Patent ID: 6561244
Filing Date: 2003-05-13
Classification: B60C,C08K,C08L

Abstract:
A tire having a rubber tread configured with lugs and grooves wherein a portion of said grooves are of a non-black color and are exclusive of carbon black and wherein the faces of said lugs are defined by a tread cap layer, designed to ground-contacting, contain carbon black and are thereby of a black color, wherein:(A) said rubber tread contains a non-black colored, silica reinforced, rubber layer, exclusive of carbon black, underlying said lug faces, which extends to a visible bottom of at least one of said tread grooves and is thereby exclusive of any appreciable portion of said lug face and wherein said non-black colored rubber layer is an intermediate rubber layer positioned between and co-extruded with said tread cap layer and a black colored, carbon black-containing tread base layer, and wherein (B) said non-black colored rubber layer is comprised of (1) 100 phr of elastomer comprised of (a) about 20 to about 100 phr of at least one diene-based elastomer and (b) from zero to about 80 phr of a halogenated copolymer of isobutylene and p-methyl styrene, wherein said halogen is selected from bromine and chlorine, (2) about 25 to about 100 phr of silica comprised of aggregates of synthetic amorphous silica, and (3) a coupling agent having a moiety reactive with hydroxyl groups on the surface of said silica aggregates and another moiety interactive with at least one of said elastomers; wherein said tread base layer is not exposed at the surface of the groove and wherein said visually exposed non-black colored tread intermediate layer includes and extends from the bottom of said groove up to at least seventy percent of the distance from the bottom of said groove to the top of said groove; wherein said aggregates of synthetic amorphous silica for said non-black colored rubber layer are comprised of (A) aggregates of precipitated silica having hydroxyl groups on the surface thereof, and (B) pre-hydrophobated aggregates of precipitated silica having been pre-hydrophobated by treating silica in an aqueous colloidal form thereof with an alkylsilane or with both an organomercaptosilane and an alkylsilane in a weight ratio of said organomercaptosilane to said alkylsilane in a range of from 10/90 to 90/10; wherein said alkylsilane is of the general Formula (I) Xnâ€”Siâ€”R4-nâ€ƒâ€ƒ(I) wherein R is an alkyl radical having from one to 18 carbon atoms, n is a value of from 1 to 3 and X is a radical selected from chlorine, bromine and alkoxy radical as (OR1)â€”, wherein R1 is an alkyl radical selected from methyl and ethyl radicals, and where said organomercaptosilane is of the general formula (II): (X)n(R2O)3-nâ€”Siâ€”R3â€”SHâ€ƒâ€ƒ(II) wherein X is a radical selected from chlorine, bromine, and alkyl radicals having from one to 16 carbon atoms; wherein R2 is an alkyl radical having from one to 16 carbon atoms and R3 is an alkylene radical having from one to 16 carbon atoms; and n is a value from zero to 3; and wherein said non-black colored rubber layer also contains from zero to 20 phr of at least one organo phosphite, or from 0.5 to 20 phr of at least one organo phosphite where said non-black rubber layer includes said halogenated copolymer of isobutylene and p-methyl styrene, wherein said organo phosphite is selected from monophosphites selected from formula (III) and diphosphites selected from formula (IV) and diisodecyl pentearythritol diphosphite, distearyl pentaerythritol diphosphite and pentearythritol diphosphite: wherein each R4 radical is independently selected from alkyl radicals and phenyl radicals and alkyl substituted phenyl radicals; wherein said R4 alkyl radicals have from 1 to 18 carbon atoms, wherein R5 is a phenyl radical; and wherein R6 is selected from alkyl radicals having from 2 to 8 carbon atoms; wherein said organo phosphite is provided by one or more of the following: (A) by mixing said organo phosphite with said elastomer(s) and said synthetic silica, (B) by pre-reacting said halogenated copolymer of isobutylene and p-methyl styrene with said organo phosphite prior to blending said reinforcing filler therewith, (C) by pre-reacting said organo phosphite with an aqueous dispersion of colloidal silica particles from which a precipitated silica is recovered to form an organo phosphite/silica composite thereof, (D) mixing said organo phosphite with said elastomer(s) and said synthetic silica, according to any of said steps (A), (B) or (C), wherein said synthetic silica includes at least one of said pre-hydrophobated silica aggregates which has been pre-hydrophobated prior to mixing with said elastomers, (E) mixing said organo phosphite with said elastomer(s) and an alkylsilane of the said Formula (I) with said elastomer(s) and said synthetic silica, and (F) by pre-reacting said organo phosphite and said alkylsilane of Formula (I) with (1) said aggregates of synthetic precipitated silica or (2) an aqueous dispersion of colloidal silica particles from which a precipitated silica is recovered to form a silica composite thereof.