Elastomer matrix comprising thermoplastic elastomer

Abstract

The present invention relates to an elastomer matrix comprising:-a triblock thermoplastic elastomer having a central diene elastomer block and two terminal thermoplastic blocks comprising alpha-methylstyrene units bonded to the diene elastomer block, from 2% to 10% by weight, relative to the total weight of the elastomer matrix, of a diblock thermoplastic elastomer having a diene elastomer block and a thermoplastic block comprising alpha-methylstyrene units, -greater than 10% by weight, relative to the total weight of the elastomer matrix, of a thermoplastic polymer comprising alpha-methylstyrene units, the content of thermoplastic blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer being at least 10% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer; the content of thermoplastic chains comprising alpha-methylstyrene units is at most 55% by weight with respect to the total weight of the elastomer matrix, wherein the thermoplastic chain comprising alpha-methylstyrene units consists of a chain of a thermoplastic polymer comprising alpha-methylstyrene units and a chain of thermoplastic blocks of a triblock thermoplastic elastomer and a diblock thermoplastic elastomer.

Description

Technical Field

[0001] The invention relates to an elastomeric matrix comprising a triblock thermoplastic elastomer having a diene elastomer block and two thermoplastic blocks comprising α-methylstyrene units. Background Art

[0002] In the field of motor vehicle tires, the Applicant Company has in the past developed rubber compositions comprising thermoplastic elastomers. These tires exhibit a very good compromise in terms of grip and rolling resistance performance qualities.

[0003] Thermoplastic elastomers (TPEs) are elastomers of great interest in many fields because they combine the properties associated with elastomer blocks on the one hand and with rigid thermoplastic blocks on the other. In addition, the association of the rigid thermoplastic blocks with each other gives the material the behavior of a crosslinked elastomer. This is because the rigid nodes formed by the areas where the thermoplastic blocks are associated with each other act as crosslinking nodes. Therefore, the material is rigid and does not flow. On the other hand, when the temperature rises above the glass transition temperature or melting point of the rigid blocks, the polymer will be able to flow, making it possible to shape the material. When the temperature returns to a level below the operating temperature of the Tg of the thermoplastic blocks, the polymer regains its rigidity. This significant feature of TPE means that it has a very wide range of application potential.

[0004] These thermoplastic elastomers include copolymers with poly(α-methylstyrene) blocks, which have the advantage of having higher hot strength because the rigid block is a poly(α-methylstyrene) block with a high Tg of about 150° C. to 170° C. These thermoplastic elastomers are widely described in the prior art, academic literature or patent literature. Among these thermoplastic elastomers, some are described as having a thermoplastic block, which is a copolymer of α-methylstyrene and another monomer (such as styrene), as described, for example, in WO 2007112232A2. Other documents describe TPEs whose thermoplastic blocks consist only of units derived from α-methylstyrene, such as FR 2243214.

[0005] It is also described to achieve various purposes based on a polymer composition of a copolymer with a poly (alpha-methylstyrene) block. Therefore, EP 1498455 A1 describes a polymer composition, the polymer composition includes a block thermoplastic elastomer, an acrylic resin and a plasticizer, a block of the block thermoplastic elastomer is mainly composed of alpha-methylstyrene, and a block is composed of a conjugated diene. For its part, EP 2955203 A1 describes a polymer composition, the polymer composition includes a block thermoplastic elastomer and another thermoplastic elastomer related to polypropylene and polyethylene, a block of the block thermoplastic elastomer is mainly composed of alpha-methylstyrene, and a block is composed of a conjugated diene. In addition, WO 2020136194 describes a polymer composition, the polymer composition includes a block thermoplastic elastomer and a plasticizer selected from oligobutadiene, a block of the block thermoplastic elastomer is mainly composed of alpha-methylstyrene, and a block is composed of a conjugated diene.

[0006] In this prior art, great importance is attached to the physical properties of the polymer composition, in particular the mechanical properties, such as scratch resistance, wear resistance, flexibility, rigidity and mechanical strength. In addition, EP 1498455 A1, paragraph

[0053] , EP 2955203 A1, paragraph

[0043] and FR 2243214, page 3, line 17 remind the reader that in the synthesis of copolymers with poly(alpha-methylstyrene) blocks, it is recommended to carefully choose the operating conditions in order to minimize the deactivation of the poly(alpha-methylstyrene) chains during their synthesis stage, so as to minimize the amount of free poly(alpha-methylstyrene) in the final product. This is because the poly(alpha-methylstyrene) polymer is described as an impurity that may impair the mechanical properties of the final product.

[0007] A constant goal of tire manufacturers is to reduce the rolling resistance of tires. A prerequisite for improving rolling resistance is to reduce hysteresis losses. However, the reduction of hysteresis (and therefore the improvement of hysteresis properties) is not a goal specific to the tire field, but can also have many advantages in other fields where hysteresis materials are used.

[0008] It is therefore an object of the present invention to reduce the hysteresis of materials based on thermoplastic elastomers having a thermoplastic block comprising α-methylstyrene units.

[0009] The purpose of reducing hysteresis (improving hysteresis properties) is achieved by combining in certain proportions a thermoplastic polymer comprising α-methylstyrene units with a triblock thermoplastic elastomer comprising a diene elastomer block and two terminal thermoplastic blocks comprising α-methylstyrene units.

[0010] This is because the inventors have been able to demonstrate that, surprisingly, at the same total content of thermoplastic chains based on alpha-methylstyrene, a content of greater than 10% by weight of thermoplastic polymer based on alpha-methylstyrene in an elastomeric matrix based on block thermoplastic elastomers whose thermoplastic blocks are based on alpha-methylstyrene enables a significant reduction in hysteresis compared to elastomeric matrices comprising lower contents of such thermoplastic polymers and therefore enables an improvement in the hysteresis properties of the elastomeric matrix.

[0011] The subject of the present invention is therefore an elastomeric matrix comprising a first polymer that is a block thermoplastic elastomer having a diene elastomer block and two thermoplastic blocks comprising α-methylstyrene units, 2% to 20% by weight of a second polymer, relative to the total weight of the elastomeric matrix, and greater than 10% by weight of a third polymer, the first polymer being a block thermoplastic elastomer having a diene elastomer block and a thermoplastic block comprising α-methylstyrene units, the second polymer being a block thermoplastic elastomer having a diene elastomer block and a thermoplastic block comprising α-methylstyrene units, and the third polymer being a thermoplastic polymer comprising α-methylstyrene units. Summary of the invention

[0012] The subject matter of the invention described in more detail below is at least one of the embodiments listed in the following points:

[0013] 1-An elastomeric matrix, the elastomeric matrix comprising

[0014] a triblock thermoplastic elastomer having a central diene elastomeric block and two terminal thermoplastic blocks comprising α-methylstyrene units bonded to said diene elastomeric block,

[0015] - 2% to 20% by weight, relative to the total weight of the elastomeric matrix, of a diblock thermoplastic elastomer having a diene elastomeric block and a thermoplastic block comprising α-methylstyrene units,

[0016] - greater than 10% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising alpha-methylstyrene units,

[0017] The content of the thermoplastic block of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

[0018] The content of thermoplastic chains comprising α-methylstyrene units is up to 55% by weight, relative to the total weight of the elastomeric matrix.

