To obtain a compsn. with an excellent curing property and storage stability, by compounding not only a urethane prepolymer, an amine type catalyst and/or amine type latent curing agent, but also a barbituric acid or its deriv. and/or an active methine compd.

This is a resin compsn. comprising a urethane prepolymer, 0.001-0.1 equivalent, based on one equivalent of the NCO group, of an amine type catalyst such as an N-methylmorpholine and/or 0.1-1 equivalent of an amine type latent curing agent such as an oxazolidine compd., as well as 0.001-20 wt.%, based on the wt. of the compsn., of a barbituric acid or its deriv. having formula I and/or an active methine compd. having formula II. A urethane sealant is obtd. by blending 100 pts.wt. of this compsn. with 0.1-20 pts.wt. of a silyl ester compd., 50-200 pts.wt. of a filler, a plasticizer, an antioxidant, a solvent, etc. In the formulae, R1 and R2 are each hydrogen or a 1-18C hydrocarbon group; R3 and R4 are each a 1-10C hydrocarbon group; m and n are each 0-3; and m+n=3.