Patent ID: 8138365

Claim:
A process for preparing an organosilane of general formula I: [R(R)(R′O)Si—R″—] 2 S m I wherein: R is the same or different and is a C 1 -C 8 -alkyl, C 1 -C 8 -alkenyl, C 1 -C 8 -aryl, C 1 -C 8 -aralkyl group, or an OR′ group, R′ is the same or different and is a C 1 -C 22 branched or unbranched monovalent alkyl or alkenyl group, an aryl group, an aralkyl group, a hydrogen, an alkyl ether group O—(CR III 2 )—O-Alk or O—(CR III 2 ) y —O-Alk or an alkyl polyether group O—(CR III 2 O) y -Alk or O—(CR III 2 —CR III 2 —O) y -Alk, where y=2-20, R III is independently H or an alkyl group and Alk is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic monovalent C 1 -C 22 hydrocarbon group, R″ is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C 1 -C 30 hydrocarbon group which is optionally substituted by F, Cl, Br, I, HS, NH 2 or NHR′, m is a mean sulfur chain length of from 1.5 to 4.5, said process comprising reacting a (haloorganyl)alkoxysilane of formula II: wherein R, R′ and R″are each as defined above and Hal is chlorine, bromine, fluorine or iodine; with a hydrous sulfurizing reagent comprising 15 to 60% by weight of water and alkali metal hydrogensulfide, metal sulfide Me 2 S, metal polysulfide Me 2 S g or any desired combinations thereof, where Me=alkali metal, NH 4 or (alkaline earth metal) 1/2 , and g=1.5-8.0, and, optionally, additionally with sulfur and/or with H 2 S in a solvent consisting of an alcohol selected from the group consisting of methanol, ethanol, and propanol and, optionally, water, wherein the alkali metal hydroxide content of all feedstocks is less than 0.44% by weight and wherein said process results in a product with greater than a 90% yield and a monomer content of greater than 90%.