[0019] The thermoplastic chain comprising α-methylstyrene units is constituted by a chain of a thermoplastic polymer comprising α-methylstyrene units and a chain of a thermoplastic block of a triblock thermoplastic elastomer and a diblock thermoplastic elastomer.

[0020] 2- Elastomeric matrix according to the preceding embodiment, characterized in that it comprises up to 45% by weight of thermoplastic polymer comprising alpha-methylstyrene units, relative to the total weight of the elastomeric matrix.

[0021] 3. Elastomeric matrix according to any of the preceding embodiments, characterized in that it comprises at least 20% by weight, preferably at least 25% by weight, of thermoplastic chains comprising alpha-methylstyrene units, relative to the total weight of the elastomeric matrix.

[0022] 4- The elastomeric matrix according to any one of the preceding embodiments, characterized in that it comprises at least 15% by weight of a thermoplastic polymer comprising α-methylstyrene units, relative to the total weight of the elastomeric matrix.

[0023] 5. The elastomeric matrix according to any one of the preceding embodiments, characterized in that it essentially comprises a triblock thermoplastic elastomer having a diene elastomer block and two thermoplastic blocks comprising α-methylstyrene units bonded to the diene elastomer block.

[0024] 6. Elastomer matrix according to any of the preceding embodiments, characterized in that it comprises up to 80% by weight of a triblock thermoplastic elastomer, relative to the total weight of the elastomer matrix, wherein the triblock thermoplastic elastomer has a diene elastomer block and two thermoplastic blocks comprising α-methylstyrene units bonded to the diene elastomer block.

[0025] 7- Elastomeric matrix according to any of the preceding embodiments, characterized in that the content of thermoplastic blocks comprising α-methylstyrene units is at least 15% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

[0026] 8. Elastomer matrix according to the preceding embodiment, characterized in that the content of thermoplastic blocks comprising α-methylstyrene units is at most 45% by weight, preferably at most 40% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

[0027] 9. Elastomer matrix according to any one of the preceding embodiments, characterized in that the content of thermoplastic chains comprising α-methylstyrene units in the elastomeric matrix is ​​at most 50% by weight relative to the total weight of the elastomeric matrix.

[0028] 10 - Elastomeric matrix according to any one of the preceding embodiments, characterized in that the diene elastomer blocks comprise units derived from diene monomers having from 4 to 12 carbon atoms.

[0029] 11 - Elastomeric matrix according to any one of the preceding embodiments, characterized in that the diene elastomer blocks comprise units derived from butadiene.

[0030] 12 - Elastomeric matrix according to any one of the preceding embodiments, characterized in that the diene elastomer blocks additionally comprise units derived from vinyl aromatic monomers.

[0031] 13. The elastomeric matrix according to the preceding embodiment, characterized in that the vinyl aromatic monomer is styrene.

[0032] 14- Elastomeric matrix according to any one of the preceding embodiments, characterized in that the diene elastomer blocks are fully hydrogenated or partially hydrogenated.

[0033] 15. The elastomeric matrix according to any one of the preceding embodiments, characterized in that the thermoplastic blocks comprising α-methylstyrene units mainly comprise units derived from α-methylstyrene.

[0034] 16. Elastomeric matrix according to the preceding embodiment, characterized in that the thermoplastic blocks comprising α-methylstyrene units additionally comprise units derived from at least one other vinylaromatic monomer, preferably styrene.

[0035] 17 - Elastomeric matrix according to any one of embodiments 1 to 15, characterized in that the thermoplastic blocks comprising α-methylstyrene units consist essentially of α-methylstyrene units.

[0036] 18. The elastomeric matrix according to any one of the preceding embodiments, characterized in that the thermoplastic polymer comprising α-methylstyrene units comprises mainly units derived from α-methylstyrene.

[0037] 19. The elastomeric matrix according to any one of the preceding embodiments, characterized in that the thermoplastic polymer comprising α-methylstyrene units comprises units derived from at least one other vinyl aromatic monomer, preferably styrene.

[0038] 20. The elastomeric matrix according to any one of embodiments 1 to 18, characterized in that the thermoplastic polymer comprising α-methylstyrene units is an α-methylstyrene homopolymer.

[0039] 21- Elastomeric matrix according to any of the preceding embodiments, characterized in that at least one, preferably two, preferably three, preferably four, preferably five, preferably all of the following characteristics are observed,

[0040] - the diene blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer comprise units derived from butadiene,

[0041] - the thermoplastic blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer consist of poly(α-methylstyrene),

[0042] - the thermoplastic polymer comprising α-methylstyrene units is poly(α-methylstyrene),

[0043] - the content of the thermoplastic block comprising α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% and at most 45% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer,

[0044] - the said matrix comprises more than 10% by weight, preferably at least 15% by weight and at most 45% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising α-methylstyrene units,

[0045] The content of thermoplastic chains comprising α-methylstyrene units is at least 20% and at most 55% by weight, relative to the total weight of the elastomeric matrix.

[0046] definition

[0047] In the present application, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by weight.

[0048] Furthermore, any numerical interval represented by the expression "between a and b" means a range within the limits a and b (i.e., excluding the limits a and b), while any numerical interval represented by the expression "from a to b" means a numerical range extending from a to b (i.e., including the strict limits a and b).

[0049] In the present patent application, "predominantly" or "mainly" in relation to a compound is understood to mean that among the compounds of the same type of the composition, the compound is predominant, i.e., among the compounds of the same type, it is the compound which represents the largest weight fraction. Thus, the unit resulting from the "main" monomer in a polymer is the unit which represents the largest weight fraction of the units constituting the polymer, relative to the total weight of said polymer. Alternatively, a component is "predominant" in a composition when it represents the largest weight fraction of the ingredients constituting the composition, relative to the total weight of the composition. In a system comprising only one specific type of element, said element is predominant within the meaning of the present invention.

[0050] In the present patent application, "elastomeric matrix" is understood to mean a mixture consisting of polymers and exhibiting elastomeric properties.

[0051] Poly(α-methylstyrene) is generally understood to mean α-methylstyrene homopolymer.

[0052] In the present patent application, “thermoplastic chains comprising α-methylstyrene units” are understood to mean chains of thermoplastic polymers comprising α-methylstyrene units and chains of thermoplastic blocks of triblock thermoplastic elastomers and diblock thermoplastic elastomers comprising α-methylstyrene units.

[0053] The carbon-containing compounds mentioned in the specification may be compounds of fossil origin or bio-based compounds. In the case of bio-based compounds, they may be derived partly or completely from biomass, or may be obtained partly or completely from renewable starting materials derived from biomass. In the same way, the compounds mentioned may also be derived from the recovery of previously used materials, i.e. they may be derived partly or completely from a recovery process, or may be obtained partly or completely from starting materials that themselves are derived from a recovery process. In particular, monomers, polymers, etc. are concerned. DETAILED DESCRIPTION

[0054] The present invention relates to an elastomeric matrix comprising:

[0055] a triblock thermoplastic elastomer having a central diene elastomeric block and two terminal thermoplastic blocks comprising α-methylstyrene units bonded to said diene elastomeric block,

[0056] - 2% to 20% by weight, relative to the total weight of the elastomeric matrix, of a diblock thermoplastic elastomer having a diene elastomeric block and a thermoplastic block comprising α-methylstyrene units,

[0057] - greater than 10% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising alpha-methylstyrene units,

[0058] The content of the thermoplastic block of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

[0059] The content of thermoplastic chains comprising α-methylstyrene units is up to 55% by weight, relative to the total weight of the elastomeric matrix.

