Rubber composition comprising an estolide as bio-sourced plasticizer

Abstract

The present invention relates to a rubber composition based on at least one elastomer matrix, a reinforcing filler, a vulcanization system and a plasticizing system comprising at least one estolide having a weight-average molar mass (Mw) of less than 5000 g / mol as a biosourced plasticizer.

Description

[0001] Title: Rubber composition comprising an estolide as a bio-sourced plasticizer

[0002] Technical field

[0003] The present invention relates to rubber compositions intended in particular for the manufacture of rubber articles such as tires or semi-finished products for tires. In particular, the invention relates to such rubber compositions, comprising an estolide as plasticizer, which may be entirely or partially biosourced.

[0004] In the current context of energy saving and environmental preservation, manufacturers are constantly looking for new renewable sources that can be used as raw materials for the manufacture of products.

[0005] With this in mind, tire manufacturers are seeking to reduce the impact of tire manufacturing and use on the environment.

[0006] Reducing the hysteresis of rubber compounds used in tire manufacturing has been a long-standing goal of designers in order to obtain tires with reduced rolling resistance to limit fuel consumption.

[0007] Among the levers also available to tire designers is the gradual substitution of materials derived from fossil resources with sustainable materials. Bio-sourced materials constitute a part of these sustainable materials. However, replacing petroleum-based products in tire compositions with bio-sourced products must not be at the expense of safety and expected performance. Thus, bio-sourced products used in tires must be technically as efficient as products prepared from fossil-based raw materials.

[0008] There is a wealth of literature on the replacement of fossil-based liquid plasticizers in rubber compounds for tire manufacturing with bio-based oils derived from vegetable oils such as tall oil, sunflower oil, linseed oil, and castor oil.

[0009] Finding alternatives to the use of plasticizers of fossil origin is therefore a major concern for designers of materials intended for the manufacture of tires, while maintaining the hysteresis of these materials, in order to limit the environmental impacts of tires.

[0010] Thus, the technical problem that arises is to provide a rubber composition for the tire that contributes to reducing its environmental footprint while maintaining its performance, in particular hysteresis. More particularly, an objective of the present invention is to provide a rubber composition comprising an at least partially bio-sourced plasticizer system, while ensuring the maintenance of the hysteresis properties of the composition and therefore the performance of the tire. Presentation of the invention

[0011] The Applicant has discovered, surprisingly, that replacing petroleum-derived oil in a rubber composition with an estolide not only allows the use of a bio-sourced plasticizer, but also a significant reduction in the value of tan delta max at 23°C, a descriptor of the hysteresis of the composition, a property which contributes to rolling resistance.

[0012] Summary of the invention

[0013] The subject of the invention is therefore a rubber composition based on at least one elastomer matrix, a reinforcing filler, a crosslinking system and a plasticizing system, which plasticizing system comprises an estolide having a weight-average molar mass (Mw) of less than 5000 g / mol.

[0014] The invention particularly relates to a rubber composition according to any one of the following embodiments:

[0015] 1. Rubber composition based on at least:

[0016] - an elastomer matrix,

[0017] - 40 to 200 pce of a reinforcing filler,

[0018] - 10 to 140 pce of a plasticizing system comprising at least one estolide with a weight-average molar mass (Mw) of less than 5000g / mol determined by SEC, size exclusion chromatography described in the description,

[0019] - a crosslinking system.

[0020] 2. Composition according to the preceding embodiment in which the elastomer matrix comprises at least one diene elastomer chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.

[0021] 3. Composition according to any one of the preceding embodiments in which the elastomer matrix comprises at least one butadiene elastomer chosen from the group consisting of polybutadienes and butadiene copolymers and mixtures of these elastomers, preferably at least one copolymer of butadiene and styrene.

[0022] 4. Composition according to any one of the preceding embodiments in which the elastomer matrix comprises predominantly at least one butadiene elastomer, preferably at least one copolymer of butadiene and styrene.

[0023] 5. Composition according to any one of the preceding embodiments in which the reinforcing filler comprises silica, carbon black, or a mixture of silica and carbon black.

[0024] 6. Composition according to any one of the preceding embodiments in which the reinforcing filler mainly comprises silica at a rate within a range from 40 phr to 120 phr, preferably from 60 to 120 phr. 7. Composition according to any one of the preceding embodiments in which the rate of the at least one estolide is within a range from 5 to 70 phr, preferably from 10 to 50 phr.

[0025] 8. Composition according to any one of the preceding embodiments in which the plasticizing system comprises from 10 to 100% by weight of at least one estolide, preferably 15 to 70% by weight, relative to the total weight of the plasticizing system.

[0026] 9. Composition according to any one of the preceding embodiments in which the at least one estolide is an estolide of a fatty acid, saturated or unsaturated, linear or branched, Cx to C34, esterified with a fatty alcohol or a dimer diol.

[0027] 10. Composition according to any one of the preceding embodiments in which the at least one estolide is an estolide of a hydroxylated fatty acid, linear or branched, saturated or unsaturated, in C12 to C22, in particular in C16 to C20 and more particularly in Cis.

[0028] 11. Composition according to any one of the preceding embodiments in which the at least one estolide is a ricinoleic acid estolide.

[0029] 12. Composition according to any one of the preceding embodiments in which the estolide is an estolide esterified with a fatty alcohol, saturated or unsaturated, linear or branched, Cx to C34.

