The present invention relates to oligomeric organosilanes, to a process for preparation thereof and to the use thereof in rubber mixtures.

It is known that sulfur-containing organosilicon compounds such as 3- mercaptopropyltrimethoxysilane or bis(3-[triethoxysilyl]propyl)tetrasulfane can be used as a silane adhesion promoter or reinforcing additive in rubber mixtures with oxidic fillers, including for tyre treads and other parts of automobile tyres (DE 2 141 159, DE 2 212239, US 3 978 103, US 4 048 206).

EP 0784072 A1 discloses rubber mixtures based on at least one elastomer with silica as a filler and a reinforcing additive which is prepared by blending or as an in situ reaction product from at least one functional polyorganosiloxane compound, and which contain a functional organosilane as a further constituent. Monomeric units used are especially 3-mercaptopropyltrialkoxysilanes or bis(trialkoxysilylpropyl)tetrasulfanes, which bear 3 and 6 alkoxy substituents respectively.

In addition, EP 0964021 discloses oligomeric organosilane polysulfanes which are not polycondensed to give a solid, and which contain the structural units A and/or B and/or C in any linear, branched or cyclic arrangement.

WO 2006/037380, EP 0997489 and EP 1273613 likewise disclose oligomeric organosilanes.

In addition, US 7368584 discloses mercapto-functional silane compositions comprising at least one mercapto-functional silane having the chemical structure [G ¹ -/SiX ^a _u Z ^p _v Z ^e w)s]m[(HS)r-G ² - (SiX ^a uZP _v Z ⁶ w)s]n.

EP 3094686 discloses oligomeric organosilanes containing at least two different structural units within a molecule, selected from the structural units A, B, C and D joined in any desired linear, branched or cyclic arrangement

C D

Disadvantages of the known oligomeric organosilanes are poor tear resistance and/or poor storage stability.

It is an object of the present invention to provide oligomeric organosilanes having improved tear resistance and/or improved storage stability.

The invention provides oligomeric organosilanes containing at least structural units A, B and C in any linear, branched or cyclic arrangement

A B C where n = 1-10, preferably 1-4, more preferably 3,

R ¹ and R ³ are the same or different and are independently -OH, (C1-C4)alkoxy, preferably ethoxy, OSiR ² R ³ 2, OSi((CH2)nSH)R ³ 2, structural unit C which is attached via the oxygen atom to the silicon atom of structural unit A or B and is terminated by an -OH group or is attached cyclically to the oxygen of the Si-O group of the same structural unit, or an alkyl polyether group -O-(R ⁵ -O) _m -R ⁶ where R ⁵ is the same or different and is a branched or unbranched, saturated or unsaturated, aliphatic divalent C1-C30 hydrocarbon group, preferably CH2CH2, m has an average value of 1 to 30, preferably 5, and R ⁶ is an unsubstituted or substituted, branched or unbranched C1-C30-alkyl, preferably C13H17, C2-C30-alkenyl, a C6-C14-aryl group, or a C7-C40-aralkyl group, R ² is a branched or unbranched, saturated or unsaturated, aliphatic monovalent C1-C30, preferably C1-C8, more preferably C8, hydrocarbon group,

R ⁴ is identical or different branched or unbranched, saturated or unsaturated C1-C10-alkyl, C1- C10-alkyl-OH, C1-C10-alkyl-NH2 or H, and p = 1-10, which are characterized in that the molar ratio of the alkyl polyether group -O-(R ⁵ -O) _m -R ⁶ to silicon is greater than 0.

The molar ratio of the alkyl polyether group -O-(R ⁵ -O) _m -R ⁶ to silicon may be between 0 and 0.30, preferably between 0 and 0.10, more preferably from 0.01 to 0.09, most preferably from 0.01 to 0.08. The molar ratio of structural unit C to silicon may be between 0 and 1 .7, preferably between 0.1 and 1 .5. Structural unit C may also be present in R ¹ and/or R ³ and may be terminated by an OH group or be cyclically attached to the oxygen atom of the Si-O group of the same structural unit. The molar ratio of structural units A and B in the oligomeric organosilanes according to the invention may be 10:1 to 1 :10, preferably 3:1 to 1 :3, more preferably 2:1 to 1 :2.

The alkyl polyether group may preferably be -O-(CH2CH2-O) _m -R ⁶ , more preferably -O-(CH2CH2- O) ₅ -R ⁶ , most preferably -O-(CH2CH2-O)S-CI ₃ H27.

In the oligomeric organosilane according to the invention, it may preferably be the case that R ¹ = OC2H5 or -O-(R ⁵ -O) _m -R ⁶ , R ² = (CH ₂ )7CH ₃ , R ³ = OC2H5 or -O-(R ⁵ -O) _m -R ⁶ , R ⁴ = H or CH ₃ , R ⁵ = CH2CH2, R ⁶ = CI ₃ H ₂ 7, n = 3, m = 5, p = 3.

