at when each of R1, R2 and R3 is a hydroxyl group, their corresponding q1, q2 and q3, r1, r2 and r3 are each 1, X is a divalent group comprised of 2 to 5 carbon atoms in which a carbon atom adjacent to at least one of the carbonyl carbons has a carbon-carbon double bond, and J is favorably a group represented by the following general formula (VIII):