[0030] 13. Composition any one of the preceding embodiments in which the estolide is an estolide esterified with a fatty alcohol having a branched aliphatic carbon chain in C12 to C22, in particular in C16 to C20 and more particularly in Cis.

[0031] 14. Composition according to any one of the preceding embodiments in which the estolide is an estolide esterified with isotearyl alcohol.

[0032] 15. Composition according to any one of embodiments 1 to 11 in which the estolide is an estolide esterified with a diol dimer.

[0033] 16. Composition according to any one of embodiments 1 to 11 in which the estolide is an estolide esterified with an alicyclic diol dimer, saturated or unsaturated.

[0034] 17. Composition according to any one of embodiments 1 to 11 in which the estolide is an estolide esterified with a C36 diol dimer, preferably saturated.

[0035] 18. Composition according to any one of the preceding embodiments in which the estolide corresponds to formula I: in which, n is an integer ranging from 1 to 5, preferably from 1 to 3; m is 1 or 2;

[0036] X is a hydrogen atom H or a hydroxyl group -OH;

[0037] RI, identical or different, represent divalent aliphatic radicals, saturated or unsaturated, linear or branched, in C1 - C20, preferably the RI are identical;

[0038] R2, identical or different, are divalent aliphatic radicals, saturated or unsaturated, linear or branched, in C1 - C20, preferably the R2 are identical; the number of carbons in each fatty acid unit being within a range from 8 to 34, preferably from 12 to 22, more preferably 18, when m is 1, R3 represents H (hydrogen atom) or an aliphatic group, linear or branched, saturated or unsaturated, in C12 to C22, in particular in C16 to C20 and more particularly in C18, when m is 2, R3 represents a divalent aliphatic group, cyclic or acyclic, saturated or unsaturated, in particular in C24 to C44, in particular in C32 to C40 and more particularly in C36.

[0039] 19. Composition according to the preceding embodiment in which in formula I, the number of carbons in each fatty acid unit is within a range from 16 to 20, in particular 18.

[0040] 20. Composition according to any one of embodiments 18 to 19 in which in formula I, X represents a hydroxyl group -OH.

[0041] 21. Composition according to any one of embodiments 18 to 20 in which in formula I, m is 1 and R3 represents a saturated aliphatic group branched in C16 to C20 and more particularly in C18.

[0042] 22. Composition according to any one of embodiments 18 to 20 in which in formula I, m is 2 and R3 represents a divalent alicyclic group, saturated or unsaturated, preferably saturated, in C32 to C40 and more particularly in C36.

[0043] 23. Composition according to any one of the preceding embodiments in which the at least one estolide is a ricinoleic acid estolide esterified with isotearyl alcohol or a ricinoleic acid estolide esterified with a saturated C36 alicyclic diol dimer.

[0044] The invention also relates to finished or semi-finished rubber articles comprising a rubber composition in accordance with the invention according to any one of the preceding embodiments.

[0045] The invention also relates to a tire, one of its constituent elements of which comprises a composition according to any one of the preceding embodiments.

[0046] More particularly, the invention also relates to a tire whose tread comprises a composition according to any one of the preceding embodiments.

[0047] Definitions By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomer or rubber.

[0048] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0049] On the other hand, any interval 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., excluding the limits a and b), while any interval 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). In this document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated.

[0050] In this document, the expression "composition based on" means a composition comprising the mixture or the reaction product of the different constituents used, some of these basic constituents being capable of, or intended to, react with each other, at least in part, during the different phases of manufacture of the composition, in particular during its crosslinking or vulcanization. For example, a composition based on an elastomer matrix and sulfur comprises the elastomer matrix and the sulfur before curing, whereas after curing the sulfur has reacted with the elastomer matrix to form sulfur bridges (polysulfides, disulfides, mono-sulfide).

[0051] When a "majority" compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, i.e. it is the one which represents the largest quantity by mass among the compounds of the same type. Preferably, this is the compound which represents, for example, more than 50%, 60%, 70%, 80%, 90%, or even 100% by weight relative to the total weight of the type of compound. Thus, for example, a majority reinforcing filler is the reinforcing filler representing the largest mass relative to the total mass of the reinforcing fillers in the composition. On the contrary, a "minority" compound is a compound which does not represent the largest mass fraction among the compounds of the same type.

[0052] 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. Similarly, the compounds mentioned may also come from the recycling of materials already in use, i.e. they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0053] Detailed description of the invention

[0054] 1.1. Elastomer matrix The rubber composition according to the invention comprises an elastomer matrix, which matrix is ​​usually based on at least one diene elastomer.

[0055] By "diene elastomer" is meant in a known manner one (meaning one or more) elastomers derived at least in part (i.e., a homopolymer or a copolymer) from diene monomers.

[0056] The term diene elastomer capable of being used in the compositions in accordance with the invention is particularly understood to mean:

[0057] (a) - any homopolymer of a conjugated diene monomer having from 4 to 18 carbon atoms;

[0058] (b) - any copolymer of a conjugated diene having from 4 to 18 carbon atoms and at least one other monomer. The other monomer may be ethylene, a vinyl aromatic compound or another diene.

[0059] Suitable conjugated diene is a conjugated diene having 4 to 12 carbon atoms, in particular a 1,3-diene, such as in particular 1,3-butadiene, isoprene, 2,3-di(C1-C5 alkyl)-1,3-butadiene and 1,3-pentadiene, as well as 2,4-hexadiene. 1,3-butadiene and isoprene are particularly suitable conjugated dienes.

