CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 63/086,610, filed Oct. 2, 2020, the substance of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to disposable absorbent articles having improved performance characteristics.

BACKGROUND

Disposable absorbent articles are widely used by a variety of consumers. In general, disposable absorbent articles comprise a topsheet, a backsheet, and an absorbent core disposed between the topsheet and the backsheet. Users of such disposable absorbent articles have several desired qualities in their absorbent article of choice. For example, in the context of feminine hygiene articles, users typically desire a soft and cushiony feeling article. Users typically also want good fluid acquisition such that the topsheet does not feel wet.

Additionally, users also typically desire resiliency. Namely, the article should be able to recover its shape, at least to some extent, due to forces applied to the article by the user, e.g. when the user is in motion. Unfortunately this desire is often at odds with resiliency. The amount of force required to compress an article can impact the level of softness that the article provides. The higher the force, typically the “harder” the product is perceived. Similarly, absorbent articles that are resilient can include materials which resist such compressive forces. So, resilient articles may not be perceived as “soft.” However, an absorbent article with good resiliency can help accommodate forces which are applied during use. An absorbent article with good resiliency can help the absorbent article recover its shape despite these forces. In contrast, absorbent articles with poor resiliency qualities will tend to bunch or compress during use in the face of these forces without recovery. Unfortunately, the bunching or compressing of the absorbent article can lead to some discomfort and also lead to leakage.

Moreover, some consumers may desire a product that has sufficient thickness and stiffness to provide the desirable amount of protection while also being flexible. Lofty materials may be utilized to provide a thick cushiony feeling article. However, in use these lofty materials can experience various compressive loads. Recovery from these compressive loads is paramount in maintaining the cushiony feeling of the article. Exacerbating this issue is the fact that the characteristics of the materials of the absorbent article change once fluid is introduced into the article. Hence, an article that may meet a consumer's requisite criteria before use may no longer be comfortable, flexible, or have the desired stiffness to the user after a given amount of fluid has been absorbed by the absorbent article.

Regarding quick acquisition speeds, there is typically a tradeoff between acquisition and rewet. Namely, the quicker the acquisition speed, the higher the rewet increases and vice versa. Low rewet is also desired by consumers.

As such there is a need to create an absorbent article with improved fluid acquisition, rewet, softness, and resiliency.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as the present invention, it is believed that the invention will be more fully understood from the following description taken in conjunction with the accompanying drawings. Some of the figures may have been simplified by the omission of selected elements for the purpose of more clearly showing other elements. Such omissions of elements in some figures are not necessarily indicative of the presence or absence of particular elements in any of the exemplary embodiments, except as may be explicitly delineated in the corresponding written description. None of the drawings are necessarily to scale.

FIG. 1A is a schematic representation of a disposable absorbent article constructed in accordance with the present disclosure;

FIG. 1B is a schematic representation of an absorbent system of the disposable absorbent article shown in FIG. 1A;

FIG. 2 is a schematic representation of a process which can be utilized to construct fluid management layer of the present disclosure;

FIG. 3 is a schematic representation of an elevation view of a fluid management layer constructed in accordance with the present disclosure;

FIG. 4 is a graphical plot showing results from a dynamic mechanical analysis test performed on the fluid management layer of the present disclosure;

FIGS. 5A-5D are SEM images showing cross sections of a fluid management layer which is a comparative sample;

FIGS. 6A-6D are SEM images showing cross sections of a fluid management layer of a fluid management layer constructed in accordance with the present disclosure; and

FIG. 7 is a schematic illustration showing a view of an apparatus used for the Repetitive Acquisition and Rewet test.

FIGS. 8A-8B are schematic illustrations showing views of an apparatus used for the Repetitive Acquisition and Rewet test.

FIGS. 9A-9B are schematic illustrations showing views of an apparatus used for the Repetitive Acquisition and Rewet test.

DETAILED DESCRIPTION

As used herein, the following terms shall have the meaning specified thereafter:

“Absorbent article” refers to wearable devices, which absorb and/or contain liquid, and more specifically, refers to devices, which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Absorbent articles can include diapers, training pants, adult incontinence undergarments (e.g., liners, pads and briefs) and/or feminine hygiene products.

The term “integrated” as used herein is used to describe fibers of a nonwoven material which have been intertwined, entangled, and/or pushed/pulled in a positive and/or negative Z-direction (direction of the thickness of the nonwoven material). Some exemplary processes for integrating fibers of a nonwoven web include spunlacing and needlepunching. Spunlacing uses a plurality of high pressure water jets to entangle fibers. Needlepunching involves the use of needles to push and/or pull fibers to entangle them with other fibers in the nonwoven.

The term “carded” as used herein is used to describe structural features of the fluid management layers described herein. A carded nonwoven utilizes fibers which are cut to a specific length, otherwise known as “staple length fibers.” Staple length fibers may be any suitable length. For example, staple length fibers may have a length of up to 120 mm or may have a length as short as 10 mm. However, if a particular group of fibers are staple length fibers, for example viscose fibers, then the length of each of the viscose fibers in the carded nonwoven is predominantly the same, i.e. the staple length. It is worth noting that where additional staple fiber length fiber types are included, for example, polypropylene fibers, the length of each of the polypropylene fibers in the carded nonwoven is also predominantly the same. But, the staple length of the viscose and the staple length of the polypropylene may be different.

In contrast, continuous filaments such as by spunbonding or meltblowing processes, do not create staple length fibers. Instead, these filaments are of an indeterminate length and are not cut to a specific length as noted regarding their staple fiber length counterparts.

The “longitudinal” direction is a direction running parallel to the maximum linear dimension, typically the longitudinal axis, of the article and includes directions within 45° of the longitudinal direction. “Length” of the article or component thereof, when used herein, generally refers to the size/distance of the maximum linear dimension, or typically to the size/distance of the longitudinal axis, of an article or part thereof.

The “lateral” or “transverse” direction is orthogonal to the longitudinal direction, i.e. in the same plane of the majority of the article and the longitudinal axis, and the transverse direction is parallel to the transverse axis. “Width” of the article or of a component thereof, when used herein, refers to the size/distance of the dimension orthogonal to the longitudinal direction of the article or component thereof, i.e. orthogonal to the length of the article or component thereof, and typically it refers to the distance/size of the dimension parallel of the transverse axis of the article or component.

The “Z-direction” is orthogonal to both the longitudinal and transverse directions.

“Machine Direction” or “MD” as used herein means the direction parallel to the flow of the carded staple-fiber nonwoven through the nonwoven making machine and/or absorbent article product manufacturing equipment.

“Cross Machine Direction” or “CD” as used herein means the direction parallel to the width of the carded staple-fiber nonwoven making machine and/or absorbent article product manufacturing equipment and perpendicular to the machine direction.

Disposable absorbent articles of the present disclosure comprise a wearer-facing surface and an opposing garment-facing surface. A topsheet may form at least a portion of the wearer-facing surface and a backsheet may form at least a portion of the garment-facing surface. An absorbent core is disposed between the topsheet and the backsheet, and a fluid management layer is disposed between the absorbent core and the topsheet.

The topsheet and the backsheet may be joined together to form an outer periphery of the disposable absorbent article. A periphery of the absorbent core and/or the fluid management layer may be disposed inboard of the outer periphery. For example, the absorbent core may have end edges extending generally parallel to a transverse axis and side edges extending generally parallel to a longitudinal axis. Each of the end edges and side edges may be disposed inboard of the outer periphery. Similarly, the fluid management layer may comprise end edges which extend generally parallel to the transverse axis and side edges which extend generally parallel to the longitudinal axis.

The end edges and side edges may be disposed inboard of the outer periphery. Or, the end edges may be coterminous with the outer periphery to the extent that the end edges intersect the outer periphery. In addition or independently of the end edges of the fluid management layer, the side edges of the fluid management layer may be coterminous with the outer periphery of the absorbent article.

Additionally, the end edges and/or side edges of the absorbent core and/or fluid management layer may be curvilinear in nature. For example, the side edges of the absorbent core and/or the fluid management layer may curve inward from the ends toward the transverse axis. Such construction may help with conformity of the absorbent article. Similarly, the end edges in conjunction with or independently of the side edges of the absorbent core and/or fluid management layer may comprise a curvilinear path which is either generally concave or generally convex.

The fluid management layer of the present disclosure comprises a plurality of carded, integrated fibers. The fluid management layer provides increased caliper to the absorbent article which can translate into a softer feeling article. Additionally, the fluid management layer of the present disclosure can provide increased resiliency to the absorbent article over that of currently available absorbent articles. Typically, there is a tradeoff with resiliency and softness. Softer materials may have difficulty recovering their shape from applied forces in one or more directions. And the converse may be true for resilient materials. In the absorbent article context, resilient materials typically exhibit good recovery from applied forces; however, they are typically not perceived as being very soft. It is also worth noting that many absorbent articles can exhibit good resilience properties when dry; however, upon absorption of a liquid insult, their resiliency decreases substantially. The absorbent articles of the present disclosure exhibit good resiliency properties both in dry and wet conditions.

In addition to the softness and resiliency benefits of the absorbent articles of the present disclosure, stain size control and faster fluid acquisition may be obtained. Stain size is important in the way the absorbent article is perceived. In the menstrual context, when the stain is large, users may feel like their product is near failure just from the optics of the stain in relation to the outer periphery of the absorbent article. In contrast, smaller stains can provide users with assurance that the absorbent article will not fail as the stain is more inboard of the outer periphery than its large stain counterpart.

Regarding fluid acquisition speed, this attribute is key in making the user feel dry and clean. When the absorbent article takes a long time to drain liquid insults from the topsheet, users can feel wet. Additionally, when fluid stays on the topsheet for an extended period of time, users can feel like their skin in the intimate area is unclean.

As noted previously, the fluid management layer is an integrated, carded, nonwoven material. The fluid management layer of the present disclosure may comprise one or more carded webs which are subsequently fiber integrated with one another. Where only one carded web is utilized, the fibers of the carded web are integrated.

A wide variety of configurations for a fluid management layer may be achieved. However, it is important that the fluid management layer of the present disclosure have adequate openness to allow for quick acquisition of fluid. With this in mind, the carded webs which make up the fluid management layer may be different from one another. For example, one of the carded webs may comprise a different fiber blend than the others. Specifically, assuming the first carded web would be closest to the wearer-facing surface in an absorbent article, the fiber selection for a first carded web may be such that there is more openness associated with this web. A second carded web may be similarly configured. In contrast, a third carded web may be configured to collect liquid insults from the void space of the first and second carded webs and effectively distribute these liquid insults to an absorbent core. Where a fiber makeup of one of the carded webs is different than a fiber makeup of another carded web, where the carded webs are integrated, is a heterogenous configuration. Alternatively, where the carded webs being integrated all have the same fiber makeup is termed a homogeneous configuration.

Once the carded web(s) are integrated, they cannot be manually separated—at least not without substantial effort and time. Each carded nonwoven web forms a stratum in the overall fluid management layer. Each stratum can maintain its unique properties for at least a portion of the stratum along the z-direction, even when integrated into a larger fluid management layer. The fluid management layer can provide capillary suction to “pull” fluid through the topsheet, which is competing for trickle/low flow conditions. The fluid management layer also can contain a gush by providing distribution functions to efficiently utilize the absorbent core, as well as provide intermediate storage until the absorbent core can accept fluid.

As noted previously, absorbent articles which exhibit a soft cushiony feel, good resiliency and fluid handling characteristics is in accordance with the present disclosure. The caliper of the fluid management layer therein is important. Notably, typical calipers of webs from conventional spunlace lines achieve a caliper factor (caliper per 10 gsm of basis weight) of 0.03 to 0.12. In contrast, the fluid management layers of the present disclosure can exhibit a caliper factor of at least 0.13 mm, at least about 0.15 mm, or about 0.2 mm, including any values within these ranges and any ranges created thereby. The fluid management layer of the present disclosure can have a caliper factor of between 0.13 mm to about 0.3 mm, or from about 0.14 mm to about 0.25 mm, or from about 0.15 mm to about 0.22 mm, including all values within these ranges and any ranges created thereby. Caliper data is provided hereafter for an Inventive sample 1 as well as a Comparative sample 1. The caliper and caliper factor of the fluid management layers of the present disclosure may be determined by the Caliper and Caliper Factor test methods disclosed herein. It is important to note that the caliper factors mentioned heretofore are with regard to caliper obtained using 0.5 kPa of applied pressure as noted in the Caliper method disclosed herein.

The inventors have surprisingly discovered that in order to achieve the increase in caliper factor, a simpler process path may be utilized to produce the spunlace web. Generally, the web path through a hydroentangling line is tortuous and subjects the web to both compressive and tensile stresses. This tortuous web path requires water jet pressures high enough to entangle the fibers, creating tensile strength sufficient to survive subsequent web handling. These water jets are applied to both surfaces of the web. This additional water pressure required to create sufficient entanglement for tensile strength is generally in excess of the pressure needed to create the desired fluid handling pore structure and meaningfully reduces caliper of the resultant web. Additionally, the web is subject to significant radial compression and tensile stress as the web is wound around a variety of vacuum drums and rolls such that additional water jets can further entangle the constituent fibers of the strata. Moreover, these webs may be subsequently wound around dryer drums subjecting them to additional compressive force. However, the inventors have found that winding of the web around these rolls causes compression on the web and actually reduces the caliper of the web.

In contrast, the inventors have discovered that through the use of a simplified web path that reduces radial compressive stresses/excessive tensile forces and the appropriate selection of fibers in the fluid management layer, caliper of the fluid management layers of the present disclosure can be maintained. For example, the use of rolls and the number of water jets utilized can be reduced via the simplified path. As such, while the level of entanglement is not to the extent provided by the conventional process, sufficient tensile strength in the web can be provided by selecting the appropriate combination of fibers as disclosed herein, e.g. stiffening fibers which can be heat treated. Again, the simplified path and appropriate fiber selection as described herein, allows the fluid management layers of the present disclosure to achieve caliper factors that have heretofore not been achievable.

Additionally, the caliper factors of the fluid management layers of the present disclosure mentioned above were derived from caliper data from material which was rolled for storage/shipping. Caliper measures pre-winding could be taken which would yield much higher caliper factors. However, such caliper measurements may not necessarily reflect the fluid management layer that makes it into an article.

