WO2020128257A1

WO2020128257A1 - Tyre having a rubber composition comprising a thermoplastic elastomer and a rubber crumb

Info

Publication number: WO2020128257A1
Application number: PCT/FR2019/053065
Authority: WO
Inventors: François LALLET; José Merino Lopez; Frédéric PIALOT; Maxime PRAS
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2018-12-19
Filing date: 2019-12-13
Publication date: 2020-06-25

Abstract

The invention relates to a tyre having a rubber composition based on at least one rubber crumb and a thermoplastic elastomer, wherein the rubber crumb is 50% by mass or more of the composition, and having a ratio of the chloroformic extract to the acetone extract of less than 2; the chloroformic and acetone extracts being expressed as percentages by weight.

Description

TIRE COMPRISING A RUBBER COMPOSITION COMPRISING A THERMOPLASTIC ELASTOMER AND A RUBBER POWDER

The invention relates to tires comprising at least one rubber composition comprising a rubber crumb.

Indeed, it is interesting today for tire manufacturers to find solutions to lower the costs of rubber compositions without penalizing the performance of tires using these compositions.

It is also of interest for manufacturers to promote the recycling of end-of-life tires into new tires with the aim of reducing the environmental impact of their activity.

The grinding or micronization of vulcanized rubber compositions produces granules or particles which are generally called rubber crumbs ("rubber crumbs" in English).

In this context, it is known in the state of the art that rubber crumbs can be used in tires. For example, the document WO2018 / 115715 proposes to use on the sidewall of the tire compositions which can comprise 23 phr, or 30 phr, or up to 50 phr or 54 phr of various crumbs. These amounts correspond to mass percentages of less than 25% by mass in the compositions. It is also known in document WO2010 / 039327 that tire compositions can also be prepared from masterbatches (“masterbatch” in English) comprising up to 50% by mass of crumb. These documents describe mixtures of crumb with diene elastomers.

Now, the Applicants have shown that very high quantities of crumb can also be used in tire compositions, in combination with thermoplastic elastomers. In particular, the Applicant has found a way to obtain excellent hysteresis and therefore rolling resistance properties in compositions comprising a thermoplastic elastomer, and 50% by mass or more of specific crumb.

The invention therefore relates to a tire comprising a rubber composition based on at least one rubber crumb and a thermoplastic elastomer, said rubber crumb representing 50% by mass or more of the composition, and having a ratio of chloroform extract. on the acetone extract less than 2; the chloroform and acetone extracts being expressed in percentages by mass.

Preferably, the tire according to the invention will be chosen from tires intended to equip a two-wheeled vehicle, a passenger vehicle, or even a vehicle said “heavyweight” (that is to say metro, bus, off-road vehicles, road transport vehicles such as trucks, tractors, trailers), or even planes, civil engineering, agrarian, or handling.

Constituents of the composition

The rubber compositions for the tire according to the invention are based on at least one rubber crumb and a thermoplastic elastomer, said rubber crumb representing 50% by mass or more of the composition, and having a ratio of chloroformic extract. on the acetone extract less than 2; the chloroform and acetone extracts being expressed in percentages by mass.

By the expression “composition based on” is meant a composition comprising the mixture and / or the in situ reaction product of the various basic constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the various stages of manufacturing the composition, or during subsequent cooking, modifying the composition as it is prepared at the start. Thus, the compositions as used for the invention may be different in the non-crosslinked state and in the crosslinked state.

Furthermore, the term "pce", well known to those skilled in the art, means within the meaning of the present patent application, part by weight per hundred parts of elastomers, within the meaning of the preparation of the composition before baking . That is to say, in the case of the presence of a rubber crumb in a composition, that the term “pce” means part by weight per hundred parts of “new” elastomers, therefore excluding from the base 100 the elastomers contained in the rubber crumb. Of course, the crumb itself has a rubber composition, the ingredients of which can also be expressed in phr, the term pce denoting in this case the quantity in parts by weight per hundred parts of elastomers, within the meaning of the composition proper of the powder.

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are percentages by mass. On the other hand, any range of values designated by the expression "between a and b" represents the range of values going from more than a to less than b (ie limits a and b excluded) while any range of values designated by the expression "from a to b" signifies the range of values going from a to b (that is to say including the strict limits a and b).

The compounds mentioned in the description can be of fossil origin or bio-based. In the latter case, they can be, partially or totally, from biomass or obtained from renewable raw materials from biomass. Are concerned in particular polymers, plasticizers, fillers, etc. Rubber crumb

The composition of the invention also comprises a rubber crumb (abbreviated as "crumb" in the following).

The crumbs are in the form of granules (or aggregates), possibly put in the form of a rubber plate. Most often the rubber crumbs come from a grinding or micronization of cooked rubber compositions already used for a first application, for example in tires, they are a product for recycling materials. Preferably the powders are in the form of microparticles.

By “microparticles” is meant particles which have a size, namely their diameter in the case of spherical particles or their largest dimension in the case of anisotropic particles, of a few tens or hundreds of microns.

The powders usually consist of a composition based on an elastomer and a filler. They also usually include all the ingredients used in the rubber compositions such as plasticizers, antioxidants, vulcanization additives, etc.

The crumbs can be simple crushed / micronized rubber, without further treatment. It is also known that these powders can undergo a treatment in order to modify them. This treatment can consist of a chemical modification of functionalization or devulcanization. It can also be a thermomechanical, thermochemical, biological treatment ...

Depending on the constituents of the powders and the treatment they may have undergone, they usually have an acetone extract of between 3 and 30% by mass, and a chloroform extract of between 5 and 85% by mass.