[0060] A suitable vinyl aromatic compound is a vinyl aromatic compound having 8 to 20 carbon atoms. Examples of suitable vinyl aromatic compounds are styrene, ortho-, meta-, para-methyl styrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene. Styrene is particularly suitable as a vinyl aromatic compound.

[0061] The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units.

[0062] The diene elastomer may have any microstructure which depends on the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used. The elastomer may be, for example, block, statistical, sequenced, microsequenced, and may be prepared in dispersion or in solution.

[0063] The diene elastomer can be coupled and / or star-shaped or even functionalized with a coupling and / or star-shaped or functionalizing agent.

[0064] The diene elastomer may be simultaneously or alternatively functionalized and comprise at least one functional group. By functional group is meant a group comprising at least one heteroatom chosen from Si, N, S, O, P. Particularly suitable as functional groups are those comprising at least one function such as: silanol, an alkoxysilane, a primary, secondary or tertiary amine, cyclic or not, a thiol, an epoxide. Preferably, the elastomer matrix according to the invention comprises at least one diene elastomer chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers.Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (B IR), isoprene-styrene copolymers (SIR), isoprene-butadiene-styrene copolymers (SBIR), butadiene-acrylonitrile copolymers (NBR), butadiene-styrene-acrylonitrile copolymers (N SB R), ethylene-butadiene copolymers (EBR) and terpolymers of ethylene, butadiene and another conjugated diene monomer, in particular isoprene, myrcene or farnesene, or a mixture of two or more of these compounds.

[0065] The compositions of the invention may contain a single diene elastomer or a mixture of several diene elastomers.

[0066] According to a preferred implementation of the invention, the elastomer matrix comprises at least one butadiene elastomer. This means one or more butadiene elastomers.

[0067] Preferably according to this implementation, the elastomer matrix mainly comprises at least one butadiene elastomer. Preferably again, the rate of butadiene elastomer(s) is from 30 to 100 phr, more preferably from 50 to 100 phr, more preferably from 80 to 100 phr.

[0068] By "butadiene elastomer" is meant, in a known manner, a homopolymer or a copolymer of butadiene, in other words a diene elastomer chosen from the group consisting of polybutadienes (BR), butadiene copolymers as listed above and their mixtures. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). Preferably, the butadiene elastomer is chosen from the group consisting of butadiene-styrene copolymers (SBR) and their mixtures.

[0069] 1.2, Plasticizer System

[0070] The composition according to the invention comprises from 10 to 140 pce of a plasticizing system comprising at least one estolide having a weight-average molar mass Mw of less than 5000 g / mol and preferably within a range varying from 700 to 5000 g / mol, more preferably within a range varying from 700 to 3500 g / mol.

[0071] The weight-average molar mass (Mw) of estolides is measured by SEC (Size Exclusion Chromatography) according to the method described below.

[0072] According to the invention, the term "at least one estolide" means one or more estolides. According to embodiments of the invention, the plasticizer system comprises from 10 to 100% by weight of at least one estolide, preferably 15 to 70% by weight, relative to the total weight of the plasticizer system. The term "at least one estolide" is intended to denote one or more estolides (i.e. a mixture of estolides).

[0073] According to the invention, the rubber composition preferably comprises from 5 to 70 pce, more preferably from 10 to 50 pce of at least one estolide.

[0074] Estolides:

[0075] Estolides are obtained from unsaturated fatty acids and / or saturated fatty acids. Estolides are a class of 100% bio-based esters when the fatty acids are of natural origin. The oligomeric structure of estolides contains repeating fatty acid units, with each fatty acid unit being esterified by another fatty acid unit. WO2012173671A1 describes such compounds.

[0076] Some estolides can be obtained from naturally hydroxylated fatty acids or from fatty acids that have undergone hydroxylation, the hydroxyl function of each unit of a fatty acid is esterified by the acid function of another fatty acid. According to other methods of synthesis, the estolide will be formed by production of a carbocation on the site of unsaturation of an unsaturated fatty acid, followed by a nucleophilic attack on the carbocation by the carboxylic group of another fatty acid. As a starting compound, the fatty acid or its alkyl ester can be used, some of which are commercially available. These methods of synthesis are known and within the reach of those skilled in the art. For example, document WO2012173671A1 describes methods of synthesizing estolides.

[0077] The reader will understand that in order to reduce the environmental impact of the rubber composition according to the invention, by fatty acid is very preferably meant a fatty acid of natural origin, obtained by hydrolysis of vegetable oils, such as, to cite only a few examples, the fatty acids of orange oil, avocado oil, macadamia oil, olive oil, hydrogenated soybean oil, rapeseed oil, jojoba oil, palm oil, castor oil, wheat germ oil, saffron oil, linseed oil, safflower oil, corn oil, pine oil, sunflower oil, coconut oil, peanut oil, grape seed oil, cottonseed oil, macadamia oil and mixtures thereof.

