Patent ID: 7829623

Claim:
A process for preparing a thermoplastic vulcanizate composition having a dispersed, cross-linked rubber phase in a continuous thermoplastic polypropylene phase comprising: a) providing into melt processing equipment at least the following components: i) from 5 wt % to 10 wt %, based on the total weight of the thermoplastic vulcanizate, of at least one thermoplastic polypropylene homopolymer or copolymer having a melt temperature greater than 120° C., and a heat of fusion greater than 45 J/g; ii) 6-12 wt. %, based on the total weight of the thermoplastic vulcanizate composition, at least one propylene copolymer having from 7 to 30 wt. % ethylene, based upon the weight of the propylene copolymer, a melting point less than 120° C., and a heat of fusion less than 45 J/g; iii) from 15 wt % to 35 wt %, based on total weight of the thermoplastic vulcanizate, of at least one cross-linkable rubber, where, if including an ethylene copolymer rubber, said copolymer rubber having equal to or more than 40 wt. % the total copolymer rubber weight; and iv) from about 30 to 250 parts by weight, per 100 parts by weight of the rubber, of an oil; b) melt processing the blend of i), ii), of a); c) dynamically vulcanizing the cross-linkable rubber iii) in the presence of the thermoplastic i) and copolymer ii), where said step of dynamically vulcanizing is effected by employing a phenolic resin cure system at a temperature of from 180° C. to 240° C.; and where prior to said step of dynamically vulcanizing, volatiles produced by said step of melt processing b) are vented from the melt processing equipment d) removing a thermoplastic vulcanizate product of c) from the melt processing equipment, wherein the dispersed, cross-linked rubber phase of the thermoplastic vulcanizate product d) consists of particles having an effective diameter not greater than 2 millimicrons, where said thermoplastic polypropylene homopolymer or copolymer and said propylene copolymer have at least 90% of the same tacticity, further comprising the step of fabricating the thermoplastic vulcanizate, where said step of fabricating includes (i) extruding at a pressure of not greater than 10 bar for at least 6 hours under die plug free conditions or (ii) injection molding the thermoplastic vulcanizate to form a molded part that is free of flow marks.