Sealing composition comprising a mixture of brominated butyl rubber, polyisobutylene and carbon black, and method of making same

A sealing composition comprises a mixture of brominated butyl rubber and polyisobutylene, a curative agent for brominated butyl rubber, and optionally amorphous or activated carbon. 100 parts of the mixture contains 10 to 90 parts and 90 to 10 parts of rubber and polyisobutylene, up to 200 parts of the carbon and sufficient curative to cure the brominated butyl rubber. In addition, up to 150 parts of an epoxyhydroxy polyether resin and sufficient curative to cure the resin may be included. The composition is prepared by milling the rubber at elevated temperature, e.g. 200 DEG to 400 DEG F. with part of the polyisobutylene and carbon if used, cooling, adding the epoxyhydroxy polyether resin if required, and incorporating a mixture of curative and the remaining polyisobutylene prior to use. Curing agents include p-quinone dioxime and sulphur, and activators such as 1,3-dichloro-5,5 dimethyl hydantoin, zinc oxide, lead oxide and dioxide and red lead, stearic acid and polyparadinitrosobenzene may be present. The epoxyhydroxy polyether resin is prepared by the condensation of polyhydric phenol and an epihalohydrin or polyepoxy compound and may be cured with amines, and when present the product is stiffer and less sticky. The compositions are suitable as window putty or caulking compounds, particularly for joints and seams of inert elastomeric liners. Specification 798,602 is referred to.