PURPOSE: To obtain a coating composition which is solvent-free and does not contaminate the working environment by incorporating a curing compound in a liquid resin formed by polymerizing a specific (meth)acrylate monomer, a polymerizable unsaturated carboxylic acid and an other vinyl compound.

CONSTITUTION: A liquid resin with a number average molecular weight of 1×104-2×105 and a viscosity of 500-200,000cPs (50°C) is produced by copolymerizing 50-95wt.% of a (meth)acrylate monomer of the formula (wherein R1 is H or CH3; R2 is a 1-5C hydrocarbon; n is 1-3; and m is 4-25) tetraethylene glycol methacrylate, etc.) 5-50wt.% of a polymerizable unsaturated carboxylic acid (maleic acid, etc.) and 0-20wt.% of an other polymerizable vinyl compound (styrene, etc.) in the presence of isopropanol, etc., which is a good solvent for the raw monomers but a poor solvent for the polymer. A substantially solvent- free coating composition is produced by incorporating 0.3-10 reaction equivalents of a curing agent having 2 or more functional groups in the molecule (maleic acid, etc.) for each equivalent of the carboxyl group of the resin. The coating material can be used in a usual coating manner and dried by heating.