In certain documents, the use of special reclaimed rubber crumbs has been described, which have a morphology modified by heat and / or mechanical, and / or biological and / or chemical treatment. . These regenerated powders generally have an acetone extract of between 5 and 20% by mass, and a chloroform extract of between 15 and 85% by mass, the latter having a weight average molecular mass (Mw) greater than 10,000 g / mol. In regenerated crumbs, the ratio of chloroform extract to acetonic extract, expressed as a percentage by mass, is generally greater than or equal to 2. Finally, regenerated crumbs have a Mooney viscosity (conventionally expressed in Mooney unit, MU) generally between 40 and 90. These regenerated crumbs, if they have certain known advantages, result from a particular treatment which involves an additional cost of the product and technical characteristics resulting in other properties than the crumbs which have not undergone such treatment. As examples of such regenerated powders, mention may be made of the commercial products "Wuxi fine reclaim", which has an acetone extract rate of 9% and a chloroform extract rate of 37.2%; or “Nantong HT tire reclaim”, which has an acetone extract rate of 12.7% and a chloroform extract rate of 28.3%.

For the purposes of the invention, a specific crumb will be chosen, which has a ratio of the chloroform extract to the acetone extract of less than 2, and preferably less than or equal to 1.5; the chloroform and acetone extracts being expressed in percentages by mass.

Preferably, the powder has an acetone extract of between 3 and 15% by mass, more preferably included in a range ranging from 3 to 10% by mass.

Also, it is preferred that the powder has a chloroform extract of between 3 and 20% by mass, more preferably included in a range ranging from 5 to 15% by mass.

Preferably, the chloroform extract of the rubber crumb has a weight average molecular mass (Mw) of less than 10,000 g / mol, preferably less than 8,000 g / mol.

Also preferably, the crumb has an average particle size (D50) of between 10 and 400 μm, preferably between 50 and 250 μm and more preferably between 70 and 220 μm.

Preferably for the invention, the crumb which has not undergone any modification by thermal and / or mechanical, and / or biological and / or chemical treatment.

Preferably, the crumb useful for the invention comprises a diene elastomer. This elastomer preferably represents at least 30% by mass of the crumb, percentage determined according to standard ASTM E1131. It is preferably chosen from the group consisting of polybutadienes, polyisoprenes including natural rubber, butadiene copolymers and isoprene copolymers. More preferably, the molar level of units of diene origin (conjugated dienes) present in the diene elastomer is greater than 50%, preferably between 50% and 70%.

Preferably for the invention, the powder contains between 5 and 70% by mass of filler, more preferably between 10% and 60%, and very preferentially between 15% and 50%.

By filler is meant here any type of filler, whether it is reinforcing (typically with nanometric particles, and preferably of average size by weight less than 500 nm, in particular between 20 and 200 nm) or whether it is non-reinforcing or inert (typically with micrometric particles, and preferably of average size by weight greater than 1 μm, for example between 2 and 200 μm). The average size by weight of the nanometric particles is measured in a manner well known to those skilled in the art (for example example, according to request W02009 / 083160 paragraph 1.1). The average size by weight of the micrometric particles can be determined by mechanical sieving.

By way of examples of fillers known as reinforcing agents to those skilled in the art, mention may in particular be made of carbon black or an inorganic reinforcing agent such as silica or alumina in the presence of a coupling agent, or their mixtures.

According to a preferred embodiment of the invention, the crumb contains as a filler a reinforcing filler, in particular a carbon black or a mixture of carbon blacks.

The carbon black or the mixture of carbon blacks preferably represents more than 50%, more preferably more than 80%, even more preferably more than 90% by weight of the weight of the reinforcing filler of the crumb. According to a more preferred embodiment, the reinforcing filler consists of a carbon black or a mixture of carbon blacks.

Very preferably, the carbon black is present in the powder at a rate ranging from 20 to 40% by mass, more preferably from 25 to 35% by mass.

As carbon blacks, all carbon blacks are suitable, in particular blacks of the HAF, ISAF, SAF, FF, FEF, GPF and SRF type conventionally used in rubber compositions for tires (so-called pneumatic grade blacks).

The crumb can contain all the other usual additives which enter into a rubber composition, in particular for tires. Among these usual additives, mention may be made of liquid or solid plasticizers, non-reinforcing fillers such as chalk, kaolin, protective agents and crosslinking agents. These additives can also be found in the crumb in the form of a residue or derivative, since they may have reacted during the stages of manufacturing the composition or of crosslinking of the composition from which the crumb originated. In the powders useful for the invention, the crosslinking system is preferably a vulcanization system, that is to say based on sulfur (or a sulfur donor agent) and a vulcanization accelerator.

The powders useful for the invention are available commercially and those skilled in the art will be able to identify the powders useful for the invention, in particular by analyzing the chloroform and acetone extracts and their ratio, as discussed above. Suitable for the invention are “PD80” powders from the company Lehigh Technologies, which has an acetone extract rate of 7% and a chloroform extract rate of 7.3%; or “RNM60” from the company Rubber Resources, which has an acetone extract rate of 7.4% and a chloroform extract rate of 8.2%.

The crumb itself, if it is not directly purchased commercially, can be obtained according to techniques known to those skilled in the art of grinding or micronization. The grinding can be carried out by different technologies, for example by mechanical grinding process by a Kahl type grinding wheel, or even by cryogenic impact micronization technologies which make it possible to obtain small particles on rubber materials. Commercial equipment such as the CUM150 shredders from the company Netzsch or CW250 from the company Alpine can be used.

