Patent ID: 7288602

Claim:
A method for processing a rubber composition by a multi-stage mixing procedure, the method comprising: (A) mixing a rubber composition at a rubber temperature in a range of from 140° C. to 190° C. for a mixing time of from 1 to 20 minutes, said rubber composition comprising (1) 100 parts by weight of at least one sulfur vulcanizable elastomer wherein (a) from 40 to 100 parts by weight of said vulcanizable elastomer is a multi-viscoelastic response rubber wherein said multi-viscoelectric response rubber is an emulsion styrene-butadiene rubber composition comprised of (A) a high molecular weight styrene-butadiene rubber having a weight average molecular weight of at least about 300,000; and (B) a low molecular weight styrene-butadiene rubber having a weight average molecular weight which is less than about 280,000; wherein the ratio of the high molecular weight styrene-butadiene rubber to the low molecular weight styrene-butadiene rubber is within the range of about 80:20 to about 25:75; wherein the styrene-butadiene rubber composition is made by coagulating a blend of a latex of the high molecular weight styrene-butadiene rubber and a latex of the low molecular weight styrene-butadiene rubber; and (b) from zero to 60 parts by weight of said vulcanizable elastomer is a rubber containing olefinic unsaturation other than said multi-viscoelastic rubber; (2) from 0.1 to 25 phr of an organosilicon compound of the formula: Z-Alk-S n -Alk-Z in which Z is selected from the group consisting of where R 1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; R 2 is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is from 2 to 8; (3) from 10 to 250 phr of a silica filler; and (4) the absence of zinc oxide to form a non-productive compound; and (B) mixing a productive compound at a rubber temperature not to exceed 120° C., the productive compound comprising (1) said non-productive compound; (2) from 0.5 to 5 phr of a sulfur vulcanizing agent; and (3) from 1 to 8 phr of zinc oxide.