[0060] The thermoplastic chain comprising α-methylstyrene units is constituted by the chain of the thermoplastic polymer comprising α-methylstyrene units and the chain of the thermoplastic blocks comprising α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

[0061] A-Elastomer Matrix

[0062] The combination of features related to the content of segmented thermoplastic elastomer and thermoplastic polymer, the content of thermoplastic blocks and the content of thermoplastic chains within the elastomeric matrix makes it possible to combine the elastomeric properties and the thermoplastic characteristics of the matrix while achieving a significant reduction in hysteresis compared to a matrix containing the same total content of thermoplastic chains but less thermoplastic polymer.

[0063] According to the invention, the elastomeric matrix comprises a triblock thermoplastic elastomer having a central diene elastomeric block and two terminal thermoplastic blocks comprising α-methylstyrene units bonded to the diene elastomeric block.

[0064] The minimum content of triblock thermoplastic elastomer in the elastomer matrix is ​​determined by the properties associated with the diene elastomer block. The elastomer matrix must have elastomeric properties. According to certain embodiments of the present invention, the triblock thermoplastic elastomer is the main component of the elastomer matrix by weight, that is, the weight fraction of the triblock thermoplastic elastomer is the largest in the polymer constituting the matrix. According to these embodiments, the triblock thermoplastic elastomer may be present in the elastomer matrix in a proportion of at least 50% by weight, preferably at least 65% by weight, relative to the total weight of the elastomer matrix. The content of the triblock thermoplastic elastomer is at most 88% by weight of the total weight of the elastomer matrix. According to certain embodiments, the content is advantageously at most 80% by weight of the total weight of the elastomer matrix.

[0065] According to the invention, the elastomeric matrix also comprises from 2% to 20% by weight, relative to the total weight of the elastomeric matrix, of a diblock polymer composed of a diene elastomeric block and a thermoplastic block comprising α-methylstyrene units.

[0066] According to the invention, in the elastomer matrix, these thermoplastic blocks of block elastomers comprising α-methylstyrene units represent at least 10% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer. Thermoplastic polymers comprising α-methylstyrene units, which are another component of the elastomer matrix, are not considered to be thermoplastic blocks according to the invention. In other words, according to the invention, thermoplastic blocks comprising α-methylstyrene units represent at least 10% by weight relative to the weight of the block polymers of the matrix.

[0067] Preferably, the thermoplastic block containing α-methylstyrene units accounts for up to 45% by weight, preferably up to 40% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer. Above 45% by weight, the elastomeric properties of the thermoplastic elastomer that can be used according to the invention may be reduced.

[0068] According to the invention, the elastomeric matrix also contains a thermoplastic polymer comprising alpha-methylstyrene units, the proportion of which is greater than 10% by weight relative to the total weight of the elastomeric matrix. An improvement in the hysteresis properties is observed when the thermoplastic polymer comprising alpha-methylstyrene units exceeds 10% by weight, relative to a matrix comprising the same content of thermoplastic chains but with less than 10% by weight of thermoplastic polymer comprising alpha-methylstyrene units.

[0069] According to one embodiment of the invention, the elastomeric matrix comprises at most 45% by weight of a thermoplastic polymer comprising alpha-methylstyrene units, relative to the total weight of the elastomeric matrix. This is because, as will be understood by a person skilled in the art, the matrix according to the invention exhibits elastomeric properties and that, exceeding 45% by weight, the compromise of properties related to elastomeric characteristics deteriorates.

[0070] According to a particular embodiment of the invention, the elastomeric matrix comprises at least 15% by weight of thermoplastic polymer comprising α-methylstyrene units, relative to the total weight of the elastomeric matrix.

[0071] According to a particular embodiment of the invention, the content of thermoplastic polymer comprising α-methylstyrene units in the elastomeric matrix is ​​greater than 10% by weight, in particular at least 15% and at most 45% by weight, relative to the total weight of the elastomeric matrix.

[0072] The content of thermoplastic chains comprising α-methylstyrene units in the elastomeric matrix according to the invention is at most 55% by weight, preferably at most 50% by weight, relative to the total weight of the elastomeric matrix. "Thermoplastic chains comprising α-methylstyrene units" is understood to mean all thermoplastic chains consisting of chains of thermoplastic polymers comprising α-methylstyrene units and chains of thermoplastic blocks of triblock thermoplastic elastomers and diblock thermoplastic elastomers comprising α-methylstyrene units. When exceeding 55% by weight, the elastomeric properties of the matrix may deteriorate and the properties related to elasticity may also deteriorate.

[0073] According to an embodiment of the invention, the elastomeric matrix according to the invention has a content of thermoplastic chains comprising alpha-methylstyrene units of at least 20% by weight relative to the total weight of the elastomeric matrix. According to some of these embodiments, the content of thermoplastic chains comprising alpha-methylstyrene units may be at least 25% by weight relative to the total weight of the elastomeric matrix.

[0074] B-Block Polymer:

[0075] The triblock thermoplastic elastomer and the diblock thermoplastic elastomer of the elastomeric matrix according to the invention are composed of three polymer blocks and two polymer blocks, respectively. The triblock thermoplastic elastomer has a central diene elastomer block. The properties of the diene elastomer block of the diblock thermoplastic elastomer may be the same as the properties of the diene elastomer block of the triblock thermoplastic elastomer.

[0076] A diene elastomer is understood to mean an elastomer resulting at least partly (ie, homopolymer or copolymer) from diene monomers (monomers carrying two conjugated or non-conjugated carbon-carbon double bonds).

[0077] According to a preferred embodiment of the invention, diene elastomer is understood to mean any homopolymer obtained by polymerization of conjugated diene monomers having from 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes having from 4 to 12 carbon atoms with one another or of one or more vinyl aromatic compounds having from 8 to 20 carbon atoms.

[0078] The following are particularly suitable as conjugated dienes which can be used according to the invention: 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(C 1 -C 5 alkyl)-1,3-butadiene (e.g., 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene or 2-methyl-3-isopropyl-1,3-butadiene), phenyl-1,3-butadiene, 1,3-pentadiene and 2,4-hexadiene.

[0079] According to one embodiment of the invention, the diene elastomer comprises units derived from 1,3-diene monomers having from 4 to 12 carbon atoms; more particularly, the diene elastomer comprises units derived from butadiene or isoprene.

[0080] The following are particularly suitable as vinylaromatic compounds: styrene, α-methylstyrene, o-, m- or p-methylstyrene, the “vinyltoluene” commercial mixtures, p-(tert-butyl)styrene, methoxystyrene, vinylmesitylene, divinylbenzene and vinylnaphthalene.

[0081] According to one embodiment of the invention, the diene elastomer additionally comprises units arising from vinyl aromatic monomers, more particularly styrene.

[0082] The diene elastomer is preferably a polybutadiene (BR), a synthetic polyisoprene (IR), a butadiene copolymer, in particular a copolymer of butadiene and of a vinyl aromatic monomer, in particular styrene, or an isoprene copolymer. According to one embodiment, the diene elastomer is a polybutadiene or a butadiene copolymer.

[0083] The diene elastomer may have any microstructure depending on the polymerization conditions used.The diene elastomer may also be coupled or star-branched by means of coupling agents or star-branching agents with or without functional groups.