The fluid management layer of the present disclosure can have a basis weight of up to 75 grams per square meter (gsm); or a basis weight of up to 70 gsm; or a basis weight in the range of between about 30 gsm to about 75 gsm, from about 45 gsm to about 70 gsm, and between about 50 gsm to about 65 gsm, including any values within these ranges and any ranges created thereby.

Some absorbent articles may not require as much basis weight as recited above. For example, liners which generally do not have the same level of absorbent capacity as menstrual pads may be able to have a reduced basis weight over that which was recited above. For example, the fluid management layer may have a basis weight of between 20 gsm to 70 gsm or between 35 gsm to about 65 gsm, or from about 40 gsm to about 60 gsm, specifically including all values within these ranges and any ranges created thereby. In one specific example, the fluid management layer of the present disclosure can have a basis weight of between about 45 gsm to about 55 gsm. The basis weights of the fluid management layers of the present disclosure may be determined by the Basis Weight method disclosed herein.

The inventors have also found that the processing technique for creating caliper in the fluid management layer can be utilized not only on spunlace materials where the strata are heterogeneous but also where the strata are homogeneous, e.g. each stratum has the same fiber makeup. Additionally, the inventors have surprisingly found that spunlace materials constructed with this process along with appropriate fiber selection can also provide good resiliency and recovery from compression, with improved fluid handling performance above those spunlace materials that are produced via typical spunlace processes.

It is also worth noting that due to the fiber integration, the fluid management layer does not require adhesives or latex binders for stability. Additionally, the carded nonwoven of the fluid management layers of the present disclosure can be manufactured from an assortment of suitable fiber types that produce the desired performance characteristics. For example, the fluid management layer may comprise a combination of stiffening fibers, absorbent fibers and resilient fibers.

As will be discussed in additional detail hereafter, the types of fibers in the fluid management layer of the present disclosure are described in terms of their functionality within the fluid management layer. For example, absorbent fibers are utilized to absorb liquid insults. Stiffening fibers are utilized to bond together via heat treatment thereby providing stiffness and resiliency to the fluid management layer. Resilient fibers are utilized to provide recovery from compressive forces which act against the fluid management layer.

In order to enhance the stabilizing effect of the integration, crimped, carded fibers may be utilized. One or more of the absorbent fibers, stiffening fibers, and resilient fibers may be crimped prior to integration. For example, where synthetic fibers are utilized, these fibers may be mechanically crimped via intermeshing teeth. As for the absorbent fibers, these fibers may be mechanically crimped and/or may have a chemically induced crimp due to the variable skin thickness formed during creation of the absorbent fibers.

As noted previously, the amount of absorbent fibers can impact the absorption of liquid insults to the wearer-facing surface or topsheet. However, when absorbent fibers absorb liquid, they tend to lose some of their structural integrity. The loss of structural integrity can reduce the resiliency of the absorbent article and lead to increased bunching and increased leakage. Accordingly, while in principle, a large percentage of absorbent fibers is good for draining liquid insults from the wearer-facing surface and/or topsheet rapidly, a large percentage can also lead to other problems with the absorbent article as mentioned heretofore.

In light of the potential problems associated with having too much of a weight percentage of absorbent fibers, the inventors have found that the fluid management layer of the present disclosure may comprise from about 10 percent to about 60 percent by weight, from about from about 15 percent to about 50 percent by weight, from about 20 percent to about 40 percent by weight, specifically including any values within these ranges and any ranges created thereby of absorbent fibers. In one specific example, the fluid management layer may comprise from about 20 percent to about 30 percent by weight of absorbent fibers. The weight percentages of the absorbent fibers, resilient fibers, and/or stiffening fibers may be determined via the Material Compositional Analysis method disclosed herein.

Additionally, due to the loss of integrity of the absorbent fibers when wet, the fluid management layer also can comprise sufficient weight percentage of resilient fibers which impact the recovery of the absorbent article from compressive loads experienced during use. The inventors have found that the fluid management layer of the present disclosure may comprise from about 15 percent to about 70 percent, from about 20 percent to about 60 percent, or from about 25 percent to about 50 percent by weight of resilient fibers, specifically reciting all values within these ranges and any ranges created thereby. In one specific example, the fluid management layer may comprise from about 30 percent by weight to about 40 percent by weight resilient fibers.

Moreover, stiffening fibers may be utilized to help the fluid management layer of the present disclosure provide resiliency to the absorbent article. For example, as discussed hereafter, stiffening fibers may be bonded to one another via heat treatment of the fluid management layer during production. This bonding of the stiffening fibers creates a support matrix which helps with resiliency and stiffness of the fluid management layer. With this in mind, the fluid management layer may comprise from about 25 percent to about 70 percent, from about 30 percent to about 60 percent, or from about 40 percent to about 55 percent of stiffening fiber, specifically reciting all values within these ranges and any ranges created thereby. In one specific example, the fluid management layer may comprise from about 40 percent by weight to about 50 percent by weight of stiffening fibers.

As mentioned previously, the fluid management layers of the present disclosure can provide their respective absorbent articles with a soft cushiony feel with good resiliency. Where caliper, resiliency, and a soft cushiony feel are the objective, the weight percentage of stiffening fibers may be greater than or equal to the weight percentage of resilient fibers. The weight percentage of absorbent fibers can be less than the weight percentage of resilient fibers and/or stiffening fibers. In general, a higher weight percentage of absorbent fibers is considered to be beneficial in rapidly absorbent fluid insults; however, given the proximity of the absorbing fibers to the topsheet, it is beneficial for the absorbent core to dewater the absorbing fibers. Where there is a larger percentage of absorbing fibers, typically a larger core is required to dewater the absorbent fibers. This typically leads to higher costs. With this in mind, a ratio of absorbent fibers in the fluid management layers of the present disclosure to stiffening fibers by weight percentage can be from about 1:7 to about 2:1, from about 1:4 to about 1.5:1, from about 1:2 to about 1:1, specifically reciting all values within these ranges and any ranges created thereby Similarly a ratio of absorbent fibers to resilient fibers by weight percentage can be from about 1:7 to about 3:1, from about 1:2 to about 2:1, or from about 1:1.5 to about 1:1, specifically reciting all values within these ranges and any ranges created thereby.

Regardless of whether the fluid management layer is utilized in an adult incontinence article menstrual article, liner, or other hygiene article, of importance is the ability of the fluid management layer to acquire liquid insults from the topsheet and to pull the liquid far enough from the topsheet, such that the topsheet does not feel wet. To accomplish this, the inventors have found that the increased caliper of the fluid management layer discussed herein can facilitate fluid acquisition due to the increased void volume of the fluid management layer. The higher caliper at the lower basis weight equals more void volume with higher permeability. Additionally, the increased caliper of the fluid management layer can also provide a stain masking benefit. Namely, the stains that are visible through the topsheet with absorbent articles using the fluid management layer of the present disclosure, appear much smaller than their conventional fluid management layer counterparts.

It is worth noting that for a set basis weight of a fiber, larger diameter fibers can provide more void volume between adjacent fibers as compared to their smaller diameter counterparts. As such, the fiber size of the fibers in the fluid management layer can be important. For example, for a set percentage weight of fiber, as fiber size goes up there are fewer fibers per gram, and fewer fibers can equal more space between the fibers. Ideally, particularly in the context of menstrual fluid, the fluid management layer can have void volume as well as some degree of capillarity to drain the topsheet.

With the above in mind, the inventors have also surprisingly discovered that careful selection of the fiber types in each of the strata in the fluid management layer and the linear densities of the fiber types can achieve the desired outcome of quick acquisition and low rewet. The fiber types of the individual strata are discussed in additional detail hereafter. It is worth noting that the discussion below regarding fiber types in the strata of the fluid management layer assumes that the first carded nonwoven web is nearer to the topsheet than the web(s) of the additional card(s).

Some suitable linear density values of absorbent fibers for use in the fluid management layers of the present disclosure are provided. For example, the absorbent fiber linear density may range from about 1 dtex to about 7 dtex, from about 1.4 dtex to about 6 dtex, or from about 1.7 dtex to about 5 dtex, specifically reciting all values within these ranges and any ranges created thereby. In one specific example, the absorbent fiber may comprise a linear density of about 1.7 dtex. The dtex of the absorbent fibers, stiffening fibers, and resilient fibers may be determined via the Fiber Decitex method disclosed herein.

The absorbent fibers of the fluid management layer may have any suitable shape. Some examples include trilobal, “H,” “Y,” “X,” “T,” round, or flat ribbon. Further, the absorbing fibers can be solid, hollow or multi-hollow. Other examples of suitable multi-lobed, absorbent fibers for utilization in the fluid management layers detailed herein are disclosed in U.S. Pat. No. 6,333,108 to Wilkes et al, U.S. Pat. No. 5,634,914 to Wilkes et al., and U.S. Pat. No. 5,458,835 to Wilkes et al. The trilobal shape can improve wicking and improve masking. Suitable trilobal rayon is available from Kelheim Fibres and sold under the trade name Galaxy. While each stratum may comprise a different shape of absorbing fiber, much like mentioned above, not all carding equipment may be suited to handle such variation between/among strata. In one specific example, the fluid management layer comprises round absorbent fibers.

Any suitable absorbent material for the absorbent fibers may be utilized. Some examples of absorbent materials include cotton, pulp, rayon or regenerated cellulose or combinations thereof. In one example, the fluid management layer 30 may comprise viscose cellulose fibers. The length of the absorbent fibers can be in the range of about 20 mm to about 100 mm, or about 30 mm to about 50 mm or about 35 mm to about 45 mm, specifically reciting all values within these ranges and any ranges created thereby. In general, the fiber length of pulp is from about 4 to 6 mm and cannot used in conventional carding machines because the pulp fibers are too short. So, if pulp is desired as a fiber in the fluid management layer, then additional processing to add pulp to the carded webs may be required. As an example, pulp may be airlaid between carded webs with the combination being subsequently integrated. As another example, tissue may be utilized in combination with the carded webs and the combination may be subsequently integrated.

As noted previously, in addition to absorbent fibers, the fluid management layer of the present disclosure may comprise stiffening fibers. Stiffening fibers may be utilized to help provide structural integrity to the fluid management layer. The stiffening fibers can help increase structural integrity of the fluid management layer in a machine direction and/or in a cross-machine direction which can facilitate web manipulation during processing of the fluid management layer for incorporation into a disposable absorbent article.

Some suitable linear density values of stiffening fiber are provided. For example, the stiffening fiber linear density may range from about 1.0 dtex to about 6 dtex, from about 1.5 dtex to about 5 dtex, or from about 2.0 dtex to about 4 dtex, specifically reciting all values within these ranges and any ranges created thereby. In another specific example, the dtex of the stiffening fibers is about 2.2 dtex.

Some examples of suitable stiffening fibers include bi-component fibers comprising polyethylene and polyethylene terephthalate components or polyethylene terephthalate and co-polyethylene terephthalate components. The components of the bi-component fiber may be arranged in a core sheath arrangement, a side by side arrangement, an eccentric core sheath arrangement, a trilobal arrangement, or the like. In one specific example, the stiffening fibers may comprise bi-component fibers having polyethylene/polyethylene terephthalate components arranged in a concentric, core—sheath arrangement where the polyethylene is the sheath.

While other materials may be useful, the inventors have found that the stiffness of polyethylene terephthalate is useful in creating a resilient structure. In contrast, the polyethylene component of the stiffening fibers can be utilized to bond to one another during heat treatment. This can help provide tensile strength to the web in both the MD and CD. Additionally, the bonding of the polyethylene component to other polyethylene components of stiffening fibers can create fixed points in the nonwoven. These fixed points can reduce the amount of fiber-to-fiber sliding which can increase the resiliency of the material.

One of the benefits of the stiffening fibers is that the integrated nonwoven may be heat treated post fiber entanglement. The heat treatment can provide additional structural integrity to the integrated nonwoven by forming bonds between adjacent stiffening fibers. So, where there is a higher percentage of stiffening fibers, more connection points may be created. Too many connection points can yield a much stiffer fluid management layer which may negatively impact comfort/softness. As such, the weight percentage of the stiffening fibers is of critical importance when designing an absorbent article.

Regarding the heat stiffening process, any suitable temperature may be utilized. And, the suitable temperature may be impacted, in part, by the constituent chemistry of the stiffening fibers as well as by the processing fluid management layer web. For example, the fluid management layer web may be heat stiffened at a temperature of about 132 degrees Celsius. However, it is also worth noting, that in order to provide a uniform stiffness property across the fluid management layer, any heating operation should be set up to provide uniform heating to the fluid management layer web. Even small variations in temperature can greatly impact the tensile strength of the fluid management layer.

As noted previously, the fluid management layer of the present disclosure comprises resilient fibers. The resilient fibers can help the fluid management layer maintain its permeability and compression recovery. Any suitable size fiber may be utilized. For example, the resilient fibers can have a linear density of about 4 dtex to about 15 dtex, from about 5 dtex to about 12 dtex, or from about 6 dtex to about 10 dtex, specifically reciting all values within these ranges and any ranges created thereby. In one specific example, the fluid management layer may comprise resilient fibers having variable cross sections, e.g. round and hollow spiral, and/or may comprise resilient fibers having variable dtex's. In yet another specific example, the resilient fibers of the present disclosure may comprise a dtex of about 10. In such forms, the resilient fibers may be hollow spiral.

The resilient fibers can be any suitable thermoplastic fiber, such as polypropylene (PP), polyethylene terephthalate, or other suitable thermoplastic fibers known in the art. The length of the resilient fibers can be in the range of about 20 mm to about 100 mm, or about 30 mm to about 50 mm or about 35 mm to about 45 mm. The thermoplastic fibers can have any suitable structure or shape. For example, the thermoplastic fibers can be round or have other shapes, such as spiral, scalloped oval, trilobal, scalloped ribbon, and so forth. Further, the PP fibers can be solid, hollow or multi-hollow. The resilient fibers may be solid and round in shape. Other suitable examples of resilient fibers include polyester/co-extruded polyester fibers. Additionally, other suitable examples of resilient fibers include bi-component fibers such as polyethylene/polypropylene, polyethylene/polyethylene terephthalate, polypropylene/polyethylene terephthalate. These bi-component fibers may be configured as a sheath and a core. The bi-component fibers may provide a cost-effective way to increase basis weight of the material while additionally enabling optimization of the pore size distribution.

