Alkoxysilane polysulphide

Abstract

The invention relates to an alkoxysilane polysulfide, of formula (I):
(R.sup.3O).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z—S.sub.x—Z—HC(R.sup.2)—CH.sub.2—Si(R.sup.1).sub.n(OR.sup.3).sub.3-n  (I),
in which: R.sup.1, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 18 carbon atoms; R.sup.2, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 4 carbon atoms; R.sup.3, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 12 carbon atoms, preferably from 1 to 6 carbon atoms; Z, which are identical or different, each represent a divalent hydrocarbon bonding group comprising from 1 to 16 carbon atoms; x is an integral or fractional number greater than or equal to 2; and n is an integer equal to 0, 1 or 2.

Claims

1. An alkoxysilane polysulfide of formula (I):
(R.sup.3O).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z—S.sub.x—Z—HC(R.sup.2)—CH.sub.2—Si(R.sup.1).sub.n(OR.sup.3).sub.3-n  (I), in which: R.sup.1, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 18 carbon atoms; R.sup.2, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 4 carbon atoms; R.sup.3, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 12 carbon atoms; Z, which are identical or different, each represent a divalent hydrocarbon bonding group comprising from 1 to 16 carbon atoms; x is an integral or fractional number greater than or equal to 2; and n is an integer equal to 2.

2. The alkoxysilane polysulfide according to claim 1, wherein each R.sup.3 represents an ethoxy group.

3. The alkoxysilane polysulfide according to claim 1, wherein x is within a range extending from 2 to 4.

4. The alkoxysilane polysulfide according to claim 1, wherein each R.sup.1 is selected from the group consisting of C.sub.1-C.sub.6 alkyls, C.sub.5-C.sub.8 cycloalkyls and the phenyl radical, and each Z group is selected from the group consisting of C.sub.1-C.sub.16 alkylenes and C.sub.6-C.sub.12 arylenes.

5. The alkoxysilane polysulfide according to claim 4, wherein each R.sup.1 group is selected from the group consisting of C.sub.1-C.sub.3 alkyls, and each Z group is selected from the group consisting of methylene and ethylene.

6. The alkoxysilane polysulfide according to claim 5, wherein each R.sup.1 and R.sup.2 is methyl.

7. The alkoxysilane polysulfide according to claim 1, wherein the alkoxysilane polysulfide consists of bis(2-methylpropane-1,3-diyl)(dimethylethoxylsilane) polysulfide of formula: ##STR00012##

8. A process for producing an alkoxysilane polysulfide of formula (I) according to claim 1, the process comprising the following steps: carrying out hydrosilylation of an alkene of formula R.sup.2—C(CH.sub.2)Z-Hal, where Hal is halogen, with a hydrosilane of formula Hal.sub.3-n(R.sup.1).sub.nSi-H in order to give a halogenated organosilane of formula:
Hal.sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z-Hal  (A); carrying out alcoholysis, in an inert organic solvent, on the halogenated organosilane of formula (A) in the presence of an organic or inorganic base, in order to trap an acid halide formed, and of an alcohol, in order to obtain an alkoxysilane of formula:
(R.sup.3O).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z-Hal  (C); carrying out sulfidation on the alkoxysilane of formula (C), by the action of a polysulfide, in order to result in the alkoxysilane polysulfide of formula (I).

9. The process according to claim 8, wherein Hal is chlorine.

10. The process according to claim 8, wherein the organic base intended to trap the acid halide formed is a tertiary amine.

11. The process according to claim 8, wherein the polysulfide is an ammonium or metal polysulfide (x≥2), of formula M.sub.2S.sub.x or M′S.sub.x with M=alkali metal or NH.sub.4 and M′=Zn or alkaline earth metal.

