Patent ID: 8076434

Claim:
An amphoteric polymer comprising: a structure unit (a) derived from a cationic group-containing monomer (A); and a structure unit (b) derived from a carboxyl group-containing monomer (B), the cationic group-containing monomer (A) represented by the formula (1) or (1′): wherein R 0 represents CH 3 ; R 1 represents CH 2 CH 2 ; R 2 , R 3 , and R 4 each represent a C 1-20 organic group, and each of R 2 , R 3 , and R 4 may be the same as or different from each other; R 5 and R 6 each represent H or a C 1-20 organic group and may be the same as or different from each other; Y 1 represents a C 2-20 alkylene group, and each of Y 1 s may be the same as or different from each other; n represents an average addition number of moles of oxyalkylene groups (—Y 1 —O—) and is from 1 to 300; and X − represents a counteranion, wherein, the structure unit (a) is present at a level of 1 to 99% by mass based on 100% by mass of all structure units derived from all monomers in the amphoteric polymer, and the structure unit (b) is present at a level of 1 to 99% by mass based on 100% by mass of all the structure units derived from all the monomers in the amphoteric polymer.