Structural unit A may be, for example,

[-O-(HO-CH2-CH ₂ -O)Si(-(CH ₂ ) ₃ -SH)-],

[-O-((EtO) ₂ Si((CH ₂ ) ₃ -SH)-O-)Si(-(CH ₂ ) ₃ -SH)-],

[-O-((Ci ₃ H ₂ 7-(OCH ₂ CH2)5-O)(EtO)Si(-(CH2) ₃ -SH)-O-)Si((CH2) ₃ -SH)-],

[-O-((HO-CH2-CH(CH ₃ )-CH ₂ -O)(EtO)Si(-(CH2) ₃ -SH)-O-)Si((CH ₂ ) ₃ -SH)-], [-O-((EtO) ₂ Si((CH ₂ )7-CH ₃ )-O-)Si(-(CH ₂ ) ₃ -SH)-],

[-O-((Ci ₃ H ₂ 7-(OCH ₂ CH2)5-O)(EtO)Si(-(CH2)7-CH ₃ )-O-)Si((CH2) ₃ -SH)-] or [-O-((HO-CH2-CH(CH ₃ )-CH ₂ -O)(EtO)Si(-(CH2)7-CH ₃ )-O-)Si((CH ₂ ) ₃ -SH)-].

Structural unit B may be, for example,

[-O-(MeO)Si(-(CH ₂ )7-CH ₃ )-],

[-O-(EtO)Si(-(CH ₂ ) ₂ -CH ₃ )-],

[-O-(EtO)Si(-(CH ₂ ) ₃ -CH ₃ )-],

[-O-(EtO)Si(-(CH ₂ )4-CH ₃ )-],

[-O-(EtO)Si(-(CH ₂ ) ₅ -CH ₃ )-],

[-O-(EtO)Si(-(CH ₂ ) ₆ -CH ₃ )-],

In the oligomeric organosilane according to the invention, structural unit C may more preferably be [-O-CH ₂ -CH(CH) ₃ -CH ₂ -] or [-O-CH ₂ -CH ₂ -].

The oligomeric organosilane according to the invention may most preferably contain the structural units and

C = [-O-CH ₂ -CH(CH) ₃ -CH ₂ -].

The present invention further provides a process for preparing the oligomeric organosilanes according to the invention, which is characterized in that a mercaptosilane D, an alkylsilane E, a polyol F, -R ⁷ HO- (C(R ⁴ ) ₂ ) _p -OH

D E F an alkyl polyether alcohol of the formula HO-(R ⁵ -O) _m -R ⁶ where R ² , R ⁴ , R ⁵ , R ⁶ n, m, p have the same definition as defined above,

R ⁷ is the same or different and is -OH, (C1-C4)-alkoxy, preferably ethoxy, or an alkyl polyether group -O-(R ⁵ -O) _m -R ⁶ where R ⁵ is the same or different and is a branched or unbranched, saturated or unsaturated, aliphatic divalent C1-C30 hydrocarbon group, preferably CH2CH2, m has an average value of 1 to 30, preferably 5, and R ⁶ is an unsubstituted or substituted, branched or unbranched C1-C30-alkyl, preferably C13H17, C2-C30-alkenyl, a C6-C14-aryl group, or a C7-C40- aralkyl group, and a catalyst are mixed and reacted at a temperature of 20-180°C, preferably 90°C-150°C.

The reaction can be effected within 30 min - 10 h, preferably within 30 min - 3 h.

The reaction can be effected with stirring.

The secondary components can be separated off by distillation.

The secondary components can be separated off by distillation during the reaction or thereafter. The secondary components can preferably be separated off during the reaction.

The secondary components can be separated off by distillation at atmospheric pressure or reduced pressure. The secondary components can preferably be separated off by distillation under reduced pressure. More preferably, they can be separated off by distillation at a pressure of 20-200 mbara.

Components D and E may be used in a molar ratio of 1 :10 to 10:1 , preferably of 1 :3 to 3:1 , more preferably of 1 :2 to 2:1 .

Components D and F may be used in a molar ratio of 1 :1 to 1 :10. Preferably, components D and F may be used in a molar ratio of 1 :2 to 1 :10. More preferably, components D and F may be used in a molar ratio of 1 :2 to 1 :4. Most preferably, components D and F may be used in a molar ratio of 1 :2 to 1 :3.

Component D and the alkyl polyether alcohol of the formula HO-(R ⁵ -O) _m -R ⁶ may be used in a molar ratio of 1 :0.01 to 1 :2. Preferably, component D and the polyether alcohol of the formula HO-(R ⁵ - O) _m -R ⁶ may be used in a molar ratio of 1 :0.1 to 1 :1 .

The catalyst may be added in catalytic or stoichiometric amounts. In this context, all kinds of acidic, basic or nucleophilic catalysts which are known to those skilled in the art from the SOLGEL chemistry of alkoxysilanes (see, for example, R. Corriu, D. Leclercq, Angew. Chem. 1996, 108, 1524-1540) are also suitable for the oligomerization in the context of the invention. It is unimportant here whether the catalysts are in the same phase as the reaction solution (homogeneous catalysis) or are in the form of solids (heterogeneous catalysis) and are removed after the reaction has ended.

