Process for hardening a resin composition by radiation cross-linking

A new composition and process suitable for coatings, adhesives, and resinous raw materials for molding articles are provided to improve physical and chemical properties by cross-linking polymerization employing ionizing radiations. The process comprises irradiating with ionizing radiations. A composition made by dissolving or swelling methyl acrylate resins in methyl acrylate or a methyl acrylate-vinyl monomer mixture. The methyl acrylate unit requires not less than one mole %, preferably not less than 10% of high molecular compounds or their mixture. The content of the methyl methacrylate resins in the composition are generally preferred in the 0.5% to 50% range. The radiation dose may be from 103 to 108 r, usually 104 to 107 r. In one example, 20 parts by weight of a copolymer consisting of methyl acrylate and methyl methacrylate were dissolved in 80 parts of methyl acrylate. This resin composition was coated on a galvanized plate to form a film of 10 microns in thickness. This film was irradiated with an accelerated electron beam with 2 Mrad in air at room temperature. The hardness of the irradiated coating was 2H. The residue after immersion in acetone for 30 min., was shown to be considerable. In another example, a composition was composed of 20 parts of the copolymer in example 1, 50 parts of methyl acrylate and 30 parts of vinyl acetate. The hardening was carried out as above. The hardness was 2H. (Iwakiri, K.)