Rubber composition

Abstract

A rubber composition is provided that comprises a highly saturated diene elastomer that is a copolymer of ethylene and a 1,3-diene that comprises ethylene units that represent more than 50 mol% of the monomer units of the copolymer, a vulcanization system, a reinforcing filler that contains a silica, and an organofunctional silane coupling agent having at least one blocked thiol function, at least one thiol function, and at least one function that is a hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group. Such a composition exhibits improved cured fracture properties.

Description

Title of the invention: Rubber composition

[0001] The field of the present invention is that of rubber compositions which comprise a silica and a highly saturated diene elastomer and which are in particular intended to be used in the manufacture of tires.

[0002] Silica-reinforced rubber compositions comprising a highly saturated diene elastomer are known from WO 2014114607 A1 and WO 2018224776 A1. The highly saturated diene elastomer is a copolymer of ethylene and a 1,3-diene such as 1,3-butadiene and has the characteristic of containing more than 50 mol% of ethylene unit. Due to its high ethylene content and low diene unit content of less than 50 mol%, it is largely distinguished from diene elastomers which are traditionally used in rubber compositions and which generally contain more than 50 mol% of diene unit, such as polybutadienes, polyisoprenes and copolymers of 1,3-butadiene or isoprene and styrene. In particular, it has the particularity of giving a rubber composition a different compromise of properties between rigidity and hysteresis.

[0003] There remains a need to further improve the cured fracture properties of such rubber compositions.

[0004] The inventors have discovered a novel rubber composition which has further improved as-cured breaking properties such as elongation at break and breaking stress.

[0005] Thus, the invention relates to a rubber composition which comprises: - a highly saturated diene elastomer which is a copolymer of ethylene and a 1,3-diene which comprises ethylene units which represent more than 50 mol% of the monomer units of the copolymer, - a vulcanization system, - a reinforcing filler which contains a silica, - and an organofunctional silane coupling agent having at least one blocked thiol function, at least one thiol function and at least one function which is a hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group and corresponding to the formula (1) (A)p(B)q(l) in which A and B respectively represent a blocked mercaptosilane unit corresponding to formula (2) and a mercaptosilane unit corresponding to formula (3) p (2) f"' QQ yb 2 V-* * O """"x ^4 Ol Z- y O xu 2% I 4 f^i 3 *i5' h ri O tx^ 'ww o 1 —— v W Xu in which R3 is selected from a hydrogen atom, a linear or branched C1-C18 alkyl, a linear or branched C2-C18 alkenyl, each R4 is independently selected from linear or branched C1-C6 saturated divalent hydrocarbon groups, each Zb which forms a bridging structure between a silicon atom of a unit and a silicon atom of another unit, these units being able to be identical or different, is independently selected from (-O-)0.5 and [-O(R°CR0)fO-]oJ5 with the symbols R°, identical or different, each representing a hydrogen atom or a C1-C3 alkyl and f being a number in a range from 2 to 15, each Zc which forms a cyclic structure with the silicon atom of a unit is a group of formula [-O(R°CR0)fO-]oJ5 with R° and f as defined above, each X is independently selected from a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group,a C1-C6 alkoxyl group and a group of formula HO(R0CR°)fO- with R° and f as defined previously, with u+v+2w=3, u being a number equal to 0, 1, 2 or 3, v being a number equal to 1, 2 or 3 and w being a number equal to 0 or 1, p is a number in a range from 1 to 20, q is a number in a range from 1 to 20.

[0006] The invention also relates to a tire which comprises a rubber composition in accordance with the invention, preferably in its tread. Detailed description

[0007] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​greater than "a" and less than "b" (i.e., excluding the limits a and b) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0008] The abbreviation "pce" means parts by weight per hundred parts of elastomer (of the total elastomers if several elastomers are present).

[0009] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. In the same way, the compounds mentioned may also come from the recycling of materials already used, that is to say they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0010] In the present invention, the term "tyre" means a pneumatic or non-pneumatic bandage. A pneumatic bandage usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic bandage, for its part, usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement, ensuring the connection with a tread and a deformable structure, such as spokes, ribs or cells, this structure being arranged between the base and the crown. Such non-pneumatic bandages do not necessarily comprise a sidewall. Non-pneumatic bandages are described for example in documents WO 03 / 018332 and FR2898077.According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic bandage.

[0011] Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a copolymer such as the copolymer useful in the invention are expressed as a molar percentage relative to the total of the monomer units of the copolymer.

[0012] The elastomer useful for the purposes of the invention is a highly saturated diene elastomer, preferably random, which comprises ethylene units resulting from the polymerization of ethylene. In a known manner, the expression "ethylene unit" refers to the -(CH2-CH2)- unit resulting from the insertion of ethylene into the elastomer chain. The highly saturated diene elastomer is rich in ethylene units, since the ethylene units represent more than 50% by mole of all the monomer units of the elastomer.

[0013] Preferably, the highly saturated diene elastomer comprises at least 60 mol% of ethylene unit, preferably at least 65 mol% of ethylene unit, more preferably at least 70 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 of the monomer units of the highly saturated diene elastomer. Even more preferably, the ethylene units represent at least 70 mol% of all of the monomer units of the highly saturated diene elastomer.

[0014] Preferably, the ethylene units in the highly saturated diene elastomer represent at most 90 mol% of all the monomer units of the highly saturated diene elastomer. More preferably, the ethylene units represent at most 85 mol% of all the monomer units of the highly saturated diene elastomer. Even more preferably, the ethylene units represent at most 80 mol% of all the monomer units of the highly saturated diene elastomer.

[0015] According to an advantageous embodiment, the highly saturated diene elastomer comprises from 60% to 90 mol% of ethylene unit, particularly from 60% to 85 mol% of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer. More advantageously, the highly saturated diene elastomer comprises from 60% to 80 mol% of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0016] According to another advantageous embodiment, the highly saturated diene elastomer comprises from 65% to 90 mol% of ethylene unit, particularly from 65% to 85 mol% of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer. More advantageously, the highly saturated diene elastomer comprises from 65% to 80 mol% of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0017] According to yet another advantageous embodiment of the invention, the highly saturated diene elastomer comprises from 70% to 90% mol of ethylene unit, particularly from 70% to 85% mol of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer. More advantageously, the highly saturated diene elastomer comprises from 70% to 80% mol of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0018] The highly saturated diene elastomer being a copolymer of ethylene and a 1,3-diene also comprises 1,3-diene units resulting from the polymerization of a 1,3-diene. In a known manner, the expression "1,3-diene unit" refers to the units resulting from the insertion of the 1,3-diene by a 1,4-addition, a 1,2-addition or a 3,4-addition in the case of isoprene for example. The 1,3-diene units are those for example of a 1,3-diene having 4 to 12 carbon atoms, such as 1,3-butadiene, isoprene, 1,3-pentadiene, an aryl-1,3-butadiene. Preferably, the 1,3-diene is the 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 random.

