POLYMER COMPOSITION WITH A THERMOPLASTIC ELASTOMER WITH BUTADIENE AND STYRENE BLOCKS AND A COMPATIBLE PLASTICIZER

Description

[0001] The present invention relates to a polymeric composition comprising a thermoplastic elastomer whose elastomer block(s) are predominantly butadiene and further comprising units derived from one or more styrenic monomers, and whose thermoplastic block(s) are styrenic, and a plasticizer selective for the diene elastomer phase.

[0002] In a conventional tire, the tread generally comprises mainly by weight one or more diene elastomers.

[0003] A constant objective of tire manufacturers is to improve tire grip on wet surfaces. At the same time, another objective is to reduce tire rolling resistance. However, these two objectives are difficult to reconcile in that improving grip requires increasing hysteretic losses, while improving rolling resistance requires reducing hysteretic losses. There is therefore a performance compromise to be optimized.

[0004] For this purpose, the applicants have previously developed tire compositions comprising a thermoplastic elastomer. These tires offer a very good compromise between grip and rolling resistance performance.

[0005] Furthermore, thermoplastic elastomer treads are easy to use due to their low viscosity at temperature.

[0006] To further improve these tires, the room temperature rigidity of the treads must be finely adjusted.

[0007] It is known to use plasticizers in combination with thermoplastic elastomers to adjust the stiffness of the composition. However, these plasticizers are not selective for the elastomer phase.

[0008] Reference may also be made to document DE 10 2016 210267 which discloses a sulfur-crosslinkable rubber mixture comprising at least one diene rubber, at least one silica, at least one plasticizer and at least one thermoplastic elastomer which may be a styrene-based triblock copolymer, but the properties obtained are not satisfactory.

[0009] It is advantageous to have plasticizers that are selective for the diene elastomer phase. Indeed, these make it possible to shift the glass transition temperature of the elastomer phase (which determines the temperature positioning of the adhesion potential of the material) and to adjust the rigidity of the composition, without modifying the glass transition temperature of the thermoplastic phase of the thermoplastic elastomer (which controls the thermal resistance of the material, particularly for high-speed performance).

[0010] The applicants have discovered that the use of a specific plasticizer chosen from butadiene oligomers as defined below in a polymer composition comprising a thermoplastic elastomer with blocks comprising at least one elastomer block and at least one thermoplastic block, the elastomer block(s) comprising mainly units derived from butadiene and further comprising units derived from one or more styrene monomers, the thermoplastic block(s) being made up of units derived from one or more styrene monomers, makes it possible to obtain a selective effect of the plasticizer in the elastomer phase.

[0011] The subject of the invention is therefore a polymeric composition comprising a) at least one thermoplastic block elastomer comprising at least one elastomer block and at least one thermoplastic block, the elastomer block(s) comprising mainly units derived from butadiene and further comprising units derived from one or more styrene monomers, the thermoplastic block(s) being made up of units derived from one or more styrene monomers, b) at least one plasticizer chosen from butadiene oligomers, it being understood that: b1) the molar content of 1,2-polybutadiene unit in said plasticizer is within a range from 70% to 130% of the molar content of 1,2-polybutadiene unit in the elastomer block of the thermoplastic elastomer, and the molar mass Mn of the plasticizer is greater than 2000 g / mol and less than 50000 g / mol, or b2) the molar content of 1,2-polybutadiene unit polybutadiene 1,2 in the plasticizer is less than 70%, or greater than 130% of the molar rate of polybutadiene 1 unit,2 in the elastomer block of the thermoplastic elastomer, and, the molar mass Mn of the plasticizer is greater than 5000 g / mol, and less than 50000 g.

[0012] In this description, unless expressly indicated otherwise, all percentages (%) indicated are mass percentages.

[0013] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (i.e., excluding the limits a and b) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e., including the strict limits a and b).

[0014] In the present application, the term "part per cent of elastomer" or "pce" means the part by weight of a constituent per 100 parts by weight of the elastomer(s), i.e. of the total weight 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.

[0015] Thermoplastic elastomer (TPE) is understood to mean, in a known manner, a polymer comprising a thermoplastic part and an elastomeric part.