[0084] According to one embodiment of the invention, the diene elastomer constituting the central block of the thermoplastic elastomer is fully hydrogenated or partially hydrogenated. Partial hydrogenation is generally preferred when subsequent crosslinking of the thermoplastic elastomer is envisaged via the carbon-carbon double bonds of the elastomer. Full hydrogenation is also envisaged, in particular with regard to the formation of rigid nodules formed by the zones where the thermoplastic blocks are united to one another, which act as crosslinking nodes.

[0085] In summary, preferably, for the present invention, the number-average molar mass (M n ) is 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, in order to impart good elastomeric properties and satisfactory mechanical strength to the thermoplastic elastomer. The number-average molar mass of the diene elastomeric block of the thermoplastic elastomer can be determined by size exclusion chromatography in a manner known to a person skilled in the art using a calibration curve generated from diene standards.

[0086] According to a particular embodiment, the diene elastomeric block of the triblock thermoplastic elastomer and the diene elastomeric block of the diblock thermoplastic elastomer have identical properties, that is, they have the same microstructure and the same macrostructure.

[0087] The thermoplastic elastomer of the elastomeric matrix according to the invention comprises two terminal thermoplastic blocks comprising α-methylstyrene units.

[0088] In the context of the present invention, a thermoplastic block comprising α-methylstyrene units is understood to mean a thermoplastic block comprising units derived from α-methylstyrene and having a glass transition temperature greater than or equal to 100° C., preferably at least 120° C. and at most 180° C. The Tg of the thermoplastic block is measured according to the method described below.

[0089] In summary, preferably, the number average molar mass (M n ) is at least 5000 g / mol, preferably at least 7000 g / mol and at most 100000 g / mol, preferably at most 50000 g / mol. The number average molar mass of the thermoplastic block of the thermoplastic elastomer can be determined by size exclusion chromatography in a manner known to the person skilled in the art and is expressed here relative to polystyrene standards.

[0090] According to a preferred embodiment of the present invention, the thermoplastic block containing α-methylstyrene units of the thermoplastic elastomer mainly contains units derived from α-methylstyrene, thereby imparting good heat resistance to the thermoplastic elastomer and the elastomer matrix. In other words, according to this embodiment, each thermoplastic block preferably contains at least 50% by weight, preferably at least 70% by weight, of units derived from α-methylstyrene monomers.

[0091] When the thermoplastic block of the thermoplastic elastomer comprising α-methylstyrene units additionally comprises units derived from at least one other monomer, the other monomer may be a vinyl aromatic monomer, preferably styrene.

[0092] According to a particularly advantageous embodiment, the thermoplastic block of the thermoplastic elastomer consists essentially of α-methylstyrene units, that is to say, the thermoplastic block contains no units derived from monomers other than α-methylstyrene. Thus, better heat resistance of the thermoplastic elastomer and the elastomeric matrix at higher temperatures is observed.

[0093] The minimum content of the thermoplastic block in the thermoplastic elastomer may vary depending on the use conditions of the thermoplastic elastomer.

[0094] On the other hand, the ability of the thermoplastic elastomer to deform during the manufacture of the object may also contribute to determining the proportion of thermoplastic blocks in the thermoplastic elastomer that can be used according to the invention.

[0095] According to the invention, the thermoplastic block comprising α-methylstyrene units represents at least 10% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer of the elastomeric matrix. According to certain embodiments of the invention, the thermoplastic block comprising α-methylstyrene units represents at least 15% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer of the elastomeric matrix.

[0096] According to one embodiment of the invention, the thermoplastic block comprising α-methylstyrene units represents at most 45% by weight, preferably at most 40% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer of the elastomeric matrix.

[0097] The triblock thermoplastic elastomers and diblock thermoplastic elastomers according to the invention can be produced in a known manner according to various synthesis methods described in the prior art.

[0098] A method for synthesizing a triblock thermoplastic elastomer includes, for example, anionic polymerization of α-methylstyrene in the presence of polydienyl dilithium as a polymerization initiator to form two thermoplastic blocks simultaneously. For example, WO 8505116A1 and EP 0014947 A1 describe these methods, which include copolymerization of styrene and α-methylstyrene to produce thermoplastic blocks. Thus, a triblock copolymer of the type of poly(α-methylstyrene-to-styrene)-b-polydiene-b-poly(α-methylstyrene-to-styrene) is obtained. A similar synthesis method can be envisioned to manufacture a triblock polymer of poly(α-methylstyrene)-b-polydiene-poly(α-methylstyrene) using polydienyl lithium as a polymerization initiator. This method is described, for example, in FR 3045615.

[0099] Other synthesis methods consist in polymerizing α-methylstyrene anionically in a first step. Then, in a second stage, diene monomers are polymerized on the living chains obtained comprising α-methylstyrene units. Thus, a (thermoplastic block comprising α-methylstyrene units)-b-polydiene block diblock polymer is obtained, the diene ends of which are active. The polymer reaction can usually be stopped at this point by adding a protic compound, and the diblock diene elastomer can then be recovered.

[0100] Alternatively, according to this other synthesis method, in order to obtain a triblock thermoplastic elastomer, a coupling agent is added at this time to couple the diene blocks of the chain, whose diene ends are reactive. This stage is carried out in a manner known per se. The coupling agent generally comprises a silicon atom or a tin atom, substituted by at least two reactive groups relative to the carbon anion ends of the active polymer chain. As an example of a coupling agent, a coupling agent with two reactive groups can be mentioned, such as a dihalogenated tin compound and a dihalogenated silane compound (particularly dibutyltin dichloride or dimethyldichlorosilane) or a dialkoxysilane. At the end of this coupling stage, a (thermoplastic block comprising α-methylstyrene units)-b-polydiene block-b-(thermoplastic block comprising α-methylstyrene units) triblock is formed.

[0101] A person skilled in the art will understand that, depending on the operating conditions according to this last synthesis method, said method may result in a product consisting of a mixture containing, in addition to the (thermoplastic block comprising α-methylstyrene units)-b-diene elastomer block-b-(thermoplastic block comprising α-methylstyrene units) triblock, other macromolecular populations, such as thermoplastic polymers comprising α-methylstyrene units and (thermoplastic block comprising α-methylstyrene units)-b-diene elastomer block diblock polymers. A person skilled in the art knows how to determine the synthesis conditions in order to promote the formation of certain populations rather than others. For example, a person skilled in the art can achieve the target content of triblock thermoplastic elastomer and diblock thermoplastic elastomer, respectively, by specifically adjusting the amount and nature of the coupling agent.

[0102] Such a method for synthesizing block thermoplastic elastomers is described, for example, in US 4302559 A. The synthesis of block copolymers includes a first stage of polymerization of alpha-methylstyrene at low temperatures in the presence of a polar agent. In the second stage, a small amount of conjugated diene is added to obtain an active polydiene-based block, thereby avoiding the depolymerization of alpha-methylstyrene. In the third stage, in the presence of another polar compound, the addition of conjugated diene monomers can randomly insert residual alpha-methylstyrene. In order to obtain a triblock copolymer, a coupling agent is used to couple the polymer obtained in the last polymerization stage. According to the synthetic method, the central diene elastomer block of the triblock copolymer is a random poly (butadiene-to-alpha-methylstyrene) copolymer.

