FR3160977A1 - Polymer composition comprising a mixture of thermoplastic elastomers. - Google Patents

Abstract

The invention relates to a polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer, which first thermoplastic is a thermoplastic elastomer with TPE11 blocks of formula A-B-A, 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 the diene units relative to the mass of the diene elastomer block, or a thermoplastic elastomer with TPE12 blocks of formula A’-B’-A’, in which A’ is a thermoplastic block comprising predominantly by mole α-methylstyrene units and B’ is a random copolymer elastomer block comprising diene units and vinylaromatic units, or a mixture of the two thermoplastic elastomers with TPE11 and TPE12 blocks, which second thermoplastic elastomer comprises at least one block polyether elastomer and at least one thermoplastic block, TP block, which TP block has a melting temperature, Tf, in a range from 130°C to 180°C. The invention also relates to a tire comprising such a composition in all or part of its tread.

Description

Polymer composition comprising a mixture of thermoplastic elastomers.

The present invention relates to a polymer composition comprising thermoplastic elastomers.

In the field of tires for motor vehicles, the Applicant has in the past 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.

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 association of the rigid thermoplastic blocks between them gives the material the behavior of a crosslinked elastomer. Indeed, the rigid nodules, formed by zones of association of thermoplastic blocks between them, act as crosslinking nodes. The material is therefore rigid and does not flow. On the other hand, when the temperature is raised above the glass transition temperature or the melting temperature of the rigid blocks, the polymer will be able to flow, allowing the material to be shaped. The latter regains its rigidity when the temperature returns to the operating temperature, lower than the Tg of the thermoplastic blocks. This particularity of TPEs implies a very broad application potential.

Among the most widespread thermoplastic elastomers are styrenic block copolymers, known as styrenic 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 certain applications, the Tg value of polystyrene blocks is insufficient. Indeed, this value does not allow the use of these TPEs to be considered for the manufacture of certain objects subject in particular to specific conditions of use where temperatures exceed 100°C.

As other styrenic TPEs, copolymers having 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 widely described in the state of the art, in academic literature or in patent documentation such as in document WO2007112232A2 or document FR2243214.

The Applicant has previously developed compositions for tires, in particular for tire treads, 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.

A constant objective of tire manufacturers is to improve the properties of the tread, which must meet a large number of technical requirements, including that of having a very good level of road behavior on a motor vehicle. To improve road behavior, as we know, a certain level of tread rigidity is sought.

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

It is generally known that the use of plasticizers in combination with TPEs, in particular TPEs comprising α-methylstyrene-based blocks, makes it possible to improve their processability and formability, as indicated in document WO2012152686 or in document WO2015/113966. However, it is also accepted that the use of plasticizers in a TPE composition makes it possible to reduce its rigidity.

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 retaining the rigidity of the composition.

This objective is achieved in that the inventors discovered during their research, in a surprising manner, 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 a range from 130°C to 180°C, exhibited improved processability, without this being to the detriment of the rigidity of the composition.

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

• lequel premier thermoplastique est

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

a thermoplastic elastomer with TPE11 blocks of formula A-B-A, 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 the diene units relative to the mass of the diene elastomer block, or

a thermoplastic elastomer with TPE12 blocks of formula A’-B’-A’, in which A’ is a thermoplastic block comprising predominantly in moles α-methylstyrene units and B’ is a random copolymer elastomer block comprising diene units and vinylaromatic units, or

• lequel deuxième élastomère thermoplastique comprend au moins un bloc élastomère polyéther et au moins un bloc thermoplastique, bloc TP, lequel bloc TP présente une température de fusion, Tf, comprise dans un domaine allant de 130°C à 190°C.

a blend of the two thermoplastic block elastomers TPE11 and TPE12,

• which second thermoplastic elastomer comprises at least one polyether elastomer block and at least one thermoplastic block, TP block, which TP block has a melting temperature, Tf, within a range from 130°C to 190°C.

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

The invention also relates to a tire comprising a polymer composition in accordance with the invention in all or part of its tread.

