Method for the production of low-odor hydrogel-forming polymers
First Claim
1. A process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of:
- a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and
optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer;
characterized by the acrylic acid used in step a) containing less than 500 ppm (by weight, based on acrylic acid) of acrylic acid oligomers.
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Abstract
The present invention relates to a process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of: a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer; characterized by the acrylic acid used in step a) having a total acrylic acid oligomer content of less than 500 ppm, preferably not more than 400 ppm and especially not more than 300 ppm. Here and hereinafter, all ppm units are by weight based on acrylic acid. It is advantageous for the level of triacrylic acid (compound I where x=2) and higher oligomers of acrylic acid to be less than 100 ppm, especially less than 50 ppm and specifically less than 10 ppm.
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Citations
10 Claims
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1. A process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of:
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a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and
optionallyb) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer;
characterized by the acrylic acid used in step a) containing less than 500 ppm (by weight, based on acrylic acid) of acrylic acid oligomers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for preparing a low-odor hydrogel-forming acrylic acid polymer comprising polymerizing an acrylic acid with an acrylic acid oligomer content of less than 500 ppm.
Specification