Preferably, the homogeneous catalysis can be conducted with a transition metal complex, for example tetrabutyl orthotitanate, or a transition metal salt. Basic catalysis can be effected, for example, with an organic base such as triethylamine, tetramethylpiperidine, tributylamine or pyridine, or with an inorganic base such as NaOH, KOH, Ca(OH)2, Na2CO3, K2CO3, CaCOs, CaO, NaHCOs, KHCO3 or alkoxides such as NaOCHs or NaOC2Hs. Acidic catalysis can be effected with dilute aqueous mineral acids, such as H2SO4 or HCI, or solutions of Lewis acid in water.

Preferably, the catalyst used may be a transition metal complex, KOH, NaOH, ammonium fluoride, H2SO4 or HCI.

More preferably, the catalyst used may be a transition metal complex. Most preferably, the catalyst used may be tetrabutyl orthotitanate.

The process according to the invention can be performed in solvent-free form or in the presence of a solvent, preferably in solvent-free form.

Solvents may be an inert organic solvent or mixture thereof, for example an aromatic solvent such as chlorobenzene, a halogenated hydrocarbon, for example chloroform, methylene chloride, an ether, for example diisopropyl ether, tert-butyl methyl ether, tetrahydrofuran or diethyl ether, acetonitrile, a carboxylic ester, for example ethyl acetate, methyl acetate, isopropyl acetate, or an alcohol, for example methanol, ethanol, n-propanol, i-propanol, n-butanol, sec-butanol or tertbutanol.

The mercaptosilane of the formula D may, for example, be

3-mercaptopropyltrimethoxysilane,

3-mercaptopropyltriethoxysilane,

4-mercaptobutyltriethoxysilane,

5-mercaptopentyltriethoxysilane or

6-mercaptohexyltriethoxysilane.

The alkylsilane of the formula E may, for example, be methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, isobutyltri methoxysilane, isobutyltriethoxysilane, pentyltri methoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane, hexylltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, hexadecyltrimethoxysilane or hexadecyltriethoxysilane.

The polyol of the formula F may, for example, be propane-1 ,3-diol, propane-1 ,2,3-triol, 2-methylpropane-1 ,3-diol or ethane-1 ,2-diol.

The alkyl polyether alcohol may, for example, be

Ci3H ₂ 7-(OCH ₂ CH ₂ )5-OH.

The catalyst can remain in the product after the reaction, be deactivated, preferably by neutralization, or be removed, preferably by filtration. More preferably, the catalyst may not be deactivated after the reaction and remain in the product.

The invention further provides for the use of the oligomeric organosilanes according to the invention in rubber mixtures.

The invention further provides rubber mixtures comprising the oligomeric organosilanes according to the invention.

The rubber mixtures according to the invention can be used for production of shaped bodies, especially pneumatic tyres or tyre treads.

The rubber mixtures according to the invention may comprise rubber, filler, preferably precipitated silica, optionally further rubber auxiliaries, and at least one oligomeric organosilane according to the invention.

The use of the oligomeric organosilanes according to the invention in rubber blending processes distinctly reduces the unpleasant release of alcohol because of the precondensation that has already taken place. Compared to the usual mode of operation, for example by simple use of bis(3- [triethoxysilyl]propyl)tetrasulfane (TESPT) as adhesion promoter, evolution of alcohol is reduced during the blending operation.

Rubber used may be natural rubber and/or synthetic rubbers. Preferred synthetic rubbers are described, for example, in W. Hofmann, H. Gupta, "Handbuch der Kautschuktechnologie" [Handbook of Rubber Technology], Dr. Gupta Verlag, Ratingen 2001 , chapter 3, p. 2-4. They may include: polybutadiene (BR), polyisoprene (IR), styrene/butadiene copolymers, for example emulsion SBR (E-SBR) or solution SBR (S- SBR), preferably having styrene contents of 1% to 60% by weight, more preferably 5% to 50% by weight (SBR), chloroprene (CR), isobutylene/isoprene copolymers (HR), butadiene/acrylonitrile copolymers having acrylonitrile contents of 5% to 60%, preferably 10% to 50%, by weight of (NBR), partly hydrogenated or fully hydrogenated NBR rubber (HNBR), ethylene/propylene/diene copolymers (EPDM), abovementioned rubbers which also have functional groups, e.g. carboxy, silanol or epoxy groups, for example epoxidized NR, carboxy-functionalized NBR or amine(NR2), silanol(- SiOH)-, epoxy-, mercapto-, hydroxy-, or siloxy(-Si-OR)-functionalized SBR, and mixtures of these rubbers. The rubbers mentioned may additionally be silicon- or tin-coupled. In a preferred embodiment, the rubbers may be sulfur-vulcanizable. For the production of car tyre treads, it is possible in particular to use anionically polymerized S-SBR rubbers (solution SBR) with a glass transition temperature above -50°C, and also mixtures of these with diene rubbers. It is possible with particular preference to use S-SBR rubbers having a butadiene content with a vinyl fraction of more than 20% by weight. It is possible with very particular preference to use S-SBR rubbers having a butadiene content with a vinyl fraction of more than 50% by weight.