[0078] Examples of naturally occurring fatty acids include:

[0079] - saturated linear fatty acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, lignoceric acid, cerotic acid,

[0080] - branched fatty acids, saturated or unsaturated, are fatty acids having a methyl group attached to the penultimate or antepenultimate carbon atom or several methyl groups distributed along the chain, such as for example isostearic acid, isopalmic acid,

[0081] - linear unsaturated fatty acids, such as linderic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, elaidic acid, gadolenoic acid, eicosapentaenoic acid, docosahexaenoic acid, erucic acid, brassidic acid, arachidonic acid,

[0082] - hydroxylated fatty acids such as ricinoleic acid, hydroxystearic acids.

[0083] According to the invention, the term "fatty acid" is intended to denote a fatty acid, saturated or unsaturated, linear or branched, in Cs to C34, in particular in Cs to C26, in particular in C12 to C22, in particular in C16 to C22. According to preferred embodiments of the invention, the fatty acid is a hydroxylated fatty acid, linear or branched, saturated or unsaturated, in C12 to C22, in particular in C16 to C20 and more particularly in Cis. Preferably again, the fatty acid is ricinoleic acid.

[0084] According to preferred embodiments of the invention, the estolide is an estolide which has undergone ultimate esterification with a saturated or unsaturated, linear or branched C1 to C34 aliphatic alcohol, preferably a fatty alcohol, or a dimer diol, which fatty alcohol and dimer diol are defined below. In the context of the invention, such an esterified estolide is also designated by the name "estolide".

[0085] By "fatty alcohol" is meant, according to the invention, an alcohol obtained by catalytic hydrogenation of a fatty acid, saturated or unsaturated, linear or branched, in Cs to C34, in particular in Cs to C26, in particular in C12 to C22, in particular in C16 to C22 and more particularly in Cis.

[0086] The fatty alcohol may be a linear, saturated or unsaturated fatty alcohol, from Cs to C34, preferably a linear fatty alcohol from Cs to C26, in particular from C12 to C22 and more particularly from Cis, such as, for example, stearyl alcohol, oleyl alcohol and linoleyl alcohol.

[0087] The fatty alcohol may be a branched fatty alcohol. According to the invention, the term "branched fatty alcohol" is intended to denote an alcohol derived from a fatty acid having a methyl group attached to the penultimate or antepenultimate carbon atom or several methyl groups distributed along the chain. These branched fatty alcohols are preferably C12 to C22 and more particularly Cis, like isostearyl alcohol.

[0088] Also, by "dimer diol", is meant according to the invention, a diol produced by catalytic hydrogenation of the acid functions of a dimer dicarboxylic acid, itself obtained by dimerization of a fatty acid, linear or branched, preferably unsaturated, in particular C12 to C22, in particular C16 to C20, and more particularly Cis, like for example oleic acid, linoleic acid and α-linoleic acid, and their mixture. Dimerized fatty acids are commercially available, for example under the name "Pripol" ("Pripol 1013", "Pripol 1009", "Pripol 1017",...) by the company Croda. The dimer diols that can be used in the context of the invention can be synthesized in a conventional manner.

[0089] Dimer diols that can be used in the context of the invention are also commercially available. Examples include the C36 dimer diols marketed under the name "Pripol 2033", "Pripol 2043", "Pripol 2013" by the company Croda. According to embodiments of the invention, the dimer diol derived from a dimerized fatty acid is aliphatic, cyclic or acyclic, saturated or unsaturated. Cyclic is understood to mean a monocyclic or polycyclic dimer diol, i.e. comprising one or more aliphatic rings in its structure. According to particular embodiments of the invention, the dimer diol is alicyclic (aliphatic and cyclic), saturated or unsaturated, at C36, preferably saturated.

[0090] Preferably, according to these embodiments of the invention, the estolide is an estolide which has undergone ultimate esterification with a fatty alcohol in Cx to C26, in particular in C12 to C22 and more particularly in Cis like isostearyl alcohol.

[0091] Alternatively, preferably according to these embodiments of the invention, the estolide is an estolide which has undergone ultimate esterification with a diol dimer, more preferably at C36.

[0092] According to the invention, the at least one estolide is preferably a compound of Formula I:

[0093] Formula I in which, n is an integer ranging from 1 to 5, preferably from 1 to 3; m is 1 or 2,

[0094] X is a hydrogen atom or an -OH group;

[0095] RI, identical or different, represent divalent, saturated or unsaturated, linear or branched aliphatic radicals, C1 - C20, preferably the RI are identical; R2, identical or different, are divalent, saturated or unsaturated, linear or branched aliphatic radicals, C1 - C20, preferably the R2 are identical; the number of carbons in each fatty acid unit being within a range from 8 to 34, preferably from 12 to 22, more preferably from 16 to 20, in particular 18; when m is 1, R3 represents H (hydrogen atom) or a linear or branched, saturated or unsaturated aliphatic group, in Cs-C34, preferably an aliphatic group in Cs to C26, in particular in C12 to C22, in particular in C16 to C20 and more particularly in C18, when m is 2, R3 represents a divalent, cyclic or acyclic, saturated or unsaturated aliphatic group in C24 to C44, in particular in C32 to C40 and more particularly in C36.

[0096] According to variants of the invention, in formula I, at least one of R1 and R2 is an unsaturated, linear or branched, divalent aliphatic radical comprising at least one carbon-carbon double bond. According to preferred variants of the invention, the number of carbons in each fatty acid unit is within a range from 16 to 20, in particular 18. The term "fatty acid unit" means the unit of formula II:

[0097] Formula I

[0098] According to variants of the invention, estolide may be a compound obtained from a hydroxylated fatty acid. According to these variants, in Formula I, X represents an -OH group. As hydroxylated fatty acid, mention may be made of ricinoleic acid or hydroxylated stearic acids.