12. The process according to claim 11, wherein the polysulfide is a sodium polysulfide Na.sub.2S.sub.x.

13. The process according to claim 8, wherein the sulfidation stage is carried out in the aqueous phase or in a two-phase water/organic solvent medium, in the presence of a phase transfer catalyst and of a salt of formula M″Hal or M″.sub.2SO.sub.4 with M″ chosen from Li, Na and K and Hal chosen from F, Cl and Br.

14. An elastomeric composition based on at least a diene elastomer, an inorganic filler as reinforcing filler and an alkoxysilane polysulfide as coupling agent, of formula (I):
(R.sup.3O).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z-S.sub.x-Z-HC(R.sup.2)—CH.sub.2-Si(R.sup.1).sub.n(OR.sup.3).sub.3-n  (I), in which: R.sup.1, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 18 carbon atoms; R.sup.2, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 4 carbon atoms; R.sup.3, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 12 carbon atoms; Z, which are identical or different, each represent a divalent hydrocarbon bonding group comprising from 1 to 16 carbon atoms; x is an integral or fractional number greater than or equal to 2; and n is an integer equal to 2.

15. The elastomeric composition according to claim 14, wherein x is within a range extending from 2 to 4.

16. The elastomeric composition according to claim 14, wherein each R.sup.1 group is selected from the group consisting of C.sub.1-C.sub.3 alkyls, and each Z group is selected from the group consisting of methylene and ethylene.

17. The elastomeric composition according to claim 14, wherein the alkoxysilane polysulfide of formula (I) consists of a bis(2-methylpropane-1,3-diyl)(dimethylethoxylsilane) polysulfide.

18. The elastomeric composition according to claim 14, wherein the diene elastomer is selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures thereof.

19. The elastomeric composition according to claim 14, wherein a content of reinforcing inorganic filler is between 30 and 150 phr, and the reinforcing filler is predominantly silica.

20. A tire comprising the elastomeric composition according to claim 14.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is the NMR spectra of bis(2-methylpropane-1,3-diyl)(triethoxylsilane) (product B1).

(2) FIG. 2 is the NMR spectra of bis(2-methylpropane-1,3-diyl)(dimethylethoxylsilane) (product B2).

DETAILED DESCRIPTION OF THE INVENTION

(3) Alkoxysilane Polysulfide of the Invention

(4) The first subject-matter of the invention is an alkoxysilane polysulfide, of formula (I)
(R.sup.3O).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z—S.sub.x—Z—HC(R.sup.2)—CH.sub.2—Si(R.sup.1).sub.n(OR.sup.3).sub.3-n (I) or in the semi-expanded form:

(5) ##STR00003##

(6) in which: R.sup.1, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 18 carbon atoms; R.sup.2, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 4 carbon atoms; R.sup.3, which are identical or different, each represent a monovalent hydrocarbon group having from 1 to 12 carbon atoms, preferably from 1 to 6 carbon atoms; Z, which are identical or different, each represent a divalent hydrocarbon bonding group comprising from 1 to 16 carbon atoms; x is an integral or fractional number greater than or equal to 2; n is an integer equal to 0, 1 or 2.

(7) Preferably, the R.sup.1 groups are chosen from C.sub.1-C.sub.6 alkyls, C.sub.5-C.sub.8 cycloalkyls and the phenyl radical, the Z groups being chosen from C.sub.1-C.sub.16 alkylenes and C.sub.6-C.sub.12 arylenes, and more preferably the R.sup.1 groups are chosen from C.sub.1-C.sub.3 alkyls, the Z groups being chosen from C.sub.1-C.sub.3 alkylenes.

(8) According to a preferred alternative embodiment of the invention, the polysulfide corresponds to the formula (OEt=ethoxy):
(EtO).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z—S.sub.x—Z—HC(R.sup.2)—CH.sub.2—Si(R.sup.1).sub.n(OEt).sub.3-n

(9) and, more preferably still, the polysulfide corresponds to the formula (Me=methyl):
(EtO).sub.3-n(Me).sub.nSi—CH.sub.2-(Me)CH—Z—S.sub.x—Z—HC(Me)-CH.sub.2—Si(Me).sub.n(OEt).sub.3-n

(10) Preferably, the Z groups are chosen from methylene and ethylene.