[0103] Other processes using this method of synthesizing poly(α-methylstyrene)-b-polydiene-b-poly(α-methylstyrene) triblock copolymers are described, which make it possible to obtain a central diene elastomer block free of α-methylstyrene. For example, in document FR 2243214, the process comprises homopolymerizing α-methylstyrene in a concentrated medium at a temperature between 0° C. and 40° C. in a first stage. At the end of this stage, the conjugated diene and solvent required for the synthesis of the poly(conjugated diene) block are added. At the end of this last polymerization stage, the polymer obtained is coupled using a coupling agent. Recently, WO 2020070406A1 describes another process capable of synthesizing poly(α-methylstyrene)-b-polydiene-b-poly(α-methylstyrene) triblock copolymers, the central diene elastomer block of which also does not contain α-methylstyrene.

[0104] In the context of the present invention, the elastomeric matrix may comprise one or more triblock thermoplastic elastomers having a central diene elastomer block and two terminal thermoplastic blocks comprising α-methylstyrene units. In the same way, the elastomeric matrix may comprise from 2% to 20% by weight of one or more diblock thermoplastic elastomers having a diene elastomer block and a thermoplastic block comprising α-methylstyrene units.

[0105] C - Thermoplastic polymer containing α-methylstyrene units

[0106] In the elastomeric matrix according to the invention, the thermoplastic polymer comprising α-methylstyrene units may have the same properties as the terminal thermoplastic block of the triblock thermoplastic elastomer or different properties.

[0107] The thermoplastic polymer comprising α-methylstyrene units may additionally comprise units derived from at least one other monomer, provided that the polymer retains its thermoplastic behavior. The other monomer may be a vinyl aromatic monomer as defined above. According to this embodiment of the invention, the other monomer is preferably styrene.

[0108] According to a preferred embodiment, the thermoplastic polymer mainly comprises units derived from alpha-methylstyrene, in order to impart good heat resistance to the elastomeric matrix according to the invention. According to this embodiment, the thermoplastic polymer preferably comprises at least 50% by weight, preferably at least 70% by weight, of units derived from alpha-methylstyrene monomers. More particularly, according to this embodiment, the thermoplastic polymer is advantageously an alpha-methylstyrene homopolymer.

[0109] Preferably, the number average molar mass (M n ) is at least 5000 g / mol and at most 150000 g / mol, preferably at most 100000 g / mol, more preferably at most 50000 g / mol. The number average molar mass of the thermoplastic polymer can be measured by size exclusion chromatography in a manner known to those skilled in the art using a calibration curve generated from polystyrene standards.

[0110] In the context of the present invention, the glass transition temperature of the thermoplastic polymer comprising α-methylstyrene units is greater than or equal to 100° C., preferably at least 120° C. and at most 180° C. The Tg of the thermoplastic polymer is measured according to the method described below.

[0111] Thermoplastic polymers containing α-methylstyrene units are commercially available or can be produced in a known manner, for example by anionic polymerization of α-methylstyrene in the presence of an organometallic polymerization initiator, for example an organolithium compound, such as an alkyllithium. Document FR 2852960A1 describes a process for the synthesis of poly(α-methylstyrene).

[0112] As commercially available thermoplastic polymers comprising α-methylstyrene units, mention may be made of the thermoplastic polymers comprising α-methylstyrene units sold by ABCR.

[0113] In the context of the present invention, the elastomeric matrix may comprise one or more different thermoplastic polymers comprising α-methylstyrene units.

[0114] The individual preferred or non-preferred embodiments of the invention relating to block polymers and thermoplastic polymers can be combined with one another.

[0115] Thus, according to a particularly advantageous embodiment of the invention, the elastomeric matrix exhibits at least one, preferably two, preferably three, preferably four, preferably five, preferably six, preferably all of the following characteristics:

[0116] - the diene blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer comprise units derived from butadiene,

[0117] - the thermoplastic blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer consist of poly(α-methylstyrene),

[0118] - the thermoplastic polymer comprising α-methylstyrene units is poly(α-methylstyrene),

[0119] - the content of the thermoplastic block comprising α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% and at most 45% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer,

[0120] - the said matrix comprises more than 10% by weight, preferably at least 15% by weight and at most 45% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising α-methylstyrene units,

[0121] The content of thermoplastic chains comprising α-methylstyrene units is at least 20% and at most 55% by weight, relative to the total weight of the elastomeric matrix.

[0122] Preparation of D-elastomeric matrix

[0123] According to one embodiment, the elastomer matrix of the present invention can be obtained by blending in a solution a triblock thermoplastic elastomer, a diblock thermoplastic elastomer, and a thermoplastic polymer comprising α-methylstyrene units, which are obtained separately. According to another embodiment, a mixture of a triblock thermoplastic elastomer and a diblock thermoplastic elastomer is obtained in a single synthesis process as described above. The mixture of the diblock thermoplastic elastomer and the triblock thermoplastic elastomer is then mixed with a thermoplastic polymer comprising α-methylstyrene units. According to another embodiment, the elastomer matrix according to the present invention can be obtained in a one-pot synthesis method including anionic polymerization of α-methylstyrene in a first step. At this time, the polymerization of a portion of the chain is usually stopped by adding a protic compound to produce a thermoplastic polymer, the content of which is controlled by adjusting the amount of the protic agent. The synthesis is continued as described above to subsequently form a diblock thermoplastic elastomer and a triblock thermoplastic elastomer.

[0124] According to any of these embodiments, the polymers may be co-dissolved in a common solvent.

[0125] Alternatively, according to any of these embodiments, the polymers may be separately dissolved in the same or different but mutually miscible solvents, followed by blending of the solutions.

[0126] As the solvent, there may be mentioned any inert hydrocarbon solvent, which may be, for example, an aliphatic hydrocarbon or an alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, cyclohexane or methylcyclohexane, or an aromatic hydrocarbon such as benzene, toluene or xylene.

[0127] After blending is complete, the solvent may be removed, such as by steam stripping, at which point the elastomeric matrix may then be dried and recovered.

[0128] The elastomeric matrix according to the invention can be used in combination with one or more other compounds. The advantages resulting from the thermoplastic elastomers and the improved hysteresis properties of the elastomeric matrix according to the invention make it possible to envisage uses in many fields. Particular mention may be made of the use in the manufacture of various rubber-based products (e.g. hoses, conveyor belts, tires, tracks, shoe soles, surgical supplies, etc.).

[0129] Example

[0130] I. Description of the measurement method

[0131] A-Proton NMR ( 1 H NMR)

[0132] Spectroscopic characterization of the polymers and measurements of the microstructure were performed by liquid phase nuclear magnetic resonance (NMR) spectroscopy. Proton NMR is able to distinguish and quantify the 1,2-butadiene units, 1,4-butadiene units and α-methylstyrene units of the elastomer matrix. For these measurements, a Bruker Avance III HD ≥ 400 MHz spectrometer equipped with a Bruker BBFO z-stage 5 mm cryoprobe was used.

[0133] 1D recording using RF pulses with a tilt angle of 30° 1 H NMR experiments were performed at 25 °C with 64 repetitions and a recycle delay of 5 s.

[0134] NMR tubes were prepared so that 25 mg of sample was dissolved in 1 ml of CS 2 and add 100 μl of C 6 D 12 In δ 1H =7.18ppm relative to the solvent CS used 2 Impurity signal calibration 1 Axis of H chemical shift.

