In an embodiment according to the present invention, the softener emulsion is treated with ultrasonic energy for a period of 1 to 60 min, preferably 10 to 30 min. Treating the softener emulsion for the preferred time reduces the viscosity of the softener emulsion to the preferred level.

According to the present invention, the softener emulsion may be added to fiber slurry at the wet end of the paper machine, and/or a softener emulsion may be applied on the wet fiber web or at the dry sheet or converted roll.

Emulsion may be applied on the wet fiber web and/or on the dry sheet by spraying or any other suitable method.

In an embodiment, the softener emulsion may be added to fiber slurry at wet end of paper, tissue or board machine. The fiber slurry may comprise bleached and/or unbleached fibers comprising virgin fibres and/or recycled fibers from fiber sources selected from hardwood (HW), such as eucalyptus, aspen and birch, softwood (SW), such as spruce, pine, fir, larch and/or hemlock, non-wood fibres such as bamboo, cotton, hemp and/or linen, or any combination thereof.

According to an embodiment of the present invention, the emulsion may be diluted for wet end application. A diluted softener emulsion may comprise 0.01 to 10 wt-% softener concentrate, and 90 to 99.9 wt-% water, preferably the diluted softener emulsion comprises 0.01 to 5 wt-% softener concentrate and 95 to 99.9 wt-% water, of the total weight of the softener emulsion. In an especially preferred embodiment, the diluted softener emulsion comprises 1 wt-% softener concentrate and 99% water, of the total weight of the diluted softener emulsion. According to an embodiment of the present invention, dosage of the softener emulsion may be from 1.5 to 20 kg/t (3 to 40 lb/ton) of dry pulp, preferably from 1.5 to 6 kg/t (3 to 12 lb/ton) of dry pulp, as weight of the softener concentrate.

In an embodiment of the present invention, the softener emulsion may be applied at the wet fiber web. The softener emulsion is typically applied by spraying. The web may have a moisture content of 30 to 90%, as weight percentage of water in the wet fiber web. According to an embodiment of the present invention, dosage of the softener emulsion may be from 1.5 to 20 kg/t (3 to 40 lb/ton) of dry pulp, preferably from 1.5 to 6 kg/t (3 to 12 lb/ton) of dry pulp, as weight of the softener concentrate.

In an embodiment of the present invention, the softener emulsion may be applied at the dry sheet or converted roll. The dry sheet or converted roll may have a moisture content of less than 12%, as weight percentage of water in the dry sheet or converted roll. According to an embodiment of the present invention, dosage of the softener emulsion may be from 1.5 to 20 kg/t (3 to 40 lb/ton) of dry pulp, preferably from 1.5 to 6 kg/t (3 to 12 lb/ton) of dry pulp, as weight of the softener concentrate.

In the present disclosure, t refers to a tonne (1000 kg), whereas ton refers to a short ton (2000 lb).

Spraying softeners onto dry sheet requires a low viscosity fluid to achieve a uniform spray pattern. For instance, one of the industrial standard equipment, i.e., WEKO fluid application system, prefers the viscosity of the softener emulsion even lower than 100 cPs. Although the softener emulsion can be reduced in viscosity right after manufacturing, the viscosity might increase during transportation or storage at an elevated temperature or a cold temperature, because the particles are prone to aggregation. Therefore, an on-site process to reduce the emulsion viscosity and maintain the low emulsion viscosity is desired.

FIG. 1 depicts a novel process which uses either a high shear homogenizer equipment or an ultrasound unit with or without adding electrolytes to achieve the low viscosity. The softener emulsion may be stored at a storage tank 1.

The softener emulsion is pumped through a high shear equipment or an ultrasonic equipment in unit 2. The high shear homogenizer can be any high-speed machine offering homogenization, emulsification, or disintegration, such as a homogenizer, a colloid mill, or an emulsifier. The desired amount of electrolytes can be added (A) on the top of the storage tank 1 or (B) the inlet of the discharge pump of the storage tank 1. The softener emulsion can be recirculated (C) to the storage tank 1 until the viscosity of emulsion reaches the target range. Subsequently, the emulsion may be supplied to dry sheet spray system 3.

