Antifouling coating composition and novel resin

A resin which has a weight-average molecular weight within a range from 1,000 to 300,000 and comprises, as a repeating unit, a structural unit (a2) represented by the following formula (2):

• (in the formula (2), R2′ represents a group selected from an alkyl group having 1 to 11 carbon atoms, a benzyl group, a phenyl group and a methylphenyl group, or a hydrogen atom;
• R3′ represents a structure of R—, R—O—R′—, R—O—CO—CH(R2′)—, R—CO—CH(R2′)— or R—O—R′—O—CO—CH(R2′)—;
• R4′ represents a structure of R—, R—O—, R—O—R′— or R—O—R′—O—, in which R represents an alkyl group having 1 to 8 carbon atoms, a benzyl group, a phenyl group, a naphthyl group or a methylphenyl group and R′ represents an alkylene group having 1 to 8 carbon atoms;
• and n and n′ each represents an integer of 0 or 1, where n is 1 when n′ is 0, and n is 0 when n′ is 1).

A resin which has a weight-average molecular weight within a range from 1,000 to 300,000 and comprises, as a repeating unit, a structural unit (a3) represented by the following formula (3):

• (in the formula (3), R2′ represents a group selected from an alkyl group having 1 to 11 carbon atoms, a benzyl group, a phenyl group and a methylphenyl group, or a hydrogen atom;
• R3′ represents a structure of R—, R—O—R′—, R—O—CO—CH(R2′)—, R—CO—CH(R2′)— or R—O—R′—O—CO—CH(R2′)—;
• R4′ represents a structure of R—, R—O—, R—O—R′— or R—O—R′—O—;
• and X3 and X4 each independently represents a hydrogen atom or a methyl group;
• in which R represents an alkyl group having 1 to 8 carbon atoms, a benzyl group, a phenyl group, a naphthyl group or a methylphenyl group and R′ represents an alkylene group having 1 to 8 carbon atoms).