Rubber composition

Abstract

The present invention relates to a rubber composition comprising a reinforcing filler, a crosslinking system, an elastomer A, a statistical copolymer comprising monomer units of a 1,3-diene, monomer units of an ester of methacrylic acid corresponding to the formula CH2 = CMe - COOR1 and monomer units of an acrylic acid ester corresponding to formula (II) CH2 = 5 CH - COOR2, Me being a methyl group, R1 and R2 being alkyl groups, the monomer units of the 1,3-diene representing from 10 to 70 mol% of the monomer units of the elastomer A, the monomer units of the methacrylic acid ester representing n mol% of the monomer units of the elastomer A, n being greater than or equal to 15 and the monomer units of the ester of the acrylic acid representing m mol% of the monomer units of the elastomer A, n being greater than or equal to m and less than or equal to 3m. The rubber composition makes it possible in particular to improve the compromise between the rolling resistance and the handling performance of the tyre comprising the rubber composition in its tread.

Description

[0001] Rubber composition

[0002] The field of the present invention is that of rubber compositions reinforced by a reinforcing filler, particularly used in the manufacture of tires for vehicles.

[0003] One of the requirements for a tire tread is to minimize its contribution to the tire's rolling resistance, meaning it should be as hysteresis-free as possible. It is well known that those skilled in the art can achieve this property by reducing the amount of reinforcing filler in the rubber compound used to make the tread.

[0004] However, at the same time, the tire tread must also ensure good vehicle handling, which notably involves efficient force transmission between the rim and the road surface during cornering and therefore requires sufficient tread rigidity. This rigidity can typically be achieved by increasing the amount of reinforcing filler in the rubber compound used to make the tread.

[0005] Thus, the rubber composition of the tread must satisfy potentially conflicting requirements, namely to exhibit hysteresis as low as possible to meet the rolling resistance requirement, and to exhibit rigidity as high as possible to meet the road behavior requirement.

[0006] To reduce the rolling resistance of a tire tread, it has been proposed to introduce into the rubber composition of the tread elastomers comprising methacrylic acid ester monomer units bearing a silica-interacting functional group, such as an alcohol. The mass percentages of methacrylic acid ester monomer units in the elastomer are generally less than 20% of the elastomer's mass, which represents a molar content of methacrylic acid ester monomer units much lower than 20%, considering the respective molar masses of the constituent monomer units of the elastomer. See, for example, the publication of patent application EP 1 308 318.

[0007] Subsequently, it was discovered that the introduction, into a rubber composition constituting a tire tread, of a particular elastomer whose monomer units comprise at least 20 mole percent of monomer units of a methacrylic acid ester, preferably a methacrylate of an alkyl having 4 carbon atoms, makes it possible to significantly improve the wet grip performance of the tire, as described in publications EP3164453A1 and WO2024 / 126166.

[0008] The Applicant, continuing its research efforts, discovered that the choice, as an elastomer comprising monomer units of a methacrylic acid ester, of a statistical copolymer comprising monomer units of a 1,3-diene, monomer units of a particular methacrylic acid ester and monomer units of a particular acrylic acid ester, these monomer units being present in specific proportions, makes it possible to obtain a rubber composition with reduced hysteresis but with sufficiently high rigidity.

[0009] 2020PAT00112FR Thus, a first object of the invention is a rubber composition comprising:

[0010] - a reinforcing load

[0011] - a crosslinking system

[0012] - an elastomer A, a statistical copolymer comprising monomeric units of a 1,3-diene, monomeric units of a methacrylic acid ester corresponding to formula (I)

[0013] CH2 = CMe - COOR 1 and monomer units of an acrylic acid ester corresponding to the formula (II) CH2= CH - COOR 2 , Me being a methyl group, R 1 and R 2 being alkyl groups, the monomer units of 1,3-diene representing 10 to 70% by mole of the monomer units of elastomer A, the monomer units of methacrylic acid ester representing n% by mole of the monomer units of elastomer A, n being greater than or equal to 15 and the monomer units of acrylic acid ester representing m% by mole of the monomer units of elastomer A, n being greater than or equal to m and less than or equal to 3m.

[0014] Another object of the invention is a semi-finished product comprising a rubber composition according to the invention.

[0015] The invention also relates to a tire comprising a semi-finished product according to the invention or a rubber composition according to the invention.

[0016] Detailed description

[0017] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., bounds a and b excluded) 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 bounds a and b).

[0018] All percentages are mass percentages unless otherwise stated.

[0019] The abbreviation "pce" means parts by weight per hundred parts of elastomers present in the elastomer matrix.

[0020] The term elastomer matrix refers to all the elastomers present in the composition of rubber.

[0021] The compounds mentioned in the description (typically polymers, fillers, plasticizers, coupling agents, the vulcanization system, other additives, etc.) can be of fossil origin or bio-based. In the latter case, they may be partially or entirely derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of previously used materials; that is, they may be partially or entirely produced through a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0022] In this application, a carbon chain is defined as a chain that contains one or more carbon atoms.

