Water-absorbing polymer structure having improved permeability and absorption under pressure

1. A process for the preparation of a water-absorbing polymer structure, comprising the following process steps:

i) providing an untreated, water-absorbing polymer structure; and

ii) bringing the untreated, water-absorbing polymer structure into contact with from about 0.1 to about 5 wt % based on the weight of the untreated, water-absorbing polymer structure, of a salt comprising at least about 50 wt % of the salt, of aluminum lactate, and

of which more than about 80% by weight, relative to the water-absorbing polymer structure, are based on acrylic acid, of which in a range of from about 50 to about 85 mol % are neutralized, the water-absorbing polymer structure having the following properties:

A1 a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 10×10 7 cm 3 s/g to about 180×10 7 cm 3 s/g;

B1 a retention (CRC) determined according to ERT 441.2-02 of at least about 25 g/g; and

C1 a particle size distribution with at least about 80% by weight of the particles of the water-absorbing polymer structure in a particle size range of from about 150 to about 850 μm, at least about 5% by weight of the particles of water-absorbing polymer structure having a particle size in a range of from about 150 to about 250 μm.

2. The process according to claim 1 , wherein the salt comprises from about 0.6 wt % to about 2 wt % based on the water-absorbing polymer structure, of aluminum lactate.

3. The process according to claim 1 , wherein the salt comprises from about 0.6 wt % to about 1 wt % based on the water-absorbing polymer structure, of aluminum lactate.

4. The process according to claim 1 , wherein the salt comprises at least about 75 wt % of the salt, of aluminum lactate.

5. The process according to claim 1 , wherein the salt comprises at least about 100 wt % of the salt, of aluminum lactate.

6. The process according to claim 1 , wherein the salt comprises from about 0.2 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate and an amount of aluminum sulfate wherein the amount of aluminum lactate and aluminum sulfate is at least 0.6 wt % based on the water-absorbing polymer structure.

7. The process according to claim 1 , wherein in process step ii) the untreated, water-absorbing polymer structure is brought into contact with the salt in the presence of at most about 15% by weight, based on the weight of the untreated, water-absorbing polymer structure, of a solvent.

8. A water-absorbing polymer structure comprising,

an untreated, water absorbing polymer structure comprising

(α1) from about 20 to about 99.999% by weight, polymerized, ethylenically unsaturated, acid-group-carrying monomers or their salts or polymerized, ethylenically unsaturated monomers containing a protonated or quaternized nitrogen atom, or mixtures thereof; and

(α2) from 0.001 to about 0.5% by weight of the part (α1), of a crosslinker;

wherein the untreated water-absorbing polymer structure forms an inner region and

an outer region surrounding the inner region, wherein the outer region comprises from about 0.1 to about 5 wt % based on the weight of the untreated, water-absorbing polymer structure, of a salt comprising at least about 50 wt % of the salt, of aluminum lactate, and

of which more than about 80% by weight, relative to the water-absorbing polymer structure, are based on acrylic acid, of which in a range of from about 50 to about 85 mol % are neutralized, the water-absorbing polymer structure having the following properties:

A1 a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 10×10 7 cm 3 s/g to about 180×10 7 cm 3 s/g;

B1 a retention (CRC) determined according to ERT 441.2-02 of at least about 25 g/g; and

C1 a particle size distribution with at least about 80% by weight of the particles of the water-absorbing polymer structure in a particle size range of from about 150 to about 850 μm, at least about 5% by weight of the particles of water-absorbing polymer structure having a particle size in a range of from about 150 to about 250 μm.

9. The water-absorbing polymer structure according to claim 8 , wherein the salt comprises at least about 75 wt % of the salt, of aluminum lactate.

10. The water-absorbing polymer structure according to claim 8 , wherein the salt comprises at least about 100 wt % of the salt, of aluminum lactate.

11. The water-absorbing polymer structure according to claim 8 , wherein the salt comprises from about 0.6 wt % to about 2 wt % based on the water-absorbing polymer structure, of aluminum lactate.

12. The water-absorbing polymer structure according to claim 8 , wherein the salt comprises from about 0.6 wt % to about 1 wt % based on the water-absorbing polymer structure, of aluminum lactate.

13. The water-absorbing polymer structure according to claim 8 , wherein the salt comprises from about 0.2 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate and an amount of aluminum sulfate wherein the amount of aluminum lactate and aluminum sulfate is at least 0.6 wt % based on the water-absorbing polymer structure.

14. The water-absorbing polymer structure according to claim 8 , wherein the outer region further comprises from about 0.01 wt % to about 1 wt % based on the water-absorbing polymer structure, of aluminum sulfate.

15. A composite comprising a water-absorbing polymer structure according to claim 8 and a substrate.