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—S—R5 (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 group, C4-C10-cycloalkoxy groups or alkyl polyether group —O—(R6—O)r—R7 where R6 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 R7 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 group, C7-C20-aralkyl group or halogen,
• R3 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,
• R4 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,
• R5 is hydrogen or a —C(═O)—R8 group with R8=hydrogen, a C1-C20-alkyl group, C6-C20-aryl groups, C2-C20-alkenyl group, C7-C20-aralkyl group,
• and n is 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 20:80-90:10.