It is preferably possible to use mixtures of the abovementioned rubbers which have an S-SBR content of more than 50% by weight, preferably more than 60% by weight.

The rubber may be a functionalized rubber, where the functional groups may be amine and/or amide and/or urethane and/or urea and/or aminosiloxane and/or siloxane and/or silyl and/or alkylsilyl, for example N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane or methyltriphenoxysilane, and/or halogenated silyl and/or silane sulfide and/or thiol and/or hydroxyl and/or ethoxy and/or epoxy and/or carboxyl and/or tin, for example tin tetrachloride or dibutyldichlorotin, and/or silanol and/or hexachlorodisiloxane and/or thiocarboxy and/or nitrile and/or nitroxide and/or amido and/or imino and/or urethane and/or urea and/or dimethylimidazolidinone and/or 2-methyl-2-thiazoline and/or 2-benzothiazoleacetonitrile and/or 2- thiophenecarbonitrile and/or 2-(N-methyl-N-3-trimethoxysilylpropyl)thiazoline and/or carbodiimide and/or N-substituted aminoaldehyde and/or N-substituted aminoketone and/or N-substituted aminothioaldehyde and/or N-substituted aminothioketone and/or benzophenone and/or thiobenzophenone with amino group and/or isocyanate and/or isothiocyanate and/or hydrazine and/or sulfonyl and/or sulfinyl and/or oxazoline and/or ester groups.

The rubber mixture according to the invention may contain at least one filler.

Fillers usable for the rubber mixtures according to the invention include the following fillers: Carbon blacks: The carbon blacks may be produced by the lamp-black process, furnaceblack process, gas-black process or thermal process and have BET surface areas of from 20 to 200 m ² /g. The carbon blacks may optionally also contain heteroatoms, such as Si for example.

Amorphous silicas produced for example by precipitation from solutions of silicates or flamehydrolysis of silicon halides with specific surface areas of from 5 to 1000 m ² /g, preferably from 20 to 400 m ² /g (BET surface area) and with primary particle sizes of from 10 to 400 nm. The silicas may optionally also be in the form of mixed oxides with other metal oxides, such as oxides of Al, Mg, Ca, Ba, Zn and titanium.

Synthetic silicates, such as aluminium silicate, alkaline earth metal silicates such as magnesium silicate or calcium silicate, having BET surface areas of 20 to 400 m ² /g and primary particle diameters of 10 to 400 nm.

Synthetic or natural aluminium oxides and synthetic or natural aluminium hydroxides. Natural silicates, such as kaolin and other naturally occurring silicas.

Glass fibres and glass-fibre products (mats, strands) or glass microbeads.

It is possible with preference to use amorphous silicas prepared by precipitation from solutions of silicates, with BET surface areas of 20 to 400 m ² /g, more preferably 100 m ² /g to 250 m ² /g, in amounts of 5 to 150 parts by weight, based in each case on 100 parts of rubber.

With very particular preference, it is possible to use precipitated silicas as filler.

The fillers mentioned may be used alone or in a mixture.

The rubber mixtures according to the invention may contain 5 to 150 parts by weight of filler and 0.1 to 30 parts by weight, preferably 1 to 25 parts by weight, more preferably 2 to 20 parts by weight, of the oligomeric organosilanes according to the invention, wherein the parts by weight are based on 100 parts by weight of rubber.

The oligomeric organosilanes according to the invention may be used as adhesion promoter between inorganic materials, for example glass beads, glass flakes, glass surfaces, glass fibres, or oxidic fillers, preferably silicas such as precipitated silicas and fumed silicas, and organic polymers, for example thermosets, thermoplastics or elastomers, or as crosslinking agents and surface modifiers for oxidic surfaces.

The oligomeric organosilanes according to the invention may be used as coupling reagents in filled rubber mixtures, examples being tyre treads, industrial rubber articles or footwear soles.

The rubber mixtures according to the invention may comprise further rubber auxiliaries, such as reaction accelerators, ageing stabilizers, heat stabilizers, light stabilizers, antiozonants, processing aids, plasticizers, resins, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic acids, retarders, metal oxides, and activators such as diphenylguanidine, triethanolamine, polyethylene glycol, alkoxy-terminated polyethylene glycol alkyl-O-(CH2-CH2-O) _y i-H with y ¹ = 2-25, preferably y ¹ = 2-15, more preferably y ¹ = 3-10, most preferably y ¹ = 3-6, or hexanetriol, that are familiar to the rubber industry. The rubber auxiliaries may be used in familiar amounts determined by factors including the end use. Customary amounts may, for example, be amounts of 0.1% to 50% by weight based on rubber. Crosslinkers used may be peroxides, sulfur or sulfur donor substances. The rubber mixtures according to the invention may further comprise vulcanization accelerators. Examples of suitable vulcanization accelerators may be mercaptobenzothiazoles, sulfenamides, thiurams, dithiocarbamates, thioureas and thiocarbonates. The vulcanization accelerators and sulfur may be used in amounts of 0.1 % to 10% by weight, preferably 0.1% to 5% by weight, based on 100 parts by weight of rubber.