[0019] The highly saturated diene elastomer can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the highly saturated diene elastomer. Generally, it can be prepared by copolymerization of at least one 1,3-diene, preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. In this respect, mention may be made of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant.The highly saturated diene elastomer, including when it is random, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1. Advantageously, the diene elastomer is random and is preferably prepared according to a semi-continuous or continuous process such as described in documents WO 2017103543 A1, WO 201713544 A1, WO 2018193193 and WO 2018193194. The highly saturated diene elastomer can carry functional groups comprising one or more heteroatoms such as nitrogen, oxygen, silicon, halogen.The functional groups may be introduced into the highly saturated diene elastomer during its synthesis or after its synthesis, as is for example described in document WO 2017097931 AL According to any of the embodiments of the invention, the highly saturated diene elastomer is preferably a hydrocarbon polymer, i.e. consisting solely of hydrogen atoms and carbon atoms.

[0020] The highly saturated diene elastomer preferably contains units of formula (I) or units of formula (II). -CH2-CH(CH=CHz)- (0)

[0021] The presence of 6-membered saturated cyclic unit, 1,2-cyclohexanediyl, of formula (I) in the copolymer may result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. When the highly saturated diene elastomer comprises units of formula (I) or units of formula (II), the molar percentages of the units of formula (I) and the units of formula (II) in the highly saturated diene elastomer, respectively o and p, preferably satisfy the following equation (eq. 1) or equation (eq. 2), o and p being calculated on the basis of all the monomer units of the highly saturated diene elastomer. 0 < o+p < 30 (eq. 1) 0 < o+p < 25 (eq. 2)

[0022] Preferably, the highly saturated diene elastomer comprises units of formula (I) in a molar ratio greater than 0% and less than 15%, more preferably less than 10% mol, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0023] The rubber composition may contain, in addition to the highly saturated diene elastomer, a second diene elastomer. A diene elastomer is understood to mean an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). The diene monomer units are called diene units. The second elastomer may be chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes, polyisoprenes, butadiene copolymers, isoprene copolymers and their mixture. A highly unsaturated elastomer is an elastomer which contains more than 50 mol% of diene units.

[0024] Preferably, the level of the highly saturated diene elastomer in the rubber composition is at least 50 parts by weight per hundred parts of elastomer of the rubber composition (phr). More preferably, the level of the highly saturated diene elastomer in the rubber composition varies in a range from 80 to 100 phr. Even more preferably, it varies in a range from 90 to 100 phr. It is advantageously 100 phr. The highly saturated diene elastomer may be a single highly saturated diene elastomer or a mixture of several highly saturated diene elastomers which differ from each other by their microstructures or by their macrostructures.In the case where the rubber composition contains several highly saturated diene elastomers which differ from each other by their microstructures or by their macrostructures, the level of the highly saturated diene elastomer in the rubber composition relates to the mixture of highly saturated diene elastomers.

[0025] The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CT AB specific surface area both less than 450 m2 / g, preferably within a range from 30 to 400 m2 / g, in particular from 60 to 300 m2 / g. In this presentation, 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" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the standard NF ISO 5794-1, Annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / po: 0.05 to 0.17]. The CT AB specific surface area values ​​were determined according to the standard NF ISO 5794-1, Annex G of June 2010.The process is based on the adsorption of CT AB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the “external” surface of the reinforcing filler.

[0026] Any type of precipitated silica may be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples that may be mentioned are the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ® 5000GR”, “Ultrasil ® 7000GR” from the company Evonik, the silicas “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” from Evonik, silica “Zeosil® 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0027] The reinforcing filler may comprise any type of so-called reinforcing filler other than silica, known for its ability to reinforce a rubber composition usable in particular for the manufacture of tires, for example a carbon black. Suitable carbon blacks include all carbon blacks, in particular the blacks conventionally used in tires or their treads. Among the latter, mention will be made more particularly of reinforcing carbon blacks of the 100, 200, 300 series, or blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772. These carbon blacks can be used in their isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. When carbon black carbon is used in the rubber composition, it is preferably used at a rate less than or equal to 10 phr (for example, the carbon black rate can be in a range from 1 to 10 phr). Advantageously, the carbon black rate in the rubber composition is less than or equal to 5 phr. In the indicated ranges, the coloring (black pigmenting agent) and anti-UV properties of carbon blacks are benefited from, without otherwise penalizing the typical performance provided by silica.

[0028] The silica preferably represents more than 50% by mass of the reinforcing filler. In other words, the proportion of silica in the reinforcing filler is greater than 50% by weight of the total weight of the reinforcing filler. More preferably, the silica represents more than 85% by mass of the reinforcing filler.

[0029] The total rate of reinforcing filler may vary over a wide range, for example from 30 phr to 150 phr. According to a first embodiment, the total rate of reinforcing filler varies over a range from 30 phr to 60 phr. According to a second embodiment, the total rate of reinforcing filler varies over a range from more than 60 phr to 150 phr. The first embodiment is preferred over the second embodiment for use of the rubber composition in a tread having very low rolling resistance. Any of these ranges of total rate of reinforcing filler may be applicable to any of the embodiments of the invention.

[0030] To couple the silica to the diene elastomer to the highly saturated diene elastomer, a coupling agent (or bonding agent) is used, a silane, at least bifunctional intended to ensure a sufficient connection, of a chemical and / or physical nature, between the silica and the diene elastomer. The rubber composition according to the invention comprises, as coupling agent, an organofunctional silane having at least one blocked mercaptosilane unit, at least one mercaptosilane unit and at least one function which is a hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group. The organofunctional silane corresponds to the following formula (1): (A)p(B)q(l) in which - A is a symbol representing a blocked mercaptosilane unit corresponding to the formula (2) I* . R 3---C---S---R4—S i--Z3, He I ox ü < 2 )

[0031] - B is a symbol representing a mercaptosilane unit corresponding to the formula (3) Zc I w Mcyn .or 37h no 1x4 01 v

[0032] In formula (2), R3 is chosen from a hydrogen atom, a linear or branched C1-C18 alkyl, a linear or branched C2-C18 alkenyl, In formulae (2) and (3), each R4 is independently selected from linear or branched C1-C6 saturated divalent hydrocarbon groups, each Zb which forms a bridging structure between a silicon atom of one unit and a silicon atom of another unit, these units being able to be identical or different, is independently selected from (-O-)0.5 and [-O(R°CR°)fO-]o.5 with the symbols R°, identical or different, each representing a hydrogen atom or a C1-C3 alkyl and f being a number in a range from 2 to 15, each Zc which forms a cyclic structure with the silicon atom of a unit is a group of formula [-O(R °CR°)fO-]o.5 with R° and f as defined above, each X is independently selected from a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group, a group C1-C6 alkoxyl and a group of formula HO(R°CR°)fO- with R° and f as defined previously, with u+v+2w=3, u being a number equal to 0, 1, 2 or 3,v being a number equal to 1, 2 or 3 and w being a number equal to 0 or 1. ,

[0033] p is a number in the range from 1 to 20, q is a number in the range from 1 to 20.

