Abstract:
The invention relates to a process for producing superabsorbents, comprising the preparation of partly neutralized acrylic acid by the steps (i) preparing an over-neutralized acrylic acid having a degree of neutralization of at least 100.1 mol-% by mixing of an acrylic acid 1 and a base and (ii) preparing a neutralized acrylic acid having a degree of neutralization from 50 to 85 mol-% by mixing of the over-neutralized acrylic acid and an acrylic acid 2, wherein the content of dimeric acrylic acid in the acrylic acid 2 is lower than the content of dimeric acrylic acid in the acrylic acid 1.
Abstract:
Absorbent core and an absorbent article respectively with improved properties, especially rewet performance, are disclosed. The absorbent core contains at least two layers, wherein each layer has from 0 to 10% by weight fibrous material and from 90 to 100% by weight water-absorbent polymer particles, based on the sum of water-absorbent polymer particles and fibrous material. The surface crosslinked water absorbent polymer particles within the upper layer have a sphericity of at least 0.89 and the absorbent core shows a CRCAP/TACAP ratio of at least 0.65.
Abstract:
An absorbent core and an absorbent article respectively with improved properties, especially rewet performance, are disclosed. The absorbent core has at least two layers, wherein each layer comprising from 0 to 10% by weight fibrous material and from 90 to 100% by weight water-absorbent polymer particles, based on the sum of water-absorbent polymer particles and fibrous material. The surface-postcrosslinked water absorbent polymer particles within the upper layer have a sphericity of at least 0.89 and a CRC of at least 34 g/g. Preferably the water-absorbent polymer particles have a sphericity of at least 0.89 and the sum of the CRC and AUL (0.3 psi, 21 g cm−2) (EDANA 442.2-02) of the water absorbent polymer particles is at least 65 g/g.
Abstract:
A process for thermal surface postcrosslinking of water-absorbing polymer particles, wherein the polymer particles are coated with an aqueous solution, the coated polymer particles are deagglomerated and the deagglomerated polymer particles are thermally surface postcrosslinked by means of a drum heat exchanger with an inverse screw helix.
Abstract:
A superabsorbent obtainable by a process for producing superabsorbents by polymerizing a monomer solution comprising a) at least one ethylenically unsaturated monomer which bears acid groups and is optionally present at least partly in salt form, b) at least one crosslinker, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomers mentioned under a), e) optionally one or more water-soluble polymers, the process further comprising drying of the resulting polymer and optionally grinding of the dried polymer and sieving of the ground polymer and optionally surface postcrosslinking of the dried and optionally ground and sieved polymer, wherein at least one sulfonic acid derivative is added to the monomer mixture and/or to the polymer prior to the drying, and at least one phosphonic acid derivative is added to the polymer after the drying or optionally after the surface postcrosslinking, exhibits improved stability to discoloration in the course of storage at elevated temperatures or under elevated air humidity.
Abstract:
Superabsorbents comprising pyrogenic aluminum oxide exhibit a low caking tendency coupled with good absorption properties and rapid water absorption.