[0023] In this application, we will note C x a carbon chain (saturated or unsaturated) comprising x carbon atoms (x being an integer) and C x -C y a carbon chain (saturated or unsaturated) containing from x to y carbon atoms (y also being an integer). The designation alkyl C x

[0024] 2020PAT00112FR is used to denote an alkyl group consisting of a carbon chain having x carbon atoms. The designation alkyl C x -C y is used to refer to an alkyl consisting of a carbon chain having x to y carbon atoms.

[0025] The invention described in more detail below relates to at least one of the objects defined according to any one of the following embodiments:

[0026] 1. Rubber composition comprising:

[0027] - a reinforcing load

[0028] - a crosslinking system

[0029] - an elastomer A, a statistical copolymer comprising monomeric units of a 1,3-diene, monomeric units of a methacrylic acid ester corresponding to the formula (I) CH2= CMe - COOR 1 and monomer units of an acrylic acid ester corresponding to the formula (II) CH2= CH - COOR 2 , Me being a methyl group, R 1 and R 2 being alkyl groups, the monomer units of 1,3-diene representing 10 to 70% by mole of the monomer units of elastomer A, the monomer units of methacrylic acid ester representing n% by mole of the monomer units of elastomer A, n being greater than or equal to 15 and the monomer units of acrylic acid ester representing m% by mole of the monomer units of elastomer A, n being greater than or equal to m and less than or equal to 3m.

[0030] 2. Rubber composition according to embodiment 1 in which R 1is an alkyl group C2-Cio, preferably an alkyl group C2-C8, more preferably an alkyl group C4, even more preferably an n-butyl group.

[0031] 3. Rubber composition according to any one of the preceding embodiments, wherein R 2 is an alkyl group C2-Ci0, preferably an alkyl group C2-C8, more preferably an alkyl group C4, even more preferably an n-butyl group.

[0032] 4. Rubber composition according to any one of the preceding embodiments in which R 1 and R 2 are identical.

[0033] 5. Rubber composition according to any one of the preceding embodiments in which elastomer A is a copolymer of 1,3-diene, methacrylic acid ester and acrylic acid ester.

[0034] 6. Rubber composition according to any one of the preceding embodiments wherein the 1,3-diene is 1,3-butadiene or isoprene or a mixture of 1,3-butadiene and isoprene, preferably 1,3-butadiene.

[0035] 7. Rubber composition according to any one of the preceding embodiments wherein the 1,3-diene monomer units represent 40 to 60 mole percent of the elastomer A monomer units, the methacrylic acid ester monomer units represent 20 to 45 mole percent of the elastomer A monomer units and the acrylic acid ester monomer units represent 10 to 30 mole percent of the elastomer A monomer units.

[0036] 8. Rubber composition according to any of the preceding embodiments in which the reinforcing filler comprises silica.

[0037] 9. Rubber composition according to embodiment 8 in which silica represents more than 50% by mass of the reinforcing filler, preferably more than 80% by mass of the reinforcing filler.

[0038] 10. Rubber composition according to any one of the preceding embodiments in which

[0039] 2020PAT00112FR the reinforcing load rate is within a range of 20 to 120 pc, preferably from 40 to 100 pc.

[0040] 11. Rubber composition according to any of the preceding embodiments wherein the crosslinking system is a vulcanization system.

[0041] 12. Semi-finished product comprising a rubber composition according to any of the preceding embodiments.

[0042] 13. Semi-finished product according to embodiment 12 characterized in that it is a tread for a tire.

[0043] 14. Pneumatics comprising a semi-finished product according to any one of embodiments 12 to 13 or a rubber composition according to any one of embodiments 1 to 11.

[0044] Elastomer

[0045] An essential characteristic of the rubber composition of the invention is that it comprises an elastomer A, a statistical copolymer comprising monomer units of a 1,3-diene, monomer units of a methacrylic acid ester and monomer units of an acrylic acid ester.

[0046] The methacrylic acid ester useful for the purposes of the invention corresponds to the following formula (I): CH2= CMe - COOR 1 (I) in which Me is a methyl group and R 1 is an alkyl group.

[0047] Preferably, R 1is a C2-C10 alkyl group, preferably a C2-C8 alkyl group, more preferably a C4 alkyl group, and even more preferably an n-butyl group. According to this embodiment, the methacrylic acid ester useful for the purposes of the invention is n-butyl methacrylate.

[0048] The monomer units of methacrylic acid ester represent n% by mole of the monomer units of elastomer A, n being greater than or equal to 15. Below this value, the effect of the presence of the monomer units of methacrylic acid ester might not be sufficiently visible on the properties of elastomer A.

[0049] The acrylic acid ester useful for the purposes of the invention corresponds to the following formula (II):

[0050] CH2 = CH - COOR 2 (II) in which R 2 is an alkyl group.

[0051] Preferably, R 2is a C2-C10 alkyl group, preferably a C2-C8 alkyl group, more preferably a C4 alkyl group, and even more preferably an n-butyl group. According to this embodiment, the acrylic acid ester useful for the purposes of the invention is n-butyl acrylate.