[0099] According to one of these variants of the invention, the estolide is preferably a compound obtained from ricinoleic acid. Advantageously, such an estolide is obtained from castor oil comprising a mass fraction at least equal to 80% of ricinoleic acid.

[0100] According to variants of the invention, the estolide may be a compound obtained from a fatty acid, hydroxylated or non-hydroxylated, having undergone esterification with an aliphatic alcohol, preferably a fatty alcohol. According to these variants of the invention, R3 is preferably the carbon chain derived from a fatty alcohol and represents a Cs-C34 aliphatic radical, saturated or unsaturated, linear or branched, in particular Cs to C26, in particular C12 to C22, in particular C16 to C20 and more particularly Cis.

[0101] According to variants of the invention, the estolide may be a compound obtained from a fatty acid, hydroxylated or non-hydroxylated, having undergone esterification with a diol dimer. According to these variants of the invention, R3 is preferably the carbon chain resulting from a diol dimer and represents a divalent aliphatic group, cyclic or acyclic, saturated or unsaturated, in C24 to C44, in particular in C32 to C40 and more particularly in C36. More preferably then, R3 represents a divalent cyclic aliphatic group in C36, preferably saturated.

[0102] According to variants of the invention, the estolide is preferably a compound obtained from a hydroxylated fatty acid, preferably ricinoleic acid, having undergone esterification with a branched C12 to C22 and more particularly C18 fatty alcohol, preferably isostearyl alcohol, or with a C36 alicyclic diol dimer, preferably saturated.

[0103] Advantageously, ricinoleic acid is obtained from castor oil.

[0104] Other plasticizers

[0105] According to certain embodiments of the invention, the plasticizer system consists essentially of at least one estolide.

[0106] Thus, according to certain embodiments of the invention, the plasticizing system may comprise one or more other plasticizing compounds usually used in rubber compositions for tires. These other plasticizing compounds may be chosen from plasticizing hydrocarbon resins and plasticizers that are liquid at room temperature (around 23°C) usually used in rubber compositions for tires.

[0107] Examples of hydrocarbon resins that can be used in the context of the invention include those chosen from the group consisting of cyclopentadiene (abbreviated CPD) or dicyclopentadiene (abbreviated DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins (or more generally a Cx to Cio cut), coumarone homopolymer or copolymer resins, rosin esters and mixtures of these resins. Among the above copolymer resins, mention may be made more particularly of those chosen from the group consisting of terpene copolymers, aromatic (D)CPD / C9 copolymer resins, (D)CPD / terpene copolymer resins, (D)CPD / C5 cut copolymer resins, terpene / vinylaromatic copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins.

[0108] The term "terpene" here includes in a known manner in particular the monomers alpha-pinene, beta-pinene and limonene. Suitable C9 monomers include, for example, styrene, phenol, alpha-methyl styrene, ortho-, meta-, para-methyl styrene, vinyl toluene, para-tert-butyl styrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene, vinyl naphthalene, indene, and any vinyl aromatic monomer derived from a C9 cut (or more generally from a Cx to Cio cut).

[0109] Examples of liquid plasticizers that can be used in the context of the invention include those chosen from liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvates) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds.

[0110] The reader will understand that in order to reduce the environmental impact of the rubber composition according to the invention, if at least one other plasticizer is used in the rubber composition, this will preferably be of a renewable nature, in particular of bio-sourced origin.

[0111] 1.3, Reinforcing charge

[0112] The rubber composition of the invention comprises from 40 to 200 phr of total reinforcing filler. The rubber composition of the invention may comprise one or more reinforcing fillers.

[0113] Any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition that can be used in particular for the manufacture of tires, can be used, for example an organic filler such as carbon black, an inorganic filler such as silica or a mixture of these two types of fillers.

[0114] Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the 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 the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. Carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a “masterbatch” (see, for example, applications WO97 / 36724-A2 or W099 / 16600-A1).

[0115] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiCL) or of the aluminous type, in particular alumina (AI2O3). 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 CTAB specific surface area, both of less than 450 m 2 / g, preferably within a range of 30 to 400 m 2 / g, especially from 60 to 300 m 2 / g.

[0116] 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 and are commercially available. Examples include 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, 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.

[0117] The physical state in which the reinforcing inorganic filler is presented is indifferent, whether in the form of powder, microbeads, granules, or even beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular silicas as described above.

[0118] Those skilled in the art will understand that, as a replacement for the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or else has functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. By way of example, mention may be made of carbon blacks partially or completely covered with silica, or carbon blacks modified with silica, such as, without limitation, the “Ecoblack®” type fillers of the CRX2000 series or the “CRX4000” series from Cabot Corporation.

[0119] The person skilled in the art will be able to adapt the total reinforcing filler rate and its nature according to the use concerned, in particular according to the type of tire concerned or the type of composition of the tire. The total reinforcing filler rate is within a range from 40 to 200 pce, more preferably from 45 to 180 pce, and even more preferably from 50 to 160 pce; the optimum being, in a known manner, different according to the particular applications targeted.