[0034] For the purposes of the present invention, the term "organofunctional silane" means a silane or a mixture of silanes having the characteristic of possessing at least one blocked, i.e. protected, thiol function, one thiol function, i.e. unprotected, and at least one function which is a hydroxylalkoxysilyl group or a cyclic dialkoxysilyl group.

[0035] By “mercaptosilane unit” is meant a unit which contains at least one silicon atom and a thiol function (-SH) linked to a carbon atom.

[0036] By "blocked mercaptosilane unit" is meant a unit which contains at least one silicon atom and at least one blocked thiol function. A blocked thiol function can for example be a thioester group -S-(CO) R.

[0037] In the compound of formula (1), the sequence of the blocked mercaptosilane repeating units (A) and the mercaptosilane repeating units (B) is indifferent. In particular, this sequence can be alternating (for example ABABAB), block (for example AAABBB) or statistical, that is to say that the sequential distribution of said units (A) and (B) obeys known statistical laws.

[0038] By hydroxyalkoxy group used in the name hydroxyalkoxysilyl, we mean a monovalent group of formula HO(R°CR°)fO- which substitutes the silicon atom, R° and f being as defined previously.

[0039] By cyclic dialkoxysilyl group is meant a group in which a silicon atom is linked to two oxygen atoms each linked to a separate carbon atom of the same alkylene group.

[0040] By “bridging structure” is meant a chemical structure made of covalent bond(s) allowing two repeating units to be linked together, these repeating units being able to be identical or different.

[0041] The Cn-Cm denomination qualifying a group refers to the number of carbon atoms constituting the group which contains n to m carbon atoms, n and m being whole numbers with m greater than n.

[0042] Preferably, R3 in formula (2) is selected from hydrogen, C1-C10 alkyls and C2-C10 alkenyls. More preferably, R3 in formula (2) is a linear C6-C8 alkyl. Even more preferably, the symbol R3 in formula (2) is heptyl (C7Hi5-).

[0043] Preferably, each R4 in formulas (2) and (3) is independently a linear C1-C4 alkylene. More preferably, each R4 is propylene.

[0044] Preferably, each Zb in formulas (2) and (3) is independently selected from the group consisting of the units of formula (-O-)0.5, [A3CH2CH2CH20-]oj5, [-OCH2CH2CH2CH20-]o.5 and [-OCH2CH(CH3)CH2O-]oj5. More preferably, Zb in formulas (2) and (3) is of formula (-O-)0.5 or of formula [-OCH2CH(CH3)CH2 0-]o.5-

[0045] Preferably, each Zc in formulas (2) and (3) is independently selected from the group consisting of the units of formula [-OCH2CH2CH2O-]0>5, [-OCH2CH2 CH2CH20-]0.5 and [-OCH2CH(CH3)CH20-]0.5. More preferably, each Zc in formulas (2) and (3) is of formula [-OCH2CH(CH3)CH2O-]0>5.

[0046] Preferably, each X in formulas (2) and (3) is independently selected from the group consisting of hydroxyl, methoxy, ethoxy, methyl, ethyl, 3-hydroxypropoxy, 3-hydroxy-2-methylpropoxy and 4-hydroxybut-1-oxy. More preferably, each X in formulas (2) and (3) is identical and is selected from the group consisting of hydroxyl, methoxy, ethoxy and 3-hydroxy-2-methylpropoxy.

[0047] Very advantageously, in formulas (2) and (3), R3 is heptyl (C7Hi5-), each R4 is propylene, each Zb is of formula (-O-)0.5 or l-OCHoCHlCHdCFTO-lo^ each Zc is of formula [-OCH2CH(CH3)CH20-]o.5, each X is selected from the group consisting of hydroxyl, methoxy, ethoxy and 3-hydroxy-2-methylpropoxy, with u+v+2w=3, u being 0, 1, 2 or 3, v being 1, 2 or 3 and w being 0 or 1.

[0048] The notations (-O-)0.5 and [-O(R0CR°)fO-]o.5 refer to half of a siloxane bond and half of a bridging dialkoxy group respectively. These notations are used in conjunction with a silicon atom of the repeating units of the oligomer. They denote half of an oxygen atom, namely half of the oxygen atom which is bonded to the silicon atom of a repeating unit or half of a dialkoxy group, namely half of the atom of the dialkoxy group which is bonded to the silicon atom of a repeating unit; it being understood that the other half of the oxygen atom or the dialkoxy group respectively is bonded to another silicon atom of another repeating unit of the structure of the oligomer; the repeating units may be the same or different. Thus, (-O-)0.5 forms a siloxane bond between two silicon atoms each belonging to a repeating unit.[-O(R°CR°)fO-]o,5can form either a bridging structure (this intermolecular structure being represented by Zb) between two silicon atoms each belonging to a repeating unit, or a cyclic structure (this intramolecular structure being represented by Zc), the two oxygen atoms of [-O(R°CR°)fO-]o,5 being linked to the silicon atom of the unit. A person skilled in the art will understand that in the compound of formula (1), the bridging structures can be identical or different between the repeating units. For example, the bridging structures can be of the -Si-O(R°CR°)fO-Si- type or a mixture of bridging structures of the -Si-O(R°CR°)fO-Si- type and of the -Si-O-Si- type.

[0049] Preferably, the organofunctional silane has a molar percentage of blocked mercaptosilane units (A) ranging from 20 to 80% and a molar percentage of mercaptosilane units (B) ranging from 80 to 20%. More preferably, the organofunctional silane has a molar percentage of blocked mercaptosilane units (A) ranging from 40 to 60% and a molar percentage of mercaptosilane units (B) ranging from 60 to 40%. Even more preferably, the organofunctional silane has a molar percentage of blocked mercaptosilane units ranging from 50 to 55% and a molar percentage of mercaptosilane units ranging from 50 to 45%.The molar percentage of blocked mercaptosilane units and that of mercaptosilane units of the organofunctional silane are calculated relative to the total number of thiol units, whether blocked or not, in the organofunctional silane and they can be determined by any method well known to those skilled in the art, such as for example 'H NMR analysis.

