Polymer composition comprising a mixture of thermoplastic elastomers.

Abstract

The invention relates to a polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer, the first thermoplastic being a TPE11 block thermoplastic elastomer of formula ABA, wherein A is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B is a diene elastomer block comprising more than 95% by mass of diene units relative to the mass of the diene elastomer block, or a TPE12 block thermoplastic elastomer of formula A'-B'-A', wherein A' is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B' is a statistical copolymer elastomer block comprising diene units and vinylaromatic units, or alternatively a mixture of the two TPE11 and TPE12 block thermoplastic elastomers, the second thermoplastic elastomer comprising at least one polyether elastomer block and at least one thermoplastic block, TP block,which block TP has a melting temperature, Tf, in the range of 130°C to 180°C. The invention also relates to a tire comprising such a composition in all or part of its tread.

Description

Title of the invention: Polymer composition comprising a mixture of thermoplastic elastomers. technical field

[0001] The present invention relates to a polymer composition comprising thermoplastic elastomers. Previous technique

[0002] In the field of motor vehicle tires, the Applicant has previously developed rubber compositions comprising at least one thermoplastic elastomer. These tires offer a very good compromise between grip and rolling resistance performance, as well as good road handling.

[0003] Thermoplastic elastomers (or TPEs) are elastomers of great interest in many fields due to their combined properties, linked on the one hand to the flexible elastomer block and on the other hand to the rigid thermoplastic block. Furthermore, the bonding of the rigid thermoplastic blocks gives the material the behavior of a cross-linked elastomer. Indeed, the rigid nodules, formed by areas where the thermoplastic blocks bond together, act as cross-linking nodes. The material is therefore rigid and does not flow. However, when the temperature is raised above the glass transition temperature or the melting temperature of the rigid blocks, the polymer will flow, allowing the material to be shaped. The material regains its rigidity when the temperature returns to the operating temperature, which is lower than the glass transition temperature (Tg) of the thermoplastic blocks.This characteristic of very small businesses implies a very wide range of potential applications.

[0004] Among the most widespread thermoplastic elastomers are styrene block copolymers, known as styrene TPEs. The glass transition temperature (Tg) of polystyrene blocks is around 80°C to 100°C, depending on the size of the polystyrene blocks. For some applications, the Tg value of polystyrene blocks is insufficient. Indeed, this value does not allow for the use of these TPEs in the manufacture of certain objects subjected, in particular, to specific operating conditions where temperatures exceed 100°C.

[0005] As other styrenic TPEs, copolymers with poly(α-methylstyrene) blocks instead of polystyrene blocks have been proposed because they have the advantage of exhibiting high thermal resistance attributed to the high Tg of approximately 150-170°C of the rigid poly(α-methylstyrene) blocks. These thermoplastic elastomers are extensively described in the state of the art, in academic literature or in patent documentation such as document WO2007112232A2 or document FR2243214.

[0006] The Applicant has previously developed compositions for tires, in particular for tire tread, comprising a thermoplastic elastomer, as in document WO2012152686 or more recently, in document WO2023202915A1 describing a TPE matrix comprising a triblock TPE having a diene elastomer block and two thermoplastic blocks comprising α-methylstyrene units.

[0007] A constant objective of tire manufacturers is to improve the properties of the tread, which must meet a large number of technical requirements, notably that of having a very good level of road handling on motor vehicles. To improve road handling, as is known, a certain level of tread rigidity is sought.

[0008] It is therefore desirable that a TPE composition comprising rigid blocks based on α-methylstyrene exhibit good rigidity, particularly in the manufacture of tires. To this same end, improvements in the processability and shaping of such a TPE composition are constantly being sought.

[0009] It is generally known that the use of plasticizers in combination with TPEs, in particular TPEs comprising α-methylstyrene blocks, improves their processability and shaping, as indicated in document WO2012152686 or in document WO2015 / 113966. However, it is also accepted that the use of plasticizers in a TPE composition reduces its rigidity.

[0010] An objective of the present invention is to improve the processability of a thermoplastic block TPE rubber composition comprising α-methylstyrene units, while improving or at least maintaining the rigidity of the composition. Description of the invention

[0011] This objective is achieved in that the Inventors discovered during their research, in a surprising way, that a specific rubber composition comprising a first block TPE, comprising a flexible diene block and rigid thermoplastic blocks comprising α-methylstyrene units, and a second block TPE comprising at least one polyether elastomer block and at least one thermoplastic TP block, which thermoplastic TP block has a melting temperature, Tf, in the range of 130°C to 180°C, exhibited improved processability, without this being at the expense of the rigidity of the composition.

[0012] These significant improvements in properties make it possible to achieve a very good level of compromise between processability of a TPE composition and road behavior of tires having a tread based on such a TPE composition.

[0013] Thus, a first object of the invention is a polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer, - which first thermoplastic is

[0014] a TPE11 block thermoplastic elastomer of formula ABA, in which A is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B is a diene elastomer block comprising more than 95% by mass of diene units relative to the mass of the diene elastomer block, or

[0015] a TPE12 block thermoplastic elastomer of formula A'-B'-A', wherein A' is a thermoplastic block comprising predominantly α-methylstyrene units by mole and B' is a statistical copolymer elastomer block comprising diene units and vinylaromatic units, or

[0016] a mixture of the two block thermoplastic elastomers TPE11 and TPE12, - which second thermoplastic elastomer comprises at least one polyether elastomer block and at least one thermoplastic block, block TP, which block TP has a melting temperature, Tf, in the range of 130°C to 190°C.

[0017] The invention also relates to finished or semi-finished products comprising a polymer composition according to the invention and intended for the manufacture of tires, in particular, a tire tread comprising such a composition.

[0018] The invention also relates to a tire comprising a polymer composition according to the invention in all or part of its tread. Summary of the invention

[0019] The invention, described in more detail below, relates to at least one of the embodiments listed in the following points:

[0020] 1. polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer, - which first thermoplastic is

[0021] a TPE11 block thermoplastic elastomer of formula ABA, wherein A is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B is a diene elastomer block comprising more than 95% by mass of diene units relative to the mass of the diene elastomer block, or

[0022] a TPE12 block thermoplastic elastomer of formula A'-B'-A', wherein A' is a thermoplastic block comprising predominantly α-methylstyrene units by mole and B' is a statistical copolymer elastomer block comprising diene units and vinylaromatic units, or

[0023] a mixture of the two block thermoplastic elastomers TPE11 and TPE12, - which second thermoplastic elastomer comprises at least one polyether elastomer block and at least one thermoplastic block, block TP, which block TP has a melting temperature, Tf, in the range of 130°C to 190°C.

[0024] 2. Composition according to embodiment 1, in which the thermoplastic blocks A and A' independently comprise more than 95% by mole of α-methylstyrene units.

[0025] 3. Composition according to embodiment 1 or 2 in which the thermoplastic blocks A and A' comprise styrene units independently of each other.

[0026] 4. Composition according to any one of embodiments 1 to 2 in which the blocks Thermoplastics A and A' are independently of each other homopolymers of α-methylstyrene.

[0027] 5. Composition according to any one of the preceding embodiments in which the thermoplastic blocks A represent at least 10% by mass relative to the mass of the thermoplastic block elastomer TPE11, preferably from 10 to 45% by mass, preferably again from 10% to 40% by mass, and independently the thermoplastic blocks A' represent at least 10% by mass relative to the mass of the thermoplastic block elastomer TPE12, preferably from 10 to 45% by mass and preferably again from 10% to 40% by mass.

[0028] 6. Composition according to any one of the preceding embodiments in which the elastomer block B comprises from 0 to less than 5% by mass of units of one or more vinylaromatic monomers.

