wherein R1 is hydrogen, or a straight-chain, branched or cyclic alkyl group or aralkyl group having 1 to 20 carbon atoms, m is an integer of 1 to 4, and n is an integer of 1 to 100, with an oxide or a hydroxide of a metallic atom that is at least divalent in the presence of water, the water being included in an amount of 1 to 30% by weight based on the weight of the solids of the base resin, and a