[0050] The coupling agent, the organofunctional silane, can be obtained from a synthesis process comprising at least one step (a) of transesterification reaction of a diol compound of formula (4) with at least one blocked mercaptosilane compound of formula (5) and with at least one mercaptosilane compound of formula (6): HO(R°CR°)fOH (4) (RO)3SiR4SC(=O)R3 (5) (RO)3SiR4SH (6) R° and f being as defined previously, namely R°, identical or different, representing a hydrogen atom, a methyl, an ethyl or a propyl and f a number within a range from 2 to 15, R, identical or different, representing a linear C1-C6 alkyl group, R3 and R4 being as defined previously, namely R4 representing a linear or branched C1-C6 saturated divalent hydrocarbon group, R3 representing a hydrogen atom, a linear or branched C1-C18 alkyl, or a linear or branched C2-C18 alkenyl.

[0051] The transesterification reaction is a reaction well known to those skilled in the art and can be carried out in the presence of a transesterification catalyst, such as, for example, strong acids.

[0052] Preferably, in the process described above, the diol compound of formula (4) is chosen from HOCH2CH2CH2OH, HOCH2CH2CH2CH2OH and HOCH2CH(CH3)CH2 OH. More preferably, in the process described above, the diol compound of formula (4) is HOCH2CH(CH3)CH2OH.

[0053] Preferably, the compounds of formula (5) and (6) used in the implementation of the process described above are those in which the group R is chosen from methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl

[0054] Preferably, the compounds of formula (5) used in the implementation of the process described above are those in which R3 represents a hydrogen atom, a linear or branched C1-C10 alkyl, or a linear or branched C2-C10 alkenyl. More preferably, the compounds of formula (5) used in the implementation of the process described above are those in which R3 is a linear C6-C8 alkyl. Even more preferably, the compounds of formula (5) used in the implementation of the process described above are those in which R3 is heptyl (C7Hi5-).

[0055] Preferably, the compounds of formula (5) and (6) used in carrying out the process described above are those in which each R4 is independently a divalent hydrocarbon group chosen from the group consisting of linear C 1 -C 4 alkylenes. More preferably, the compounds of formula (5) and (6) used in carrying out the process described above are those in which each R4 is propylene.

[0056] Preferably, the compounds of formula (5) and (6) used in the implementation of the process described above are those in which R3 is heptyl, R4 is propylene, R, identical or different (preferably identical), is chosen from methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl and the compound of formula (4) used in the implementation of the process described above is HOCH2CH(CH3)CH2OH.

[0057] Mixtures of compounds of formula (5) and mixtures of compounds of formula (6) can be used to synthesize the coupling agent, the organofunctional silane.

[0058] The method for synthesizing the coupling agent may further comprise: - at least one treatment step (b) of the products obtained in step (a) to convert part of the blocked thiol functions, if present in the products obtained in step (a), into thiol functions (-SH) and / or - at least one treatment step (c) of the products obtained in step (a) to convert part of the thiol functions, if present in the products obtained in step (a), into blocked thiol functions and / or - at least one step (d) of partial hydrolysis of the products obtained in step (a), of the products obtained in step (b) if this step is implemented in the process and of the products obtained in step (c) if this step is implemented in the process.

[0059] Treatment step (b) may, for example, be a step during which a strong base, for example, NaOEt, is used to convert the blocked thiol functions carried by the products obtained in step (a) into thiol functions. Treatment step (c) may, for example, be a step of esterification of the thiol functions of the products obtained in step (a) using a carboxylic acid (in particular C7Hi5COOH) or an acyl chloride (in particular C7Hi5COC1) to convert them into blocked thiol functions. Partial hydrolysis step (d) may take place when there is an excess of water compared to the products and reagents used during steps (a), and optionally steps (b) and (c) if present. The partial hydrolysis step makes it possible to obtain the compounds described above in which Zb represents (-6)-)0.5 or OH.

[0060] Those skilled in the art may refer in particular to document WO2007 / 098120 A2 which describes the process for obtaining the organofunctional silane coupling agent.

[0061] The organofunctional coupling agent may be obtained in the form of a mixture resulting from the implementation of the process described above and may be used in the rubber composition according to the invention in the form of this mixture. The mixture contains not only the organofunctional coupling agent, but also other silanes chosen from any one of the following compounds and mixtures thereof: - a compound of formula (2') which is derived from formula (2), formula (2') differs denying formula (2) in that Zbv is replaced by Zat, Za having the same definition as group X of formula (2), t being a number equal to 0, 1, 2 or 3 with u+t+2w= 3 and u and w having the same definition as in formula (2), - a compound of formula (3') which is derived from formula (3), formula (3') differing from formula (3) in that Zbv is replaced by Zat, Za having the same definition as group X of formula (3), t being a number equal to 0, 1, 2 or 3 with u+t+2w= 3 and u and w having the same definition as in formula (3), - a dimer consisting of two blocked mercaptosilane units of formula (2), - a dimer consisting of two mercaptosilane units of formula (3), - a dimer consisting of a blocked mercaptosilane unit (2) and of a mercaptosilane unit of formula (3) - an oligomer consisting of blocked mercaptosilane units of formula (2), - an oligomer consisting of mercaptosilane units of formula (3).

[0062] The organofunctional silane coupling agent is for example commercially available from Momentive. Inc under the trade name “NXT-Z”, in particular “NXT-Z45”.

[0063] In the rubber composition according to the invention, the level of the organofunctional silane coupling agent is adjusted by a person skilled in the art according to the specific surface area of ​​the silica used in the rubber composition and according to the level of silica in the rubber composition. It preferably varies from 1 to 15 phr, more preferably from 1.5 to 10 phr, even more preferably from 2 to 5 phr.

[0064] The rubber composition according to the invention has the further essential characteristic of containing a vulcanization system, i.e. a sulfur-based crosslinking system. The sulfur is typically provided in the form of molecular sulfur or a sulfur-donating agent, preferably in molecular form. Sulfur in molecular form is also referred to as molecular sulfur. The term “sulfur donor” means any compound which releases sulfur atoms, combined or not in the form of a polysulfide chain, capable of being inserted into the polysulfide chains formed during vulcanization and bridging the elastomer chains. In addition to the vulcanization system, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine), etc. are incorporated during the first non-productive phase and / or during the productive phase.The sulfur content is preferably between 0.5 and 4 pce, that of the primary accelerator is preferably between 0.5 and 5 pce. These preferential rates can apply to any of the embodiments of the invention.

