Rubber composition

Abstract

The present invention relates to a rubber composition comprising a highly saturated diene elastomer, a vulcanization system, a reinforcing filler and an azosilane coupling agent, the highly saturated diene elastomer being a copolymer of ethylene and 1, 3-diene, the copolymer comprising ethylene units constituting more than 50 mol% of the monomer units of the copolymer, the reinforcing filler comprises silica.

Description

Field of the Invention

[0001] The field of the invention is that of rubber compositions comprising silica and highly saturated diene elastomers, said rubber compositions being intended in particular for tire manufacture. Background Art

[0002] For example, from documents WO 2014114607 A1 and WO 2018224776 A1, it is known to use rubber compositions reinforced with silica and comprising highly saturated diene elastomers. Highly saturated diene elastomers are copolymers of ethylene and 1,3-dienes (such as 1,3-butadiene), and their distinguishing feature is that they contain more than 50 mol% of ethylene units. Due to their high ethylene content and low diene unit content of less than 50 mol%, they are significantly different from the diene elastomers conventionally used in rubber compositions (which generally contain more than 50 mol% of diene units, such as polybutadiene, polyisoprene, and copolymers of 1,3-butadiene or isoprene with styrene). In particular, they have the distinguishing feature of conferring on the rubber composition a different compromise between stiffness and hysteresis than that conferred by the diene elastomers conventionally used.

[0003] Since the need to save fuel and protect the environment has become a priority, it is desirable to produce mixtures having good abrasion resistance properties while having the lowest possible hysteresis, so that they can be processed into the form of rubber compositions that can be used to manufacture the various semi-finished products (such as treads) involved in tire compositions, thereby obtaining tires having improved abrasion resistance without adversely affecting rolling resistance.

[0004] To improve abrasion resistance, it is known that it is desirable for the tread to have a certain stiffness, for example, this strengthening of the tread can be obtained by increasing the content of reinforcing fillers in the rubber compositions constituting these treads. Unfortunately, experience has shown that this strengthening of the tread has a known and generally discouraging adverse effect on the rolling resistance properties, since it is accompanied by a significant increase in the loss of hysteresis of the rubber composition.

[0005] Therefore, improving stiffness performance while maintaining low rolling resistance has received continuous attention from tire designers. In view of the above, the general objective is to provide rubber compositions for tires, said rubber compositions satisfying an improved compromise between stiffness and hysteresis for tires (especially treads), thereby improving the performance compromise between wear and rolling resistance.

[0006] The inventors have found a rubber composition that combines a very high level of stiffness and a very low level of hysteresis. Summary of the Invention

[0007] Accordingly, the present invention relates to a rubber composition comprising:

[0008] - A highly saturated diene elastomer, which is a copolymer of ethylene and a 1,3-diene, and the copolymer contains more than 50 mol% of ethylene units based on the monomer units of the copolymer.

[0009] - A vulcanization system

[0010] - A reinforcing filler, which contains silica

[0011] - And a silane coupling agent of formula (1)

[0012] (G1) 3-a (G2) a Si-Z-NH-C(O)-N=N-G4(1)

[0013] Wherein:

[0014] - G1 are the same or different and each represents a C1-C8 alkyl group

[0015] - G2 are the same or different and each represents a hydroxyl group or a C1-C8 alkoxy group

[0016] - G4 represents an aromatic group

[0017] - Z represents a C1-C8 alkanediyl group

[0018] - a is equal to 1, 2 or 3.

[0019] The present invention also relates to a tire, which contains the rubber composition according to the present invention, preferably in its tread. Detailed Description

[0020] Any numerical interval represented by the expression "between a and b" represents a numerical range greater than "a" and less than "b" (i.e., excluding the end values a and b), while any numerical interval represented by the expression "from a to b" means a numerical range extending from "a" to "b" (i.e., including the exact end values a and b).

[0021] The abbreviation "phr" means parts by weight per hundred parts of elastomer (if there are several elastomers, the sum of the elastomers).

[0022] In the disclosure of the present invention, the name "C n - C m group" is used to represent a group having n to m carbon atoms, where n is an integer greater than or equal to 1 and m is an integer greater than n. For example, C1-C8 alkyl represents an alkyl group having 1 to 8 carbon atoms, C1-C8 alkoxy represents an alkoxy group having 1 to 8 carbon atoms, C1-C8 alkanediyl represents an alkanediyl group having 1 to 8 carbon atoms, and C6-C12 Aryl means an aryl group having 6 to 12 carbon atoms.

[0023] The compounds mentioned in the specification can be compounds of fossil origin or can be biobased compounds. In the case where the compounds are biobased compounds, they can be partially or fully derived from biomass or can be obtained from renewable starting materials derived from biomass. In the same way, the mentioned compounds can also be sourced from the recycling of pre-used materials, that is to say, they can be partially or fully from a recycling process or can be obtained from starting materials that themselves come from a recycling process.

[0024] In the present invention, the term "tire" is understood to mean a pneumatic tire or a non-pneumatic tire. A pneumatic tire generally includes two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, and two sidewalls, and the tire is reinforced by a carcass reinforcement anchored in the two beads. By itself, a non-pneumatic tire generally includes a base designed to be mounted, for example, on a rigid rim, a crown reinforcement ensuring the connection to the tread, and a deformable structure such as spokes, ribs or cells located between the base and the crown. Such a non-pneumatic tire does not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077. According to any embodiment of the present invention, the tire according to the present invention is preferably a pneumatic tire.