The resilient fibers can be polyethylene terephthalate (PET) fibers, or other suitable non-cellulosic fibers known in the art. The PET fibers can have any suitable structure or shape. For example, the PET fibers can be round or have other shapes, such as spiral, scalloped oval, trilobal, scalloped ribbon, hollow spiral, and so forth. Further, the PET fibers can be solid, hollow or multi-hollow. In one particular example, fibers may be fibers made of hollow/spiral PET. Optionally, the resilient fibers may be spiral-crimped or flat-crimped. The resilient fibers may have a crimp value of between about 4 and about 12 crimps per inch (cpi), or between about 4 and about 8 cpi, or between about 5 and about 7 cpi, or between about 9 and about 10 cpi. Particular non-limiting examples of resilient fibers can be obtained from Wellman, Inc. Ireland under the trade names H1311 and T5974. Other examples of suitable resilient fibers for utilization in the carded staple-fiber nonwovens detailed herein are disclosed in U.S. Pat. No. 7,767,598 to Schneider et al.

It is worth noting that the stiffening fibers and resilient fibers should be carefully selected. For example, while the constituent chemistries of the stiffening fibers and the resilient fibers may be similar, resilient fibers should be selected such that their constituent material's melting temperature is higher than that of the stiffening fibers. Otherwise, during heat treatment, resilient fibers could bond to stiffening fibers and vice versa and could create an overly rigid structure.

Without wishing to be bound by theory, it is believed that for weight percentage of absorbent fibers above about 30 percent, within the gsm ranges disclosed herein, the resilient fibers and/or stiffening fibers should be carefully selected. Where a soft, cushiony fluid management layer with a caliper factor of at least 0.13 or greater as described herein, the resilient and/or stiffening fibers can be selected to counteract the loss of structural integrity of the absorbent fibers when wet. For example, a higher dtex of resilient fiber may be beneficial in counteracting the loss of integrity experienced by the absorbent fibers. In such instances, resilient fibers may be utilized having a dtex of between about 5 dtex to about 15 dtex, from about 6 dtex to about 12 dtex, or from about 7 dtex to about 10 dtex.

In addition to or an alternative thereof, the stiffening fibers may be configured to provide greater structural integrity. For example, the stiffening fibers may comprise bi-component fibers in a core-sheath configuration where the sheath is co-polyethylene terephthalate. However, with such a material change, additional problems may occur. For example, the joining of materials to the fluid management layer may then only be via adhesive as opposed to fusion bonding.

Still another example which is in addition to or independent of the foregoing is an increase in bonding of the stiffening fibers. Where the absorbent fibers comprise more than 30 percent by weight of the fluid management layer, the heat at which the stiffening fibers are bonded may be increased and/or the time of exposure may be increased. This can increase the number of bonds in the stiffening fiber matrix which can counteract the loss of integrity of the absorbent fibers when wet. However, with the increase in the number of bonds comes an increase in stiffness. The increase in stiffness can decrease the perception of softness by the user. In a similar regard, in addition to or alternatively thereto, the linear density of the stiffening fibers may be increased to combat the loss of integrity of the absorbent fibers, where the absorbent fibers make up 30 percent by weight or more. In such instances, the linear density of the stiffening fibers may be from about 3 dtex to about 6 dtex, from about 4 dtex to about 6 dtex.

It is worth noting that while it may appear that the solution to wet collapse is simply to use larger dtex fibers, their use must be balanced. Particularly for viscous fluids, the fluid management layers of the present disclosure can have some degree of capillarity to help drain liquid insults to the wearer-facing surface of the article. Unfortunately, while the use of large dtex fibers can provide caliper benefits, it also detracts from capillarity which can lead to fluid handling issues.

The fluid management layer of the present disclosure may be incorporated into a variety of absorbent articles. An exemplary schematic showing an absorbent article, i.e. a feminine hygiene pad, of the present disclosure is shown in FIG. 1A. As shown, absorbent articles 10 in accordance with the present disclosure comprise a topsheet 20, a backsheet 50, and an absorbent core 40 disposed between the topsheet 20 and the backsheet 50. A fluid management layer 30 is disposed between the topsheet 20 and the absorbent core 40. The absorbent article has a wearer-facing surface 60 and an opposing garment-facing surface 62. The wearer-facing surface 60 primarily comprises the topsheet 20 while the garment-facing surface 62 primarily comprises the backsheet 50. Additional components may be included in either the wearer-facing surface 60 and/or the garment-facing surface 62. For example, where the absorbent article is an incontinent pad, a pair of barrier cuffs which extend generally parallel to a longitudinal axis L of the absorbent article 10, may also form a portion of the wearer-facing surface 60. Similarly, a fastening adhesive may be present on the backsheet 50 and form a portion of the garment-facing surface 62 of the absorbent article.

An exemplary configuration for the fluid management layer of the present disclosure is shown in FIG. 1B. As shown, the fluid management layer 30 comprises opposing end edges 32A and 32B which may extend generally parallel to a transverse axis T. And, the fluid management layer 30 comprises side edges 31A and 32B which may extend generally parallel to the longitudinal axis L. Similarly, the absorbent core 40 comprises opposing end edges 42A and 42B which may extend generally parallel to the transverse axis T. And, the absorbent core 40 may comprise side edges 41A and 41B which extend generally parallel to the longitudinal axis L.

As shown, each of the end edges 32A and 32B of the fluid management layer 30 may be disposed longitudinally outboard of the absorbent core 40. However, this is not necessarily required. For example, the end edges 32A and/or 32B may be coextensive with the absorbent core 40 or the end edges 32A and/or 32B may be disposed longitudinally inboard of the end edges 42A and/or 42B of the absorbent core 40.

Similarly, the side edges 31A and/or 31B may be disposed transversely outboard of the side edges 41A and/or 41B of the absorbent core 40. Or, the side edges 31A and/or 31B may be coextensive with the side edges 41A and/or 41B of the absorbent core 40.

An exemplary process for forming the fluid management layer of the present disclosure is shown in FIG. 2. As shown, a plurality of carding machines 210, 220, and 230 may each create a carded nonwoven web, e.g. 214, 224, and 234, respectively, which is transferred to a carrier belt 240. Each of the carded nonwoven webs 214, 224, and 234, may be provided to the carrier belt 240 via a web chute 212, 222, 232, respectively. It is also worth noting that after the carded nonwoven 214 is deposited on the carrier belt 240, the carded nonwoven 224 is then deposited on the first carded nonwoven 214 on the carrier belt 240. Similarly, the third carded nonwoven web 234 deposited on the second carded nonwoven 224 and the first carded nonwoven 214 on the carrier belt 240. Subsequently, each of the first, second, and third carded nonwoven webs 214, 224, and 234 are then provided to an integration process 250 which utilizes either needles and/or high-pressure water streams to entangle the fibers of the first, second, and third carded nonwoven webs. Both carding and integration processes are well known in the art.

Additional carding machines may be utilized. Additionally, the fluid management layer of the present disclosure may be produced utilizing only two out of the three cards. In such instances, the first carded web 214 would be deposited on the carrier belt 240. And, subsequently, the second carded web 224 would be deposited on the first carded web 214. Then, the first carded web 214 and the second carded web 224 would be integrated as described herein.

It is worth noting that with the arrangement provided in schematic diagram of FIG. 2, a wide variety of configurations for a fluid management layer may be achieved. However, it is important that the fluid management layer of the present disclosure have adequate openness to allow for quick acquisition of fluid yet also are able to lock away liquid insults to reduce the likelihood of rewet. With this in mind, the carded webs, i.e. 214, 224, and/or 234, may be different from one another.

For example, one of the carded webs may comprise a different fiber blend than the others. Specifically, assuming the first carded web would be closest to the wearer-facing surface in an absorbent article, the fiber selection for the first carded web 214 may be such that there is more openness associated with this web. The second carded web 224 may be similarly configured. In contrast, the third carded web 234 may be configured collect liquid insults from the void space of the first and second carded webs 214 and 224 and effectively distribute these liquid insults to an absorbent core. Alternatively, the first carded web 214, the second carded web 224 and the third carded web 234 may be configured the same.

A schematic representation of an exemplary fluid management layer in accordance with the present disclosure is provided in FIG. 3. As shown, the fluid management layer 30 comprises the first surface 300A and the opposing second surface 300B. Between the first surface 300A and the second surface 300B, the fluid distribution layer 30 comprises two or more strata along the Z-direction.

Disposable absorbent articles comprising the fluid management layer were constructed and tested. Additionally, a plurality of disposable absorbent articles was constructed and tested. The difference between the inventive samples and the comparative samples was solely the fluid management layer. Each of the below described inventive samples comprised a fluid management layer of the present disclosure while the comparative sample absorbent articles comprised a fluid management layer which is currently available on the market.

For each of the inventive sample 1 and comparative sample 1, the following components were utilized.

Topsheet—The topsheet for each of the Inventive sample 1 and Comparative sample 1 was a hydroformed film with microapertures and macroapertures. The film is currently available from Tredegar Corp. USA.

Absorbent Core—The absorbent core was an airlaid absorbent core comprising pulp fibers, absorbent gelling material, and bico fibers, having a basis weight of 182 gsm available from Glatfelter, York, Pa., USA.

For each of the Inventive sample 1 and Comparative sample 1, the following was their fluid management layer's constituent material makeup. All of the fluid management layers were hydroentangled, spunlaced.

Comparative sample 1 fluid management layer—basis weight of 50 gsm, having 40 percent by weight viscose cellulose fibers having a 1.7 dtex; 20 percent by weight polyethylene terephthalate having a 4.4 dtex; and 40 percent by weight bi-component fibers having a first component of polypropylene and a second component of polyethylene having a 1.7 dtex. The fluid management layer of Comparative sample 1 was created via conventional hydroentanglement processes Inventive sample 1 fluid management layer—basis weight of 55 gsm having 20 percent by weight viscose cellulose fibers having a 1.7 dtex; 30 percent by weight hollow spiral polyethylene terephthalate fibers having a 10 dtex; and 50 percent by weight bi-component fibers having a first component polyethylene terephthalate and polyethylene in a core-sheath configuration where the polyethylene is the sheath. The fluid management layer of Inventive sample 1 was made in accordance with the fluid management layers of the present disclosure.

For each of the inventive sample 2 and comparative sample 2, the following components were utilized.

Topsheet—The topsheet for each of the Inventive sample 2 and Comparative sample 2 was a nonwoven topsheet having a basis weight of 24 gsm and being an air-through bonded, nonwoven. The air-through bonded nonwoven comprised bi-component fibers, where polyethylene terephthalate and polyethylene were in a core-sheath configuration with polyethylene as the sheath. The fibers comprise a 2.2 dtex. The topsheet comprised 60% hydrophilic fibers and 40% hydrophobic fibers by weight of the fibers.

Absorbent Core—The absorbent core was an airlaid absorbent core comprising pulp fibers, absorbent gelling material, and bico fibers, having a basis weight of 182 gsm available from Glatfelter, York, Pa., USA.

For each of the inventive sample 2 and comparative sample 2, the following was their fluid management layer's constituent material makeup.

Comparative sample 2 fluid management layer—basis weight of 65 gsm, having 33 percent by weight viscose cellulose fibers having a 1.3 dtex; 17 percent by weight polyethylene terephthalate having a 4.4 dtex; and 50 percent by weight bi-component fibers having a first component of polypropylene and a second component of polyethylene having a 1.7 dtex. The fluid management layer of Comparative sample 2 was created via conventional hydroentanglement processes

Inventive sample 2 fluid management layer—basis weight of 65 gsm having 20 percent by weight viscose cellulose fibers having a 1.3 dtex; 30 percent by weight hollow spiral polyethylene terephthalate fibers having a 10 dtex; and 50 percent by weight bi-component fibers having a first component polyethylene terephthalate and polyethylene in a core-sheath configuration where the polyethylene is the sheath having a 2.2 dtex. The fluid management layer of Inventive sample 2 was made in accordance with the fluid management layers of the present disclosure.

Table 1 shows caliper of the fluid management layers of the Inventive sample 1 versus the Comparative sample 1. Note that the calipers were taken at 0.5 kPa. Each of the fluid management layers was removed from a finished product.

TABLE 1

Sample
Caliper (mm)

Comparative sample 1
0.47

Inventive sample 1
0.85

As shown, the fluid management layer of the present disclosure is 80 percent thicker than its comparative counterpart with only a 10 percent difference in basis weight. And, as shown the caliper factor for the Inventive sample 1 is much higher than that of the Comparative sample 1 as shown in Table 2.

TABLE 2

Sample
Caliper Factor (mm/10 gsm)

Comparative sample 1
0.09

Inventive sample 1
0.15

Table 3 shows the acquisition speed of the fluid management layers of the Inventive sample 1 versus the Comparative sample 1.

TABLE 3

Sample
Acquisition Speed (sec)

Comparative sample 1
11.16

Inventive sample 1
7.76

As shown, the fluid management layer of the Inventive sample 1 is 30 percent faster in acquiring liquid insults than the fluid management layer of the Comparative sample 1. The fluid management layers of the present disclosure can exhibit an acquisition speed of less than about 10 seconds, less than about 8 seconds, or less than about 7 seconds when measured in accordance with the Liquid Strikethrough Time test method described herein. For example, the fluid management layers of the present disclosure can exhibit acquisition times in the range of from between about 5 seconds to about 10 seconds, from about 5 seconds to about 9 seconds, or from about 5 seconds to about 8 seconds, specifically reciting all values within these ranges and any ranges created thereby, when measured in accordance with the Liquid Strikethrough Time test method described herein.