(11) The alkoxysilane polysulfides synthesized are in fact mixtures of polysulfides (for example from x=2 to x=9), with as consequence a mean value for x which is different from a whole value. The mean value targeted for x is preferably in a range extending from 2 to 6, more preferably in a range extending from 2 to 4.

(12) According to a preferred embodiment of the invention, n is equal to 0 and preferably the polysulfide consists of a bis(2-methylpropane-1,3-diyl)(triethoxylsilane) polysulfide of formula:

(13) ##STR00004##

(14) According to another preferred embodiment of the invention, n is equal to 2 and preferably the polysulfide consists of a bis(2-methylpropane-1,3-diyl)(dimethylethoxylsilane) polysulfide of formula:

(15) ##STR00005##

(16) Process of Synthesis

(17) The alkoxysilane polysulfide of formula (I) can be obtained by a process comprising the following stages: a hydrosilylation (Scheme 1 below) of an alkene of formula R.sup.2—C(CH.sub.2)Z-Hal (where Hal=halogen) with a hydrosilane of general formula Hal.sub.3-n(R.sup.1).sub.nSi—H is carried out in order to give a halogenated organosilane (hereinafter product A) of formula:
Hal.sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z-Hal

(18) ##STR00006##

(19) with R.sup.1, R.sup.2 and Z as defined above; an alcoholysis by the action of an alkoxyl donor is carried out, in an inert organic solvent, on the product A in the presence of an organic or inorganic base, in order to trap the acid halide formed, the alkoxyl donor being an alcohol, in order to obtain an alkoxysilane (product C) of formula:
(R.sup.3O).sub.3-n—(R.sup.1).sub.2Si—CH.sub.2—(R.sup.2)CH—Z-Hal

(20) with R.sup.3 as defined above; finally, a stage of sulfidation is carried out on the product C (Scheme 3), by the action of a polysulfide, in order to result in the targeted product of formula (I).

(21) According to an advantageous alternative to the process, the product C can be obtained by a hydrosilylation reaction of an alkene of formula R.sup.2—C(CH.sub.2)Z-Hal with a trialkoxyhydrosilane, as described, for example, by Mark D. Westmeyer in Application WO2005118598 or by Mark Paul Bowman in Application EP 0 669 338.

(22) According to the preferred embodiment corresponding to an ethoxysilane polysulfide, the second stage of the above process is carried out as follows: an ethanolysis is carried out, in an inert organic solvent, on the product A in the presence of an organic or inorganic base, in order to trap the acid halide formed, and of ethanol, in order to obtain an alkoxysilane (product C′) of formula:
(EtO).sub.3-n(R.sup.1).sub.nSi—CH.sub.2—(R.sup.2)CH—Z-Hal

(23) with R.sup.1, R.sup.2 and Z as defined above. The scheme of this reaction stage is as follows:

(24) ##STR00007## Finally, a stage of sulfidation is carried out on the product C (Scheme 3), by the action of a polysulfide, in order to result in the targeted product:

(25) ##STR00008##

(26) Advantageously, Hal is chlorine.

(27) Preferably, the organic base intended to trap the acid halide formed is a tertiary amine.

(28) According to an alternative embodiment of the process, the alkoxyl donor is used in excess with respect to the amount of product A.

(29) Advantageously, the polysulfide is an ammonium or metal polysulfide (x≥2), of formula M.sub.nS.sub.x or M′S.sub.x (M=alkali metal or NH.sub.4; M′=Zn or alkaline earth metal).

(30) Preferably, it is a sodium polysulfide Na.sub.2S.sub.x, preferably generated by the action of sulfur on Na.sub.2S.

