Water-absorbing polymer structures with improved absorption properties

• US 8,071,202 B2
• Filed: 04/21/2006
• Issued: 12/06/2011
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Evonik Superabsorber GmbH
• Original Assignee: Evonik Stockhausen GmbH (Evonik Degussa GmbH)
• Inventors: Furno, Franck, Schmidt, Harald, Nielinger, Ursula, Keup, Michael, Herbe, Peter
• Primary Examiner(s): Sample, David
• Assistant Examiner(s): Ferguson, Lawrence
• Application Number:
  US11/912,011
• Publication Number:
  US 20090202805A1
• Time in Patent Office: 2,055 Days
• Field of Search: 428/212, 428/219, 428/220, 525/474
• US Class Current: 428/212
• CPC Class Codes: A61L 15/18 containing inorganic materials
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: B01J 20/26 Synthetic macromolecular compounds
• CPC Class Codes: B01J 2220/68 Superabsorbents
• CPC Class Codes: C08F 222/102 of dialcohols, e.g. ethylene glycol di(meth)acrylate or 1,4-butanediol dimethacrylate
• CPC Class Codes: C08J 7/12 Chemical modification
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree

Abstract

The present invention relates to a process for production of water-absorbing polymer structures comprising the process steps of providing an untreated, water-absorbing polymer structure (Pu) with a retention of at least about 35 g/g; and bringing this water-absorbing untreated polymer structure (Pu) into contact with a permeability-increasing agent. The invention further relates to the water-absorbing polymer structures obtainable by this process, water-absorbing polymer structures, a composite, a process for production of a composite, a composite obtainable by this process, chemical products comprising water-absorbing polymer structures or a composite as well as the use of water-absorbing polymer structures or of the composite in chemical products.

Claims

1. A water-absorbing polymer structure comprising:

from about 0.001 wt % to about 10 wt % of a compound selected from a SiO compound or a trivalent cation or a combination of the SiO compound and trivalent cation;

wherein said water-absorbing polymer structure has the following properties;

a a retention determined according to the herein-described test method of at least 32 g/g; and

b a Time-dependent Absorption Against a Pressure (TAAP at 0.3 psi) determined according to the test method described herein of 20 g/cm², (TAAP;

Time-dependent Absorption Against Pressure at 0.3 psi) selected from the group consisting of;

b1 50% of the maximum absorption of the polymer structure within about 20 minutes and

b2 90% of the maximum absorption of the polymer structure within about 40 minutes.

2. A composite comprising a water-absorbing polymer structure, which was produced according to a process, comprising the process steps of:

I providing an untreated water-absorbing polymer structure (Pu) with a retention determined according to the test method described herein of at least about 37.5 g/g; and

II bringing into contact of this water-absorbing, untreated polymer structure (Pu) with a permeability-increasing agent or a water-absorbing polymer structure according to claim 1, a substrate and if necessary an additive, wherein the composite comprises at least one region which comprises the water-absorbing polymer structure in an amount from about 30 to about 100 wt. %, based on the total weight of the relevant regions;

wherein said permeability-increasing agent comprises from about 0.001 wt % to about 10 wt % of a compound selected from a SiO compound or a trivalent cation or a combination of the SiO compound and trivalent cation.

3. The composite according to claim 2, wherein the composite is an absorbent layer.

4. The composite according to claim 3, having at least one of the properties:

(δ

1) a Rewet value of at most about 3 g after the third wetting;

(δ

2) an Acquisition Time after the second wetting of at most about 450 s;

(δ

3) an Acquisition Time after the third wetting of at most about 1500 s.

5. The composite according to claim 2, wherein the composite has a mass per unit area of at least about 0.02 g/cm².

6. The composite according to claim 2, wherein the composite has a thickness of maximum about 20 mm.

7. A process for the production of a composite according to claim 2, wherein the water-absorbing polymer structure and the substrate, and optionally the additive are brought into contact with each other.

11. The process according to claim 1, wherein the SiO compound which was obtained by polycondensation of monoorthosilicic acid.

12. The process according to claim 4, wherein the SiO compound is a silica sol.

13. The process according to claim 1, wherein the trivalent cation is an Al³⁺ ion.

14. The process according to claim 6, wherein the salt is selected from AlCl₃×

6 H₂O, NaAl(SO₄)₂×

12 H₂O, KAl(SO₄)₂×

12 H₂O or Al₂(SO₄)₃×

14-18 H₂O.

15. The process according to claim 1, wherein the water-absorbing polymer structures are post-crosslinked before, during or after process step II.

16. A water-absorbing polymer structure obtainable by a process according to claim 1.

8. A water-absorbing polymer comprising,

a) an untreated water-absorbing polymer structure (Pu) having a retention determined according to the test method “

Determination of the Retention”

described herein from about 40 to about 50 g/g; and

b) a permeability-increasing agent located on the surface of the untreated water-absorbing polymer structure

wherein the water-absorbing polymer further comprises

from about 0.001 wt % to about 10 wt % of a compound selected from a SiO compound or a trivalent cation or a combination of the SiO compound and trivalent cation,

wherein the foregoing compound is immobilized on the surface of the water-absorbing polymer.

9. The water-absorbing polymer structure according to claim 8, having an Absorption against a Pressure of 0.7 psi (50 g/cm²) determined according to ERT 442.2-02 of at least about 10 g/g.

10. A process for the production of water-absorbing polymer structures, comprising the following steps:

I providing an untreated water-absorbing polymer structure (Pu) having a retention determined according to the test method “

Determination of the Retention”

described herein from about 40 to about 50 g/g; and

II bringing into contact of the water-absorbing, untreated polymer structure (Pu) with from about 0.00 wt % to about 10 wt % of a compound selected from a SiO compound or a trivalent cation or a combination of the SiO compound and trivalent cation;

wherein said water-absorbing polymer structure has the following properties;

a a retention determined according to the herein-described test method of at least 32 g/g; and

b a Time-dependent Absorption Against a Pressure (TAAP at 0.3 psi) determined according to the test method described herein of 20 g/cm², (TAAP;

Time-dependent Absorption Against Pressure at 0.3 psi) selected from the group consisting of;

b1 50% of the maximum absorption of the polymer structure within about 20 minutes and

b2 90 % of the maximum absorption of the polymer structure within about 40 minutes.