In the composition of the tire of the invention, the crumb is present at a rate of 50% by mass or more, preferably at a rate comprised in a range ranging from 50% to 95% by mass, preferably from 60% to 90 % and more preferably from 70% to 90%. Below 50%, the savings made would not be as attractive.

Thermoplastic elastomer

Thermoplastic elastomers (abbreviated as "TPE") combine the properties of thermoplastic polymers and elastomers. These are block copolymers, made up of rigid, thermoplastic blocks, connected to flexible, elastomeric blocks.

The thermoplastic elastomer used for the implementation of the invention is a block copolymer, the chemical nature of the thermoplastic blocks and elastomers can vary.

The number average molecular mass (denoted Mn) of the TPE is preferably between 30,000 and 500,000 g / mol, more preferably between 40,000 and 400,000 g / mol. Below the minima indicated, the cohesion between the TPE elastomer chains, in particular due to its possible dilution (in the presence of an extension oil), risks being affected; on the other hand, an increase in the temperature of use risks affecting the mechanical properties, in particular the properties at break, with the consequence of a reduced "hot" performance. Furthermore, an excessively high mass Mn can be penalizing for the implementation. Thus, it has been found that a value within a range of 50,000 to 300,000 g / mol is particularly well suited, in particular to the use of TPE in a composition for tires.

For styrenic TPEs, the number-average molecular mass (Mn) of the TPE elastomer is determined in known manner by steric exclusion chromatography (SEC). For example, in the case of styrenic thermoplastic elastomers, the sample is dissolved beforehand in tetrahydrofuran at a concentration of approximately 1 g / l; then the solution is filtered through a filter with a porosity of 0.45 μm before injection. The equipment used is a “WATERS alliance” chromatographic chain. The elution solvent is tetrahydrofuran, the flow rate of 0.7 ml / min, the system temperature of 35 ° C and the analysis time of 90 min. We use a set of four WATERS columns in series, with trade names "STYRAGEL"("HMW7","HMW6E" and two "HT6E"). The injected volume of the polymer sample solution is 100 µl. The detector is a "WATERS 2410" differential refractometer and its associated software for processing chromatographic data is the "WATERS MILLENIUM" system. Molar masses calculated averages relate to a calibration curve carried out with polystyrene standards. The conditions are adaptable by a person skilled in the art.

The value of the polydispersity index Ip (reminder: Ip = Mw / Mn with Mw weight average molecular weight and Mn number average molecular weight) of the TPE is preferably less than 3; more preferably less than 2 and even more preferably less than 1.5.

In known manner, the TPEs have two peaks of glass transition temperature (Tg, measured according to ASTM D3418), the lowest temperature being relative to the elastomeric part of the TPE, and the highest temperature being relative to the part TPE thermoplastic. Thus, the flexible blocks of TPE are defined by a Tg lower than ambient temperature (25 ° C), while the rigid blocks have a Tg greater than 80 ° C.

In the present application, when reference is made to the glass transition temperature of the TPE, it is the Tg relative to the elastomer block. The TPE preferably has a glass transition temperature ("Tg") which is preferably less than or equal to 25 ° C, more preferably less than or equal to 10 ° C. A Tg value greater than these minimums can reduce the performance of the composition when used at very low temperatures; for such a use, the Tg of the TPE is more preferably still less than or equal to 10 ° C. Also preferably, the Tg of the TPE is greater than -100 ° C.

To be both elastomeric and thermoplastic in nature, the TPE must be provided with sufficiently incompatible blocks (that is to say different due to their chemical nature, their polarity or their respective Tg) to maintain their own properties. elastomeric or thermoplastic block.

The TPEs can 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 15000 g / mol. These TPEs can be, for example, diblock copolymers, comprising a thermoplastic block and an elastomer block. They are also often triblock elastomers with two rigid segments connected by a flexible segment. The rigid and flexible segments can be arranged linearly, star-shaped or branched. Typically, each of these segments or blocks often contains at least more than 5, generally more than 10 repeating units (for example styrene units and butadiene units for a styrene / butadiene / styrene block copolymer).

The TPEs can also include a large number of smaller blocks (more than 30, typically from 50 to 500), in which case these blocks preferably have low masses, for example from 800 to 5000 g / mol, these TPEs will be called Multiblock TPE thereafter, and are a chain of elastomeric blocks - thermoplastic blocks. According to a first variant, the TPE is presented in a linear form. For example, TPE is a diblock copolymer: thermoplastic block / elastomer block. The TPE can also be a triblock copolymer: thermoplastic block / elastomer block / thermoplastic block, that is to say a central elastomer block and two terminal thermoplastic blocks, at each of the two ends of the elastomer block. Also, the multiblock TPE can be a linear chain of elastomeric blocks - thermoplastic blocks.

According to another variant of the invention, the TPE useful for the needs of the invention is in a star shape with at least three branches. For example, the TPE can 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 can vary, for example from 3 to 12, and preferably from 3 to 6.

According to another variant of the invention, the TPE is presented in a branched or dendrimer form. The TPE can then consist of a branched elastomer block or dendrimer and a thermoplastic block, located at the end of the branches of the elastomer dendrimer block.

The elastomeric blocks of TPE for the purposes of the invention may be any of the elastomers known to those skilled in the art. They generally have a Tg of 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 elastomer block of the TPE is greater than -100 ° C.

For carbon chain elastomer blocks, if the elastomer part of the TPE does not contain ethylenic unsaturation, we will speak of a saturated elastomer block. If the TPE elastomer block contains ethylenic unsaturations (that is to say carbon-carbon double bonds), then we will speak of an unsaturated or diene elastomer block.

