PURPOSE: A composition having improved adhesiveness after curing, preventing expansion in volume, easily treatable free from temperature dependence of viscosity, obtained by blending polybutadiene or a copolymer consisting essentially of butadiene with a specific polyether polymer.

CONSTITUTION: (A) 100pts.wt. modified or unmodified polybutadiene or copolymer consisting essentially of butadiene is blended with (B) 1W1,000pts.wt. polyether polymer containing at least one hydrolyzable silicon group in the molecule and 300W15,000 molecular weight. The component A used has a group such as hydroxyl group, carboxyl, or ester, etc. or is hydrogenated. The component B used consists essentially of propylene oxide. The composition is preferably blended with a small amount of a curing catalyst.