[0016] A thermoplastic elastomer is a copolymer consisting of one or more rigid “thermoplastic” blocks linked to one or more flexible “elastomer” blocks.

[0017] Thus, the thermoplastic elastomer(s) of the polymeric composition of the tire according to the invention comprise at least one elastomer block and at least one thermoplastic block.

[0018] Typically, each of these blocks contains at least more than 5, usually more than 10, repeat units.

[0019] In the present application, when reference is made to the glass transition temperature of a thermoplastic elastomer, this is the glass transition temperature relative to the elastomer block (unless otherwise indicated). Indeed, as is known, non-crystalline thermoplastic elastomers have two peaks of glass transition temperature (Tg, measured according to ASTM D3418), the lower temperature being relative to the elastomer part of the thermoplastic elastomer, and the higher temperature being relative to the thermoplastic part of the thermoplastic elastomer. Thus, the flexible blocks of thermoplastic elastomers, called elastomeric, are generally defined by a Tg less than or equal to room temperature (25°C), while the rigid blocks called thermoplastic have a Tg greater than or equal to 80°C.To be both elastomeric and thermoplastic in nature, the thermoplastic elastomer must have blocks that are sufficiently incompatible (i.e. different due to their respective mass, polarity or Tg) to retain their own properties as elastomeric or thermoplastic blocks.

[0020] Thus, the thermoplastic elastomer(s) that can be used according to the invention (therefore the elastomer block(s) of the thermoplastic elastomers) preferably have a glass transition temperature of the elastomer block(s) that is less than or equal to 25°C, more preferably less than or equal to 10°C. A Tg value higher than these minima can reduce the performance of the tread when used at very low temperatures; for such use, the glass transition temperature of the thermoplastic elastomers is more preferably still less than or equal to -10°C.

[0021] Also preferably, the glass transition temperature of the thermoplastic elastomers which can be used according to the invention is greater than -110°C.

[0022] The number-average molecular mass (Mn) of thermoplastic elastomers is preferably between 30,000 and 500,000 g / mol, more preferably between 40,000 and 400,000 g / mol. Below the indicated minima, the cohesion between the elastomer chains of the thermoplastic elastomers, in particular due to their possible dilution (in the presence of an extender oil), risks being affected. Furthermore, an excessively high Mn mass can be detrimental to implementation. Thus, it has been found that a value between 50,000 and 300,000 g / mol is particularly well suited to the use of thermoplastic elastomers in a tire tread.

[0023] The polydispersity index (Ip = Mw / Mn with Mw weight average molecular mass) of the thermoplastic elastomer(s) is preferably less than 3; more preferably less than 2, and even more preferably less than 1.5.

[0024] The thermoplastic elastomers that can be used according to the invention may be copolymers with a small number of blocks (less than 5, typically 2 or 3), in which case these blocks preferably have high masses, greater than 15,000 g / mol.

[0025] Thermoplastic elastomers can also be copolymers with a large number of smaller blocks (more than 30, typically 50 to 500), in which case these blocks preferably have low masses, for example 500 to 5000 g / mol, these thermoplastic elastomers will be called multi-block thermoplastic elastomers hereinafter.

[0026] According to a first variant, the thermoplastic elastomers which can be used according to the invention are in a linear form.

[0027] In a first particular embodiment of this first variant, the thermoplastic elastomers are diblock copolymers: thermoplastic block / elastomer block.

[0028] In a second particular embodiment of this first variant, the thermoplastic elastomers are triblock copolymers: thermoplastic block / elastomer block / thermoplastic block, i.e. a central elastomer block and a terminal thermoplastic block at each of the two ends of the elastomer block.

[0029] In a third particular embodiment of this first variant, the thermoplastic elastomers are made up of an alternating linear sequence of elastomer blocks and thermoplastic blocks (multi-block thermoplastic elastomers).

[0030] According to a second variant, the thermoplastic elastomers usable according to the invention are in a star shape with at least three branches.

[0031] For example, the thermoplastic elastomers may then consist of a star-shaped elastomer block with at least three branches and a thermoplastic block, located at the end of each of the branches of the elastomer block. The number of branches of the central elastomer may vary, for example from 3 to 12, and preferably from 3 to 6.