[0052] According to one embodiment of the invention, R 2 is identical to R 1 and thus, according to a preferred embodiment, R 1 and R 2 are both n-butyl groups and, in this preferred embodiment, the methacrylic acid ester and the acrylic acid ester are respectively n-butyl methacrylate and n-butyl acrylate.

[0053] The preferred natures of the R groups 1 and R 2 can be applied to any of the embodiments of the invention.

[0054] 2020PAT00112FR The monomer units of acrylic acid ester represent m% in moles of the monomer units of elastomer A, m being such that n is greater than or equal to m but less than or equal to 3m. Indeed, for the effect of the presence of the monomer units of acrylic acid ester to be perceptible on the properties of the rubber composition, it is necessary that the proportion, in moles, of the units of acrylic acid ester in elastomer A (m) be at least equal to 25% of the proportion, in moles, of all the monomer units of methacrylic acid ester and the monomer units of acrylic acid ester in elastomer A (n+m).Furthermore, in order to maintain the effect of the presence of methacrylic acid ester monomer units in elastomer A, the proportion, in moles, of methacrylic acid ester monomer units in elastomer A must be at least as high as the proportion, in moles, of acrylic acid ester monomer units in elastomer A. It follows from the fact that n is less than or equal to 3m and from the fact that n is greater than or equal to 15, that m is necessarily greater than or equal to 5, that is to say that elastomer A contains at least 5% in moles of acrylic acid ester monomer units.

[0055] As examples of 1,3-dienes whose monomeric units constitute elastomer A, the following are particularly suitable:

[0056] 1,3-Butadiene, 2-methyl-1,3-butadiene, 2,3-di(α-Ikyl C1-C5)-1,3-butadiene such as, for example,

[0057] 2,3-Dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene. 1,3-Diene is preferably the

[0058] 1,3-Butadiene, isoprene, or a mixture of 1,3-butadiene and isoprene. More preferably, 1,3-diene is 1,3-butadiene.

[0059] These preferred natures for 1,3-diene whose monomer units are part of the composition of elastomer A can be applied to any of the embodiments of the invention.

[0060] The monomer units of 1,3-diene represent 10 to 70% by mole of the monomer units of elastomer A.

[0061] According to one embodiment of the invention, the monomer units of 1,3-diene represent 40 to 60% by mole of the monomer units of elastomer A, the monomer units of methacrylic acid ester represent 20 to 45% by mole of the monomer units of elastomer A and the monomer units of acrylic acid ester represent 10 to 30% by mole of the monomer units of elastomer A.

[0062] These preferred ranges of mole fraction of the monomer units of 1,3-diene, methacrylic acid ester and acrylic acid ester in the monomer units of elastomer A can be applied to any of the embodiments of the invention.

[0063] According to one embodiment of the invention, elastomer A is an elastomer obtained by radical polymerization, particularly in bulk, in solution, or in dispersed media, notably in emulsions, dispersions, or suspensions. Radical polymerization, particularly in bulk, in solution, or in dispersed media, is a process well known to those skilled in polymer synthesis. The choice of one or another of these three processes can be guided, for example, by the reactivity of the monomers to be polymerized, the polymerization kinetics, or the exothermicity of the polymerization reaction. For the choice of the polymerization process, reference may be made, for example, to the following publications: Macromolecules, 1998, 31, 2822-2827; Macromolecules, 2006, 39, 923-930; J. Am. Chem. Soc. 1951, 73, 5736. This embodiment can be applied to any of the embodiments of the invention.

[0064] 2020PAT00112FR According to one embodiment of the invention, elastomer A comprises only monomers of 1,3-diene as defined above, monomers of methacrylic acid ester of formula (I), and monomers of acrylic acid ester of formula (II), to the exclusion of any other type of monomer. Elastomer A is thus a random copolymer of 1,3-diene, methacrylic acid ester, and acrylic acid ester. This embodiment can be applied to any of the embodiments of the invention.

[0065] Elastomer A can then be obtained by radical polymerization of 1,3-diene, methacrylic acid ester and acrylic acid ester according to one of the processes mentioned above.

[0066] Elastomer A itself can consist of a single elastomer or of several elastomers which differ from each other by their composition or their macrostructure (in particular the distribution of molar masses of the polymer chains which compose them).

[0067] The rubber composition may include, in addition to elastomer A, other elastomers. Other suitable elastomers include those commonly used in rubber compositions for tire manufacturing, such as polyisoprenes, polybutadienes, isoprene copolymers, and butadiene copolymers such as butadiene-styrene copolymers.

[0068] According to any one embodiment of the invention, the proportion of elastomer A in the rubber composition is preferably greater than 50 parts per annum, more preferably greater than 80 parts per annum, and even more preferably equal to 100 parts per annum. When elastomer A is used at a proportion of 100 parts per annum, it is then the only elastomer present in the rubber composition.

[0069] These preferred variants of the elastomer A content in the rubber composition can be applied to any of the embodiments of the invention.

[0070] The rubber composition according to the invention comprises a reinforcing filler which, according to one embodiment of the invention, comprises silica.

