PURPOSE: To obtain the subject composition which gives a coating film excellent in water resistance, solvent resistance, chemical resistance, drying properties, tensile strength, etc., by using a specific acrylic copolymer and a specific polyisocyanate in a given proportion as major components.

CONSTITUTION: A vinyl monomer having an alkoxysilane group and represented by formula I (wherein A is a group represented by formula II or III; R1 is H or CH3; R2 is a 1-15C divalent aliphatic saturated hydrocarbon group; R3 and R4 are each phenyl, a 1-6C alkyl, or a 1-10C alkoxy; R5 is a 1-10C alkyl; and (n) is 1-100) is copolymerized with a carboxylated unsaturated monomer and a hydroxylated unsaturated monomer and optionally with other monomer(s) copolymerizable therewith, the amount of the vinyl monomer being 1-90wt.% based on all the monomers. Thus, a water-dispersible acrylic copolymer (A) is obtained which has an acid value of 20-150 and a hydroxyl value of 10-250. The composition in the title comprises as major components the copolymer (A) and a polyisocyanate (B) having two or more NCO groups in such a proportion that the amount of the NCO groups of (B) is about 0.2-3 equivalents to the OH groups of (A).