[0135] The calculations known to those skilled in the art were performed by means of 1D with the aid of Topspin software. 1 The integration of the HNMR spectrum is used to quantify the microstructure in mole percent (mol%) and weight percent (wt%). The integration area considered for the quantification is the spectral characteristic area of ​​the monomer unit known to those skilled in the art. From these calculations, the amount of thermoplastic chains containing alpha-methylstyrene units is determined.

[0136] B-Size Exclusion Chromatography (SEC):

[0137] Measurement of the molar mass of a sample

[0138] The SEC (size exclusion chromatography) technique is able to separate macromolecules in solution according to their size using a column filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest macromolecules eluting first.

[0139] SEC enables the understanding of the molar mass distribution of polymers, but is not an absolute method. Starting from commercial standard products, various number-average molar masses (M n ) and weight average molar mass (M w ) and peak molar mass (M p ), and the polydispersity index (PI = M w / M n ).

[0140] The polymer samples were not specially treated before analysis. -1 The concentration of 1.5 μM was simply dissolved in the elution solvent. The solution was then filtered through a filter with a porosity of 0.45 μm before injection.

[0141] The device used was a Waters Alliance chromatography line. The elution solvent was tetrahydrofuran protected with 250 ppm BHT (butylated hydroxytoluene) to prevent oxidation or tetrahydrofuran without an antioxidant, with a flow rate of 1 ml.min -1 , the system temperature was 35°C, and the analysis time was 45 min. The columns used were a set of three Agilent columns with the trade name Polypore or a set of four Agilent columns, two trade names PL Gel Mixed D, and two trade names PL Gel Mixed E. The injection volume of the polymer sample solution was 100 μl. The detector was a Waters 2410 differential refractometer (RI), and the software using the chromatographic data was the Waters Empower system.

[0142] In the case of thermoplastic polymers comprising only α-methylstyrene units, the calculated number-average molar masses were related to a calibration curve generated from the commercial “PSS-pskit1h-3” polystyrene standards.

[0143] In the case of products containing diblock thermoplastic elastomers and / or triblock thermoplastic elastomers comprising butadiene units, the calculated number-average molar masses are related to a calibration curve generated from the commercial "PSS-bdfkit" polybutadiene standards.

[0144] In the case of a product obtained from the synthesis of a block thermoplastic elastomer (thermoplastic block comprising α-methylstyrene units-b-polydiene-b-thermoplastic block comprising α-methylstyrene units) containing less than 10% by weight of a thermoplastic polymer containing poly(α-methylstyrene) units, the distribution of the different fractions of the product is obtained by integration of the RI signals of the SEC chromatogram. The weight proportion of each fraction is related to the integration of all the RI signals of the chromatogram.

[0145] In the case of a product comprising more than 10% by weight of a thermoplastic polymer comprising poly(α-methylstyrene) units, the distribution of the different fractions of the product is obtained by integration of the RI signal of the SEC chromatogram, while adjusting the RI response by the value of a specific increment of the refractive index dn / dc for each fraction, or by metering the thermoplastic polymer comprising poly(α-methylstyrene) units to produce a calibration straight line in a manner known to a person skilled in the art.

[0146] C- Composition of the elastomer matrix

[0147] C-1 Determination of the content of thermoplastic polymers and block polymers containing α-methylstyrene units by RI SEC as described above

[0148] In the case where a thermoplastic polymer comprising α-methylstyrene units is added to the thermoplastic elastomer, the amount of thermoplastic polymer comprising α-methylstyrene units present in the elastomer matrix can be calculated according to a calculation known to a person skilled in the art by adding the amount contained in the mixture obtained from the synthesis of the thermoplastic elastomer (determined by RI SEC) and the amount of thermoplastic polymer added.

[0149] C-2 Determination of the content of thermoplastic chains comprising α-methylstyrene units by NMR as described above

[0150] C-3 Content of thermoplastic block containing α-methylstyrene units

[0151] The content of the thermoplastic block comprising α-methylstyrene units is calculated as follows:

[0152] Content of thermoplastic block containing α-methylstyrene units = (content of thermoplastic chain containing α-methylstyrene units - content of thermoplastic polymer containing α-methylstyrene units) * 100 / (100 - content of thermoplastic polymer containing α-methylstyrene units)

[0153] D—Measurement of Tg of Thermoplastic Blocks Comprising α-Methylstyrene Units and Thermoplastic Polymers Comprising α-Methylstyrene Units

[0154] D-1 Thermoplastic Elastomer Block

[0155] The characterization of the Tg values ​​of the thermoplastic elastomers (elastomer blocks and thermoplastic blocks comprising α-methylstyrene units) was carried out by DSC measurement (Netzsch DSC214 Polyma equipment). The equipment was operated under a helium atmosphere. A sample of 10 to 20 mg of the thermoplastic elastomer was taken out and placed in a crucible commonly used by those skilled in the art for Tg measurements.

[0156] The sample is first placed under isothermal conditions at +25°C for 2 minutes, and then cooled to -100°C at a rate of 50°C / min. Isothermal is then applied at -100°C for 5 minutes. Then, the first heating starts from -100°C to +10°C at a rate of 20°C / min, and continues from 10°C to 250°C at a rate of 50°C / min. Then, the sample is quenched at the maximum speed allowed by the equipment to reach -100°C. Then, the sample is kept under isothermal conditions at -100°C for 5 minutes. Then, the second heating starts from -100°C to +10°C (the measurement range of the Tg of the elastomer block) at a rate of 20°C / min, and continues from +10°C to +250°C (the measurement range of the Tg of the thermoplastic block containing α-methylstyrene units) at a rate of 50°C / min. In this measurement, only the second heating is used.

[0157] D-2 Thermoplastic polymer containing α-methylstyrene units

[0158] The characterization of the Tg value of the thermoplastic polymer containing α-methylstyrene units is carried out by DSC measurement (Netzsch DSC214 Polyma equipment). The equipment is operated under a helium atmosphere. A sample of 10 mg to 20 mg of the TPE elastomer is taken out and placed in a crucible commonly used by a person skilled in the art for Tg measurement.

[0159] First, the sample is placed under isothermal conditions at +10°C for 2 minutes. Then, the first heating is started at a rate of 50°C / min from 10°C to +250°C. Then, the sample is cooled from 250°C to 10°C at a rate of 30°C / min. Then, the sample is kept under isothermal conditions at 10°C for 2 minutes. Then, the second heating is started at a rate of 50°C / min from 10°C to +250°C. In this measurement, only the second heating is used.

[0160] E-hysteresis properties

[0161] Tan δmax is measured on a viscoanalyzer (Metravib VA4000) according to standard ASTM D 5992-96. According to standard ASTM D 1349-99, the viscosity of a pre-molded elastomer matrix sample (with a thickness of 2 mm and a cross section of 79 mm) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz at 60°C is recorded. 2The response of a cylindrical specimen of 100 mm / s is measured. The strain amplitude is swept from 0.1% to 50% peak-to-peak (outward cycle) and then from 50% to 0.1% peak-to-peak (return cycle). The result used more particularly is the loss factor tan δ. For the return cycle, the maximum value of tan δ observed is indicated, denoted tan δmax. This value represents the hysteresis of the material: the smaller the value of tan δmax, the smaller the hysteresis of the matrix.

