TIRE TREAD WITH INCOMPATIBLE RUBBERS
A tread for a tire, the tread comprising a rubber composition that is based upon a cross-linkable elastomer composition, the cross-linkable elastomer composition comprising, per hundred parts by weight of rubber (phr), a high-Tg rubber being a highly unsaturated diene elastomer having a glass transition temperature of between −30° C. and 0° C., a low-Tg rubber being a highly unsaturated diene elastomer having a glass transition temperature of between −110° C. and −60° C. The high-Tg and the low-Tg elastomers are incompatible and this provides, among other advantages, improved snow traction of the tread when compared to tire treads having lower Tg.
1 . A tread for a tire, the tread comprising a rubber composition that is based upon a cross-linkable elastomer composition, the cross-linkable elastomer composition comprising, per hundred parts by weight of rubber (phr):
a high-Tg rubber being a highly unsaturated diene elastomer having a glass transition temperature of between −30° C. and 0° C.;
a low-Tg rubber being a highly unsaturated diene elastomer having a glass transition temperature of between −110° C. and −60° C., wherein the high-Tg and the low-Tg elastomers are incompatible;
a reinforcing filler; and
a curing system.
2 . The tread of claim 1 , wherein the high-Tg rubber is selected from a synthetic polyisoprene rubber, an isoprene/styrene copolymer, a styrene/butadiene copolymer and combinations thereof.
3 . The tread of claim 1 , wherein the low-Tg rubber is selected from a polybutadiene, synthetic isoprene rubber, an isoprene/styrene copolymer, a styrene/butadiene copolymer, a natural rubber and combinations thereof.
4 . The tread of claim 1 , wherein the elastomer composition comprises between 55 phr and 90 phr of the low-Tg rubber.
5 . The tread of claim 1 , wherein the elastomer composition comprises between 10 phr and 45 phr of the high-Tg rubber.
6 . The tread of claim 1 , wherein the elastomer composition comprises between 70 phr and 130 phr of the reinforcing filler.
7 . The tread of claim 6 , wherein the reinforcing filler is silica and no more than 20 phr of carbon black.
8 . The tread of claim 1 , wherein the elastomer composition comprises between 80 phr and 120 phr of the reinforcing filler.
9 . The tread of claim 1 , wherein the reinforcing filler comprises carbon black, silica and combinations thereof.
10 . The tread of claim 1 , wherein the high-Tg and the low-Tg rubbers are both a styrene/butadiene copolymer.
11 . The tread of claim 1 , wherein the high-Tg rubber is a styrene/butadiene copolymer and the low-Tg rubber is a natural rubber.
12 . The tread of claim 1 , wherein the high-Tg rubber is a styrene/butadiene copolymer and the low-Tg rubber is a polybutadiene rubber.
13 . The tread of claim 1 , wherein the elastomer composition further comprises a plasticizing system that is selected from an oil, a plasticizing resin or combinations thereof.
14 . The tread of claim 13 , wherein the plasticizing system is the oil.
15 . The tread of claim 13 , wherein the plasticizing system comprises less than 15 phr of the resin.
16 . The tread of claim 13 , wherein the plasticizing system comprises between 5 phr and 50 phr of the resin.