Triorganotin lithium, process to prepare same and anionic polymerization initiated therewith

A process for producing a solution of hexaorgano substituted-ditin comprising:

• combining in the presence of a solvent a triorgano substituted-tin halide with an effective amount of lithium metal to form a solution primarily of hexaorgano substituted-ditin and lithium halide, said solvent being one or more solubilizing solvents in an amount such that the mole ratio of said solubilizing solvents to the triorgano substituted-tin halide is 3.0 or less, and
• separating the lithium halide which precipitates from the hexaorgano substituted-ditin,
• wherein the resulting hexaorgano substituted-ditin solution has less than 3000 parts of halide per million parts of said hexaorgano substituted-ditin.

A process for anionically polymerizing one or more monomers into a polymer with reduced hysteresis and low levels of volatile organotin by-products when said polymer is compounded in carbon black-filled elastomers, said process comprising:

• reacting a triorgano substituted-tin lithium initiator solution with at least one diene monomer and optionally a monovinyl aromatic monomer to form a polymer with triorgano substituted-tin groups on at least one end, wherein said initiator solution has a residual halide content of less than 3000 parts based on one million parts of said triorgano substituted-tin lithium initiator, wherein the amount of said triorgano substituted-tin lithium initiator is at least 90 percent by weight based on all of the tin containing species in said initiator, wherein said organo groups of said initiator independently is an alkyl or a cycloalkyl having from 1 to 12 carbon atoms or an aryl or an alkyl substituted aryl having from 6 to 15 carbon atoms, and wherein said diene has from 4 to 12 carbon atoms and wherein said monovinyl aromatic monomer has from 8 to 18 carbon atoms.