[0032] According to a third variant, the thermoplastic elastomers usable according to the invention are in a branched or dendrimer form. The thermoplastic elastomers can then be composed of a branched or dendrimer elastomer block and a thermoplastic block, located at the end of the branches of the dendrimer elastomer block.

[0033] As explained previously, the polymeric composition according to the invention comprises at least one thermoplastic elastomer with blocks comprising at least one elastomer block and at least one thermoplastic block.

[0034] The elastomer block(s) mainly comprise units derived from butadiene.

[0035] In other words, each elastomer block comprises at least 50% by weight, preferably at least 70% by weight of units derived from butadiene, relative to the weight of said elastomer block.

[0036] According to the invention, the elastomer block(s) further comprise units derived from one or more styrenic monomers.

[0037] The butadiene used to form the elastomer block(s) may be copolymerized, in a statistical manner, with at least one other monomer so as to form an elastomer block comprising mainly units derived from butadiene. The molar fraction of polymerized monomer other than butadiene, relative to the total number of units in the elastomer block, must be such that this block retains its elastomer properties. Advantageously, the molar fraction of this other comonomer may range from 0 to 50%, more preferably from 0 to 45% and even more preferably from 0 to 30%.

[0038] As styrenic monomers which may be used for the elastomer block(s), mention may be made of styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene, beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethylstyrene, beta-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chlorostyrene, alpha-chloro-m-chlorostyrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorostyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene,beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, styrene derivatives substituted by a silyl group. The preferred styrenic monomers are styrene and alphamethylstyrene.,

[0039] Preferably, the units derived from styrenic monomers in said elastomer block(s) represent 0 to 50% by weight of the elastomer block.

[0040] Thus, the at least one elastomer block may be a random copolymer of the styrene-butadiene type (SBR), this copolymer being able to be hydrogenated. This SBR block preferably has a Tg (glass transition temperature) measured by DSC according to the ASTM D3418 standard of 1999, less than 25°C, preferably less than 10°C, more preferably less than 0°C and very preferably less than -10°C. Also preferably, the Tg of the SBR block is greater than -100°C. Particularly suitable are SBR blocks having a Tg of between 20°C and -70°C and more particularly between 0°C and -50°C. As is well known, the SBR block comprises a styrene content, a -1,2 unit content of the butadiene part, and a -1,4 unit content of the butadiene part, the latter consisting of a trans-1,4 unit content and a cis-1,4 unit content when the butadiene part is not hydrogenated.Preferably, an SBR block is used in particular having a styrene content of, for example, in a range from 0 to 50% by weight, preferably from 0% to 30% by weight, and for the butadiene part, a content of -1,2 bonds of a range from 0% to 90% (mol%), and a content of -1,4 bonds of a range from 0% to 90% (mol%).

[0041] Preferably for the invention, the elastomer blocks of the thermoplastic elastomers have, in total, a number-average molecular mass ("Mn") ranging from 25,000 g / mol to 350,000 g / mol, preferably from 35,000 g / mol to 250,000 g / mol so as to give the thermoplastic elastomers good elastomeric properties and sufficient mechanical strength compatible with use in tires.

[0042] As explained previously, the thermoplastic elastomers usable according to the invention also comprise at least one thermoplastic block.

[0043] By thermoplastic block is meant a block consisting of polymerized monomers and having a glass transition temperature, or a melting temperature in the case of semi-crystalline polymers, greater than or equal to 80°C, preferably varying from 80°C to 250°C, more preferably varying from 80°C to 200°C, and in particular varying from 80°C to 180°C.

[0044] When the thermoplastic block is a semi-crystalline polymer, a melting temperature higher than the glass transition temperature can be observed. In this case, the melting temperature is taken into account for the above definition and not the glass transition temperature.

[0045] The thermoplastic block(s) of the thermoplastic elastomer used according to the invention consist of units derived from one or more styrenic monomers.