The present invention further provides a use of the softener emulsion to increase the bulk and softness of textile products. Comprising a cationic surfactant, the softener emulsion according to the present invention adheres well to natural fibers such as wool and cotton. The softener emulsion according to the present invention provides a bio-based alternative to synthetic textile softeners.

The present invention further provides a use of the softener emulsion as a debonding agent to produce fluff pulp. Fluff pulp is used in e.g. infant diapers, feminine hygiene products and sanitary napkins. A fluff pulp product is typically converted from a sheeted form to individual fibers. The pulp is typically treated with a debonding agent at the wet end which can interfere with the formation of hydrogen bonding between fibers during drying. The softener emulsion according to the present invention is well suitable as a debonding agent, providing defibering of the pulp through control of inter-fiber hydrogen bonds.

The present invention further provides a use of the softener emulsion as a releasing agent in the manufacture of paper and paperboard. The softener emulsion according to the present invention may provide a bio-based alternative to conventional releasing agents having a good releasing performance.

The present invention further provides a use of the softener emulsion as a bulking agent for tissue, paper, and paperboard products. A bulking agent increases the pore volume of a tissue, paper or paperboard product, resulting in an increase of sheet thickness. The softener emulsion according to the present invention may provide a bio-based alternative to conventional bulking agents.

The present invention further provides a use of the softener emulsion as a fluting agent for linerboard applications.

EXPERIMENTS
Experiment 1. Handsheet Preparation for Wet End Application of Softener

Two different fiber blends were used in this evaluation, i.e., 50:50 and 70:30 eucalyptus to softwood ratio. The eucalyptus pulp was re-slushed with Valley beater without refining. Lab softwood was refined to around 500 CSF (Canadian Standard Freeness) and blended with eucalyptus at the target ratio. The fiber blends were diluted with synthetic water treated with 35 ppm of Ca²⁺ and 150 ppm of SO₄²⁻ separately to about 0.45%. The pH of the furnish was approximately 7.0.

Chemicals were mixed with fiber slurry for 45 seconds before making handsheet. The softener emulsion was diluted to 1 wt-% in softener concentrate concentration of the total weight of the diluted softener emulsion, and then dosed to the thin furnish at 3 and 6 kg/t of dry pulp (6 and 12 lb/ton of dry pulp), as weight of softener concentrate. A commercial coagulant (FennoFix 501, Kemira Oyj) was used in some examples.

Handsheets (target to about 35 g/m²) were prepared according to the standard handsheet protocol by Dynamic Sheet Former (DSF) from Techpap. Sheets were drum-dried (set at 115° C. for 60-second total drying time) with a backing blotter paper without wet press.

Experiment 2. Handsheet Preparation for Wet Web Spray of Softener Emulsion

The thin furnish was prepared similarly than in Experiment 1. Two blank conditions were included in the wet web study. No chemicals were added in wet end. Handsheets (target to about 35 g/m²) were prepared according to the standard handsheet protocol by Dynamic Sheet Former (DSF) from Techpap. After making the handsheet, the master sheet was cut into 3 pieces with a width of 23 cm (9 inch). Each single sheet was sprayed using 1550 AutoJet Modelar Spray System with Phoenix I single axis Servo controller. The dosages of softener were 3 and 6 kg/t of dry pulp (6 and 12 lb/ton of dry pulp). The sheet was then sandwiched by two blotter papers and drum-dried (set at 115° C. for 60-second total drying time) without wet press.

Experiment 3. Dry Sheet Spray of Softener Emulsion

The sheet used for dry sheet spray was a commercial bath tissue base sheet obtained from a tissue paper mill. The basis weight of the base sheet was approximately 20 g/m². The spraying system is 1550 AutoJet Modular Spray System with Phoenix I single axis Servo controller. The 30% softener emulsion was used for this study. Add-on rate was estimated by the sheet weight difference pre- and post-spray then divided by the sheet weight. After spraying, the sheet was dried using a heat press set at 121° C. (250° F.) for 60 s without press.

