Co-agents for the preparation of thermoplastic elastomeric blends of rubber and polyolefins

A process for preparing a dynamically vulcanized thermoplastic elastomer composition comprising:

• blending a mixture of at least one polypropylene resin and at least one ethylene/alpha-olefin/non-conjugated diene elastomer at a temperature above the melting point of the at least one polypropylene resin;
• adding a free radical initiator, at least one co-agent comprising diene-containing polymers with a 1,2-vinyl content greater than about 50% by weight, and at least one co-agent comprising multifunctional acrylates containing at least two acrylate groups or multifunctional maleimides containing at least two imide groups;
• and
• then mixing and shearing the blend sufficiently at a temperature to effect crosslink formation such that the elastomer has a gel content of at least 97%, wherein the free radical initiator and the co-agents are collectively present in an amount sufficient to provide blends of the invention having a shore A durometer hardness of at least 70 with an oil swell of less than about 90% by weight, and blends having a shore A durometer hardness of no greater than 70 with an oil swell of less than about 100% by weight.

A thermoplastic elastomer curing system comprising:

• a free radical initiator comprising at least one organic peroxide;
• a first co-agent comprising diene-containing polymers with a 1,2-vinyl content greater than about 50% by weight;
• and
• a second co-agent comprising multifunctional acrylates containing at least two acrylate groups, multifunctional maleimides containing at least two imide groups, or mixtures thereof;
• wherein the curing system includes sufficient amounts of the free radical initiator and the co-agents, when combined with at least one polypropylene resin and at least one additional ethylene-containing material, to form a reactively modified thermoplastic elastomer blend having a gel content of the elastomer of at least 97% and to provide blends of the invention having a shore A durometer hardness of at least 70 with an oil swell of less than about 90% by weight, and blends having a shore A durometer hardness of no greater than 70 with an oil swell of less than about 100% by weight.