TECHNICAL FIELD

The current disclosure pertains to processes and systems for the cationization of natural fiber-containing (e.g., cotton-based) textiles which can be used to improve association of dyes with the cationized textile.

BACKGROUND

Textile dyeing is the process of applying pigments or dyes on textile materials such as fabrics, yarns, and fibers. Desirably, the dyeing process is efficient and rapid, and provides the dyed textile with a desired degree of coloring, and resistance to fading and running of the dye (color fastness). Further, the dyeing process and the materials used therein preferably do not adversely affect the aspects of the textile, such as its flexibility, durability, and tactile properties like softness, smoothness, stiffness. Depending on the material of the textile (e.g., natural, synthetic, or mixtures thereof) and desired coloring, various dye types are used.

Common dyes for cotton have a negative charge. However, in an aqueous solution the surface of the cotton fiber has a neutral or mildly negative charge due to the presence of hydroxyl groups of the cellulosic material that constitute the cotton. Negatively charged dyes get repelled by negatively charged cellulosic material resulting in less dye uptake by the cotton. In order for the textile to be dyed, the surface properties of the cotton fiber must be altered so the dye is not repelled. Traditional dyeing of cotton-based textiles has involved use of a mixture of salts, alkali, and dyes to associate the dye with the material of the cotton fiber. Salt is commonly used in a dyebath to reverse the charge on the cotton fiber, and alkali is used to allow the dyes to react with and associate with the induced positively-charged surface of the cotton fiber. However, these traditional processes can consume significant amounts of water, energy, and chemicals, which is undesirable.

As an alternative to salt and alkali treatment, processes that use cationic reagents to modify cotton fibers are known in the art. Cationic reagents with appropriate chemistries can react with chemical groups on cellulose to provide a permanent cationic (positive) charge on the surface of the cotton fiber (“cationic cotton”). The positive surface charge on the cotton fiber allows it to associate with a greater variety of dyes, and can also allow for a range of color variation (e.g., color depth). Cationization processes for cotton-based textiles may also consume less water, energy, and chemicals, making them desirable for industrial scale operations.

One type of cationizing agent is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC) (e.g., see U.S. Pat. No. 7,201,778; Hashem, M., et al., Textile Res. J., 73:1017, 2003). CHTAC can be reacted with the hydroxyl groups of cellulose in the presence of a base. In first step, the CHTAC is dechlorinated to form the reactive intermediate epoxypropyl trimethyl ammonium chloride (EPTAC), and the epoxide group of this compound can react with a deprotonated hydroxyl group of cellulose, thereby covalently linking the cationic ammonium chloride group to the cellulose backbone through an ther linkage. However, there is a competing reaction with water molecules which results in the epoxide group of EPTAC being hydrolyzed, and generating 2,3-dihydroxypropyl trimethyl ammonium chloride (2,3-DHTAC), which is a waste product. As such, formation of 2,3-DHTAC is desirably minimized. Carrying out “batch” treatment of a textile in the presence of base and cationizing agent at low temperature and an extended period of time can allow better reaction of the cationizing agent with the fiber and can minimize formation of waste product, but such prolonged processing steps are impractical for commercial operations.

Attempts to reduce use of chemicals like salts, alkali, and water for generating and dyeing cationic cotton are made to improve the dying of textiles. Accordingly, the methods and systems of the current disclosure improve cationization of textiles, such as textiles that include natural fibers such as cotton, while reducing use of chemicals in the process. The cationized textile can then be used as an improved substrate in a dyeing process to provide a textile with better color properties.

SUMMARY

The current disclosure provides methods and systems that facilitate the cationization of textiles that contain, or are derived from, natural fibers, such as cotton. The process of the disclosure forms improved cationized textiles that facilitate subsequent textile dyeing and improves properties of the dyed textile, such as coloration.

Using a process as described herein, cationization of textiles can be performed in a short period of time with good results and reduction in waste. Hydrolysis of the cationizing agent is minimized and its reaction with the textile is improved. Subsequent dyeing of the cationized textile provides desirable coloration and color fastness. In turn, the process improves use of reagents by creating less waste products, saves energy by minimizing processing times, and improves overall industrial processing efficiency. Further, the cationizing agent of the disclosure, which is capable of generating two epoxide groups in the presence of the alkali metal hydroxide, when used in conjunction with the cationization methods described herein, can provide better cationization on the treated textile as compared to monohalogenated compounds.

In one aspect, the disclosure provides a method for cationizing a textile including a natural fiber or derivative thereof. The method includes a step of treating a textile including a natural fiber or derivative thereof with an aqueous solution that includes an alkali metal hydroxide and a cationizing agent comprising a halogenated compound capable of generating two epoxide groups in the presence of the alkali metal hydroxide. Next, the textile is treated in an environment with steam at a temperature(s) that is greater than 100° C. but less than 110° C. for a period of time in the range of 1 min to 10 min to react the cationizing agent with the textile.

In embodiments, the textile is heated to a temperature in the environment with steam, or more than one temperature, in the range of greater than 100° C. to less than 105° C., for a period of time in the range of about 2 to 8 minutes.

In embodiments, the textile is heated to a temperature in the environment with steam, or more than one temperature, in the range of greater than 100° C. to less than 104° C., for a period of time in the range of about 3 to 7 minutes.

In embodiments, the textile is heated to a temperature in the environment with steam, or more than one temperature, in the range of greater than 100° C. to less than 103° C., for a period of time in the range of about 4 to 6 minutes.

In some embodiments, after the textile is treated with the aqueous solution that includes the alkali metal hydroxide and the cationizing agent, a portion of the aqueous solution is mechanically removed from the textile.

