Silane mixtures and processes for preparation thereof

Silane mixture comprising a silane of the formula I

• (R1)y(R2)3-ySi—R3—(S—R4)n—Sx—(R4—S)n—R3—Si(R1)y(R2)3-y (I)
• and a silane of the formula II
• (R1)y(R2)3-ySi—R3—(S—R4)z—S—R3—Si(R1)y(R2)3-y (II)
• where R1 are the same or different and are C1-C10-alkoxy groups, phenoxy groups, C4-C10-cycloalkoxy groups or alkyl polyether groups —O—(R5—O)r—R6 where R5 are the same or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, r is an integer from 1 to 30, and R6 is an unsubstituted or substituted, branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl group,
• R2 are the same or different and are C6-C20-aryl groups, C1-C10-alkyl groups, C2-C20-alkenyl groups, C7-C20-aralkyl groups or halogen,
• R3 are the same or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon groups,
• R4 are the same or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon groups,
• and x is a number from 2 to 10,
• n are the same and are 0, 1, 2 or 3, y are the same or different and are 1, 2 or 3, z is 1, 2 or 3, and the molar ratio of silane of the formula I to silane of the formula II is 19:81-81:19.