[0025] Unless otherwise indicated, the content of the units resulting from the insertion of monomers into a copolymer (such as the copolymers useful in the present invention) is expressed as a mole percentage relative to all the monomer units of the copolymer.

[0026] The elastomers useful for the purposes of the present invention are highly saturated diene elastomers, which are preferably statistical diene elastomers and contain ethylene units resulting from the polymerization of ethylene. In a known manner, the expression "ethylene unit" means a -(CH2-CH2)- unit resulting from the insertion of ethylene into the elastomer chain. The highly saturated diene elastomers are rich in ethylene units since the ethylene units represent more than 50 mol% of all the monomer units of the elastomer.

[0027] Preferably, the highly saturated diene elastomer contains at least 60 mol% of ethylene units, preferably at least 65 mol% of ethylene units. In other words, the ethylene units in the highly saturated diene elastomer preferably represent at least 60 mol% of all the monomer units of the highly saturated diene elastomer, more preferably at least 65 mol% of all the monomer units of the highly saturated diene elastomer.

[0028] Preferably, the ethylene units in the highly saturated diene elastomer account for no more than 90 mol% of all monomer units of the highly saturated diene elastomer. More preferably, the ethylene units account for no more than 85 mol% of all monomer units of the highly saturated diene elastomer. Even more preferably, the ethylene units account for no more than 80 mol% of all monomer units of the highly saturated diene elastomer.

[0029] According to an advantageous embodiment, the highly saturated diene elastomer contains from 60 mol% to 90 mol% of ethylene units, in particular from 60 mol% to 85 mol% of ethylene units, the mole percentages being calculated based on all monomer units of the highly saturated diene elastomer. More advantageously, the highly saturated diene elastomer contains from 60 mol% to 80 mol% of ethylene units, the mole percentages being calculated based on all monomer units of the highly saturated diene elastomer.

[0030] According to another advantageous embodiment, the highly saturated diene elastomer contains from 65 mol% to 90 mol% of ethylene units, in particular from 65 mol% to 85 mol% of ethylene units, the mole percentages being calculated based on all monomer units of the highly saturated diene elastomer. More advantageously, the highly saturated diene elastomer contains from 65 mol% to 80 mol% of ethylene units, the mole percentages being calculated based on all monomer units of the highly saturated diene elastomer.

[0031] Since the highly saturated diene elastomer is a copolymer of ethylene and a 1,3-diene, it also contains 1,3-diene units resulting from the polymerization of the 1,3-diene. In a known manner, the expression "1,3-diene unit" or "diene unit" refers to the unit resulting from the insertion of a 1,3-diene by 1,4 addition, 1,2 addition or 3,4 addition (for example in the case of isoprene). The 1,3-diene unit is, for example, a 1,3-diene unit of a 1,3-diene containing from 4 to 12 carbon atoms, such as 1,3-butadiene, isoprene, 1,3-pentadiene or aryl-1,3-butadiene. Preferably, the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes (one of which is 1,3-butadiene). More preferably, the 1,3-diene is 1,3-butadiene, in which case the highly saturated diene elastomer is a copolymer of ethylene and 1,3-butadiene, preferably a statistical copolymer.

[0032] Highly saturated diene elastomers can be obtained according to various synthesis methods known to those skilled in the art, in particular according to the target microstructure of the highly saturated diene elastomers. Generally, it can be prepared by copolymerization of at least 1,3-diene (preferably 1,3-butadiene) with ethylene according to known synthesis methods (in particular in the presence of a catalytic system comprising a metallocene complex). In this regard, mention may be made of the catalytic systems based on metallocene complexes described in EP 1092731, WO 2004 / 035639, WO2007 / 054223 and WO 2007 / 054224 in the name of the present applicant. Highly saturated diene elastomers (including the case where it is a statistical diene elastomer) can also be prepared by a method using a preformed type of catalytic system (such as the catalytic systems described in WO2017 / 093654 A1, WO 2018 / 020122A1 and WO 2018 / 020123A1). Advantageously, the diene elastomer is a statistical diene elastomer and is preferably prepared by the semi-continuous or continuous processes described in documents WO 2017103543 A1, WO201713544 A1, WO 2018193193 and WO 2018193194.

[0033] The highly saturated diene elastomer preferably contains units of formula (I) or units of formula (II).

[0034]

[0035] -CH2-CH(CH=CH2)- (II)

[0036] The presence of the saturated six-membered ring units (1,2-cyclohexanediyl) of formula (I) in the copolymer can be generated by a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during the growth of the polymer chain. When the highly saturated diene elastomer contains units of formula (I) or units of formula (II), the molar percentages (o and p respectively) of the units of formula (I) and the units of formula (II) in the highly saturated diene elastomer preferably satisfy the following equation (Equation 1) or equation (Equation 2), where o and p are calculated based on all the monomer units of the highly saturated diene elastomer.