In some embodiments, the steps of treating with an aqueous solution and mechanically removing are performed at a temperature(s) of less than 35° C., and for a total period of time not greater than 1 minute.

In some embodiments, the steps of treating with aqueous solution, mechanically removing, and treating the textile in an environment comprising steam can be performed for a total a period of time of not more than 11 minutes, such as in the range of 1 minute to 11 minutes, in the range 1 minute to 8 minutes, or in the range 1 minute to 8 minutes, which significantly enhances textile throughput, while at the same time providing good cationization of the textile and incorporated nitrogen content, which in turn facilitates a subsequent dyeing process.

In some embodiments, after steam treatment the textile is then neutralized with an acid-containing solution. The cationic textile can subsequently be dyed in a composition comprising a dye, using the same system that is used for padding and steam treatment, or can be dyed using a different system.

An exemplary halogenated cationizing agent capable of generating two epoxide groups in the presence of alkali metal hydroxide is a bis ether halogenated di-hydroxylated ammonium compound such as bis[(3-chloro-2-hydroxypropyldialkylammonium)alkyl] ether dichloride. In embodiments, the solution has an alkali metal hydroxide to cationizing agent molar ratio of greater than 1:1, such as in the range of 1.8:1 to 5:1, or 2.0:1 to 4.5:1. Such bis-based compounds are preferred when used in conjunction with the methods of the disclosure as they are able to promote cationization and dyeing with significantly reduced chemicals, water, energy, and wastewater generation, while at the same time facilitating the formation of dyed textiles that have desirably bright, bold, and long lasting colors.

In another aspect, the disclosure provides a system for cationizing and dyeing a textile including a natural fiber or derivative thereof. The system includes a padding bath configured to allow treatment of a textile including a natural fiber or derivative thereof with an aqueous solution in the padding bath, the solution including an alkali metal hydroxide and a cationizing agent. The system also includes a steam treatment apparatus configured to treat the padded textile, at a temperature(s) that is greater than 100° C. but less than 110° C. for a period of time in the range of 1 min to 10 min to react the cationizing agent with the textile.

In further embodiments, the system can also include a solution removal apparatus to remove aqueous solution from the padded textile after treatment in the padding bath, with the system including a conveyor apparatus capable of moving the textile through the padding bath and the solution removal apparatus in about a minute or less. The system can also include a neutralization bath to neutralize the textile with an acid-containing solution. The system can include a process controller, such as a computer-based controller, which can be programmed to perform the treatment method as described herein. Optionally, the system can include a dye bath for dyeing the cationized textile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary system for cationization and dyeing of a textile.

FIG. 2 is a graph of nitrogen content on cationized cotton as prepared by a cold batch process versus treatment using different steaming conditions and base to cationizing agent ratios.

DETAILED DESCRIPTION

The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the present invention.

All publications and patents mentioned herein are hereby incorporated by reference. The publications and patents disclosed herein are provided solely for their disclosure. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate any publication and/or patent, including any publication and/or patent cited herein.

The term “about” used preceding any numerical value of the disclosure or appended claims allows some slight imprecision in that stated numerical value, which imprecision may either be understood in the art, or may result from methods of measuring to obtain such numerical values (e.g., such as with chemical or physical measurements), and any numerical value not preceded by the term “about” of the disclosure or appended claims may also be understood the same way.

Methods and compositions of the disclosure described as “comprising” or “including” can include those recited step and compounds, respectively, and optionally can include other steps and components. If methods or compositions of the disclosure are described as “consisting of” those methods or compositions have the recited steps or compounds but do not include steps or compounds that are not recited. The term “consisting essentially of” generally refers to compositions that include the recited compounds and may include other non-recited compounds, but in unsubstantial amounts. For example, such compositions can include one or more other non-recited components but not in an amount that is greater than about 1% (wt), greater than about 0.5% (wt), or greater than about 0.1% (wt), of the total composition. Ina composition “consisting of” the recited components there is no other measurable amount of component other than the recited component, or a method “consisting” of certain steps includes no other steps than those ones recited.

The present disclosure describes methods and systems for cationizing a textile that includes a natural fiber, such as cotton, or derivative thereof. The cationization process can be carried out in a relatively short time period, wherein the process generates low levels of waste and uses minimal energy. The method and system treats the textile in an aqueous solution (which can also be referred to as a “padding” solution) that includes an alkali metal hydroxide and a cationizing agent that is a halogenated compound capable of generating two epoxide groups in the presence of the alkali metal hydroxide, wherein the padding treatment can be performed quickly, such as in a period of not greater than a minute, and at temperatures, such as ambient temperatures, that do not require heating of the aqueous solution. After padding, excess solution is removed from the textile, and then the textile is introduced into a steam heating apparatus to cause reaction of the cationizing agent with the textile. The steam treatment is also performed rather quickly and in a defined temperature range. In particular, the textile is treated in an environment with steam at a temperature(s) that is greater than 100° C. but less than 110° C. for a period of time in the range of 1 min to 10 min. In some embodiments more specific temperature and time ranges can be used.

Advantageously, good cationization is achieved without requiring long padding and reaction times (such as periods of time of hours) characteristic of cold batch padding processes. Instead, it has been discovered that the treatment temperatures and times of the disclosure provide good cationization of the textile while minimizing loss of reagent through hydrolysis. As an additional benefit using the prescribed steam treatment time and temperature, the aqueous padding solution requires less alkali metal hydroxide than typically used for a mono-halogenated compound (as based on reactive groups).

The cationization method of the disclosure renders the textile in excellent condition for association with a dye, and the dyeing process can in turn provide good coloration of the textile. Textile dyeing can be performed using a different system, or with the same system used for padding and steam treatment as described herein.