[0029] 7. Composition according to embodiment 6 in which the monomer units vinylaromatics of block B, are chosen from styrene units, α-methylstyrene units and their mixture.

[0030] 8. Composition according to any one of the preceding embodiments in which The elastomer block B mainly comprises 1,3-butadiene units, preferably block B is a polybutadiene block (BR).

[0031] 9. Composition according to any one of the preceding embodiments in which The elastomer block B' comprises more than 5% by mass to less than 45% by mass, preferably more than 10% by mass to less than 40% by mass of vinylaromatic units, relative to the mass of block B', the vinylaromatic units preferably being styrene units.

[0032] 10. Composition according to any one of the preceding embodiments in which the Elastomer block B' comprises units of 1,3-butadiene and units of styrene.

[0033] 11. Composition according to any one of the preceding embodiments in which the B' elastomer block is a random copolymer of 1,3-butadiene and styrene.

[0034] 12. Composition according to any one of the preceding embodiments, in which the thermoplastic block(s) of the second thermoplastic elastomer are chosen from the group consisting of polyamides, preferably the thermoplastic block(s) of the second thermoplastic elastomer are chosen from the group consisting of polyamides of type PA6, PAU PA12, PA4.12, PA4.14, PA4.18, PA6.10, PA6.12, PA6.14, PA6.18, PA9.12, PA10.10, PA10.12, PA10.14, PA10.18 and their mixtures, preferably the polyamide blocks are chosen from the group consisting of polyamides of type PA6, PAU, PA12 and their mixtures.

[0035] 13. Composition according to any one of the preceding embodiments, in which the mass fraction of the thermoplastic block (TP) in the second thermoplastic elastomer is in the range of 15% to 60%, preferably 20% to 50%.

[0036] 14. Composition according to any one of the preceding embodiments, in which The polyether elastomer block(s) of the second thermoplastic elastomer are selected from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycols (PEG), polypropylene ether glycol (PPG), polyhexamethylene ether glycol, polytrimethylene ether glycol (PO3G), poly(3-alkyltetrahydrofuran), and mixtures thereof, preferably from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycols (PEG) and mixtures thereof.

[0037] 15. Composition according to any one of the preceding embodiments, in which the second thermoplastic elastomer is chosen from the group consisting of polyether and polyamide block copolymers (PEBA).

[0038] 16. Composition according to any one of the preceding embodiments, in which the thermoplastic block (TP) of the second thermoplastic elastomer has a Tf in a range preferably from 130°C to 180°C.

[0039] 17. Composition according to any one of the preceding embodiments, in which the the rate of the first thermoplastic elastomer in the composition is in the range of 50 to 96 parts per annum, preferably 60 to 80 parts per annum.

[0040] 18. Composition according to any one of the preceding embodiments, in which the The proportion of the second thermoplastic elastomer in the composition is in a range of 4 to 50 parts per cent.

[0041] 19. Composition according to any one of the preceding embodiments, which the composition further comprises an α-methylstyrene homopolymer in a mass proportion ranging from 5 to 45% by mass relative to the total mass of the composition.

[0042] 20. Composition according to any one of the preceding embodiments comprising at less one component selected from non-thermoplastic elastomers, reinforcing fillers selected from carbon blacks and other reinforcing fillers, organic and inorganic of siliceous type in particular silica, as well as mixtures of these fillers, elastomer / filler coupling agents, non-reinforcing fillers, processing agents, stabilizers, plasticizers, pigments, antioxidants, anti-fatigue agents, anti-ozonating waxes, adhesion promoters, reinforcing resins, crosslinking systems based on sulfur and / or peroxide and / or bismaleimides, crosslinking activators including zinc monoxide and stearic acid, guanidic derivatives, extending oils, silica coating agents.

[0043] 21. Finished or semi-finished product intended for the manufacture of tires comprising a composition according to any one of the previous designs.

[0044] 22. A tire comprising a tread, which tire comprises a composition according to any one of the realizations 1 to 20 in all or part of its tread. Definitions

[0045] In the present, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0046] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain within the limits a and b (i.e. bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e. including the strict bounds a and b).

[0047] In this description, "part per percent of elastomer" or "pce" means the mass portion of a constituent per 100 mass portions of the elastomer(s), i.e., of the total mass of the elastomer(s), whether thermoplastic or non-thermoplastic, in the composition. Thus, a constituent at 60 pce will mean, for example, 60 g of that constituent per 100 g of elastomer.

[0048] Poly(α-methylstyrene) is commonly understood to be a homopolymer of α-methylstyrene.

[0049] In the present description, "X units" (or "X motifs") or units of the X monomer of a polymer mean the monomer units that result from the polymerization of the X monomer. Thus, "α-methylstyrene units" are the units resulting from the polymerization of the α-methylstyrene monomer.

[0050] The carbon-containing compounds mentioned in the description may be of fossil origin or bio-based. 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 previously used materials; that is, 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, monomers, polymers, etc. Detailed description of the invention

[0051] The polymer composition according to the invention comprises a first thermoplastic elastomer and a second thermoplastic elastomer. The first thermoplastic elastomer (TPE1)

[0052] The first TPE useful for the needs of the invention is chosen from: a triblock thermoplastic elastomer (TPE 11), of formula ABA with two rigid thermoplastic segments A comprising α-methylstyrene units connected by a flexible segment B made of a diene elastomer, a triblock thermoplastic elastomer (TPE12) of formula A'-B'-A' with two rigid thermoplastic segments A' comprising α-methylstyrene units connected by a flexible segment B' made of a statistical copolymer elastomer comprising diene units and vinylaromatic units, and a mixture of TPE11 and TPE12.

[0053] The number-average molar mass (denoted Mn) of the first TPE of the invention is preferably between 60,000 and 800,000 g / mol, more preferably between 80,000 and 600,000 g / mol. Below the indicated minimums, the cohesion between the TPE chains may be affected; furthermore, an increase in the operating temperature may affect the mechanical properties, particularly the fracture properties. Moreover, an excessively high Mn mass can be detrimental to processing. Thus, it has been found that a value in the range of 80,000 to 400,000 g / mol is particularly well-suited, especially for using the TPE in a tire compound. An Mn in the range of 100,000 to 300,000 g / mol is even more preferable.

[0054] For TPEs, the number-average molar mass (Mn) of TPE telatomer is determined by size-exclusion chromatography (SEC) in a manner known to those skilled in the art using a calibration curve made from standard polybutadienes.

[0055] The value of the polymolecularity index Ip (reminder: Ip = Mw / Mn with Mw being the weight-average molar mass and Mn the number-average molar mass) of the TPE is preference less than 3, more preferentially less than 2, even more preferentially less than 1.5.

[0056] As is known, TPEs exhibit two peaks of glass transition temperature (Tg), the lower temperature being relative to the elastomer part of the TPE, and the higher temperature being relative to the thermoplastic part of the TPE.

[0057] The TPE 11 triblock thermoplastic elastomer of formula ABA

[0058] The triblock thermoplastic elastomer denoted TPE11 useful for implementing the present invention is of formula ABA, in which A is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B is a diene elastomer block comprising more than 95% by mass of diene units relative to the mass of the diene elastomer block. The diene elastomer block "B" or B block

[0059] Block B of the first TPE, for the purposes of the invention, is a diene elastomer. A diene elastomer is defined as an elastomer derived at least in part (i.e., a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not). Block B generally has a Tg below 0°C and very preferably below -10°C. A Tg value above these values ​​may reduce the performance of the composition when used at very low temperatures. Preferably, the Tg of the elastomer block of the TPE is above -100°C. The essential characteristic of block B is that it contains predominantly diene units by mass. In other words, the diene units of block B represent the highest weight fraction of the constituent units of block B.