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

• lequel premier thermoplastique est

1. polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer,

• which first thermoplastic is

a thermoplastic elastomer with TPE11 blocks of formula A-B-A, 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 the diene units relative to the mass of the diene elastomer block, or

a thermoplastic elastomer with TPE12 blocks of formula A’-B’-A’, in which A’ is a thermoplastic block comprising predominantly in moles α-methylstyrene units and B’ is a random copolymer elastomer block comprising diene units and vinylaromatic units, or

• lequel deuxième élastomère thermoplastique comprend au moins un bloc élastomère polyéther et au moins un bloc thermoplastique, bloc TP, lequel bloc TP présente une température de fusion, Tf, comprise dans un domaine allant de 130°C à 190°C.

a blend of the two thermoplastic block elastomers TPE11 and TPE12,

• which second thermoplastic elastomer comprises at least one polyether elastomer block and at least one thermoplastic block, TP block, which TP block has a melting temperature, Tf, within a range from 130°C to 190°C.

2. Composition according to embodiment 1, in which the thermoplastic blocks A and A’ comprise, independently of one another, more than 95 mol% of α-methylstyrene units.

3. Composition according to embodiment 1 or 2 in which the thermoplastic blocks A and A’ comprise, independently of one another, styrene units.

4. Composition according to any one of embodiments 1 to 2 in which the thermoplastic blocks A and A’ are, independently of one another, homopolymers of α-methylstyrene.

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 elastomer with TPE11 blocks, preferably from 10 to 45% by mass, more preferably 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 elastomer with TPE12 blocks, preferably from 10 to 45% by mass and more preferably from 10% to 40% by mass.

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.

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

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

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 the block B', the vinylaromatic units preferably being styrene units.

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

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

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, PA11, 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 mixtures thereof, preferably the polyamide blocks are chosen from the group consisting of polyamides of type PA6, PA11, PA12 and mixtures thereof.

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 within a range from 15% to 60%, preferably from 20% to 50%.

14. Composition according to any one of the preceding embodiments, in which the polyether elastomer block(s) of the second thermoplastic elastomer are chosen 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, preferably from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycol (PEG) and mixtures thereof.

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).

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

17. Composition according to any one of the preceding embodiments, in which the rate of the first thermoplastic elastomer in the composition is within a range from 50 to 96 pce, preferably from 60 to 80 pce.

18. Composition according to any one of the preceding embodiments, in which the rate of the second thermoplastic elastomer in the composition is within a range from 4 to 50 pce.

19. Composition according to any one of the preceding embodiments, which 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.

20. Composition according to any one of the preceding embodiments comprising at least one component chosen from non-thermoplastic elastomers, reinforcing fillers chosen 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 comprising zinc monoxide and stearic acid, guanidine derivatives, extending oils, silica covering agents.

21. Finished or semi-finished product intended for the manufacture of tires comprising a composition according to any of the preceding embodiments.

22. A tire comprising a tread, which tire comprises a composition according to any one of embodiments 1 to 20 in all or part of its tread.

Definitions

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

On the other hand, any range of values designated by the expression "between a and b" represents the domain within the limits a and b (i.e., excluding the limits a and b), while any range of values designated by the expression "from a to b" means the domain of values from a to b (i.e., including the strict limits a and b).

In this description, the term "part per cent of elastomer" or "pce" means the part by mass of a constituent per 100 parts by mass of the elastomer(s), i.e. of the total mass of the elastomer(s), whether thermoplastic or non-thermoplastic, of the composition. Thus, a constituent at 60 pce will mean, for example, 60 g of this constituent per 100 g of elastomer.

Poly(α-methylstyrene) is commonly understood to mean a homopolymer of α-methylstyrene.

In the present description, the term "units X" (or "units X") or units of the monomer X of a polymer means the monomer units which result from the polymerization of the monomer X. Thus, "α-methylstyrene units" are the units resulting from the polymerization of the monomer α-methylstyrene.

The carbon-containing 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, monomers, polymers, etc.

Detailed description of the invention

The polymer composition according to the invention comprises a first thermoplastic elastomer and a second thermoplastic elastomer.

The first thermoplastic elastomer (TPE1)

The first TPE useful for the purposes of the invention is chosen from: a triblock thermoplastic elastomer (TPE11), of formula A-B-A with two rigid thermoplastic segments A comprising α-methylstyrene units linked by a flexible segment B consisting of a diene elastomer, a triblock thermoplastic elastomer (TPE12) of formula A’-B’-A’ with two rigid thermoplastic segments A’ comprising α-methylstyrene units linked by a flexible segment B’ consisting of a random copolymer elastomer comprising diene units and vinylaromatic units, and a mixture of TPE11 and TPE12.