A “system” according to the disclosure includes apparatus (“system members”) that allow methods of the disclosure to be performed. The system can include one or more of the following apparatuses: baths to hold treatment solutions (padding bath, wash bath, neutralization bath, and/or optionally dyeing bath); textile movement apparatus, such as a conveyor including rollers; solution removal apparatus, such as roller pairs; steaming apparatus, including steam generator, heater, valving; control apparatus, such as a computer-based operation unit.

Steps of the method of the invention can be carried out using a continuous process, a semi-continuous process, a batch process, or a combination thereof.

One option for processing the textile is using a continuous process. A continuous process is a flow product method that is used to manufacture, process, or produce an article avoiding stoppage of the processing flow. In a continuous process, an article that is being processed or manufactured is in motion. In the continuous processing of a textile, the textile is often in the form of a sheet that is moved through two or more processing areas (e.g., “treatment zone(s)”, with the sheet being subjected to different chemical, mechanical, and/or physical processes in each processing area while it is being moved. Movement of the textile in a continuous process can be facilitated using a system apparatus such as a textile conveyor having rollers, which contact and facilitate movement of the textile in a continuous process. A continuous process can be performed on a system of the disclosure as described herein.

In embodiments, two or more steps of the method of the disclosure can be described as a continuous process. For example, in steps of padding the textile in a solution of the base and cationizing agent, mechanically removing a portion of the solution from the padded textile, and then steam treating the textile, the textile can be continuously moved through treatment zones which provide prescribed treatments of the textile in motion. Other steps in the process of cationizing and dyeing (e.g., washing, neutralizing, and/or dyeing) can also be described as continuous, or optionally as non-continuous. FIG. 1 illustrates a system than can be used for the continuous processing of a textile according to methods of the disclosure.

A semi-continuous process can include those wherein a flow product operation (continuous) is stopped and then restarted after a period of time. In some embodiments, two or more steps of the method of the disclosure can be described as a semi-continuous process. For example, depending on desired processing conditions, movement of the textile can be stopped in a treatment zone for a period of time and then restarted to move the textile out of the treatment zone. Methods of the disclosure can use a semi-continuous process wherein movement of the textile is stopped in the steam treatment apparatus for a period of time and temperature described herein suitable for reaction of the cationizing agent with the textile, and then movement of the textile is restarted after the time period to move the textile out of the steam treatment apparatus. A semi-continuous process can be performed on a system of the disclosure as described herein.

Optionally, in embodiments, one or more steps in the method of the disclosure can be performed in a batch process. For example, before a processing step of the disclosure, or after a processing step of the disclosure, the textile can be altered in a way such that it is configured for use in a batch process rather than a continuous process. Alteration may be performed by cutting the textile to provide textile portions which are then used in one or more batch processing steps. In a batch process, the system can include apparatus configured in a way where the textile is not automatically moved from one apparatus to the other otherwise associated with apparatus of a continuous process. For example, in a system that includes apparatus for batch processing step(s), system features such as a conveyor apparatus which otherwise transports the textile from one apparatus to another in a continuous process may not be present in at least some of the apparatus of a system used for batch processing. In embodiments of the disclosure a textile is provided and then processed according to steps as described herein. The term “textile” refers to a flexible material that includes a network of fibers and that is intended to encompass all forms of textile-based articles, including woven textiles, knitted textiles, and non-woven textiles. Textiles can be in the form of sheets (fabrics) or thin strands (yams). Textiles can be formed by art-known techniques involving one or more processes of weaving, knitting, crocheting, felting, or braiding strands of fiber-containing materials together. Exemplary textile substrates can be provided in the form of a textile roll which provides a continuous sheet of textile which may have a width of greater than 1 meter and a length of up to 100 meters or more. With reference to FIG. 1, the arrangement of textile roll 10 to be treated, in relation to other components of the system, is illustrated.

Textiles that are cationized using the cationizing agent and steam treatment according to methods of the disclosure include a natural fiber or derivative thereof. A natural fiber of the textile can be obtained from plants such as cotton, hemp, ramie, flax, jute, kapok, coir, bamboo, and the like. Plant raw fibers can be spun to produce long strands, and the strands can be included in the textile by weaving (interlacing of the strands), knitting (interlooping of the yarns), etc., as known in the art of woven fabrics. In nonwovens, the plant-based fibers are not converted into strands or yarns but are rather directly intermingled with each other or other fibers to produce non-woven fabrics.

The natural fiber in the textile material can include natural polymers such as naturally-occurring polysaccharides like cellulose or cellulosic material, or chitin, or combinations thereof, or derivatives thereof. Cellulose or cellulosic material, which can include modified cellulose, as well as chitin and derivatives thereof, have chemistries that allow reaction with the cationizing agent. Cellulose is composed of repeating glucopyranose subunits which presents three hydroxyl groups on each subunit. Chitosan is composed of repeating glycosamine subunits which presents two hydroxyl groups and one amine group on each subunit. The hydroxyl groups of these polysaccharides are reactive with the hydroxide-activated cationizing agent.

Cellulosic materials also include rayon (viscose), which is generated from wood pulp, and lyocell (e.g., Tencel™), which is a form of rayon. Textile substrates treated according to the disclosure can also include cellulose derivatives such as cellulose acetate, or imidazolidinone-modified cellulose.

The textile can be a blend or mixture of different materials, such as a blend of natural and synthetic fibers. Blends include blends of different types of natural fibers, such as wool/cotton blends, silk/cotton blends, and angora/cotton blends. Animal-based materials can include collagen fibers, keratin fibers, fibroin fibers, or a mixture thereof. Other exemplary blends include blends of cellulosic and synthetic fibers, such as cotton/polyester blends, cotton/polyolefin blends, cotton/polyacrylonitrile blends, cotton/polyamide blends (e.g., cotton/nylon blends), as well as blends of cellulose fibers and cellulose derivative fibers, such as cotton/rayon blends.