[0065] Any compound capable of acting as an accelerator for the vulcanization of elastomers can be used as a vulcanization accelerator (primary or secondary). diene compounds in the presence of sulfur, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide type for primary accelerators, of the thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type for secondary accelerators. Examples of primary accelerators include, in particular, sulfenamide compounds such as N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), and mixtures of these compounds. The primary accelerator is preferably a sulfenamide, more preferably N-cyclohexyl-2-benzothiazyl sulfenamide.Examples of secondary accelerators include thiuram disulfides such as tetraethylthiuram disulfide, tetrabutylthiuram disulfide ("TBTD"), tetrabenzylthiuram disulfide ("TBZTD") and mixtures of these compounds. The secondary accelerator is preferably a thiuram disulfide, more preferably tetrabenzylthiuram disulfide.

[0066] The 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 and 90 min depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition considered.

[0067] The rubber composition in accordance with the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, in particular pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, plasticizers such as plasticizing oils or resins.

[0068] The rubber composition, before vulcanization, can be manufactured in suitable mixers, using two successive preparation phases according to a procedure well known to those skilled in the art: a first thermo-mechanical working or kneading phase (sometimes referred to as a "non-productive" phase) at high temperature, up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second mechanical working phase (sometimes referred to as a "productive" phase) at a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the sulfur or sulfur donor and the vulcanization accelerator are incorporated.

[0069] For example, the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary constituents, any possible additional implementation and other various additives, with the exception of the vulcanization system. The total mixing time, in this non-productive phase, is preferably between 1 and 15 min. After cooling the mixture thus obtained during the first non-productive phase, the low-temperature vulcanization system is then incorporated, generally in an external mixer such as a roller mixer, the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

[0070] The rubber composition may be calendered or extruded in the form of a sheet or plate, in particular for laboratory characterization, or in the form of a semi-finished (or profiled) rubber usable in a tire. The composition may be either in the raw state (before crosslinking or vulcanization), or in the cured state (before crosslinking or after vulcanization). It may constitute all or part of a semi-finished article, in particular intended to be used in a pneumatic or non-pneumatic tire which comprises a tread, in particular in the tread of the tire.

[0071] In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 35:

[0072] Mode 1: Rubber composition which comprises: - a highly saturated diene elastomer which is a copolymer of ethylene and a 1,3-diene which comprises ethylene units which represent more than 50 mol% of the monomer units of the copolymer, - a vulcanization system, - a reinforcing filler which contains silica, - and an organofunctional silane coupling agent having at least one blocked thiol function, at least one thiol function and at least one function which is a hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group and corresponding to the formula (1) (A)p(B)q(l) in which A and B respectively represent a blocked mercaptosilane unit corresponding to formula (2) and a mercaptosilane unit corresponding to formula (3) R3--C--S--R4—Si---Zbv He I (2> O Xu yC HS---R4—Si----Zbv , , Xu in which R3 is selected from a hydrogen atom, a linear or branched C1-C18 alkyl, a linear or branched C2-C18 alkenyl, each R4 is independently selected from linear or branched C1-C6 saturated divalent hydrocarbon groups, each Zb which forms a bridging structure between a silicon atom of one unit and a silicon atom of another unit, these units being able to be identical or different, is independently selected from (-O-)0.5 and [-O(R°CR°)fO-]o.5 with the symbols R°, identical or different, each representing a hydrogen atom or a C1-C3 alkyl and f being a number in a range from 2 to 15, each Zc which forms a cyclic structure with the silicon atom of a unit is a group of formula [-O(R°CR°)fO-]o.5 with R° and f as defined above, each X is independently selected from a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group,a C1-C6 alkoxyl group and a group of formula HO(R0CR°)fO- with R° and f as defined previously, with u+v+2w=3, u being a number equal to 0, 1, 2 or 3, v being a number equal to 1, 2 or 3 and w being a number equal to 0 or 1, p is a number in a range from 1 to 20, q is a number in a range from 1 to 20.

[0073] Mode 2: Rubber composition according to mode 1 in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes, one of which is 1,3-butadiene.

[0074] Mode 3: Rubber composition according to mode 1 or 2 in which the 1,3-diene is 1,3-butadiene.

[0075] Mode 4: Rubber composition according to any one of modes 1 to 3 in which the ethylene units in the highly saturated diene elastomer represent at least 60 mol% of all the monomer units of the highly saturated diene elastomer.

[0076] Mode 5: Rubber composition according to any one of modes 1 to 4 in which the ethylene units in the highly saturated diene elastomer represent at least 65 mol% of all the monomer units of the highly saturated diene elastomer.

[0077] Mode 6: Rubber composition according to any one of modes 1 to 5 in which the ethylene units in the highly saturated diene elastomer represent at least 70 mol% of all the monomer units of the highly saturated diene elastomer.

[0078] Mode 7: Rubber composition according to any one of modes 1 to 6 in which the ethylene units in the highly saturated diene elastomer represent at most 90 mol% of all the monomer units of the highly saturated diene elastomer.

[0079] Mode 8: Rubber composition according to any one of modes 1 to 7 in which the ethylene units in the highly saturated diene elastomer represent at most 85 mol% of all the monomer units of the highly saturated diene elastomer.

[0080] Mode 9: Rubber composition according to any one of modes 1 to 8 in which the ethylene units in the highly saturated diene elastomer represent at most 80 mol% of all the monomer units of the highly saturated diene elastomer.

[0081] Mode 10: Rubber composition according to any one of modes 1 to 9 in which the highly saturated diene elastomer contains units of formula (I) or units of formula (II). -CHz-CH(CH=CH2)- (H)

[0082] Mode 11: Rubber composition according to any one of modes 1 to 10 in which the highly saturated diene elastomer comprises units of formula (I) in a molar ratio greater than 0% and less than 15%, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0083] Mode 12: Rubber composition according to any one of modes 1 to 11 in which the highly saturated diene elastomer comprises units of formula (I) in a molar ratio greater than 0% and less than 10% mol, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0084] Mode 13: Rubber composition according to any one of modes 1 to 12 in which the highly saturated diene elastomer is a random copolymer.

[0085] Mode 14: Rubber composition according to any one of modes 1 to 13 in which the level of the highly saturated diene elastomer is at least 50 parts by weight per hundred parts of elastomer of the rubber composition (pce).

[0086] Mode 15: Rubber composition according to any one of modes 1 to 14 in which the rate of highly saturated diene elastomer varies in a range from 80 to 100 pce.

[0087] Mode 16: Rubber composition according to any one of modes 1 to 15 in which the total rate of reinforcing filler varies in a range from 30 to 150 pce.

