BINDER COMPOSITIONS FOR MAKING CROSSLINKED CELLULOSE FIBER

Abstract

The present invention provides aqueous compositions for treating fluff pulp comprising (i) one or more acrylic acid polymers containing phosphinate groups and having a weight average molecular weight of from 1,000 to 6,000 and (ii) from 5 to 50 wt. %, based on the total solids weight of the aqueous compositions, of one or more polyethylene glycols, having a formula weight of from 150 to 7,000, or, preferably, from 200 to 600. The present invention also provides individualized, intrafiber crosslinked cellulosic fibers comprising the cellulosic fiber and, in cured form, the aqueous compositions, as well as methods of making the individualized, intrafiber crosslinked cellulosic fibers.

Claims

1. An aqueous composition for treating fluff pulp comprising (i) one or more acrylic acid polymers containing phosphinate groups and having a weight average molecular weight of from 1,000 to 6,000 and (ii) from 5 to 50 wt. %, based on the total solids weight of the aqueous compositions, of one or more polyethylene glycols, having a formula weight of from 150 to 7,000.

2. The aqueous composition as claimed in claim 1, wherein the amount of the (ii) one or more polyethylene glycols ranges from 13 to 40 wt. %, based on the total solids weight of the aqueous compositions.

3. The aqueous composition as claimed in claim 1, wherein the (ii) one or more polyethylene glycols has a formula weight of from 200 to 600.

4. The aqueous composition as claimed in claim 1, wherein the aqueous compositions have a solids content of from 50 to 70 wt. %, based on the total weight of the compositions.

5. The aqueous composition as claimed in claim 1, wherein the (i) one or more acrylic acid polymers have from 2 to 20 wt. % of phosphinate groups taken as the amount of phosphorus acid catalysts used to make the acrylic acid polymers based on the total weight of reactants used to make the acrylic acid polymers.

6. The aqueous composition as claimed in claim 1, wherein the (i) one or more acrylic acid polymers is polyacrylic acid.

7. An individualized, intrafiber crosslinked cellulosic fiber comprising the cellulosic fiber and, in cured form, the aqueous compositions chosen from claim 1 or an aqueous composition of (i) one or more acrylic acid polymers containing phosphinate groups and having a weight average molecular weight of from 1,000 to 6,000 and (ii) from 5 to 50 wt. %, based on the total solids weight of the aqueous compositions, of one or more C1 to C2 alkoxy polyethylene glycols, having a formula weight of from 150 to 7,000.

8. The individualized, intrafiber crosslinked cellulosic fiber as claimed in claim 7, wherein the amount of the aqueous compositions in cured form ranges from 0.5 to 15 wt. %, based on the total dry weight of the untreated cellulosic fibers.

9. A method of using the aqueous compositions as claimed in claim 1 to form individualized, intrafiber crosslinked crosslinked cellulosic fibers comprising contacting with the aqueous compositions a collection of fluff pulp or a sheet thereof to form treated fluff pulp, and, a) in any order, drying, curing and defiberizing the treated fluff pulp to produce individualized, intrafiber crosslinked fibers, preferably, drying, defiberizing and curing or defiberizing, drying and curing.

10. The method as claimed in claim 9, wherein the drying and curing takes place sequentially, in separate steps.

Description

EXAMPLES

[0070] In the following examples, unless otherwise specified, all temperatures are room temperature (20 to 22° C.) and all pressures are standard pressure (1 atm).

[0071] In the following examples, Polymer 1 is polyacrylic acid having a Mw of 2,700 comprising the polymerization product of acrylic acid monomer and from 9 to 11 wt. % sodium hypophosphite monohydrate (SHP), based on the total weight of monomers used to make the polymer. Polymer 1 has a 50 wt. % solids content.

[0072] In the following examples, Polymer 2 is polyacrylic acid having a Mw of 5,000 comprising the polymerization product of acrylic acid monomer and −6 wt. % (SHP), based on the total weight of monomers used to make the polymer. Polymer 2 has a 46 wt. % solids content.

[0073] In the following examples, glycerol is used as a 99 wt. % solids material, dextrose monohydrate is used at 90 wt. % solids, and all polyethylene glycols and methoxy polyethylene glycols are used at 99.9 wt. % solids.

[0074] In the following examples, the term “PEG” refers to polyethylene glycol, the term “MPEG” refers to methyl terminated polyethylene glycol and, unless otherwise indicated, the number following each term refers to the formula weight of the given material.