Regarding the soft, cushiony nature of the fluid management layer of the present disclosure, we now refer to FIG. 4. The fluid management layer of the present disclosure is illustrated graphically by the lines associated in group 410 while the Comparative sample 1 of the fluid management layer is illustrated graphically by the lines associated in group 420. As shown, the fluid management layer of the present disclosure (Inventive sample 1) shows a higher caliper during and after compression versus the Comparative sample 1. Even after repeated cycles of compression and relaxation, the fluid management layer of the Inventive sample 1 continues to provide a higher caliper. This translates into the fluid management layer of the Inventive sample 1 being softer and more cushiony than the Comparative sample 1. Data for the graph depicted in FIG. 4 as well as the data in Tables 4A-4C was obtained via the Dynamic Mechanical Analysis method disclosed herein. The data provided in Tables 4A-4C are for the fluid management layers of the Inventive sample 1 and Comparative sample 1 and were constructed as noted previously.

TABLE 4A

Avg.
Avg.

Inventive
Comparative

sample 1
sample 1

Compression Step
Caliper (mm)
Caliper (mm)

Step 1- Caliper (mm) at 0.2 kPa
1.61
0.80

Step 2- Caliper (mm) at 8 kPa
0.59
0.32

Step 3 (Caliper (mm) at 0.2 kPa)
1.10
0.54

Step 4 (8 kPa)
0.58
0.32

Step 5 (Caliper (mm) at 0.2 kPa)
1.08
0.52

Step 6 (8 kPa)
0.58
0.32

Step 7 (Caliper (mm) at 0.2 kPa)
1.06
0.51

Step 8 (8 kPa)
0.58
0.32

Step 9 (Caliper (mm) at 0.2 kPa)
1.06
0.50

Step 10 (8 kPa)
0.57
0.31

The data in Table 4A shows that the average caliper of the Inventive sample 1 is greater than that of the Comparative sample 1 at every step whether at 0.2 kPa or at 8 kPa. In fact, the data also shows that the average caliper of the Inventive sample 1 when under compression of 8 kPa is greater than the caliper of the fluid management layer of the Comparative sample 1 when under a pressure of only 0.2 kPa—except at Step 1.

It is worth noting that the calipers expressed in Table 1 versus those in Table 4A were obtained for different pressures, i.e. 0.5 kPa versus 0.2 kPa. As such, the calipers shown are much higher than those listed in Table 1. However, it is also worth noting that from an initial wear standpoint, i.e. at Step 1, the user has a much more cushier absorbent article given the 2× higher caliper of the fluid management layer of the present disclosure, and it is believed that the user can feel the cushiness as shown by the compression in step 2. It is believed that the remainder of the steps, i.e. 3-10, can reflect more of the behavior of the fluid management layer in use—namely the resiliency of the fluid management layers of the present disclosure.

So, for the fluid management layers in accordance with the present disclosure, the caliper at step 1 (measured in accordance with the Dynamic Mechanical Analysis method disclosed herein) can be greater than about 0.9 mm, greater than about 1.2 mm, or greater than about 1.5 mm. For example, the caliper of the fluid management layer in accordance with the present disclosure can have a caliper (measured in accordance with the Dynamic Mechanical Analysis method disclosed herein) of from between about 1.0 mm to about 2.4 mm, from about 1.1 mm to about 2.2 mm, or from about 1.3 mm to about 2.0 mm, specifically reciting all values within these ranges and any ranges created thereby. In order to achieve the 2.4 mm caliper, the basis weight may be between about 60 gsm to about 75 gsm.

For the wearing experience, e.g. steps 2-10, the caliper of the fluid management layer constructed in accordance with the present disclosure can have a caliper (as measured by the Dynamic Mechanical Analysis method disclosed herein) that is greater than about 0.45 mm at 8 kPa and greater than about 0.65 mm at 0.2 kPa, or greater than about 0.5 mm at 8 kPa and greater than about 0.7 mm at 0.2 kPa, or greater than about 0.60 at 8 kPa and greater than about 0.8 mm at 0.2 kPa. For example, fluid management layers in accordance with the preset disclosure can have a caliper (as measured by the Dynamic Mechanical Analysis method disclosed herein) of from between about 0.45 mm to about 0.9 mm at 8 kPa, from between about 0.50 mm to about 0.8 mm at 8 kPa, or from about 0.55 mm to about 0.75 mm at 8 kPa, specifically reciting all values within these ranges and any ranges created thereby. Additionally or independently thereof, the fluid management layers of the present disclosure can have a caliper (as measured by the Dynamic Mechanical Analysis method disclosed herein) of from between about 0.65 mm to about 1.50 mm at 0.2 kPa, from about 0.75 mm to about 1.40 mm at 0.2 kPa, or from about 0.8 mm to about 1.20 mm at 0.2 kPa, specifically reciting all values within these ranges and any ranges created thereby.

In Table 4B, the compression distance which is the amount of decrease in caliper between the initial state, e.g. steps 1, 3, 5, 7, and 9, minus the compressed state, i.e. steps 2, 4, 6, 8, and 10.

TABLE 4B

Avg.
Avg.

Inventive
Comparative

Compression Distance (mm)
sample 1
sample 1

Step 1 minus Step 2 (mm)
1.02
0.48

Step 3 minus Step 4 (mm)
0.52
0.22

Step 5 minus Step 6 (mm)
0.50
0.20

Step 7 minus Step 8 (mm)
0.48
0.19

Step 9 minus Step 10 (mm)
0.49
0.19

Average Compression Distance (mm)
0.50
0.20

As shown in Table 4B, the fluid management layer of the Inventive sample 1 also exhibits a greater compression distance than that of the comparative sample 1. For example, fluid management layers constructed in accordance with the present disclosure may have a compression distance of greater than about 0.60 mm (as measured by the Dynamic Mechanical Analysis method disclosed herein) from Step 1 to step 2. Again, as mentioned above, it is believed that the initial caliper and compression can represent the initial feel that the user gets when using the article. Whereas step 2 onward is believed to be more of a measure for the in use experience. From step 1 to step 2, the fluid management layer of the present disclosure can exhibit a compression distance of from between about 0.60 mm to about 1.4 mm, from about 0.7 mm to about 1.4 mm, or from about 0.8 mm to about 1.4 mm, specifically reciting all values within these ranges and any ranges created thereby—as measured by the Dynamic Mechanical Analysis method disclosed herein.

For the in use steps, e.g. 3-10, fluid management layer of the present disclosure can exhibit compression distances of from between about 0.30 mm to about 1.0 mm, from about 0.40 mm to about 0.8 mm, or from about 0.45 mm to about 0.7 mm, specifically reciting all values within these ranges and any ranges created thereby—as measured by the Dynamic Mechanical Analysis method disclosed herein.

Table 4C provides additional data regarding the difference in compression distance between the Inventive sample 1 fluid management layer and the Comparative sample 1 fluid management layer as well as the percentage difference.

TABLE 4C

Delta

(Inventive −
Percent

Compression Distance (mm)
Comparative)
Difference

Step 1 minus Step 2 (mm)
0.54
212%

Step 3 minus Step 4 (mm)
0.30
237%

Step 5 minus Step 6 (mm)
0.29
244%

Step 7 minus Step 8 (mm)
0.29
249%

Step 9 minus Step 10 (mm)
0.30
256%

Average Compression Distance (mm)
0.29
246%

Referring now the FIGS. 5A through 6D, scanning electron microscope images are shown for the fluid management layer of the Comparative sample 1 (FIGS. 5A-5D) and for the fluid management layer of the Inventive sample 1, (FIGS. 6A-6D). As shown, viewing the scale indicator on both images, the Inventive sample 1 has a higher caliper than that of the Comparative sample 1. Additionally, it is noted that there are many more fibers associated with the Inventive sample 1 which extend from the first surface and are disposed, in part, superjacent to the first surface. Moreover, based on the images, many more of the fibers which are disposed, in part, superjacent to the first surface are looped. Namely, these fibers have a first fiber end which extends from the first surface and a second end which extends to the first surface. In contrast, the majority of fibers of the Comparative sample 1 which are disposed superjacent to the first surface have their respective first ends which extend from the first surface but comprise a second end which is also disposed superjacent to the first surface.

Regarding the articles of the Inventive Sample 2 versus the Comparative sample 2, several attributes of the article were measured as demonstrated below. First, the article of the Inventive sample 2 had much faster acquisition speed than that of the article of the Comparative sample 2. See

Table 5.

TABLE 5

Inventive
Comparative
Comparative

Test
Sample 2
Sample 2
Sample 1

Acquisition time 1 (sec)
19.2
45.5
14.1

Acquisition time 2 (sec)
41.9
113.4
27.5

Acquisition time 3 (sec)
69.9
183.0
37.6

Rewet (g)
0.291
0.391
0.725

As shown, the articles of the Inventive sample 2 averaged 58 percent faster speeds than the articles of the Comparative sample 2 during the first gush, averaged 63 percent faster speeds than the articles of the Comparative sample 2 during the second gush, and averaged 62 percent faster speeds than the articles of the Comparative sample 2 during the third gush. And, while acquisition speed and rewet are typically considered to be diametrically opposed interests, the Inventive sample 2 provides a 26 percent lower rewet measure compared to the article of the Comparative sample 2. Additionally, Inventive sample 2 provides for much reduced rewet over that of Comparative sample 1. Inventive sample 2 provides a reduction in rewet of 60 percent over that of Comparative sample 1. The acquisition time and rewet values for absorbent articles in accordance with the present disclosure can be determined via the Repetitive Acquisition and Rewet method disclosed herein.

Regarding the lower rewet of Inventive sample 2 versus Comparative samples 1 and 2, typically one major difference is that nonwoven topsheets tend to exhibit higher rewet values over that of film topsheets. However, both Inventive sample 2 and Comparative sample 2 exhibited lower rewet values, despite comprising the same nonwoven topsheet, over Comparative sample 1 which utilized a film topsheet. The lower rewet value exhibited by Inventive sample 2 and Comparative sample 2, demonstrate that the nonwoven topsheet of the present disclosure provide a significant rewet benefit over that of a conventional film topsheet. The lower acquisition speeds of Inventive sample 2 over that of Comparative sample 2, demonstrate that the combination of the nonwoven topsheet of the present disclosure, when coupled with the fluid management layer of the present disclosure, can exhibit both reduced rewet coupled with faster acquisition speeds.

So, with the above in mind, articles of the present disclosure may exhibit an acquisition speed of less than 40 seconds on the first gush, less than 35 seconds, or less than 30 seconds. For example, an article of the present disclosure may exhibit an acquisition speed for the first gush in the range of about 10 seconds to about 40 second, from about 10 seconds to about 35 seconds, or from about 10 seconds to about 30 seconds, specifically including all values within these ranges and any ranges created thereby.

Regarding the second gush, articles of the present disclosure may exhibit an acquisition speed of less than 100 seconds, less than 80 seconds, or less than about 60 seconds. For example, article of the present disclosure may exhibit an acquisition speed for the second gush of from between about 20 seconds to about 100 seconds, from about 20 seconds to about 80 seconds, or from about 20 seconds to about 60 seconds, specifically including all values within these ranges and any ranges created thereby.

Regarding the third gush, articles of the present disclosure may exhibit an acquisition speed of less than about 160 seconds, less than about 140 seconds, or less than about 120 seconds. For example, articles of the present disclosure may exhibit an acquisition speed on the third gush of from between about 35 seconds to about 160 seconds, from about 35 seconds to about 140 seconds, or from about 35 seconds to about 120 seconds, specifically reciting all values within these ranges and any ranges created thereby.

It is worth noting that there is much significance in the fact that the Inventive sample 2 also has a smaller difference from the first gush acquisition time to the second gush, from the second gush to the third gush, and from the first gush to the third gush. As noted previously, the fluid management layer of the present disclosure can withstand the loss of integrity of the absorbent fibers better than the fluid management layer of its Comparative sample 2 counterpart. Table 6 lists the differences between the first gush and second gush, second gush and third gush, and first gush and third gush are shown for the Inventive sample 2 and the Comparative sample 2.

TABLE 6

Inventive
Comparative

Difference (sec)
sample 2
sample 2

Second gush − First gush
22.7
67.9

Third gush − Second gush
28.0
69.6

Third gush − First gush
50.7
137.5

As shown, the Inventive sample 2 lost acquisition speed at a much lower rate than did the Comparative sample 2 from gush to gush. For example, absorbent articles of the present disclosure may exhibit a difference between a second gush and first gush of less than about 60 seconds, less than about 50 seconds, or less than about 40 seconds. As another example, absorbent articles of the present disclosure can exhibit a difference between the second gush and first gush of from between about 11 seconds to about 60 seconds, from about 11 seconds to about 50 seconds, or from about 11 seconds to about 40 seconds, specifically reciting all values within these ranges and any ranges created thereby.

Regarding a difference between the third gush and second gush, the Inventive sample 2 again exhibited a smaller difference than its Comparative sample 2 counterpart. For example, absorbent articles constructed in accordance with the present disclosure may exhibit a difference between the third gush and second gush of less than about 60 seconds less than about 50 seconds, or less than about 40 seconds. As another example, absorbent articles of the present disclosure can exhibit a difference between the third gush and second gush of from between about 14 seconds to about 60 seconds, from about 14 seconds to about 50 seconds, or from about 14 seconds to about 40 seconds, specifically reciting all values within these ranges and any ranges created thereby.

Regarding a difference between the third gush and the first gush, the Inventive sample 2 once again exhibited a smaller difference than its Comparative sample 2 counterpart. For example, absorbent articles constructed in accordance with the present disclosure may exhibit a difference between the third gush and first gush of less than about 120 seconds, less than about 90 seconds, or less than about 60 seconds. As another example, absorbent articles of the present disclosure can exhibit a difference between the third gush and first gush of from between about 25 seconds to about 120 seconds, from about 25 seconds to about 90 seconds, or from about 25 seconds to about 60 seconds, specifically reciting all values within these ranges and any ranges created thereby.

And, as demonstrated, articles of the present disclosure can exhibit the acquisition speeds mentioned heretofore while also exhibiting a rewet of less than about 1.0 grams, less than about 0.8 grams, or less than about 0.6 grams. For example, articles of the present disclosure may exhibit rewet values in the range of from about 0.1 grams to about 1.0 grams, from about 0.1 grams to about 0.8 grams, or from about 0.1 grams to about 0.6 grams, specifically including all values created by these ranges and any ranges created thereby.

Additionally, as mentioned previously, articles of the present disclosure do a great job in mitigating stain size. Data regarding the average stain size exhibited by articles is provided in Table 7.