A saturated elastomer block consists of a polymer block obtained by the polymerization of at least one (that is to say one or more) ethylenic monomer, that is to say comprising a carbon-carbon double bond. Among the blocks originating from these ethylenic monomers, mention may be made of polyalkylene blocks such as random ethylene-propylene or ethylene-butylene copolymers. These saturated elastomeric blocks can also be obtained by hydrogenation of unsaturated elastomeric blocks.

The elastomeric blocks can also be aliphatic blocks from the family of polyethers, polyesters, or polycarbonates.

C4-C14 conjugated dienes can be copolymerized with ethylenic monomers. In this case, they are random copolymers. Preferably, these conjugated dienes are chosen from isoprene, butadiene, 1-methylbutadiene, 2-methylbutadiene, 2,3-dimethyl-1,3-butadiene, 2,4-dimethyl-1,3 butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3 pentadiene, 2,3-dimethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-l , 3-hexadiene, 5-methyl-1,3-hexadiene, 2,3-dimethyl-1,3-hexadiene, 2,4-dimethyl-1,3-hexadiene, 2,5-dimethyl-1 , 3-hexadiene, 2-neopentylbutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-vinyl-1,3-cyclohexadiene or a mixture thereof. More preferably, the conjugated diene is chosen from butadiene or isoprene or a mixture containing butadiene and isoprene.

In the case of unsaturated elastomeric blocks, this TPE elastomeric block is preferably composed mainly of a diene elastomeric part. By predominantly, is meant a rate by weight of diene monomer which is highest relative to the total weight of the elastomer block, and preferably a rate by weight of more than 50%, more preferably of more than 75% and even more preferably of more than 85 %. Alternatively, the unsaturation of the unsaturated elastomer block can come from a monomer comprising a double bond and an unsaturation of cyclic type, this is the case for example in polynorbornene.

Preferably, conjugated dienes of C4 - C14 can be polymerized or copolymerized to constitute a diene elastomer block. Preferably, these conjugated dienes are chosen from isoprene, butadiene, piperylene, 1-methylbutadiene,

2-methylbutadiene, 2,3-dimethyl-1,3-butadiene, 2,4-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3 -methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 2,5-dimethyl-1,3-pentadiene, 2-methyl 1,4-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 2-methyl-1,5-hexadiene,

3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, 2,5-dimethyl-1,3-hexadiene, 2,5- 2,4-dimethyl-hexadiene, 2-neopentyl-1,3-butadiene, 1,3-cyclopentadiene, methylcyclopentadiene, 2-methyl-1,6-heptadiene, 1,3-cyclohexadiene, l-vinyl -1,3-cyclohexadiene or a mixture thereof. More preferably, the conjugated diene is isoprene or butadiene or a mixture containing isoprene and / or butadiene.

Alternatively, the monomers polymerized to form the elastomeric part of the TPE can be copolymerized, statistically, with at least one other monomer so as to form an elastomeric block. According to this variant, the molar fraction of polymerized monomer other than an ethylenic monomer, relative to the total number of units of the elastomer block, must be such that this block retains its elastomer properties. Advantageously, the molar fraction of this other co-monomer can range from 0 to 50%, more preferably from 0 to 45% and even more preferably from 0 to 40%.

By way of illustration, this other monomer capable of copolymerizing with the first monomer can be chosen from ethylenic monomers as defined above (for example ethylene), diene monomers, more particularly, conjugated diene monomers having 4 to 14 carbon atoms as defined above (for example butadiene), the vinylaromatic type monomers having from 8 to 20 atoms carbon as defined below or alternatively, it may be a monomer such as vinyl acetate).

When the co-monomer is of vinylaromatic type, it advantageously represents a fraction in units out of the total number of units in the thermoplastic block from 0 to 50%, preferably ranging from 0 to 45% and even more preferably ranging from 0 to 40%. By way of vinyl aromatic compounds, the styrene monomers mentioned above are suitable, namely methylstyrenes, para-tertio-butylstyrene, chlorostyrenes, bromostyrenes, fluorostyrenes or even para-hydroxy-styrene. Preferably, the vinylaromatic type co-monomer is styrene.

The glass transition temperature characteristic (Tg) of the rigid thermoplastic block will be used for the definition of the thermoplastic blocks. This characteristic is well known to those skilled in the art. It allows in particular to choose the temperature of industrial implementation (transformation). In the case of an amorphous polymer (or polymer block), the processing temperature is chosen to be substantially higher than the Tg of the thermoplastic block. In the specific case of a semi-crystalline polymer (or polymer block), a melting temperature can then be observed which is higher than the glass transition temperature. In this case, it is rather the melting temperature (Tf) which makes it possible to choose the processing temperature of the polymer (or polymer block) considered. Thus, later, when we speak of "Tg (or Tf, if applicable)", it should be considered that this is the temperature used to choose the processing temperature.

For the purposes of the invention, the TPE elastomers comprise one or more thermoplastic block (s) preferably having a Tg (or Tf, if applicable) greater than or equal to 80 ° C. and constituted from of polymerized monomers. Preferably, this thermoplastic block has a Tg (or Tf, if applicable) comprised in a range varying from 80 ° C to 250 ° C. Preferably, the Tg (or Tf, if applicable) of this thermoplastic block is preferably from 80 ° C to 200 ° C, more preferably from 80 ° C to 180 ° C.