The rubber mixtures according to the invention can be vulcanized at temperatures of 100°C to 200°C, preferably 120°C to 180°C, optionally at a pressure of 10 to 200 bar. The blending of the rubbers with the filler, any rubber auxiliaries and the oligomeric organosilanes according to the invention can be conducted in known mixing units, such as rollers, internal mixers and mixing extruders.

The rubber mixtures according to the invention can be used for production of moulded articles, for example for the production of tyres, especially pneumatic tyres or tyre treads, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, footwear soles, sealing rings and damping elements.

The oligomeric organosilanes according to the invention and the fillers are preferably added at mass temperatures of 100 to 200°C, but can also be added at a later stage at lower temperatures (40 to 100°C), for example together with further rubber auxiliaries.

The oligomeric organosilanes can be added to the blending operation either in pure form or else applied to an inert organic or inorganic carrier. Preferred carrier materials are silicas, natural or synthetic silicate, aluminium oxide or carbon blacks.

The oligomeric organosilanes according to the invention are obtainable by the process according to the invention.

The oligomeric organosilanes according to the invention have improved storage stability and/or, in rubber mixtures, the advantage of improved tear resistance.

GC analysis:

Determination of free ethanol/OCTEO/MPTES/2-methylpropan-2-ol

The volatile components are determined by gas chromatography by the internal standard method. For this purpose, calibration of the individual components is conducted with an internal standard such as n-nonane, n-decade or n-dodecane in an appropriate solvent. The gas chromatograph used is an HP 6850 or HP7820 with a TCD detector. The separating column used is an HP5 column having the following properties: length: 30 m; internal diameter: 0.53 mm with a film thickness of 2.65 mm. Alternatively, an HP1 column having the following properties is used: length: 30 m; internal diameter: 0.53 mm with a film thickness of 1 .50 mm. The temperature is 250°C, the detector temperature 280°C. The temperature program of the column oven is: 50°C - 5 min - 15°C/min - 275°C - 15 min. The carrier gas used is helium with a flow rate of ~ 4 ml/min and a split ratio of 1 :50 to 1 :100. The amount of sample injected is 0.4 ml.

This method is employed analogously for the determination of other alcohols, for example methanol.

Calculation of the content of the sample:

Ci = concentration of the components i to be determined fi = calibration factor of component i Ast = peak area of the internal standard

Ai = peak area of the component i to be determined mst = weight of the internal standard mp = weight of the sample

Gas chromatography determination of the ethanol after hydrolysis:

The determination of the ethanol after hydrolysis can be effected by the hydrolysis of the silane by means of sulfuric acid (20 w%). Subsequently, water and sodium hydroxide (20 w%) are added. The resultant mixture is subjected to steam distillation with a suitable apparatus. The distillate is collected in a corresponding standard flask, 2-butanol is added as internal standard, and the mixture is made up to the mark with distilled water.

The gas chromatograph used is a capillary gas chromatograph with FID and evaluation software, for example HP7820 with OpenLab. The separating column has the following properties: length: 30 m; internal diameter: 0.32 mm; film thickness 1 .00 mm; stationary phase: Stabiwax (#10654- 6850). The injector temperature is 250°C, the detector temperature 280°C. The column oven: 90°C - 10 min - 25°C/min - 240°C - 0 min. The carrier gas used is helium with a flow rate of ~ 2 ml/min and a split ratio of ~ 1 :50. The combustion gas used is a hydrogen/synthetic air mixture. The amount of sample injected is 1 .0 ml.

This method is analogously applicable to the determination of other hydrolysable alkoxy groups, for example methoxy groups.

Calculation of the content of the sample:

Ci = concentration of the components i to be determined fi = calibration factor of component i Ast = peak area of the internal standard

Ai = peak area of the component i to be determined mst = weight of the internal standard mp = weight of the sample NMR analysis: In addition, the trialkoxysilane content, and also M, D and T structures, can be determined using ²⁹ Si NMR spectrometry, which is likewise well known to the person skilled in the art. The solvent used is deuterated chloroform with tetramethylsilane as internal standard.

²⁹ Si NMR (79.5 MHz): 40-46 ppm (trialkoxysilane); 50-54 ppm (M structures); 57-61 ppm (D structures); 61-65 ppm (T structures).

A B C

The molar proportion of silicon-containing groups (structural units A, B) and of structural unit C, and of the attached alkyl polyether group (R ¹ , R ³ = -O-(R ⁵ -O) _m -R ⁶ ), can be determined by using ¹³ C NMR spectroscopy, which is likewise well known to the person skilled in the art. The solvent used is deuterated chloroform with tetramethylsilane as internal standard and chromium acetylacetonate. Structural unit C may also be present in R ¹ and/or R ³ and may be terminated by an OH group or be cyclically attached to the oxygen atom of the Si-O group of the same structural unit.

