Processable silica-filled rubber stocks with reduced hysteresis

Abstract

A processable rubber stock is produced by the preparation of a silica-filled, vulcanized elastomeric compound comprising mixing an elastomer with an amorphous silica filler, a processing aid comprising fatty acid ester of a polyol, optionally an additional mineral filler, and a cure agent. The elastomer is preferably a diene monomer homopolymer or a copolymer of at least one diene and at least one monovinyl aromatic monomer. By effecting vulcanization, a vulcanized elastomeric compound is produced containing good physical properties for use as tread stock for a pneumatic tire.

We claim  
     
         1 . A process for the preparation of a silica-filled, vulcanized elastomeric compound comprising: 
 mixing an elastomer with an amorphous silica filler, a processing aid comprising a fatty acid ester of a polyol and a cure agent, and, effecting vulcanization.    
     
     
         2 . A process as in  claim 1  wherein the elastomer is a diene memos homopolymer or a copolymer of a diene monomer and a monomer selected from the group consisting of a monovinyl aromatic monomer and a triene monomer.  
     
     
         3 . A process as in  claim 1  wherein the processing aid is selected from the group consisting of sorbitan dioleate, sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate, sorbitan laurate, sorbitan palmate and sorbitan stearate and polyoxyethylene derivatives thereof.  
     
     
         4 . A process as in  claim 1  wherein the processing aid is sorbitan monooleate.  
     
     
         5 . A process as in  claim 1  wherein the processing aid is a fatty acid ester of a glycol.  
     
     
         6 . A process as in  claim 1  wherein the elastomer is styrene butadiene rubber.  
     
     
         7 . A process as in  claim 1  including mixing the elastomer with a filler selected from the group consisting of mica, talc, urea and clay.  
     
     
         8 . A vulcanizable silica-filled compound comprising an elastomer, a silica filler, a processing aid comprising a fatty acid ester of a polyol and a cure agent.  
     
     
         9 . The vulcanizable silica-filled compound of  claim 8  wherein the elastomer is a diene monomer homopolymer.  
     
     
         10 . The vulcanizable silica-filled compound of  claim 8  wherein the elastomer is a copolymer of at least one diene and at least one monovinyl aromatic monomer.  
     
     
         11 . The vulcanizable silica-filled compound of  claim 10  wherein the elastomer is styrene butadiene rubber.  
     
     
         12 . The vulcanizable silica-filled compound of  claim 8  wherein the processing aid is selected from the group consisting of sorbitan monooleate, sorbitan dioleate, sorbitan trioleate, sorbitan sesquioleate, sorbitan laurate, sorbitan Pate, sorbitan stearate, and polyoxyethylene derivatives thereof.  
     
     
         13 . The vulcanizable silica-filled compound of  claim 8  wherein the processing aid is sorbitan monooleate.  
     
     
         14 . The vulcanizable silica-filled compound of  claim 8  wherein the processing aid is a fatty acid ester of a polyhydroxy alcohol.  
     
     
         15 . The vulcanizable silica-filled compound of  claim 8  wherein the silica filter has a surface area of about 32 to about 400 m 2 /g.  
     
     
         16 . The vulcanizable silica-filled compound of  claim 8  wherein the silica filler has a pH of about 5.5 to about 7.  
     
     
         17 . The vulcanizable silica-filled compound of  claim 8  further containing a carbon black filler.  
     
     
         18 . The vulcanizable silica-filled compound of  claim 8  wherein silica is present in an amount of about 1 phr to about 100 phr.  
     
     
         19 . The vulcanizable silica-filled compound of  claim 8  further containing a filler selected from the group consisting of mica, talc, urea and clay.  
     
     
         20 . The vulcanizable silica-filled compound of  claim 8  further containing a natural rubber.  
     
     
         21 . A pneumatic tire comprising tread stock vulcanized from the vulcanizable silica-filled compound of  claim 8 .  
     
     
         22 . A pneumatic tire comprising tread stock vulcanized from the vulcanizable silica-filled compound of claim  19 .