[0071] The silica (SiO2) used can be any reinforcing silica known to those skilled in the art, including any precipitated or pyrogenated silica. Examples of highly dispersible precipitated silicas (known as "HDS") include "Ultrasil" 7000 and "Ultrasil" 7005 from Degussa, "Zeosil" 1165MP, 1135MP and 1115MP from Rhodia, "Hi-Sil" EZ150G from PPG, "Zeopol" 8715, 8745 and 8755 from Huber, and high specific surface area silicas as described in application WO 03 / 016387.

[0072] The physical state in which the silica is presented is irrelevant, whether it is in the form of powder, microbeads, granules, or balls.

[0073] According to one embodiment of the invention, silica represents more than 50% by mass of the reinforcing filler: silica is then the major reinforcing filler by mass. Preferably, silica represents more than 80% by mass of the reinforcing filler. These preferred ranges of silica mass proportions in the reinforcing filler can be applied to any one of the embodiments of the invention.

[0074] 2020PAT00112FR Note that the reinforcing filler may contain, in addition to silica, at least one other reinforcing filler which may be an inorganic reinforcing filler or an organic reinforcing filler.

[0075] In this application, "reinforcing inorganic filler" is defined as any inorganic or mineral filler (regardless of its color and origin (natural or synthetic)), also called "white" filler, "light" filler, or even "non-black filler" ("non-black filler") as opposed to carbon black, capable of reinforcing, on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words, capable of replacing, in its reinforcing function, a conventional carbon black of tire grade; such a filler is generally characterized, in a known way, by the presence of hydroxyl groups (-OH) on its surface.As a reinforcing inorganic filler other than silica, we will also mention mineral fillers of the aluminous type, in particular alumina (Al2O3) or aluminum (oxide)hydroxides, or even reinforcing titanium oxides, for example described in US 6 610 261 and US 6 747 087.

[0076] If the reinforcing filler contains an organic reinforcing filler, the organic reinforcing filler is preferably carbon black. This organic reinforcing filler, preferably carbon black, is then preferentially present in a weight percentage of less than 50% of the mass of the reinforcing filler.

[0077] In the specific embodiment where silica represents more than 50% by mass of the reinforcing filler, carbon black is preferably used at a concentration below 20%, more preferably below 10% (for example, between 0.5 and 20%, particularly between 2 and 10%), and even more preferably below 5%. Within the indicated ranges, the coloring (black pigmenting agent) and UV-resistant properties of carbon black are utilized without compromising the typical performance provided by the reinforcing inorganic filler.

[0078] All carbon blacks are suitable, including those conventionally used in tires. Among these, particularly the reinforcing carbon blacks of the 100, 200, and 300 series, or the 500, 600, and 700 series (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772. These carbon blacks can be used on their own, as commercially available, or in other forms, for example, as a carrier for certain rubber compound additives.

[0079] Preferably, the reinforcing filler content in the rubber compound is between 20 and 200 parts per cubic inch (ppc). Below 20 ppc, the reinforcement of the rubber compound is insufficient to provide an adequate level of cohesion or wear resistance. Above 200 ppc, there is a risk of increased hysteresis and therefore increased tire rolling resistance. More preferably, the reinforcing filler content in the rubber compound ranges from 20 to 120 ppc, and even more preferably from 40 to 100 ppc. These preferred ranges of reinforcing filler content can be applied to any of the embodiments of the invention.

[0080] 2020PAT00112FR In embodiments where the reinforcing filler includes silica, and in particular where silica constitutes more than 50% by weight of the reinforcing filler of the rubber composition, a coupling agent (or bonding agent) is typically used in a well-known manner to couple the silica to at least one of the elastomers that constitute the elastomeric matrix of the rubber composition.

[0081] As is well known, a coupling agent is an agent capable of establishing a sufficient chemical and / or physical bond between the filler in question and the elastomer, while also facilitating the dispersion of this filler within the elastomer matrix. This at least bifunctional agent is designed to ensure a sufficient chemical and / or physical connection between the inorganic filler, in this case silica, and the elastomer. Organosilanes, particularly polysulfurized alkoxysilanes or mercaptosilanes, or polyorganosiloxanes, are used. These polyorganosiloxanes possess functional groups capable of binding physically and / or chemically to the inorganic filler and functional groups capable of binding physically and / or chemically to the elastomer, for example, via a sulfur atom.Silica / elastomer bonding agents, in particular, have been described in a large number of documents, the best known being bifunctional alkoxysilanes such as polysulfide alkoxysilanes. Polysulfide silanes, described as "symmetric" or "asymmetric" depending on their specific structure, are used in particular, as described for example in applications W003 / 002648 (or US 2005 / 016651) and W003 / 002649 (or US 2005 / 016650).

[0082] Examples of coupling agents other than polysulfurized alkoxysilane include bifunctional POSS (polyorganosiloxanes) or polysulfurized hydroxysilanes as described in patent applications WO 02 / 30939 (or US 6,774,255) and WO 02 / 31041 (or US 2004 / 051210), or silanes or POSS bearing azo-dicarbonyl functional groups, as described for example in patent applications WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534.

[0083] Alkoxysilanes bearing an amine function, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethyltriethoxysilane, available for example from suppliers Sigma-Aldrich, Gelest and Molport, are also suitable as coupling agents.