[0046] Preferably, the styrenic monomer(s) of the thermoplastic block(s) are chosen from styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene, beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethylstyrene, beta-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chlorostyrene, alpha-chloro-m-chlorostyrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorostyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene,beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, styrene derivatives substituted by a silyl group.,

[0047] According to a preferred embodiment, the thermoplastic block(s) mainly comprise units derived from the alpha-methylstyrene monomer.

[0048] In other words, according to this embodiment, each thermoplastic block comprises at least 50% by weight, preferably at least 70% by weight, of units derived from the alpha-methylstyrene monomer.

[0049] More preferably, the thermoplastic block(s) consist of units derived from the alpha-methylstyrene monomer.

[0050] Preferably, the thermoplastic blocks of the thermoplastic elastomers have a total number-average molecular weight (“Mn”) ranging from 5,000 g / mol to 150,000 g / mol.

[0051] The thermoplastic block(s) are preferably present in sufficient proportions to preserve the thermoplastic character of the thermoplastic elastomers usable according to the invention. The minimum level of thermoplastic blocks in the thermoplastic elastomers may vary depending on the conditions of use of the thermoplastic elastomers.

[0052] On the other hand, the ability of thermoplastic elastomers to deform during tire preparation can also contribute to determining the proportion of thermoplastic blocks in the thermoplastic elastomers usable according to the invention.

[0053] Preferably, the thermoplastic block(s) consisting of units derived from one or more styrene monomers represent at most 35%, preferably from 10 to 35% by weight, relative to the weight of the thermoplastic elastomer.

[0054] The thermoplastic elastomer usable in the polymeric composition of the tire according to the invention generally represents from 15 to 100 pce of the polymeric composition, preferably from 50 to 100 pce, more preferably from 70 to 100 pce.

[0055] The thermoplastic elastomer usable in the polymer composition according to the invention can be prepared by the synthesis process analogous to that described in document FR 3 045 615.

[0056] The polymeric composition according to the invention may also comprise one or more non-thermoplastic elastomers, such as diene elastomers well known to those skilled in the art.

[0057] By “diene” elastomer or rubber, one must understand in a known manner one (meaning one or more) elastomers derived at least in part (i.e.; a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0058] According to the invention, the term “diene elastomer” should be understood to mean any synthetic elastomer derived at least in part from diene monomers. More particularly, the term “diene elastomer” means any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinylaromatic compounds having 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinylaromatic units.Suitable conjugated dienes which can be used in the process according to the invention are, in particular, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C1-C5 alkyl)-1,3-butadiene such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, etc.

[0059] The diene elastomer possibly present in the composition is preferably chosen from the group of diene elastomers consisting of polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers, ethylene and diene copolymers and mixtures of these polymers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-butadiene-styrene copolymers (SBIR), halogenated or non-halogenated butyl rubbers, and ethylene and butadiene copolymers (EBR).

[0060] In a particularly preferred manner, the thermoplastic elastomer(s) which can be used according to the invention and described above are the only elastomers in the polymer composition of the tire according to the invention.

[0061] As explained previously, the polymeric composition according to the invention comprises at least one plasticizer chosen from butadiene oligomers, it being understood that: b1) the molar content of 1,2-polybutadiene unit in said plasticizer is within a range from 70% to 130% of the molar content of 1,2-polybutadiene unit in the elastomer block of the thermoplastic elastomer, and the molar mass Mn of the plasticizer is greater than 2000 g / mol, and less than 50000 g / mol, or b2) the molar content of 1,2-polybutadiene unit in the plasticizer is less than 70%, or greater than 130% of the molar content of 1,2-polybutadiene unit in the elastomer block of the thermoplastic elastomer, and the molar mass Mn of the plasticizer is greater than 5000 g / mol, and less than 50000 g / mol.

[0062] Preferably, the plasticizer(s) represent from 5 to 50 pce, preferably from 5 to 30 pce, better still from 7 to 20 pce.

[0063] The polymeric composition according to the invention may also comprise a crosslinking system.

[0064] Preferably, the crosslinking system is based on sulfur or a sulfur donor.

[0065] The expression "crosslinking system based on" means that the crosslinking system comprises a mixture and / or the reaction product of the different constituents used in the crosslinking system, and in particular the sulfur or the sulfur donor, some of these basic constituents being capable of, or intended to, react with each other or with the other constituents of the tire, at least in part, during the different phases of manufacturing the tire.

