COPOLYMER FOR DETERGENT

The purpose of the present invention is to provide a copolymer for detergent that has exceptional antimicrobial performance during washing and persistence of antimicrobial performance after washing, as well as an exceptional capability to prevent resoiling. The present invention is a copolymer for detergent having structural units (a) derived from a cationic-group-containing monomer (A) and structural units (b) derived from a hydrophobic monomer (B), wherein the copolymer for detergent is characterized in that the copolymer for detergent is a copolymer (α) having a weight-average molecular weight of 1,000-1,000,000 and having structural units derived from a cationic-group-containing monomer (A) represented by formula (4) and/or (5) as structural unit (a), or a copolymer (β) having a weight-average molecular weight of 1,000-200,000 and having structural units derived from a cationic-group-containing monomer (A) represented by formula (6) and/or (7) as structural unit (a), the copolymer (β) being configured such that: the hydrophobic monomer (B) is at least one compound selected from the group consisting of: (meth)acrylates having a homopolymer solubility parameter of 15 or lower and optionally having at least one substituent selected from the group consisting of hydroxyl groups, C1-18 alkoxy groups, sulfonic acid groups, phosphoric acid groups, halogeno groups, epoxy groups, and carbonyl groups; unsaturated monocarboxylic acids; aromatic vinyl monomers such as styrene; olefin monomers; esters of unsaturated alcohols and carboxylic acids; vinyl halides; alkyl vinyl ethers; addition reaction products of C1-20 alcohols and unsaturated monomers having C2-8 cyclic-ether-containing groups; alkylene oxide adducts of C2-20 unsaturated alcohols and end hydrophobic modified forms thereof; and cyclic vinyl monomers; such that the proportion of structural units (e) derived from a monomer (E) other than the cationic-group-containing monomer (A) and the hydrophobic monomer (B) is 0-10% by mass relative to 100% mass of all structural units; and such that the other monomer (E) is at least one compound selected from the group consisting of: esters of (meth)acrylic acids and polyols having two or more hydroxyl group substitutions; a polyol having two or more methacrylic acid ester substitutions; ethers of unsaturated alcohols and polyols having two or more hydroxyl group substitutions; and diallyl phthalate, triallyl phosphate, allyl methacrylate, tetraallyloxyethane, triall