TABLE 7

Stain Size

Sample
(mm{circumflex over ( )}2)

Comparative sample 1
2940.9

Inventive sample 1
1914.9

As shown, the articles of the Inventive sample 1 exhibited on average a 35 percent smaller stain than that of the Comparative sample 1 when measured in accordance with the Stain Size test method. So, articles of the present disclosure can exhibit stain sizes of less than about 2400 mm{circumflex over ( )}2, less than about 2100 mm{circumflex over ( )}2, or less than about 1800 mm{circumflex over ( )}2. For example, article of the present disclosure may exhibit stain sizes of from between about 1200 mm{circumflex over ( )}2 to about 2400 mm{circumflex over ( )}2, from about 1200 mm{circumflex over ( )}2 to about 2100 mm{circumflex over ( )}2, or from about 1200 mm{circumflex over ( )}2 to about 1950 mm{circumflex over ( )}2, specifically reciting all values within these ranges and any ranges created thereby, when measured in accordance with the Stain Size test method.

While the fluid management layers of the present disclosure can provide the user with a soft, more cushiony feeling absorbent article, the fluid management layers of the present disclosure also provide the user with the appropriate stiffness such that their resultant absorbent articles can reduce the likelihood of bunching. A metric which can determine the stiffness of a fluid management layer is MD Bending Length. The fluid management layers of the present disclosure may have an MD Bending Length of from between about 4 mN/cm to about 12 mN/cm, specifically reciting all values within these ranges and any ranges created thereby.

Absorbent Articles

Referring back to FIGS. 1A and 1B, as mentioned previously, disposable absorbent articles of the present disclosure may comprise the topsheet 20 and the backsheet 50. Sandwiched therebetween may be the fluid management layer 30 and the absorbent core 40. Additional layers may be positioned between the topsheet 20 and the backsheet 50.

The topsheet 20 may be joined to the backsheet 50 by attachment methods (not shown) such as those well known in the art. The topsheet 20 and the backsheet 50 may be joined directly to each other in the article periphery and may be indirectly joined together by directly joining them to the absorbent core 40, the fluid management layer 30, and/or additional layers disposed between the topsheet 20 and the backsheet 50. This indirect or direct joining may be accomplished by attachment methods which are well known in the art. For example, the layers, e.g. topsheet and fluid management layer may be joined via fusion bonds, ultrasonic bonds, pressure bonds, adhesive, or combinations thereof.

The topsheet 20 may be compliant, soft feeling, and non-irritating to the wearer's skin. Suitable topsheet materials include a liquid pervious material that is oriented towards and contacts the body of the wearer permitting bodily discharges to rapidly penetrate through it without allowing fluid to flow back through the topsheet to the skin of the wearer. The topsheet, while being capable of allowing rapid transfer of fluid through it, may also provide for the transfer or migration of the lotion composition onto an external or internal portion of a wearer's skin. The topsheet may comprise a nonwoven material.

Nonlimiting examples of woven and nonwoven materials suitable for use as the topsheet include fibrous materials made from natural fibers, e.g. cotton, including 100 percent organic cotton, modified natural fibers, synthetic fibers, or combinations thereof. These fibrous materials can be either hydrophilic or hydrophobic, but it is preferable that the topsheet be hydrophobic or rendered hydrophobic. As an option, portions of the topsheet can be rendered hydrophilic, by the use of any known method for making topsheets containing hydrophilic components. Nonwoven fibrous topsheets 20 may be produced by any known procedure for making nonwoven webs, nonlimiting examples of which include spunbonding, carding, wet-laid, air-laid, meltblown, needle-punching, mechanical entangling, thermo-mechanical entangling, and hydroentangling.

Nonwoven materials suitable for use as a topsheet may comprise one strata of fibers or may be laminate of multiple nonwoven strata, which may comprise the same or different compositions (e.g., spunbond-meltblown laminate). In one specific example, the topsheet is a carded, air-through bonded nonwoven.

The nonwoven may comprise a mix of hydrophobic and hydrophilic fibers. For example, the nonwoven may comprise at least about 40 percent, more preferably at least about 50 percent, or most preferably at least about 60 percent hydrophilic fibers by weight of the fibers, specifically including all values within these ranges and any ranges created thereby. For example, the nonwoven topsheet may comprise from between 40 percent by weight to about 70 percent by weight, more preferably from about 45 percent by weight to about 68 percent by weight, or most preferably from about 50 percent by weight to about 65 percent by weight of hydrophilic fibers, specifically reciting all values within these ranges and any ranges created thereby.

Additionally or alternatively, the nonwoven may comprise 60 percent or less, more preferably 50 percent or less, or most preferably 40 percent or less of hydrophobic fibers by weight of the fibers, specifically including all values within these ranges and any ranges created thereby. For example, the nonwoven topsheet of the present disclosure may comprise from between about 30 percent by weight to about 60 percent by weight, more preferably from about 32 percent by weight to about 50 percent by weight, or most preferably from about 35 percent by weight to about 45 percent by weight, specifically reciting all values within these ranges and any ranges created thereby. In one specific example, nonwoven topsheets of the present disclosure may comprise about 60 percent by weight hydrophilic fibers and about 40 percent by weight hydrophobic fibers.

Without wishing to be bound by theory, it is believed that where a majority of the fibers are hydrophilic, fluid acquisition speed can be improved while not overly impacting rewet in a negative or too negative a manner. Where less rewet is the goal, then the converse may be true. Namely, a higher percentage weight of hydrophobic fibers may be utilized.

The fibers may comprise a linear density of between about 1.3 dtex to about 4.4 dtex, more preferably from about 1.4 dtex to about 3.3 dtex, or most preferably from about 1.7 dtex to about 2.8 dtex, specifically reciting all values in 0.1 increments therein, and all ranges created thereby. In one specific example, the fibers of the nonwoven topsheet of the present disclosure may comprise a linear density of about 2.2 dtex. It is worth noting that fibers with varying linear densities within the ranges described may be utilized as well.

Without wishing to be bound by theory, it is believed that utilization of fibers having a higher linear density than 4.4 dtex, may lead to a topsheet which does not have the desired softness properties as these larger fibers would tend to be more stiff. Conversely, fibers having a linear density of less than about 1.3 dtex, can decrease the interstitial spaces between adjacent fibers and make fluid acquisition, even with apertures, more challenging.

Nonwoven topsheets of the present disclosure may comprise fibers having a myriad of constituent chemistries. For example, fibers may be formed from polymeric materials, such as polyethylene (PE) and/or polyethylene terephthalate (PET). Fibers may be in the form of bi-component fibers. In nonlimiting examples, bi-component fibers which may comprise PET as a core in combination with another polymer as a sheath. In further nonlimiting examples, PE may be used as a sheath in combination with a PET core.

Other polymeric materials may be utilized. For example, polypropylene, polyethylene, co-polyethylene terephthalate, co-polypropylene, and the like may be utilized. It is recommended that the polymer with the lower melting temperature be provided as the sheath where core-sheath bi-component fibers are utilized. Additionally, without wishing to be bound by theory, it is believed that the use of polyethylene terephthalate as a core can provide resilience to the topsheet.

Suitable fibers may be staple fibers having a length of at least about 30 mm, or at least about 40 mm, or about at least about 50 mm, or up to about 55 mm, or from about 30 to about 55 mm, or from about 35 to about 52 mm, reciting for said range every 1 mm increment therein. In nonlimiting examples, staple fibers may have a length of about 38 mm.

The topsheet may be apertured. Apertures may comprise a diameter of about 0.5 mm to about 2 mm, reciting for said range every 0.1 mm therein. Without wishing to be bound by theory, it is believed that the where the apertures are too oval in nature, that such apertures can negatively impact fluid acquisition speeds. With this in mind, the apertures of the nonwoven topsheets of the present disclosure comprise an aspect ratio (MD length CD length). The aspect ratio of apertures can be from 1.5:1 to 1:1.5, more preferably 0.2:1 to about 1:1.2, or most preferably about 1:1.

The topsheet may comprise a basis weight of at least about 15 gsm, more preferably at least about 40 gsm, or most preferably at least about 60 gsm, specifically reciting all values within these ranges and any ranges created thereby. For example, the nonwoven topsheets of the present disclosure may have a basis weight of from between about 15 gsm to about 80 gsm, more preferably from about 20 gsm to about 60 gsm, or most preferably from about 20 gsm to about 40 gsm, specifically reciting all values within these ranges and any ranges created thereby.

The topsheet may be void of film. Known topsheets for feminine care hygiene products typically include a film, such as hydroformed film, which can be in combination with a nonwoven substrate. The film may prevent liquids from resurfacing and contacting the wearer. The inventors have surprisingly found that a topsheet having the characteristics described herein, particularly in combination with the fluid management layer described herein, can effectively prevent rewet to the same degree or better than articles having topsheets comprising film. Without being bound by theory, it is believed that the careful selection of the fiber types in each of the strata in the fluid management layer and the linear densities of the fiber types can achieve the desired outcome of quick acquisition and low rewet to counteract the typical tradeoffs associated with prior nonwoven topsheets. The improved performance is evident from the new combination of the unique nonwoven topsheet with a fluid management layer of the present disclosure.

The backsheet 50 may be positioned adjacent a garment-facing surface of the absorbent core 40 and may be joined thereto by attachment methods such as those well known in the art. For example, the backsheet 50 may be secured to the absorbent core 40 by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Alternatively, the attachment methods may comprise using heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment methods or combinations of these attachment methods as are known in the art.

The backsheet 50 may be impervious, or substantially impervious, to liquids (e.g., urine) and may be manufactured from a thin plastic film, although other flexible liquid impervious materials may also be used. As used herein, the term “flexible” refers to materials which are compliant and will readily conform to the general shape and contours of the human body. The backsheet 207 may prevent, or at least inhibit, the exudates absorbed and contained in the absorbent core 205 from wetting articles of clothing which contact the incontinence pad 10 such as undergarments. However, the backsheet 50 may permit vapors to escape from the absorbent core 40 (i.e., is breathable) while in some cases the backsheet 50 may not permit vapors to escape (i.e., non-breathable). Thus, the backsheet 50 may comprise a polymeric film such as thermoplastic films of polyethylene or polypropylene. A suitable material for the backsheet 50 is a thermoplastic film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils), for example. Any suitable backsheet known in the art may be utilized with the present invention.

The backsheet 50 acts as a barrier to any absorbed bodily fluids that may pass through the absorbent core 40 to the garment surface thereof with a resulting reduction in risk of staining undergarments or other clothing. A preferred material is a soft, smooth, compliant, liquid and vapor pervious material that provides for softness and conformability for comfort, and is low noise producing so that movement does not cause unwanted sound.

Exemplary backsheets are described in U.S. Pat. No. 5,885,265 (Osborn, III.) issued Mar. 23, 1999; U.S. Pat. No. 6,462,251 (Cimini) issued Oct. 8, 2002; U.S. Pat. No. 6,623,464 (Bewick-Sonntag) issued Sep. 23, 2003 or U.S. Pat. No. 6,664,439 (Arndt) issued Dec. 16, 2003. Suitable dual or multi-layer breathable backsheets for use herein include those exemplified in U.S. Pat. Nos. 3,881,489, 4,341,216, 4,713,068, 4,818,600, EP 203 821, EP 710 471, EP 710 472, and EP 793 952.

Suitable breathable backsheets for use herein include all breathable backsheets known in the art. In principle there are two types of breathable backsheets, single layer breathable backsheets which are breathable and impervious to liquids and backsheets having at least two layers, which in combination provide both breathability and liquid imperviousness. Suitable single layer breathable backsheets for use herein include those described for example in GB A 2184 389, GB A 2184 390, GB A 2184 391, U.S. Pat. No. 4,591,523, U.S. Pat. No. 3 989 867, U.S. Pat. No. 3,156,242 and WO 97/24097.

The backsheet may be a nonwoven web having a basis weight between about 20 gsm and about 50 gsm. In one embodiment, the backsheet is a relatively hydrophobic 23 gsm spunbonded nonwoven web of 4 denier polypropylene fibers available from Fiberweb Neuberger, under the designation F102301001. The backsheet may be coated with a non-soluble, liquid swellable material as described in U.S. Pat. No. 6,436,508 (Ciammaichella) issued Aug. 20, 2002. The backsheet has a garment-facing side and an opposite body-facing side. The garment-facing side of the backsheet comprises a non-adhesive area and an adhesive area. The adhesive area may be provided by any conventional means. Pressure sensitive adhesives have been commonly found to work well for this purpose.

The absorbent core 40 of the present disclosure may comprise any suitable shape including but not limited to an oval, a discorectangle, a rectangle, an asymmetric shape, and an hourglass. For example, in some forms of the present invention, the absorbent core 205 may comprise a contoured shape, e.g. narrower in the intermediate region than in the end regions. As yet another example, the absorbent core may comprise a tapered shape having a wider portion in one end region of the pad which tapers to a narrower end region in the other end region of the pad. The absorbent core 40 may comprise varying stiffness in the MD and CD.

The configuration and construction of the absorbent core 40 may vary (e.g., the absorbent core 40 may have varying caliper zones, a hydrophilic gradient, a superabsorbent gradient, or lower average density and lower average basis weight acquisition zones). Further, the size and absorbent capacity of the absorbent core 40 may also be varied to accommodate a variety of wearers. However, the total absorbent capacity of the absorbent core 40 should be compatible with the design loading and the intended use of the disposable absorbent article or incontinence pad 10.

In some forms of the present invention, the absorbent core 40 may comprise a plurality of multi-functional layers that are in addition to the first and second laminates. For example, the absorbent core 40 may comprise a core wrap (not shown) useful for enveloping the first and second laminates and other optional layers. The core wrap may be formed by two nonwoven materials, substrates, laminates, films, or other materials. In a form, the core wrap may only comprise a single material, substrate, laminate, or other material wrapped at least partially around itself.

The absorbent core 40 of the present disclosure may comprise one or more adhesives, for example, to help immobilize the SAP or other absorbent materials within the first and second laminates.

