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US 7,008,508 B2Granted
Composition for increasing wet strength of paper including water-soluble blocked urethane prepolymers
AssigneeDai-Ichi Kogyo Seiyaku Co., Ltd.
InventorsTakeshi Doi, Takeshi Miyamura, Masahiro Kouchi
Life of this patent
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Abstract
For use as a wet strength agent, a water-soluble blocked urethane prepolymer having a hydrophilic group and a blocked isocyanate group is combined with a cationic charge-adjusting agent. The adsorption and retention of the water-soluble blocked urethane prepolymer to cellulosic fiber are promoted by virtue of the cationic charge adjusting agent when the wet strength agent is added to a paper-making stock.
Claims16
A composition for increasing the wet strength of paper comprising:
- (a) a water-soluble blocked urethane prepolymer having a hydrophilic group and a blocked isocyanate group capable of thermally unblocking;
- wherein the water-soluble blocked urethane prepolymer is produced by blocking a urethane prepolymer having a plurality of free isocyanate groups and at least one tertiary amino group with a phenolic compound having an electron-attracting group of trifluoromethyl, nitro, cyano, acetyl, alkoxycarbonyl, carboxyl or alkylsulfonyl at the ortho- or para-position followed by quaternizing or neutralizing the tertiary amino group, the water-soluble urethane prepolymer is free of a reversibly blocked isocyanate group other than those derived from the phenolic compound;
- and
- (b) a cationic compound or polymer effective for enhancing the cationic charge of the blocked urethane prepolymer in an aqueous solution.
1 more element
Dependencies are inferred from the claim text.