Thermosetting polyurethane resin and coating agent thereof prepared from at least two polyoxyalkylene polyols, blocking agent, chain-elongating agent, cross-linking agent and a mixture of diisocyanates

A thermosetting polyurethane resin obtained by interacting:

• (a) a prepolymer having terminal NCO groups which is obtained by reacting at least one polyoxyalkylene polyol with methylene bis(4-cyclohexylisocyanate) and isophorone diisocyanate and then with a chain-elongating agent,
• (b) a monofunctional isocyanate-blocking agent,
• (c) a non-ionic surface active agent selected from the group consisting of a polyoxyethylene glycol or a polyoxyethylene-polyoxypropylene glycol, and mixtures thereof, and
• (d) a cross-linking agent
• wherein said prepolymer is reacted with said monofunctional isocyanate-blocking agent, the total weight percentage of said at least one polyoxyalkylene polyol and said non-ionic surface active agent is 10 to 40% based upon the weight of the nonvolatile matter of the thermosetting polyurethane resin, the weight percentage of said non-ionic surface active agent is 1 to 8% relative to the weight of the non-volatile matter of the thermosetting polyurethane resin, and the molar ratio of the methylene bis(4-cyclohexylisocyanate) and iso-phorone diisocyanate is in the range of from 1:0.3 to 1:1.5.