Butyl rubber compounds comprising a mixed modifier system

Abstract

Rubber compounds containing a halobutyl elastomer, at least one additional elastomer, a mineral filler and at least a three component mixed modifier system comprising a silane compound, a phosphine compound and an additive containing at least one hydroxyl group and a functional group containing a basic amine. A process for preparing the compounds is also disclosed. The compounds are particularly useful in tire treads and exhibit improved processability, traction, rolling resistance and wear properties.

What is claimed is: 
     
         1 . A rubber compound comprising:
 a halobutyl elastomer,   at least one additional elastomer,   a mineral filler, and   a mixed modifier system comprising:
 a silane; and 
 1.6 to 3.7 phr of triphenylphosphine. 
   
     
     
         2 . The rubber compound according to  claim 1 , wherein the halobutyl elastomer is selected from a chlorobutyl elastomer or a bromobutyl elastomer. 
     
     
         3 . The rubber compound according to  claim 1 , wherein the halobutyl elastomer comprises a halogenated copolymer of at least an isoolefin and a conjugated diolefin. 
     
     
         4 . The rubber compound according to  claim 3 , wherein the isoolefin comprises isobutylene and the conjugated diolefin comprises isoprene. 
     
     
         5 . The rubber compound according to  claim 1 , wherein the halobutyl elastomer comprises:
 a halogenated terpolymer of an isoolefin,   a conjugated diolefin, and   a vinyl aromatic monomer.   
     
     
         6 . The rubber compound according to  claim 5 , wherein:
 the isoolefin comprises isobutylene,   the conjugated diolefin comprises isoprene, and   the vinyl aromatic monomer comprises p-methylstyrene.   
     
     
         7 . The rubber compound according to  claim 1 , wherein the at least one additional elastomer comprises BR, SBR, NBR, NR, ENR. or mixtures thereof. 
     
     
         8 . The rubber compound according to  claim 1 , wherein the mineral filler comprises silica. 
     
     
         9 . The rubber compound according to  claim 8 , wherein the mineral filler comprises a highly dispersive silica. 
     
     
         10 . The rubber compound according to  claim 1 , wherein the silane comprises an aminosilane or a sulphur-containing silane. 
     
     
         11 . The rubber compound according to  claim 10 , wherein the silane is selected from the group consisting of bis[3-(triethoxysilyl)propyl]-monosulfane, bis[3-(triethoxysilyl)propyl]disulfane, bis[3-(triethoxysilyl)propyl]trisulfane, bis[3-(triethoxysilyl)propyl]tetrasulfane, bis[2-(triethoxysilyl)ethyl]-tetrasulfane, 3-(triethoxysilyl)propanthiol, and mixtures thereof. 
     
     
         12 . The rubber compound according to  claim 1 , the silane is present in the mixed modifier in an amount of 0.1 to 15.0 phr. 
     
     
         13 . The rubber compound according to  claim 13 , wherein the silane is bis[3-(triethoxysilyl)-propyl]-tetrasulfane. 
     
     
         14 . The rubber compound according to  claim 1 , having a tan delta at 0° C. greater than 0.325, a tan delta at 60° C. less than 0.120, an abrasion volume loss (DIN) less than 165 mm 3 , a tensile at break values greater than 13.0 MPa, and a Mooney Scorch (MS LR @ 125° C., t05 (min)) of >30. 
     
     
         15 . The rubber compound according to  claim 1 , wherein:
 the halobutyl elastomer is a chlorobutyl elastomer or a bromobutyl elastomer, and is a halogenated polymer comprising isobutylene and isoprene;   the at least one additional elastomer comprises butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), natural rubber (NR), epoxidized natural rubber (ENR). or mixtures thereof;   the mineral filler comprises a highly dispersive silica, and   the mixed modifier system comprises silane in an amount of 0.1 to 15.0 phr, and the silane is selected from the group consisting of bis[3-(triethoxysilyl)propyl]-monosulfane, bis[3-(triethoxysilyl)propyl]disulfane, bis[3-(triethoxysilyl)propyl]trisulfane, bis[3-(triethoxysilyl)propyl]tetrasulfane, bis[2-(triethoxysilyl)ethyl]-tetrasulfane, 3-(triethoxysilyl)propanthiol, and mixtures thereof.   
     
     
         16 . The rubber compound according to  claim 15 , wherein:
 the halobutyl elastomer is a halogenated terpolymer of isobutylene, isoprene, and p-methylstyrene;   the at least one additional elastomer comprises a butadiene rubber and a styrene-butadiene rubber;   the silane is bis[3-(triethoxysilyl)-propyl]-tetrasulfane; and   the rubber has a tan delta at 0° C. greater than 0.325, a tan delta at 60° C. less than 0.120, an abrasion volume loss (DIN) less than 165 mm 3 , a tensile at break values greater than 13.0 MPa, and a Mooney Scorch (MS LR @ 125° C., t05 (min)) of >30.   
     
     
         17 . A process for preparing a rubber compound, the process comprising admixing a halobutyl elastomer, at least one additional elastomer, a mineral filler, and a mixed modifier system comprising:
 a silane, and   1.6 to 3.7 phr of triphenylphosphine.   
     
     
         18 . The process according to  claim 16 , further comprising:
 premixing the silane and triphenylphosphine of the mixed modifier system as a first mixture, and   premixing the halobutyl elastomer, the at least one additional elastomer, and the mineral filler as a second mixture, and   admixing the first mixture with the second mixture.   
     
     
         19 . A rubber compound comprising a halobutyl elastomer, at least one additional elastomer, a mineral filler, and a mixed modifier system comprising:
 1.4 to 4.2 phr of a silane selected from the group consisting of aminosilanes, vinyl silanes, or sulphur-containing silanes, and   1.32 to 3.97 phr of triphenylphosphine.   
     
     
         20 . The rubber compound according to  claim 19 , wherein:
 the halobutyl elastomer is a halogenated copolymer of isobutylene and isoprene,   the at least one additional elastomer comprises a butadiene rubber, and   the silane is bis[3-(triethoxysilyl)-propyl]-tetrasulfane.