Silica-reinforced rubber compounded with blocked mercaptosilanes and alkyl alkoxysilanes

A pneumatic tire comprising a component produced from a sulfur-vulcanized elastomeric compound having an improved physical property, the compound comprising an elastomer;

• a reinforcing filler comprising silica or a mixture thereof with carbon black;
• an alkyl alkoxysilane;
• a blocked mercaptosilane silica coupling agent comprising a mercaptosilane moiety and a blocking moiety, wherein the weight ratio of the mercaptosilane moiety to the alkyl alkoxysilane is about 0.001:1 to about 0.20:1;
• a deblocking agent;
• and a cure package, wherein the elastomer, the silica, the alkyl alkoxysilane, and the blocked mercaptosilane are mixed together, in the absence of the deblocking agent and the cure package, at a temperature of about 160° C. to about 185° C.,
• and wherein the compound exhibits an improved physical property compared to a similar compound containing the alkyl alkoxysilane and a non-blocked mercaptosilane.

A method for preparing a sulfur-vulcanized elastomeric compound, having an improved physical property, comprising the steps of:

• (a) mixing together at a temperature of about 160° C. to about 185° C., in the absence of added sulfur, cure agents and deblocking agents, (i) an elastomer, (ii) a reinforcing filler comprising silica or a mixture thereof with carbon black, (iii) an alkyl alkoxysilane, (iv) a blocked mercaptosilane silica coupling agent comprising a mercaptosilane moiety and a blocking moiety, wherein the weight ratio of the mercaptosilane moiety to the alkyl alkoxysilane is about 001:1 to about 0.20:1;
• (b) allowing the mixture to cool below the mixing temperature;
• (c) mixing the mixture obtained in step (b), at a temperature lower than a vulcanization temperature, with a deblocking agent and a cure package, wherein the deblocking agent is added in a separate substep or is added with the cure package;
• (d) curing the mixture obtained in step (c),
• wherein the compound exhibits an improved physical property compared to a similarly prepared compound containing the alkyl alkoxysilane and a non-blocked mercaptosilane.