Patent ID: 7439304

Claim:
A composition comprising: (i) a dynamically-cured rubber; (ii) from about 20 to about 300 parts by weight of an isotactic polypropylene having a melt temperature of from 150° C. to 175° C. and a density of from 0.85 g/cc to 0.91 g/cc per 100 parts by weight rubber; (iii) from 0.3 to 0.9 parts by weight stannous chloride per 100 parts by weight rubber; (iv) from 0.4 to 0.7 parts by weight zinc oxide per 100 parts by weight rubber; (v) from about 0.1 to about 5% by weight, based upon the total weight of the composition, of a natural or synthetic hydrotalcite; and (vi) from about 30 to about 250 parts by weight oil per 100 parts by weight rubber wherein said composition exhibits an elongation retention in excess of 80% after heat aging at 125° C. for six weeks, said composition exhibits a tensile strength retention in excess of 80% after heat aging at 125° C. for six weeks, said dynamically-cured rubber is cured with a phenolic resin consisting of a blend of about 33% by weight of the total resin octvlphenol-formaldehyde and about 67% by weight of the total resin nonylphenol-formaldehyde by dynamic vulcanization to an extent where not more than 3 weight percent of the rubber is extractable by using cyclohexane or boiling xylene as an extractant and said dynamically-cured rubber is in the form of discrete particles within the isotactic polypropylene, and where the discrete particles have an average particle size that is less than 5 μm.