[0060] Preferably, block B is any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 15 carbon atoms, or a copolymer obtained by copolymerization of one or more conjugated dienes having 4 to 15 carbon atoms between them or possibly by copolymerization with one or more vinylaromatic monomers having 8 to 20 carbon atoms.

[0061] Suitable conjugated dienes for use according to the invention include, in particular, 1,3-dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(alkyl in Ci-C5)-1,3-butadiene such as, for example, 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, phenyl-1,3-butadiene, 1,3-pentadiene.

[0062] More preferably, block B comprises 1,3-diene monomer units having 4 to 12 carbon atoms. Even more preferably, block B comprises 1,3-butadiene units.

[0063] Block B is preferably a polybutadiene (BR) or a 1,3-butadiene copolymer, in particular a copolymer of 1,3-butadiene and a vinylaromatic monomer.

[0064] Suitable vinylaromatic monomers include styrene, α-methylstyrene, ortho-meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tert-butylstyrene, methoxystyrenes, vinylmesitylene, divinylbenzene, and vinylnaphthalene. The vinylaromatic monomer is preferably styrene or α-methylstyrene, more preferably α-methylstyrene.

[0065] According to a particularly preferred embodiment of the invention, the elastomer block B comprises predominantly by mass units of 1,3-butadiene, preferably block B is a polybutadiene block.

[0066] According to one embodiment of the invention, the elastomer block B comprises from 0 to less than 5% by mass of units of one or more vinylaromatic monomers. According to this preferred embodiment of the invention, the units of a vinylaromatic monomer in the elastomer block B are advantageously chosen from styrene and α-methylstyrene, more advantageously α-methylstyrene.

[0067] Preferably, the elastomer block B has a number-average molar mass (Mn) of at least 25,000 g / mol, preferably at least 35,000 g / mol and at most 350,000 g / mol, preferably at most 250,000 g / mol, so as to impart good elastomeric properties and satisfactory mechanical strength to the thermoplastic elastomers. The number-average molar mass of the elastomer block B of the thermoplastic elastomer can be determined by size-exclusion chromatography in a manner known to those skilled in the art using a polybutadiene standard curve. The thermoplastic block "A" or block A

[0068] The first thermoplastic elastomer useful for the purposes of the invention comprises two terminal thermoplastic, or rigid, blocks comprising α-methylstyrene units.

[0069] Preferably, the thermoplastic blocks A each have a number-average molar mass (“Mn”) of at least 5,000 g / mol, preferably at least 7,000 g / mol, and at most 100,000 g / mol, preferably at most 50,000 g / mol. The number-average molar mass of the thermoplastic blocks A can be determined by size-exclusion chromatography in a manner known to those skilled in the art and is expressed here relative to polystyrene standards.

[0070] According to the invention, the thermoplastic blocks A comprise predominantly by mole of α-methylstyrene units in order to provide good thermal resistance to the thermoplastic elastomer, as well as to the composition according to the invention. In other words, the α-methylstyrene units of block A represent the highest mole fraction of the constituent units of block A. Thermoplastic block A preferably comprises more than 95 mole percent of α-methylstyrene units, a percentage expressed relative to all the monomer units constituting block A.

[0071] When the thermoplastic blocks A further comprise units derived from at least one other monomer, this monomer may be vinylaromatic, preferably styrene. These units derived from another monomer may also be a conjugated diene.

[0072] According to a particularly preferred embodiment of the invention, the thermoplastic blocks A are essentially composed of α-methylstyrene units, that is to say, the thermoplastic blocks A do not comprise any units of a monomer other than α-methylstyrene. Thus, improved thermal resistance at higher temperatures is observed for the thermoplastic elastomer, as well as for the composition containing it. For this reason, the thermoplastic blocks A have a Tg that is preferably greater than or equal to 100°C, more preferably at least 120°C, and even more preferably at most 200°C, advantageously varying from 100°C to 200°C, preferably from 120°C to 180°C.

[0073] The minimum proportion of thermoplastic blocks A in the first plastic elastomer can vary depending on the conditions of use of the composition according to the invention and is adjusted by a person skilled in the art. Preferably, the two thermoplastic blocks A represent at least 10% by mass relative to the mass of the first thermoplastic elastomer, preferably from 10% to 45% by mass, more preferably from 10% to 40% by mass.

[0074] In the context of the invention, the polymer composition may comprise one or more first thermoplastic elastomers TPE11 of formula ABA. In the case where there are several, they are differentiated by their macrostructure or their microstructure.

[0075] Advantageously, TPE11 is a triblock thermoplastic elastomer of formula ABA in which the A blocks each represent a poly(α-methylstyrene) thermoplastic block and the B block is a diene elastomer block, the B block being in particular a homopolymer of a 1,3-diene or a copolymer of a 1,3-diene, the 1,3-diene being as defined above, the 1,3-diene being preferably 1,3-butadiene.

[0076] The triblock thermoplastic elastomer TPE12 of formula A'-B'-A'

[0077] The triblock thermoplastic elastomer designated TPE12 is useful for implementation of the present invention is of formula A'-B'-A', in which A' is a thermoplastic block comprising predominantly α-methylstyrene units by mole and B' is a statistical copolymer elastomer block comprising diene units and vinylaromatic units, in particular a statistical copolymer elastomer block (1,3-diene-co-vinylaromatic monomer). The diene elastomer block “B’” or B’ block

[0078] Block B' of the second TPE, for the purposes of the invention, can be any statistical copolymer comprising diene units and vinylaromatic units, in particular styrene units, known to those skilled in the art. It generally has a Tg below 0°C and very preferably below -10°C. A Tg value above these values ​​may reduce the performance of the composition according to the invention when used at very low temperatures. Also preferably, the Tg of block B' is above -100°C.

[0079] By statistical copolymer elastomer formed of diene units and styrene units (or elastomer block "B'") is meant a statistical copolymer elastomer derived at least in part from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not) and at least in part from vinylaromatic monomers, monomers of formula ArCH=CH2 or Ar-CMe=CH2, the symbol Ar representing an aromatic group.

[0080] Preferably, block B' is an elastomer obtained by statistical copolymerization of one or more conjugated dienes having 4 to 15 carbon atoms with one or more vinylaromatic monomers having 8 to 20 carbon atoms.

[0081] Suitable conjugated dienes for use according to the invention include, in particular, 1,3-dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(alkyl in Ci-C5)-1,3-butadiene such as 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, phenyl-1,3-butadiene and 1,3-pentadiene.

[0082] Preferably, block B' comprises 1,3-diene units having 4 to 12 carbon atoms, more particularly, block B' comprises 1,3-butadiene units.

[0083] Suitable vinylaromatic monomers include styrene, α-methylstyrene, ortho-meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tert-butylstyrene, methoxystyrenes, vinylmesitylene, divinylbenzene and vinylnaphthalene.

[0084] According to one embodiment of the invention, the elastomer block B' comprises units of styrene or Ta-methylstyrene or both units of styrene and units of α-methylstyrene, preferably units of styrene.

[0085] Block B' is preferably a random copolymer comprising 1,3-butadiene units and styrene units. More preferably, block B' is a random copolymer of 1,3-butadiene and styrene.

[0086] According to one embodiment of the invention, the elastomer block B' advantageously comprises more than 5% by mass to less than 45% by mass, preferably more than 10% by mass to less than 40% by mass of styrene relative to the mass of block B'.

