| abstract |
(57) Abstract: To improve the initial residual tack of a building sealing material containing an isobutylene-based polymer having a reactive silicon group. The star-shaped branched polymer has a hydroxyl group or a hydrolyzable group bonded to a silicon atom and has at least one silicon-containing group capable of crosslinking by forming a siloxane bond, and forms a branch. A curable composition containing, as a main component, a polymer composed of an isobutylene-based polymer. |