[0037] 0 < o + p ≤ 30 (Equation 1)

[0038] 0 < o + p < 25 (Equation 2)

[0039] Preferably, the highly saturated diene elastomer contains units of formula (I) in a molar content greater than 0 mol% and less than 15 mol%, more preferably less than 10 mol%, based on all the monomer units of the highly saturated diene elastomer.

[0040] In addition to the highly saturated diene elastomer, the rubber composition may further comprise a second diene elastomer. The term "diene elastomer" means an elastomer that is at least partially (i.e., homopolymer or copolymer) derived from diene monomer units (monomers having two conjugated or non-conjugated carbon-carbon double bonds). The second elastomer may be selected from highly unsaturated diene elastomers consisting of polybutadiene, polyisoprene, butadiene copolymers, isoprene copolymers, and mixtures thereof. A highly unsaturated elastomer is an elastomer containing more than 50% (mol%) of diene units.

[0041] Preferably, the content of the highly saturated diene elastomer in the rubber composition is at least 50 parts by weight per 100 parts by weight of elastomer of the rubber composition (phr). More preferably, the content of the highly saturated diene elastomer in the rubber composition varies in the range of 80 phr to 100 phr. Even more preferably, it varies in the range of 90 phr to 100 phr. Advantageously, it is 100 phr. The highly saturated diene elastomer may be a single highly saturated diene elastomer or a mixture of highly saturated diene elastomers having different microstructures or macrostructures from each other. In the case where the rubber composition contains several highly saturated diene elastomers having different microstructures or macrostructures from each other, the content of the highly saturated diene elastomer in the rubber composition refers to the mixture of highly saturated diene elastomers.

[0042] The silica used may be any reinforcing silica known to those skilled in the art, particularly any precipitated silica or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably in the range of 30 m 2 / g to 400 m 2 / g, particularly in the range of 60 m 2 / g to 300 m 2 / g. In the present invention, the BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Volume 60, page 309, February 1938), more particularly according to the method [multi-point (5 points) volume method - gas: nitrogen - degassing under vacuum: 1 hour at 160 °C - relative pressure p / po range: 0.05 to 0.17] derived from the standard NF ISO 5794-1 (Appendix E) of June 2010. The CTAB specific surface area value is determined according to the standard NF ISO 5794-1 (Appendix G) of June 2010. The method is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "outer" surface of the reinforcing filler.

[0043] Any type of precipitated silica can be used, in particular highly dispersible precipitated silica (HDS, meaning "highly dispersible silica"). These precipitated silicas (which may or may not be highly dispersible) are well known to those skilled in the art. For example, mention may be made of the silicas described in patent applications WO 03 / 016215 - A1 and WO 03 / 016387 - A1. Among commercial HDS silicas, in particular, 5000GR and 7000GR silica from company Evonik or 1085GR, 1115MP, 1165MP, Premium 200MP and HRS1200MP silica from company Solvay. As non - HDS silica, the following commercial silicas can be used: VN2GR and VN3GR silica from company Evonik, 175GR silica from company Solvay or Hi - Sil EZ120G(-D), Hi - Sil EZ160G(-D), Hi - Sil EZ200G(-D), Hi - Sil 243LD, Hi - Sil 210 and Hi - Sil HDP320G silica from company PPG.

[0044] Reinforcing fillers may include any type of "reinforcing" filler other than silica known to be capable of reinforcing rubber compositions that can be used particularly for manufacturing tires, such as carbon black. Suitable carbon blacks include all carbon blacks, especially those conventionally used in tires or their treads. Among said carbon blacks, reinforcing carbon blacks of series 100, 200, and 300, or carbon blacks of series 500, 600, or 700 (ASTM D - 1765 - 2017 grades) will be more particularly mentioned, such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 carbon blacks. These carbon blacks can be used in the form of commercially available isolates, or in any other form (such as as a carrier for some rubber engineering additives used). When carbon black is used in a rubber composition, it is preferably present in an amount less than or equal to 10 phr (for example, the carbon black content can be in the range of 1 phr to 10 phr). Advantageously, the carbon black content in the rubber composition is less than or equal to 5 phr. Within the specified range, the coloring property (black colorant) and UV stabilizing property of carbon black are utilized without adversely affecting the typical property quality produced by silica.

[0045] Silica preferably accounts for more than 50 mass% of the reinforcing filler. In other words, the proportion of silica in the reinforcing filler is more than 50% by weight relative to the total weight of the reinforcing filler. More preferably, silica accounts for more than 85 mass% of the reinforcing filler.

[0046] The total content of the reinforcing filler can vary within a wide range, for example, from 30 phr to 150 phr. According to a first embodiment, the total content of the reinforcing filler varies within the range of 30 phr to 60 phr. According to a second embodiment, the total content of the reinforcing filler varies within the range of more than 60 phr to 150 phr. For a tread where the rubber composition is used to have a very low rolling resistance, the first embodiment is superior to the second embodiment. Any of these ranges of the total content of the reinforcing filler can be applicable to any embodiment of the present invention.