Experiment 4. Paper Sample Handling and Preparation

The handsheet samples and the tissue base sheets were conditioned at 23° C. and 50% relative humidity for at least 24 hours, per TAPPI 402, prior to testing. Special care was taken to avoid impacting the sheet structure. The areas closed to the edges of the sheet were avoided during testing. Wrinkled area from the commercial base sheet were avoided if possible.

Experiment 5. Caliper

Sheet caliper was measured using a Thwing Albert ProGage thickness tester, using 35.7 mm diameter foot with 2.0 kPa of pressure. This procedure references TAPPI Test Method T580 pm-12 “Thickness of towel, tissue, napkin and facial products”. The sample was measured with the tissue stacked in 8 plies for commercial base sheet and single ply was used for handsheet sample. Six replicates and eight replicates per condition for handsheet and commercial base sheet respectively were taken, and the average value being reported. Bulk value is calculated by using average caliper divided by average grammage.

Experiment 6. Grammage

The handsheet sample was cut with a 112.8 mm diameter circular punch cutter as single ply and then weighed on an analytical balance. For the commercial base sheet, eight plies were cut using the cutter. The grammage was calculated based on area and is reported in g/m²per sheet.

Experiment 7. Tensile Strength, Dry

Tensile strength is measured by applying a constant rate-of-elongation to a sample and recording three tensile breaking properties of paper and paper board: the force per unit width required to break a specimen (tensile strength), the percentage elongation at break (stretch) and the energy absorbed per unit area of the specimen before breaking (tensile energy absorption). This method is applicable to all types of paper, but not to corrugated board. This procedure references TAPPI Test Method T494. A minimum of twelve measurements were taken per condition for handsheet sample and 16 measurements for commercial base sheet. The testing gap was set for 5 cm (2 inches). Handsheet sample were tested with single ply and commercial samples were tested with four plies. A Thwing-Albert QC 3A tensile tester with was used.

Experiment 8. Tissue Softness Analyzer (TSA)

Tissue softness was analyzed using the Emtec TSA Tissue Softness Analyzer. The TSA measures softness indicated by HF (hand feel), the TS7 value (correlates to real softness), TS750 (correlating to felt smoothness) and D value (correlates to stiffness). Hand feel (HF) is a combination parameter and has no units attached to the data value. Because the handsheet samples have no creping, no HF results was reported for lab handsheets. TS7 and TS750 are the peak heights (in dB V2 rms) recorded at 7000 and 750 Hz, respectively. The D value is the distance that the tissue is displaced by the impeller during the testing as the impeller presses against the sample, and is expressed in mm/N.

The TSA functions by clamping a tissue sample in the sample ring and measuring acoustic values as the surface of the tissue is brushed with a rotating wheel. The handsheet samples were run using the “research” algorithm, with the dryer side analyzed. No HF results were reported. Commercial base sheet samples used TPII algorithm. Table 1 below explains the four parameters and how to interpret the data.

TABLE 1

TSA Parameter and Data Interpretation

Parameter
Correlation
How to Interpret

HF
Combination parameter for
Higher = better

hand feel

TS7
Real softness (from fibers)
Lower = softer

TS750
Felt smoothness/roughness
Higher peak = higher roughness

D
Stiffness
Lower = stiffer

Experiment 9. Bulk Viscosity of Emulsion

Viscosity is the resistance of a fluid to being deformed by shear or extensional stress. Bulk viscosity (BV) is a measurement of fluid as-is. A Brookfield Viscometer, DV2T, with #63 spindle and spindle rotation speed at 30 rpm is used for this study. A rotation speed of 20 rpm is used if the viscosity is higher than 4000 cPs. All viscosities were measured at ambient temperature.