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 minima, the cohesion between the chains of the TPE risks being affected; on the other hand, an increase in the operating temperature risks affecting the mechanical properties, in particular the properties at break. Furthermore, an excessively high Mn mass can be detrimental to processing. Thus, it has been found that a value in a range of 80,000 to 400,000 g/mol is particularly well suited, in particular to use of the TPE in a tire composition. An Mn in a range of 100,000 to 300,000 g/mol is more preferred.

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

The value of the polymolecularity index Ip (reminder: Ip = Mw/Mn with Mw average molar mass by weight and Mn average molar mass by number) of the TPE is preferably less than 3, more preferably less than 2, even more preferably less than 1.5.

As is known, TPEs exhibit two glass transition temperature (Tg) peaks, 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.

The triblock thermoplastic elastomer TPE11 , of A-B-A formula

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

The diene elastomer block “B” or B block

The B block of the first TPE, for the purposes of the invention, is a diene elastomer. By diene elastomer is meant 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). The B block generally has a Tg of less than 0°C and very preferably less than -10°C. A Tg value higher than these values can reduce the performance of the composition when used at very low temperatures. Also preferably, the Tg of the elastomer block of the TPE is greater than -100°C. The B block has the essential characteristic of containing predominantly by mass diene units. In other words, the diene units of the B block represent the highest weight fraction of the constituent units of the B block.

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 optionally by copolymerization with one or more vinylaromatic monomers having from 8 to 20 carbon atoms.

Suitable conjugated dienes which can be used in accordance with the invention are in particular 1,3-dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(C ₁ -C ₅ alkyl)-1,3-butadienes 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.

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.

Block B is preferably a polybutadiene (BR) or a copolymer of 1,3-butadiene, in particular a copolymer of 1,3-butadiene and a vinyl aromatic monomer.

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

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

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 of the elastomer block B are advantageously chosen from styrene and α-methylstyrene, more advantageously α-methylstyrene.

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 give the thermoplastic elastomers good elastomeric properties and satisfactory mechanical strength. 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

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

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 expressed here relative to polystyrene standards.

According to the invention, the thermoplastic blocks A comprise predominantly in moles α-methylstyrene units in order to provide good thermal resistance to the thermoplastic elastomer, as well as to the composition in accordance with the invention. In other words, the α-methylstyrene units of the block A represent the highest molar fraction of the constituent units of the block A. The thermoplastic block A preferably comprises more than 95% in moles of α-methylstyrene units, a percentage expressed relative to all the constituent monomer units of the block A.

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

According to a particularly preferred embodiment of the invention, the thermoplastic blocks A are essentially composed of α-methylstyrene units, that is to say that the thermoplastic blocks A do not comprise units of a monomer other than α-methylstyrene. Thus, better thermal resistance at higher temperatures of the thermoplastic elastomer is observed, as well as of the composition containing it. For this reason, the thermoplastic blocks A have a Tg which 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.

The minimum content of thermoplastic blocks A in the first plastic elastomer may vary depending on the conditions of use of the composition in accordance with 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.

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

Advantageously, TPE11 is a triblock thermoplastic elastomer of formula A-B-A 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 is preferably 1,3-butadiene.

The triblock thermoplastic elastomer TPE12 , of formula A’-B’-A’

The triblock thermoplastic elastomer noted TPE12 useful for implementing the present invention is of formula A’-B’-A’, in which A’ is a thermoplastic block comprising predominantly in moles α-methylstyrene units and B’ is a random copolymer elastomer block comprising diene units and vinylaromatic units, in particular a random copolymer elastomer block (1,3-diene-co-vinylaromatic monomer).

The diene elastomer block “B’” or B’ block

The B’ block of the second TPE for the purposes of the invention may be any random copolymer comprising diene units and vinylaromatic units, in particular styrene units, known to those skilled in the art. It generally has a Tg of less than 0°C and very preferably less than -10°C. A Tg value higher than these values may reduce the performance of the composition in accordance with the invention when used at very low temperatures. Also preferably, the Tg of the B’ block is greater than -100°C.

By statistical copolymer elastomer formed from diene units and styrenic units (or elastomer block "B'") is meant a statistical copolymer elastomer derived at least in part from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not) and at least in part from vinylaromatic monomers, monomers of formula ArCH=CH ₂ or Ar-CMe=CH ₂ , the symbol Ar representing an aromatic group.

Preferably, block B' is an elastomer obtained by random 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.

Suitable conjugated dienes which can be used in accordance with the invention are in particular 1,3-dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(C ₁ -C ₅ alkyl)-1,3-butadienes 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.

