This invention relates to a process for producing a free radical control agent
of the structural formula:
##STR1##
wherein Z is selected from the group consisting of
##STR2##
wherein R1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl
or phenyl; wherein R2 is an alkoxy group of 1 to 8 carbon atoms or a
cycloalkoxy group of 5 to 8 carbon atoms; wherein Alk is a divalent hydrocarbon
of 1 to 18 carbon atoms; and wherein Y represents a functional group that is capable
of activating a vinylic carbon toward free radical addition; said process comprising
the steps of (1) reacting a mercaptosilane of the structural formula: Z-Alk-SH
with carbon disulfide in the presence of a phase transfer catalyst and an alkali
metal hydroxide to produce a trithiocarbonate salt; and (2) reacting the trithiocarbonate
salt with a halogen containing compound of the structural formula X-Y to produce
the free radical control agent, wherein X represents a halogen atom. Such free
radical control agents are capable of covalently bonding to silica/silicate surfaces
and are of particular benefit in producing rubbery compounds that will be loaded
with silica fillers, such as tire tread rubbers.
