초록 ▼

The present invention relates to a process for the production of water-absorbing polymer structures, comprising the process steps of providing of an aqueous monomer solution comprising a polymerizable, monoethylenically unsaturated monomer (α1) carrying acid groups or a salt thereof; free-radical po

The present invention relates to a process for the production of water-absorbing polymer structures, comprising the process steps of providing of an aqueous monomer solution comprising a polymerizable, monoethylenically unsaturated monomer (α1) carrying acid groups or a salt thereof; free-radical polymerization of the aqueous monomer solution to give a polymer gel, drying of the optionally comminuted polymer gel to give water-absorbing polymer structures, and surface post-crosslinking of the optionally ground and sieved water-absorbing polymer structures, wherein a thermoplastic polymer is added to the aqueous monomer solution before process step ii) or during process step ii), preferably before process step ii), or II) the polymer gel after process step ii) and before process step iv) or during process step iv), preferably before process step iv), or III) the water-absorbing polymer structure after process step iv).

대표청구항 ▼

1. A process for producing water-absorbing polymer structures, comprising the process steps of: i) providing an aqueous monomer solution comprising from 70 to 98.79 wt % of a polymerizable, monoethylenically unsaturated monomer (α1) bearing acid groups, or a salt thereof,from 0.01 to 2.5 wt % of a c

1. A process for producing water-absorbing polymer structures, comprising the process steps of: i) providing an aqueous monomer solution comprising from 70 to 98.79 wt % of a polymerizable, monoethylenically unsaturated monomer (α1) bearing acid groups, or a salt thereof,from 0.01 to 2.5 wt % of a crosslinker (α3), andadding from 0.05 to 5 wt % based on the total weight of the monomer solution of a thermoplastic polymer dispersion having a Brookfield viscosity in a range of from 5 to 3,000 mPa·sec, determined at 20° C., to the aqueous monomer solution and wherein the thermoplastic polymer dispersion is a mixture of the thermoplastic polymer and a dispersion agent wherein these two components do not dissolve in one another,ii) free-radically polymerizing the aqueous monomer solution to obtain a polymer gel,iii) comminuting the polymer gel to form comminuted polymer gel,iv) drying the comminuted polymer gel of step iii) to obtain water-absorbing polymer structures,v) grinding and sieving the water-absorbing polymer structures, andvi) surface postcrosslinking the ground and sieved water-absorbing polymer structures of step v),wherein the thermoplastic polymer dispersion is added to the aqueous monomer solution before process step ii) or during process step ii) and wherein the water-absorbing polymer structures do not contain a silicon oxide compound and wherein the water-absorbing polymer structures have the following properties:(β1) a dust content determined by the test method described herein for the entire particle fraction of not more than 1.0%(β2) a flow value determined by the test method described herein for the entire particle fraction of at most about 15;(β3) a retention, as determined according to ERT 441.2-02, of from about 25 g/g to about 35 g/g;(β4) a Gel Bed Permeability, as determined by the test method described herein, of from about 30 darcy to about 150 darcy wherein the value of the Gel Bed Permeability increases from 74.8 darcy to 113.3 darcy when the amount of thermoplastic polymer dispersion is increased from 0.5 wt % to 1.5 wt %; and(β5) at least 50 wt. % based on the total weight of the post crosslinked water-absorbing polymer structures having a particle size in a range of from 300 to 600 μm. 2. The process as claimed in claim 1, wherein the thermoplastic polymer dispersion is added to the aqueous monomer solution before process step ii). 3. The process as claimed in claim 1 wherein the thermoplastic polymer has a melting temperature or glass transition temperature determined by ISO 11357 within a range from about −100° C. to about 200° C. 4. The process as claimed claim 1 wherein the thermoplastic polymer is used in the form of a dispersion comprising the thermoplastic polymer, a dispersion medium and optionally a dispersant. 5. The process as claimed in claim 4 wherein, when the dispersion is added to the aqueous monomer solution before process step ii), the dispersion is added to the monomer solution in an amount within a range from about 0.05 to about 5% by weight, based on the total weight of the monomer solution. 6. The process as claimed in claim 1 wherein the thermoplastic polymer is a polyacrylate, a (meth)acrylic acid copolymer, an ethylene-(meth)acrylic acid copolymer, a (meth)acrylic ester copolymer, a maleic acid copolymer, a maleic acid-propylene copolymer, a polyurethane, a vinyl acetate copolymer, an ethylene-vinyl acetate copolymer or a vinyl acetate-butyl acrylate copolymer, a styrene copolymer, a butyl acrylate-styrene copolymer, or a polycarbonate. 7. The process as claimed in claim 4 wherein the dispersion medium is water. 8. The process as claimed in claim 4 wherein the amount of thermoplastic polymer in the dispersion is within a range from about 5 to about 95% by weight, based on the total weight of the dispersion. 9. A process for producing water-absorbing polymer structures, comprising the process steps of: i) providing an aqueous monomer solution comprising a polymerizable, monoethylenically unsaturated monomer (α1) bearing acid groups, or a salt thereof,a crosslinker (α3), anda thermoplastic polymer dispersion having a Brookfield viscosity in a range of from 5 to 3,000 mPa·sec, determined at 20° C. and wherein the thermoplastic polymer dispersion is a mixture of the thermoplastic polymer and a dispersion agent wherein these two components do not dissolve in one another;ii) free-radically polymerizing the aqueous monomer solution to obtain a polymer gel,iii) comminuting the polymer gel to form comminuted polymer gel,iv) drying the comminuted polymer gel to obtain water-absorbing polymer structures,v) grinding and sieving the water-absorbing polymer structures, andvi) surface postcrosslinking the ground and sieved water-absorbing polymer structures of step v),wherein the thermoplastic polymer dispersion is added to the aqueous monomer solution before process step ii) or during process step ii) and wherein the water-absorbing polymer structures do not contain a silicon oxide compound and wherein the water-absorbing polymer structures have the following properties:(β1) a dust content determined by the test method described herein for the entire particle fraction of not more than 1.0%;(β2) a flow value determined by the test method described herein for the entire particle fraction of at most about 15;(β3) a retention as determined according to ERT 441.2-02 of from about 25 g/g to about 35 g/g; and(β4) a Gel Bed Permeability determined by the test method described herein of from about 30 darcy to about 150 darcy wherein the value of the Gel Bed Permeability increases from 74.8 darcy to 113.3 darcy when the amount of thermoplastic polymer dispersion is increased from 0.5 wt % to 1.5 wt %.