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

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

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

The B’ block is preferably a random copolymer comprising 1,3-butadiene units and styrene units. More preferably, the B’ block is a random copolymer of 1,3-butadiene and styrene.

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 the block B'.

Preferably for the invention, the 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 give the second thermoplastic elastomer good elastomeric properties and satisfactory mechanical strength, as well as the composition in accordance with the invention. The number-average molar mass of the block B' can be determined by size exclusion chromatography in a manner known to those skilled in the art using a calibration curve produced from polystyrene standards.

The thermoplastic block “A’” or A’ block

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

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 expressed here relative to polystyrene standards.

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 in accordance with the invention. Each thermoplastic block A’ preferably comprises more than 95% by mole of α-methylstyrene units.

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

According to a particularly preferred embodiment of the invention, the thermoplastic blocks A' are essentially composed of α-methylstyrene units, that is to say that the thermoplastic blocks A' do not comprise units of a monomer other than α-methylstyrene. Thus, better thermal resistance at higher temperatures of the thermoplastic elastomer is observed, as well as of the composition in accordance with the invention. For this reason, the thermoplastic blocks A' have a Tg which 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.

The minimum content of thermoplastic blocks A’ in the second thermoplastic elastomer may vary depending on the conditions of use of the composition in accordance with 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.

Advantageously, the second TPE is a triblock thermoplastic elastomer of formula A'-B'-A' in which the blocks A' each represent a poly(α-methylstyrene) thermoplastic block, the block B' is a random 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.

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 differ by their macrostructure or their microstructure.

The first thermoplastic elastomer of the polymer composition in accordance with 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.

Quantity of first thermoplastic elastomer (TPE1)

In the polymer composition according to the invention, the content of the first thermoplastic elastomer (TPE1), whether this TPE1 is TPE11 or TPE12 or a mixture of the two, is preferably within a range from 50 to 96 pce, preferably from 60 to 80 pce, preferably from 60 to 70 pce.

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

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

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

According to the invention, the polymer composition comprises at least one 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) within a range from 130°C to 190°C.

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 TPE with polyether blocks and TP or TPE2 herein.

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

Structure of the second thermoplastic elastomer (TPE2)

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

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 produced from standard polystyrenes.

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, i.e. a central thermoplastic block and two terminal elastomer blocks, at each of the two ends of the elastomer block. Also, TPE2 can be a multiblock copolymer which can be a linear chain of polyether elastomer blocks – TP thermoplastic blocks.

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

Alternatively, TPE2 can be in a branched or dendrimeric form. TPE2 can then be composed of a branched polyether elastomer block or dendrimer and a thermoplastic TP block, located at the end of the branches of the dendrimer elastomer block.

Preferably, the TPE2 is in a linear and multi-block form.

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

The mass fraction of TP blocks in TPE2 is preferably in a range from 10% to 90%, preferably from 40% to 75%, more preferably from 50% to 70%.

Elastomer blocks of the second thermoplastic elastomer (TPE2)

The elastomer blocks of the second TPE for the purposes of the invention can be any polyether type elastomer known to those skilled in the art.

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

For the purposes of the present invention, the polyether blocks may be composed of monomer units chosen 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 will preferably be chosen. More preferably, the polyether is chosen from the group consisting of polytetramethylene glycol (PTMG), polyethylene glycol (PEG) and mixtures thereof.

Advantageously, the elastomer blocks of the second TPE have, in total, a number-average molar mass ("Mn") ranging from 100 g/mol to 6,000 g/mol, preferably from 200 g/mol to 3,000 g/mol and 200 to 1,100 so as to give the second TPE good elastomer properties and sufficient mechanical strength compatible with the use of the composition according to the invention.

The polyether elastomer block can also be made up of several polyether elastomer blocks as defined above which differ from each other by their composition.

The thermoplastic blocks of TPE2

The thermoplastic blocks of the second TPE are preferably blocks chosen from polyamide blocks. More preferably, the thermoplastic blocks of TPE2 are chosen from the group consisting of polyamides of type PA6, PA11, 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 chosen from the group consisting of polyamides of type PA6, PA11, PA12 and their mixtures.

The particular polyether block TPEs and TPs in which the thermoplastic TP blocks 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.

According to the invention, the thermoplastic blocks of TPE2 have, in total, a number-average molar mass (“Mn”) ranging from 300 g/mol to 15,000 g/mol, 600 to 5000 g/mol so as to give the TPE2 good elastomeric properties and sufficient mechanical strength compatible with the use of the composition according to the invention.