[0084] The coupling agent content in the rubber composition according to the invention, whether a single compound or a mixture of compounds, is advantageously less than 20 parts per million (ppm), it being understood that it is generally desirable to use as little as possible. Typically, the coupling agent content is from 0.5% to 15% by weight relative to the amount of silica. Its content is preferably between 0.5% and 12 ppm, more preferably within a range of 3% to 10 ppm. This content is readily adjusted by those skilled in the art according to the amount of silica used in the composition, and its preferred ranges are applicable to any of the embodiments of the invention.

[0085] Crosslinking system

[0086] Another essential characteristic of the composition according to the invention is that it includes a crosslinking system.

[0087] The crosslinking system may be based on sulfur, peroxides, or mixtures thereof. In other words, crosslinking may rely on reactions involving sulfur, peroxides, or both. The proportion of the compound(s) constituting the crosslinking system introduced into the rubber composition is adjusted by a person skilled in the art according to the desired degree of crosslinking of the rubber composition and the chemical nature of the crosslinking system. This degree of crosslinking is determined by a person skilled in the art according to the desired stiffness of the crosslinked rubber composition, this stiffness varying according to the intended application of the rubber composition.

[0088] The crosslinking system according to the invention is preferably a vulcanization system, that is to say, a system based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. To this basic vulcanization system, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retardants may be added, incorporated during the first non-productive phase and / or during the productive phase as described later.A primary or secondary vulcanizing accelerator may be cited as any compound capable of acting as a vulcanizing accelerator for diene elastomers in the presence of sulfur, particularly thiazole-type accelerators and their derivatives, sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate-type accelerators. Sulfur is used at a preferential concentration between 0.5 and 12 parts per million (ppm), particularly between 1 and 10 ppm. The primary vulcanizing accelerator is used in the rubber compound at a preferential concentration between 0.5 and 10 ppm, more preferably between 0.5 and 5.0 ppm. These preferred ranges for sulfur and accelerator concentrations may be applied to any of the embodiments.

[0089] The rubber composition according to the invention may also contain coupling activators, silica coating agents or more generally processing aids capable, in a known manner, through an improvement in the dispersion of the filler in the elastomer matrix and a reduction in the viscosity of the rubber composition, of improving its processing ability in the raw state, these agents being for example hydrolyzable silanes such as alkylalkoxysilanes, polyols, polyethers, hydroxylated or hydrolyzable polyorganosiloxanes.

[0090] Additives

[0091] The rubber composition according to the invention may also include all or part of the usual additives commonly used in rubber compositions for the manufacture of tires, such as plasticizers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents and mixtures of such compounds.

[0092] Manufacturing of the rubber compound

[0093] The rubber composition according to the invention can be manufactured in suitable mixers, generally using two successive preparation phases well known to those skilled in the art: a first thermomechanical working or mixing phase (the so-called "non-productive" phase) at high temperature, up to a maximum temperature between 110°C and 190°C, preferably between 120°C and 180°C, followed by a second mechanical working phase (the so-called "productive" phase) down to a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the crosslinking system is incorporated.

[0094] 2020PAT00112FR The rubber composition according to the invention can be prepared according to a process which comprises the following steps:

[0095] - thermomechanically knead the elastomer matrix, the reinforcing filler, the coupling agent, and the other additives of the rubber composition, with the exception of the crosslinking system, until a maximum temperature of between 110°C and 190°C is reached;

[0096] - cool the assembly to a temperature below 100°C;

[0097] - then incorporate the crosslinking system;

[0098] - knead everything until a maximum temperature below 110°C to obtain a rubber composition.

[0099] After incorporating all the ingredients of the rubber composition, the resulting final composition is then calendered, for example, into a sheet or plate, particularly for laboratory characterization, or extruded to form, for example, a rubber profile used as a rubber component or semi-finished product, particularly for the manufacture of a tire. The rubber composition according to the invention can be used as a calender in a tire. The calender or extrudate formed from the rubber composition constitutes, in whole or in part, a semi-finished product, particularly a tire.

[0100] Thus, according to a particular embodiment of the invention, the rubber composition according to the invention, which can be either in the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization), is in a tire, for example in a tire tread.

[0101] Crosslinking (or curing), where applicable 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 120 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.

[0102] Other objects of the invention

[0103] The semi-finished product according to the invention has the essential characteristic of being composed, in whole or in part, of the rubber composition according to the invention. It can be manufactured according to the process described above, which includes an additional step of calendering or extruding the rubber composition. It is preferably a tire tread.

[0104] The invention also relates to the tread previously described both in the raw state (i.e., before baking) and in the baked state (i.e., after cross-linking or vulcanization).

[0105] The invention also relates to a tire comprising a rubber compound or a semi-finished product according to the invention, which tire exists both in its raw and cured states, the semi-finished product preferably being a tread. In the present invention, the term "tire" (in English, "tire") means a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads intended to contact a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads.A non-pneumatic tire, 2020PAT00112FR, typically comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement that connects to a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being positioned between the base and the crown. Such non-pneumatic tires do not necessarily include a sidewall. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077. According to any one embodiment of the invention, the tire according to the invention is preferably a pneumatic tire.

