| 摘要 |
PROBLEM TO BE SOLVED: To obtain a urethane prepolymer composition made proof against a long-term increase in viscosity even under heating or in a humid atmosphere by setting the reaction ratio of an isocyanate compound to a polyol compound in a specified range. SOLUTION: The reaction ratio of an isocyanate compound to a polyol compound is such that 10-100 mol of the hydroxy group of the latter are present per 100 mol of the former. The isocyanate compound is desirably one comprising 5-80 mol% 2,4-diphenylmethane diisocyanate and 95-20 mol% 4,4'- diphenylmethane diisocyanate. The polyol compound may be one usually used in the production of a polyurethane and is exemplified by polyethylene glycol. In order to adjust the melt viscosity or adhesion to a substrate, it is also possible to add a tackifier such as a rosin resin or a thermoplastic resin such as an ethylene/vinyl monomer copolymer.
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