The thermoplastic block may also consist of several thermoplastic blocks as defined above.

Examples of TPE2

Examples of commercially available TPE2 include PEBA elastomers of the “PEBAX” type, marketed by Arkema, for example under the names “PEBAX 4033”, “PEBAX 6333”, “PEBAX 2533”, “PEBAX 7233”, “35R53”, “40R53”, “55R53” or even “VESTAMID E” marketed by EVONIK, for example under the names “VESTAMID E55” or “VESTAMID E62”, or any other PEBA from other suppliers.

Quantity of TPE2

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.

In the polymer composition according to the invention, the content of the TPE2 elastomer with polyether and TP blocks is preferably within a range from 4 to 90 phr, preferably from 25 to 70 phr, preferably from 30 to 45 phr.

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

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

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 level less than or equal to 30 and a number-average molar mass (Mn) greater than or equal to 600 g/mol.

In a manner known to those skilled in the art, the term “resin” is reserved in the present 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 pce) with the thermoplastic elastomers with which it is mixed.

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 above copolymer resins, mention may be made more particularly 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.

The term "terpene" herein includes, in a known manner, the monomers α-pinene, beta-pinene and limonene. Suitable vinylaromatic monomers are, for example, styrene, α-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut).

More particularly, mention may be made of resins chosen from the group consisting of terpene homopolymer or copolymer resins, C5 cut/C9 cut copolymer resins, and mixtures of these resins.

The plasticizing hydrocarbon resin useful for the purposes of the invention may optionally be hydrogenated.

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 a range from 600 to 1500 g/mol.

Preferably, the plasticizing hydrocarbon resin, optionally 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.

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

According to embodiments, the level of plasticizing hydrocarbon resin, optionally hydrogenated, is within a range from 5 pce to 70 pce, preferably from 5 to 55 pce.

The plasticizing hydrocarbon resins, optionally 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.

The table below summarizes the characteristics of the commercial resins useful for the purposes of the invention cited above. Resin name supplier Nature Resin Tg (°C) %H aromatic Mn (g/mol) 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

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

A first method of synthesis consists, for example, in anionically polymerizing α-methylstyrene in order to concomitantly form the two thermoplastic blocks in the presence of polydienyldilithium as a polymerization initiator. For example, WO8505116A1 and EP0014947A1 describe such methods which comprise the copolymerization of styrene and α-methylstyrene to generate the thermoplastic blocks. A triblock copolymer of the poly(α-methylstyrene-co-styrene)-b-polydiene-b-poly(α-methylstyrene-co-styrene) type is thus obtained. Similar methods of synthesis can be envisaged for manufacturing poly(α-methylstyrene)-b-polydiene-poly(α-methylstyrene) triblock polymers using polydienyllithium as a polymerization initiator. Such a method is for example described in FR3045615.

A second method of synthesis consists of anionically polymerizing α-methylstyrene in a first step. Then, in a second step, the diene monomer is polymerized on the living poly(α-methylstyrene) chains obtained. This gives a poly(α-methylstyrene)-b-polydiene diblock polymer whose dienyl end is living. 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 by two groups reactive with respect to the carbanion end of the living polymer chains. Examples of coupling agents include dihalotin and dihalosilane, including dibutyltin dichloride or dimethyldichlorosilane, or dialkoxysilanes. The polymer resulting from the coupling step is a poly(α-methylstyrene)-b-polydiene-b-poly(α-methylstyrene) triblock.

Methods for implementing the second mode of synthesis are described, for example, in US4302559A. The synthesis of the block copolymer comprises a first step of polymerization of 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 first addition of a small amount of conjugated diene is carried out to add a living polydienyl block of a few units to the chain end of the poly(α-methylstyrene) block and thus avoid depolymerization of the α-methylstyrene, 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 inserting the residual α-methylstyrene in a random manner 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.

Other processes implementing this second method of synthesizing a poly(α-methylstyrene)-b-polydiene-b-poly(α-methylstyrene) triblock copolymer are described as making it possible to obtain 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 a concentrated medium at temperatures between 0°C and 40°C. At the end of this step, the conjugated diene and the solvent necessary for the synthesis of the poly(conjugated diene) block are added. At the end of this last polymerization step, the polymer obtained is coupled using a coupling agent. More recently, WO2020070406A1 describes another process for the synthesis of a poly(α-methylstyrene)-b-polydiene-b-poly(α-methylstyrene) triblock copolymer whose central diene elastomer block is also free of α-methylstyrene.

