| abstract |
The present invention relates to an anionic polymerization technique for synthesizing functionalized rubbery polymers containing polysiloxane that have excellent characteristics for utilization in (a) tire tread compounds that are highly loaded with silica, (b) shiny tire side-wall compounds, and (c) tire building bladders having improved mold release characteristics. The rubbery polymers of this invention can optionally be coupled with tin halides or silicon halides to further improve the characteristics of the rubber for use in tire tread compounds. The present invention more specifically discloses a process for synthesizing a rubbery polymer that comprises (1) polymerizing at least one conjugated diolefin monomer to produce a living rubbery polymer, wherein said polymerization is optionally carried out in the presence of a polar modifier, wherein said polymerization is an anionic polymerization that is initiated with an alkylsilyloxy protected functional lithium initiator having a structural formula selected from the group consisting: n n n wherein X represents a group IVa element selected from the group consisting of carbon, silicon, germanium, and tin, wherein Y represents phosphorous or nitrogen, wherein R represents alkyl groups that can be the same or different, wherein the alkyl groups contain from 1 to about 8 carbon atoms, and wherein A represents an alkylene group containing from 1 to about 8 carbon atoms; (2) adding a hexaalkylcyclotrisiloxane monomer to the living rubbery polymer; (3) allowing the hexaalkylcyclotrisiloxane monomer to polymerize to produce a living polysiloxane containing rubber; and optionally, (4) reacting the living polysiloxane containing rubber with a coupling agent selected from the group consisting of tin halides and silicon halides to produce a coupled polysiloxane containing rubber. |