PURPOSE: To obtain a material for a coating compound having improved film properties without causing coloring in reaction and gelation, by polymerizing a cyclopentadiene type monomer in the presence of a solvent for a coating compound, adding a natural oil type or alkyd resin type vehicle component to the polymer, followed by heating.

CONSTITUTION: In the presence of a solvent for a coating compound (e.g., mineral spirit, xylene, etc.), preferably 40W80wt% cyclopentadiene type monomer (e.g., dicyclopentadiene, etc.) is polymerizied in a conversion of ≥80%, to this polymer solution a natural oil type (e.g., linseed oil, tung oil, etc.) or an alkyl resin type (e.g., stand oil or boiled oil of a natural oil, etc.) vehicle component, to give a material for coating compound modified with a cyclopentadiene polymer. The content of the cyclopentadiene polymer in the reaction product is preferably 10W30wt%.

EFFECT: The production efficiency is improved and reactivity is good.