Patent ID: 8541539

Claim:
A method for preparing a water-soluble polyamide, comprising the steps of: copolymerizing reactive monomers including: caprolactam; ethylene glycol bis(2-aminoethyl)ether or ethylene glycol bis(3-aminopropyl)ether; and 5-sulfoisophthalic acid monosodium salt, wherein the reactive monomers have a molar ratio of caprolactam:ethylene glycol bis(2-aminoethyl)ether or ethylene glycol bis(3-aminopropyl)ether:5-sulfoisophthalic acid monosodium salt is about 0:1:1 to about 5:1:1, and wherein the reactive monomers have a molar ratio of sulphonate group to carboxyl group is 0.5.