[0066] The crosslinking system may be a vulcanization system. In this case, it is preferably sulfur-based or based on a sulfur donor and a vulcanization accelerator, in particular a primary vulcanization accelerator.

[0067] Among the sulfur donors, we can cite for example alkyl phenol disulfides (APDS) such as for example paratertiobutylphenol disulfide.

[0068] Advantageously, the sulfur or sulfur donor content is between 0.2 and 2 pce, preferably between 0.5 and 1.5 pce, more preferably between 0.5 and 1.4 pce.

[0069] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur may be used as the primary accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the thiuram type, zinc dithiocarbamates. These accelerators are more preferably chosen from the group consisting of N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated as "CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated as "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated as "TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide (abbreviated as "TBSI"), zinc dibenzyldithiocarbamate (abbreviated as "ZBEC") and mixtures of these compounds.

[0070] Preferably, a primary accelerator of the sulfenamide type is used.

[0071] Particularly preferably, the primary vulcanization accelerator is N-cyclohexyl-2-benzothiazyl sulfenamide (CBS).

[0072] According to a particular embodiment of the invention, the level of vulcanization accelerator(s) varies from 0.2 to 10 pce, preferably varies from 0.2 to 7 pce, more preferably from 0.6 to 2 pce.

[0073] Advantageously, the weight ratio of sulfur or sulfur donor / vulcanization accelerator varies from 0.25 to 4.

[0074] Optionally, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine), etc. are added to this vulcanization system.

[0075] The polymeric composition according to the invention may also comprise a reinforcing filler.

[0076] In particular, any type of filler normally used for the manufacture of tires can be used, for example an organic filler such as carbon black, an inorganic filler such as silica, or a blend of these two types of filler, in particular a blend of carbon black and silica.

[0077] Suitable carbon blacks are all carbon blacks conventionally used in tires (so-called tire-grade blacks). Examples include reinforcing carbon blacks of the 100, 200 or 300 series (ASTI grades), such as blacks N115, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N660, N683, N772), or even N990.

[0078] By "reinforcing inorganic filler" is meant in the present application, by definition, any inorganic or mineral filler (whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even "non-black filler" as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words capable of replacing, in its reinforcing function, a conventional tire-grade carbon black; such a filler is generally characterized, in a known manner, by the presence of hydroxyl groups (-OH) on its surface.

[0079] The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below.

[0080] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, in particular silica (SiO 2 ), or of the aluminous type, in particular alumina (Al 2 O 3 ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area both of less than 450 m 2 < / g, preferably from 30 to 400 m 2 < / g. Examples of highly dispersible precipitated silicas (known as “HDS”) include “Ultrasil” 7000 and “Ultrasil” 7005 silicas from Degussa, “Zeosil” 1165MP, 1135MP and 1115MP silicas from Rhodia, “Hi-Sil” EZ150G silica from PPG, “Zeopol” 8715, 8745 and 8755 silicas from Huber, and high specific surface silicas as described in application WO 03 / 16837.

[0081] To couple the reinforcing inorganic filler to the elastomer, it is possible, for example, to use in a known manner an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the elastomer, in particular bifunctional organosilanes or polyorganosiloxanes.

[0082] The volumetric content of optional reinforcing filler in the polymer composition (carbon black and / or reinforcing inorganic filler such as silica) is within a range from 0 to 30%, which corresponds approximately to a content of 0 to 100 phr for a polymer composition without plasticizer. Preferably, the polymer composition according to the invention comprises less than 30 phr of reinforcing filler and more preferably less than 10 phr.

[0083] According to a preferred variant of the invention, the polymeric composition does not contain a reinforcing filler.

[0084] In the same way, the polymeric composition according to the invention may contain one or more inert micrometric fillers such as the lamellar fillers known to those skilled in the art.

[0085] Preferably, the polymeric composition according to the invention does not contain a micrometric filler.