(31) More preferably still, the sulfidation stage is carried out in the aqueous phase or in a two-phase water/organic solvent medium, in the presence of a phase transfer catalyst and of a salt of formula M″Hal or M″2504 (M″ chosen from Li, Na and K; Hal chosen from F, Cl and Br).

(32) Use as Coupling Agent

(33) As indicated above, the compound of the invention, by virtue of its twofold functionality, has an advantageous industrial application as coupling agent intended, for example, to provide the bonding or adhesion between a reactive polymeric matrix (in particular a rubber matrix) and any material having a hydroxylated surface, in particular an inorganic material (for example, a glass fibre) or a metal material (for example, a wire made of carbon steel or of stainless steel).

(34) Without this being limiting, it can be used in particular for the coupling of reinforcing inorganic or white fillers and diene elastomers, for example in rubber compositions intended for the manufacture of tyres. The term “reinforcing inorganic filler” is understood as meaning, in a known way, an inorganic or mineral filler, whatever its colour and its origin (natural or synthetic), also known as “white filler” or sometimes “clear filler”, in contrast to carbon black, this inorganic filler being capable of reinforcing, by itself alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of tyres, in other words capable of replacing, in its reinforcing role, a conventional tyre-grade carbon black filler.

(35) Thus, the invention also relates to elastomeric compositions based on at least a diene elastomer, an inorganic filler as reinforcing filler and an ethoxysilane polysulfide as coupling agent, of formula (I) as mentioned above.

(36) Advantageously, the diene elastomer is selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and the mixtures of these elastomers.

(37) For such a use, the diene elastomer is then preferably selected from the group of highly unsaturated diene elastomers consisting of polybutadienes (BRs), synthetic polyisoprenes (IRs), natural rubber (NR), butadiene/styrene copolymers (SBRs), butadiene/isoprene copolymers (BIRs), butadiene/acrylonitrile copolymers (NBRs), isoprene/styrene copolymers (SIRs), butadiene/styrene/isoprene copolymers (SBIRs) and the mixtures of these elastomers.

(38) When the ethoxysilane polysulfide of the invention is intended for coupling (inorganic filler/diene elastomer) in a rubber composition forming, for example, all or a portion of a passenger vehicle tyre tread, the diene elastomer is then preferably an SBR or a blend (mixture) of SBR and of another diene elastomer, such as BR, NR or IR. In the case of an SBR elastomer, use is made in particular of an SBR having a styrene content of between 20% and 30% by weight, a content of vinyl bonds of the butadiene part of between 15% and 65%, a content of trans-1,4-bonds of between 15% and 75% and a glass transition temperature (Tg—measured according to Standard ASTM D3418-82) of between −20° C. and −55° C., this SBR copolymer, preferably prepared in solution (SSBR), optionally being used as a mixture with a polybutadiene (BR) preferably having more than 90% of cis-1,4-bonds.

(39) When the tread is intended for a utility tyre, such as a heavy duty vehicle tyre, the diene elastomer is then preferably an isoprene elastomer, that is to say a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IRs), the various isoprene copolymers and the mixtures of these elastomers; it is then more preferably natural rubber or a synthetic polyisoprene of the cis-1,4-type having a content (mol %) of cis-1,4-bonds of greater than 90%, more preferably still of greater than 98%.

(40) The ethoxysilane polysulfides of the invention have proved to be sufficiently effective by themselves alone for the coupling of a diene elastomer and a reinforcing inorganic filler, such as silica, used in particular as predominant reinforcing filler. Preferably, the content of reinforcing filler will be chosen between 10 and 200 phr, more preferably between 30 and 150 phr, in particular greater than 50 phr, and more preferably still between 60 and 140 phr.

(41) Preferably, the ethoxysilane polysulfides are used at a content of greater than 1 phr (parts by weight per hundred parts of elastomer), more preferably of between 2 and 20 phr. They can advantageously constitute the sole coupling agent present in rubber compositions reinforced with inorganic filler and intended for the manufacture of tyres.

