Compounding silica-reinforced rubber with low volatile organic compound (VOC) emission

A method for making a mixture of alkoxy-modified silsesquioxanes comprising:

• (a) combining as a reaction mixture:
• (i) water;
• (ii) alcohol;
• (iii) an alkyltrialkoxysilane, an alkyltrichlorosilane, or a mixture thereof;
• and
• (iv) a hydrolysis and condensation catalyst;
• (b) allowing the reaction mixture to react for about 0.5 hours to about 200 hours;
• and
• (c) recovering the alkoxy-modified silsesquioxane,
• the mixture of alkoxy-modified silsesquioxanes consisting essentially of alkoxy-modified silsesquioxanes having an open structure with a reactive alkoxysilyl group, and being essentially free of closed caged polyhedral organosilsesquioxanes.

A vulcanizable rubber compound comprising

• (a) an elastomer;
• (b) a reinforcing filler comprising silica or a mixture thereof with carbon black;
• (c) a silica dispersing aid comprising an alkoxy-modified silsesquioxane that comprises one or more compounds selected from the group consisting of alkoxy-modified silsesquioxanes having the formula
• and mixtures thereof, wherein w, x and y represent mole fractions, y does not equal zero, either w or x but not both can be zero, and w+x+y=1.00,
• wherein R1, R2 and R3 are the same or different and selected from the group consisting of (i) H or an alkyl groups having one to about 20 carbon atoms, (ii) cycloalkyl groups having 3 to about 20 carbon atoms, (iii) alkylaryl groups having 7 to about 20 carbon atoms, and (iv) R5X, wherein X is selected from the group consisting of Cl, Br, SH, SaR6, NR62, OR6, CO2H, SCOR6, CO2R6, OH, olefins, epoxides, amino groups, vinyl groups, acrylates and methacrylates, wherein a=1 to about 8, R5 is selected from the group consisting of alkylene groups having one to about 20 carbon atoms, cycloalkylene groups having 3 to about 20 carbon atoms, and R4 and R6 are selected from the group consisting of alkyl groups having one to about 5 carbon atoms, cycloalkyl groups having 3 to about 20 carbon atoms, and alkylaryl groups having 7 to about 20 carbon atoms;
• and
• (d) a cure agent.

A pneumatic tire including at least one component comprising a vulcanized rubber that comprises a vulcanized rubber compound comprising

• (a) an elastomer;
• (b) a reinforcing filler comprising silica or a mixture thereof with carbon black;
• (c) a silica dispersing aid comprising an alkoxy-modified silsesquioxane that comprises one or more compounds selected from the group consisting of alkoxy-modified silsesquioxanes having the formula
• and mixtures thereof, wherein w, x and y represent mole fractions, y does not equal zero, either w or x but not both can be zero, and w+x+y=1.00,
• wherein R1, R2 and R3 are the same or different and selected from the group consisting of (i) H or an alkyl groups having one to about 20 carbon atoms, (ii) cycloalkyl groups having 3 to about 20 carbon atoms, (iii) alkylaryl groups having 7 to about 20 carbon atoms, and (iv) R5X, wherein X is selected from the group consisting of Cl, Br, SH, SaR6, NR62, OR6, CO2H, SCOR6, CO2R6, OH, olefins, epoxides, amino groups, vinyl groups, acrylates and methacrylates, wherein a=1 to about 8, R5 is selected from the group consisting of alkylene groups having one to about 20 carbon atoms, cycloalkylene groups having 3 to about 20 carbon atoms, and R4 and R6 are selected from the group consisting of alkyl groups having one to about 5 carbon atoms, cycloalkyl having 3 to about 20 carbon atoms, and alkylaryl groups having 7 to about 20 carbon atoms;
• and
• (d) a cure agent.

A method for producing a vulcanizable rubber composition with low VOC release during compounding comprising:

• (a) forming a mixture by mixing together at a mixing temperature:
• (i) an elastomer;
• (ii) a reinforcing filler comprising silica or a mixture thereof with carbon black;
• and
• (iii) a silica dispersing aid comprising an alkoxy-modified silsesquioxane that comprises one or more compounds selected from the group consisting of alkoxy-modified silsesquioxanes having the formula
• and mixtures thereof, wherein w, x and y represent mole fractions, y does not equal zero, either w or x but not both can be zero, and w+x+y=1.00,
• wherein R1, R2 and R3 are the same or different and selected from the group consisting of (i) H or an alkyl groups having one to about 20 carbon atoms, (ii) cycloalkyl groups having 3 to about 20 carbon atoms, (iii) alkylaryl groups having 7 to about 20 carbon atoms, and (iv) R5X, wherein X is selected from the group consisting of Cl, Br, SH, SaR6, NR62, OR6, CO2H, SCOR6, CO2R6, OH, olefins, epoxides, amino groups, vinyl groups, acrylates and methacrylates, wherein a=1 to about 8, R5 is selected from the group consisting of alkylene groups having one to about 20 carbon atoms, cycloalkylene groups having 3 to about 20 carbon atoms, and R4 and R6 are selected from the group consisting of alkyl groups having one to about 5 carbon atoms, cycloalkyl groups having 3 to about 20 carbon atoms, and alkylaryl groups having 7 to about 20 carbon atoms;
• (b) cooling the mixture to a temperature below the mixing temperature;
• and
• (c) mixing a vulcanizing agent into the mixture at a temperature that will not initiate vulcanization.