Thermoplastic blocks having a Tg (or Tf, where appropriate) greater than or equal to 80 ° C. can be formed from polymerized monomers of various natures, in particular, they can constitute the following blocks or their mixtures: polyolefins (polyethylene, polypropylene); polyurethanes; polyamides; polyesters; polyacetals; polyethers (polyethylene oxide, polyphenylene ether); phenylene polysulfides; polyfluorinated (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethylmethacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene (ABS) copolymer.

The polystyrenes, preferred for the thermoplastic blocks of TPEs, are obtained from styrenic monomers. By styrenic monomer should be understood in the present description any monomer comprising styrene, unsubstituted as substituted; among the substituted styrenes, mention may be made, for example, of methylstyrenes (for example the methylstyrene, m-methylstyrene or p-methylstyrene, alpha-methylstyrene, alpha-2-dimethylstyrene, alpha-4-dimethylstyrene or diphenylethylene), para-tertio-butylstyrene, chlorostyrenes (for example o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene or 2,4,6-trichlorostyrene), bromostyrenes (for example o-bromostyrene , m-bromostyrene, p-bromostyrene, 2,4-dibromostyrene, 2,6-dibromostyrene or 2,4,6-tribromostyrene), fluorostyrenes (for example o-fluorostyrene, m-fluorostyrene , p-fluorostyrene, 2,4-difluorostyrene, 2,6-difluorostyrene or 2,4,6-trifluorostyrene) or para-hydroxy-styrene.

According to a preferred embodiment of the invention, the weight content of styrene in the TPE elastomer is between 5% and 50%. Below the minimum indicated, the thermoplastic nature of the elastomer may decrease appreciably while above the recommended maximum, the elasticity of the composition may be affected. For these reasons, the level of styrene is more preferably between 10% and 40%.

For example, TPE is a copolymer whose elastomer part is saturated, and comprising styrene blocks and alkylene blocks. The alkylene blocks are preferably ethylene, propylene or butylene. More preferably, this TPE elastomer is chosen from the following group, consisting of diblock, linear or star triblock copolymers: styrene / ethylene / butylene (SEB), styrene / ethylene / propylene (SEP), styrene / ethylene / ethylene / propylene (SEEP) ), styrene / ethylene / butylene / styrene (SEBS), styrene / ethylene / propylene / styrene (SEPS), styrene / ethylene / ethylene / propylene / styrene (SEEPS), styrene / isobutylene (SIB), styrene / isobutylene / styrene ( SIBS) and mixtures of these copolymers.

According to another example, TPE is a copolymer whose elastomeric part is unsaturated, and which comprises styrene blocks and diene blocks, these diene blocks being in particular isoprene or butadiene blocks. More preferably, this TPE is chosen from the following group, consisting of diblock copolymers, linear or star triblocks: styrene / butadiene (SB), styrene / isoprene (SI), styrene / butadiene / isoprene (SBI), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / butadiene / isoprene / styrene (SBIS) and mixtures of these copolymers.

Also for example, TPE is a linear or star copolymer, the elastomer part of which comprises a saturated part and an unsaturated part such as, for example, styrene / butadiene / butylene (SBB), styrene / butadiene / butylene / styrene (SBBS) or a mixture of these copolymers.

Among the multiblock TPEs, mention may be made of copolymers comprising random copolymer blocks of ethylene and propylene / polypropylene, polybutadiene / polyurethane (TPU), polyether / polyester (COPE), polyether / polyamide (PEBA).

As examples of commercially available TPE elastomers, mention may be made of the elastomers of the SEPS, SEEPS or SEBS type sold by the company Kraton under the name name "Kraton G" (eg products G1650, G1651, G1654, G1730) or the company Kuraray under the name "Septon" (eg "Septon 2007", "Septon 4033", "Septon 8004"); or the SIS type elastomers marketed by Kuraray, under the name "Hybrar 5125", or marketed by Kraton under the name "D1161" or else the linear SBS type elastomers marketed by Polimeri Europa under the name "Europrene SOLT 166" or Star SBS marketed by Kraton under the name "D1184". Mention may also be made of the elastomers marketed by the company Dexco Polymers under the name of “Vector” (eg “Vector 4114”, “Vector 8508”). Among the multiblock TPEs, there may be mentioned the “Vistamaxx” TPE marketed by the company Exxon; TPE COPE marketed by DSM under the name "Arnitel", or by Dupont under the name "Hytrel", or by Ticona under the name "Riteflex"; TPE PEBA marketed by Arkema under the name "PEBAX"; the TPU TPU marketed by the company Sartomer under the name "TPU 7840", or by the company BASF under the name "Elastogran".

Preferably for the invention, the thermoplastic elastomer is chosen from the group of styrenic thermoplastic elastomers, that is to say of which the thermoplastic block is a styrenic block. More preferably, the TPE is chosen from the group of unsaturated styrenic thermoplastic elastomers, that is to say of which the thermoplastic block is a styrenic block and whose elastomeric block is unsaturated. Even more preferably, the elastomeric block of TPE is a polybutadiene, or a random copolymer of butadiene and styrene.

Crosslinking

Optionally, the composition of the tire of the invention can be crosslinked by any means known to those skilled in the art.

One can in particular crosslink the composition by electron bombardment as described in document W02017 / 064091, or also by means of an organic peroxide as described in document W02018 / 091510, or also by sulfur vulcanization as described in document W02018 / 091514.

Thus preferably, the composition comprises a crosslinking system. As such, one can use any type of crosslinking system known to those skilled in the art for rubber compositions for tires. Preferably, the crosslinking system comprises sulfur or an organic peroxide.