If the textile includes a blend of fibers, it preferably has at least about 5% (wt) of a natural fiber such as cotton, or derivative thereof, and more preferably about 25% (wt) or greater, about 35% (wt) or greater, or about 40% (wt) or greater, of the natural fiber (e.g., cellulosic), or derivative thereof. Exemplary blends include a natural fiber (or derivative thereof; e.g., cellulosic)) to synthetic fiber weight ratio in the range of about 5:95 to about 95:5, 25:75 to about 25:75, or 40:60 to about 60:40.

The woven textile can also be described in terms of textile weight (weight/area) which is often expressed in terms of ounces per square yard, or grams per square meter. Textile weight can be affected by the type or types of fibers in the textile and their properties, the type of weave of the textile, and the finish of the textile. Exemplary textile weights typically range from about 50 g/m²to about 1000 g/m², or about 100 g/m²to about 750 g/m².

In embodiments, the process of the disclosure utilizes a bleached textile, or the process further includes a process step of bleaching the textile. A bleached textile can have removed from it natural color, odor, and impurities otherwise present in when the fiber of the textile is in a raw (natural) form. Oxidative bleaching is typically performed using oxidative bleaching agents such as hydrogen peroxide, sodium hypochlorite, sodium chlorite, sulfuric acid, or a combination thereof. Sodium hydrosulphite is often used for reductive bleaching of textiles.

If an optional bleaching step is performed, the textile can be placed in a bleaching bath for treatment with a bleaching solution for a desired period of time. An exemplary bleaching solution includes hydrogen peroxide or sodium hypochlorite in an aqueous solution at a concentration in the range of about 0.5 to 5.0% (wt). After bleaching, the textile can be washed and dried.

The method of the disclosure includes a step of treating the textile with an aqueous treatment solution comprising an alkali metal hydroxide (base) and a cationizing agent.

Treatment of the textile with a solution including base and cationizing agent can be referred to as a “padding” process in which the aqueous solution with the treatment compounds (treatment solution, or padding solution) are placed in contact with the textile. Often, the treatment solution is present in a container (e.g., a “padding bath” or simply a “padder”) into which the textile is submerged. In the padding bath the textile can become saturated with the treatment solution. The base and cationizing agent come into contact with material of the textile (and in a subsequent process step the activated cationizing agent is reacted with the textile in the presence of steam). Alternatively, the aqueous treatment solution can be applied using a spray apparatus, a roller, or a brush. Generally, padding is performed for a short period of time, such as not greater than one minute.

A cationizing agent, as used herein, refers to a compound that is able to associate with the textile material, such as by chemical reaction resulting in covalent bonding between the agent and material of the textile. The reaction imparts a positive (cationic) charge to the textile.

Exemplary cationizing agents include halogenated and hydroxylated ammonium compounds. In the presence of a base, the compound can become dehalogenated and deprotonated to form a reactive glycidyl (epoxy) intermediate compound which in turn can react with hydroxyl groups of cellulosic material in the textile. Amine groups of chitosan-containing textiles can also be reacted with glycidyl-containing ammonium compounds to provide cationization to the textile. Methods and systems of the disclosure use a halogenated compound capable of generating two epoxide groups in the presence of an alkali metal hydroxide.

Exemplary cationizing agents include bis ether di-halogenated di-hydroxylated ammonium compounds, such as those of the following formula I:

[Image Omitted]

wherein R¹and R^1′ are independently selected from alkylene (divalent) groups, such as a C1-C6 alkylene groups like methylene, ethylene, propylene, etc., and R², R^2′, R³, and R^3′, are independently selected from alkyl (monovalent) groups, such as a C1-C6 alkyl groups like methyl, ethyl, propyl, etc., and R⁴and R^4′ are independently selected from alkylene (divalent) groups, such as a C1-C6 alkylene, and X-X′″ are independently selected from halogen atoms, such as Cl, Br, or I.

In some embodiments the halogenated hydroxylated ammonium compound is a bis[(3-chloro-2-hydroxypropyldialkylammonium) alkyl]ether dichloride compound. R¹and R^1′ are methylene, and preferably R², R^2′, R³, and R^3′ are independently selected from methyl, ethyl and propyl, and R⁴and R^4′are preferably methylene, ethylene, or propylene. Exemplary compounds include bis[(3-chloro-2-hydroxypropyldimethyhummonium)ethyl]ether dichloride, bis[(3-chloro-2-hydroxypropyl-dimethylammonium)ethyl]ether dichloride, and bis[(3-chloro-2-hydroxypropylmethylethyl-ammonium)propyl]ether dichloride. See, for example, U.S. Publication No. 2015/0210627.

In embodiments, the treatment solution includes desired types and amounts of base and cationizing agent which facilitate rapid downstream processing in a steaming step, described herein. In embodiments, the concentration of the cationizing agent in the aqueous treatment solution is at least about 20 g/L but preferably not greater than 125 g/L. Preferably, the concentration of the cationizing agent in the aqueous treatment solution is in the range of about 40 to about 105 g/L, about 50 to about 95 g/L, or about 55 to about 85 g/L.

The concentration of cationizing agent can also be expressed in terms of molarity. For a dihalogenated cationizing agent, the concentration in the aqueous treatment solution can be at least about 0.05 molar. Preferably, the concentration of a dihalogenated cationizing agent is in the range of about 0.05 molar to about 0.3 molar, about 0.1 molar to about 0.25 molar, about 0.125 molar to about 0.225 molar, or about 0.14 molar to about 0.2 molar.

