Resin composition formed by ionizing radiations

A radiation hardenable resin composition is disclosed, a coating layer of which will not crack due to contraction during polymerization when a monomer is employed as a solvent and cross-linking agent. The composition is characterized by containing a vinyl acetate monomer, at least 50% by weight of the total resin being diallyl phthalate prepolymer, and containing 1 to 30 parts by weight of particulate SiO2 for 100 parts of the resin. In addition to vinyl acetate, the resin may contain the tertiary compound alpha-olefinic monomer that can react with vinyl acetate. The polymer of this invention is obtained by stopping the polymerization before gelation and by separating unreacted monomer. Certain desirable properties of the prepolymer are a melting point of 500 to 1100C, an iodine value of 45 to 65 and a viscosity of 35 to 110 C.P. In one of the examples, a solution consisting of 50 parts of diallyl phthalate prepolymer, 50 parts of vinyl acetate, 2 parts of aerosil and 8 parts of tokusil GUN were coated on a decorative plate and irradiated with electron beams at a dose of 3.6 Mrad at an energy level of 1.5 MeV for 16 hours. An absorbent cotton mass filled with acetone was left on the irradiated surface coating of the plate for 15 minutes, without producing corrosion or cracks. (Iwakiri, K.)