[0120] According to another particular embodiment of the invention, the reinforcing filler is predominantly an inorganic reinforcing filler (preferably silica), preferably it comprises more than 50% by weight of an inorganic reinforcing filler such as silica relative to the total weight of the reinforcing filler. According to this embodiment, the inorganic filler is preferably used at a rate within a range of 40 to 160 phr, preferably 40 to 140 phr, more preferably 60 to 120 phr. Optionally according to this embodiment, the reinforcing filler also comprises carbon black. According to this option, the carbon black is used at a rate of less than or equal to 20 phr, more preferably less than or equal to 10 phr (for example the carbon black rate may be within a range of 0.5 to 20 phr, in particular 1 to 10 phr).Within 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 the reinforcing inorganic filler.

[0121] 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 NF ISO 5794-1 standard, 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],

[0122] For inorganic fillers such as silica, for example, the CTAB specific surface area values ​​were determined according to standard NF ISO 5794-1, annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0123] To couple the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a well-known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure sufficient interaction, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer. Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”.More preferably, the organosilane is a polysulfurized organosilane.

[0124] Of course, mixtures of the coupling agents described above could also be used.

[0125] The content of coupling agent in the composition of the invention is advantageously less than or equal to 30 phr, it being understood that it is generally desirable to use as little as possible. Typically the level of coupling agent represents from 0.5% to 15% by weight relative to the quantity of reinforcing inorganic filler. This level is easily adjusted by a person skilled in the art according to the level of reinforcing inorganic filler used in the composition of the invention.

[0126] 1.4, Crosslinking system

[0127] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0128] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0129] Sulfur is used at a preferential rate of between 0.5 and 12 pce, preferably 1 to 10 pce, more preferably 1 to 5 pce. The vulcanization accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably 0.5 to 5.0 pce.

[0130] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0131] I.5, Miscellaneous additives

[0132] The rubber compositions in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions for tires, such as, for example, fillers (other than those mentioned above), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described, for example, in application WO 02 / 10269).

[0133] II. Preparation of rubber compositions

[0134] The rubber compositions of the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first phase of thermomechanical working or kneading (so-called "non-productive" phase) at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C for a duration generally of between 2 and 10 minutes; followed by a second phase of mechanical working (so-called "productive" phase) down to a lower temperature, typically below 120°C, for example between 40°C and 100°C, a finishing phase during which the crosslinking system is incorporated, and the whole is then mixed for a few minutes, for example between 5 and 15 minutes.

[0135] The process for preparing such compositions therefore consists, for example, in incorporating into the elastomers, in particular the vinylaromatic diene elastomer, during the first stage (called "non-productive"), the reinforcing filler, the plasticizing system and any other ingredients of the composition with the exception of the crosslinking system, by thermomechanically mixing the whole (for example in one or more times), until a maximum temperature of between 110°C and 190°C is reached; then in cooling the whole to a temperature below 100°C; then in order to incorporate, during the second stage (called "productive"), the crosslinking system and mix the whole to a maximum temperature below 110°C.

[0136] The final composition thus obtained can then be calendered, for example in the form of a sheet, a plate in particular for characterization in the laboratory, or even extruded, for example to form a rubber profile used for the manufacture of a tire.

[0137] The invention relates to the rubber compositions, rubber articles, tires and semi-finished products for tires previously described, both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization). III, Tire of the invention

[0138] The rubber composition according to the invention can be used in different parts of the tire, in particular in the crown, the carcass, the bead area, the sidewall area and the tread (including in particular the tread underlay).

[0139] The above-mentioned 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.

[0140] EXAMPLES OF CARRYING OUT THE INVENTION

[0141] Measures and tests used

[0142] Size exclusion chromatography

[0143] The SEC (Size Exclusion Chromatography) technique separates macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0144] Although not an absolute method, SEC allows us to understand the distribution of molar masses of a polymer. From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined via a so-called MOORE calibration.

[0145] Operating mode

[0146] The number-average molar mass (Mn), the weight-average molar mass (Mw) of the constituents usable in the compositions in accordance with the invention, are determined in a known manner, by conventional size exclusion chromatography (SEC: Size Exclusion Chromatography) with RI detection and PS (Polystyrene) calibration. The PS standards are from the “PSS-kitrll” kit from PSS-Polymers.

[0147] To determine the average molar masses, the sample solution at 1.5 g / l, previously prepared and filtered through a 0.45 pm PTFE filter, is used and injected into the chromatographic system. The equipment used is a “WATERS alliance e2695” chromatographic chain with a “RI 410 Waters” detector. The elution solvent is tetrahydrofuran, the flow rate is 1 mL.min-1, the system temperature is 35°C and the analysis time is 50 min. Four AGILENT columns are used (2 PLGEL 5 pm MIXED-D and 2 PLGEL 3 pm MIXED-E). The injected volume of the sample solution is 100 pL.

[0148] The software for processing chromatographic data is the WATERS “Empower” system. Differential scanning calorimetry

[0149] The glass transition temperatures (Tg) of elastomers are determined using a differential scanning calorimeter, according to ASTM D3418 (1999).

[0150] Hysteresis:

[0151] The deformation hysteresis is measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of vulcanized composition (cylindrical specimen 4 mm thick and 400 mm long) is recorded. 2 section), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under normal temperature conditions (23°C) according to standard ASTM D 1349-99.