Advantageously, by applying the prescribed steam treatment time and temperatures, the aqueous padding solution generally requires less solids reagents than what is often used when mono-halogenated compounds are used for cationization. In particular, the process requires less alkali metal hydroxide, which is beneficial as it reduces waste and increases economic efficiency of the dyeing process.

Exemplary alkali metal hydroxide bases are potassium hydroxide and sodium hydroxide. The amount of base used can be determined by the amount of cationizing agent, and the steam treatment time and temperature. In embodiments, the concentration of the base in the aqueous treatment solution is at least about 10 g/L but preferably not greater than 40 g/L. Preferably, the concentration of the base in the aqueous treatment solution is in the range of about 15 g/L to about 35 g/L, or about 15 g/L to about 30 g/L. Expressed in terms of molarity, when used with the dihalogenated cationizing agent, the concentration of the base in the aqueous treatment solution can be at least about 0.25 molar, or at least about 0.35 molar. Preferably, the concentration of the base when a dihalogenated cationizing agent is used is in the range of about 0.30 molar to about 1.0 molar, about 0.35 molar to about 0.9 molar, or about 0.40 molar to about 0.8 molar.

The amounts of base and cationizing agent in the treatment solution can also be described with reference to the molar ratio of the base to the cationizing agent. In embodiments, the aqueous solution can have a molar ratio of alkali metal hydroxide to di-halogenated cationizing agent of greater than about 1:1, or greater than about 1.8:1, but less than about 5:1. In preferred aspects, the molar ratio of the alkali metal hydroxide to the cationizing agent is in the range of about 1.8:1 to about 5:1, about 2.0:1 to about 4.75:1, or about 2.25:1 to about 4.5:1.

In some modes of practice the aqueous treatment solution further includes a viscosity enhancer (also referred to as an “anti-migration agent”). According to the disclosure use of a viscosity enhancer can improve immobilization of the cationizing agent in the padded textile, which in turn improves reaction efficiency, and then subsequent dyeing of the cationized textile. Exemplary viscosity enhancers include polyvinyl methyl ethers (e.g., having a mean molecular weight of about 100,000), sodium alginates, Gaur gum, carboxymethylcellulose (CMC), low molecular weight cellulose ethers, polyethylene glycols (e.g., having a mean molecular weight in the range of 8,000 to 10,000), poly vinyl caprolactam, and acrylic polymers, with acrylic polymers being a preferred viscosity enhancer. Preferred viscosity enhancers should not disturb the dye, should not cause loss in color brilliance, should have adequate liquor stability, should not cause any hardening of the handle, should have good solubility at room temperature, and should provide good effects in small amounts. In embodiments, the viscosity enhancer is provided to the padding bath to provide a viscosity in the range of about 50 to about 350 cP. In exemplary embodiments, the viscosity enhancers can be used in an amount in the range of about 2% to about 20% (wt), or about 5% to about 10% (wt) in the aqueous padding solution.

The aqueous padding solution is generally maintained at a temperature (or temperatures) not greater than 35° C. Preferably the aqueous padding solution is at a temperature(s) in the range of about 15° C. to about 27° C., or about 18° C. to about 25° C.

In some exemplary modes of practice the method is a continuous process wherein the textile is fed into a treatment bath, the textile is moved through the bath, and then exits the bath. In embodiments, the padding step can be performed quickly Referring to FIG. 1, a sheet 12 of textile is advanced from textile roll 10 and into padding bath 20 which holds treatment solution 22 including cationizing agent and base. Padding bath 20 includes roller set (24a-24c) to facilitate movement and positioning of the advancing textile sheet in the treatment solution 22. The residence time (“padding times”) in the padding bath is defined by the time where a particular portion of the textile enters the bath and then ends when that particular portion leaves the padding bath. Typically, this is greater than 0.5 second, greater than 1 second, or greater than 2 seconds, and generally less than 1 minute, about 45 seconds or less, or about 30 seconds or less. An exemplary padding time is in the range of 1 second to 1 minute, 1 second to 45 seconds, 1 second to 30 seconds, 1 second to 20 seconds, 1 second to seconds, 1 second to 10 seconds, or 2 seconds to 5 seconds.

In embodiments, the residence time of the textile in the padding bath can be determined by the speed of the machine as well as other aspects of the system. For example, based on the rate that the textile conveyor apparatus of the system moves the textile though a treatment area, and the length of the travel path through the treatment area, the residence time of the textile in the treatment area can be known. In exemplary system, the textile conveyor apparatus moves the textile through at least the padding bath at a rate in the range of about 20 meters/min to about 50 meters/min. Exemplary lengths of travel paths through the padding bath can be in the range of about 0.5 meter to about 5 meters, or about 1 meter to about 4 meters.

The padding process can result in the textile becoming “soaked” or “saturated” with the treatment solution. In some modes of practice, as the textile exits the bath excess treatment solution can be removed from the textile and returned to the padding bath.

Referring to FIG. 1, the textile can be advanced out of the treatment solution 22 and through roller pair (26a, 26b) which applies pressure to the padded textile to remove excess treatment solution, which is returned to the padding bath 20. However, sufficient treatment solution is maintained in the textile to provide an amount of base and cationizing agent for reaction with the textile in the subsequent steam treatment step.

The padded textile can be described in terms of the amount of aqueous treatment solution present in the textile (an “effective concentration”). For example, the padded textile can be referred to in terms of a “wet pickup,” which is the amount (weight) of treatment solution present in the textile divided by the weight of dry textile before padding. Generally, the padding step provides a wet pick up of the treatment solution of greater than about 50%. Preferably, the padding step provides a wet pick up of the treatment solution in the range of about 60% to about 80%. In an exemplary scenario, if the cationizing agent is present in the padding bath at 100 g/L, and them is 70% wet pick up, then the effective concentration of the cationizing agent in the textile is 70 g/L, or 7%.