[0047] The essential feature of the rubber composition according to the present invention is that it contains a silane of formula (1)

[0048] (G1) 3-a (G2) a Si - Z - NH - C(O) - N=N - G4(1)

[0049] wherein:

[0050] - G1 are the same or different and each represents a C1 - C8 alkyl group;

[0051] - G2 are the same or different and each represents a hydroxyl group or a C1 - C8 alkoxy group,

[0052] - G4 represents an aromatic group,

[0053] - Z represents a C1-C8 alkanediyl group,

[0054] - a is equal to 1, 2 or 3.

[0055] The silane of formula (1) is a coupling agent (or binder) which is intended to ensure a sufficient chemical and / or physical property connection between silica and the diene elastomer.

[0056] Preferably, G2 are the same or different and each represents a C1-C4 alkoxy group. More preferably, G2 are the same or different and each represents a methoxy or ethoxy group.

[0057] Preferably, G1 are the same or different and each represents a methyl or ethyl group.

[0058] G4 is an aromatic hydrocarbon group or an aromatic group containing a heteroatom (such as a nitrogen atom, an oxygen atom or a sulfur atom). Preferably, G4 is a C6-C 12 aryl group; more preferably, G4 represents a phenyl or tolyl group.

[0059] Preferably, Z represents a C1-C4 alkanediyl group. More preferably, Z represents 1,3-propanediyl.

[0060] According to any one of the embodiments of the present invention, a is preferably equal to 3.

[0061] Advantageously, the silane coupling agent of formula (1) is a compound in which G2 each represents an ethoxy group, G1 each represents a methyl group, G4 represents a phenyl group, Z represents 1,3-propanediyl, and a is equal to 1, 2 or 3. More advantageously, the silane coupling agent of formula (1) is a compound in which G2 each represents an ethoxy group, G4 represents a phenyl group, Z represents 1,3-propanediyl, and a is equal to 3.

[0062] The silane coupling agent of formula (1) can be prepared according to the synthesis method described in the patent application WO2015162053A1.

[0063] In the rubber composition according to the present invention, those skilled in the art adjust the content of the silane coupling agent of formula (1) according to the specific surface area of the silica used in the rubber composition and according to the silica content in the rubber composition. According to any one of the embodiments of the present invention, its range is preferably from 1 phr to 15 phr, more preferably from 1.5 phr to 10 phr, and even more preferably from 2 phr to 5 phr.

[0064] Another essential feature of the rubber composition according to the invention lies in its inclusion of a vulcanization system, namely a sulfur-based crosslinking system. Sulfur is generally provided in the form of molecular sulfur or sulfur donors, preferably in molecular form. Molecular sulfur is also referred to by the term "molecular sulfur". The term "sulfur donor" means any compound that releases sulfur atoms, which are optionally bound in the form of polysulfide chains and which are capable of inserting into the polysulfide chains formed during vulcanization and bridging the elastomer chains. Various known secondary vulcanization accelerators or vulcanization activators (such as zinc oxide, stearic acid, etc.) are added to the vulcanization system, which is introduced during the course of the first non-production phase and / or during the production phase. The sulfur content is preferably between 0.5 phr and 4 phr, and the primary accelerator content is preferably between 0.5 phr and 5 phr. These preferred contents can be applied to any embodiment of the present invention.

[0065] As (primary or secondary) vulcanization accelerators, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, in particular thiazole accelerators and their derivatives, sulfenamide accelerators (as primary accelerators) or thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate accelerators (as secondary accelerators). As examples of primary accelerators, mention may be made in particular of sulfenamide compounds such as N-cyclohexyl-2-benzothiazole sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazole sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazole sulfenamide ("TBBS") and mixtures of these compounds. The primary accelerator is preferably a sulfenamide, more preferably N-cyclohexyl-2-benzothiazole sulfenamide. As examples of secondary accelerators, mention may be made in particular of thiuram disulfides such as tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide ("TBTD"), tetrabenzyl thiuram disulfide ("TBZTD") and mixtures of these compounds. The secondary accelerator is preferably a thiuram disulfide, more preferably tetrabenzyl thiuram disulfide.

[0066] Vulcanization is carried out in a known manner at a temperature generally between 130 °C and 200 °C for a sufficient time, which can vary, for example, between 5 minutes and 90 minutes, depending in particular on the curing temperature, the vulcanization system employed and the vulcanization kinetics of the composition under consideration.

[0067] The rubber composition according to the invention may also contain all or some of the common additives usually used in elastomer compositions intended for tire manufacture, in particular pigments, protective agents (such as anti-ozone waxes, chemical anti-ozone agents, antioxidants) or plasticizers (such as plasticizing oils or resins).

[0068] Before vulcanization, the rubber composition can be manufactured in two successive preparation stages in a suitable mixer according to procedures known to those skilled in the art: a first stage of thermomechanical working or kneading at a high temperature (up to a maximum temperature between 110°C and 190°C, preferably between 130°C and 180°C) (sometimes called the "non - productive" stage), followed by a second stage of mechanical working at a lower temperature (usually below 110°C, for example between 40°C and 100°C) (sometimes called the "productive" stage), during which sulfur or a sulfur donor and a vulcanization accelerator are introduced.