(42) Mention will be made, as reinforcing inorganic filler, of mineral fillers of the siliceous type, in particular silica (SiO.sub.2), or of the aluminous type, in particular alumina (Al.sub.2O.sub.3), or of aluminium (oxide) hydroxides, or also of reinforcing titanium oxides, as described in the abovementioned patents or patent applications.

(43) Highly dispersible precipitated silicas (HDSs) are preferred, in particular when the invention is employed in the manufacture of tyres exhibiting a low rolling resistance; mention may be made, as examples of such silicas, of the Ultrasil 7000 silicas from Evonik, the Zeosil 1165MP, 1135MP, 1115MP and Premium 200MP silicas from Solvay, the Hi-Sil EZ150G silica from PPG or the Zeopol 8715, 8745 and 8755 silicas from Huber.

(44) The reinforcing inorganic filler can be used also combined with a reinforcing organic filler, in particular carbon black.

(45) The amount of carbon black present in the total reinforcing filler can vary within wide limits; it is preferably less than that of the reinforcing inorganic filler. Advantageously, carbon black is used in a very low proportion, with a content of between 2 and 20 phr and preferably at a content of less than 10 phr.

(46) Such rubber compositions also comprise, in a known way, a crosslinking system, preferably a vulcanization system, that is to say a system based on sulfur (or on a sulfur-donating agent) and on a primary vulcanization accelerator. Additional to this base vulcanization system are various known secondary vulcanization accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (in particular diphenylguanidine), incorporated during the first non-productive phase and/or during the productive phase, as described subsequently.

(47) The sulfur is used at a preferred content of between 0.5 and 12 phr, in particular between 1 and 10 phr. The primary vulcanization accelerator is used at a preferred content of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr.

(48) According to a preferred alternative embodiment of the invention, zinc and any zinc derivative, such as ZnO, are excluded among the secondary vulcanization accelerators or vulcanization activators used or they can be used in accordance with the 0.5 phr maximum of zinc in the composition, and preferably less than 0.3 phr. Furthermore, according to another preferred alternative form, guanidine derivatives, such as diphenylguanidine, are excluded.

(49) The rubber compositions in accordance with the invention can also comprise all or a portion of the normal additives customarily used in elastomer compositions intended for the manufacture of tyres, in particular of treads, such as, for example, plasticizers or extender oils, whether the latter are aromatic or non-aromatic in nature, pigments, protective agents, such as antiozone waxes, chemical antiozonants or antioxidants, anti-fatigue agents, reinforcing resins, methylene acceptors (for example, phenolic novolak resin) or methylene donors (for example, HMT or H3M), such as described, for example, in Application WO 02/10269, a crosslinking system based either on sulfur or on sulfur-donating agents and/or on peroxide and/or on bismaleimides, vulcanization accelerators or vulcanization activators.

(50) Manufacture of the Rubber Compositions

(51) The rubber compositions of the invention are manufactured in appropriate mixers, using two successive phases of preparation according to a general procedure well known to a person skilled in the art: a first phase of thermomechanical working or kneading (sometimes described as “non-productive” phase) at high temperature, up to a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C., followed by a second phase of mechanical working (sometimes described as “productive” phase) at a lower temperature, typically of less than 120° C., for example between 60° C. and 100° C., during which finishing phase the crosslinking or vulcanization system is incorporated.

(52) It is possible to envisage one or more additional stages targeted at preparing masterbatches of elastomer and of reinforcing filler which are intended to be introduced during the first working phase.

(53) The compositions thus obtained are subsequently calendered in the form of plaques (thickness of 2 to 3 mm) or of thin sheets of rubber, for the measurement of their physical or mechanical properties, or extruded in order to form profiled elements which can be used directly, after cutting and/or assembling to the desired dimensions, for example as semi-finished products for tyres, in particular as tyre treads.