[0152] A strain amplitude sweep is carried out from 0.1% to 100% peak-peak (forward cycle), then from 100% to 0.1% peak-peak (return cycle). The result used is the loss factor tan(ô). For the return cycle, the maximum value of tan ô observed, noted tan ô max, is indicated. This value is representative of the hysteresis of the material and in this case gives the trend in rolling resistance: the lower the value of tan ô max, the lower the hysteresis and consequently the rolling resistance. In the examples, the results are given on a base of 100.

[0153] Plasticizers

[0154] Bio-based plasticizers based on ricinoleic acid estolides were obtained according to the following protocols:

[0155] A - Ricinoleic acid esterified with isostearyl alcohol (Oil No. 1)

[0156] Reaction scheme (Oil No. 1)

[0157] The plasticizer based on ricinoleic acid estolide was obtained according to the following protocol: Protocol

[0158] Obtaining the esterified estolide was carried out in four steps. The first consisted of synthesizing an estolide with a well-defined structure, between 2 and 4 chains of ricinoleic acid units. The second step consisted of distilling the excess acid present in the medium using molecular distillation. The esterification of the acid functions available on the estolide was then carried out with an excess of isostearyl alcohol. Finally, the last step consisted of distilling the excess unreacted alcohol.

[0159] Step 1: Synthesis of the oligomer

[0160] Operating mode

[0161] Stirred batch reactor

[0162] Conditions: 180°C / 600mbar / 14h

[0163] Analytical monitoring: SEC (PS equivalent)

[0164] Step 2: molecular distillation known as "short path"

[0165] Terms :

[0166] Temp, trap: -22°C

[0167] Addition pump speed: 230mL / h

[0168] Temp, double jacket: 200°C

[0169] Vacuum: 5.10-2inbar

[0170] Analytical monitoring: SEC (PS equivalent)

[0171] Step 3: esterification of the acid functions

[0172] Addition of 3 molar eq. of isostearyl alcohol

[0173] Operating mode

[0174] Stirred batch reactor

[0175] Conditions: 160°C / under vacuum to distill the water formed during the reaction

[0176] Analytical monitoring: Acid index according to standard NF EN ISO 660 and SEC (Equivalent PS)

[0177] Step 4: Distillation of excess alcohol, known as "short-path"

[0178] Terms :

[0179] Temp, trap: -22°C

[0180] Addition pump speed: 230mL / h

[0181] Temp, double jacket: 200°C

[0182] Vacuum: 8.7.10-2mbar

[0183] Analytical monitoring: SEC (PS equivalent)

[0184] B - Ricinoleic acid esterified with a C36 diol dimer (Oil No. 2)

[0185] Reaction diagram (Oil No. 2)

[0186] Protocol

[0187] The production of esterified estolide was carried out in a single step. It is a polycondensation reaction of methyl ricinoleate produced from castor oil and the diol "Pripol 2033".

[0188] Operating mode

[0189] Stirred batch reactor

[0190] Conditions: 180°C / max vacuum / 3 Oh

[0191] Catalysis: lwt.% Ti(BuO)4

[0192] Distillation of the MeOH formed during the reaction

[0193] Analytical monitoring: SEC (PS equivalent)

[0194] The table below gives the weight-average molar mass (Mw) and glass transition temperature (Tg) characteristics of the two bio-sourced oils in accordance with the invention in comparison with the non-bio-sourced oil (MES Oil).

[0195] Table 1:

[0196] Compositions

[0197] The so-called reference composition T1 is presented in the table below and it includes a TDAE oil which is of fossil origin. Another reference composition T2 is used comprising an oleic sunflower oil, therefore biosourced, already widely described as a plasticizer for rubber compositions for tires.

[0198] It should be noted that compositions C1 and C2, in accordance with the present invention, are formulated so as to be at the same volume dilution in oil (%v) as the control compositions T1 and T2.

[0199] The compositions are as follows (in parts). Table 2

[0200] (1) SBR functionalized with silanol at the chain end, 27% by weight of styrene and 24% mol / BR of vinyl, Tg of -48°C;

[0201] (2) ASTM Black “N234” from CABOT Company

[0202] (3) Silica “ZeosiH 165MP” from the company SOLVAY

[0203] (4) “ESCOREZ 5600” resin from EXXON MOBIL

[0204] (5) Silane “SI69” from the company EVONIK

[0205] (6) Diphenyl guanidine “DPG” from the company AKROCHEM

[0206] (7) Antioxidant “Santoflex 6PPD” from the company FLEXSYS

[0207] (8) TMQ “Naugard Q” antioxidant from CHEMTURA

[0208] (9) “Redezon PWM 43” wax from REPSOL

[0209] (10) “Vivatec 500” oil from BRITISH PETROLEUM

[0210] (11) Oleic sunflower oil from CARGILL

[0211] (12) Oil No. 1: Ricinoleic acid esterified with isostearyl alcohol

[0212] (13) Oil No. 2: Ricinoleic acid estolide esterified by an alicyclic diol dimer in Cas

[0213] (14) Industrial grade zinc oxide - UMICORE company

[0214] (15) Stearin “Pristerene 4931” from the company UNIQUEMA

[0215] (16) Cyclohexyl-benzothiazyl sulfenamide CBS accelerator from AKROCHEM

[0216] Preparation of the compositions

[0217] The rubber compositions, the formulation details of which are given in Table 2, were prepared as follows: The elastomer matrix is ​​introduced into an internal mixer (final filling rate: approximately 70% by volume and paddle speed 60 rpm), with an initial tank temperature of approximately 70°C. When the temperature reaches 90°C, the carbon black, silica and silane are introduced. Then, when the temperature reaches 120°C, the plasticizer and resin are introduced, followed by the rest of the additives. Thermomechanical work (non-productive phase) is then carried out in one step, lasting a total of approximately 3 to 4 minutes, until a maximum "fall" temperature of over 140°C is reached.The resulting mixture is recovered, cooled and then the sulphur and vulcanisation accelerators are added to a mixer (homo-finisher) at 30°C, mixing everything (productive phase) for an appropriate time (for example around ten minutes).