[0069] For example, the first (non - productive) stage is carried out in a single thermomechanical step, during which all the necessary ingredients, optional additional processing aids, and various other additives (except the vulcanization system) are introduced into a suitable mixer (such as a conventional closed mixer). The total kneading time in this non - productive stage is preferably between 1 minute and 15 minutes. After cooling the mixture thus obtained during the first non - productive stage, the vulcanization system is then usually introduced into an open mixer (such as a mill) at a low temperature; then all the substances are mixed (productive stage) for several minutes, for example between 2 minutes and 15 minutes.

[0070] The rubber composition can be calendered or extruded in the form of sheets or plates (especially for laboratory characterization), or in the form of rubber semi - finished products (or shaped elements) that can be used for tires. The composition can be in an unprocessed state (before cross - linking or vulcanization), or in a cured state (after cross - linking or vulcanization). It can consist of all or part of the semi - finished products, especially intended for use in pneumatic or non - pneumatic tires (especially tire treads) including the tread.

[0071] In summary, the present invention is advantageously implemented according to any one of the following embodiments 1 to 29:

[0072] Embodiment 1: A rubber composition, the rubber composition comprising:

[0073] - A highly saturated diene elastomer, which is a copolymer of ethylene and a 1,3 - diene, the copolymer containing more than 50 mol% of ethylene units based on the monomer units of the copolymer,

[0074] - A vulcanization system,

[0075] - A reinforcing filler, the reinforcing filler containing silica,

[0076] - And a silane coupling agent of formula (1)

[0077] (G1) 3-a (G2) aSi-Z-NH-C(O)-N=N-G4(1)

[0078] wherein:

[0079] -G1 is the same or different and each represents a C1-C8 alkyl group;

[0080] -G2 is the same or different and each represents a hydroxyl group or a C1-C8 alkoxy group;

[0081] -G4 represents an aromatic group or a heteroaromatic group;

[0082] -Z represents a C1-C8 alkanediyl group;

[0083] -a is equal to 1, 2 or 3.

[0084] Embodiment 2: The rubber composition according to Embodiment 1, wherein the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes (one of which is 1,3-butadiene).

[0085] Embodiment 3: The rubber composition according to Embodiment 1 or 2, wherein the 1,3-diene is 1,3-butadiene.

[0086] Embodiment 4: The rubber composition according to any one of Embodiments 1 to 3, wherein the ethylene units of the highly saturated diene elastomer account for at least 60 mol% of all the monomer units of the highly saturated diene elastomer.

[0087] Embodiment 5: The rubber composition according to any one of Embodiments 1 to 4, wherein the ethylene units of the highly saturated diene elastomer account for at least 65 mol% of all the monomer units of the highly saturated diene elastomer.

[0088] Embodiment 6: The rubber composition according to any one of Embodiments 1 to 5, wherein the ethylene units of the highly saturated diene elastomer account for at least 70 mol% of all the monomer units of the highly saturated diene elastomer.

[0089] Embodiment 7: The rubber composition according to any one of Embodiments 1 to 6, wherein the ethylene units of the highly saturated diene elastomer account for not more than 90 mol% of all the monomer units of the highly saturated diene elastomer.

[0090] Embodiment 8: The rubber composition according to any one of Embodiments 1 to 7, wherein the ethylene units of the highly saturated diene elastomer account for not more than 85 mol% of all the monomer units of the highly saturated diene elastomer.

[0091] Embodiment 9: The rubber composition according to any one of Embodiments 1 to 8, wherein the ethylene units of the highly saturated diene elastomer account for no more than 80 mol% of all monomer units of the highly saturated diene elastomer.

[0092] Embodiment 10: The rubber composition according to any one of Embodiments 1 to 9, wherein the highly saturated diene elastomer contains units of formula (I) or units of formula (II).

[0093]

[0094] -CH2-CH(CH=CH2)- (II)

[0095] Embodiment 11: The rubber composition according to any one of Embodiments 1 to 10, wherein the highly saturated diene elastomer contains units of formula (I) in a molar content greater than 0 mol% and less than 15 mol%, the molar percentage being calculated based on all monomer units of the highly saturated diene elastomer.

[0096]

[0097] Embodiment 12: The rubber composition according to any one of Embodiments 1 to 11, wherein the highly saturated diene elastomer contains units of formula (I) in a molar content greater than 0 mol% and less than 10 mol%, the molar percentage being calculated based on all monomer units of the highly saturated diene elastomer.

[0098]

[0099] Embodiment 13: The rubber composition according to any one of Embodiments 1 to 12, wherein the highly saturated diene elastomer is a statistical copolymer.

[0100] Embodiment 14: The rubber composition according to any one of Embodiments 1 to 13, wherein the content of the highly saturated diene elastomer is at least 50 parts by weight per hundred parts of elastomer of the rubber composition (phr).

[0101] Embodiment 15: The rubber composition according to any one of Embodiments 1 to 14, wherein the content of the highly saturated diene elastomer varies in the range of 80 phr to 100 phr.

[0102] Embodiment 16: The rubber composition according to any one of Embodiments 1 to 15, wherein the total content of the reinforcing filler varies in the range of 30 phr to 150 phr.

[0103] Embodiment 17: The rubber composition according to any one of Embodiments 1 to 16, wherein the total content of the reinforcing filler varies in the range of 30 phr to 60 phr.

