Process for producing a polybutadiene resin composition hardenable by irradiation with ionizing radiations

A polybutadiene resin is produced by a process comprising semiesterifying the hydroxyl radicals of hydroxyl polybutadiene or butadiene copolymer with maleic anhydride. The butadiene copolymer contains at least 50% by weight of butadiene. The semiesterified resin is hardened by irradiation to make coatings hard and flexible in a rapid and easy manner. The process is suitable for continuous application as in coating coils. The remainder can be stored for further use. Moreover, the resin can be applied for electrodeposition by neutralization with an amine or alkali. In embodiments, the semiesterification reaction between the hydroxyl group of hydroxyl polybutadiene or butadiene copolymer and maleic anhydride efficiently takes place at 1200C for 1 hour. The reaction temperature may be 600-1600C, preferably 1000-1200C. The adequate reaction time is 2 hours at 600-800C, 1 hour at 1000-1200C, and 40 minutes at 1200-1400C. The addition of 0.1-1% of antioxydants or radical polymerization inhibitors are preferred to prevent gelation. The copolymerizable compositions may be ionizing radiations including electron beams from the high energy electron beam accelerators. In examples, 1,000 parts of hydroxyl polybutadiene of hydroxyl value 85, and average molecular weight 1,000, and 151 parts of maleic anhydride were mixed and heated at 1000C for 80 minutes to produce a resin. The resin thus produced was irradiated with electron beams at an energy level of 600 kV with doses of 1.5, 5 and 20 Mrad. At 20 Mrad, a pencil hardness of 4H or 5H was obtained. (Iwakiri, K.)