Generally, the padding process and removal of any excess treatment solution from the saturated textile can be performed rather quickly, which facilitates the overall process of cationization and dyeing of the textile.

After the textile has been padded, it is introduced into an apparatus that applies steam energy to the padded textile to promote reaction and bonding of the cationizing agent to the textile. Referring to FIG. 1, a sheet 12 of textile is advanced from roller pair (26a, 26b) into steaming apparatus 30 through opening 32. Steaming apparatus 30 includes roller set (34a-34e) on which the textile can be supported and moved through the steam chamber. The apparatus can also have a steam generator (not shown) which includes a water vessel and a heating element capable of heating a volume of water to boiling to generate steam which is introduced through a conduit (not shown). The chamber can also have a heating element (not shown) to maintain a steam-containing atmosphere at a desired temperature according to the disclosure. The steam treatment step is carried out for a short period of time in a well-defined temperature range.

The steam process can be described with regards to the steam density in the steam chamber. The density of steam is dependent on the temperature of the steam and the size of its container, or the pressure it is under. At 100° C. at normal atmospheric pressure steam (i.e., dry steam) has a density of 0.0006 grams per cubic centimeter (600 g/m). In the method of the disclosure the steam density in the chamber is at least 0.0006 g/cm³. However, the steam chamber will typically include dry steam, wherein all water molecules are in the gaseous state, and also wet steam, where some of the water molecules have lost their energy and condense into airborne water droplets. Optionally, steam used in the method of the disclosure can be referred to by the dryness fraction of wet steam. For example, if the water content in the steam is 5% by mass, then the steam is said to be 95% dry with a dryness fraction 0.95. By comparison, it is noted that under normal atmospheric conditions, a maximum of about 30 grams of water vapor can exist in a cubic meter volume of air with a temperature of about 35° C.

Upon introduction to the steam chamber, the padded textile is rapidly heated to the steam temperature set for the apparatus. Generally, the textile will be heated to the desired temperature in a short period of time, such as less than 15 seconds or less than 10 seconds. The textile may be moved through the steam chamber as it reaches the desired temperature.

The textile is heated to a temperature in the steam chamber, or more than one temperature, that is at least 100° C., but less than 110° C., and then held at this temperature(s) for a period of time in the range of 1 min to 10 min to react the cationizing agent with the textile.

Preferably, the textile is heated to a temperature in the steam chamber, or more than one temperature, in the range of: greater than 100° C. to about 109° C., greater than 100° C. to about 108° C., greater than 100° C. to about 107° C., greater than 100° C. to about 106° C., greater than 100° C. to about 105° C., greater than 100° C. to about 104° C., or greater than of 100° C. to about 103° C. Preferably, the textile is treated at a temperature(s) in any one of these ranges in steam for a period of time in the range of about 1 to about 10 minutes, about 1 to about 9 minutes, about 2 to about 8 minutes, about 2 to about 7 minutes, about 3 to about 7 minutes, about 3 to about 6 minutes, or about 4 to about 6 minutes.

An exemplary heating temperature and treatment time is where the textile is heated to a temperature in the steam chamber, or more than one temperature, in the range of greater than 100° C. to about 105° C., for a period of time in the range of about 2 to about 8 minutes.

Another exemplary heating temperature and treatment time is where the textile is heated to a temperature in the steam chamber, or more than one temperature, in the range of greater than 100° C. to about 104° C., for a period of time in the range of about 3 to about 7 minutes.

Another exemplary heating temperature and treatment time is where the textile is heated to a temperature in the steam chamber, or more than one temperature, in the range of greater than 100° C. to about 103° C., for a period of time in the range of about 4 to about 6 minutes.

The steam treatment temperatures and times of the disclosure can promote rapid reaction of the cationizing agent with reactive chemistries on the textile while minimizing hydrolysis of the cationizing agent, which otherwise renders it nonfunctional.

Optionally, the treated textile can be described in terms of a reaction efficiency of the cationizing agent with the textile. Reaction efficiency can by expressed by the amount of cationizing agent reacted per weight unit of the textile (e.g., mmol cationizing agent per gram of textile material). The reaction efficiency (cationization degree) can be determined by the amount of nitrogen content of the textile as imparted by the cationizing agent. For example, the process of the disclosure provides at least about 0.075 mmol nitrogen (from the cationizing agent) per gram of textile. More typically there is at least about 0.085 mmol, at least about 0.09 mmol, or at least about 0.095 mmol nitrogen (from the cationizing agent) per gram of textile. Determination of reaction of cationizing agent can be determined by analyzing the added ammonium groups to the textile such as by Kjeldahl method or combustion method (e.g., see Schwarzinger, C., et al. (2002) Monatshefte fur Chemie 133:1-17; or Ma, W., et al. (2017) Molecules, 22:2235).

After the cationized textile has been steam treated, it can be washed with a hot aqueous solution. The hot water wash can remove at least a portion of any unreacted or hydrolyzed cationizing agent, base, and/or other optional component (e.g., viscosity enhancer) carried over from the padding bath. For example, in a continuous process, the steam-treated textile can exit the steaming apparatus 30 through an aperture 36, and can be fed into a hot water bath 40. Hot water bath 40 includes roller set (44a-44e) to facilitate movement and positioning of the advancing textile sheet in the hot water.