[0086] In addition to the elastomers previously described, the composition of the polymeric composition could also comprise, always in a minority weight fraction relative to the thermoplastic elastomers, polymers other than elastomers, such as for example thermoplastic polymers. When they are present in the polymeric composition, it is preferred that the total level of non-elastomeric thermoplastic polymers be less than 40 phr, preferably between 5 and 30 phr, and more preferably between 10 and 25 phr.

[0087] The invention also relates to a tire comprising a polymeric composition as defined above. Examples

[0088] Determination of molar mass distribution by SEC RI equivalent PS

[0089] It is determined by size exclusion chromatography (SEC) in polystyrene equivalent. SEC separates macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first. Without being an absolute method, SEC allows us to understand the molar mass distribution of a polymer. From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined and the polydispersity index (Ip = Mw / Mn) calculated via a so-called MOORE calibration.

[0090] Polymer preparation: There is no special treatment of the polymer sample before analysis. It is simply solubilized in chloroform, at a concentration of approximately 2 g / l. Then the solution is filtered through a 0.45 µm porosity filter before injection.

[0091] SEC Analysis: The apparatus used is an “Agilent 1200” chromatograph. The elution solvent is chloroform. The flow rate is 1 ml / min, the system temperature is 30°C and the analysis time is 30 min. A set of three Agilent columns in series preceded by a filter, with the commercial names “PLgel 10 µm (precolumn)” and two “PLgel 10 µm mixed B” are used. The injected volume of the polymer sample solution is 100 µl. The detector is an “Agilent 1200” differential refractometer and the chromatographic data processing software is the “Chemstation” system. The calculated average molar masses are relative to a calibration curve produced from commercial standard polystyrenes “Agilent-KIT PS”.

[0092] Proton Nuclear Magnetic Resonance (1H NMR): The determinations of the levels of the different monomer units and their microstructures within the copolymer 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 1H NMR experiment uses a simple 30° pulse sequence and a repetition delay of 5 seconds between each acquisition. The samples are solubilized in CDCl3. The integration zones considered for quantification are the spectral signature zones of the monomer units known to those skilled in the art. Differential scanning calorimetry (DSC): Measurement of the Tg of copolymers

[0093] The characterization of the Tg of the elastomer block and the polyalphamethylstyrene blocks is carried out by a DSC measurement (DSC1 device from Mettler Toledo). The device is operated under a helium atmosphere. A sample of 10 to 20 mg of TPE elastomer is placed in a hollow conventionally used by those skilled in the art to carry out Tg measurements.

[0094] 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 polyalphamethylstyrene blocks). In this measurement only the second heating is used. Method for measuring dynamic properties in deformation

[0095] The dynamic properties, complex moduli G*, are measured on a viscoanalyzer (Metravib DMA+ 450), according to the ASTM D 5992 - 96 standard. The response of a sample of desired composition (cylindrical specimen 2 mm thick and 78 mm2 in cross-section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz. A scan is carried out from -80°C to +150°C at a speed of 1.5° / min at a stress of 0.7 MPa.

[0096] The samples are molded at 180°C (diameter 25mm, thickness 2mm) for 5 minutes, then cut to a diameter of 10mm with a die cutter.

[0097] The complex modulus G* is measured.

[0098] The purpose of the examples is to verify the compatibility and selectivity of certain plasticizers used according to the invention with the elastomer phase of different thermoplastic elastomers.

[0099] The thermoplastic elastomers TPE1, TPE2 and TPE3 used are linear triblock copolymers with a polyalphamethylstyrene thermoplastic block / styrene-butadiene elastomer block / polyalphamethylstyrene thermoplastic block sequence. The so-called central block is therefore the elastomeric block in this macrostructure. Summary of TPE3:

[0100] In a 500 mL reactor, 20 g of methylcyclohexane, 10 g of alphamethylstyrene and 1.25 mmol of tetrahydrofurfurylethyl ether are introduced. After neutralization of the impurities with n-butyl lithium, 0.25 mmol of s-butyl lithium are introduced. After 2 h 30 at T = 5 °C, the conversion to alphamethylstyrene measured by dry extract is 70%. Analysis of the polymer by size exclusion chromatography shows the presence of a main population: Mn = 20,400 g / mol.