According to a preferred embodiment, the crosslinking system is based on sulfur, this is called a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or of a sulfur donor. At least one vulcanization accelerator is also preferably present, and, optionally, also preferentially, various known vulcanization activators can be used such as zinc oxide, stearic acid or equivalent compound such as acid salts stearic and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or also known vulcanization retardants. Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr. The vulcanization accelerator is used at a preferential rate of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr.

Any compound capable of acting as an accelerator for vulcanization of diene elastomers in the presence of sulfur, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type can be used as accelerator. Examples of such accelerators include the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N, N-dicyclohexyl- 2-benzothiazyle sulfenamide ("DCBS"), N-ter-butyl-2- benzothiazyle sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyle sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD") , zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

According to another preferred embodiment, the crosslinking system comprises an organic peroxide. In a particularly preferred manner, the organic peroxide (s) which can be used according to the invention are chosen from dialkyl peroxides such as ditertbutyl peroxide (DTBP); dicumyl peroxide (Dicup); tertbutylcumyl peroxide and 2,5-dimethyl-2,5-di (tertbutylperoxy) hexane (DBPH), diacyl peroxides such as bis (2,4-di-chlorobenzoyl) peroxide (DCBP-50) and benzoyl peroxide (BP-50), acetal peroxides such as ethyl 3,3-di- (t-butylperoxy) butyrate), ester peroxides such as t-butyl peroxybenzoate and OO- (t-butyl) 0- (2-ethylhexyl) monoperoxycarbonate, hydroperoxides such as t-amyl hydro peroxide, and mixtures of these compounds. The level of peroxide is preferably within a range ranging from 0.1 to 10 phr, preferably from 0.2 to 6 phr, more preferably from 0.5 to 5 phr.

Reinforcing filler

The rubber composition of the invention may include one or more reinforcing fillers. Any type of reinforcing filler can be used, known for its capacity to reinforce a rubber composition which can be used in particular for the manufacture of tires, for example an organic filler such as carbon black, an inorganic filler such as silica or else a mixture of these two types of charges.

As carbon blacks, all carbon blacks are suitable, in particular the blacks conventionally used in tires or their treads. Among the latter, there may be mentioned more particularly the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (grades ASTM D-1765-2017), such as, for example, the blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a support for some of the rubber additives used. The carbon blacks could for example already be incorporated into a diene elastomer, in particular isoprene, in the form of a masterbatch (see for example applications W097 / 36724-A2 or W099 / 16600-A1).

As an example of organic fillers other than carbon blacks, mention may be made of organic fillers of functionalized polyvinyl as described in applications W02006 / 069792-A1, W02006 / 069793-A1, W02008 / 003434-A1 and W02008 / 003435-A1 .

By "reinforcing inorganic filler" should be understood here any inorganic or mineral filler, whatever its color and its 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 other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires. In known manner, certain reinforcing inorganic fillers can be characterized in particular by the presence of hydroxyl groups (OH) on their surface.

As reinforcing inorganic fillers, in particular mineral fillers of the siliceous type, preferably silica (SiO 2) or of the aluminous type, in particular alumina (Al 2 O 3) are suitable. The silica used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface as well as a CTAB specific surface both of which are less than 450 m 2 / g, preferably included in a range ranging from 30 to 400 m2 / g, in particular from 60 to 300 m2 / g.

Other examples of inorganic fillers which may be used in the rubber compositions of the invention may also be cited mineral fillers of the aluminous type, in particular alumina (Al 2 O 3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications W099 / 28376-A2, WOOO / 73372-A1, WO02 / 053634-A1 , W02004 / 003067-A1, W02004 / 056915-A2, US6610261-B1 and US6747087-B2.

The physical state in which the reinforcing inorganic filler is present is immaterial, whether in the form of powder, microbeads, granules, or even balls or any other suitable densified form. Of course, the term reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of silicas as described above.

Those skilled in the art will understand that, as a replacement for the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, as soon as this reinforcing filler of another nature is covered with an inorganic layer. such as silica, or else would have on its surface functional sites, in particular hydroxyls, requiring the use of a coupling agent to establish the bond between this reinforcing filler and diene elastomer. For example, carbon blacks include partially or completely covered with silica, or carbon blacks modified by silica, such as, without limitation, expenses type "Ecoblack ^®" Series CRX2000 ”or from the“ CRX4000 ”series from Cabot Corporation.

A person skilled in the art will know how to adapt the total reinforcing charge rate according to the use concerned, in particular according to the type of tire concerned, for example tire for a motorcycle, for a passenger vehicle or even for a utility vehicle such as a van or heavy vehicle. Preferably, this rate of total reinforcing filler is included in a range ranging from 10 to 200 phr, more preferably from 30 to 180 phr, and even more preferably from 40 to 160 phr; the optimum being in known manner different according to the particular applications targeted.

According to a variant of the invention, the reinforcing filler is mainly carbon black, that is to say that it comprises more than 50% by weight of carbon black relative to the total weight of reinforcing filler. According to a variant of the invention, the reinforcing filler consists of carbon black.

According to a variant of the invention, the composition does not contain a reinforcing filler.

For carbon blacks, the specific surface STSA is determined according to standard ASTM D6556-2016.

Preferably for the invention, the composition, when it comprises a filler, comprises from 5 to 80 phr of carbon black, more preferably from 30 to 70 phr.

