Cosmetic composition and hair wash

1. A cosmetic composition comprising a copolymer (I) and a metal pyrithione salt, wherein the copolymer comprises constituting units corresponding to a cationic vinyl monomer (A) represented by the following formula (I) and constituting units corresponding to a nonionic vinyl monomer (B) represented by the following formula (II) and/or (III); the proportion of the constituting units corresponding to the cationic vinyl monomer (A) is from 10 to 80 wt % to the total constituting units constituting the copolymer; and the weight average molecular weight of the copolymer is from 10,000 to 2,000,000:

CH 2 ═C(R 1 )—CO(O) a —(NH) 1-a —(CH 2 ) b —N + R 2 R 3 R 4 X −   (I)

wherein R 1 is a hydrogen atom or a methyl group, each of R 2 and R 3 which are independent of each other, is a C 1-24 alkyl group, a C 1-24 aryl group or a C 1-24 aralkyl group, R 4 is a hydrogen atom, a C 1-24 alkyl group, a C 1-24 aryl group, a C 1-24 aralkyl group or —CH 2 —CH(OH)—CH 2 —N + R 5 R 6 R 7 Y − , each of R 5 to R 7 which are independent of one another, is a C 1-24 alkyl group, a C 1-24 aryl group or a C 1-24 aralkyl group, each of X − and Y − which are independent of each other, is an anion, a is 0 or 1, and b is an integer of from 1 to 10

CH 2 ═C(R 8 )—CO(O)—X—H  (II)

wherein R 8 is a hydrogen atom or a methyl group, and X is a bivalent linking group containing at least two hydroxy groups

CH 2 ═C(R 9 )—CO—NR 10 R 11   (III)

wherein R 9 is a hydrogen atom or a methyl group, and each of R 10 and R 11 which are independent of each other, is a hydrogen atom, a C 1-4 alkyl group or a C 1-4 hydroxyalkyl group; and

wherein the amount of the cationic vinyl monomer (A) is from 0.1 to 10.0 meq/g, the amount of nonionic vinyl monomer (B) represented by formula (II) is 1.5 to 20.0 meq/g if present, and the amount of nonionic vinyl monomer (B) represented by formula (III) is 1.5 to 10.0 meq/g if present; and when the cosmetic composition is used as a hair wash, the amount of adsorption of the metal pyrithione salt is at least 20 μg/g on at least one of untreated hair and damaged hair.

2. The cosmetic composition according to claim 1 , wherein the metal pyrithione salt is zinc pyrithione.

3. The cosmetic composition according to claim 1 , which further comprises an anionic surfactant.

4. The cosmetic composition according to claim 2 , which further comprises an anionic surfactant.

5. A hair wash employing the cosmetic composition as defined in claim 1 .

6. A hair wash employing the cosmetic composition as defined in claim 2 .

7. A hair wash employing the cosmetic composition as defined in claim 3 .

8. A hair wash employing the cosmetic composition as defined in claim 4 .