[0087] Preferably for the invention, block B' has a number-average molar mass (“Mn”) of at least 45,000 g / mol, preferably at least 65,000 g / mol and at most 700,000 g / mol, preferably at most 500,000 g / mol, so as to impart good elastomeric properties and satisfactory mechanical strength to the second thermoplastic elastomer, as well as to the composition according to the invention. The number-average molar mass of block B' can be determined by size-exclusion chromatography in a manner known to those skilled in the art using a calibration curve made from polystyrene standards. The thermoplastic block “A'” or block A'

[0088] The TPE12 triblock thermoplastic elastomer of formula A'-B'-A' according to the invention comprises two terminal thermoplastic, or rigid, blocks, block A' comprising α-methylstyrene units.

[0089] Preferably, the thermoplastic blocks A' each have a number-average molar mass (“Mn”) of at least 5,000 g / mol, preferably at least 7,000 g / mol, and at most 100,000 g / mol, preferably at most 50,000 g / mol. The number-average molar mass of the blocks A' can be determined by size-exclusion chromatography in a manner known to those skilled in the art and is expressed herein relative to polystyrene standards.

[0090] According to the invention, the thermoplastic blocks A' comprise predominantly by mole of α-methylstyrene units to provide good thermal resistance to the thermoplastic elastomer, as well as to the composition according to the invention. Each thermoplastic block A' preferably comprises more than 95% by mole of α-methylstyrene units.

[0091] When the thermoplastic blocks A' further comprise units of at least one other monomer, this monomer may be vinylaromatic, preferably styrene. These units of another monomer may also be a conjugated diene.

[0092] According to a particularly preferred embodiment of the invention, the thermoplastic blocks A' are essentially composed of α-methylstyrene units, that is to say, the thermoplastic blocks A' do not comprise any units of a monomer other than α-methylstyrene. Thus, improved thermal resistance at higher temperatures is observed in the thermoplastic elastomer, as well as in the composition according to the invention. For this reason, the thermoplastic blocks A' exhibit a Tg that is preferably greater than or equal to 100°C, in a more preferentially of at least 120°C, and even more preferably of at most 200°C, advantageously varying from 100°C to 200°C, preferably from 120°C to 180°C.

[0093] The minimum proportion of thermoplastic blocks A' in the second thermoplastic elastomer can vary depending on the conditions of use of the composition according to the invention and is adjusted by a person skilled in the art. Preferably, the thermoplastic blocks A' represent at least 10% by mass relative to the mass of the thermoplastic elastomer, preferably from 10% to 45% by mass, more preferably from 10% to 40% by mass.

[0094] Advantageously, the second TPE is a triblock thermoplastic elastomer of formula A'-B'-A' in which the A' blocks each represent a poly(α-methylstyrene) thermoplastic block, the B' block is a statistical copolymer elastomer block of a 1,3-diene and a vinylaromatic monomer, the 1,3-diene being as defined above, preferably 1,3-butadiene and the vinylaromatic monomer being as defined above, preferably styrene.

[0095] In the context of the invention, the polymer composition may comprise one or more second thermoplastic elastomers A'-B'-A'. In the case where there are several, they are differentiated by their macrostructure or their microstructure.

[0096] The first thermoplastic elastomer of the polymer composition according to the invention is TPE11 according to a first variant of the invention, is TPE12 according to a second variant of the invention and a mixture of the two thermoplastic elastomers TPE11 and TPE12 according to a third variant of the invention.

[0097] Quantity of the first thermoplastic elastomer (TPE1)

[0098] In the polymer composition according to the invention, the proportion of the first thermoplastic elastomer (TPE1), whether this TPE1 is TPE11 or TPE12 or a mixture of the two, is preferably in the range of 50 to 96 parts per annum, preferably 60 to 80 parts per annum, preferably 60 to 70 parts per annum.

[0099] When TPE1 is a mixture of TPE11 and TPE12, the mass percentage of TPE11 relative to the total mass of TPE11 and TPE12 is from 50 to 90.

[0100] According to a particular embodiment, the composition further comprises one or more thermoplastic poly(α-methylstyrene) homopolymers.

[0101] According to a particular embodiment of the invention, the composition comprises a homopolymer of α-methylstyrene (poly(α-methylstyrene)) in a mass proportion ranging from 5 to 45% by mass relative to the total mass of the composition. The second thermoplastic elastomer

[0102] According to the invention, the polymer composition comprises at least a second thermoplastic elastomer (TPE2) comprising at least one polyether elastomer block and at least one thermoplastic block (TP), which thermoplastic block has a melting temperature (Tf) in the range of 130°C to 190°C.

[0103] For the purposes of the invention, the second thermoplastic elastomer (TPE2) is a block copolymer comprising at least one polyether-type elastomer block and at least one thermoplastic (TP) block. This elastomer is also referred to as polyether-block TPE and TP or TPE2 in the present text.

[0104] For the purposes of the invention, the melting temperature (Tf) of the TP block of the TPE2 is within a range of 130°C to 190°C. Advantageously, the Tf of the TPE2 is within a range of 130°C to 180°C.

[0105] Structure of the second thermoplastic elastomer (TPE2)

[0106] The number-average molar mass (denoted Mn) of TPE2 is preferably between 20,000 and 200,000 g / mol, and even more preferably between 25,000 and 150,000 g / mol. Thus, it has been found that a value in the range of 30,000 to 120,000 or 35,000 to 100,000 is particularly well suited, especially for use of the second TPE according to the invention.

[0107] The number-average molar mass (Mn) of the second TPE elastomer is determined in a manner known to those skilled in the art, by size exclusion chromatography (SEC) using a calibration curve made from standard polystyrenes.

[0108] The second TPE can be in a linear form. For example, the second TPE can be a triblock copolymer: polyether block / TP block / polyether block, that is, a central thermoplastic block and two terminal elastomer blocks, one at each end of the elastomer block. Alternatively, TPE2 can be a multiblock copolymer, which can be a linear sequence of polyether elastomer blocks and thermoplastic TP blocks.

[0109] Alternatively, the TPE2 useful for the purposes of the invention may be in a star shape with at least three points. For example, the TPE2 may then consist of a star-shaped polyether elastomer block with at least three points and a thermoplastic TP block, located at the end of each of the points of the polyether elastomer block. The number of points of the central elastomer may vary, for example from 3 to 12, and preferably from 3 to 6.

[0110] Alternatively, TPE2 can be in a branched or dendrimer form. TPE2 can then consist of a branched or dendrimer polyether elastomer block and a thermoplastic TP block, located at the ends of the branches of the dendrimer elastomer block.

[0111] Preferably, the TPE2 is presented in linear and multiblock form.

[0112] The mass fraction of polyether elastomer blocks in TPE2 is preferably in the range of 10% to 90%, more preferably 25% to 60% and more preferably 30% to 50%.

[0113] The mass fraction of TP blocks in TPE2 is preferably in the range of 10% to 90%, preferably 40% to 75%, preferably still 50% to 70%.

[0114] The elastomer blocks of the second thermoplastic elastomer (TPE2)

[0115] The elastomer blocks of the second TPE for the purposes of the invention, can be any polyether type elastomers known to the person skilled in the art.

[0116] These polyether blocks preferably have a Tg (glass transition temperature) measured by differential scanning calorimetry, DSC, according to a method defined later.

[0117] In the context of the present invention, the polyether blocks may be composed of monomer units selected from cyclic alcohols or ethers, preferably aliphatic cyclic alcohols or ethers, such as ethanol or tetrahydrofuran. Among the polyethers, those from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycol (PEG), polypropylene ether glycol (PPG), polyhexamethylene ether glycol, polytrimethylene ether glycol (PO3G), poly(3-alkyltetrahydrofuran), and mixtures thereof, are preferably selected. Even more preferably, the polyether is selected from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycol (PEG), and mixtures thereof.