[0218] The compositions thus obtained are then calendered either in the form of plates (thickness 2 to 3 mm) or thin sheets of rubber and vulcanized to their optimum at a temperature of 150°C for the measurements of their physical and dynamic properties which are shown in table 3.

[0219] Results

[0220] Table 3

[0221] Reading the results obtained, it can be said that the compositions in accordance with the invention unexpectedly make it possible to improve the hysteretic properties compared to the control composition T1 comprising an oil of fossil origin usually used in rubber compositions for tires. Indeed, a significant decrease in the relative value of Tan ô Max back to 23°C is observed for compositions C1 and C2, which indicates a decrease in hysteresis compared to composition TL.

[0222] Furthermore and surprisingly, the two compositions according to the invention C1 and C2 comprising a bio-sourced plasticizer also make it possible to improve the hysteresis properties compared to the control composition T2 comprising a bio-sourced oil known as a plasticizer for rubber compositions for tires. Indeed, a significant decrease in the relative value of Tan ô Max back to 23°C is observed for compositions C1 and C2, which indicates a decrease in hysteresis compared to composition T2.

Claims

Claims 1. Rubber composition based on at least: - an elastomer matrix, - 40 to 200 pce of a reinforcing filler, - 10 to 140 pce of a plasticizing system comprising at least one estolide with a weight-average molar mass (Mw) of less than 5000g / mol determined by SEC, size exclusion chromatography described in the description, - a crosslinking system.

2. Composition according to claim 1 in which the elastomer matrix comprises at least one butadiene elastomer chosen from the group consisting of polybutadienes and copolymers of butadiene and styrene and their mixtures, preferably the butadiene elastomer is chosen from copolymers of butadiene and styrene and their mixtures.

3. Composition according to any one of the preceding claims in which the elastomer matrix predominantly comprises at least one butadiene elastomer chosen from the group consisting of polybutadienes and copolymers of butadiene and styrene and their mixtures, preferably the butadiene elastomer is chosen from copolymers of butadiene and styrene and their mixtures.

4. Composition according to any one of the preceding claims in which the reinforcing filler mainly comprises silica at a rate in a range from 40 phr to 120 phr, preferably from 60 to 120 phr.

5. Composition according to any one of the preceding claims in which the level of at least one estolide is within a range from 5 to 70 pce, preferably from 10 to 50 pce.

6. Composition according to any one of the preceding claims in which the at least one estolide is a linear or branched, saturated or unsaturated, C12 to C22, in particular C16 to C20 and more particularly C18, hydroxylated fatty acid estolide, preferably ricinoleic acid.

7. Composition according to any one of the preceding claims in which the estolide is an estolide esterified with a fatty alcohol, saturated or unsaturated, linear or branched, Cs to C34.

8. Composition according to any one of the preceding claims in which the estolide is an estolide esterified with a fatty alcohol having a branched aliphatic carbon chain in C12 to C22, in particular in C16 to C20 and more particularly in C18, preferably the estolide is an estolide esterified with isostearyl alcohol.

9. Composition according to any one of claims 1 to 6 in which the estolide is an estolide esterified with a dimer diol.

10. Composition according to the preceding claim in which the diol dimer is an alicyclic, saturated or unsaturated diol dimer.

11. Composition according to claim 9 or 10 in which the dimer diol is a C36 dimer diol, preferably saturated.

12. Composition according to any one of the preceding claims in which the estolide corresponds to formula I: Formula I in which, n is an integer ranging from 1 to 5, preferably from 1 to 3; m is 1 or 2; X is a hydrogen atom H or a hydroxyl group -OH; RI, identical or different, represent divalent aliphatic radicals, saturated or unsaturated, linear or branched, in C1 - C20, preferably the RI are identical; R2, identical or different, are divalent aliphatic radicals, saturated or unsaturated, linear or branched, in C1 - C20, preferably the R2 are identical; the number of carbons in each fatty acid unit being within a range from 8 to 34, preferably from 12 to 22, more preferably from 16 to 20, more preferably 18, when m is 1, R3 represents H (hydrogen atom) or a linear or branched, saturated or unsaturated aliphatic group, in Cs-C34, preferably in Cs to C26, more preferably in C12 to C22, in particular in C16 to C20 and more particularly in Cis, when m is 2, R3 represents a divalent, cyclic or acyclic, saturated or unsaturated aliphatic group, preferably in C24 to C44, in particular in C32 to C40 and more particularly in C36.

13. Finished or semi-finished rubber article comprising a composition according to any one of claims 1 to 12.

14. Tire comprising a composition according to any one of claims 1 to 12.

15. Tire according to the preceding claim, the tread of which comprises a composition according to any one of claims 1 to 12.

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