Where appropriate, to couple the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a well known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure sufficient connection, of a chemical and / or physical nature. , between the inorganic filler (surface of its particles) and the diene elastomer. In particular organosilanes or polyorganosiloxanes which are at least bifunctional are used. By “bifunctional” is meant a compound having a first functional group capable of interacting with the inorganic charge and a second functional group capable of interacting with the diene elastomer. For example, such a bifunctional compound can comprise a first functional group comprising a silicon atom, the said first functional group being capable of interacting with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, the so-called second functional group being able to interact with the diene elastomer.

Other possible additives

The composition of the tire according to the invention can optionally also comprise all or part of the usual additives usually used in elastomer compositions intended in particular for the manufacture of tires, such as for example non-reinforcing fillers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, plasticizing agents, anti-fatigue agents, reinforcing resins, acceptors (for example novolak phenolic resin) or methylene donors (e.g. HMT or H3M).

It goes without saying that the invention relates to the rubber compositions described above, both in the so-called "raw" or non-crosslinked state (ie, before baking) and in the so-called "cooked" or crosslinked, or even vulcanized state ( ie, after crosslinking or vulcanization).

Preparation of the tire layers according to the invention

When the quantity of crumb is greater than 80% by mass of the composition of the tire of the invention, the preparation of this layer can be made by sintering of crumb.

By sintering of rubber crumb, it is understood a step of forming a predetermined quantity of crumb by heating to an elevated temperature and at the same time pressurizing this quantity of crumb in the cavity of a mold. The sintering step of the crumb takes place in a mold and, preferably without the addition of vulcanization additive. More particularly, it is a solid phase sintering of the grains of crumb, in other words, of a cohesion of the grains by heating at a high temperature of a compaction of the grains of crumb of rubber put under pressure. Heating and pressurizing the crumb creates a compact sintered agglomerate of crumb particles. Thus, the compression creates a physical approximation of the particles and the heating promotes molecular mobility and therefore this approximation via the interpenetration of the elastomer chains of the crumbs. Under the effect of temperature, there may also be splits of elastomeric chains, in particular on the surface of the crumbs. These elastomeric chains recombine with each other to create chemical bonds between the grains of rubber crumb, and ensure the cohesion of the material.

Preferably, the crumb and the thermoplastic elastomer are introduced into the mold and subjected to a nominal temperature between 100 ° C and 210 ° C, preferably from 150 ° C to 200 ° C, and at a nominal pressure between 20 and 200 bars for a period of time between 2 and 15 minutes.

A rubber profile is thus obtained, the shape and dimensions of which are defined by those of the sintering cavity of the mold, and the density of which is controlled, the latter being in direct connection with the compacting pressure of the crumb. These products can then be used for the manufacture of semi-finished products for the manufacture of tires, according to techniques known to those skilled in the art.

The sintering described above can thus be used when the level of crumb is greater than 80% by mass, in the presence of 20% of other ingredients such as thermoplastic elastomers. The preparation of the composition of the tire of the invention can also be done by the usual means of those skilled in the art for the preparation of the rubber compositions. In particular, the compositions can be manufactured in suitable mixers, by implementing a thermomechanical working or kneading phase at a temperature higher than the temperature Tg or Tf of the blocks of the TPE. The composition can also be obtained by extrusion-mixing at a temperature higher than the temperature Tg or Tf of the blocks of the TPE.

Such a preparation method can for example be used for compositions comprising, by mass, from 50% to 95% of crumb, preferably from 50% to 90% and in particular from 50% to 85%.

In the case where a crosslinking system is included in the composition, the thermomechanical working phase previously described can be followed by a second mechanical working phase (sometimes called "productive" phase) at a lower temperature, typically below 110 ° C, finishing phase during which the crosslinking system is incorporated.

The final composition thus obtained can then be calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or else extruded, to form for example a rubber profile used for the manufacture of semi -finished for tires. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

The examples which follow illustrate the invention without however limiting it.

Examples of embodiment of the invention

Characterization of the crumbs and rubber compositions of the examples

In the examples, the rubber crumbs are characterized as indicated below.

Particle size measurement:

The size of the particles (in particular the D50) can be measured by laser granulometry of the mastersizer 3000 type from the company Malverne. The measurement is carried out in a liquid way, dispersed in alcohol after a preliminary treatment of 1 min of ultrasound in order to guarantee the dispersion of the particles. The measurement is carried out in accordance with ISO-13320-1.

Measurement of the acetone extract:

The acetone extract rate is measured according to ISO1407 standard, using a soxhlet extractor.

A sample test sample (between 500 mg and 5g) is introduced into an extraction cartridge and then placed in the extractor tube of the soxhlet. A volume of acetone equal to two or three times the volume of the extractor tube is placed in the collector of the soxhlet. The soxhlet is then assembled and then heated for 16 hours.

The sample is weighed after extraction. The acetone extract rate corresponds to the loss of mass of the sample during extraction, compared to its initial mass.

Measurement of chloroform extract:

The chloroform extract rate is measured according to ISO1407, using a soxhlet extractor.

A sample test sample (between 500 mg and 5g) is introduced into an extraction cartridge and then placed in the extractor tube of the soxhlet. A volume of chloroform equal to two or three times the volume of the extractor tube is placed in the collector of the soxhlet. The soxhlet is then assembled and then heated for 16 hours.

The sample is weighed after extraction. The level of chloroform extract corresponds to the loss of mass of the sample during extraction, compared to its initial mass.

Measurement of the average molecular weights of the chloroform extract:

The molecular weights are determined by size exclusion chromatography, according to a Moore calibration and according to the ISO16014 standard.