[0118] Advantageously, the elastomeric blocks of the second TPE have, in total, an average number molar mass ("Mn") ranging from 100 g / mol to 6000 g / mol, preferably from 200 g / mol to 3000 g / mol and 200 to 1100 so as to give the second TPE good elastomeric properties and sufficient mechanical strength compatible with the use of the composition according to the invention.

[0119] The polyether elastomer block can also be made up of several polyether elastomer blocks as defined above which differ from each other in their composition. The thermoplastic blocks of TPE2

[0120] The thermoplastic blocks of the second TPE are preferably blocks selected from polyamide blocks. Even more preferably, the thermoplastic blocks of TPE2 are selected from the group consisting of polyamides of type PA6, PAU, PA12, PA4.12, PA4.14, PA4.18, PA6.10, PA6.12, PA6.14, PA6.18, PA9.12, PA10.10, PA10.12, PA10.14, PA10.18 and their mixtures; preferably the thermoplastic blocks of TPE2 are selected from the group consisting of polyamides of type PA6, PAU, PA12 and their mixtures.

[0121] Polyether block TPEs and particular TPs in which the thermoplastic blocks TP are polyamides are usually denoted TPE-A or TPA (thermoplastic copolyamide) or PEBA (copolyether block amide), and they are particularly preferred for the purposes of the invention.

[0122] According to the invention, the thermoplastic blocks of TPE2 have, in total, an average number molar mass (“Mn”) ranging from 300 g / mol to 15,000 g / mol, 600 to 5,000 g / mol so as to give TPE2 good elastomeric properties and sufficient mechanical strength compatible with the use of the composition according to the invention.

[0123] The thermoplastic block can also be made up of several thermoplastic blocks as defined above. Examples of TPE2

[0124] Examples of commercially available TPE2s include PEBA elastomers of the "PEBAX" type, marketed by Arkema, for example under the name "PEBAX 4033", "PEBAX 6333", "PEBAX 2533", "PEBAX 7233", "35R53", "40R53", "55R53", or "VESTAMID E" marketed by EVONIK, for example under the name "VESTAMID E55" or "VESTAMID E62", or any other PEBA from other suppliers. Quantity of TPE2

[0125] In the context of the invention, the polymer composition may comprise one or more second thermoplastic elastomers TPE2. In the case where there are several, they are differentiated by their macrostructure or their microstructure.

[0126] In the polymer composition according to the invention, the proportion of the TPE2 elastomer with polyether and TP blocks is preferably in the range of 4 to 90 pc, preferably 25 to 70 pc, preferably 30 to 45 pc.

[0127] According to a particular embodiment, the composition further comprises one or more thermoplastic poly(α-methylstyrene) homopolymers.

[0128] According to a particular embodiment of the invention, the composition comprises a homopolymer of α-methylstyrene (poly(α-methylstyrene)) in a mass proportion ranging from 5 to 45% by mass relative to the total mass of the composition. Plasticizing hydrocarbon resin

[0129] According to a preferred embodiment of the present invention, the composition further comprises a plasticizing hydrocarbon resin, optionally hydrogenated, having a Tg (glass transition temperature) greater than or equal to 40°C, having an aromatic proton content less than or equal to 30 and a number-average molar mass (Mn) greater than or equal to 600 g / mol.

[0130] As is known to those skilled in the art, the term "resin" is reserved in this application, by definition, for a compound which is, on the one hand, solid at room temperature (23°C) (as opposed to a liquid plasticizing compound such as an oil), and on the other hand, compatible (i.e., miscible at the rate used, typically greater than or equal to 5 pc) with the thermoplastic elastomers with which it is blended.

[0131] Such a plasticizing hydrocarbon resin is for example chosen from cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), dicyclopentadiene homopolymer or copolymer resins (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins and mixtures of these resins. Among the copolymer resins above, special mention can be made of those chosen from the group consisting of (D)CPD / vinylaromatic copolymer resins, (D)CPD / terpene copolymer resins, terpene phenol copolymer resins, (D)CPD / C5 cut copolymer resins, (D)CPD / C9 cut copolymer resins, terpene / vinylaromatic copolymer resins, C5 cut / vinylaromatic copolymer resins, and mixtures of these resins.

[0132] The term "terpene" here encompasses, in a well-known way, the monomers α-pinene, β-pinene and limonene. Suitable examples of vinylaromatic monomers include styrene, α-methylstyrene, rortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, and any vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut).

[0133] In particular, we can mention resins chosen from the group consisting of terpene homopolymer or copolymer resins, C5 / C9 cup copolymer resins, and mixtures of these resins.

[0134] The plasticizing hydrocarbon resin useful for the needs of the invention may optionally be hydrogenated.

[0135] The plasticizing hydrocarbon resin, optionally hydrogenated, according to the invention has a number-average molar mass (Mn) greater than or equal to 600 g / mol. Preferably, the plasticizing hydrocarbon resin, optionally hydrogenated, has a number-average molecular mass (Mn) in the range of 600 to 1500 g / mol.

[0136] Preferably, the plasticizing hydrocarbon resin, possibly hydrogenated, has a polymolecularity index Ip less than or equal to 2, preferably less than or equal to 1.8, preferably less than 1.7.

[0137] According to embodiments, the plasticizing hydrocarbon resin according to the invention, optionally hydrogenated, has a Tg within a range of 30°C to 150°C, as well as an average number-average molar mass Mn within a range from 600 to 1500 g / mol and an aromatic proton content in a range from 0 to 30%.

[0138] According to embodiments, the percentage of plasticizing hydrocarbon resin, possibly hydrogenated, is in a range from 5 to 70 parts per cent, preferably from 5 to 55 parts per cent.

[0139] The plasticizing hydrocarbon resins, possibly hydrogenated, which can be used according to the invention are commercially available under the references "A125" and "S135" marketed by DRT, under the reference NevChem 140 marketed by Neville Chemical, under the references PICCOTAC 8090 and PICCOTAC 9095 marketed by EASTMANN, under the reference Sylvatraxx 6720 marketed by KRATON.

[0140] The table below summarizes the characteristics of the commercial resins useful for the needs of the invention cited above. Resin Name Supplier Nature Tg Resin (°C) %H Aromatic Mn (g / l) A125 DRT Terpene (alpha-pinene) 84 1 810 NevChem 140 Neville Chemical C5 / C9 86 16 830 PICCOTAC 8090 EASTMANN C5 / C9 44 8 850 PICCOTAC 9095 EASTMANN C5 42 2 1071 S135 DRT Terpene (beta-pinene) 85 0 1245 Sylvatraxx 6720 KRATON Terpene / phenol 67 27 881 Synthesis

[0141] The thermoplastic elastomers useful for the needs of the invention can be manufactured in a known manner according to various synthesis methods described in the prior art.

[0142] A first synthesis method consists, for example, of anionically polymerizing α-methylstyrene to simultaneously form the two thermoplastic blocks in the presence of polydienyldilithium as a polymerization initiator. For example, WO8505116A1 and EP0014947A1 describe such methods which include the copolymerization of styrene and α-methylstyrene to generate the thermoplastic blocks. This yields a triblock copolymer of the type poly(α-methylstyrene-co-styrene)-β-polydiene-β-poly(α-methylstyrene-co-styrene). Similar synthesis methods can be considered for manufacturing poly(α-methylstyrene)-β-polydiene-poly(α-methylstyrene) triblock polymers using polydienyllithium as a polymerization initiator. Such a process is described for example in FR3045615.