[0106] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation.

[0107] Examples

[0108] I. Measurements and tests used

[0109] 1.1 Determination of the glass transition temperature of elastomers

[0110] The glass transition temperatures Tg and glass transition widths ATg of the polymers are measured using a Differential Scanning Calorimeter ("Differential Scanning Calorimeter") according to ASTM D3418-08.

[0111] 1.2. Determination of the microstructure of elastomers by NMR (nuclear magnetic resonance) analysis

[0112] The determination of methacrylate unit content and acrylate unit content is performed by 1H NMR analysis. Spectra are acquired on an Avance 500 MHz BROKER spectrometer equipped with a 5 mm z-grad BBFO "broadband" cryoprobe for soluble samples and a 4 mm z-grad HRMAS probe. 1 H / 13 C for partially crosslinked and partially insoluble samples.

[0113] The quantitative 1H NMR experiment uses a simple 30° pulse sequence and a 5-second repetition interval between each acquisition. Samples are solubilized or swollen in deuterated chloroform.

[0114] Chemical shifts are calibrated with respect to the protonated impurity of chloroform (µppm) 1 H to

[0115] 7.2 ppm).

[0116] NMR signal allocation 1 The H values ​​used for quantification in butadiene / alkyl methacrylate / alkyl acrylate copolymers are given in Table 1:

[0117] Table 1

[0118] 2020PAT00112FR

[0119] 1.3 Determination of the macrostructure of elastomers by SEC analysis

[0120] The SEC (Size Exclusion Chromatography) technique is used, which separates macromolecules in solution according to their size using columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first. The SEC is coupled to a refractometer; in this case, it provides relative information. Using commercial standard products, the various number-average molar masses (M) are obtained. n ) and in weight (M w ) which characterize the molar mass distribution of the polymer, can be determined and the polymolecularity index (Ip = M w / M n) calculated via a Moore calibration. There is no special treatment of the polymer sample before analysis. It is simply solubilized in the elution solvent at a concentration of approximately 1 g / L. The solution is then filtered through a 0.45 µm porosity filter before injection.

[0121] The equipment used is a "WATERS alliance" chromatographic system. The elution solvent is tetrahydrofuran, the flow rate is 1 mL / min, the system temperature is 35°C, and the analysis time is 45 min. A set of three AGILENT (Mixed BLS) columns is used. The injected volume of the polymer sample solution is 100 pL. The detector is a "WATERS 2414" differential refractometer, and the chromatographic data processing software is the "WATERS EMPOWER" system.

[0122] The calculated average molar masses are relative to a calibration curve made from commercial standard polystyrenes “PSSREADY CAL-KIT”.

[0123] 1.4 Determination of the loss factor

[0124] The dynamic properties tan θ max are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a vulcanized composition sample (cylindrical specimen 4 mm thick and 400 mm long) is recorded. 2(of section), subjected to a sinusoidal alternating simple shear load at a frequency of 10 Hz, under normal temperature conditions (23°C) according to ASTM D 1349-99. A strain amplitude sweep is performed from 0.1% to 100% (forward cycle), then from 100% to 0.1% (return cycle). The result used is the loss factor tan θ between the values ​​at 0.1% and 100% strain (Payne effect). For the return cycle, the maximum observed value of tan θ is recorded, denoted tan θ max return.

[0125] The maximum return tan θ is a descriptor of the intrinsic rolling resistance performance of the tested rubber compound. Since the results are expressed as a base of 100, a value lower than the reference value, arbitrarily set at 100, indicates an improved result (lower rolling resistance).

[0126] 1.5 Determination of the shear modulus

[0127] The complex shear modulus G* is measured on a Metravib VA4000 or DMA+450 viscoanalyzer using specimens containing a baked rubber compound. The response of the specimen subjected to sinusoidal alternating simple shear loading is recorded.

[0128] 2020PAT00112FR frequency of 10 Hz under specified temperature conditions (here 23°C) according to ASTM D1349-99. A strain amplitude sweep is performed from 0.1% peak-to-peak to 100% peak-to-peak (forward cycle), then from 100% peak-to-peak to 0.1% peak-to-peak (return cycle). The specimen has a cylindrical cross-section as described in ASTM D 5992-96 (version reapproved in 2011, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. The complex dynamic shear modulus G* is defined as the square root of the sum of the squares of G' and G"², where G' represents the elastic modulus and G"² represents the viscous modulus. The complex shear modulus G* is measured at 10% peak-to-peak strain on the return cycle.

[0129] The G* is a descriptor of the intrinsic stiffness of the tested rubber composition. The results are expressed on a base of 100; a value higher than the reference value, arbitrarily set at 100, indicates an improved result (higher stiffness).

[0130] Preparation of elastomers

[0131] The elastomers used for the examples are prepared in the following way:

[0132] Preparation of the following items in advance:

[0133] - We weigh approximately exactly the quantity of solutes to prepare the solutions to a known concentration close to a given value below and preceded by the term "approximately".