[0104] Embodiment 18: The rubber composition according to any one of Embodiments 1 to 17, wherein the silica accounts for more than 50% by mass of the reinforcing filler.

[0105] Embodiment 19: The rubber composition according to any one of Embodiments 1 to 18, wherein the silica accounts for more than 85% by mass of the reinforcing filler.

[0106] Embodiment 20: The rubber composition according to any one of Embodiments 1 to 19, wherein G2 are the same or different and each represents a C1-C4 alkoxy group.

[0107] Embodiment 21: The rubber composition according to any one of Embodiments 1 to 20, wherein G2 are the same or different and each represents a methoxy group or an ethoxy group.

[0108] Embodiment 22: The rubber composition according to any one of Embodiments 1 to 21, wherein G1 are the same or different and each represents a methyl group or an ethyl group.

[0109] Embodiment 23: The rubber composition according to any one of Embodiments 1 to 22, wherein G4 is a C6-C 12 aryl group.

[0110] Embodiment 24: The rubber composition according to any one of Embodiments 1 to 23, wherein G4 represents a phenyl group or a tolyl group.

[0111] Embodiment 25: The rubber composition according to any one of Embodiments 1 to 24, wherein Z represents a C1-C4 alkanediyl group.

[0112] Embodiment 26: The rubber composition according to any one of Embodiments 1 to 25, wherein Z represents a 1,3-propanediyl group.

[0113] Embodiment 27: The rubber composition according to any one of Embodiments 1 to 26, wherein a is equal to 3.

[0114] Embodiment 28: A tire comprising the rubber composition as defined in any one of Embodiments 1 to 27.

[0115] Embodiment 29: A tire, wherein the tire comprises the rubber composition as defined in any one of Embodiments 1 to 27 in its tread.

[0116] The above and other features of the present invention will be more clearly understood by reading the following description of multiple exemplary embodiments of the present invention given as non-limiting illustrations.

[0117] Examples

[0118] Kinetic properties

[0119] The kinetic properties G* and tan(δ)max were measured on a viscometer (Metravib VA4000) according to standard ASTM D 5992-96. According to standard ASTM D 1349-99, under standard temperature conditions (23 °C), the response of a vulcanized composition sample (cylindrical specimen, 4 mm thick, cross-sectional area 400 mm 2 ) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz was recorded. A strain amplitude sweep was carried out from 0.1% to 100% (outward cycle) and then from 100% to 0.1% (return cycle). The results used were the complex dynamic shear modulus (G*), the loss factor tan(δ), and the modulus difference ΔG* (Payne effect) between the values at 0.1% strain and 50% strain. For the return cycle, the maximum value of the observed tan(δ) was shown and denoted as tan(δ)max.

[0120] The results used were the complex shear modulus (G*), the loss factor tan(δ), and the modulus difference ΔG* (Payne effect) between the values at 0.1% strain and 50% strain. For the return cycle, the maximum value of the observed tan(δ) was shown and denoted as tan(δ)max. The complex modulus G * (denoted by G * ), the modulus difference ΔG * (Payne effect) between the values at 0.1% strain and 50% strain, and the value of tan(δ)max were given on a scale of 100, with a value of 100 assigned to the control composition (T).

[0121] The response of a vulcanized composition sample (cylindrical specimen, 4 mm thick, cross-sectional area 400 mm 2 ) subjected to a simple alternating sinusoidal shear stress (applied stress 0.7 MPa, frequency 10 Hz) during a temperature sweep (from the lowest temperature below the Tg of the elastomer of the composition up to the highest temperature above 100 °C) was also recorded. The result used was the complex dynamic shear modulus (G*); the value of G* was measured at a temperature of 60 °C.

[0122] The stiffness (G*) and hysteresis (tan(δ)max and ΔG*) results are expressed on a base of 100 relative to the control as a reference. Values ​​less than 100 indicate values ​​less than the control. The lower the value of ΔG*, the lower the nonlinearity that is the cause of hysteresis. The lower the value of tan(δ)max, the lower the hysteresis of the rubber composition. The lower the value of G*, the lower the stiffness of the composition.

[0123] Nuclear magnetic resonance (NMR) analysis of the microstructure of elastomers:

[0124] The microstructure of the elastomer is composed of 1 H NMR analysis confirmed that 1 When the resolution of H NMR spectroscopy is insufficient to identify and quantify all species, 13 C NMR analysis. The measurements were performed using a Brüker 500 MHz NMR spectrometer, with proton observation at a frequency of 500.43 MHz and carbon observation at a frequency of 125.83 MHz.

[0125] For insoluble elastomers with swelling ability in solvents, proton observation and carbon observation were performed using a 4 mm z-stage HRMAS probe in proton decoupled mode. Spectra were collected at a rotation speed of 4000 Hz to 5000 Hz.

[0126] For the measurements of soluble elastomers, a liquid NMR probe was used in proton decoupled mode for proton observation and carbon observation.

[0127] The preparation of insoluble samples is carried out in a rotor containing the material to be analyzed and a deuterated solvent capable of swelling, usually deuterated chloroform (CDCl3). The solvent used must always be a deuterated solvent and its chemical characteristics can be adjusted by a person skilled in the art. The amount of material used is adjusted to obtain a spectrum with sufficient sensitivity and resolution.

