Method for producing organosilanes

A process for preparing an organosilane of general formula I:

• [R(R)(R′O)Si—R″—]2Sm I
• wherein:
• R is the same or different and is a C1-C8-alkyl, C1-C8-alkenyl, C1-C8-aryl, C1-C8-aralkyl group, or an OR′ group,
• R′ is the same or different and is a C1-C22 branched or unbranched monovalent alkyl or alkenyl group, an aryl group, an aralkyl group, a hydrogen, an alkyl ether group O—(CRIII2)—O-Alk or O—(CRIII2)y—O-Alk or an alkyl polyether group O—(CRIII2O)y-Alk or O—(CRIII2—CRIII2—O)y-Alk, where y=2-20, RIII is independently H or an alkyl group and Alk is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic monovalent C1-C22 hydrocarbon group,
• R″ is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group which is optionally substituted by F, Cl, Br, I, HS, NH2 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 Me2S, metal polysulfide Me2Sg or any desired combinations thereof, where Me=alkali metal, NH4 or (alkaline earth metal)1/2, and g=1.5-8.0, and, optionally, additionally with sulfur and/or with H2S 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%.