[0101] At the end of these 2 h 30 at 5 °C, 2 g of butadiene are introduced into the reactor then two minutes after this addition of butadiene, a mixture containing 16.75 g of butadiene and 100 g of methylcyclohexane whose impurities have been previously neutralized with n-butyl lithium is introduced into the reactor. The reaction medium is maintained at 5 °C for 15 minutes. At the end of these 15 minutes, the conversion to butadiene is 83%.

[0102] 0.12 mmol of dimethyldichlorosilane is then introduced into the reactor. The reaction medium is maintained at 5 °C for 30 minutes. The polymer obtained at the end of this coupling step is a poly(alphamethylstyrene)-b-polybutadiene-b-poly(alphamethylstyrene) triblock polymer which has a molar mass by SEC analysis: Mn = 139,600 g / mol and 2 Tg measured by DSC analysis: 181 °C and -25 °C.

[0103] TPE1 and TPE2 are prepared using a similar process.

[0104] The structures of the thermoplastic elastomers used according to the invention and tested are given in Tables 1 and 1bis. Table 1 Name·TPE¤ %Block· Thermoplastic· (PAMS)¤ %Block· Elastomer· (SBR)¤ %STY· / ·block· Elastomer¤ %PB1·-·2·· / · block· Elastomer¤ %PB1·-4· / · block· Elastomer¤ TPE1¤ 26.6¤ 73.4¤ 7.9¤ 76.9¤ 15.20 TPE2¤ 30.4¤ 69.6¤ 0.7¤ 87.8¤ 11.6¤ TPE3¤ 23.9¤ 76.1¤ 0.8¤ 80.1¤ 19.1¤ Table 1bis TPE name Mn SEC (g / mol) Ip SEC (g / mol) Tg DSC elastomer block (°C) Tg DSC bloc thermoplastic tick (°C) TPE1 113300 1.25 -8 175 TPE2 132400 1.05 -13 174 TPE3 139600 1.03 -25 181 %Thermoplastic Block (PAMS): % by mass of the polyalphamethylstyrene thermoplastic block in the TPE %Elastomer Block (SBR): % by mass of the SBR elastomer block in the TPE %STY / Elastomer block: % molar of styrene units in the elastomer block %PB 1-2 / Elastomer block: % molar of PB 1-2 units in the elastomer block %PB 1-4 / Elastomer block: % molar of PB 1-4 units in the elastomer block

[0105] Polymer compositions comprising a thermoplastic elastomer and a plasticizer in solution are prepared. In a 5L reactor equipped with a stirring blade, 100g of TPE and 20g of plasticizer are introduced for a composition containing 20pce of plasticizer. 2 liters of methylcyclohexane are added and the whole is stirred for 12 hours. The solution is recovered and dried under vacuum or stripped with water vapor to remove the solvent.

[0106] The plasticizers used are butadiene oligomers.

[0107] The characteristics of the plasticizers used are presented in Table 2.

[0108] Table 2a shows their contents in the compositions, the glass transition temperatures of the elastomer block and the polyalphamethylstyrene thermoplastic blocks of the thermoplastic elastomers in the compositions.

[0109] Finally, Table 2a presents the complex modules G* of the compositions. Table 2 Plasticizer name Mn plasticizer (g / mol) PB1 rate ,2 (%) bdf 1,5k (1) 1530 15.2 bdf 2,7k (2) 2700 12.9 bdf 4,7k (3) 4700 10.9 bdf 10k (4) 10000 7 bdf 18k (5) 18000 7.7 bdf 47k (6) 47000 7 bdt 1,5k (7) 1500 88 bdt 3,2k (8) 3200 80.4 Ricon 130 (9) 3400 22.9 Ricon 150 (10) 4300 42.1 Ricon 156 (11) 2000 50.3 Ricon 184 (12) 8600 26 Polybutadiene 5k (13) 5300 14 Polybutadiene 150k (14) 180000 4 (1)bdf 1.5k from PSS Polymer Standards Service GmbH (2)bdf 2.7k from PSS Polymer Standards Service GmbH (3)bdf 4.7k from PSS Polymer Standards Service GmbH (4)bdf 10k from PSS Polymer Standards Service GmbH (5)bdf 18k from PSS Polymer Standards Service GmbH (6)bdf 47k from PSS Polymer Standards Service GmbH (7)bdt 1.5k from PSS Polymer Standards Service GmbH (8)bdt 3.2k from PSS Polymer Standards Service GmbH (9)Ricon 130 from Cray Valley (10) Ricon 150 from Cray Valley (11) Ricon 156 from Cray Valley (12) Ricon 184 from Cray Valley containing between 10 and 16 mol% styrene (13) Polybutadiene 5k having a Mn of 5,300 g / mol, an Ip = 1.05, and having a percentage of PB 1,2 of 14% by mass (14) Polybutadiene 150k having a Mn of 150,000 g / mol, an Ip = 1.9, and having a percentage of PB 1,2 of 4% by mass, of PB1,4cis of 93% by mass and of PB1,4trans of 3% by mass PB 1.2 rate: molar rate of polybutadiene 1.2 units in the plasticizer,