IMPLEMENTATIONAL EXAMPLES OF THE INVENTION

(54) The implementational examples which follow present in particular the synthesis of bis(2-methylpropane-1,3-diyl)(triethoxyl silane) (product B1) and of bis(2-methylpropane-1,3-diyl)(dimethylethoxylsilane) (product B2), illustrated by FIGS. 1 and 2, which represent the NMR spectra of each of these products.

Synthesis of Chloroisobutyltriethoxysilane

(55) This compound can be obtained by applying, to triethoxyhydrosilane, the procedure described, for example, by Mark D. Westmeyer in Application WO2005118598 or by Mark Paul Bowman in Application EP 0 669 338, i.e. a hydrosilylation reaction, catalysed by a ruthenium complex, with an alkene of formula R.sup.2—C(CH.sub.2)Z-Hal.

Synthesis of bis(2-methylpropane-1,3-diyl)(triethoxylsilane) (Product B1)

(56) ##STR00009##

(57) The reaction is carried out in a 2-litre round-bottomed flask equipped with a temperature control system, with a reflux condenser, with a mechanical stirrer and with a dropping funnel. The equipment is purged beforehand with nitrogen for 1 hour.

(58) Sulfur (10.41 g), sodium sulfide nonahydrate (44.48 g) and sodium chloride (33.14 g) are added to a two-phase mixture of water (665.0 g) and toluene (126.3 g). The temperature of the mixture is brought to 80° C. and the medium is stirred at this temperature for 120 minutes. The reaction medium becomes red from the time of the dissolution of the salts.

(59) Tetrabutylammonium chloride (9.94 g, in solution at 50% in toluene) is added at 86° C. Immediately afterwards, a solution of chloroisobutyltriethoxysilane (61.0 g) in toluene (457 g) is placed in the dropping funnel and is added dropwise. The addition lasts 2 hours and the temperature of the reaction medium is maintained between 84 and 86° C. After the end of the addition, the reaction medium is stirred for an additional 3 hours at 85° C. An analysis of the mixture by gas chromatography makes it possible to confirm the complete consumption of the starting chloroisobutyltriethoxysilane.

(60) The temperature of the reaction medium is slowly brought back to ambient temperature. The aqueous phase is separated. 800 ml of water are added to the organic phase. The mixture is stirred at ambient temperature and then the aqueous and organic phases are separated. This washing is repeated six times so that the pH of the phase is equal to 7.

(61) The organic phase is concentrated under at 30° C. at a pressure of less than 1 mm/Hg (affected by this pressure in 40 minutes). The oil obtained is concentrated under 1 mm/Hg at 30° C. for 1 h 30. 40 g of a brown oil are obtained.

(62) The NMR spectrum of the product B1 obtained is presented in FIG. 1.

Synthesis of bis(2-methylpropane-1,3-diyl)(dimethylethoxyl silane) (Product B2)

(63) ##STR00010##

(64) The reaction is carried out in a 2-litre round-bottomed flask equipped with a temperature control system, with a reflux condenser, with a mechanical stirrer and with a dropping funnel. The equipment is purged beforehand with nitrogen for 1 hour.

(65) Sulfur (10.33 g), sodium sulfide nonahydrate (44.49 g) and sodium chloride (33.45 g) are added to a two-phase mixture of water (365.0 g) and toluene (115.8 g). The temperature of the mixture is brought to 80° C. and the medium is stirred at this temperature for 120 minutes. The reaction medium becomes red from the time of the dissolution of the salts.

(66) Tetrabutylammonium chloride (10.5 g, in solution at 50% in toluene) is added at 86° C. Immediately afterwards, a solution of chloroisobutyldimethylethoxysilane (47.67 g) in toluene (449.91 g) is placed in the dropping funnel and is added dropwise. The addition lasts 2 hours and the temperature of the reaction medium is maintained between 84 and 86° C. After the end of the addition, the reaction medium is stirred for an additional 3 hours at 85° C. An analysis of the mixture by gas chromatography makes it possible to confirm the complete consumption of the starting chloroisobutyldimethylethoxysilane.