The person skilled in the art will understand that depending on the method and conditions of synthesis of the thermoplastic elastomer, the product obtained may consist, in addition to the A-B-A triblock (or A'-B'-A' triblock), of other populations of macromolecules such as thermoplastic polymers having the microstructure of the A (or A') block, diene elastomers having the microstructure of the B (or B') block or diblock polymers of formula A-B (or A'-B'), the blocks A, A', B and B' being as defined in the present application. Thus, within the scope of the invention, the person 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 A-B-A triblock and the A’-B’-A’ triblock may comprise at most 20% by mass of a diblock polymer of formula A-B and a diblock polymer of formula A’-B’ respectively. In the same way, the product resulting from the synthesis may comprise a thermoplastic polymer having the microstructure of the A block in the case of the A-B-A triblock synthesis (or A’ in the case of the A’-B’-A’ triblock synthesis).

Polymerization can be carried out using a continuous process or a batch processing process.

The polymer composition according to the invention may further comprise at least one component chosen from non-thermoplastic elastomers, reinforcing fillers chosen 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 comprising zinc monoxide and stearic acid, guanidine derivatives, extension oils, silica covering agents.

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

Another subject 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 CARRYING OUT THE INVENTION I Tests and measurements: A – Measurement of the Mn of TPEs

The macrostructure (Mw, Mn, Ip) of TPEs is determined by size exclusion chromatography (SEC) based on 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) standards.

For these measurements, the TPE sample is first solubilized in stabilized tetrahydrofuran at a concentration of 1 g/L; then the solution is filtered with PTFE filters with a porosity of 0.45 μm before injection. The equipment used is a “WATERS alliance” chromatographic chain. 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 is used (set of three AGILENT columns). 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 chromatographic data is the “WATERS ALLIANCE” system.

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.

The calculated number-average molar masses are relative to a calibration curve produced from commercial standard polystyrenes "PSS-pskit1h-3" in the case of thermoplastic polymers comprising α-methylstyrene units alone.

The calculated number-average molar masses are relative to a calibration curve produced from commercial standard polybutadienes "PSS-bdfkit" in the case of products comprising diblock and/or triblock thermoplastic elastomers containing butadiene units.

In the case of products resulting from the synthesis of thermoplastic block elastomers (thermoplastic block comprising α-methylstyrene units—b—polydiene—b—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 of the product is carried out 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 of the chromatogram.

In the case of products containing more than 10% by mass of thermoplastic polymer comprising poly(α-methylstyrene) units, the distribution of the different species of the product is carried out 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 metered addition of thermoplastic polymer comprising poly(α-methylstyrene) units, in a manner known to those skilled in the art.

B – Differential scanning calorimetry (DSC) of TPEs

The characterization of the Tg of the elastomer block and the thermoplastic blocks of the first and second thermoplastic elastomers TPE1 and TPE2 is carried out by DSC measurement (DSC1 device from Mettler Toledo). The device is operated under a helium atmosphere. A sample of 10 to 20 mg of thermoplastic elastomer is placed in a crucible conventionally used by those skilled in the art to carry out Tg measurements.

The sample is first placed in an isothermal state at +25°C for 2 minutes and then cooled to -150°C at a rate of 50°C per minute. An isothermal state is then applied at -150°C for 10 minutes. An initial heating 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 is then quenched to reach -150°C at the maximum rate allowed by the device. The sample is then kept in an isothermal state at -150°C for 15 minutes. The second heating then begins from -150°C to +10°C at a speed of 20°C per minute (Tg measurement range of the elastomer part of the TPE) and continues from +10°C to +250°C at a speed of 50°C per minute (Tg measurement range of the thermoplastic blocks). In this measurement only the second heating is used.

C – Proton Nuclear Magnetic Resonance (NMR ¹ H)

The determinations of the levels of the different monomer units within thermoplastic elastomers are carried out by NMR analysis. The spectra are acquired on a 500MHz BRUKER spectrometer equipped with a "Broad Band" BBIz-grad 5mm probe. The quantitative ¹ H NMR experiment uses a simple 30° pulse sequence and a repetition delay of 5 seconds between each acquisition. The samples are solubilized in CDCl ₃ . The integration zones considered for quantification are the spectral signature zones of the monomer units known to those skilled in the art.