The oligomeric silanes were characterized by spectroscopic determination of the following ratios via integration of the corresponding ¹³ C NMR signals:

Molar ratio of structural unit C to silicon:

[A + B] / [C]

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B] = polyether alcohol I Si

Molar ratio of structural units A and B:

Examples

Octyltriethoxysilane (OCTEO) and VP Si 263® (MPTES, 3-mercaptopropyltriethoxysilane) are silanes from Evonik Operations GmbH.

Marlosol is a polyether alcohol of the formula HO-(R ⁵ -O) _m -R ⁶ with R ⁵ = CH2CH2, R ⁶ = C13H27 and m = 5 from Sasol.

Comparative Example 1 , corresponding to Example 3 from US7369584 (MPTES:OCTEO:2-MPD = 1 :2.33:10) An initial charge of 3-mercaptopropyltriethoxysilane (MPTES) (1.00 eq; 0.34 mol; 81.00 g) together with octyltriethoxysilane (OCTEO) (2.33 eq; 0.79 mol; 219.00 g) in a round-bottom flask is mixed. Concentrated sulfuric acid (0.010 eq; 3.60 mmol; 0.30 g) is added to the mixture. Subsequently, a vacuum of 67 mbar is applied and the mixture is heated to 50°C. As soon as 50°C has been attained, 2-methylpropane-1 ,3-diol (2-MPD) (10 eq; 3.395 mol; 306.00 g) is metered in within 30 min. The ethanol formed is removed by distillation. On completion of metered addition, the mixture is stirred for a further 4.5 h. As soon as the product has cooled down to room temperature, sodium ethoxide (w = 21 %; 0.012 eq; 4.30 mmol; 1 .45 g) is added to neutralize the sulfuric acid.

Analysis:

- GC: free ethanol: 3.6% ethanol after hydrolysis: 4.3%

MPTES (1.1 %), OCTEO (< 0.1 %), 2-methylpropane-1 ,3-diol (38%)

¹³ C NMR (100 MHz):_6 (ppm) 27.5 (m, Si-(CH ₂ ) ₃ -SH), 29.2 (m, Si-(CH ₂ ) ₇ -CH ₃ ), 64.0 - 65.8 (m, -(O- CH ₂ ) ₂ CH(CH ₃ )), 70.1-70.8 (m, -O-CH ₂ -CH(CH ₃ )-CH ₂ -OH).

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B] = 0.0:1

Molar ratio of structural unit C to silicon:

[C] / [A + B] = 1 .75

Molar ratio of structural units A and B:

[A] / [B] = 0.4:1

²⁹ Si NMR: trialkoxysilanes: 94 mol%; M structures: 6 mol%

²⁹ Si NMR after 4 months: trialkoxysilanes: 88 mol%; M structures: 12 mol% Comparative Example 2, corresponding to example 1 from EP 3094686 (MPTES:OCTEO:Marlosol = 1 :0.5:0.5) - 0.8 eq H ₂ O

An initial charge of 3-mercaptopropyltriethoxysilane (1.00 eq; 1.75 mol; 417.00 g) together with octyltriethoxysilane (0.50 eq; 0.880 mol; 242.00 g) is heated to 85°C. A mixture of H ₂ O (0.8 eq;

2.11 mol; 38.00 g) and concentrated hydrochloric acid (w = 37%; 0.005 eq; 8.00 mmol; 0.30 g) in ethanol (4.50 eq; 7.88 mol; 363.00 g) is slowly added dropwise, and the reaction mixture is stirred for a further 8.5 h. The solvent and the alcohol of hydrolysis are removed under reduced pressure. To the oligomer thus obtained are added Marlosol (0.50 eq; 0.880 mol; 368.00 g) and tetra-n-butyl titanate (0.0008 eq; 1.469 mmol; 0.50 g). The mixture is heated to 140°C and the temperature is maintained for 1 h. The ethanol formed is removed by distillation under reduced pressure.

Analysis:

- GC: free ethanol: 0.7% ethanol after hydrolysis: 3.7% MPTES (0.3%), OCTEO (0.1 %)

¹³ C NMR (100 MHz):_6 (ppm) = 27.5 (m, Si-(CH ₂ ) ₃ -SH), 29.2 (m, Si-(CH ₂ ) ₇ -CH ₃ ), 61.2 (HO-(CH ₂ - CH ₂ -O) ₅ -CI ₃ H ₂₇ ), 61 .5 (Si-O-(CH ₂ -CH ₂ -O) ₅ -Ci ₃ H ₂₇ ).