[0110] Table 2bis shows that the plasticizers bdf 10k, bdf 18k, bdf47k, bdt 3.2k and polybutadiene 5k are compatible and selective with the elastomer phase because they significantly lower the Tg of the elastomer central block (or at least the ratio Tg(unplasticized TPE E block - Tg(plasticized TPE E block) / (Tg(unplasticized TPE E block) - Tg(plasticizer)) is important) without lowering the Tg of the thermoplastic blocks by more than 25°C.

[0111] Furthermore, the complex G* modules show a decrease in rigidity on the measured compositions, which confirms that the plasticizers according to the invention do indeed allow the rigidity of the composition to be adjusted.

Claims

1. Polymer composition comprising a) at least one block thermoplastic elastomer comprising at least one elastomer block and at least one thermoplastic block, the elastomer block(s) predominantly comprising units derived from butadiene and further comprise units derived from one or more styrene monomers, the thermoplastic block(s) consisting of units derived from one or more styrene monomers, b) at least one plasticizer selected from butadiene oligomers, it being understood that: b1) the molar content of 1,2-polybutadiene units in said plasticizer is within a range of from 70% to 130% of the molar content of 1,2-polybutadiene units in the elastomer block of the thermoplastic elastomer, and the molar mass Mn of the plasticizer is greater than 2000 g / mol, and less than 50 000 g / mol, or else b2) the molar content of 1,2-polybutadiene units in the plasticizer is less than 70%, or greater than 130%, of the molar content of 1,2-polybutadiene units in the elastomer block of the thermoplastic elastomer, and the molar mass Mn of the plasticizer is greater than 5000 g / mol, and less than 50 000 g / mol.

2. Polymer composition according to Claim 1, characterized in that the styrene monomer(s) of the elastomer block(s) are selected from styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene, beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethylstyrene, beta-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chlorostyrene, alpha-chloro-m-chlorostyrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorostyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, and styrene derivatives substituted with a silyl group.

3. Polymer composition according to Claim 2, characterized in that the styrene monomer(s) of the elastomer block(s) are selected from styrene and alpha-methylstyrene.

4. Polymer composition according to any one of the preceding claims, characterized in that the styrene monomer(s) of the thermoplastic block(s) are selected from styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene, beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethylstyrene, beta-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chlorostyrene, alpha-chloro-m-chlorostyrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorostyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, and styrene derivatives substituted with a silyl group.

5. Polymer composition according to Claim 4, characterized in that the thermoplastic block(s) predominantly comprise units derived from the alpha-methylstyrene monomer.

6. Polymer composition according to Claim 5, characterized in that the thermoplastic block(s) consist of units derived from the alpha-methylstyrene monomer.

7. Polymer composition according to any one of the preceding claims, characterized in that the thermoplastic block(s) consisting of units derived from one or more styrene monomers represent at most 35%, preferably from 10% to 35% by weight, relative to the weight of the thermoplastic elastomer.

8. Polymer composition according to any one of the preceding claims, characterized in that said plasticizer(s) represent from 5 to 50 phr, preferably from 5 to 30 phr, better still from 7 to 20 phr.

9. Tyre comprising a polymer composition as defined in any one of the preceding claims.