| 摘要 |
PROBLEM TO BE SOLVED: To provide a urethane acrylate oligomer for ultraviolet curing which does not deposit crystals, permits little decrease of the elastic modulus at -20 to 80 deg.C, exerts a high elastic modulus at a cold-hot cycle test temperature range, has an ability to inhibit cracking of surface materials of plywoods especially at woodwork use and, compared to the conventional urethane acrylate oligomers, shows a low viscosity at ordinary temperatures even without adding organic solvents or reactive diluents and easily reduces its viscosity when heated since the viscosity has a large dependence on temperature, and an ultraviolet- curing coating composition using the oligomer. SOLUTION: An ultraviolet-curing urethane acrylate oligomer comprises a polyisocyanate and hydroxyalkyl acrylate, wherein, as essential components, 1,3-bisisocyanatomethylcyclohexane is used as the polyisocyanate and 2- hydroxypropyl acrylate and 2-hydroxyethyl acrylate are used as the hydroxyalkyl acrylate. Here, the mixing molar ratio of 2-hydroxypropyl acrylate/2-hydroxyethyl acrylate is 0.9/0.1 to 0.25/0.75.
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