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B] = 0.5:1

Molar ratio of structural units A and B:

[A] / [B] = 1.8:1

²⁹ Si NMR: trialkoxysilanes: 0 mol%; M structures: 48 mol%; D structures: 38 mol%; T structures: 14 mol%

²⁹ Si NMR after 4 months: trialkoxysilanes: 0 mol%; M structures: 62 mol%; D structures: 35 mol%; T structures: 3 mol%

Example 1 (MPTES:OCTEO:2-MPD:Marlosol = 1 :2.33:10:1)

An initial charge of 3-mercaptopropyltriethoxysilane (1.00 eq; 0.344 mol; 81.00 g), octyltriethoxysilane (2.33 eq; 0.794 mol; 219.00 g) and Marlosol (1.00 eq; 1.132 mol; 476.12 g) together with tetra-n-butyl titanate (0.0026 eq; 0.88 mmol; 0.30 g) is heated to 130°C. The ethanol formed is removed by distillation. As soon as the mixture has reached 130°C, a vacuum of 200 mbar is applied, which is maintained for 30 minutes. Next, the pressure is reduced to 100 mbar for 30 minutes. The reaction mixture is cooled down to room temperature and 2-methylpropane- 1 ,3-diol (10.0 eq; 3.395 mol; 306.00 g) and tetra-n-butyl titanate (0.0026 eq; 0.88 mmol; 0.30 g) are added, and the mixture is heated again to 130°C. The ethanol formed is removed by distillation. As soon as the mixture has reached 130°C, a vacuum of 200 mbar is applied, which is maintained for 30 minutes, then the pressure is reduced to 20 mbar within 30 minutes. The vacuum of 20 mbar is maintained for 1 h and the mixture is cooled back down to room temperature. Analysis:

- GC: free ethanol: 0.1 % ethanol after hydrolysis: 0.2%

MPTES (< 0.1 %), OCTEO (< 0.1 %), 2-methylpropane-1 ,3-diol (22%)

¹³ C NMR (100 MHz):_6 (ppm) = 27.5 (m, Si-(CH ₂ ) ₃ -SH), 29.2 (m, Si-(CH ₂ ) ₇ -CH ₃ ), 61.2 (HO-(CH2- CH2-O)5-C13H27), 61.5 (Si-O-(CH2-CH2-O) ₅ -C13H27), 64.0-65.8 (m, -(O-CH ₂ ) ₂ CH(CH ₃ )), 70.1- 70.8 (m, -O-CH ₂ -CH(CH ₃ )-CH ₂ -OH).

Molar ratio of structural unit C to silicon:

[C] / [A + B] = 1.16

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B] = 0.22:1

Molar ratio of structural units A and B:

[A] / [B] = 0.5:1

²⁹ Si NMR: trialkoxysilanes: 100 mol%

²⁹ Si NMR after 4 months: trialkoxysilanes: 83 mol%; M structures: 17 mol%

Example 2 (MPTES:OCTEO:2-MPD:Marlosol = 1 :1 :2.95:0.1)

An initial charge of 3-mercaptopropyltriethoxysilane (1.00 eq; 2.20 mol; 524.57 g), octyltriethoxysilane (1.00 eq; 2.20 mol; 602.20 g), 2-methylpropane-1 ,3-diol (2.95 eq; 6.425 mol; 579.00 g), Marlosol (0.10 eq; 0.216 mol; 90.69 g) and tetra-n-butyl titanate (0.00076 eq; 2.00 mmol; 0.57 g) is heated to 130°C. The temperature is maintained for 1.5 h. The ethanol formed is removed by distillation under reduced pressure (200-20 mbar), then the product obtained is cooled down to room temperature.

Analysis:

- GC: free ethanol: 0.5% ethanol after hydrolysis: 0.5% MPTES (< 0.1 %), OCTEO (1 .1 %), 2-methylpropane-1 ,3-diol (0.6%)

¹³ C NMR (100 MHz):_6 (ppm) = 27.5 (m, Si-(CH ₂ ) ₃ -SH), 29.2 (m, Si-(CH ₂ ) ₇ -CH ₃ ), 61.2 (HO-(CH2- CH2-O) ₅ -C13H27), 61.5 (Si-O-(CH2-CH2-O) ₅ -C13H27), 64.0-65.8 (m, -(O-CH ₂ ) ₂ CH(CH ₃ )), 70.1- 70.8 (m, -O-CH ₂ -CH(CH ₃ )-CH ₂ -OH).

Molar ratio of structural unit C to silicon:

[C] / [A + B] = 1 .40

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B ] = 0.01 :1

Molar ratio of structural units A and B:

[A] / [B] = 1:1

²⁹ Si NMR: trialkoxysilanes: 100 mol%

²⁹ Si NMR after 4 months: trialkoxysilanes: 95 mol%; M structures: 5 mol%

Example 3 (MPTES:OCTEO:2-MPD:Marlosol = 1 :0.5:2:0.5)

An initial charge of 3-mercaptopropyltriethoxysilane (1.00 eq; 1 .75 mol; 417.00 g), octyltriethoxysilane (0.50 eq; 0.88 mol; 242.00 g), 2-methylpropane-1 ,3-diol (2.00 eq; 3.50 mol; 315.42 g), Marlosol (0.50 eq; 0.88 mol; 368.00 g) and tetra-n-butyl titanate (0.00038 eq; 1.67 mmol;

0.57 g) is heated to 130°C. The temperature is maintained for 1 .5 h. The ethanol formed is removed by distillation under reduced pressure (200-20 mbar), then the product obtained is cooled down to room temperature.

