Water-swellable polymer particles

Abstract

The present invention is related to water-swellable polymer particles which contain a hydrophilic base polymer (B) and a hydrophobic polymer (P). It is also related to a process for producing the water-swellable polymer particles, an article containing the water-swellable polymer particles and the use of the water-swellable polymer particles.

Claims

1. Water-swellable polymer particles, comprising i) up to 99.9 wt.-% of a hydrophilic base polymer (B) which is optionally crosslinked, and ii) up to 10.0 wt.-% of a hydrophobic polymer (P), which is a copolymer of up to 95.0 mol-% of at least one (meth)acrylic acid ester and/or (meth)acrylic amide of formula (I) ##STR00014## wherein R.sup.1 is hydrogen or a methyl group, V is OR.sup.2 or NR.sup.3R.sup.4, R.sup.2 and R.sup.3 independently from each other are hydrogen or linear or branched C.sub.1 to C.sub.30 alkyl, and R.sup.4 is hydrogen or linear or branched C.sub.1 to C.sub.30 alkyl, and up to 35.0 mol-% of at least one ethlyenically unsaturated amine-containing monomer, based on an overall weight of the water-swellable polymer particles.

2. The water-swellable polymer particles according to claim 1, wherein the hydrophilic base polymer (B) comprises carboxyl groups, sulfonic acid groups and/or salts thereof and mixtures thereof.

3. The water-swellable polymer particles according to claim 1, which have a particle size d.sub.50 equal to or below 250 μm.

4. The water-swellable polymer particles according to claim 1, wherein the hydrophilic base polymer (B) is a copolymer of i) at least one acid-containing monomer being an ethylenically unsaturated carboxylic acid-containing monomer and/or a sulfonic acid-containing monomer of formula (IIa) and/or formula (IIb) ##STR00015## wherein Y is —O— or —NH—, R.sup.5 is hydrogen or a methyl group, R.sup.6, R.sup.7 and R.sup.8 are independently from each other hydrogen, OH, C.sub.1-C.sub.6-alkyl or C.sub.6-C.sub.14-aryl, n is 0 or 1, M is hydrogen, a metal cation or an ammonium cation and a represents 1 or 1/valency of the metal cation, ##STR00016## ii) optionally at least one amide-containing monomer being a (meth)acrylamide-containing monomer of formula (III) ##STR00017## wherein R.sup.9 is hydrogen or methyl and R.sup.10 and R.sup.11 are independently from each other hydrogen, linear or branched C.sub.1-C.sub.20-alkyl, C.sub.5-C.sub.8-cycloalkyl or C.sub.6-C.sub.14-aryl, or N-Vinylformamide, and iii) optionally a cross-linker.

5. The water-swellable polymer particles according to claim 4, wherein the hydrophilic base polymer (B) comprises a) 10.0 to 70.0 mol-% of the at least one acid-containing monomer, b) 0.0 to 90.0 mol-% of the at least one amide-containing monomer of formula (III), and c) 0.0 to 30.0 mol-% of the cross-linker.

6. The water-swellable polymer particles according to claim 4, wherein the at least one acid-containing monomer is selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chloro sorbic acid, 2′-methylisocrotonic acid, cinnamic acid, p-chlorocinnamic acid, itaconic acid, citraconic acid, mesacronic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), styrenesulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, 2-methylacrylamido-2-methylpropane sulfonic acid, 2-acrylamidobutane sulfonic acid, 3-acrylamido-3-methyl-butane sulfonic acid, 2-acrylamide-2,4,4-trimethylpentane sulfonic acid, 2-sulfoethyl acrylate, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid, a salt thereof, and a mixture thereof.

7. The water-swellable polymer particles according to claim 4, wherein the hydrophilic base polymer (B) comprises the at least one amide-containing monomer, which is selected from the group consisting of (meth)acrylamide, N-methyl(meth)acrylamide, N,N′-dimethyl(meth)acrylamide, N-ethylacrylamide, N,N-diethylacrylamide, N-cyclohexylacrylamide, N-benzylacrylamide, N-tert-butylacrylamide, N-Vinylformamide, and a mixture thereof.