The weight average molecular weight (Mw) of the chloroform extract is measured by steric exclusion chromatography (SEC) with a refractive index (RI) detector. The system consists of an Alliance 2695 chain from Waters, a column oven from Waters and an RI 410 detector from Waters. The set of columns used is composed of 2 PL GEL MIXED D columns (300 x 7.5 mm 5pm) followed by 2 PL GEL MIXED E columns (300 x 7.5 mm 3pm) from the company Agilent. These columns are placed in a column oven thermostatically controlled at 35 ° C. The mobile phase used is non-antioxidized tetrahydrofuran. The flow rate of the mobile phase is lml / min. The RI detector is also thermostatically controlled at 35 ° C.

The chloroform extract is dried under nitrogen flow. The dry extract is then taken up at lg / l in non-antioxidized tetrahydrofuran at 250 ppm for 2 hours with stirring. The solution obtained is filtered using a syringe and a 0.45pm syringe filter in disposable PTFE. 100 μl of the filtered solution is injected into the chromatographic system conditioned at lml / min and 35 ° C.

The Mw results are provided by integration of the chromatographic peaks detected by an RI detector beyond a value of 2000 g / mol. The Mw is calculated from a calibration carried out using standard polystyrenes. Measurement of the mass fraction of carbon black:

The measurement of the mass fraction of carbon black is made by a thermogravimetric analysis (ATG) according to standard NF T-46-07, on an apparatus of the company Mettler Toledo model "TGA / DSC1". Approximately 20 mg of sample is introduced into the thermal analyzer, then subjected to a thermal program from 25 to 600 ° C. under an inert atmosphere (pyrolyzable phase) then from 400 to 750 ° C. under an oxidizing atmosphere (oxidizable phase). The mass of the sample is measured continuously throughout the thermal program. The black content corresponds to the loss of mass measured during the oxidizable phase compared to the initial sample mass.

In the examples, the rubber compositions are characterized before and / or after curing as indicated below.

Dynamic properties (after cooking):

The dynamic properties and in particular the tan (5) max are measured on a viscoanalyzer (Metravib V A4000), according to standard ASTM D 5992 - 96. The response of a sample of vulcanized composition is recorded (cylindrical test piece of 4 mm d 'thickness and 400 mm2 section), subjected to a sinusoidal stress in alternating single shear, at the frequency of 10 Hz, at 23 ° C, according to standard ASTM D 1349 - 99. A sweep is carried out in amplitude of peak deformation at peak from 0.1 to 50% (outward cycle), then from 50% to 1% (return cycle). The exploited result is the loss factor (tan delta). For the return cycle, the maximum value of tan d observed (tan (delta) max) is indicated. For the maximum tan (delta) value at 23 ° C., the lower the value, the more the composition will have a low hysteresis and therefore a low rolling resistance.

Rubber compositions

The composition according to the invention is produced by extrusion-mixing at a temperature of 160 ° C. Alternatively, the compositions could be prepared in an internal mixer also at a temperature of 160 ° C or by sintering as described above. The control composition is produced with an introduction of all of the constituents (except the crosslinking ingredients) on an internal mixer, with a thermomechanical working phase up to a temperature of 130 ° C., a phase of introduction of the vulcanization at a lower temperature, and a baking phase at 150 ° C.

The examples presented in Table 1 are intended to compare the hysteresis of a non-conforming composition (T1) to that of a composition according to the invention (Cl). The amounts of the ingredients of the compositions are indicated in% by mass.

The maximum tan (delta) at 23 ° C. measured for all the compositions is indicated in the last line of Table 1, and it can be observed that the hysteresis of the composition conforms to the invention is improved compared to the non-conforming composition, a sign of reduced rolling resistance in tires.

[Table 1]

References for table 1:

(1) NR: Natural rubber

(2) SBS "DX1000-A" from Kraton

(3) "RNM60" crumb from the company Rubber Resources, which has an acetone extract rate of 7.4% and a chloroform extract rate of 8.2% and a D50 of 209 pm.

Claims

1. A tire comprising a rubber composition based on at least one rubber crumb and a thermoplastic elastomer, said rubber crumb representing 50% by mass or more of the composition, and having a ratio of the chloroformic extract to the extract acetone less than 2; the chloroform and acetone extracts being expressed in percentages by mass.

2. A tire according to claim 1, in which the rubber crumb is present at a rate comprised in a range ranging from 50% to 95% by mass, preferably from 60% to 90% and more preferably from 70% to 90%.

3. Tire according to any one of the preceding claims, in which the rubber crumb has a ratio of the chloroformic extract to the acetonic extract less than or equal to 1.5.

4. Tire according to any one of the preceding claims, in which the powder has an acetone extract of between 3 and 15% by mass, more preferably included in a range ranging from 3 to 10% by mass.

5. Tire according to any one of the preceding claims, in which the crumb has a chloroform extract of between 3 and 20% by mass, more preferably included in a range ranging from 5 to 15% by mass.

6. Tire according to any one of the preceding claims, in which the crumb has an average particle size (D50) of between 10 and 400 μm, preferably between 50 and 250 μm and more preferably between 70 and 220 μm.

7. Tire according to any one of the preceding claims, in which the thermoplastic elastomer is chosen from the group of styrenic thermoplastic elastomers, preferably from the group of unsaturated styrenic thermoplastic elastomers.

8. A tire according to the preceding claim, wherein the elastomeric block of the thermoplastic elastomer is a polybutadiene, or a random copolymer of butadiene and styrene.

9. Tire according to any one of the preceding claims, in which the the composition further comprises a crosslinking system comprising sulfur or an organic peroxide.

10. Tire according to any one of the preceding claims, in which the composition also comprises a reinforcing filler.