[0088] Mode 17: Rubber composition according to any one of modes 1 to 16 in which the total rate of reinforcing filler varies in a range from 30 pce to 60 pce.

[0089] Mode 18: Rubber composition according to any one of modes 1 to 17 in which the silica represents more than 50% by mass of the reinforcing filler.

[0090] Mode 19: Rubber composition according to any one of modes 1 to 18 in which the silica represents more than 85% by mass of the reinforcing filler.

[0091] Mode 20: Rubber composition according to any one of modes 1 to 19 in which R3 in formula (2) is selected from hydrogen, C1-C10 alkyls and C2-C10 alkenyls.

[0092] Mode 21: Rubber composition according to any one of modes 1 to 20 in which R3 in formula (2) is a linear C6-C8 alkyl, more preferably is heptyl.

[0093] Mode 22: A rubber composition according to any one of modes 1 to 21 wherein each R4 in formulae (2) and (3) is independently a linear C1-C4 alkylene.

[0094] Mode 23: A rubber composition according to any one of modes 1 to 22 wherein each R4 in formulae (2) and (3) is propylene.

[0095] Mode 24: A rubber composition according to any one of modes 1 to 23 wherein each Zb in formulae (2) and (3) is independently selected from the group consisting of the units of formulae (-O-)0.5, [-OCH2CH2CH2O-]oj5, [-OCH2CH 2CH2CH2O-]0j5 and [-OCH2CH(CH3)CH2O-]0j5.

[0096] Mode 25: A rubber composition according to any one of modes 1 to 24 wherein each Zb in formulae (2) and (3) is of formula (-O-)0.5 or [-OCH2 CH(CH3)CH20-]0.5.

[0097] Mode 26: A rubber composition according to any one of modes 1 to 25 wherein each Zc in formulae (2) and (3) is independently selected from the group consisting of the units of formulae [-OCH2CH2CH2O-]0j5, [-OCH2CH2CH2CH2 O-]0.5 and [-OCH2CH(CH3)CH2O-]0.5.

[0098] Mode 27: Rubber composition according to any one of modes 1 to 26 in which each Zc in formulae (2) and (3) is of formula [-OCH2CH(CH3)CH2 0-]o,5-

[0099] Mode 28: A rubber composition according to any one of modes 1 to 27 wherein each X in formulas (2) and (3) is independently selected from the group consisting of hydroxyl, methoxy, ethoxy, methyl, ethyl, 3-hydroxypropoxy, 3-hydroxy-2-methylpropoxy and 4-hydroxybut-1-oxy.

[0100] Mode 29: A rubber composition according to any one of modes 1 to 28 wherein each X in formulae (2) and (3) is the same and is selected from the group consisting of hydroxyl, methoxy, ethoxy and 3-hydroxy-2-methylpropoxy.

[0101] Mode 30: Rubber composition according to any one of modes 1 to 29 in which the organofunctional silane has a molar percentage of blocked mer-captosilane units (A) ranging from 20 to 80% and a molar percentage of mercaptosilane units (B) ranging from 80 to 20%.

[0102] Mode 31: Rubber composition according to any one of modes 1 to 30 in which the organofunctional silane has a molar percentage of blocked mercaptosilane units (A) ranging from 40 to 60% and a molar percentage of mercaptosilane units (B) ranging from 60 to 40%.

[0103] Mode 32: Rubber composition according to any one of modes 1 to 31 in in which the organofunctional silane has a molar percentage of blocked mer-captosilane units ranging from 50 to 55% and a molar percentage of mercap-tosilane units ranging from 50 to 45%.

[0104] Mode 33: Rubber composition according to any one of modes 1 to 32 in which the level of the organofunctional silane coupling agent varies from 1 to 15 pce.

[0105] Mode 34: Rubber composition according to any one of modes 1 to 33 in which the level of the organofunctional silane coupling agent varies from 1.5 to 10 pce, preferably from 2 to 5 pce.

[0106] Mode 35: Tire which comprises a rubber composition defined in any one of modes 1 to 34, preferably in its tread.

[0107] The aforementioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes. Examples

[0108] Properties at break: Tensile tests are used to determine the properties at break. Unless otherwise stated, they are carried out in accordance with French standard NF T 46-002 of September 1988, using a type H2 specimen, with a tensile speed of 500 mm / min. The breaking stresses (in MPa) and the elongations at break (in %) are measured at 23°C ± 2°C according to standard NF T 46-002, and at 100°C ± 2°C. The results are expressed on a base of 100 relative to a control. A value higher than that of the control, arbitrarily set at 100, indicates an improved result, i.e. a measured quantity greater than that of the control.

[0109] Microstructure of elastomers by nuclear magnetic resonance analysis (NMR): The microstructure of the elastomers is determined by ¹H NMR analysis, supplemented by ¹³C NMR analysis when the resolution of the ¹H NMR spectra does not allow the attribution and quantification of all species. The measurements are carried out using a BRUKER 500MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83MHz for carbon observation. For elastomers that are insoluble but have the ability to swell in a solvent, a 4mm z-grad HRMAS probe is used to observe the proton and carbon in proton decoupled mode. The spectra are acquired at rotation speeds of 4000Hz to 5000Hz. For measurements on soluble elastomers, a liquid NMR probe is used to observe the proton and carbon in proton decoupled mode. The preparation of the insoluble samples is done in rotors filled with the material analyzed and a deuterated solvent allowing swelling, generally deuterated chloroform (CDCl3). The solvent used must always be deuterated and its chemical nature can be adapted by those skilled in the art. The quantities of material used are adjusted so as to obtain spectra with sufficient sensitivity and resolution. Soluble samples are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 ml), generally deuterated chloroform (CDCl3). The solvent or solvent blend used must always be deuterated and its chemical nature can be adapted by those skilled in the art. In both cases (soluble sample or swollen sample): For proton NMR, a single 30° pulse sequence is used. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules. The accumulation number is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement. For carbon NMR, a single 30° pulse sequence is used with proton decoupling only during acquisition to avoid "Nuclear Overhauser" (NOE) effects and remain quantitative. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules. The accumulation number is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling delay between each pulse is adapted to obtain a quantitative measurement. NMR measurements are carried out at 25°C.

[0110] Glass transition temperature of polymers: The glass transition temperature (Tg) is measured using a differential scanning calorimeter according to ASTM D3418 (1999). [YES] Mooney Viscosity: The Mooney viscosity is measured using an oscillating consistometer as described in ASTM D1646 (1999). The measurement is carried out according to the following principle: the sample analyzed in the raw state (i.e., before curing) is molded (shaped) in a cylindrical enclosure heated to a given temperature (100°C). After 1 minute of preheating, the rotor rotates within the test piece at 2 revolutions / minute and the torque used to maintain this movement is measured after 4 minutes of rotation. The Mooney viscosity (ML) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton.meter).