[0075] The materials in the indicated examples, below, were subject to the following test methods to assess performance:

[0076] Add-on (%):

[0077] The indicated fluff pulp fiber substrate is weighed and then immersed in the indicated aqueous compositions to form treated fluff pulp. The binder soaked substrate is weighed and add-on is calculated from the difference between this weight multiplied by the solids content of the binder and the weight of the original fluff pulp substrate. Then the treated fluff pulp is dried at, unless otherwise stated, 90° C. for 6 minutes.

[0078] 5 k Density (5 k):

[0079] A 4.22 g sample of treated, individualized, and cured fluff pulp fibers is laid by dropping them onto a screen using a vacuum assist to pull fibers onto the screen) onto a 7.62 cm×7.62 cm square. The square is then inserted in a Carver press (Wabash, Ind.) and 200,170 N is applied to the square, which is then immediately released. The sheet is turned 90 degrees, flipped and again 200,170 N is again applied and immediately released. Thickness is measured at the four corners and the center using an Ames bench top comparator (Waltham, Mass.). Each cured fiber sample is trimmed to a 7.62 cm×7.62 cm square which is weighed and then the 5 k density is calculated. Four samples were run for each example tested, and the average of the four results are given in Table 2, below.

[0080] Absorbency Under Load (AUL):

[0081] One end of a glass tube having a length of 15.24 cm, an inner diameter (ID) of 2.49 cm and two open ends is fitted with fritted glass and flared for support. The fitted glass tube is weighed (W0) after being fully submerged in a 0.9% (w/w) NaCl saline solution (Sigma Aldrich, St. Louis, Mo.) in a trough and padded dry to account for water uptake by the fritted glass. In all absorbency tests, roughly 0.5 grams of the indicated cured, treated individualized fluff pulp composition is added into the fitted glass tube which is again weighed (Wi). A disc of glass having an outer diameter that fits inside the fitted tube is inserted into the non-fritted end of the fitted tube so as to apply 19.3 KPa force to the treated, cured and individualized fluff pulp. The saline solution trough is placed on a scale to ensure that the saline level is the same for the start of each individual test; and then the fritted end of the fitted glass tube containing the glass fibers is submerged in the saline solution trough to fully submerge the cured, individualized fluff pulp. The individualized, cured pulp is then allowed to absorb the saline solution for 3 minutes followed by removing the fitted glass tube containing the pulp from the saline and allowing the pulp to dry for 1 minute at room temperature in the fitted glass tube. After this absorption, the disc is removed and the remainder of the filled, fritted tube is weighed (Wf). For each example, absorbency under load is a ratio, calculated as follows:

[00001]$\mathrm{Absorbency}.Math..Math.\mathrm{under}.Math..Math.\mathrm{load}.Math..Math.\left(\frac{g}{g}\right)=\frac{\mathrm{Wf}-\mathrm{Wi}}{\mathrm{Wi}-W.Math..Math.0}$

[0082] The Absorbency under load test was repeated 3 times for each example and the average was reported in Table 2, below.

[0083] L*a*b (Color Space):

[0084] The L*a*b color space was evaluated for a 7.62 cm×7.62 cm square of treated, individualized, and cured fluff pulp fibers as made for the 5 k density test, above, using a Spectro-Guide™ 45/0 from BYK-Gardner (Columbia, Md.) spectrophotometer calibrated as per manufacturer recommendations. Each determination, as reported in Table 2, below, was the mean of 5 measurements per sample (the four corners and a point in the center).

Examples 1 to 11

[0085] In the Examples in Table 1, below, the indicated materials were mixed shaken by hand for 30 seconds then warmed in a 60° C. oven for 1 hour and shaken again by hand for 30 seconds. All of the compositions in Table 1, below, were adjusted to 4.95 wt. % solids in water and then were tested as indicated in Table 2, below. Each aqueous composition in Table 1, below, was applied to Golden Isles™ (Grade 4881) cellulosic fiber mat (Georgia-Pacific Cellulose, LLC Atlanta, Ga.). An approximately 50 gram non-woven sheet of the cellulosic fiber sheet (mat) was immersed in the aqueous compositions indicated in Table 2, below, and then dried at 90° C. for 6 minutes. The sheet was weighed prior to addition of the aqueous compositions and prior to drying to obtain an add-on, this is shown in Table 2, below. The sheets were then mechanically defiberized with a blender in a container that is modified to draw fibers into the blender blades and then past the blender to a collection zone using partial vacuum; and then the individualized fluff pulp was then cured at 200° C. in an oven for 5 minutes to give the individualized, intrafiber crosslinked fibers.