[0134] - Suspension in water of Na2FeP2O7 (iron complex) at approximately 0.015 mol / L: FeSO4, 7H2O and Na4P2O7 are diluted in bubbled water, then the mixture is heated to 60°C for 45 minutes while stirring regularly;

[0135] - Preparation of a solution of cumene hydroperoxide (initiator) in alkyl methacrylate or in the mixture of alkyl methacrylate and alkyl acrylate at approximately 0.04 mol / L;

[0136] - Preparation of a tert-dodecylmercaptan (RSH) solution in alkyl methacrylate or in a mixture of alkyl methacrylate and alkyl acrylate at 0.1 mol / L;

[0137] - Preparation of a solution of N,N-diethylhydroxylamine (stopper) in water at approximately 0.05 mol / L in water.

[0138] 1,3-Butadiene and alkyl methacrylates and acrylates are purified by passing through an alumina guard and bubbling with nitrogen.

[0139] A stirred reactor is loaded according to the following operations:

[0140] - introduce the bubbled water for 45 minutes at 25°C;

[0141] - add sodium dodecyl sulfate (surfactant) under nitrogen at 25°C followed by a 10 min nitrogen scan;

[0142] - inject the RSH solution at 25°C under nitrogen;

[0143] - cool the reactor to reach a temperature Tl;

[0144] - inject the rest of the monomer charge, with the exception of 1,3-butadiene, under nitrogen;

[0145] - allow the reactor to cool to temperature Tl, then inject the Na2FeP2O7 solution;

[0146] - inject the 1,3-butadiene;

[0147] 2020PAT00112FR - let it shake for 10 to 15 minutes until the emulsion forms;

[0148] - inject the priming agent and the cumene hydroperoxide solution.

[0149] The end of the addition of the initiator marks the beginning of polymerization (i.e., t=0 min).

[0150] Agitation and temperature T1 are maintained for 1h, then, while maintaining agitation, the temperature is lowered to temperature T2 for the remainder of the polymerization time. To stop the polymerization reaction, the latex is transferred by residual pressure of the monomers into another reactor containing aqueous N,N-diethylhydroxylamine solution (stopper). The latex is then coagulated by adding a mixture of acetone and methanol (acetone / methanol: 50 / 50 by volume) (3 volumes of acetone / methanol to 1 volume of reaction medium). The coagulum is dried under partial vacuum and nitrogen purging for 48 h at 40°C. The polymers are recovered with a volatile matter content of less than 1%.

[0151] Sodium dodecyl sulfate (SDS), iron sulfate, cumene hydroperoxide, sodium pyrophosphate (tetrabasic sodium pyrophosphate), potassium persulfate, terdodecyl mercaptan, N,N-diethylhydroxylamine, n-butyl methacrylate (BuMA), n-butyl acrylate (BuA) are marketed by Aldrich.

[0152] The synthesis conditions for elastomers 1 (1,3-butadiene-n-butyl methacrylate copolymer) and 2 (1,3-butadiene-n-butyl methacrylate-n-butyl acrylate copolymer) are shown in Table 2. The quantities of water and surfactant are given as mass percentages of monomers, calculated by dividing the mass of water or surfactant added by the total mass of monomers added. The quantity of cumene hydroperoxide (initiator) is given as a molar percentage relative to the total quantity of starting monomers. The quantities of RSH, iron complex, and stopper are given as molar equivalents relative to the quantity of initiator. The composition of the starting monomer filler is given as a molar percentage calculated on the total number of moles of monomers composing the starting monomer filler.

[0153] Table 2

[0154] 2020PAT00112FR

[0155] The copolymers obtained possess the following characteristics given in Table 3:

[0156] Table 3

[0157] III. Preparation of rubber compositions

[0158] Two Cl and C2 rubber compositions are prepared. The formulations (in pieces) of the Cl and C2 compositions are described in Table 4.

[0159] Composition C2 conforms to the invention; composition Cl does not conform to the invention. Both rubber compositions Cl and C2 comprise a reinforcing filler (in this case, silica), a crosslinking system, and a statistical copolymer elastomer comprising monomer units of a 1,3-diene (in this case, monomer units of 1,3-butadiene) and monomer units of a methacrylic acid ester (here, monomer units of n-butyl methacrylate) representing n mole percent of the monomer units of elastomer A, n being greater than or equal to 15 (44% for Cl, 25% for C2). In composition Cl, the elastomer is a statistical copolymer of 1,3-diene and the methacrylic acid ester.In composition C2, according to the invention, the elastomer comprises, in addition to the monomer units of 1,3-diene and the monomer units of the methacrylic acid ester, monomer units of an acrylic acid ester (n-butyl acrylate) representing m% in mole of the monomer units of the elastomer, m being less than or equal to n (in this case, m=14 and n=25) and n being less than or equal to 3m (in this case, 3m=42 and n=25).

[0160] The manufacturing process for these compositions is as follows: the elastomer, silica, coupling agent, plasticizer, and various other ingredients, with the exception of the crosslinking system, are successively introduced into an internal mixer (final fill level: approximately 70% by volume), which has an initial tank temperature of approximately 60°C. A thermomechanical process (non-productive phase) is then carried out in a single step, lasting a total of 5 minutes, until a maximum "drop" temperature of 165°C is reached.

