| 摘要 |
PROBLEM TO BE SOLVED: To obtain a new prepolymer which can form coating films having excellent surface smoothness, weather resistance and mechanical and physical properties, when reacted with a polyol, and so used as a curing agent for one pack solvent type coating materials, powdered coating materials, or the like, by reacting diisocyanatomethylbicycloheptane in the presence of a uretdione-forming catalyst. SOLUTION: This new uretdione group-containing prepolymer of the formula [(n) is >=1] is obtained by reacting 2,5- and/or 2,6-diisocyanatomethylbicyclo[2.2.1]heptane (hereinafter NBDI) as an essential component, preferably a mixture of NBDI with one or more other aliphatic diisocyanate compounds in a weight ratio of 1/9 to 9/1 in the presence of a uretedione-forming catalyst [for example, a tris(dialkylamino) phosphine compound]. The catalyst is usually used in an amount of 0.1-1.0 wt.% based on NBDI (or the total amount of NBDI and the other aliphatic diisocyanate compounds). The prepolymer is usually produced by reacting the raw materials at 30-150 deg.C for several hr, adding a catalyst-deactivating agent to the reaction solution to stop the reaction, and then removing the unreacted NBDI, and the like, contained in the reaction solution by the use of a thin film type distillator, or the like.
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