[0143] A second synthesis method consists of first anionically polymerizing α-methylstyrene. Then, in a second step, the diene monomer is polymerized onto the resulting live poly(α-methylstyrene) chains. This yields a poly(α-methylstyrene)-β-polydiene diblock polymer with a live dien end. To obtain a triblock thermoplastic elastomer, a coupling agent is added at this stage to couple the dienyl blocks of the chains. This step is carried out in a manner known per se. Coupling agents generally contain a silicon or tin atom substituted with two reactive groups at the carbanion end of the live polymer chains. Examples of coupling agents include di-halogenotins and di-halogenosilanes, notably dibutyltin dichloride or dimethyldichlorosilane, or dialkoxysilanes.The polymer resulting from the coupling step is a poly(α-methylstyrene)-β-polydiene-β-poly(α-methylstyrene) triblock.

[0144] Processes for implementing the second synthesis method are described, for example, in US4302559A. The synthesis of the block copolymer comprises a first step of polymerizing α-methylstyrene at low temperature in the presence of a first polar agent, called a polar activator, to form the poly(α-methylstyrene) block. In a second step, a small amount of conjugated diene is added to add a live polydienyl block of a few units to the chain end of the poly(α-methylstyrene) block, thus preventing the depolymerization of the α-methylstyrene. This is followed by a second addition of conjugated diene in the presence of another polar agent, called a polar activator, to allow the formation of the second block by subsequent polymerization of the conjugated diene while statistically inserting the residual α-methylstyrene into the polymer chain.To obtain the triblock copolymer, the polymer from the last polymerization step is coupled using a coupling agent. The central diene elastomer block of the triblock copolymer is, according to this synthesis method, a poly(butadiene-co-α-methylstyrene) statistical copolymer.

[0145] Other processes implementing this second method of synthesizing a poly(α-methylstyrene)-β-polydiene-β-poly(α-methylstyrene) triblock copolymer are described as yielding a central diene elastomer block free of α-methylstyrene. For example, in document FR2243214, the process consists, in a first step, of homopolymerizing α-methylstyrene in concentrated medium at temperatures between 0°C and 40°C. Following this step, the conjugated diene and the solvent necessary for the synthesis of the poly(conjugated diene) block are added. After this final polymerization step, the resulting polymer is coupled using a coupling agent. More recently, WO2020070406A1 describes another process for the synthesis of a triblock copolymer poly(α-methylstyrene)-β-polydiene-β-poly(α- methylstyrene) whose central diene elastomer block is also free of α-methylstyrene.

[0146] Those skilled in the art will understand that, depending on the method and conditions of synthesis of the thermoplastic elastomer, the resulting product may consist, in addition to the ABA triblock (or A'-B'-A' triblock), of other macromolecule populations such as thermoplastic polymers having the microstructure of block A (or A'), diene elastomers having the microstructure of block B (or B'), or diblock polymers of formula AB (or A'-B'), blocks A, A', B, and B' being as defined in this application. Thus, within the scope of the invention, those skilled in the art will understand that the product of the synthesis may comprise all of these populations when the triblock elastomer is not isolated at the end of its synthesis. The product resulting from the synthesis of the ABA triblock and the A'-B'-A' triblock may comprise at most 20% by mass of a diblock polymer of formula AB and a diblock polymer of formula A'-B' respectively.Similarly, the product resulting from the synthesis may include a thermoplastic polymer having the microstructure of block A in the case of ABA triblock synthesis (or A' in the case of A'-B'-A' triblock synthesis).

[0147] Polymerization can be carried out by a continuous process or a batch process.

[0148] The polymer composition according to the invention may further comprise at least one component selected from non-thermoplastic elastomers, reinforcing fillers selected from carbon blacks and other reinforcing fillers, organic and inorganic of siliceous type in particular silica, as well as mixtures of these fillers, elastomer / filler coupling agents, non-reinforcing fillers, processing agents, stabilizers, plasticizers, pigments, antioxidants, anti-fatigue agents, anti-ozonating waxes, adhesion promoters, reinforcing resins, crosslinking systems based on sulfur and / or peroxide and / or bismaleimides, crosslinking activators including zinc monoxide and stearic acid, guanidic derivatives, extending oils, silica coating agents.

[0149] The present invention further relates to a finished or semi-finished product intended for the manufacture of tires comprising a polymer composition according to the invention.

[0150] Another object of the invention is a tire comprising a tread, which tire comprises a polymer composition according to the present invention in all or part of its tread. EXAMPLES OF THE INVENTION'S IMPLEMENTATION I. Tests and measurements: A - Measurement of the Mn of TPEs

[0151] The macrostructure (Mw, Mn, Ip) of TPEs is determined by size exclusion chromatography (SEC) on the basis of ISO 16014 (Determination of average molecular mass and molecular mass distribution of polymers using size exclusion chromatography), ASTM D5296 (Molecular Weight Averages and molecular weight distribution of polystyrene by High performance size exclusion chromatography) and DIN 55672 (size exclusion chromatography).

[0152] For these measurements, the TPE sample is first solubilized in stabilized tetrahydrofuran at a concentration of 1 g / L; the solution is then filtered with PTFE filters with a porosity of 0.45 µm before injection. 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 40 min. A set of Polypore columns made of a polystyrene divinylbenzene gel with controlled porosity (set of three AGILENT columns) is used. The injected volume of the polymer sample solution is 100 µL. The detector is a WATERS 2410 differential refractometer, also thermostated at 35°C, and its associated software for processing the chromatographic data is the WATERS Alliance system.

[0153] Polymer chains are separated according to the size they occupy when solubilized in the solvent: the larger the volume they occupy, the less accessible the pores of the columns are to them and the shorter their elution time.

[0154] The calculated number average molar masses are relative to a calibration curve made from commercial standard polystyrenes "PSS-pskitlh-3" in the case of thermoplastic polymers comprising α-methylstyrene units alone.

[0155] The calculated number average molar masses are relative to a calibration curve made from commercial standard polybutadienes "PSS-bdfkit" in the case of products comprising dibloc and / or tribloc thermoplastic elastomers containing butadiene units.

[0156] In the case of products resulting from the synthesis of block thermoplastic elastomers (thermoplastic block comprising α-methylstyrene—β-polydiene—β- thermoplastic block comprising α-methylstyrene units) containing less than 10% by mass of thermoplastic polymer comprising poly(α-methylstyrene) units, the distribution of the different species in the product is determined from the integration of the RI signal of the SEC chromatograms. The mass proportion of each species is related to the integral of all the RI signals in the chromatogram.

[0157] In the case of products containing more than 10% by mass of thermoplastic polymer comprising poly(α-methylstyrene) units, the distribution of different species of the product is produced from the integration of the RI signal of the SEC chromatograms by modulating the RI response by the value of the specific increment of the refractive index dn / dc of each species or by producing a calibration line by dosed addition of thermoplastic polymer comprising poly(α-methylstyrene) units, in a manner known to the person skilled in the art.

[0158] B - Differential scanning calorimetry (DSC) analysis of TPE

[0159] The characterization of the Tg values ​​of the elastomer block and the thermoplastic blocks of the first and second thermoplastic elastomers TPE1 and TPE2 is carried out by DSC measurement (Mettler Toledo DSC1 instrument). The instrument is operated under a helium atmosphere. A sample of 10 to 20 mg of thermoplastic elastomer is placed in a crucible commonly used by those skilled in the art to perform Tg measurements.