[0161] The mixture thus obtained is collected, cooled, and then the crosslinking system is incorporated on a mixer (homo-finisher) at 23°C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

[0162] The compositions thus obtained are then calendered into plates (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical properties after vulcanization for 30 min at 170°C.

[0163] 2020PAT00112FR IV Properties of rubber compositions

[0164] The properties of the Cl and C2 compositions are given as a base of 100 relative to Cl in Table 5.

[0165] Composition C2, according to the invention, has a maximum tan θ return at 23°C and 10Hz significantly lower than that of composition Cl (94 vs 100), which suggests better rolling resistance performance for a tire in which composition C2 is used in the tread than for a tire in which composition Cl is used in the tread.

[0166] Furthermore, the C2 composition, according to the invention, exhibits a G* at 10% deformation at 23°C and 10Hz similar to that of the Cl composition, which allows us to predict a rigidity of the tread and therefore a similar behavior between a tire for which the C2 composition is used in the tread and a tire for which the Cl composition is used in the tread.

[0167] The results obtained therefore show that the composition according to the invention makes it possible here to solve the technical problem in that it results in improved rolling resistance while maintaining good road behavior.

[0168] Table 4

[0169] (1) Copolymer of 1,3-butadiene and n-butyl methacrylate (see paragraph IL)

[0170] (2) Copolymer of 1,3-butadiene, n-butyl methacrylate and n-butyl acrylate (see paragraph

[0171] II-)

[0172] (3) "Zeosil 1165 MP" silica from the company Solvay-Rhodia in the form of microbeads

[0173] (4) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from the Evonik company

[0174] (5) Trioctyl phosphate (tri-2-ethylhexyl phosphate) “Disflamoll TOF” from the Lanxess company

[0175] (6) Diphenylguanidine (“Perkacit” DPG from Flexsys)

[0176] (7) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (“6PPD” from Flexsys)

[0177] (8) ZnO, industrial grade zinc oxide from Umicore

[0178] (9) N-cyclohexyl-2-benzothiazol-sulfenamide (“Santocure CBS” from Flexsys)

[0179] Table 5, 2020PAT00112FR

[0180] 2020PAT00112FR

Claims

Demands 1. Rubber composition comprising: - a reinforcing load - a crosslinking system - an elastomer A, a statistical copolymer comprising monomeric units of a 1,3-diene, monomeric units of a methacrylic acid ester corresponding to formula (I) CH2 = CMe - COOR 1 and monomer units of an acrylic acid ester corresponding to the formula (II) CH2= CH - COOR 2 , Me being a methyl group, R 1 and R 2being alkyl groups, the monomer units of 1,3-diene representing 10 to 70% by mole of the monomer units of elastomer A, the monomer units of methacrylic acid ester representing n% by mole of the monomer units of elastomer A, n being greater than or equal to 15 and the monomer units of acrylic acid ester representing m% by mole of the monomer units of elastomer A, n being greater than or equal to m and less than or equal to 3m.

2. Rubber composition according to claim 1, wherein R 1 is an alkyl group C2-Cio, preferably an alkyl group C2-C8, more preferably an alkyl group C4, even more preferably an n-butyl group.

3. Rubber composition according to any one of the preceding claims, wherein R 2is an alkyl group C2-Ci0, preferably an alkyl group C2-C8, more preferably an alkyl group C4, even more preferably an n-butyl group.

4. Rubber composition according to any one of the preceding claims, wherein R 1 and R 2 are identical. 5 Rubber composition according to any one of the preceding claims wherein elastomer A is a copolymer of 1,3-diene, methacrylic acid ester and acrylic acid ester. 6 Rubber composition according to any one of the preceding claims wherein the 1,3-diene is 1,3-butadiene or isoprene or a mixture of 1,3-butadiene and isoprene, preferably 1,3-butadiene. 7 Rubber composition according to any one of the preceding claims wherein the monomer units of 1,3-diene represent 40 to 60 mole percent of the monomer units of elastomer A, the monomer units of methacrylic acid ester represent 20 to 45 mole percent of the monomer units of elastomer A and the monomer units of acrylic acid ester represent 10 to less than 30 mole percent of the monomer units of elastomer A. 8 Rubber composition according to any one of the preceding claims wherein the reinforcing filler comprises silica. 9 Rubber composition according to claim 8 in which silica represents more than 50% by mass of the reinforcing filler, preferably more than 80% by mass of the reinforcing filler. 10 Rubber composition according to any one of the preceding claims wherein the reinforcing charge ratio is within a range of 20 to 120 pc, preferably 40 to 100 pc. 2020PAT00112FR 11 Rubber composition according to any one of the preceding claims wherein the crosslinking system is a vulcanization system.

12. Semi-finished product comprising a rubber composition according to any one of the preceding claims.

13. Semi-finished product according to claim 12 characterized in that it is a tire tread.

14. Pneumatics comprising a semi-finished product according to any one of claims 12 to 13 or a rubber composition according to any one of claims 1 to 11. 2020PAT00112FR

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