(67) The temperature of the reaction medium is slowly brought back to ambient temperature. The aqueous phase is separated. 800 ml of water are added to the organic phase. The mixture is stirred at ambient temperature and then the aqueous and organic phases are separated. This washing is repeated six times so that the pH of the phase is equal to 7.

(68) The organic phase is concentrated under at 30° C. at a pressure of less than 1 mm/Hg (affected by this pressure in 40 minutes). The oil obtained is concentrated under 1 mm/Hg at 30° C. for 1 h 30. 39 g of a brown oil are obtained.

(69) The NMR spectrum of the product B2 obtained is presented in FIG. 2.

(70) Preparation of the Rubber Compositions

(71) The tests which follow are carried out in the following way: the diene elastomer (or the mixture of diene elastomers, if appropriate), the reinforcing filler, the coupling agent and then the various other ingredients, with the exception of the vulcanization system, are introduced into an internal mixer which is 70% filled and which has an initial vessel temperature of approximately 60° C. Thermomechanical working is then carried out (non-productive phase) in one or two stages (total duration of the kneading equal to approximately 7 min), until a maximum “dropping” temperature of approximately 165° C. is reached. The mixture thus obtained is recovered and cooled and then sulfur and sulfenamide accelerator are added on an external mixer (homofinisher) at 30° C., everything being mixed (productive phase) for 3 to 4 minutes.

(72) The compositions thus obtained are subsequently calendered in the form of plaques (thickness of 2 to 3 mm) or of thin sheets of rubber, for the measurement of their physical or mechanical properties, or extruded in order to form profiled elements which can be used directly, after cutting and/or assembling to the desired dimensions, for example as semi-finished products for tyres, in particular as tyre treads.

(73) Measurements and Tests Used

(74) The rubber compositions are characterized, before and after curing, as indicated below.

(75) Tensile Tests

(76) These tests make it possible to determine the elasticity stresses and the properties at break. Unless otherwise indicated, they are carried out in accordance with French Standard NF T 46-002 of September 1988. The nominal secant moduli (or apparent stresses, in MPa) are measured in second elongation (i.e. after an accommodation cycle at the extension rate provided for the measurement itself) at 10% elongation (denoted M10), 100% elongation (denoted M100) and 300% elongation (denoted M300). The breaking stresses (in MPa) and the elongations at break (in %) are also measured. All these tensile measurements are carried out under the standard conditions of temperature and hygrometry according to French Standard NF T 40-101 (December 1979).

(77) Rheometry

(78) The measurements are carried out at 150° C. with an oscillating disc rheometer, according to Standard DIN 53529—Part 3 (June 1983). The change in the rheometric torque, ΔTorque, as a function of the time describes the change in the stiffening of the composition as a result of the vulcanization reaction. The measurements are processed according to Standard DIN 53529—Part 2 (March 1983): T.sub.0 is the induction period, that is to say the time necessary for the start of the vulcanization reaction; T.sub.α (for example T.sub.99) is the time necessary to achieve a conversion of α %, that is to say α % (for example 99%) of the difference between the minimum (TMin) and maximum (TMax) torques. The conversion rate constant, denoted K (expressed in min.sup.−1), which is first order, calculated between 30% and 80% conversion, which makes it possible to assess the vulcanization kinetics, is also measured.

(79) Test

(80) The aim of this test is to demonstrate the improved performance qualities of compositions in accordance with the invention, compared with a conventional composition using TESPT.