Absorbent cores comprising relatively high amounts of SAP with various core designs are disclosed in U.S. Pat. No. 5,599,335 to Goldman et al., EP 1,447,066 to Busam et al., WO 95/11652 to Tanzer et al., U.S. Pat. Publ. No. 2008/0312622A1 to Hundorf et al., and WO 2012/052172 to Van Malderen. These may be used to configure the superabsorbent layers.

Additions to the core of the present disclosure are envisioned. In particular, potential additions to the current multi-laminate absorbent core are described in U.S. Pat. No. 4,610,678, entitled “High-Density Absorbent Structures” issued to Weisman et al., on Sep. 9, 1986; U.S. Pat. No. 4,673,402, entitled “Absorbent Articles With Dual-Layered Cores”, issued to Weisman et al., on Jun. 16, 1987; U.S. Pat. No. 4,888,231, entitled “Absorbent Core Having A Dusting Layer”, issued to Angstadt on Dec. 19, 1989; and U.S. Pat. No. 4,834,735, entitled “High Density Absorbent Members Having Lower Density and Lower Basis Weight Acquisition Zones”, issued to Alemany et al., on May 30, 1989. The absorbent core may further comprise additional layers that mimic the dual core system containing an acquisition/distribution core of chemically stiffened fibers positioned over an absorbent storage core as detailed in U.S. Pat. No. 5,234,423, entitled “Absorbent Article With Elastic Waist Feature and Enhanced Absorbency” issued to Alemany et al., on Aug. 10, 1993; and in U.S. Pat. No. 5,147,345. These are useful to the extent they do not negate or conflict with the effects of the below described laminates of the absorbent core of the present invention.

Some examples of a suitable absorbent cores 40 that can be used in the absorbent article of the present disclosure is described in U.S. Patent Application Publication Nos. 2018/0098893 and 2018/0098891.

As noted previously, the absorbent articles comprising the fluid management layers of the present disclosure comprised a storage layer. Referring back to FIGS. 1A and 1B, the storage layer would generally be positioned where the absorbent core 40 is described. The storage layer may be constructed as described regarding absorbent cores. The storage layer can contain conventional absorbent materials. In addition to conventional absorbent materials such as creped cellulose wadding, fluffed cellulose fibers, Rayon fibers, wood pulp fibers also known as airfelt, and textile fibers, the storage layer often includes superabsorbent material that imbibes fluids and form hydrogels. Such materials are also known as absorbent gelling materials (AGM) and may be included in particle form. AGM is typically capable of absorbing large quantities of body fluids and retaining them under moderate pressures. Synthetic fibers including cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as ORLON), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters, bi-component fibers, tricomponent fibers, mixtures thereof and the like can also be used in the secondary storage layer. The storage layer can also include filler materials, such as PERLITE, diatomaceous earth, VERMICULITE, or other suitable materials, that lower rewet problems.

The storage layer or fluid storage layer may have absorbent gelling material (agm) in a uniform distribution or may have agm in a non-uniform distribution. The agm may be in the in the form of channels, pockets, stripes, criss-cross patterns, swirls, dots, or any other pattern, either two or three dimensional, that can be imagined by man. The AGM may be sandwiched between a pair of fibrous cover layers. Or AGM may be encapsulated, at least in part, by a single fibrous cover layer.

Portions of the storage layer can be formed only of superabsorbent material or can be formed of superabsorbent materials dispersed in a suitable carrier such as cellulose fibers in the form of fluff or stiffened fibers. One example of a non-limiting storage layer is a first layer formed only of superabsorbent material that is disposed on a second layer that is formed from a dispersion of superabsorbent material within cellulose fibers.

Detailed examples of absorbent cores formed of layers of superabsorbent material and/or layers of superabsorbent material dispersed within cellulose fibers that may be utilized in the absorbent articles (e.g., sanitary napkins, incontinence products) detailed herein are disclosed in U.S. Patent Publication No. 2010/0228209 A1. Absorbent cores comprising relatively high amounts of SAP with various core designs are disclosed in U.S. Pat. No. 5,599,335 to Goldman et al., EP 1,447,066 to Busam et al., WO 95/11652 to Tanzer et al., U.S. Pat. Publ. No. 2008/0312622A1 to Hundorf et al., WO 2012/052172 to Van Malderen, U.S. Pat. No. 8,466,336 to Carlucci, and U.S. Pat. No. 9,693,910 to Carlucci. These may be used to configure the secondary storage layer.

The absorbent article 10 may further comprise barrier cuffs. Some examples of other suitable barrier cuffs are described in U.S. Pat. Nos. 4,695,278; 4,704,115; 4,795,454; 4,909,803; U.S. Patent Application Publication No. 2009/0312730. Additional suitable barrier cuffs are described in U.S. Patent Application Publication Nos. 2018/0098893 and 2018/0098891.

Test and Measurement Methods
Caliper

The caliper, or thickness, of a test specimen is measured as the distance between a reference platform on which the specimen rests and a pressure foot that exerts a specified amount of pressure onto the specimen over a specified amount of time. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity and test specimens are conditioned in this environment for at least 2 hours prior to testing.

Caliper is measured with a manually-operated micrometer equipped with a pressure foot capable of exerting a steady pressure of 0.50 kPa±0.01 kPa onto the test specimen. The manually-operated micrometer is a dead-weight type instrument with readings accurate to 0.01 mm. A suitable instrument is Mitutoyo Series 543 ID-C Digimatic, available from VWR International, or equivalent. The pressure foot is a flat ground circular movable face with a diameter that is smaller than the test specimen and capable of exerting the required pressure. A suitable pressure foot has a diameter of 25.4 mm, however a smaller or larger foot can be used depending on the size of the specimen being measured. The test specimen is supported by a horizontal flat reference platform that is larger than and parallel to the surface of the pressure foot. The system is calibrated and operated per the manufacturer's instructions.

Obtain a test specimen by removing it from an absorbent article, if necessary. When excising the test specimen from an absorbent article, use care to not impart any contamination or distortion to the test specimen layer during the process. The test specimen is obtained from an area free of folds or wrinkles, and it must be larger than the pressure foot.

To measure caliper, first zero the micrometer against the horizontal flat reference platform. Place the test specimen on the platform with the test location centered below the pressure foot. Gently lower the pressure foot with a descent rate of 3.0 mm±1.0 mm per second until the full pressure is exerted onto the test specimen. Wait 5 seconds and then record the caliper of the test specimen to the nearest 0.001 mm. In like fashion, repeat for a total of ten replicate test specimens. Calculate the arithmetic mean for all caliper measurements and report as Caliper to the nearest 0.001 mm.

Caliper Factor

The caliper factor, as mentioned previously is the caliper per 10 gsm of basis weight of the sample. So, the equation is caliper/(basis weight/10).

Basis Weight

The basis weight of a test sample is the mass (in grams) per unit area (in square meters) of a single layer of material and is measured in accordance with compendial method WSP 130.1. The mass of the test sample is cut to a known area, and the mass of the sample is determined using an analytical balance accurate to 0.0001 grams. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity and test samples are conditioned in this environment for at least 2 hours prior to testing.

Measurements are made on test samples taken from rolls or sheets of the raw material, or test samples obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive. To ensure that all adhesive is removed, soak the layer in a suitable solvent that will dissolve the adhesive without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is obtained. The test specimen must be as large as possible so that any inherent material variability is accounted for.

Measure the dimensions of the single layer test specimen using a calibrated steel metal ruler traceable to NIST, or equivalent. Calculate the Area of the test specimen and record to the nearest 0.0001 square meter. Use an analytical balance to obtain the Mass of the test specimen and record to the nearest 0.0001 gram. Calculate Basis Weight by dividing Mass (in grams) by Area (in square meters) and record to the nearest 0.01 grams per square meter (gsm). In like fashion, repeat for a total of ten replicate test specimens. Calculate the arithmetic mean for Basis Weight and report to the nearest 0.01 grams/square meter.

Material Compositional Analysis

The quantitative chemical composition of a test specimen comprising a mixture of fiber types is determined using ISO 1833-1. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity.

Analysis is performed on test samples taken from rolls or sheets of the raw material, or test samples obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. The excised layer should be free from residual adhesive. To ensure that all adhesive is removed, soak the layer in a suitable solvent that will dissolve the adhesive without adversely affecting the material itself. One such solvent is THF (tetrahydrofuran, CAS 109-99-9, for general use, available from any convenient source). After the solvent soak, the material layer is allowed to thoroughly air dry in such a way that prevents undue stretching or other deformation of the material. After the material has dried, a test specimen is obtained and tested as per ISO 1833-1 to quantitatively determine its chemical composition.

Fiber Decitex (Dtex)

Textile webs (e.g. woven, nonwoven, airlaid) are comprised of individual fibers of material. Fibers are measured in terms of linear mass density reported in units of decitex. The decitex value is the mass in grams of a fiber present in 10,000 meters of that fiber. The decitex value of the fibers within a web of material is often reported by manufacturers as part of a specification. If the decitex value of the fiber is not known, it can be calculated by measuring the cross-sectional area of the fiber via a suitable microscopy technique such as scanning electron microscopy (SEM), determining the composition of the fiber with suitable techniques such as FT-IR (Fourier Transform Infrared) spectroscopy and/or DSC (Dynamic Scanning calorimetry), and then using a literature value for density of the composition to calculate the mass in grams of the fiber present in 10,000 meters of the fiber. All testing is performed in a room maintained at a temperature of 23° C.±2.0° C. and a relative humidity of 50%±2% and samples are conditioned under the same environmental conditions for at least 2 hours prior to testing.

If necessary, a representative sample of web material of interest can be excised from an absorbent article. In this case, the web material is removed so as not to stretch, distort, or contaminate the sample.

SEM images are obtained and analyzed as follows to determine the cross-sectional area of a fiber. To analyze the cross section of a sample of web material, a test specimen is prepared as follows. Cut a specimen from the web that is about 1.5 cm (height) by 2.5 cm (length) and free from folds or wrinkles. Submerge the specimen in liquid nitrogen and fracture an edge along the specimen's length with a razor blade (VWR Single Edge Industrial Razor blade No. 9, surgical carbon steel). Sputter coat the specimen with gold and then adhere it to an SEM mount using double-sided conductive tape (Cu, 3M available from electron microscopy sciences). The specimen is oriented such that the cross section is as perpendicular as possible to the detector to minimize any oblique distortion in the measured cross sections. An SEM image is obtained at a resolution sufficient to clearly elucidate the cross sections of the fibers present in the specimen. Fiber cross sections may vary in shape, and some fibers may consist of a plurality of individual filaments. Regardless, the area of each of the fiber cross sections is determined (for example, using diameters for round fibers, major and minor axes for elliptical fibers, and image analysis for more complicated shapes). If fiber cross sections indicate inhomogeneous cross-sectional composition, the area of each recognizable component is recorded and dtex contributions are calculated for each component and subsequently summed. For example, if the fiber is bi-component, the cross-sectional area is measured separately for the core and sheath, and dtex contribution from core and sheath are each calculated and summed. If the fiber is hollow, the cross-sectional area excludes the inner portion of the fiber comprised of air, which does not appreciably contribute to fiber dtex. Altogether, at least 100 such measurements of cross-sectional area are made for each fiber type present in the specimen, and the arithmetic mean of the cross-sectional area a_kfor each are recorded in units of micrometers squared (μm²) to the nearest 0.1 μm².

Fiber composition is determined using common characterization techniques such as FTIR spectroscopy. For more complicated fiber compositions (such as polypropylene core/polyethylene sheath bi-component fibers), a combination of common techniques (e.g. FTIR spectroscopy and DSC) may be required to fully characterize the fiber composition. Repeat this process for each fiber type present in the web material.

The decitex d_kvalue for each fiber type in the web material is calculated as follows:

d_k=10 000 m×a_k×ρ_k×10⁻⁶

where d_kis in units of grams (per calculated 10,000 meter length), a_kis in units of μm², and ρ_kis in units of grams per cubic centimeter (g/cm³). Decitex is reported to the nearest 0.1 g (per calculated 10,000 meter length) along with the fiber type (e.g. PP, PET, cellulose, PP/PET bico).

Artificial Menstrual Fluid (AMF) Preparation

The Artificial Menstrual Fluid (AMF) is composed of a mixture of defibrinated sheep blood, a phosphate buffered saline solution and a mucous component. The AMF is prepared such that it has a viscosity between 7.15 to 8.65 centistokes at 23° C.

Viscosity of the AMF is performed using a low viscosity rotary viscometer (a suitable instrument is the Cannon LV-2020 Rotary Viscometer with UL adapter, Cannon Instrument Co., State College, Pa., or equivalent). The appropriate size spindle for the viscosity range is selected, and instrument is operated and calibrated as per the manufacturer. Measurements are taken at 23° C.±1° C. and at 60 rpm. Results are reported to the nearest 0.01 centistokes.

Reagents needed for the AMF preparation include: defibrinated sheep blood with a packed cell volume of 38% or greater (collected under sterile conditions, available from Cleveland Scientific, Inc., Bath, Ohio, or equivalent), gastric mucin with a viscosity target of 3-4 centistokes when prepared as a 2% aqueous solution (crude form, available from Sterilized American Laboratories, Inc., Omaha, Nebr., or equivalent), 10% v/v lactic acid aqueous solution, 10% w/v potassium hydroxide aqueous solution, sodium phosphate dibasic anhydrous (reagent grade), sodium chloride (reagent grade), sodium phosphate monobasic monohydrate (reagent grade) and deionized water, each available from VWR International or equivalent source.

The phosphate buffered saline solution consists of two individually prepared solutions (Solution A and Solution B). To prepare 1 L of Solution A, add 1.38±0.005 g of sodium phosphate monobasic monohydrate and 8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask and add deionized water to volume. Mix thoroughly. To prepare 1 L of Solution B, add 1.42±0.005 g of sodium phosphate dibasic anhydrous and 8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask and add deionized water to volume. Mix thoroughly. To prepare the phosphate buffered saline solution, add 450±10 mL of Solution B to a 1000 mL beaker and stir at low speed on a stir plate. Insert a calibrated pH probe (accurate to 0.1) into the beaker of Solution B and add enough Solution A, while stirring, to bring the pH to 7.2±0.1.

