| abstract |
It is an object of the present invention to provide: a rubber stopper composition that is easy to mold and process, excellent in sealing properties and gas-barrier properties, low in propensity to elute into the contents, and satisfactory in needle penetration; and a medical rubber stopper made by using the same. The object of the present invention is attained by a composition made up in a predetermined way by dynamically cross-linking an isobutylene-based polymer in the presence of polyolefin with use of a hydrosilyl-group-containing compound and by further adding a softener to the isobutylene-based polymer thus cross-linked, the isobutylene-based polymer having an alkenyl group at a terminal thereof. To the composition of the present invention, a block copolymer consisting of a polymer block (a) composed mainly of an aromatic vinyl-based compound and a polymer block (b) composed mainly of isobutylene or a lubricant can be added. |