The hot aqueous solution can have a pH in the range of 6-8. The temperature of the hot water bath is preferably in the range of about 70° C. to about 90° C., or even more preferably in the range of about 75° C. to about 85° C. The cationized textile can be maintained in the hot aqueous bath for a period of time less than 20 min, less than 15 min, such as a time in the range of about 5 to 15 minutes. In a continuous process the textile can be moved through the bath, such as on rollers in the bath, and then the textile can exit the bath after the desired period of washing. The washed textile can be transferred to a neutralization bath without removing water from the textile.

After the cationized textile has been hot water washed, it can be neutralized by treatment with an acid. The acid can react with any remaining base present in the textile, thereby neutralizing the cationized textile. For example, in a continuous process and with reference to FIG. 1, the washed cationized textile can exit the hot water bath 40, can be mechanically treated, such as by passage through a roller pair (not shown) to remove the hot water solution, and then can be fed into a neutralization bath 50 including an aqueous composition with an acid. The neutralization bath 50 can include roller set (54a-54e) to facilitate movement and positioning of the advancing textile sheet in the acid-containing solution of the bath.

The acid-containing solution can have an exemplary pH in the range of about 4 to about 5. For example, the acid solution can be formed using a weak acid, such as acetic acid, citric acid, or oxalic acid, or a combination thereof. The amount of acid can depend on the acid type used, but an exemplary acid is acetic acid at a concentration in the range of about 1 about 2 grams per liter. The acid treatment solution is generally maintained at a temperature (or temperatures) not greater than 35° C. Preferably the acid treatment solution is at a temperature(s) in the range of about 15° C. to about 27° C., or about 18° C. to about 25° C. The cationized textile can be maintained in the acid treatment solution for a period of time less than 20 min, less than 15 min, such as a time in the range of about 5 to 15 minutes. In a continuous process the textile can be moved through the acid treatment solution, such as on rollers in the bath, and then the textile can exit the acid treatment solution after the desired period of washing. Accordingly, a dyeing step and dyeing apparatus may or may not be a part of the method and system of the disclosure.

The system and method of the disclosure may optionally include one or more steps of cold or hot water wash(es) between after neutralization/acid treatment.

After the cationized textile has been neutralized, it can be dyed by treatment with in a dye solution. The dyeing process can be performed using the same system as the padding bath and steam treatment apparatus, or can be performed in a different system, separate from the padding bath and steam treatment apparatus. If the dyeing process is performed using a different system, such as in a dyeing facility at a different location from the facility having the padding/steam treatment system, the cationized textile can be transported to that facility and dyed.

For purposes of discussing a step of dyeing the textile, reference to FIG. 1 showing a system with a dyeing bath is made. For example, in a continuous process, the neutralized cationized textile can exit the neutralization bath 50, can be mechanically treated, such as by passage through a roller pair (not shown) to remove any excess acid solution, and then can be fed into a dye bath 60 including a composition with a dye. The dye bath 60 can include roller set (64a-64e) to facilitate movement and positioning of the advancing textile sheet in the dye solution.

Cationized textiles can accept a variety of dyes and therefore provide good flexibility for color offerings. The cationized textile can provide improved dye association by virtue of chemical interaction between the positively-charged quaternized nitrogens of the textile bound cationizing agent and, for example, anionic groups of an anionic dye. However, the cationized textile can also accept other dye types that associate the dye with the textile in a way that does not rely on the textile-bound cationizing agent.

A “dyeing” process is one that imparts color to a textile, and “dye” refers to any substance that provides color to a textile, which can also include pigments, as described herein. Dyes can be associated with a fiber of the textile by chemical reaction, absorption, dispersion, or a combination thereof. Dyes typically differ in their resistance to sunlight, perspiration, washing, gas, and alkali; their affinity for different fibers; their reaction to cleaning agents and methods; and their solubility and method of application. Exemplary dye types that can be used to color the cationized textiles made using the methods and systems of the disclosure include natural dyes, basic (cationic) dyes, direct (substantive) dyes, sulfur dyes, pigment dyes, vat dyes, reactive dyes, and acid dyes Reactive dyes can react with one or more chemical groups of the textile fiber.

Reactive dyes can be applied from alkaline solution or from neutral solutions which are then alkalized in a separate process. Heat treatment can also be used during dyeing to develop different color shades. After dyeing, the textile can be washed with soap to remove any unfixed dye. Reactive dyes can be used for cationic textiles including cellulose fibers, as well as those including blends of wool, silk, nylon, and acrylics.

Direct dyes can color cellulose fibers directly without requiring the use of a mordant (a dye fixative). Direct dyes can be used for cationic textiles including cellulose fibers, as well as those including blends of wool, silk, nylon, rayon etc.

Sulfur dyes are water-insoluble and made soluble using a reducing agent and alkali pH (e.g., caustic soda and sodium sulfide). Dyeing is done at high temperature with large quantities of salt so that the color penetrates into the fiber. After dyeing the textile is oxidized by exposure to air or by using chemicals to provide desired color shades. Excess dyes and chemicals can be removed by thorough washing. Sulfur dyes are fast to light, washing, and perspiration, and are mostly used for cotton and linen.

Vat dyes are insoluble in water and are typically made soluble by reduction in alkaline solution which allows them to be affixed to textile fibers. Subsequent oxidation or exposure to air restore the dye to its insoluble form. An exemplary vat dye is Indigo. Vat dyes are the fastest dyes for cotton, linen and rayon. Vat dyes are commonly used with mordants to dye other textiles such as wool, nylon, polyesters, acrylics and modacrylics.

