ylol group of 1 to 5 carbon atoms, and X is a halogen atom, and (b) a recurring unit derived from an acrylic monomer represented by the following formula (A): CH2 ═CR3 --CO--Q (A) wherein R3 is a hydrogen atom, a methyl group or an ethyl group, and Q is --NH2, --NH--R4 --OH, where R4 is an alkylene group of 1 to 5 carbon atoms, or --R5, where R5 is a hydrogen atom