[0160] The sample is first placed in an isothermal environment at +25°C for 2 minutes and then cooled to -150°C at a rate of 50°C per minute. An isothermal environment of -150°C is then applied for 10 minutes. A first heating cycle then begins from -150°C to +10°C at a rate of 20°C per minute and continues from 10°C to 250°C at a rate of 50°C per minute. The sample then undergoes quenching to reach -150°C at the maximum rate allowed by the apparatus. The sample is then maintained in an isothermal environment at -150°C for 15 minutes. The second heating process then begins from -150°C to +10°C at a rate of 20°C per minute (measurement range of the Tg of the elastomer portion of the TPE) and continues from +10°C to +250°C at a rate of 50°C per minute (measurement range of the Tg of the thermoplastic blocks). In this measurement, only the second heating process is used.

[0161] C - Proton nuclear magnetic resonance (1H NMR)

[0162] The proportions of the different monomer units within thermoplastic elastomers are determined by NMR analysis. Spectra are acquired on a 500 MHz BRUKER spectrometer equipped with a 5 mm BBIz-grad broadband probe. The quantitative 1H NMR experiment uses a simple 30° pulse sequence and a 5-second repetition interval between each acquisition. The samples are solubilized in CDC13. The integration regions considered for quantification are the spectral signature regions of the monomer units known to those skilled in the art.

[0163] D- Measurement of viscosity RPA (Rubber Process Analyzer)

[0164] The method for measuring G' and G” uses an RPA-type oscillating disk rheology device, such as the 2000LV device (Oscillating Disk Rheometer) supplied by Alpha Technologies®, equipped with the standard viscosity sensor 200 in. lbs (22.6 dNm). The RPA machine allows a sample of material enclosed in a chamber (or enclosure) with biconical walls to be subjected to torsional stress.

[0165] To perform the measurement of G'(T) (elastic shear modulus), a sample of material approximately 30 mm in diameter and with a mass of approximately 5 g is placed in the chamber or enclosure of the RPA (a total volume of 5 cm³ is considered optimal; the quantity is sufficient when a small amount of sample escapes from each side of the chamber and is visible at the end of the test). At the end of this operation, the sample is perfectly molded within the closed chamber of the RPA.

[0166] A shaping operation is carried out by applying a temperature of 180°C to the sample enclosed in the RPA chamber for a time of 40 minutes with a deformation of 2.8% peak-to-peak at 1.7 Hz.

[0167] At the end of this operation, the sample is perfectly molded in the closed chamber of the RPA. The sample is then cooled to 40°C directly in the RPA chamber. It is then possible to begin measuring the value of G' at 5% peak-to-peak strain and 10 Hz in a temperature range varying from 40 to 200°C (ramp: 3°C / min).

[0168] A curve of variation of G' as a function of temperature is obtained, from which the modulus G' of the composition at 190°C can be extracted.

[0169] The shaping and measurement steps of G' are done without intervention, by programming the RPA machine.

[0170] It is recalled that, as is well known to those skilled in the art, the value of the RPA viscosity at 190°C is representative of the processability of the material: the lower the viscosity at 190°C, the easier the material is to shape.

[0171] E- Measurement of the complex dynamic shear modulus

[0172] Dynamic properties (after forming): Tensile test

[0173] The dynamic properties G*(10%) at 23°C are measured on a viscoelastic analyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a cross-linked composite sample (cylindrical specimen 4 mm thick and 400 mm² cross-section) is recorded under sinusoidal alternating simple shear loading at a frequency of 10 Hz, under defined temperature conditions, for example, 23°C according to ASTM D 1349-99, or, where applicable, at a different temperature. A strain amplitude sweep is performed from 0.1 to 50% (forward cycle), then from 50% to 1% (reverse cycle). The results used relate to the complex dynamic shear modulus G*. For the return cycle, the value of the complex dynamic shear modulus G*(10%) at 10% strain, at 23°C, is indicated.

[0174] It is recalled that, as is well known to those skilled in the art, the value of G* 10% at 23 °C is representative of the stiffness of the material: the lower G* 10% at 23 °C is, the lower the stiffness.

[0175] II. Polymer synthesis and preparation of polymer compositions

[0176] In the following tests, the following designation will be adopted:

[0177] poly(α-methylstyrene) = PAMS Polyether-polyamide block copolymer (copoly(ether-b-amide)) = PEBA A - The first thermoplastic elastomer TPE1

[0178] Al Synthesis of a triblock polymer poly(α-methylstyrene)-β-polybutadiene-β-poly(α-methylstyrene) or TPE11

[0179] In an 80 L double-jacketed reactor, 2.0 L of cyclohexane, 0.106 L of tetrahydrofuran, and 5 kg of α-methylstyrene are successively introduced under constant nitrogen purging. All products have been previously purified and / or dried.

[0180] After the temperature has been brought to 17°C, 0.125 mol of sec-butyllithium is introduced into the reactor as a solution in cyclohexane at 0.13 mol / L. The molar ratio of activator (also called polar agent), in this case tetrahydrofuran / initiator, in this case sec-butyllithium, is 2.3.

[0181] After 33 minutes of polymerization at 17°C, the measured conversion of AMS is 32%. 0.675 kg of 1,3-butadiene is then introduced, and the reaction mixture is diluted with 23 L of cyclohexane. Next, 3.9 kg of 1,3-butadiene is added, and the temperature is raised to 40°C. The temperature is maintained at a maximum of 42°C. Polymerization lasts 102 minutes. The measured conversion of 1,3-butadiene is 92%. After polymerization, 0.06 moles of dimethyldichlorosilane are added with constant stirring. The reaction mixture is maintained at 40°C for 30 minutes.

[0182] Following this coupling step, a triblock polymer poly(α-methylstyrene)-β-polybutadiene-β-poly(α-methylstyrene) is synthesized. Next, 0.2 parts per million of an antioxidant, Irganox 1520L® (from BASF), is added. The antioxidantized polymer is separated from the solvent by steam stripping, and then the polymer is dried in a vacuum oven with nitrogen flushing at 60°C.

[0183] The Tg DSC of the polybutadiene flexible block -49°C (AT, glass transition width, being equal to 9°C)

[0184] A-2 - Synthesis of a second triblock polymer poly(α-methylstyrene)-β-poly(butadiene-co-styrene)-β-poly(α-methylstyrene) (or TPE 1 2)

[0185] In an 80 L double-jacketed reactor, 2.6 L of cyclohexane, 0.028 L of tetrahydrofuran, and 2 kg of alpha-methylstyrene are successively introduced under constant nitrogen purging. All products have been previously purified and / or dried.

[0186] After the temperature has been brought to 17°C, 0.15 mol of sec-butylithium in the form of a 0.16 mol / L cyclohexane solution is introduced into the reactor. The molar ratio of activator (tetrahydrofuran) to initiator (sec-butyllithium) is 2.3.

[0187] After 40 minutes of polymerization, the measured conversion is 34%. 0.567 kg of 1,3-butadiene and 0.24 kg of styrene are then introduced, after which the reaction mixture is diluted with 43.6 L of cyclohexane. Next, 3.8 kg of 1,3-butadiene and 1.6 kg of styrene are introduced, and the temperature is raised to 40°C. The temperature is maintained at a maximum of 42°C. Polymerization lasts 85 minutes. The measured conversion is 68%.

[0188] After polymerization, 0.072 moles of dimethyldichlorosilane are added under constant stirring. The reaction mixture is maintained at 40 °C for 30 minutes.

[0189] Following this coupling step, a triblock polymer poly(α-methylstyrene)-β-butadiene-styrene-β-poly(α-methylstyrene) is synthesized. 0.2 wt. of an antioxidant, Irganox 1520L® (from BASF), is added. The antioxidantized polymer is separated from the solvent by steam stripping, and then the polymer is dried in a vacuum oven with nitrogen flushing at 60°C.

