PURPOSE: To obtain a curable compsn., which gives a cured item free from residual surface tack, i.e., a problem in a curable compsn., by the reaction of a thiol or silylthio group with an isocyanate group, which is useful as a sealant for building.

CONSTITUTION: This compsn. contains a polymer having at least two thiol groups or at least two silylthio groups represented by the formula (wherein R2, R3, and R4 are each a 1-6C alkyl, phenyl, or a haloalkyl group) in the molecule, a polyisocyanate compd. having at least two isocyanate groups in the molecule, and a molecular sieve with an amine occluded therein and gives a cured item with no surface tack.