[0128] The soluble sample is dissolved in a deuterated solvent, usually deuterated chloroform (CDCl3) (about 25 mg of elastomer in 1 ml). The solvent or solvent blend used must always be a deuterated solvent and its chemical identity can be adjusted by a person skilled in the art.

[0129] In both cases (soluble sample or swollen sample):

[0130] Proton NMR uses a 30° single pulse sequence. Adjust the spectrum window to observe all resonance lines belonging to the molecule being analyzed. Adjust the number of accumulations to obtain a signal-to-noise ratio sufficient to quantify each unit. Adjust the cycle delay between each two pulses to obtain quantitative measurements.

[0131] For carbon NMR, a 30° single-pulse sequence was used, with proton decoupling only during acquisition to avoid the "nuclear Overhauser" effect (NOE) and maintain quantification. The spectral window was adjusted to observe all resonance lines belonging to the molecule being analyzed. The number of accumulations was adjusted to obtain a signal-to-noise ratio sufficient to quantify each unit. The recycle delay between successive pulses was adjusted to obtain quantitative measurements.

[0132] The NMR measurements were carried out at 25 °C.

[0133] Glass transition temperature:

[0134] The glass transition temperature Tg of the polymer was measured using a differential scanning calorimeter. The analysis was carried out in accordance with the requirements of standard ASTM D3418-08.

[0135] Mooney viscosity:

[0136] The Mooney viscosity was measured using an oscillating consistency meter as described in standard ASTM D1646 (1999). The measurement was carried out according to the following principle: A sample to be analyzed in the uncured state (i.e., before curing) was molded (formed) in a cylindrical chamber heated to a given temperature (100 °C). After preheating for 1 minute, the rotor rotated at 2 revolutions per minute within the test specimen, and after 4 minutes of rotation, the working torque required to maintain this motion was measured. The Mooney viscosity (ML) is expressed in "Mooney units" (MU, 1 MU = 0.83 Newton·meter).

[0137] Preparation of rubber compositions:

[0138] Two rubber compositions were prepared. These compositions were manufactured in the following manner:

[0139] The elastomer, then silica, a silane coupling agent, and various other ingredients except for the vulcanization system were introduced into a closed mixer (final fill level: approximately 70% by volume), the initial tank temperature of which was approximately 80 °C. Then, thermomechanical processing (non-production phase) was carried out in one step, which lasted approximately 5 to 6 minutes until a maximum "discharge" temperature of 160 °C was reached. The mixture thus obtained was recovered and cooled, and then sulfur and a sulfenamide accelerator were introduced into the mixer (homogenizing finisher) at 23 °C, and all substances were mixed for an appropriate time (e.g., between 5 and 12 minutes) (production phase).

[0140] Subsequently, the composition thus obtained is calendered in the form of a sheet (with a thickness ranging from 2 mm to 3 mm) or a thin rubber sheet (for measuring its physical or mechanical properties after vulcanization (cured state) at 150 °C), or in the form of a formed element that can be directly used, for example, as a semi-finished product for a tire after cutting and / or assembling into the required dimensions.

[0141] The formulation of the rubber composition (in phr) is described in Table 2.

[0142] The rubber compositions all contain a highly saturated diene elastomer, elastomer E1, a vulcanization system, and silica. Rubber composition T1 is a control composition because it contains the silane coupling agent TESPT, which is commonly used in diene rubber compositions reinforced with silica and intended for tires. Composition C1 (which contains the azosilane coupling agent corresponding to formula (1)) conforms to the present invention. The azosilane is a compound of the formula (EtO)3Si(CH2)3-NH-C(=O)-N=N-Ph, where the symbol Ph represents a phenyl group. It is prepared according to the procedure described in document WO2015162053A1.

[0143] The formulations of rubber compositions T1 and C1 (in phr) are described in Table 1. The total sulfur content of each rubber composition is the same, but it should be noted that in the case of rubber composition T1, the coupling agent "Si69" releases free sulfur during the reaction with the elastomer, which represents a source of sulfur available for vulcanization, i.e., 0.3 phr. The coupling agent is introduced into the rubber composition in the same content as the alkoxysilane functional group.

[0144] Elastomer E1 is a copolymer of ethylene and 1,3-butadiene, which is prepared according to the following procedure:

[0145] To a 70 L reactor containing methylcyclohexane (64 L), ethylene (5600 g) and 1,3-butadiene (2948 g), butyl octyl magnesium (BOMAG) and a catalyst system dissolved in methylcyclohexane were added. The Mg / Nd ratio was 6.2. The volume of the introduced catalyst system solution was 840 mL, and the Nd concentration of the catalyst system solution was 0.0065 M. The reaction temperature was adjusted to 80 °C and the polymerization started. The polymerization was carried out at a constant pressure of 8.3 bar. Throughout the polymerization, ethylene and 1,3-butadiene were fed to the reactor in a molar ratio of 73 / 27. The polymerization was stopped by cooling, degassing of the reactor and addition of ethanol. An antioxidant was added to the polymer solution. After steam stripping and drying to a constant mass, the copolymer was recovered. The polymerization time was 225 minutes. The weighed mass (6.206 kg) was able to determine the average catalytic activity of the catalyst system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol·h). The ML value of the copolymer was equal to 62.