8. The water-swellable polymer particles according to claim 4, wherein the hydrophilic base polymer (B) comprises the cross-linker, which is selected from the group consisting of N,N′-methylenebisacrylamide, N,N′-methylenebi smethacrylamide, hexamethylenebismaleimde, ethylene glycol divinyl ether, triethylene glycol divinyl ether, cylcohexanediol divinyl ether, triallyl amine and/or tetra allyl ammonium salts, tetraallyloxyethane, pentaerythrittriallylether, divinyl benzene, triallyl isocyanurate, ethylene diamine, diethylene triamine, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,3-butyleneglycol diacrylate, 1,3-butyleneglycol dimethacrylate, diethyleneglycol diacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate, ethoxylated bisphenol-A-diacrylate, ethoxylated bisphenol-A-dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentylglycol dimethacrylate, polyethyl eneglycol diacrylate, polyethyleneglycol dimethacrylate, triethyleneglycol diacrylate, tetraethyleneglycol dimethacrylate, dipentaerythritpentaacrylate, pentaerythrittetraacrylate, pentaerythrittriacrylate, trimethylolpropane triacrylate, trimethyl olpropane trimethacrylate, cyclopentadiene diacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, tris(2-hydroxy) isocyanurate trimethylacrylate, divinyl esters of polycarboxylic acids, diallyl esters of polycarboxylic acids, triallyl terephthalate, diallyl maleate, diallyl fumarate, trivinyl trimellitate, divinyl adipate, diallyl succinate, glycidylacrylate, allylglycidether, ethyleneglycol diglycidether, diethyleneglycol diglycidether, polyethyleneglycol diglycidether, polypropyleneglycol diglycidether, polyethyleneglycolmonoallylether acrylate, polyethyleneglycolmonoallylether methacrylate, and a mixture thereof.

9. The water-swellable polymer particles according to claim 1, wherein the hydrophobic polymer (P) is a copolymer of at least two (meth)acrylic acid esters being a first (meth)acrylic acid ester or (meth)acrylic amide of formula (Ia) and a second (meth)acrylic acid ester or (meth)acrylic amide of formula (Ib) ##STR00018## wherein R.sup.12 is hydrogen or a methyl group, W is OR.sup.13 or NR.sup.13R.sup.14 R.sup.13 is a linear or branched C.sub.2 to C.sub.9 alkyl chain, R.sup.14 is hydrogen or a linear or branched C.sub.2 to C.sub.9 alkyl chain, T is OR.sup.16 or NR.sup.16R.sup.17, R.sup.16 is a linear or branched C.sub.10 to C.sub.30 alkyl chain, R.sup.17 is hydrogen or a linear or branched C.sub.10 to C.sub.30 alkyl chain, and at least one ethlyenically unsaturated amine-containing monomer.

10. The water-swellable polymer particles according to claim 9, wherein the first (meth)acrylic acid ester or (meth)acrylic amide of formula (Ia) is selected from the group consisting of ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-methylpentyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate and a mixture thereof, and the second (meth)acrylic acid ester or (meth)acrylic amide of formula (Ib) is selected from the group consisting of stearyl (meth)acrylate, ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, tridecyl (meth)acrylate, 2-propylheptyl (meth)acrylate and a mixture thereof.

11. The water-swellable polymer particles according to claim 1, wherein the at least one ethlyenically unsaturated amine-containing monomer is a (meth)acrylic acid ester or (meth)acrylic amide of formula (IV) ##STR00019## wherein R.sup.18 is hydrogen or a methyl group, X is —O— or —NH—, R.sup.19 and R.sup.20 are independently from each other hydrogen or linear or branched C.sub.1 to C.sub.10 alkyl, and p is in the range of 1 to 10.

12. The water-swellable polymer particles according to claim 1, wherein the at least one ethlyenically unsaturated amine-containing monomer is selected from the group consisting of N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-dimethyl aminoethyl (meth)acrylamide, and a mixture thereof.

13. A process for preparing the water-swellable polymer particles according to claim 1, the process comprising i) providing a suspension comprising the hydrophilic base polymer (B) and a hydrophobic solvent, ii) adding the hydrophobic polymer (P) to the suspension, thereby obtaining the water-swellable polymer particles, and iii) separating the water-swellable polymer particles from the hydrophobic solvent.

14. The process according to claim 13, further comprising, exposing the water-swellable polymer particles obtained in the separating iii) to mechanical force and/or a composition having a pH value of at least 12.

15. An article, comprising the water-swellable polymer particles according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows the primary particle distribution and

(2) FIG. 1b the sample which was treated with then a hydrophobic polymer and afterwards sheared to break up the agglomerates. Not all the agglomerates were broken during the shearing, but most of them were reduced to primary particles.

(3) FIG. 2 shows a particle size analysis of primary particles.

(4) FIG. 3 shows a particle size analysis of primary particles treated with the polymer and sheared before measuring.

(5) The absorption of the superabsorbers should not be negatively influenced by the agglomeration process and this would be shown using the CAC test. The results from these experiments have been presented in Table 4. Clearly, the adsorption and retention of the superabsorbers, both in water and in 1% calcium formate solution was retained.

(6) TABLE-US-00004 TABLE 4 Adsorption and retention capacity of the different examples dest. H.sub.2O Calcium (g/g) formate (g/g) Absorp- Re- Absorp- Re- Example tion tention tion tention M1 242.74 157.44 20.92 13.78 B7 230.01 148.25 21.21 12.77 B8 217.66 147.01 21.56 13.27 B9 214.70 149.42 19.22 11.02