Water-absorbing polymer structure having improved permeability and absorption under pressure
The present invention relates to a process for the preparation of water-absorbing polymer structures, 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 a salt comprising a divalent or higher-valent cation of a metal and at least one organic base as anion. The invention relates also to the water-absorbing polymer structures obtainable by that process, to water-absorbing polymer structures, to a composite comprising a water-absorbing polymer structure and a substrate, to a process for the preparation of a composite, to the composite obtainable by that process, to chemical products, such as foams, molded articles and fibers comprising water-absorbing polymer structures or a composite, to the use of water-absorbing polymer structures or of a composite in chemical products and to the use of a salt in the treatment of the surface of water-absorbing polymer structures.
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;
ii) bringing the untreated, water-absorbing polymer structure into contact with a salt comprising at least one organic base as an anion and from about 0.2 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate; and aluminum sulfate wherein the amount of aluminum lactate and aluminum sulfate is at least 0.6 wt % based on the water-absorbing polymer structure, and wherein the water-absorbing polymer structure has a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 100×10 −7 cm 3 s/g to about 180×10 −7 cm 3 s/g.
2. 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.
3. 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 (al), 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 0.2 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate; and aluminum sulfate wherein the amount of aluminum lactate and aluminum sulfate is at least 0.6 wt % based on the water-absorbing polymer structure, and wherein the water-absorbing polymer structure has a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 100×10 −7 cm 3 s/g to about 180×10 −7 cm 3 s/g.
4. The water-absorbing polymer structure according to claim 3 , 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 wherein the water-absorbing polymer structure has a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 100×10 −7 cm 3 s/g to about 120×10 −7 cm 3 s/g.
5. A composite comprising a water-absorbing polymer structure according to claim 3 and a substrate.
6. The water-absorbing polymer structure according to claim 3 , comprising from about 0.6 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate.
7. A water-absorbing polymer structure comprising
i) an untreated, water-absorbing polymer structure; and
ii) a post-crosslinking compound comprising from about 0.2 wt % to about 1 wt % based on the water-absorbing polymer structure of aluminum lactate; and aluminum sulfate wherein the amount of aluminum lactate and aluminum sulfate is at least 0.6 wt % based on the water-absorbing polymer structure, and wherein the water-absorbing polymer structure has a saline flow conductivity (SFC) determined in accordance with the test method described herein of from about 100×10 −7 cm 3 s/g to about 180×10 −7 cm 3 s/g.
8. A composite comprising a water-absorbing polymer structure according to claim 7 and a substrate.