[0162] II. Polymer Synthesis and Elastomer Matrix Preparation

[0163] In the following tests, the following names will be used:

[0164] Poly(α-methylstyrene) = PAMS

[0165] Bonded poly(α-methylstyrene) = Bonded PAMS = Thermoplastic block of the block polymer containing α-methylstyrene units

[0166] Total poly(α-methylstyrene) = Total PAMS = Thermoplastic chains containing α-methylstyrene units

[0167] Free poly(α-methylstyrene) = Free PAMS = Thermoplastic polymer containing α-methylstyrene units

[0168] A-Synthesis of poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer A containing 15 wt% of total poly(α-methylstyrene):

[0169] 3.46 kg of methylcyclohexane, 2 kg of α-methylstyrene and 0.25 mol of tetrahydrofurfuryl ether are introduced into an 80 liter reactor. After neutralization of the impurities using n-butyllithium, 0.05 mol of sec-butyllithium are introduced. After 2 hours and 55 minutes at T=5°C, the conversion of α-methylstyrene, measured by solids content, is 50%. Analysis of the polymer by size exclusion chromatography shows the presence of a single population: M n =18100 g / mol. Tg measured by DSC is 139°C.

[0170] At the end of 2 hours and 55 minutes at 5° C., 33.1 kg of methylcyclohexane (previously neutralized with n-butyllithium for its impurities) were introduced into the reactor, followed by the introduction of 5.7 kg of butadiene by means of a pump at a flow rate of 13 kg / h. The reaction medium was maintained at 5° C. At the end of the 26 minutes required to introduce 5.7 kg of butadiene, the medium was maintained at 5° C. for a further 80 minutes. At the end of 106 minutes at 5° C., the butadiene conversion was 96%. Analysis of the polymer by size exclusion chromatography showed the presence of two populations: M n,1=13800 g / mol (2%) (corresponding to free PAMS) and M n,2 =114100 g / mol (98%) (corresponding to PAMS-b-polybutadiene diblock).

[0171] 0.024 mol of dimethyldichlorosilane are then introduced into the reactor. The reaction medium is kept at 5° C. for 12 minutes. The polymer obtained at the end of this coupling stage is a poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer, which shows three populations by SEC analysis:

[0172] -M n,1 =12000 g / mol (2%), corresponding to free PAMS,

[0173] -M n,2 = 101000 (14%), corresponding to PAMS-b-polybutadiene diblock, and

[0174] -M n,3 = 229,000 (83%), corresponding to PAMS-b-polybutadiene-b-PAMS triblock.

[0175] The weight content of total poly(alpha-methylstyrene) chains in the final sample was 15% as measured by NMR.

[0176] The weight content of the combined poly(α-methylstyrene) blocks was 13% relative to the total weight of the diblock and triblock in the final sample.

[0177] The dry polymer was recovered by steam stripping followed by drying in an oven.

[0178] B-Synthesis of poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer B with a total poly(α-methylstyrene) content of 28 wt%:

[0179] 5 kg of methylcyclohexane, 3 kg of α-methylstyrene and 0.375 mol of tetrahydrofurfuryl ether are introduced into an 80 liter reactor. After neutralization of the impurities using n-butyllithium, 0.075 mol of sec-butyllithium are introduced. After 2 hours and 20 minutes at T=5°C, the conversion of α-methylstyrene, measured by solids content, is 51%. Analysis of the polymer by size exclusion chromatography shows the presence of a single population: M n =18500 g / mol. Tg measured by DSC is 155°C.

[0180] At the end of 2 hours and 20 minutes at 5° C., 33.6 kg of methylcyclohexane (previously neutralized with n-butyllithium for its impurities) are introduced into the reactor, followed by the introduction of 6 kg of butadiene by means of a pump at a flow rate of 13 kg / h. The reaction medium is maintained at 5° C. At the end of the 28 minutes required to introduce 6 kg of butadiene, the medium is maintained at 5° C. for a further 5 minutes. At the end of 33 minutes at 5° C., the butadiene conversion is 79%. Analysis of the polymer by size exclusion chromatography shows the presence of two populations: M n,1 =10800 g / mol (2%) (corresponding to free PAMS) and M n,2 =53800 g / mol (98%) (corresponding to PAMS-b-polybutadiene diblock).

[0181] 0.036 mol of dimethyldichlorosilane are then introduced into the reactor. The reaction medium is kept at 5° C. for 12 minutes. The polymer obtained at the end of this coupling stage is a poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer, which shows three populations by SEC analysis:

[0182] -M n,1 =11000 g / mol (2%), corresponding to free PAMS,

[0183] -M n,2 = 55000 (5%), corresponding to PAMS-b-polybutadiene diblock, and

[0184] -M n,3 =113000 (93%), corresponding to PAMS-b-polybutadiene-b-PAMS triblock.

[0185] The weight content of total poly(alpha-methylstyrene) chains in the final sample was 28% as measured by NMR.

[0186] The weight content of the combined poly(α-methylstyrene) blocks was 27% relative to the total weight of the diblock and triblock in the final sample.

[0187] The dry polymer was recovered by steam stripping followed by drying in an oven.

[0188] C—Synthesis of poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer C containing 38 wt% of total poly(α-methylstyrene):

[0189] 8.47 kg of methylcyclohexane, 5 kg of α-methylstyrene and 0.625 mol of tetrahydrofurfuryl ether are introduced into an 80 liter reactor. After neutralization of the impurities using n-butyllithium, 0.125 mol of sec-butyllithium are introduced. After 2 hours and 24 minutes at T=5°C, the conversion of α-methylstyrene, measured by solids content, is 49%. Analysis of the polymer by size exclusion chromatography shows the presence of a single population: M n =18000 g / mol. Tg measured by DSC is 143°C.

[0190] At the end of 2 hours and 24 minutes at 5° C., 20 kg of methylcyclohexane (previously neutralized with n-butyllithium for its impurities) are introduced into the reactor, followed by the introduction of 4.3 kg of butadiene by means of a pump at a flow rate of 13 kg / h. The reaction medium is maintained at 5° C. At the end of the 21 minutes required to introduce the 4.3 kg of butadiene, the medium is maintained at 5° C. for a further 5 minutes. At the end of 26 minutes at 5° C., the butadiene conversion is 85%. Analysis of the polymer by size exclusion chromatography shows the presence of two populations: M n,1 =10400 g / mol (2%) (corresponding to free PAMS) and M n,2 =37700 g / mol (98%) (corresponding to PAMS-b-polybutadiene diblock).

[0191] 0.06 mol of dimethyldichlorosilane are then introduced into the reactor. The reaction medium is kept at 5° C. for 12 minutes. The polymer obtained at the end of this coupling stage is a poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock polymer, which shows three populations by SEC analysis:

[0192] -M n,1 =10000 g / mol (2%), corresponding to free PAMS,

[0193] -M n,2 = 38000 (4%), corresponding to PAMS-b-polybutadiene diblock, and

[0194] -M n,3 =77000 (94%), corresponding to PAMS-b-polybutadiene-b-PAMS triblock.

[0195] The weight content of total poly(alpha-methylstyrene) chains in the final sample was 38% as measured by NMR.

[0196] The weight content of the combined poly(α-methylstyrene) blocks was 37% relative to the total weight of the diblock and triblock in the final sample.

[0197] The dry polymer was recovered by steam stripping followed by drying in an oven.

