Tire tread rubber compositions
AssigneeThe B. F. Goodrich Company
InventorRobert W. Layer
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Abstract
A synthetic rubber (SR) tire tread of styrene-butadiene rubber (SBR) and butyl rubber which SR is essentially free of natural rubber (NR), upon vulcanization with sulfur in the presence of a combination of sulfenamide accelerators, provides excellent oxidative stability, resistance to hardening, and flex resistance, despite increasing the level of sulfur to an amount in the range from 2.0-3.0 phr, as long as the total amount of sulfenamide accelerators is less than 2.0 phr and there is more TCS than BTS. The crosslink network generated by the use of TCS in combination with BTS, which combination produces poor oxidation stability in a predominantly NR containing rubber, is not produced in SR.
Claims7
In a synthetic tread rubber compound essentially free from natural rubber, which compound yields a vulcanizate particularly adapted for use in a passenger tire tread which is substantially free from a proclivity to reversion when vulcanized with sulfur in the presence of a combination of benzothiazole sulfenamide (BTS) and tread compound accelerators, said tread rubber compound comprising,
- (i) 100 parts of a synthetic rubber consisting essentially of at least 60 parts styrene-butadiene rubber, the remaining being another synthetic high unsaturation rubber;
- (ii) from 2 to 2.8 phr of sulfur;
- (iii) from 0.3 to 1.5 phr of a benzothiazole sulfenamide;
- and,
- (iv) from 0.5 to 1.5 phr of a thiocarbamyl sulfenamide (TCS);
- provided the combined amount of sulfenamides is more than 1 phr but less than 2 phr, and there is more thiocarbamyl sulfenamide than benzothiazole sulfenamide,
- whereby the tensile strength is maintained without increasing the modulus or sacrificing oxidative stability.
Dependencies are inferred from the claim text.