The mucous component is a mixture of the phosphate buffered saline solution, potassium hydroxide aqueous solution, gastric mucin and lactic acid aqueous solution. The amount of gastric mucin added to the mucous component directly affects the final viscosity of the prepared AMF. To determine the amount of gastric mucin needed to achieve AMF within the target viscosity range (7.15-8.65 centistokes at 23° C.) prepare 3 batches of AMF with varying amounts of gastric mucin in the mucous component, and then interpolate the exact amount needed from a concentration versus viscosity curve with a least squares linear fit through the three points. A successful range of gastric mucin is usually between 38 to 50 grams.

To prepare about 500 mL of the mucous component, add 460±10 mL of the previously prepared phosphate buffered saline solution and 7.5±0.5 mL of the 10% w/v potassium hydroxide aqueous solution to a 1000 mL heavy duty glass beaker. Place this beaker onto a stirring hot plate and while stirring, bring the temperature to 45° C.±5° C. Weigh the pre-determined amount of gastric mucin (±0.50 g) and slowly sprinkle it, without clumping, into the previously prepared liquid that has been brought to 45° C. Cover the beaker and continue mixing. Over a period of 15 minutes bring the temperature of this mixture to above 50° C. but not to exceed 80° C. Continue heating with gentle stirring for 2.5 hours while maintaining this temperature range. After the 2.5 hours has elapsed, remove the beaker from the hot plate and cool to below 40° C. Next add 1.8±0.2 mL of the 10% v/v lactic acid aqueous solution and mix thoroughly. Autoclave the mucous component mixture at 121° C. for 15 minutes and allow 5 minutes for cool down. Remove the mixture of mucous component from the autoclave and stir until the temperature reaches 23° C.±1° C.

Allow the temperature of the sheep blood and mucous component to come to 23° C.±1° C. Using a 500 mL graduated cylinder, measure the volume of the entire batch of the previously prepared mucous component and add it to a 1200 mL beaker. Add an equal volume of sheep blood to the beaker and mix thoroughly. Using the viscosity method previously described, ensure the viscosity of the AMF is between 7.15-8.65 centistokes. If not the batch is disposed and another batch is made adjusting the mucous component as appropriate.

The qualified AMF should be refrigerated at 4° C. unless intended for immediate use. AMF may be stored in an air-tight container at 4° C. for up to 48 hours after preparation. Prior to testing, the AMF must be brought to 23° C.±1° C. Any unused portion is discarded after testing is complete.

Repetitive Acquisition Time and Rewet

Acquisition time is measured for an absorbent article dosed with Artificial Menstrual Fluid (AMF) as described herein, using a strikethrough plate and an electronic circuit interval timer. The time required for the absorbent article to acquire a series of doses of AMF is recorded. Subsequent to the acquisition test, a rewet test is performed. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity.

Referring to FIGS. 7 to 9B, the strikethrough plate 9001 is constructed of Plexiglas with an overall dimension of 10.2 cm long by 10.2 cm wide by 3.2 cm tall. A longitudinal channel 9007 that runs the length of the plate is 13 mm deep, 28 mm wide at the top plane of the plate, with lateral walls that slope downward at 65° to a 15 mm wide base. A central test fluid well 9009 is 26 mm long, 24 mm deep, 38 mm wide at the top plane of the plate with lateral walls that slope downward at 65° to a 15 mm wide base. At the base of the test fluid well 9009, there is an “H” shaped test fluid reservoir 9003 open to the bottom of the plate for the fluid to be introduced onto the underlying test sample. The test fluid reservoir 9003 has an overall length of 25 mm, width of 15 mm, and depth of 8 mm. The longitudinal legs of the reservoir are 4 mm wide and have rounded ends with a radius 9010 of 2 mm. The legs are 3.5 mm apart. The central strut has a radius 9011 of 3 mm and houses the opposing electrodes 6 mm apart. The lateral sides of the reservoir bow outward at a radius 9012 of 14 mm bounded by the overall width 2013 of 15 mm. Two wells 9002 (80.5 mm long×24.5 mm wide×25 mm deep) located outboard of the lateral channel, are filled with lead shot (or equivalent) to adjust the overall mass of the plate to provide a constraining pressure of 0.25 psi (17.6 g/cm²) to the test area. Electrodes 9004 are embedded in the plate 9001, connecting the exterior banana jacks 9006 to the inside wall 9005 of the fluid reservoir 9003. A circuit interval timer is plugged into the jacks 9006, and monitors the impedance between the two electrodes 9004, and measures the time from introduction of the AMF into reservoir 9003 until the AMF drains from the reservoir. The timer has a resolution of 0.01 sec.

For the rewet portion of the test, the pressure applied to the test sample is 1.0 psi. The rewet weight is constructed such that the dimensions of the bottom face of the weight match the dimensions of the strikethrough plate, and the total mass required is calculated to give a pressure of 1.0 psi over the bottom face of the weight. Thus, the bottom face of the weight is 10.2 cm long by 10.2 cm wide, and constructed of a flat, smooth rigid material (e.g. stainless steel) to give a mass of 7.31 kg.

For each test sample, seven plies of filter paper cut to 150 mm diameter are used as the rewet substrate. The filter paper is conditioned at 23° C.±2° C. and 50%±2% relative humidity for at least 2 hours prior to testing. A suitable filter paper has a basis weight of about 74 gsm, a thickness of about 157 microns with medium porosity, and is available from VWR International as grade 413.

Test samples are removed from all packaging using care not to press down or pull on the products while handling. No attempt is made to smooth out wrinkles. The test samples are conditioned at 23° C.±2° C. and 50%±2% relative humidity for at least 2 hours prior to testing. Determine the dose location as follows. For symmetrical samples (i.e. the front of the sample is the same shape and size as the back of the sample when laterally divided along the midpoint of the longitudinal axis of the sample), the dose location is the intersection of the midpoints of the longitudinal axis and lateral axis of the sample. For asymmetrical samples (i.e. the front of the sample is not the same shape and size as the back of the sample when laterally divided along the midpoint of the longitudinal axis of the sample), the dose location is the intersection of the midpoint of the longitudinal axis of the sample and a lateral axis positioned at the midpoint of the sample's wings.

The required mass of the strikethrough plate must be calculated for the specific dimensions of the test sample such that a constraining pressure of 0.25 psi is applied. Measure and record the lateral width of the core at the dose location to the nearest 0.1 cm. The required mass of the strikethrough plate is calculated as the core width multiplied by the length of the strikethrough plate (10.2 cm) multiplied by 17.6 g/cm²and recorded to the nearest 0.1 g. Add lead shot (or equivalent) to the wells 9002 in the strikethrough plate to achieve the calculated mass.

Connect the electronic circuit interval timer to the strikethrough plate 9001 and zero the timer. Place the test sample onto a flat, horizontal surface with the body side facing up. Gently place the strikethrough plate 9001 onto the center of the test sample ensuring that the “H” shaped reservoir 9003 is centered over the predetermined dose location.

Using a mechanical pipette, accurately pipette 3.00 mL±0.05 mL of AMF into the test fluid reservoir 9003. The fluid is dispensed, without splashing, along the molded lip of the bottom of the reservoir 9003 within a period of 3 seconds or less. Immediately after the fluid has been acquired, record the acquisition time to the nearest 0.01 seconds and start a 5 minute timer. In like fashion, apply a second and third dose of AMF into the test fluid reservoir, with a 5 minute wait time between each dose. Record the acquisition times to the nearest 0.001 seconds. Immediately after the 3^rddose of AMF has been acquired, start a 5 minute timer and prepare the filter papers for the rewet portion of the test.

Obtain the mass of 7 plies of the filter paper and record as Dry Mass_fpto the nearest 0.001 grams. When 5 minutes have elapsed after the third acquisition, gently remove the strikethrough plate from the test sample and set aside. Place the 7 plies of pre-weighed filter paper onto the test sample, centering the stack over the dosing location. Now place the rewet weight centered over the top of the filter papers and start a 15 second timer. As soon as 15 seconds have elapsed, gently remove the rewet weight and set aside. Obtain the mass of the 7 plies of filter paper and record as Wet Mass_fpto the nearest 0.001 grams. Subtract the Dry Mass_fpfrom the Wet Mass_fpand report as Rewet Value to the nearest 0.001 grams. Thoroughly clean the electrodes 9004 and wipe off any residual test fluid from the bottom faces of the strikethrough plate and rewet weight prior to testing the next sample.

Immediately following the rewet portion of the test, proceed to the Stain Size method using the dosed test sample, as described herein.

In like fashion, repeat the entire procedure on ten replicate samples. The reported value is the arithmetic mean of the ten individual recorded measurements for Acquisition Times (first, second and third) to the nearest 0.001 seconds and Rewet Value to the nearest 0.001 grams.

Stain Size Measurement Method

This method describes how to measure the size of a fluid stain visible on an absorbent article. This procedure is performed on test samples immediately after they have been dosed with test liquid according to a separate method, as described herein (e.g. the Repetitive Acquisition and Rewet method). The resultant test samples are photographed under controlled conditions. Each photographic image is then analyzed using image analysis software to obtain measurements of the size of the resulting visible stain. All measurements are performed at constant temperature (23° C.±2° C.) and relative humidity (50%±2%).

The test sample along with a calibrated ruler (traceable to NIST or equivalent) are laid horizontally flat on a matte black background inside a light box that provides stable uniform lighting evenly across the entire base of the light box. A suitable light box is the Sanoto MK50 (Sanoto, Guangdong, China), or equivalent, which provides an illumination of 5500 LUX at a color temperature of 5500K. A Digital Single-Lens Reflex (DSLR) camera with manual setting controls (e.g. a Nikon D40X available from Nikon Inc., Tokyo, Japan, or equivalent) is mounted directly above an opening in the top of the light box so that the entire article and ruler are visible within the camera's field of view.

Using a standard 18% gray card (e.g., Munsell 18% Reflectance (Gray) Neutral Patch/Kodak Gray Card R-27, available from X-Rite; Grand Rapids, Mich., or equivalent) the camera's white balance is custom set for the lighting conditions inside the light box. The camera's manual settings are set so that the image is properly exposed such that there is no signal clipping in any of the color channels. Suitable settings might be an aperture setting of f/11, an ISO setting of 400, and a shutter speed setting of 1/400 sec. At a focal length of 35 mm the camera is mounted approximately 14 inches above the article. The image is properly focused, captured, and saved as a JPEG file. The resulting image must contain the entire test sample and distance scale at a minimum resolution of 15 pixels/mm.

To analyze the image, transfer it onto a computer running an image analysis software (a suitable software is MATLAB, available from The Mathworks, Inc, Natick, Mass., or equivalent). The image resolution is calibrated using the calibrated distance scale in the image to determine the number of pixels per millimeter. The image is analyzed by manually drawing the region of interest (ROI) boundary around the visibly discernable perimeter of the stain created by the previously dosed test liquid. The area of the ROI is calculated and reported as the Overall Stain Area to the nearest 0.01 mm²along with notation as to which method was used to generate the test sample being analyzed (e.g. Repetitive Acquisition and Rewet).

This entire procedure is repeated on all of the replicate test samples generated from the dosing method(s). The reported value is the average of the individual recorded measurements for the Overall Stain Area to the nearest 0.01 mm²along with notation as to which method was used to generate the test samples that were analyzed (e.g. Repetitive Acquisition and Rewet).

Dynamic Mechanical Analysis

A Dynamic Mechanical Analyzer (DMA) is used to measure compression resistance and recovery properties of test specimens obtained from an individual material or a portion of an absorbent article. A suitable instrument is the DMA Q800 (available from TA Instruments, New Castle, Del.), or equivalent, equipped with 40 mm diameter compression plates. The test specimen is exposed to a series of axial compression force ramps with controlled changes in stress, and the resultant change in displacement is measured. All testing is performed in a room controlled at 23° C.±3° C. and 50%±2% relative humidity.

Samples are conditioned at 23° C.±3° C. and 50%±2% relative humidity for at least 2 hours before testing. When testing a whole article, remove the release paper from any panty fastening adhesive on the garment facing side of the article if present. Lightly apply talc powder to the adhesive to mitigate any tackiness. Place the article, body facing surface up, on a bench, then identify and mark the test location as follows. For symmetrical articles (i.e. the front of the article is the same shape and size as the back of the article when laterally divided along the midpoint of the longitudinal axis of the sample), the test location is the intersection of the midpoints of the longitudinal axis and lateral axis of the article. For asymmetrical articles (i.e. the front of the article is not the same shape and size as the back of the article when laterally divided along the midpoint of the longitudinal axis of the article), the test location is the intersection of the midpoint of the longitudinal axis of the article and a lateral axis positioned at the midpoint of the article's wings. Using a round cutting die, cut a 40 mm diameter test specimen centered at the test location. When testing an individual material layer (e.g. a raw material or a layer excised from an article), the test location is determined in the same manner as when testing a whole article based upon where the individual material would be located within said article.

Program the DMA for a controlled force test with force ramps from 0.02 N to 10 N at a rate of 25 N/minute. The test temperature is ambient (23° C.±3° C.), therefore the furnace is left open. Set the Poisson's ratio to 0.44. The data sampling interval is 0.1 s/pt. Data is collected over 5 cyclic force ramps, e.g. 5 force ramps from 0.2 N to 10 N and 5 force ramps from 10.00 N to 0.02 N. The initial thickness of the test specimen is recorded by the instrument when the initial force applied is 0.02 N.

Start the test and collect Force (N) and displacement (mm) data for all five cyclic force ramps. The first half the cycle is the compression step (where force is being applied to the test specimen) whereas the second half of the cycle is the recovery step (where force is being removed from the test specimen). The following intermediate results are calculated for the test specimen.