D- RPA viscosity measurement ( Rubber Process Analyzer )

The method for measuring G’ and G’’ uses an RPA type oscillating disc rheology apparatus, such as the 2000LV device (Oscillating Disc Rheometer) supplied by Alpha Technologies®, equipped with the standard 200 in. lbs (22.6 dNm) viscosity sensor. The RPA machine allows torsional stress to be applied to a material sample enclosed in a chamber (or enclosure) with biconical walls.

To measure G'(T) (elastic shear modulus), a sample of material about 30 mm in diameter and weighing about 5 g is placed in the RPA enclosure or chamber (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 enclosure and is visible at the end of the test). At the end of this operation, the sample is perfectly molded in the closed RPA enclosure.

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

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

We obtain a curve of variation of G’ as a function of temperature, from which we can extract the G’ modulus of the composition at 190°C.

The shaping and measuring steps of G’ are done without intervention, by programming the RPA machine.

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.

E- Measurement of the complex dynamic shear modulus

Dynamic properties (after forming): Tensile test

The dynamic properties G*(10%) at 23°C are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a crosslinked composition sample (cylindrical specimen 4 mm thick and 400 mm² in cross-section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under the defined temperature conditions, for example at 23°C according to the ASTM D 1349-99 standard, or depending on the case at a different temperature. A strain amplitude sweep is carried out from 0.1 to 50% (forward cycle), then from 50% to 1% (return cycle). The results used concern the complex dynamic shear modulus G*. For the return cycle, the value of the complex dynamic shear modulus G*(10%) at 10% deformation, at 23°C, is indicated.

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 rigidity of the material: the lower G* 10% at 23°C, the lower the rigidity.

II. Synthesis of polymers and preparation of polymer compositions

In the following tests we will adopt the following denomination:

poly(α-methylstyrene) = PAMS
polyether-polyamide block copolymer (copoly(ether-b-amide)) = PEBA

A- The first thermoplastic elastomer TPE1

A-1 Synthesis of a triblock polymer poly(α-methylstyrene) -b-polybutadiene-b-poly(α-methylstyrene) or TPE1 1

In an 80 L reactor equipped with a double jacket, 2.0 L of cyclohexane, 0.106 L of tetrahydrofuran and 5 kg of α-methylstyrene were successively introduced under constant nitrogen scavenging. All products were previously purified and/or dried.

After the temperature has been brought to 17°C, 0.125 mol of sec-butyllithium is introduced into the reactor in the form of 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.

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

At the end of this coupling step, a poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer is synthesized. 0.2 pce of an antioxidant, Irganox 1520L® (from BASF), is then added. The antioxidized polymer is separated from the solvent by steam stripping, and the polymer is then dried in a vacuum oven under nitrogen sparging at 60°C.

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

HAS - 2 - Synthesis of a second triblock polymer poly(α-methylstyrene)-b-poly(butadiene-co-styrene)-b-poly(α-methylstyrene) (or TPE 1 2)

In an 80 L reactor equipped with a double jacket, 2.6 L of cyclohexane, 0.028 L of tetrahydrofuran and 2 kg of alphamethylstyrene were successively introduced under constant nitrogen flow. All products were previously purified and/or dried.

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

After 40 minutes of polymerization, the measured conversion is 34%, 0.567 kg of 1,3-butadiene and 0.24 kg of styrene are introduced, after which the reaction mixture is diluted with 43.6 L of cyclohexane. Then 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 temperature of 42°C. The polymerization lasts 85 minutes. The measured conversion is 68%.

After polymerization, 0.072 moles of dimethyldichlorosilane are added with constant stirring. The reaction medium is maintained at 40°C for 30 minutes.

At the end of this coupling step, a poly(α-methylstyrene)-b-butadiene-styrene-b-poly(α-methylstyrene) triblock polymer is synthesized. 0.2 pce of an antioxidant, Irganox 1520L® (from BASF), is added. The antioxidized polymer is separated from the solvent by steam stripping, then the polymer is dried in a vacuum oven under nitrogen sparging at 60°C.

The DSC Tg of the flexible poly(butadiene-co-styrene) block -48°C (ΔT, glass transition width, being equal to 9°C).

B- The second thermoplastic elastomer TPE2

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 soft polyether blocks and rigid thermoplastic polyamide blocks.

The characteristics of commercial “PEBAX” are given on the HAL theses website (Christopher CLOSA, HAL Id: tel-03794048).

