Silane mixtures and processes for preparation thereof The invention relates to silane mixtures and to processes for preparation thereof. EP 0670347 and EP 0753549 disclose rubber mixtures comprising at least one crosslinker, a filler, optionally further rubber auxiliaries and at least one reinforcing additive of the formula R1R2R3Si - X1 - (-Sx - Y - )m - (- Sx - X2 - SiR1R2R3)n In addition, EP 1375504 discloses silanes of the formula (R,0)(3.p)(R2)pSi-R3-Sm-R'1-(Sr1-R<)q-Sm-R3-Si(Rz)p{OR1)^P) WO 2005/059022 discloses rubber mixtures comprising a silane of the formula [R^R'Si-RS-S-RO-RMR1- Additionally known are rubber mixtures comprising a Afunctional silane and a further silane of the formula (Y)G{Z) {WO 2012/092062) and rubber mixtures comprising bistriethoxysilylpropyl polysulfide and bistriethoxysilylpropyl monosulfide (EP1085045). EP 1928949 discloses a rubber mixture comprising the silanes (HsC20)3Si-(CH2)3-X-(CH2)6-S2-(CH2)6-X-{CH2)3-Si(OC2H5)3 and/or CH5C20)3Si-(CH2)3-X-(CHz)io-S2-(CH2),o-X-(CH2)3-Si(OC2H5)o and(H5C20)3Si-{CH2)3-Sm-(CHz)3-Si(OC2Hs)3 In addition, silane mixtures comprising silanes of the formula RWR^i-X^Si-X^SiR'RZR3 and silanes of the formula R4R5R6Si-X3-(-SrY-)m-Sy-X',-SiR7RBR9 are known from EP 2557116. It is an object of the present invention to provide silane mixtures having improved processing characteristics and improved viscosity, higher crosslinking yields, higher strengthening and improved rolling resistance in rubber mixtures compared to silanes known from the prior art, The invention provides a silane mixture comprising a silane of the formula I {R1)y-, - CH2CH(CH3)-, -CH{CH3)CH2-, -C(CHa)2-. -CH(C2H5)-, -CH2CHZCH(CH3)-, -CH(CH3)CH2CH2-, -CHjCHfCHiJCHr, -CH2CH2CH2CH2CHr, -CH,CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2-,-CH2CH!CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2CH2CH2-,-CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-,- CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-,- CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-,- CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-. -CH2CHzCH2CH2CH2CHzCH2CHzCHzCH3CHjCH2CH2CHzCH2CHzCH;CH2- R1 may preferably be methoxy or ethoxy, Silanes of the formula I may preferably be: (EtO)3Si-CHz-S2-CH2-Si(OEt)3, (EtO)3Si-2-S-(C H2)2-S2-{CH02-S-(C H2)2-Si{0 Et)Sl CEtO)3Si-(CH2)3-S-(CH2)2-S2-CCH2)2-S-(CH2)j-Si(OEt)31 (EtOhSi-CH^S-tCH^s-SrtCHzh-S-CHj-SifOEtJj, (EtO)jSi-(CH2}2-S-(CH2)3-SHCH2)3-S-(CH2)i-Si{OEt)3l (EtO)3Si-(CH2)3-S-(CH2)j-S2-(CH2)3-S-(CH2)3-Si(OEt)3l (EtO)3Si-CH2-S-(CH;)<-S2-(CH2)4-S-CH2-Si(OEt)3, (EtO)3Si-(CHz)2-S-(CH2)4-S2-(CH2)4-S-(CHz)2-Si(OEt)3l (EtO)3S(-(CH2)3-S-(CH2)4-S2-(CH2)q-S-(CH2)3-Si{OEt)3l (EtO)3Si-CH2-S-(CH2)5-S2-{CH2)5-S-CH2-Si(OEt)3, CEtO)3Si-(CH2)2-S-(CH2)5-S2-{CH2)5-S-(CH2)2-Si(OEt)3l {EtO)3St-(CH2)^S-(CH2)5-S2-(CH2)5-S-(CH2)3-Si(OEt)3l (EtO)3Si-CH2-S-(CH2)6-S;-CCH2)8-S-CH2-Si(OEt)31 (EtO)3SJ-(CH2)i-S-(CH2)e-S2-(CH2)6-S-(CH2)2-Si(OEt)3l (EtO)3Sh(CH2)3-S-(CHz)6-Sz-(CH2)s-S-(CH2)3-Si{OEt)3. Especially preferred is the silane of the formula I (EtO)3Si-(CH2)3-S-(CH2)6-Sr(CHj)B-S-(CH2)3-Si(OEt)3. Silanes of the formula II may preferably be: (EtO)jSi-CH2-S-CH2-S-CH2-Si{OEt)3, (EtO)iSi-(CH2)z-S-CHz-S-(CH2)2-Si(OEt)3l (EtO)3Si-(CH2)3-S-CH2-S-{CHj)3-Si(OEt)3, (EtO)jSi-CH 2-S- (C Hijz-S-C H2-Si(OEt)3, (ElO)3Si-{CH2)2-S-(CH2)2-S-(CH2)2-Si(OEt)3, (EtO)3Si-(C H2)3-S-(C H2)2-S-{CH2)3-Si(OEt)3, (EtO)3Si-CH2-S-(CH2)3-S-CH2-Si(OEt)3, (EtO)3Si-(CH2)2-S-(CH2)3-S-(CH2)2-Si{OEt)3l (EtO)3SKCH2)3-S-(CH2)3-S-(CHz)3-Si(OEt)3, (EtO)3Si-CH2-S-(CH2)*-S-CH2-Si(OEt)3, (EtO)3Si-CCH2)2-S-(CH2)4-S-(CH2)2-Si(OEt)3. CEtO)3Si-(CHi)3-S-(CH2)<-S-{CH2)3-Si(OEt)31 (EIO)3Si-CH2-S-(CH2)5-S-CHi-Si(OEt)3, (EtO)3Si-(CH2)2-S-(CH2)5-S-{CH2)2-Si(OEt)3, {EtO)3Si-(CH2)3-S-{CH2)5-S-CCH2)3-Si{OEt)3, (EtO)3Si-CH2-S-(CH2)6-S-CH2-Si(OEt)3l (EtO)3Si-(CH2)rS-(CH2)6-S-(CH2)rSi(OEt)3, (EtO)3Si-(CH2)3-S-(CH2)6-S-(CHz)3-Si 99% in ,3C NMR) was obtained as a clear liquid. Comparative Example 3: bis(triethoxysilylpropyl) disulfide from Evonik Industries AG* Comparative Example 4: bis(triethoxysilylpropyl) sulfide To a solution of chloropropyltriethoxysilane (361 g; 1.5 mol; 1.92 eq) in ethanol (360 ml) was added NajS (61 5 g; 0 78 mol; 1 00 eq) in portions at such a rate as to not exceed 60°C. Completion of addition was followed by heating at reflux for 3 h, before leaving to cool to room temperature The reaction product was freed of precipitated salts by filtration. By distillative purification (0.04 mbar, 110°C), it was possible to obtain the product (yield: 73%, purity. > 99% by 13C NMR) as a clear liquid. Comparative Example 5: 4.3 parts by weight of Comparative Example 3 together with 2.6 parts by weight of Comparative Example 4 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed. This mixture corresponds to a molar ratio: silane ol the formula I; 60% (EtO)3Si(CH2)3Sz(CH2)3Si(OEt)3 and silane of the formula II: 40% (EtO)3Si(CH2)3S(CH2)3Si(OEt}3 Comparative Example 6: 2.9 parts by weight of Comparative Example 3 together with 3.8 parts by weight of Comparative Example 4 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed. This mixture corresponds to a molar ratio: silane of the formula I: 40% (EtO)3Si(CHJ)3S2(CH2)3Si(OEt)3 and silane of the formula II: 60% (EtO)sSi(CH2)3S(CH2)3Si(OEt)3 Comparative Example 7: 1.4 parts by weight of Comparative Example 3 together with 5 1 parts by weight of Comparative Example 4 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed. This mixture corresponds to a molar ratio: silane of the formula I: 20% (EtO)3Si(CH2)3S2(CH!)3Si(OEt)3 and silane of the formula II: 80% (EtO)3Si(CH2)3S(CH2)3Si(OEt)3. Example 1: 47,2 g of Comparative Example 1 together with 9.2 g of Comparative Example 2 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed This mixture corresponds to a molar ratio: silane of the formula I: 75% (EtO)3Si(CH2)3S(CHi)aSE(CHa)BS(CH3}3Si(pEth and silane of the formula I!: 25% {EtO)3Si(CH2)3S(CH2)8S(CHI)aSi(OEt)3. Example 2: 46.8 g of Comparative Example 1 together with 24 3 g of Comparative Example 2 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed. This mixture corresponds to a molar ratio: silane of the formula I: 57% (EtO)3SI(CH2)3S(CH2)6S2(CH2)aS(CH2)3SI(OEt)3 and silane of the formula II: 43% (EtO)3Si(CH2)3S(CH2)6S(CH2)jSi(OEt)3. Example 3: 45 6 g of Comparative Example 1 together with 36 0 g of Comparative Example 2 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 urn) and mixed. This mixture corresponds to a molar ratio, silane of the formula I: 47% (EtO)3Si(CH2)3S(CH2)6S2(CH2)6S(CH2)3Si(OEt)3 and silane of the formula II: 53% (EtObSi(CH2)3S(CH2)6S(CH2)3Si(OEt)3, Example 4: NaOEt (21% in EtOH; 1562 g, 4,820 mol) was metered into mercaptopropyltriethoxysilane (1233 g; 5.170 mol) over the course of 1 h while stirring at room temperature. On completion of addition, the reaction mixture was heated at reflux for 2 h and then left