(81) Three compositions in accordance with the process explained in the preceding section, based on SBR, reinforced predominantly with silica, are thus prepared, which compositions differ from one another in the nature of their coupling agent, these coupling agents being used in an isomolar silicon content, and in the presence or the absence of zinc oxide (ZnO), as follows: the conventional control composition C1, not in accordance with the invention, comprises, as coupling agent, TESPT and also, conventionally, ZnO, the control composition C2, not in accordance with the invention, comprises, as coupling agent, a conventional silane disulfide and also, conventionally, ZnO, the composition C3, in accordance with the invention, comprises, as coupling agent, the product B1 and also ZnO, the composition C4, in accordance with the invention, comprises, as coupling agent, the product B1 but is devoid of ZnO.

(82) It should be remembered that TESPT is bis(3-triethoxysilylpropyl) tetrasulfide, of formula [(C.sub.2H.sub.5O).sub.3Si(CH.sub.2).sub.3S.sub.2].sub.2; it is sold, for example, by Evonik under the name Si69 (or X50S when it is supported at 50% by weight on carbon black) or also by Witco under the name Silquest A1289 (in both cases, commercial mixture of polysulfides S.sub.x with a mean value for x which is approximately 4).

(83) The expanded formula for TESPT is:

(84) ##STR00011##

(85) Likewise, the silane disulfide coupling agent bis(triethoxysilylpropyl) disulfide, such as sold by Evonik under the reference Si75, is well known.

(86) The formulation of the four compositions (contents of the various products expressed in phr) and their properties after curing (approximately 30 min at 150° C.) are given in Tables 1 and 2 respectively.

(87) It is found, in the light of Table 2, surprisingly, that the compositions C3 and C4 in accordance with the invention exhibit reinforcing (M300/M100) properties which are significantly improved in comparison with the two control compositions C1 and C2 and also a marked improvement in the processability (Tmin). Surprisingly, it is found that these improvements in performance qualities for the compositions in accordance with the invention take place equally well in compositions with ZnO as in compositions without ZnO.

(88) TABLE-US-00001 TABLE 1 Compositions C1 C2 C3 C4 SBR (1) 100 100 100 100 Carbon black (2) 4 4 4 4 Silica (3) 110 110 110 110 Silane (4) 8.8 — — Silane (5) 8.1 Silane (6) — — 9.0 9.0 Resin (7) 45 45 45 45 Oil (8) 17 17 17 17 Octadecylamine 1.8 1.8 1.8 1.8 wax DPG (9) 2 2 2 2 ZnO 1 1 1 — Stearic acid 2 2 2 2 Antioxidant (10) 2.7 2.7 2.7 2.7 Sulfur* 1.1 1.8 1.8 1.8 Accelerator (11) 2.3 2.3 2.3 2.3 (1) SBR with 27% of styrene units and 24% of 1,2- units of the butadiene part (Tg = −48° C.) bearing a silanol functional group at the elastomer chain end, and comprising as a minor component by weight chains of the same microstructure but Sn star-branched; (2) Carbon black N234, sold by Cabot Corporation; (3) “HD”-type silica, Zeosil 1165MP from Solvay; (4) TESPT (Si69 ® from Evonik); (5) Si75 ® (bis(triethoxysilylpropyl) disulfide from Evonik); (6) Product B1 (bis(2-methylpropane-1,3-diyl)(triethoxylsilane) (product B1)); (7) Polylimonene resin (Resine THER 8644 from Cray Valley); (8) Sunflower oil, Lubrirob Tod 1880 from Novance; (9) Diphenylguanidine (Vulkacit D from Bayer); (10) N-(1,3-Dimethylbutyl)-N′-phenyl-para-phenylenediamine (Santoflex 6-PPD from Flexsys); (11) N-Cyclohexyl-2-benzothiazolesulfenamide (Santocure CBS from Flexsys). *The sulfur contents were adjusted in order to take into account the release of sulfur which takes place with TESPT not with the products Si75 or B1 (disulfide S.sub.2 foot).

(89) TABLE-US-00002 TABLE 2 Compositions C1 C2 C3 C4 Properties in the raw condition Tmin 1.46 1.47 1.33 1.36 Properties in the cured condition M300/M100 1.46 1.56 1.58 1.67