Analysis:

GC: free ethanol: 0.4% ethanol after hydrolysis: 0.7%

MPTES (0.1 %), OCTEO (0.4%), 2-methylpropane-1 ,3-diol (1.1 %)

¹³ C NMR (100 MHz):_6 (ppm) = 27.5 (m, Si-(CH ₂ ) ₃ -SH), 29.2 (m, Si-(CH ₂ ) ₇ -CH ₃ ), 61.2 (HO-(CH2- CH2-O) ₅ -C13H27), 61.5 (Si-O-(CH2-CH2-O) ₅ -C13H27), 64.0-65.8 (m, -(O-CH ₂ ) ₂ CH(CH ₃ )), 70.1- 70.8 (m, -O-CH ₂ -CH(CH ₃ )-CH ₂ -OH). Molar ratio of structural unit C to silicon:

[C] / [A + B] = 0.95

Molar ratio of the alkyl polyether group -O-(R ⁵ -O)m-R ⁶ to silicon: [-O-(R ⁵ -O) _m -R ⁶ ] / [A + B ] = 0.09:1

Molar ratio of structural units A and B:

[A] / [B] = 2:1

²⁹ Si NMR: trialkoxysilanes: 100 mol%

²⁹ Si NMR after 4 months: trialkoxysilanes: 96 mol%; M structures: 4 mol%

Example 4

The formulation used for the rubber mixtures is specified in Table 1 below. In this table, the unit phr means parts by weight based on 100 parts of the crude rubber employed. The oligomeric silanes, based on the reference silane according to Comparative Example 1 , were used in an equimolar amount based on the mercapto group, since the mercapto group is the only function that binds to the rubber.

The molar mass of the oligomeric silanes based on the mercapto group can be calculated from the integration of the ¹³ C and ²⁹ Si NMR signals according to the following formula:

M (g/mol) = [M(R ² ) * xi3c(R ² )+ M(-(CH ₂ ) _n -SH)* x c (-(CH ₂ )n-SH)+ M(-O-(C(R ⁴ ) ₂ ) _n -)* Xi3c (-O- (C(R ⁴ ) ₂ ) _n -O)) + M(-O-(R ⁵ -O) _m -R ⁶ ) * Xi3c(-O-(R ⁵ -O) _m -R ^e )+

M(Si) * X29Si(trialkoxysilanes) + (M(SiOos) * X29Si(M structures) + (M(SiO)) * X29Si(D structures) + (M(SiOi s) * X29S;(T structures)] I xi3c(-(CH ₂ ) _n -SH)

Xi3c (x) = molar proportion of component x based on the total amount of silanes from integration of the ¹³ C NMR signals = lnt(x) I (lnt((-(CH ₂ ) _n -SH) + In^R ² ))

X29Si (x)= molar proportion from ²⁹ Si NMR based on the total amount of silanes (trialkoxysilanes, M, D and T structures) from integration of the ²⁹ Si NMR signals = lnt(x) I (Int (trialkoxysilanes) + Int (M structures) + Int (D structures) + Int (T structures))

Table 1

The polymer Buna® VSL 4526-2 is a solution-polymerized SBR copolymer from ARLANXEO Deutschland GmbH, having a styrene content of 26% by weight and a vinyl fraction of 45% by weight. The copolymer contains 37.5% TDAE oil and has a Mooney viscosity (ML 1 +4/100°C) of 50.

The polymer Buna® CB 24 is a cis-1 ,4-polybutadiene (neodymium type) from ARLANXEO Deutschland GmbH, having a cis-1 ,4 content of at least 96% and a Mooney viscosity of 44. ULTRASIL® 7000 GR is a readily dispersible silica from Evonik Industries AG and has a CTAB surface area of 160 m ² /g. N330 is carbon black from Orion Engineered Carbons GmbH, TDAE oil used is Vivatec 500 from Hansen & Rosenthal GmbH & Co. KG, Vulkanox® 4020 is 6PPD from LANXESS Distribution GmbH, Vulkanox® HS/LG is TMQ from Lanxess and Protektor™ G3108 is an antiozonant wax from Paramelt B.V., WeiBsiegel Spezial zinc oxide is ZnO from Grillo Zinkoxid GmbH, Palmera B1804 is palmitic/stearic acid from Caldic Deutschland GmbH & Co. KG. Vulkacit® CZ is CBS from LANXESS Distribution GmbH. Uhoo TBzTD (tetrabenzylthiuram disulfide) is a product from Hebi Uhoo Rubber Chemicals Co., Ltd., ground sulfur from Avokal GmbH.

The rubber mixture is produced in three stages in an internal mixer according to Table 2.

Table 2:

The general method of producing rubber mixtures and vulcanizates thereof is described in W. Hofmann, H. Gupta, "Handbuch der Kautschuktechnologie", Dr. Gupta Verlag, Ratingen 2001 , chapter 10, pages 1-27 and 82-107. Rubber testing is effected in accordance with the test method specified in Table 3. Table 3:

Vulcanization is effected at a temperature of 165°C for a period of 12 minutes. Table 4 reports the rubber data for the vulcanizates.

Table 4:

The rubber mixtures containing the oligomeric silanes according to the invention show improved tear resistance over the reference mixtures.