Water-absorbing, cellular, cross-linked polymers with improved distribution effect, method for their production and their use
First Claim
1. An expanded, crosslinked polymer which has a free absorption speed (FAS) for a 0.9% aqueous sodium chloride solution of from 4.0 to 100 g/g sec, obtained by(I) foaming a polymerizable aqueous mixture which comprises (a) one or more monoethylenically unsaturated monomers which contain acidic groups or monoethylenically unsaturated monomers which contain acidic groups neutralized with alkali metal bases, ammonia or amines, (c) one or more crosslinkers, (d) one or more initiators and (e) 0.1-20% by weight of at least one surfactant, where the foaming takes place by dissolving a gas which is inert to free radicals under a pressure of 2-400 bar in the polymerizable aqueous mixture, and then decompressing the aqueous mixture to atmospheric pressure, and (II) polymerizing the foamed mixture to form an expanded hydrogel.
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Abstract
Water-absorbing, expanded, crosslinked polymers obtainable by
(I) foaming a polymerizable aqueous mixture which comprises
(a) monoethylenically unsaturated monomers which contain acidic groups and are optionally neutralized,
(b) optionally other monoethylenically unsaturated monomers,
(c) crosslinkers,
(d) initiators,
(e) 0.1-20% by weight of at least one surfactant,
(f) optionally at least one solubilizer and
(g) optionally thickeners, foam stabilizers, polymerization regulators, fillers and/or cell nucleating agents,
where the foaming takes place by dissolving a gas which is inert to free radicals under a pressure of 2-400 bar in the polymerizable aqueous mixture, and then decompressing the latter to atmospheric pressure, and
(II) polymerizing the foamed mixture to form an expanded hydrogel and, where appropriate, adjusting the water content of the expanded polymer to 1-60% by weight, process for preparing the water-absorbing, expanded, crosslinked polymers and use of these polymers in sanitary articles employed for absorbing body fluids, in dressing material for covering wounds, as sealing material, as soil improver, as soil substitute and as packaging material.
149 Citations
18 Claims
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1. An expanded, crosslinked polymer which has a free absorption speed (FAS) for a 0.9% aqueous sodium chloride solution of from 4.0 to 100 g/g sec, obtained by
(I) foaming a polymerizable aqueous mixture which comprises (a) one or more monoethylenically unsaturated monomers which contain acidic groups or monoethylenically unsaturated monomers which contain acidic groups neutralized with alkali metal bases, ammonia or amines, (c) one or more crosslinkers, (d) one or more initiators and (e) 0.1-20% by weight of at least one surfactant, where the foaming takes place by dissolving a gas which is inert to free radicals under a pressure of 2-400 bar in the polymerizable aqueous mixture, and then decompressing the aqueous mixture to atmospheric pressure, and (II) polymerizing the foamed mixture to form an expanded hydrogel.
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6. A process for producing expanded, crosslinked polymers, comprising
foaming a polymerizable mixture of (a) one or more monoethylenically unsaturated monomers which contain acidic groups or monoethylenically unsaturated monomers which contain acidic groups neutralized with alkali metal bases, ammonia or amines, (c) one or more crosslinkers, (d) one or more initiators and (e) 0.1-20% by weight of at least one surfactant, to form a foam in a first stage with a gas which is inert to free radicals, and in a second stage polymerizing the foam to form an expanded hydrogel, where in the first stage a gas which is inert to free radicals is dissolved under a pressure of 2-400 bar in the polymerizable aqueous mixture, and the aqueous mixture is then decompressed to atmospheric pressure to form a foam.
Specification