Displacement [mm]
Total displacement for each row

(abs(actual specimen thickness −

current specimen thickness))

Engineering Strain [ ]
displacement/initial length

Engineering Stress [Pa]
static force/specimen area

(specimen area: π*(0.04*0.5)²

(~0.001257 m²))

Work Increment [mJ]
Approximation using trapezoid rule −

change in thickness times mean force

((x2 − x1) * ½ *(y1 + y2))

Work (by Step#) [mJ]
Approximated area under the force-

displacement curve for each step

(sum of Work Increments, per step)

Energy dissipation
Approximated hysteresis area of the

(by Cycle#) [mJ]
force-displacement curve

(sum of Work Increments, per cycle)

min Thickness (by step#)
Minimum specimen thickness per step

max Thickness (by step#)
Maximum specimen thickness per step

Recovery
recovery based on initial length (cycle 1)

Now for each individual force ramp Cycle (1-5), the following parameters are calculated and reported.

initial length* [mm]
Specimen thickness* at the begin of

each cycle

length after compression [mm]
Specimen thickness at the maximum force

within each cycle

length after recovery [mm]
Specimen thickness at the end of

each cycle

max compression [ ]
Compression strain at maximum force

((initial length − length after

recovery)/initial length)

recovery [ ]
Recovery within a cycle

(1 − ((length after recovery −

initial length)/(length after

compression − initial length)))

modulus at 8 kPa [MPa]
Secant modulus (maximum stress =

maximum force/specimen area; Modulus =

maximum stress/max compression)

compression work [mJ]
Approximated area under the force-

displacement curve of the

Compression step of the cycle (sum of

incremental area in the compression portion

of the cycle using trapezoid rule

(x2 − x1) * ½ *(y1 + y2))

recovery work [mJ]
Approximated area under the force-

displacement curve of the

Recovery step of the cycle (sum of

incremental area in the recovery portion

of the cycle using trapezoid rule

(x2 − x1) * ½ *(y1 + y2))

Energy Dissipation [mJ]
Approximated hysteresis area of the force-

displacement curve (sum of incremental area

for the whole cycle using trapezoid rule

(x2 − x1) * ½ *(y1 + y2))

Compliance [1/Pa]
Inverse of secant modulus

(1/max compression)

In like fashion, repeat for a total of five replicate test specimens and report the arithmetic mean for each calculated parameter.

Liquid Strikethrough Time

Strikethrough time is measured for a test sample insulted with a known volume of test liquid, using a strikethrough plate and an electronic circuit interval timer according to compendial method WSP 70.3. The time required for the test liquid to pass through the test sample is recorded. All measurements are performed in a laboratory maintained at 23° C.±2° C. and 50%±2% relative humidity and test samples are conditioned in this environment for at least 2 hours prior to testing.

The materials required to execute this test are as follows. The test liquid is 0.9% saline (prepared by weighing 9.0 g±0.05 g of reagent grade NaCl into a weigh boat, transferring it into a 1 L volumetric flask and diluting to volume with de-ionized water). The Standard Absorbent Pad that is placed beneath the test sample consists of 5 layers of Ahlstrom Grade 989 filter paper (available from Ahlstrom-Munksjo North America LLC, Alpharetta, Ga.), or equivalent, cut to 10 cm by 10 cm. The strikethrough plate and electronic circuit interval timer are described within the WSP method, and can be purchased from W. Fritz Mezger, Inc (Spartanburg, S.C.) as the Lister AC Strikethrough Tester.

Measurements are made on test samples taken from rolls or sheets of raw material, cut to a size of 10 cm by 10 cm. Measurements can also be made on test samples obtained from a material layer removed from an absorbent article. When excising the material layer from an absorbent article, use care to not impart any contamination or distortion to the layer during the process. If the material layer has been excised from an absorbent article, a test location must be determined and marked as follows. For symmetrical articles (i.e. the front of the article is the same shape and size as the back of the article when laterally divided along the midpoint of the longitudinal axis of the article), the test location is the intersection of the midpoints of the longitudinal axis and lateral axis of the article. For asymmetrical samples (i.e. the front of the article is not the same shape and size as the back of the article when laterally divided along the midpoint of the longitudinal axis of the article), the test location is the intersection of the midpoint of the longitudinal axis of the article and a lateral axis positioned at the midpoint of the article's wings. The entire layer excised from an absorbent article is the test sample in this case, and it is not cut down to a specific size. In this case, it is possible that the width of the test sample may be smaller than 10 cm, however it must be wide enough at the test location to entirely cover the opening of the strikethrough plate.

The test sample is placed onto the filter paper with the side intended to face the body of the wearer facing up and the test location centered at the midpoint of the filter paper. The strikethrough plate is then centered over the test sample and filter paper, and the test is executed as per WSP 70.3. Only a single gush of test liquid is applied, and the strikethrough time is recorded to the nearest 0.01 seconds.

In like fashion, the test is repeated for five replicate test samples, using a fresh stack of filter paper for each replicate. Calculate and report the Strikethrough Time as the arithmetic mean of the replicates to the nearest 0.01 sec.

Wet CD Flexibility

Wet CD flexibility is a measure of the force required to deform an absorbent article loaded with a known volume of Paper Industry Fluid (PIF), as described herein, using a cyclic compression test on a horizontally oriented constant rate of extension tensile tester with a computer interface. The test consists of 7 cycles of load application and load removal, and the average hysteresis area (Flexibility), average initial slope (Initial Stiffness) and average total slope (Total Stiffness) of the force vs displacement curves over the last 3 cycles is calculated. All testing is performed in a room controlled at 23° C.±3° C. and 50%±2% relative humidity.

The tensile tester is equipped with a load frame that consists of two guide profiles, two lead screws, and two moving crossheads (each mounted directly opposite the other). The crossheads are driven symmetrically in opposing directions by two lead screws with a play-free precision ball screw guided by a linear guide via two carriages on ball bearings. A suitable instrument can be purchased from Zwick Roell (Ulm, Germany) as item D0724788. The instrument is calibrated and operated according to the manufacturer's instructions. A single load cell, for which forces measured are within 10% to 90% of the limit of the cell, is mounted on one of the moving crossheads. The tensile tester is equipped with an identical set of rounded-edge grips that are used to hold the test sample, with one attached to the moving crosshead on the right and the other attached to the moving crosshead on the left, both centrally aligned with the pull axis of the tensile tester. The rounded-edge grips have a hemisphere-shape with a radius of 50 mm and are constructed in such a way that the test sample can be gripped securely to prevent slippage. Such grips are available from Zwick Roell (Ulm, Germany). The right and left grips are mounted in such a way that they are horizontally and vertically aligned.

Program the tensile tester for a compression test, collecting force (N) and displacement (mm) data at an acquisition rate of 50 Hz as the crosshead travels at a rate of 150 mm/min. The gauge length is set to 55 mm (separation between the outermost edges of the hemispherical grips), with a path length of 20 mm. The compression test consists of seven force cycles. In the first cycle, the grips move from a starting separation distance of 55 mm to a separation distance of 35 mm, and then return to a separation distance of 50 mm. For each of the subsequent 6 cycles, the grips move from a separation distance of 50 mm to 35 mm (force application) and then back to a separation distance of 50 mm (force removal).

For this test, a strip of standard cotton is secured to the garment side of the test sample to cover the Panty Fastening Adhesive (PFA). The standard cotton is 100% bleached cotton weave, about 100 g/m²(Style #429W) available from Testfabrics, Inc., West Pittston, Pa. Additional distributors of this fabric can be found on the Testfabrics website, corn. For this execution, the sidedness of the cotton is not relevant. Prepare a strip of the standard cotton that has a width of 76 mm and a length of about 200 mm. A fresh cotton strip is used for each test sample.

The test articles are conditioned at 23° C.±2° C. and 50%±2% relative humidity for at least 2 hours prior to testing. To prepare the test sample, first remove it from any wrapper present. If the sample is folded, gently unfold it and smooth out any wrinkles. If wings are present, unfold them but leave the release paper intact for now. Place the sample on a horizontally flat rigid surface with the garment side facing up and the wings extended. Remove the PFA protective cover from the back of the sample. With the sample pulled taut, center a strip of standard cotton over the back of the sample (longitudinal axes of both aligned), and secure it to the PFA without creating any wrinkles in the cotton strip or sample. With light pressure, ensure there is good contact between the cotton strip and sample. Now remove the release paper from the wings, fold them around the lateral edges of the strip of cotton, and gently secure them to the cotton. Use care to not impart distortion or compression to the sample during the cotton attachment. Turn the sample and attached cotton over so that the body side of the sample is facing up. Now determine and mark the dosing location as follows. Mark an area that is 40 mm long (aligned with the longitudinal axis of sample) by 30 mm wide (aligned with the lateral axis of the sample) that is centered about the intersection of the midpoints of the longitudinal axis and lateral axis of the sample.

Dose the sample with the test liquid as follows. The test sample is loaded with PIF using a mechanical pipette. Accurately and evenly distribute 7.5 mL of PIF throughout the pre-marked dose location within 5 seconds without splashing. As soon as the PIF has been dispensed from the pipette, start a 10 minute timer. Ensure the tensile tester is programmed and the grips are spaced 55 mm apart, as previously described. After 10 minutes have expired, insert the lateral sides of the test sample into the grips of the tensile tester, ensuring that the sample is centrally aligned at the dose location in both the longitudinal and lateral directions. The lateral axis of the test sample at the longitudinal midpoint is exactly aligned with the central pull axis of the tensile tester. Zero the load cell and start the cyclic compression test, collecting force (N) and displacement (mm) data for all 7 cycles of force application and force removal.

Construct a graph of force (N) versus displacement (mm) for the last 3 cycles (cycles 5-7). Calculate the area of the hysteresis loop for each of the 3 cycles (the entire area created during the load application and load removal) and record to the nearest 0.01 N*mm. Now calculate the average area across all 3 cycles and record as Wet CD Flexibility to the nearest 0.01 N*mm. For each of the 3 cycles, determine the initial slope of the line between displacement values of 5.25 mm and 5.50 mm (during the load application portion of the cycle) and record to the nearest 0.1 N/m. Now calculate the average initial slope across all 3 cycles and record as Initial Stiffness to the nearest 0.1 N/mm. For each of the 3 cycles, determine the total slope of the line between the point that occurs at the minimum force (from the load application portion of the cycle) and the point that occurs at the maximum force (from the load removal portion of the cycle), and record to the nearest 0.1 N/m. Now calculate the average total slope across all 3 cycles and report as Total Stiffness to the nearest 0.1 N/m.

In like fashion, repeat the test for a total of ten replicate test samples. Calculate the arithmetic mean for Wet CD Flexibility and report to the nearest 0.01 N*mm. Calculate the arithmetic mean for Wet CD Initial Stiffness and report to the nearest 0.1 N/m. Calculate the arithmetic mean for Wet CD Total Stiffness and report to the nearest 0.1 N/m.

Paper Industry Fluid (PIF) Preparation

Paper Industry Fluid (PIF) is a widely accepted non-hazardous, non-blood based surrogate fluid for human menses. PIF is an aqueous mixture composed of sodium chloride, carboxymethyl cellulose, glycerol and sodium bicarbonate, and the surface tension is adjusted with the addition of a nonionic surfactant. This standard test fluid was developed by the technical committee of the French industry group of producers of sanitary products (Groupment Francaise de producteurs d'articles pour usage sanitaires et domestiques) and described in the AFNOR standard Normilization francaise Q34-018 of September 1994. When properly prepared, PIF has a viscosity of 11±1 centipoise, a surface tension of 50±2 mN/m and a pH value of 8±1 at a temperature of 23° C.±1° C. Viscosity of the prepared PIF is performed using a low viscosity rotary viscometer (a suitable instrument is the Cannon LV-2020 Rotary Viscometer with UL adapter, Cannon Instrument Co., State College, Pa., or equivalent). The appropriate size spindle for the viscosity range is selected, and the instrument is operated and calibrated as per the manufacturer's instructions. Measurements are taken at 23° C.±1° C. and at 30 rpm. Results are reported to the nearest 0.1 centipoise.

Surface tension of the prepared PIF is performed using a tensiometer. A suitable instrument is the Kruss K100 with a plate method (available from Kruss GmbH, Hamburg, Germany), or equivalent. The instrument is operated and calibrated as per the manufacturer's instructions. Measurements are taken when the aqueous mixture is at a temperature of 23° C.±1° C. Results are reported to the nearest 0.1 mN/m.

Reagents needed for the PIF preparation include: sodium chloride (reagent grade solid), carboxymethyl cellulose (>98% purity, mass fraction), glycerol (reagent grade liquid), sodium bicarbonate (reagent grade solid), a 0.25% wt aqueous solution of polyethylene glycol tert-octylphenyl ether (Triton™ X-100; reagent grade) and deionized water, each reagent available from VWR International or equivalent source.

The following preparation steps will result in about 1 liter of PIF. Add 80.0±0.01 g of glycerol to a 2 L glass beaker. The amount of carboxymethyl cellulose (CMC) directly affects the final viscosity of the prepared PIF, so the amount of CMC is adjusted to yield a final viscosity within the target range (11±1 centipoise). Carboxymethyl cellulose is slowly added to the beaker of glycerol (in an amount between 15-20 grams) while stirring to minimize clumping. Continue stirring for about 30 minutes or until all of the CMC has dissolved and no clumps remain. Now add 1000±1 g of deionized water to the beaker and continue to stir. Next add 10.0±0.01 g of sodium chloride and 4.0±0.01 g of sodium bicarbonate to the beaker while stirring. The amount of nonionic surfactant solution (0.25% wt Triton™ X-100 aqueous) directly affects the final surface tension of the prepared PIF, so the amount of 0.25% wt Triton™ X-100 is adjusted to yield a final surface tension within the target range (50±2 mN/m). The total amount of 0.25% wt Triton X-100 solution to add to the beaker is around 3.7 mL.

Ensure the temperature of the prepared PIF is at 23° C.±1° C. Using the viscosity and surface tension methods previously described, ensure the viscosity is 11±1 centipoise and the surface tension is 50±2 mN/m. Measure the pH of the prepared PIF using pH strips or a pH meter (any convenient source) and ensure the pH is within the target range (8±1). If the prepared batch of PIF does not meet the specified targets, it is disposed and another batch is made adjusting the amounts of CMC and 0.25% wt Triton™ X-100 solution as appropriate.

The qualified batch of PIF is stored covered at 23° C.±1° C. The viscosity, surface tension and pH are tested daily prior to use to ensure the mixture meets the specified targets for each parameter.

MD Bending Length

The measurements for MD Bending Length provided herein were obtained by using Worldwide Strategic Partners (WSP) Test Method 90.1.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”

Every document cited herein, including any cross referenced or related patent or application is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.