Experiment 10. Particle Size Analysis

Emulsion sample is analyzed for particle size with a Horiba Laser Scattering Particle Size Distribution Analyzer, model LA-300. The sample is diluted using deionized water. The RR index is 1.1-0.00i. The median particle sizes, the mean particle sizes, and standard deviations of the distributions are reported in micrometers (μm).

Experiment 11. Viscosity Reduction by Hand Homogenizer

A hand homogenizer is used to treat emulsion. A certain amount of emulsion (e.g., 300 ml) is added into the cup of the hand homogenizer and then the emulsion is pressed through a small orifice.

Experiment 12. Viscosity Reduction by Ultrasonic Cleaning Bath

A conventional ultrasonic cleaning bath (Aquasonic Model 250T, 50/60 Hz Amps: 4) is used to treat the emulsion. Typically, 400 ml emulsion is filled in a glass jar and then put in the ultrasonic cleaning bath. The ultrasonic cleaning bath is turned on and treats the emulsion over a certain period until the emulsion viscosity reaches the target value, i.e., approximately 100 cPs.

Experiment 13. ORP Measurement of Emulsion

Oxidation-reduction potential (ORP) measurement indicates how oxidizing or reducing a liquid is. In this study, an Oakton ORP tester is used for the ORP measurement of the emulsion. The probe is placed into the emulsion and the ORP value is taken until the reading is stable.

EXAMPLES

A commercial softener product FennoSoft 868NV, an imidazoline-based softener from Kemira Oyj, was evaluated as the control in some of the examples shown below.

Example 1: Preparation of the Softener Emulsion

The softener concentrate was prepared prior to emulsification. Table 2 presents the composition of this formulation.

TABLE 2

The softener composition prior to emulsification.

Soy

Surfactant Blend

Lanolin,
Lecithin,
Imidazoline,
(sorbitan:polysorbate

wt-%
wt-%
wt-%
ester 2:1), wt-%

Softener
5.0
10.0
5.0
80.0

concentrate

A typical lab procedure of the preparation of a 350.0 g softener emulsion with 30% softener concentrate content according to the present invention is shown below.

- I. Add 56.00 g sorbitan monooleate into a 500 ml stainless steel beaker.
- II. Add 28.00 g polysorbate-20 into the beaker.
- III. Add 10.50 g lecithin into the beaker.
- IV. Add 5.25 g imidazoline into the beaker.
- V. Add 5.25 g USP lanolin into the beaker.
- VI. Place the beaker on the hot plate with temperature set at 100° C.
- VII. Manually mix the blend until the lanolin melts and the blend is homogeneous. The temperature should not be below 40° C.
- VIII. Place the beaker on the platform for homogenizer IKA T50.
- IX. Start the homogenizer at low speed (i.e., 1000 rpm).
- X. Add the 245.00 g warm tap water (~35° C.) into the beaker.
- XI. Increase the speed to 2600 rpm and mix for 1 minute.
- XII. Stop the homogenizer and transfer the emulsion to a jar for storage.

The composition of final emulsion according to the present invention with 30% solids content is shown below:

- 1.5 wt-% lanolin (USP)
- 3.0 wt-% non-GMO soy lecithin
- 1.5 wt-% imidazoline
- 16.0 wt-% sorbitan monooleate
- 8.0 wt-% polysorbate-20 (Polyethylene glycol sorbitan monolaurate)
- 70.0 wt-% water

The imidazoline is produced by the reaction of a fatty acid with diethylenetriamine, and then cyclized, and finally quaternized by diethyl sulfate. The fatty acid is preferred to be oleic acid or palmitic. The oleic acid to DETA ratio is preferred in the range of 1 to 2. The cyclization reaction is preferably completed to a degree of 80 to 95%, and the quaternization reaction is preferably completed to a degree of 90 to 95%.

