Process for the continuous preparation of water-absorbent polymers

Patent metadata

Field	Value
Publication number	US-9255190-B2
Application number	US-201214364525-A
Country	US
Kind code	B2
Filing date	Dec 14, 2012
Priority date	Jan 12, 2012
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

The invention relates generally to a process for the preparation of water-absorbent polymer particles, including the process steps of preparing particulate water-absorbent polymer and mixing the particulate water-absorbent polymer with an aqueous crosslinker solution and heat-treating the mixture of particulate water-absorbent polymer in a horizontally operated mixing device, wherein the horizontally operated mixing device is hydraulically driven. The invention also relates to water-absorbent polymer particles obtainable by such a process.

First claim

The invention claimed is:

1. A process for the preparation of water-absorbent polymer particles, comprising the process steps of
preparing an aqueous monomer solution comprising at least partially neutralized, monoethylenically unsaturated monomers bearing carboxylic acid groups (α1) and at least one crosslinker (α3);
adding a polymerization initiator or a at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution;
decreasing the oxygen content of the aqueous monomer solution;
charging the aqueous monomer solution into a polymerization reactor;
polymerizing the monomers in the aqueous monomer solution in the polymerization reactor to form a polymer gel;
discharging the polymer gel out of the polymerization reactor and comminuting the polymer gel thereby obtaining polymer gel particles;
drying the polymer gel particles;
grinding the dried polymer gel particles thereby obtaining particulate water-absorbent polymer particles;
sizing the grinded water-absorbent polymer particles; and
step (xi) crosslinking the surface of the grinded and sized water-absorbent polymer particles;
wherein process step (xi) comprises the steps of:
(x1a) mixing the water-absorbent polymer particles with an aqueous crosslinker solution; and
(x2a) heat-treating the mixture obtained in process step (x1a) in a horizontally operated mixing device,
wherein the horizontally operated mixing device is hydraulically driven.

2. The process according to claim 1 , wherein mixture obtained in process step (x1a) is heat-treated at a temperature in the range from 150 to 250° C. in the horizontally operated mixing device.

3. The process according to claim 1 , wherein the horizontally operated mixing device comprises at least one rotating shaft and a hydraulic motor that converts hydraulic pressure and flow into torque and angular displacement, thereby forcing the shaft into rotation.

4. The process according to claim 3 , wherein at least two paddles are provided on the rotating shafts.

5. The process according to claim 3 , wherein an oil is used as the hydraulic liquid used in the hydraulic motor.

6. The process according to claim 1 , wherein the average residence time of the water-absorbent polymer particles in the horizontally operated mixing device is in the range from 5 to 500 minutes.

7. The process according to claim 3 , wherein the rotation speed of the shaft in the horizontally operated mixing device is in the range from 5 to 25 rpm.

Assignees

• Plochinger Harald
• Fricker Daniel
• Walther Richard
• Hager Marc
• Evonik Industries Ag

Inventors

• Plochinger Harald
• Fricker Daniel
• Walther Richard
• Hager Marc

Classifications

• A61L15/22 Primary

  containing macromolecular materials · CPC title

• C08J3/24 Primary

  Crosslinking, e.g. vulcanising, of macromolecules (mechanical aspects B29C35/00; crosslinking agents C08K) · CPC title

• B01J19/20

  in the form of helices, e.g. screw reactors · CPC title

• C08J3/245

  Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking · CPC title

• A61L15/60

  Liquid-swellable gel-forming materials, e.g. super-absorbents · CPC title