to cool to room temperature. The intermediate formed was metered into 1,6-dichlorohexane (801 7 g; 5.170 mol) that had been heated to 80°C over the course of 30 min. On completion of addition, the reaction mixture was heated at reflux for 3 h. before being left to cool to room temperature, The reaction mixture was filtered and the filtercake was rinsed with EtOH The volatile constituents were removed under reduced pressure and the 1-chloro-6-thiopropyltriethoxysilylhexane intermediate (yield: 88%, molar ratio: 66% 1-chloro-6-thiopropyltriethoxy8ilylhexane, 34% bis(thiopropyltriethoxysilyl)hexane; % by weight: 56% by weight of 1-chloro-6-thlopropyltriethoxysilylhexane, 44% by weight of 1,6-bis(thiopropyltnethoxysilyl)hexane) was obtained, Example 5: A solution of NaSH (40% in water; 46,01 g; 0 3283 mol; 1 044 eq.) and Na2C03 (38.44 g; 0 3627 mol; 1,153 eq.) in water (123 2 g; 6-837 mol; 21.74 eq ) was heated to 80°C while stirring Sulfur (9.940 g; 0.3101 mol, 0.9859 eq ) was added and the mixture was stirred for 45 min. Tetrabutylphosphonium bromide (50% in water; 2 560 g; 3.774 mmol; 0.012 eq ) and the 1-chloro- 6-thiopropyltriethoxysilylhexane intermediate from Example 4 (224.6 g; 0.6290 mol; 2,000 eq ) was added over the course of 30 min and then stirred at 75-80°C for 5 h. The organic phase was removed and freed of volatile constituents under reduced pressure, 6- Bis(thiopropyltriethoxysilylhexyl) disulfide (yield: 97%, molar ratio; silane of the formula I: 64% (EtO)jSi(CH2)3S(CH2)eS2(CH2)6S(CH2bSi(OEt)3 and silane of the formula II: 36% (EtO)3Si(CH2)3S(CH2)6S(CH2)3Si(OEt)3, % by weight: silane of the formula I: 69% by weight of (EtO)3Si(CH2}3S(CH2)6Sz(CH2)8S(CH2)3Si(OEt)3 and silane of the formula II: 31% by weight of (EtO)3Si(CHz)3S(CHz)8S(CHi)3Si(OEt)3) was obtained as a clear liquid. Example 6: H2S (27.179 g: 0.798 mol; 1 40 eq) was metered at 60°C into NaOEt (about 21% in EtOH; prepared from sodium (27 50 g; 1 196 mol; 2,10 eq) and EtOH (425 g) over the course of 20 min. After the addition and reaction time of 30 minutes, sulfur (20.07 g; 0 627 mol; 1 10 eq) was added After 20 min, 1-chloro-6-thiopropyltriethoxysilylhexane from Example 4 (61% purity; 600 g, 1 139 mol, 2.00 eq). Subsequently, the reaction temperature was adjusted to 80°C and the mixture was stirred until conversion was complete. On completion of reaction, solids formed were removed by filtration and the product was freed of the solvent under reduced pressure. Bis(thiopropyltriethoxysilylhexyl) disulfide (yield: 98%, molar ratio: silane of the formula I: 64% (EtO)3Si(CHz)3S(CH2)BS2(CH2)aS(CH2)3Si(OEt)3 and silane of the formula II: 36% (EtO)3Si(CH2)3S(CH2)eS(CH2)3Si(OEt)3, % by weight: silane of the formula I: 69% by weight of (EtO)3Si(CHz)3S(CH2)6S2(CH2)8S(CH2)3Si(OEt)3 and silane of the formula II: 31% by weight of (EtO)3Si(CH2)3S(CH2)BS(CHjhSi(OEt)3) was obtained as a clear liquid Example 7: 1-Chloro-6-thiopropyltriethoxysilylhexane from Example 4 (61% purity; 600 0 g; 1 139 mol; 2.00 eq) was dissolved in EtOH (600 g). Thereafter, sodium polysulfide (Na2S379l 20 02 g, 0.120 mol; 0.21 eq) was added in solid form, and the reaction mixture was heated to 60°C and kept at that temperature for 30-60 minutes. Then, at 60"C, the first of a total of eight metered additions of Na2S was effected (totalling 13,33 g; 0.171 mol; 0,3 eq). Thereafter, the mixture was heated at reflux for 1 h. The remaining seven metered additions of