Highly swellable polymers

Patent metadata

Field	Value
Publication number	US-9920151-B2
Application number	US-201214354356-A
Country	US
Kind code	B2
Filing date	Oct 26, 2012
Priority date	Oct 28, 2011
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The present invention relates to a method for producing polymers that are suitable for absorbing and storing aqueous liquids, and to polymers that can be obtained by this method. This invention further related to the use of such polymers. The method comprises the following steps:
i. crosslinking free-radical polymerization of a monomer composition M comprising
a) at least one monomer A having an ethylenic double bond and at least one neutralizable acid group or a group hydrolyzable to a neutralizable acid group, b) optionally one or more comonomers B which are different than the monomers A and have one ethylenic double bond, and c) 0.05 to 10% by weight, based on the total amount of monomers A and B, of at least one crosslinker C, in the presence of at least one polysaccharide-comprising substance S, in an aqueous liquid, where the weight ratio of the monomer composition M to the substance S is in the range from 9:1 to 1:9; and
ii. at least partial neutralization of the acid groups and/or hydrolysis of the groups hydrolyzable to neutralizable acid groups in the polymer obtained in step i.;

wherein the polymerization and/or the neutralization is performed in the presence of urea.

First claim

The invention claimed is:

1. A process for preparing polymers suitable for absorbing and storing aqueous liquids, comprising:
i. crosslinking free-radical polymerization of a monomer composition M comprising
a) at least one monomer A selected from monoethylenically unsaturated C 3 -C 8 -monocarboxylic acids, mixtures thereof and mixtures of at least one monoethylenically unsaturated C 3 -C 8 -monocarboxylic acid with one or more monoethylenically unsaturated C 4 -C 8 -dicarboxylic acids,
b) optionally one or more comonomers B which are different than the monomers A and have one ethylenic double bond, and
c) 0.05 to 10% by weight, based on the total amount of monomers A and B, of at least one crosslinker C,
in the presence of at least one finely divided particulate cellulose material S comprising bound lignin, in an aqueous liquid, where the weight ratio of the monomer composition M to the substance S is in the range from 8:2 to 2:8; and

ii. at least partial neutralization of the acid groups in the polymer obtained in step i.;
wherein the polymerization and/or the neutralization is performed in the presence of urea and at least 90% by weight of the particles of the particulate cellulose material have dimensions in the range from 1 μm to <500 μm, determined by sieve analysis,
wherein the amount of urea is from 5 to 60% by weight, based on the total amount of the monomer composition M and substance S, and
wherein the polymerization is performed at a pH range from 1-4.

2. The process according to claim 1 , wherein the polymer obtained in step i. is treated with urea before or during the neutralization in step ii.

3. The process according to claim 1 , wherein the total amount of urea is 1 to 20% by weight, based on the total amount of monomer composition M, substance S and aqueous liquid.

4. The process according to claim 1 , wherein the cellulose material is selected to an extent of at least 50% by weight, based on the total amount of substance S, from hemp dust, flax dust, sawdust, ground straw, ground olive stones, ground tree bark, reject material from pulp production, sugar beet peel, sugar cane waste, rice husks, cereal husks, and ground hemp fibers, ground flax fibers, ground Chinese silvergrass fibers, ground coconut fibers, ground kenaf fibers and ground wood fibers.

5. The process according to claim 1 , wherein at least 90% by weight of the particles of the particulate cellulose material have dimensions in the range from 5 to <300 μm, determined by sieve analysis.

6. The process according to claim 1 , wherein the monomers A account for at least 50% by weight, based on the total amount of monomers in the monomer composition.

7. The process according to claim 1 , wherein the monomers A comprise at least 50% by weight, based on the total amount of monomers A, of acrylic acid.

8. The process according to claim 1 , wherein the crosslinkers C are selected from ethylenically unsaturated monomers having at least 2 ethylenically unsaturated double bonds.

9. The process according to claim 1 , wherein the polymerization is performed under oxygen-comprising atmosphere.

10. The process according to claim 1 , wherein a viscosity of the reaction mixture, determined to DIN EN 2555-2000 by means of a Brookfield viscometer at 23° C. at a shear rate of <10 sec −1 , in the range from 10 to 1000 mPa·s is established at the start of the polymerization.

11. The process according to claim 1 , wherein the neutralization is followed by separation of the polymer from the aqueous liquid and drying.

Assignees

• Basf Se

Inventors

• Diamantoglou Michael
• Hartmann Christoph

Classifications

• C05G3/80

  Soil conditioners · CPC title

• C05G5/40

  Fertilisers incorporated into a matrix · CPC title

• C09K17/18

  Prepolymers; Macromolecular compounds · CPC title

• B01J2220/68

  Superabsorbents · CPC title

• B01J20/267

  Cross-linked polymers · CPC title