[0112] Preparation of rubber compositions: Three rubber compositions C1 to C3 are prepared. The following procedure is used to manufacture these compositions: The elastomer, then the silica, the silane coupling agent, and the various other ingredients, with the exception of the vulcanization system, are introduced into an internal mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 80°C. Thermomechanical work (non-productive phase) is then carried out in one step, lasting approximately 5 to 6 minutes, until a maximum "fall" temperature of 160°C is reached. The mixture thus obtained is recovered, cooled, and then sulfur and a sulfenamide-type accelerator are incorporated into a mixer (homo-finisher) at 23°C, mixing everything (productive phase) for an appropriate time (for example, between 5 and 12 minutes).

[0113] Rubber compositions C1 to C3 all contain a highly saturated diene elastomer, elastomer E1, a vulcanization system, a silica and a silane coupling agent. They differ from each other by the chemical nature of the silane coupling agent. In the rubber composition Cl, the silane coupling agent is a polysulfide silane, bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT, of formula [(C2H5O)3Si(CH2)3S2]2 marketed under the name “Si69” by the company Evonik. In rubber composition C2, the coupling agent is S-(octanoyl)mercaptopropyltriethoxysilane, marketed under the name “NXT” by the company Momentive. In the C3 rubber composition, the silane coupling agent is “NXT-Z45” marketed by the Momentive company.

[0114] Rubber compositions C1 and C2 are rubber compositions not in accordance with the invention, since the silane coupling agent does not correspond to formula (1) of the organofunctional silane. Rubber composition C3 is a rubber composition in accordance with the invention, since the coupling agent is an organofunctional silane which corresponds to formula (1).

[0115] The formulations (in pce) of the rubber compositions C1 to C3 are described in Table 1 (Table 1). The total sulfur content is identical for each of the rubber compositions, knowing that in the case of rubber composition Cl, the coupling agent “Si69” releases free sulfur during its reaction with the elastomer, which represents a source of sulfur available for vulcanization, i.e. 0.3 pce.

[0116] Three other rubber compositions C4 to C6 are prepared according to the same procedure as compositions C1 to C3. They are all in accordance with the invention, since they all contain a highly saturated diene elastomer (EI), a vulcanization system, a silica and an organofunctional silane coupling agent of formula (1), “NXT-Z45”. Compositions C4 and C5 differ composition C3 by the content of “NXT-Z45”. Composition C6 differs from composition C3 by the vulcanization system, since the vulcanization accelerator is a thiuram disulfide instead of a sulfenamide. The formulations (in pce) of rubber compositions C1 to C3 are described in Table 2 (Table 2).

[0117] The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties after vulcanization at 150°C (cooked state), or in the form of profiles which can be used directly, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires.

[0118] Elastomer El is a highly saturated diene elastomer, a copolymer of ethylene and 1,3-butadiene prepared according to the following procedure: In a 70 L reactor containing methylcyclohexane (64 L), ethylene (5600 g) and 1,3-butadiene (2948 g), butyloctylmagnesium (BOMAG) dissolved in methylcyclohexane and the catalytic system is added. The Mg / Nd ratio is 6.2. The volume of the solution of the catalytic system introduced is 840 mL, the concentration of the catalytic system solution in Nd being 0.0065 M. The reaction temperature is regulated at a temperature of 80 ° C and the polymerization reaction starts. The polymerization reaction proceeds at a constant pressure of 8.3 bar. The reactor is supplied throughout the polymerization with ethylene and 1,3-butadiene in the molar proportions 73 / 27. The polymerization reaction is stopped by cooling, degassing the reactor and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered after steam stripping and drying to constant mass.The polymerization time is 225 minutes. The weighted mass (6.206 kg) allows the average catalytic activity of the catalytic system to be determined, expressed in kilograms of synthesized polymer per mole of neodymium metal per hour (kg / mol.h). The copolymer has an ML value of 62. The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from a metallocene, [Me2Si(Flu)2Nd(q-BH4)2Li(THF)] at 0.0065 mol / L, a co-catalyst, butyloctylmagnesium (BOMAG) whose BOMAG / Nd molar ratio is equal to 2.2, and a preformed monomer, 1,3-butadiene whose 1,3-butadiene / Nd molar ratio is equal to 90. The medium is heated to 80°C for a period of 5 hours. It is prepared according to a preparation method in accordance with paragraph II. 1 of patent application WO 2017093654 AL

[0119] The results of the cured fracture properties of the rubber compositions are recorded in Table 3 and in Table 4.

[0120] Table 3 shows that rubber composition C3 is the rubber composition which exhibits the best properties at break both at 23°C and at 100°C. Both the elongations at break and the stresses at break of rubber composition C3 are respectively much higher than the elongations at break and the stresses at break of compositions C1 and C2, both at 23°C and at 100°C.

[0121] Table 4 shows that the improvement in breaking properties is also obtained for levels of silane coupling agent “NXT-Z45” different from those of composition C3, as well as for a different vulcanization system.

[0122] [Tables 1] Composition Cl C2 C3 El (1) 100 100 100 Silica (2) 38 38 38 Coupling agent “Si69” (3) 3.1 Coupling agent “NXT” (4) 4.2 Coupling agent “NXT-Z45” (5) 2.6 DPG (6) 1.2 1.2 1.2 Wax Ozone (7) 1 1 1 Antioxidant 6PPD (8) 2 2 2 Stearic acid (9) 2 2 2 ZnO (10) 2.5 2.5 2.5 Sulphur 1 1.3 1.3 CBS (11) 1 1 1

[0123] [Tables2] Composition C4 C5 C6 El (1) 100 100 100 Silica (2) 38 38 38 Coupling agent “NXT-Z45” (5) 3.1 4 2.6 DPG (6) 1.2 1.2 1.2 Wax Ozone (7) 1 1 1 Antioxidant 6PPD (8) 2 2 2 Stearic acid (9) 2 2 2 ZnO (10) 2.5 2.5 2.5 Sulphur 1.3 1.3 0.8 CBS (11) 1 1 0.5 TBZTD (12) 0.15