Pigments are not technically dyes, but still are used for coloring textiles like cotton, wool and other manmade fibers due to their excellent light fastness. Pigments are typically affixed to fibers of a textile using resins. After dyeing, the textiles are subjected to high temperatures. In some embodiments, a dyeing step according to the disclosure can use a pigment to color the cationized textile. Natural dyes, which are obtained from a natural source such as vegetable, animal, or mineral source, can be used with a cationized textiles. Direct printing is the most common approach to apply a color pattern onto a textile. If done on colored textile, it is known as overprinting. The desired pattern is produced by pressing dye on the textile in a paste form. To prepare the print paste, a thickening agent is added to a limited amount of water and dye is dissolved in it. Earlier, starch was preferred as a thickening agent for printing. More recently, gums or alginates derived from seaweed are preferred as they allow better penetration of color and are easier to wash out. Most pigment printing is done without thickeners because the mixing up of resins, solvents and water produces thickening.

Some dyes used for dyeing cationized textiles include “reactive” or anionic dyes.

Reactive, anionic dyes can include one or more anionic groups, such as sulfonate or carboxylate groups. For example, the anionic dye can include one or more sodium sulfonate (—S0₃Na) groups. The one or more anionic groups can be present in a dye molecule cable of absorbing light in the visible spectrum and having at least one chromophore/color-bearing group with a conjugated system. Commonly used anionic dyes include those based on azo chemistries, anthraquinone chemistries, and triphenyl methane chemistries. Azo dyes are chemically characterized by the group R—N═N—R′, where R and R′ commonly include an aryl group, with various chemical substituents attached to the aryl groups. Other anionic dyes include those having nitro chemistries, azine chemistries, and quinoline chemistries. Acid dyes are a type of anionic dyes that can include acid groups such as carboxylic acid, sulfonic acid, or phosphoric acid groups. Anionic dyes that can be used in methods of the disclosure are described in various references, such as Aspland, J. R., (1997) Textile Dyeing and Coloration, American Association of Textile Chemists and Colorists, AATCC; Knutson, L. (1986) Synthetic Dyes for Natural Fiber, Interweave Press; Revised edition. Examples include those dyes named “Reactive,” “Direct,” and “Acid,” preceded or followed by a color name and a number and/or letter, such as “Reactive Blue 19,” “Direct Blue 71,” “Acid Blue 62,” “Reactive Red ME4BL,” etc.

In some embodiments, the concentration of the anionic dye in the dyeing solution is in the range of about 0.001 g/L to about 5.0 g/L, about 0.01 to about 2 g/L, with more concentrated dye solutions providing a more intense dye color to the textile. In embodiments, the anionic dye solution is generally maintained at a temperature(s) in the range of about 30° C. to about 80° C. Dyeing can be carried out for a desired period of time, such as in the range of about 30 minutes to about 60 minutes. With reference to FIG. 1, after dyeing the textile can be washed (not shown) and then rolled to a roller 72.

Operation of one or more parts of the system can be controlled using a process controller (not shown), such as a computer-based controller, which can be programmed to perform the treatment method as described herein.

Example 1
Rapid Pad-Steam Cationization and Dyeing of Cotton Fabric

A bleached cotton fabric (A4 size) was dipped in various solutions containing the cationizing agent bis[(3-chloro-2-hydroxypropyldimethylammonium)ethyl]ether dichloride (annotated as bis-CHPDMAEEDC) which is commercially available under the tradename ECOFAST™ Pure; Dow) and sodium hydroxide. Concentrations of bis-CHPDMAEEDC and NaOH base are listed in Table 1.

The solutions were at ambient temperature (20° C.) and the fabric was maintained in the solutions for approximately 2-3 seconds before being removed. The soaked fabric was then passed through two rollers with 70% expression to squeeze the excess solution from the fabric. Accordingly, the effective concentration of the cationizing agent on the fabric was 49 g/L (0.119 molar).

This was followed by steam treatment of the padded fabric at a temperature of 102° C. for varying periods of time (5 min., 10 min., 15 min., 20 min.).

As a control standard, the cationizing agent and base (70 gpl bis-CHPDMAEEDC and gpl NaOH) were padded onto A4 cotton fabric and then left to batch react at a low temperature (25° C.) for a period of 14 hours.

After steam treatment, the cationized fabric was washed in hot water at a temperature of 80° C. for 10 min, then the washed fabric was neutralized in a solution containing acetic acid (1.5 g/L) as per NaOH concentration in ambient condition (temperature 30° C.) for 10 min. After cationization, nitrogen content on the fabric was assessed by the combustion method.

Dyeing was performed by placing 2 gm of the cationized cotton in a dye composition including 3% Reactofix Red ME4BL dye solution and 15 g/L sodium carbonate to improve the fixation and performance properties. The dye solution was at a temperature 60° C. and the fabric was maintained in the solution for 30 min. This was followed by washing process of a cold wash and neutralization, a hot wash at 60° C. for 10 min, and then cold wash. Results of the rapid steam treatments were compared and standardized against a cotton fabric prepared as the controlled standard (Table 1 and FIG. 2).

TABLE 1

Padding

Sodium

Molar Ratio

Results

hydroxide

NaOH:

Nitrogen
Dye Coloration (%

(NaOH)
Cationizing
cationizing

Content on
strength relative to

flakes
agent
agent
Steam Treatment
Fabric
CBP standard)

11 g/L
70 g/L
1.62:1
102° C. for 20 min
0.0765

0.27S molar
0.170 molar

13 g/L
70 g/L
1.91:1
102° C. for 15 min
0.0875
74.60

0.325 molar
0.170 molar

17 g/L
70 g/L
2.5:1
102° C. for 10 min
0.101
72.21

0.425 molar
0.170 molar

28 g/L
70 g/L
4.11:1
102° C. for 5 min
0.11
75.96

0.7 molar
0.170 molar

Surprisingly, the above results showed that using a bis-cationizing agent, a limited amount of base, short steaming times, and a steam temperature near 100° C., there was good staining (as indicated by less residual color in bath), good nitrogen content on cotton, and good color strength.