[0146] The catalyst system is a preformed catalyst system. It was prepared in methylcyclohexane from 0.0065 mol / L of metallocene [Me2SiFlu2Nd(μ-BH4)2Li(THF)], the cocatalyst butyl octyl magnesium (BOMAG) (the BOMAG / Nd molar ratio was equal to 2.2), and the preformed monomer 1,3-butadiene (the 1,3-butadiene / Nd molar ratio was equal to 90). The medium was heated at 80 °C for 5 hours. It was prepared according to the preparation method in paragraph II.1 of patent application WO 2017 / 093654 A1.

[0147] Table 2 gives the results of the properties of the rubber composition after curing. Compared with composition T1, composition C1 has higher stiffness and the hysteresis does not increase; on the contrary, the hysteresis even decreases significantly.

[0148] Table 1

[0149] Composition (phr) T1 C1 EBR(1) 100 100 Silica(2) 38 38 Si69 coupling agent(3) 3.1 Azosilane coupling agent(4) 4.3 Ozone wax(5) 1 1 Antioxidant(6) 2 2 Stearic acid(7) 2 2 ZnO(8) 2.4 2.4 Sulfur 1 1.3 CBS(9) 1 1

[0150] (1) Copolymer of ethylene and 1,3-butadiene, which contains 73.8 mol% of ethylene, 11.9 mol% of 1,2-butadiene units, 6.7 mol% of 1,4-butadiene units and 7.6 mol% of 1,2-cyclohexane rings, with an ML of 62

[0151] (2) Zeosil 1165MP in the form of microbeads obtained from Solvay-Rhodia

[0152] (3) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, Si69 obtained from Evonik

[0153] (4) Azosilane (EtO)3Si(CH2)3-NH-C(=O)-N=N-Ph

[0154] (5) Anti-ozone wax, Varazon 4959 obtained from Sasol Wax

[0155] (6) N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, Santoflex 6PPD obtained from Flexys

[0156] (7) Stearic acid, Pristerene 4931 obtained from Uniqema

[0157] (8) Industrial grade zinc oxide obtained from Umicore

[0158] (9) N-cyclohexyl-2-benzothiazolesulfenamide, Santocure CBS Table 2 obtained from Flexsys

[0159] Composition T1 C1 ΔG 23 °C 100 65 Tanδmax return 23 °C 100 75 G*60℃ 100 127

Claims

1. A rubber composition, the rubber composition comprising: - A highly saturated diene elastomer, the highly saturated diene elastomer being a copolymer of ethylene and a 1,3-diene, the copolymer comprising more than 50 mol% of ethylene units based on the monomer units of the copolymer; - A vulcanization system, - A reinforcing filler, the reinforcing filler comprising silica, - And a silane coupling agent of formula (1) (G1) 3-a (G2) a Si-Z-NH-C(O)-N=N-G4(1) Wherein: - G1 are the same or different and each represents a C1-C8 alkyl group, - G2 are the same or different and each represents a hydroxyl group or a C1-C8 alkoxy group, - G4 represents an aromatic group, - Z represents a C1-C8 alkanediyl group, - a is equal to 1, 2 or 3.

2. The rubber composition according to claim 1, wherein, The 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes in which one is 1,3-butadiene, preferably 1,3-butadiene.

3. The rubber composition according to any one of claims 1 and 2, wherein The ethylene units in the highly saturated diene elastomer account for at least 60 mol%, preferably at least 65 mol%, of all the monomer units of the highly saturated diene elastomer.

4. The rubber composition according to any one of claims 1 to 3, wherein, The ethylene units in the highly saturated diene elastomer account for no more than 90 mol%, preferably no more than 85 mol%, of all the monomer units of the highly saturated diene elastomer.

5. The rubber composition according to any one of claims 1 to 4, wherein, The ethylene units in the highly saturated diene elastomer account for no more than 80 mol% of all the monomer units of the highly saturated diene elastomer.

6. The rubber composition according to any one of claims 1 to 5, wherein, The highly saturated diene elastomer is a statistical copolymer.

7. The rubber composition according to any one of claims 1 to 6, wherein, The silica accounts for more than 50% by mass, preferably more than 85% by mass, of the reinforcing filler.

8. The rubber composition according to any one of claims 1 to 7, wherein, G2 are the same or different and each represents a C1-C4 alkoxy group.

9. The rubber composition according to any one of claims 1 to 8, wherein, G2 are the same or different and each represents a methoxy group or an ethoxy group.

10. The rubber composition according to any one of claims 1 to 9, wherein, G1 are the same or different and each represents a methyl group or an ethyl group.

11. The rubber composition according to any one of claims 1 to 10, wherein, G4 represents a phenyl group or a tolyl group.

12. The rubber composition according to any one of claims 1 to 11, wherein, Z represents a C1-C4 alkanediyl group.

13. The rubber composition according to any one of claims 1 to 12, wherein, Z represents a 1,3-propanediyl group.

14. The rubber composition according to any one of claims 1 to 13, wherein, a is equal to 3.

15. A tire, the tire comprising the rubber composition as defined in any one of claims 1 to 14, preferably in its tread.

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