[0124] (1) Copolymer of ethylene and 1,3-butadiene containing 74 mol% of unit ethylene, 19% butadiene unit in the form of 1,2 and 1,4 units and 7 mol% 1,2-cyclohexanediyl unit, Tg -44°C (2) “Zeosil 1165 MP” from Solvay-Rhodia in the form of microbeads (3) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from Evonik (4) Silane 3-octanoylthio-l-propyltriethoxy silane (“NXT”) - CAS 220727-26-4 - Momentive company (5) Silane Mercapto - Thiocarboxylate Oligomer (“NXT-Z45”) - CAS 922519-17-3 - Momentive Company (6) Diphenylguanidine “Perkacit DPG” from Flexsys (7) Anti-ozone wax “VARAZON 4959” from the company Sasol Wax (8) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine “Santoflex 6PPD” from Flexys (9) Stearic acid “Pristerene 4931” from Uniqema company (10) Industrial grade Zinc Oxide from Umicore (11) N-cyclohexyl-2-benzothiazol-sulfenamide “Santocure CBS” from Flexsys (12) Tetrabenzylthiuram disulfide ("Perkacit TBZTD" from Flexsys)-CAS 10591-85-2

[0125] [Tables3] Composition Tl Cl C2 Breaking strain at 23°C 100 104 126 Breaking stress at 23°C 100 100 144 Breaking strain at 100°C 100 106 149 Breaking stress at 100°C 100 112 146

[0126] [Tables4] Composition C3 C4 C5 C6 Breaking strain at 23°C 100 104 108 105 Breaking stress at 23°C 100 106 101 100 Breaking strain at 100°C 100 121 136 109 Breaking stress at 100°C 100 111 111 98

Claims

Claims

1. A rubber composition which comprises: - a highly saturated diene elastomer which is a copolymer of ethylene and a 1,3-diene which comprises ethylene units which represent more than 50 mol% of the monomer units of the copolymer, - a vulcanization system, - a reinforcing filler which contains a silica, - and an organofunctional silane coupling agent having at least one blocked thiol function, at least one thiol function and at least one function which is a hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group and corresponding to the formula (1) (A)p(B)q(l) in which A and B respectively represent a blocked mercaptosilane unit corresponding to the formula (2) and a mercaptosilane unit corresponding to the formula (3) 7th yw R3—C— S—R4 —Si--Zfav || | (2) O Xu ZCw HS--R4—Si---pj Xu in which R3 is selected from a hydrogen atom, a linear or branched C1-C18 alkyl, a linear or branched C2-C18 alkenyl, each R4 is independently selected from linear or branched C1-C6 saturated divalent hydrocarbon groups, each Zb which forms a bridging structure between a silicon atom of one unit and a silicon atom of another unit, these units being able to be identical or different, is independently selected from (—O—)0.5 and [-O(R°CR°)fO-]o.5 with the symbols R°, identical or different, each representing a hydrogen atom or a C1-C3 alkyl and f being a number in a range from 2 to 15, each Zc which forms a cyclic structure with the silicon atom of a unit is a group of formula [-O(R°CR0)fO-]oJ5 with R° and f as defined above, each X is independently selected from a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxyl group and a group of formula HO(R0CR°)fO- with R° and f as defined above, with u+v+2w=3, u being a number equal to 0, 1, 2 or 3, v being a number equal to 1, 2 or 3 and w being a number equal to 0 or 1, p is a number in a range from 1 to 20, q is a number in a range from 1 to 20.

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

3. A rubber composition according to any one of claims 1 to 2, wherein the ethylene units in the highly saturated diene elastomer represent at least 60 mol% of all the monomer units of the highly saturated diene elastomer, preferably at least 65 mol% of all the monomer units of the highly saturated diene elastomer, more preferably at least 70 mol% of all the monomer units of the highly saturated diene elastomer.

4. A rubber composition according to any one of claims 1 to 3, wherein the ethylene units in the highly saturated diene elastomer represent at most 90 mol% of all the monomer units of the highly saturated diene elastomer, preferably at most 85 mol% of all the monomer units of the highly saturated diene elastomer.

5. A rubber composition according to any one of claims 1 to 4 wherein the ethylene units in the highly saturated diene elastomer represent at most 80 mol% of all the monomer units of the highly saturated diene elastomer.

6. A rubber composition according to any one of claims 1 to 5 wherein the highly saturated diene elastomer is a random copolymer.

7. Rubber composition according to any one of claims 1 to 6 in which the silica represents more than 50% by mass of the reinforcing filler, preferably more than 85% by mass of the reinforcing filler.

8. A rubber composition according to any one of claims 1 to 7 wherein R3 in formula (2) is selected from hydrogen, C1-C10 alkyls and C2-C10 alkenyls, preferably is linear C6-C8 alkyl, more preferably is heptyl.

9. A rubber composition according to any one of claims 1 to 8 wherein each R4 in formulas (2) and (3) is independently a linear C1-C4 alkylene, preferably propylene.

10. A rubber composition according to any one of claims 1 to 9 wherein each Zb in formulas (2) and (3) is independently selected from the group consisting of units of formula (-O-)0.5, [-OCH2CH2CH2O-]0.5, [-OCH2CH2CH2CH2O-]0.5 and [-OCH2CH(CH3)CH2O-]0.5, preferably is of formula (-O-)0.5 or [-OCH2 CH(CH3)CH2O-]0.

5.

11. A rubber composition according to any one of claims 1 to 10 wherein each Zc in formulas (2) and (3) is independently selected from the group consisting of units of formula [-OCH2 CH2CH20-]0.5, [-OCH2CH2CH2CH20-]0.5 and [-OCH2CH(CH3)CH2O-]0.5, preferably is of formula [-OCH2CH(CH3)CH2O-]0.

5.

12. A rubber composition according to any one of claims 1 to 11 wherein each X in formulas (2) and (3) is independently selected from the group consisting of hydroxyl, methoxy, ethoxy, methyl, ethyl, 3-hydroxypropoxy, 3-hydroxy-2-methylpropoxy and 4-hydroxybut-1-oxy, preferably each X in formulas (2) and (3) is the same and is selected from the group consisting of hydroxyl, methoxy, ethoxy and 3-hydroxy-2-methylpropoxy.

13. Rubber composition according to any one of claims 1 to 12 wherein the organofunctional silane has a molar percentage of blocked mercaptosilane units (A) ranging from 20 to 80% and a molar percentage of mercaptosilane units (B) ranging from 80 to 20%, preferably the organofunctional silane has a molar percentage of blocked mercaptosilane units (A) ranging from 40 to 60% and a molar percentage of mercaptosilane units (B) ranging from 60 to 40%, more preferably the organofunctional silane has a molar percentage of blocked mercaptosilane units ranging from 50 to 55% and a molar percentage of mercaptosilane units ranging from 50 to 45%.

14. A tire which comprises a rubber composition defined in any one of claims 1 to 13, preferably in its tread.