Example 2: Dry Sheet Spray

The results of dry sheet spray are presented in FIGS. 2 to 6. 868NV refers to 20% solids emulsion of the commercial control FennoSoft 868NV. 695-71A is a softener emulsion according to the present invention with 30 wt-% softener concentrate content. In FIG. 2, both emulsions decreased dry tensile (DT) by almost 30%. HF values shown in FIG. 3 were increased by 8% by these two emulsions. Both emulsions reduced TS7 (FIG. 4) and TS 750 (FIG. 5). D value was increased by dry sheet spray (FIG. 6). No significant differences of TSA testing results were observed between 695-71A and 868NV.

TABLE 3

Softener composition and dosage for Example 2.

Dosage,

Lanolin,
Lecithin.
Imidazoline
Surfactant
kg/t

Softener
wt-%
wt-%
wt-%
blend
(lb/ton)

695-71A
5
10
5
SMO-
9 (18)

K/PSML-

20LC 2:1

868NV
0
0
7
400DO
5.6 (11.1)

Blank - Air
0
0
0
NA
0

TABLE 4

Softness measurement values for Example 2.

TS7,
TS 750,
D,
DT,

Softener
HF
dB
dB
mm/N
gf/3 in

695-71A
91.7
11.520
11.157
3.89
177

868NV
91.3
11.731
11.540
3.94
173

Blank - Air
84.5
15.343
13.113
3.67
250

Example 3: Wet Web Spray

There are two blank conditions including 50:50 eucalyptus:softwood (SW) and 70:30 eucalyptus:SW in the wet web study. Due to the higher eucalyptus content, 70:30 eucalyptus gives better softness than 50:50 eucalyptus. The wet web spray of softener tested was applied only on 50:50 eucalyptus to softwood blend. The purpose to use 70:30 eucalyptus:SW as target is to 15 evaluate if softener treatment is able to provide 20% fiber substitution of eucalyptus. FIG. 7 displays the dry tensile results. A dosage response of softener to dry tensile can be observed for 695-71A, a softener emulsion according to the present invention. In addition, 695-71A gave significant higher bulk than 50:50 eucalyptus:SW blank shown in FIG. 8. TSA results are shown in FIGS. 9 and 10. 695-71A reduced TS7 and increased D value. At a dosage of 6 kg/t of dry pulp (12 lb/ton of dry pulp), as weight of the softener concentrate, 695-71A yielded slightly better softness results than 70:30 eucalyptus:SW blend.

TABLE 5

Dosage, dry tensile, bulk, and softness values for Example 3.

Normalized

Dosage, kg/t
CD DT,
Bulk.
TS7,
TS 750,
D,

Softener
(lb/ton)
kN/m (lb/in)
cm³/g
dB
dB
mm/N

50:50 Euc/SW
0
0.588 (3.36)
3.66
80.960
52.914
0.81

70:30 Euc/SW
0
0.406 (2.32)
3.83
60.978
43.790
0.85

695-71A
3 (6)
0.450 (2.57)
3.71
65.293
45.707
0.84

695-71A
6 (12)
0.343 (1.96)
3.81
54.087
43.459
0.87

Example 4: Wet End Application

The strength and softness results in terms of wet end application of softener are shown in FIG. 11 to FIG. 15. In these figures, the blank 1 is the 50:50 eucalyptus to softwood fiber blend, and blank 2 is the 70:30 eucalyptus to softwood fiber blend. Both blanks did not use any chemical additions. All chemical treatments are used only on 50:50 eucalyptus to softwood blend. The softness target is blank 2. Blank 2 gives better softness than blank 1 due to higher eucalyptus content. The purpose to use blank 2 as target is to evaluate if softener treatment is able to provide 20% fiber substitution of eucalyptus.

695-71A, the softener emulsion according to the present invention, did not decrease dry tensile when it was used alone (FIG. 11). It is reasonable because most of the components in this formulation is nonionic. When it was used with the commercial coagulant FennoFix 501 (Kemira Oyj), 695-71A showed dry tensile decrease at a dosage of 6 kg/t of dry pulp (12 lb/ton of dry pulp), as weight of the softener concentrate. As of bulking performance (