[0198] Synthesis of D-poly(α-methylstyrene) polymer D:

[0199] 13.3 kg of methylcyclohexane, 30 kg of α-methylstyrene and 1.73 mol of tetrahydrofuran are introduced into an 80 liter reactor. After neutralization of the impurities using n-butyllithium, 0.75 mol of sec-butyllithium are introduced. After 66 minutes at T=20°C, the conversion of α-methylstyrene, measured by solid content, is 53%. The conversion is determined by weighing the extract dried at 140°C under a reduced pressure of 200 mmHg. The polymerization is terminated by adding methanol (2 eq. / Li) to the reaction medium and the dry polymer is recovered by stripping and then drying in an oven. Analysis of the polymer by size exclusion chromatography shows the presence of a single population: M n =19100 g / mol. Tg measured by DSC is 160°C.

[0200] Preparation of Elastomer Matrix of E-poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock and poly(α-methylstyrene) polymer:

[0201] In order to produce a mixture of poly(α-methylstyrene)-b-polybutadiene-b-poly(α-methylstyrene) triblock + poly(α-methylstyrene) + poly(α-methylstyrene)-b-polybutadiene diblock polymers with a controlled ratio, the weight content (g / l) of the polymers of the polymer-containing solutions A to D was measured by solid content. The volumes of solutions A to D to be mixed recovered at the end of the polymerization were adjusted to obtain the target ratio of the polymers (see Table 1 below for the target ratios). The solutions in methylcyclohexane were mixed at ambient temperature for one hour and the dried polymer mixture was then recovered by stripping and then drying in an oven by devolatilization.

[0202] Table 1

[0203] Matrix 1 2 3 4 5 6 Polymer A 100％ 87％ 74％ Polymer B 100％ 86％ Polymer C 100％ Polymer D 13％ 14％ 26％

[0204] The elastomeric matrix thus obtained by blending is shaped by molding for measuring its physical, mechanical or dynamic properties.

[0205] The results are given in the following Table 2. The contents are expressed as weight percentages relative to the total weight of the elastomeric matrix.

[0206] Table 2

[0207]

[0208] *The contents are expressed as % by weight relative to the total weight of the elastomeric matrix.

[0209] From the results given in the table, we can see that:

[0210] - the presence of 15% by weight of a poly(α-methylstyrene) polymer according to the invention in the elastomeric matrix 4 makes it possible to reduce the hysteresis of the material at the same total content of poly(α-methylstyrene) relative to a control matrix 2 comprising 2% by weight of a poly(α-methylstyrene) polymer;

[0211] - The presence of 16% and 27% by weight of poly(α-methylstyrene) polymer according to the invention in the elastomeric matrices 5 and 6, respectively, makes it possible to reduce the hysteresis of the material at the same total content of poly(α-methylstyrene), relative to the control matrix 3 comprising 2% by weight of poly(α-methylstyrene) polymer.

[0212] Thus, it was found that by increasing the content of thermoplastic polymer comprising α-methylstyrene units in an elastomeric matrix, without increasing the total content of thermoplastic chains comprising α-methylstyrene units, it is possible to reduce the tan δ value at 60° C. and therefore the hysteresis of an elastomeric matrix comprising a mixture of a triblock thermoplastic elastomer comprising a central diene elastomer block and terminal thermoplastic blocks comprising α-methylstyrene units and from 2% to 20% of a diblock thermoplastic elastomer containing a thermoplastic block comprising α-methylstyrene units.

Claims

1. An elastomeric matrix, comprising: a triblock thermoplastic elastomer having a central diene elastomeric block and two terminal thermoplastic blocks comprising α-methylstyrene units bonded to said diene elastomeric block, - 2% to 20% by weight, relative to the total weight of the elastomeric matrix, of a diblock thermoplastic elastomer having a diene elastomeric block and a thermoplastic block comprising α-methylstyrene units, - greater than 10% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising alpha-methylstyrene units, The content of the thermoplastic block of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer. The content of thermoplastic chains comprising α-methylstyrene units is up to 55% by weight, relative to the total weight of the elastomeric matrix. The thermoplastic chain comprising α-methylstyrene units is constituted by a chain of a thermoplastic polymer comprising α-methylstyrene units and a chain of a thermoplastic block of a triblock thermoplastic elastomer and a diblock thermoplastic elastomer.

2. Elastomer matrix according to the preceding claim, characterized in that The elastomeric matrix comprises at most 45% by weight of a thermoplastic polymer comprising α-methylstyrene units, relative to the total weight of the elastomeric matrix.

3. Elastomer matrix according to any one of the preceding claims, characterized in that The elastomeric matrix comprises at least 20% by weight, preferably at least 25% by weight, of thermoplastic chains comprising α-methylstyrene units, relative to the total weight of the elastomeric matrix.

4. Elastomer matrix according to any one of the preceding claims, characterized in that The elastomeric matrix comprises at least 15% by weight of a thermoplastic polymer comprising alpha-methylstyrene units, relative to the total weight of the elastomeric matrix.

5. Elastomer matrix according to any one of the preceding claims, characterized in that The elastomeric matrix primarily comprises a triblock thermoplastic elastomer.

6. Elastomer matrix according to any one of the preceding claims, characterized in that The elastomeric matrix comprises up to 80% by weight of a triblock thermoplastic polymer.

7. Elastomer matrix according to any one of the preceding claims, characterized in that The content of the thermoplastic block comprising α-methylstyrene units is at least 15% by weight relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

8. Elastomer matrix according to any one of the preceding claims, characterized in that The content of the thermoplastic block comprising α-methylstyrene units is at most 45% by weight, preferably at most 40% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer.

9. Elastomer matrix according to any one of the preceding claims, characterized in that The diene elastomer blocks of the triblock thermoplastic elastomers and of the diblock thermoplastic elastomers comprise units derived from butadiene.

10. Elastomer matrix according to any one of the preceding claims, characterized in that The triblock thermoplastic elastomer and the diene elastomeric blocks of the diblock thermoplastic elastomer additionally comprise units derived from a vinyl aromatic monomer, preferably styrene.

11. Elastomer matrix according to any one of the preceding claims, characterized in that The thermoplastic block containing α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer mainly contains units derived from α-methylstyrene.

12. Elastomer matrix according to any one of the preceding claims, characterized in that The thermoplastic blocks containing α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer are substantially composed of units derived from α-methylstyrene.

13. Elastomer matrix according to any one of the preceding claims, characterized in that The thermoplastic polymer comprising units derived from α-methylstyrene comprises predominantly units derived from α-methylstyrene.

14. Elastomer matrix according to any one of the preceding claims, characterized in that The thermoplastic polymer comprising units derived from alpha-methylstyrene is an alpha-methylstyrene homopolymer.

15. Elastomer matrix according to any one of the preceding claims, characterized in that: - the diene blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer comprise units derived from butadiene, - the thermoplastic blocks of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer consist of poly(α-methylstyrene), - the thermoplastic polymer comprising α-methylstyrene units is poly(α-methylstyrene), - the content of the thermoplastic block comprising α-methylstyrene units of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer is at least 10% and at most 45% by weight, relative to the total weight of the triblock thermoplastic elastomer and the diblock thermoplastic elastomer, - the said matrix comprises more than 10% by weight, preferably at least 15% by weight and at most 45% by weight, relative to the total weight of the elastomeric matrix, of a thermoplastic polymer comprising α-methylstyrene units, The content of thermoplastic chains comprising α-methylstyrene units is at least 20% and at most 55% by weight, relative to the total weight of the elastomeric matrix.

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