C- Plasticizing hydrocarbon resin

The resins used in the tests were chosen from the resins with the 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

Introduce TPE1 and TPE2 into an internal mixer with a volume equal to 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 temperature for at least four minutes.

Table 1 summarizes the components of the polymer compositions, their characteristics and respective rates.

[Table 1]: Mn (Kg/mol) Tg (°C)/ Tf (°C) M1 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 Resin
PICCOTAC 8090 0.850 44 22.3 22.3 22.3 22.3 22.3

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

* 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)

Tables 2 and 3 show the characteristics and microstructures of the TPEs used in the examples.

Sample name Mn PAMS block
PS Calibration PAMS/dibloc/tribloc species distribution
(PB calibration) Mp PAMS % mass PAMS % mass dibloc % mass triblock TPE11 14000 8300 2.6 11.4 86 TPE12 12400 8200 3.6 7.9 88.5

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- unit
% PB 1.4 = mass percentage of butadiene units in the form of 1.4 unit
% AMS = mass percentage of α-methylstyrene units
Mp = peak mass
% mass = mass percentage.

Sample name Mn block P olether (g/mol) Mn TP block
(g/mol) % P olether %TP TPE2-1* 2000 600 77 23 TPE2-2** 1500 1000 43 57

* 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)

The characteristics of these commercial “PEBAX” are given on the HAL theses site (Christopher CLOSA, HAL Id: tel-03794048).

D – Results of the measurements taken

Table 4 shows the results of the measurements made on the different polymer compositions, M1 to M5.

M1 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

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

Claims (16)

Polymer composition comprising a first thermoplastic elastomer and a second thermoplastic elastomer,
which first thermoplastic is
a thermoplastic elastomer with TPE11 blocks 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 the diene units relative to the mass of the diene elastomer block, or
a thermoplastic elastomer with TPE12 blocks of formula A'-B'-A', in which A' is a thermoplastic block comprising predominantly in moles α-methylstyrene units and B' is a random copolymer elastomer block comprising diene units and vinylaromatic units, or
a blend of the two thermoplastic block elastomers TPE11 and TPE12,
which second thermoplastic elastomer comprises at least one polyether elastomer block and at least one thermoplastic block, TP block, which TP block has a melting temperature, Tf, within a range from 130°C to 190°C. Composition according to claim 1, in which the thermoplastic blocks A and A’ comprise more than 95 mol% of α-methylstyrene units. Composition according to claim 1 or 2 in which the thermoplastic blocks A and A’ are homopolymers of α-methylstyrene. Composition according to any one of the preceding claims in which the thermoplastic blocks A and A', independently of one another, represent at least 10% by mass respectively relative to the mass of TPE11 and to the mass of TPE12, preferably from 10 to 45% by mass respectively relative to the mass of TPE11 and to the mass of TPE12, more preferably from 10% to 40% by mass respectively relative to the mass of TPE11 and to the mass of TPE12. Composition according to any one of the preceding claims in which the elastomer block B comprises from 0 to less than 5% by mass of units of one or more vinylaromatic monomers. Composition according to claim 5 in which the units of one or more vinylaromatic monomers of block B are chosen from styrene units, α-methylstyrene units and their mixture. Composition according to any one of the preceding claims in which the elastomer block B is a polybutadiene block (BR). Composition according to any one of the preceding claims 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 the block B'. Composition according to any one of the preceding claims in which the vinylaromatic units of block B' are styrene units. Composition according to any one of the preceding embodiments in which the elastomer block B' comprises 1,3-butadiene units and styrene units. Composition according to any one of the preceding embodiments in which the elastomer block B' is a random copolymer of 1,3-butadiene and styrene. Composition according to any one of the preceding claims, in which the thermoplastic block(s) of the second thermoplastic elastomer are chosen from the group consisting of polyamides. Composition according to any one of the preceding claims, in which the mass fraction of the thermoplastic block (TP) in the second thermoplastic elastomer is within a range from 15% to 60%, preferably from 20% to 50%. Composition according to any one of the preceding claims, in which the second thermoplastic elastomer is chosen from the group consisting of block copolymers composed of polyether blocks and polyamide blocks (PEBA). Composition according to any one of the preceding claims, in which the level of the first thermoplastic elastomer in the composition is within a range of 50 to 96 phr, preferably 60 to 80 phr and the level of the second thermoplastic elastomer in the composition is within a range of 4 to 50 phr. 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.