Na2S were effected under reflux and each at an interval of 10 minutes. After the last metered addition of NajS, the mixture was heated at reflux for another two hours and then left to cool to room temperature. The reaction mixture was filtered The filtrate was freed of volatile constituents under reduced pressure and filtered again The product (95%, molar ratio: silane of the formula I: 64% (EtO)3Si(CH2)3S(CH2)sS2(CH2}eS(CH2)3Si(OEt)3 and silane of the formula II: 36% (EtO)3Si(CH2)3S(CH2)6S(CH2)3Si(OEt)3. % by weight: silane of the formula I: 69% by weight of (EtO)3Si(CH2)3S(CH2)6S2(CH2)6S(CH2)3Si(OEt)3 and silane of the formula II: 31% by weight of (EtO)3Si(CH2)3S(CHa)6S(CH2)3Si(OEtb) was obtained as a clear liquid, Example 8: 7.2 parts by weight of Comparative Example 1 together with 3.4 parts by weight of Comparative Example 2 were weighed into a flat PE bag from Kaiser und Kraft (film thickness: 50 um) and mixed. This mixture corresponds to a molar ratio: silane of the formula I: 59% (EtO)3Si(CH2)3S(CH2)6S2(CH2)8S(CH2)3Si(OEt)3 and silane of the formula II. 41% (ElO)3Si(CH2)jS(CH2)6Sdimethylbutyl)-rV,-pheny1-p-phenylenediamine {6PPD) from Rhein Chemie Rheinau GmbH. g) TMQ Vulkanox HS/LG: polymeric 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) from Rhein Chemie Rheinau GmbH, h) Antiozonant wax: Protektor G3108 composed of refined hydrocarbons (freezing point ■ 57°C) from Paramelt B V. i) ZnO- RS RAL B44 C ZnO zinc oxide from Arnsperger Chemikalien GmbH. j) Fatty acid: fatty acid mixture (Cie / Cia), EDENOR ST1, from Caldic Deutschland Chemie B.V, k) DPG-80: Rhenogran DPG-80: 80% W,W'-diphenylguanidine (DPG) on 20% elastomeric carrier and dispersant from Rhein Chemie Rheinau GmbH. I) CBS: VulkacitCZ/EG-C: W-cyclohexyl-2-benzothiazolesulfenamide from Rhein Chemie Rheinau GmbH. m) Sulfur: 80/90° ground sulfur from Solvay & CPC Barium Strontium GmbH & Co KG The mixtures were prepared in three stages in a 1.5 I internal mixer (E-type) at a batch temperature of 150°C in accordance with the mixing instructions described in Table 2. The general process for preparing rubber mixtures and vulcanizates thereof is described in the book: "Rubber Technology Handbook", W Hofmann, Hanser Verlag 1994, Vulcanization was effected at a temperature of 160°C in a typical vulcanizing press with a holding pressure of 120 bar after tt»s% The t95% lime was determined by means of a moving die rheometer (rotorless vulcameter) as per ISO 6502 {section 3.2 "rotorless curemeter") at 160X Rubber testing was effected in accordance with the test methods specified in Table 3, Compared to the comparative mixtures, the inventive mixtures feature improved processing (Mooney viscosity) in all three mixing stages This is confirmed by lower Mmin values. In the inventive mixtures, higher crosslinking yields (A torque (Mmm-Mmm)) are obtained. Moreover, the silane mixtures according to the invention lead to advantages in strengthening (300% modulus), in abrasion resistance, in rolling resistance (resilience, tan 5) and in dynamic stiffness (E* at 0°C and eo'C), Example 16: Rubber tests The formulation used for the rubber mixtures is specified in Tabte 5 below. The unit phr means parts by weight based on 100 parts of the raw rubber used Mixtures 6-8 all contain the same phr amount of silane of the formula I (EtO)3Si(CH2)3S(CHj)eSi(CH2)BS(CH2)3Si(OEt):> and an increasing amount of silane of the formula II (EtO)jSI(CH!)3S(CHi>aS