[0190] The Tg DSC of the flexible poly(butadiene-co-styrene) block -48°C (AT, glass transition width, being equal to 9°C). B- The second thermoplastic elastomer TPE2

[0191] The second thermoplastic elastomers TPE2-1 and TPE2-2 used in the tests come from Arkema under the trade names PEBAX 2533® and PEBAX 7233® which are elastomers with flexible polyether blocks and rigid thermoplastic polyamide blocks.

[0192] The characteristics of commercial “PEBAX” are given on the HAL theses site (Christopher CLOSA, HAL Id: tel-03794048). C- The plasticizing hydrocarbon resin

[0193] The resins used in the tests are chosen from among the resins with trade names A125 and S135 marketed by DRT, NevChem 140 marketed by Neville Chemical, PICCOTAC 8090 and PICCOTAC 9095 marketed by Eastmann, Sylvatraxx 6720 marketed by Kraton, and Novarez TK100 marketed by Rain Carbon. D- Preparation of Polymer Compositions

[0194] Introduce TPE1 and TPE2 into an internal mixer with a volume of 85 cm3 heated to a temperature of 120°C. Mixing is carried out at a paddle speed in the range of 80 to 120 rpm. The mixture is heated to a temperature above the melting point for at least four minutes.

[0195] Table 1 summarizes the components of the polymeric compositions, their characteristics and respective rates.

[0196] [Table 1]: Mn (Kg / mol) Tg (°C) / T f (°C) Ml M2 M3 M4 M5 TPE1 100 70 70 96 96 TPE11 253.5 -49 70 49 49 67 67 TPE12 154.4 -48 30 21 21 29 29 TPE2-1* 35 -75 / 139 30 4 TPE2-2** 50 -60 / 174 30 4 PICCOT AC 8090 resin 0.850 44 22.3 22.3 22.3 22.3 22.3

[0197] TPE11: triblock polymer poly(α-methylstyrene)-β-polybutadiene-β-poly(α-methylstyrene) TPE12: triblock polymer poly(α-methylstyrene)-β-poly(butadiene-co-styrene)-β-poly(α-methylstyrene) Resin: PICCOTAC 8090 marketed by Eastmann.

[0198] * Thermoplastic elastomer TPE 2-1 “PEBAX 2533 SA 01” from Arkema (Tf = 134°C) ** Thermoplastic elastomer TPE 2-2 “PEBAX 7233 SA 01” from Arkema (Tf = 174°C)

[0199] Tables 2 and 3 show the characteristics and microstructure of the TPEs used in the examples.

[0200] [Tables2] Sample name Mn block P AMS Calibratio nPS Species distribution PAMS / dibloc / triblock (PB calibration) MpPA MS % mass PA MS % mass dib loc % mass triblock TPE 11 14000 8300 2.6 11.4 86 TPE12 12400 8200 3.6 7.9 88.5

[0201] AMS = α-methylstyrene PAMS = poly(α-methylstyrene) % STY = mass percentage of styrene units % PB 1.2 = mass percentage of butadiene units in the form of 1,2- units % PB 1.4 = mass percentage of butadiene units in the form of 1.4 units % AMS = mass percentage of α-methylstyrene units Mp = peak mass % mass = mass percentage.

[0202] [Tables3] Sample Name Mn block Polyether (g / mol) Mn block TP (g / mol) % Polyether %TP TPE2-1* 2000 600 77 23 TPE2-2** 1500 1000 43 57

[0203] * Thermoplastic elastomer TPE 2-1 “PEBAX 2533 SA 01” from Arkema (Tf = 134°C) ** Thermoplastic elastomer TPE 2-2 “PEBAX 7233 SA 01” from Arkema (Tf = 174°C)

[0204] The characteristics of these commercial “PEBAX” are given on the HAL theses website (Christopher CLOSA, HAL Id: tel-03794048). D - Results of Measurements Performed

[0205] Table 4 shows the results of measurements made on the different polymeric compositions, M1 to M5.

[0206] [Tables4 Ml M2 M3 M4 M5 Visco RPA at 190°C 100 52 72 72 87 G* 10% ret at 23°C 100 194 262 107 116

[0207] The results are presented on a basis of 100 relative to the ML control. Compared to composition M1 which comprises TPE1 only, compositions M2 to M5 according to the invention exhibit lower viscosity and similar to higher rigidity.

Claims

Demands

1. A polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer, wherein the first thermoplastic is a TPE11 block thermoplastic elastomer of formula ABA, in which A is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B is a diene elastomer block comprising more than 95% by mass of diene units relative to the mass of the diene elastomer block, or a TPE12 block thermoplastic elastomer of formula A'-B'-A', in which A' is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B' is a statistical copolymer elastomer block comprising diene units and vinylaromatic units, or a mixture of the two TPE11 and TPE12 block thermoplastic elastomers, in which the second thermoplastic elastomer comprises at least one polyether elastomer block and at least a thermoplastic block, TP block,which block TP has a melting temperature, Tf, within a range of 130°C to 190°C.

2. Composition according to claim 1, wherein the thermoplastic blocks A and A' comprise more than 95 mole percent of α-methylstyrene units.

3. Composition according to claim 1 or 2 wherein the thermoplastic blocks A and A' are α-methylstyrene homopolymers.

4. Composition according to any one of the preceding claims wherein the thermoplastic blocks A and A', independently of each other, represent at least 10% by mass respectively with respect to the mass of TPE11 and the mass of TPE12, preferably from 10 to 45% by mass respectively with respect to the mass of TPE11 and the mass of TPE12, preferably again from 10% to 40% by mass respectively with respect to the mass of TPE11 and the mass of TPE12.

5. Composition according to any one of the preceding claims wherein the elastomer block B comprises from 0 to less than 5% by mass of units of one or more vinylaromatic monomers.

6. Composition according to claim 5 wherein the units of one or more vinylaromatic monomers of block B are selected from the styrene units, the α-methylstyrene units and their mixture.

7. Composition according to any one of the preceding claims wherein the elastomer block B is a polybutadiene block (BR).

8. Composition according to any one of the preceding claims wherein the elastomer block B' comprises more than 5% by mass to less than 45% by mass, preferably more than 10% by mass to less than 40% by mass of vinylaromatic units, relative to the mass of block B'.

9. Composition according to any one of the preceding claims wherein the vinylaromatic units of block B' are styrene units.

10. Composition according to any one of the preceding embodiments in which the elastomer block B' comprises units of 1,3-butadiene and units of styrene.

11. Composition according to any one of the preceding embodiments wherein the elastomer block B' is a statistical copolymer of 1,3-butadiene and styrene.

12. Composition according to any one of the preceding claims, wherein the thermoplastic block(s) of the second thermoplastic elastomer are selected from the group consisting of polyamides.

13. Composition according to any one of the preceding claims, wherein the mass fraction of the thermoplastic block (TP) in the second thermoplastic elastomer is in the range of 15% to 60%, preferably 20% to 50%.

14. Composition according to any one of the preceding claims, wherein the second thermoplastic elastomer is selected from the group consisting of block copolymers composed of polyether blocks and polyamide blocks (PEBA).

15. Composition according to any one of the preceding claims, wherein the percentage of the first thermoplastic elastomer in the composition is in the range of 50 to 96 parts per annum, preferably 60 to 80 parts per annum, and the percentage of the second thermoplastic elastomer in the composition is in the range of 4 to 50 parts per annum.

16. A tire comprising a tread, which tire comprises a composition according to any one of claims 1 to 15 in all or part of its tread.