[0086] As shown in Table 2, below, the aqueous compositions of the present invention in Example 3, with acrylic acid polymer and the polyethylene glycol, give fluff pulp a significantly higher bulk (lower density) than Polymer 1 alone in comparative Example 1 and a dramatically higher bulk than an aqueous composition with glycerol in comparative Example 5. In addition, the aqueous compositions of Example 3 give fluff pulp significantly higher absorbency than the acrylic acid polymer alone in comparative Example 1 and dramatically higher absorbency than the compositions with glycerol in comparative Example 5. All of this is so even though the aqueous compositions of the present invention have about a 25 wt. % loading of the PEG 300. Thus, the aqueous compositions of the present invention provide acrylic acid polymer crosslinkers that are more than 33% more efficient than the comparative art.

TABLE-US-00001 TABLE 1 Individualized Intrafiber Crosslinked Fibers from Aqueous Compositions Auxiliary (ii) (g) Crosslinker (i)/ PEG PEG Water Example Amount (g) 300 4k Other dextrose (g)  1* Polymer 1/30 274  2 Polymer 1/35.8 2 365  3 Polymer 1/30 5 370  4 Polymer 1/18.5 5 265  5* Polymer 1/30 5.sup.1 370  6 Polymer 1/30 5 370  7 Polymer 1/30 5.sup.2 370  8 Polymer 2/32.8 5 368  9* Citric Acid/15 288 10* Citric Acid/15 5 382 11* Polymer 1/30 5.5 368 *Denotes Comparative Example; .sup.1Glycerol; .sup.2Methoxy polyethylene glycol formula weight 350).

TABLE-US-00002 TABLE 2 Performance Of The Aqueous Compositions Add- 5k AUL L A B Example on (g/cm.sup.3) (g/g) (color space)  1* 9.3% 0.230 22.92 94.37 −0.04 5.99  2 9.4% 0.228 23.44 94.09 −0.13 5.75  3 9.3% 0.211 23.61 94.92 0.15 4.92  4 9.3% 0.233 22.45 94.61 0.09 6.00  5* 9.4% 0.257 20.86 95.19 0.08 5.11  6 9.3% 0.224 20.85 95.02 −0.05 5.58  7 9.4% 0.218 22.76 94.36 0.12 6.16  8 9.4% 0.244 24.05 94.60 0.06 6.36  9* 9.8% 0.371 18.43 89.70 1.74 15.98 10* 9.8% 0.481 18.42 93.31 0.89 10.54 11* 9.2% 0.283 19.88 87.75 1.91 19.07 *Denotes Comparative Example

[0087] As shown in Table 2, above, the aqueous compositions of the present invention in Examples 2 to 4, and 6 to 8 provide individualized, intrafiber crosslinked fibers with dramatically higher bulk than citric acid or dextrose containing compositions, respectively, in comparative Examples 9, 10, and 11. Further, the aqueous compositions of Examples 2 to 4, 6 and 8, with polyethylene glycols having a range of molecular weights provide enhanced crosslinking efficiency for acrylic acid polymers of varying molecular weight. In each such example, the absorbency under load is as good as, or better than, the same compositions in comparative Examples 1 and 5, with the same acrylic acid polymers at a much higher solids loading; the inventive Examples maintain the absorbency under load with the same acrylic acid polymer but at a polymer concentration of 10% less (compare Example 2 to comparative Example 1), of 25% less (compare Examples 3, 6 and 8 to comparative Example 1), and of over 35% less (compare Example 4 to comparative Example 1). Also shown in Table 2, above, the best results occurred when the polyethylene glycol was present at from 15 to 30 wt. %, based on the solids of the aqueous compositions; further, though the lower molecular weight acrylic acid Polymer 1 gave slightly better results, the higher molecular weight acrylic acid Polymer 2 performed very well and proved that the aqueous compositions of the present invention enable fluff pulp treatment compositions having a much wider range of acrylic acid polymer formulations than previously known at the same level of performance. All inventive compositions provided products having an acceptable, not a darkened, color.