WO2020128256A1

WO2020128256A1 - Tyre comprising a rubber composition having a pro-oxidant and a rubber crumb

Info

Publication number: WO2020128256A1
Application number: PCT/FR2019/053063
Authority: WO
Inventors: Nathalie COSTE; Séverin DRONET; Guillaume Hennebert
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 comprising a rubber composition based on at least one rubber crumb, a diene elastomer, a pro-oxidant, a reinforcing filler, and a cross-linking system, said rubber crumb representing 30% by mass or more of the composition, and having a ratio of chloroformic extract to 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 PRO-OXIDANT 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 W02010 / 039327 that tire compositions can also be prepared from masterbatches (“masterbatch” in English) comprising up to 50% by weight of crumb, said compositions comprising in these cases up to 17% by mass of crumbs, for example in composition R4 of this document.

Now, the Applicant has shown that very high quantities of crumb can be used in tire compositions. In particular, the Applicant has found a way to obtain excellent stiffness properties in compositions comprising a diene elastomer, a pro-oxidant and 30% 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, a diene elastomer, a pro-oxidant, a reinforcing filler, and a crosslinking system, said rubber crumb representing 30% by mass. or more of the composition, and having a ratio of the chloroform extract to the acetone extract of 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 so-called “heavy goods vehicle” (that is to say metro, bus, off-road vehicles -road, road transport equipment such as trucks, tractors, trailers), or even airplanes, civil engineering, agrarian or handling equipment.

Constituents of the composition

The rubber compositions for the tire according to the invention are based on at least one rubber crumb, a diene elastomer, a pro-oxidant, a reinforcing filler, and a crosslinking system, said rubber crumb representing 30% by mass. or more of the composition, and having a ratio of the chloroform extract to the acetone extract of 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 crumbs 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 mass-average molecular mass (Mw) greater than 10,000 g / mol. In regenerated crumbs, the ratio of chloroformic 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 30% by mass or more, preferably at a rate comprised in a range ranging from 30% to 90% by mass, preferably from 33% to 80 % and more preferably from 35% to 70%. Below 30%, 33% or even 35%, the rigidity would not be as improved on the one hand and the savings made would not be as attractive on the other hand. Thus, very preferably, the quantity of crumb is within a range ranging from 50% to 70% by mass.

These amounts, expressed in% by mass of composition, can also be expressed in the usual way for elastomeric compositions, in phr, relative to the amount of elastomer in the composition. The two ways of expressing the amount of crumb are used in the examples below.

Elastomer

By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in known manner an elastomer consisting at least in part (ie, a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not).

These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". In general, the term "essentially unsaturated" means a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (% by moles); This is how diene elastomers such as butyl rubbers or copolymers of dienes and of alpha-olefins of the EPDM type do not enter into the preceding definition and can be qualified in particular as “essentially saturated” diene elastomers (content of reasons of weak or very weak diene origin, always less than 15%).

The term “diene elastomer capable of being used in the compositions according to the invention” is understood to mean:

(a) - any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms;

(b) - any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and from at least one other monomer.

The other monomer can be ethylene, an olefin or a diene, conjugated or not. Conjugated dienes suitable are conjugated dienes having from 4 to 12 carbon atoms, in particular 1,3-dienes, such as in particular 1,3-butadiene and isoprene.

As non-conjugated dienes, non-conjugated dienes having from 6 to 12 carbon atoms are suitable, such as 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene.

As olefins suitable are vinyl aromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms.

Examples of vinyl aromatic compounds are styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tert-butylstyrene.

As aliphatic α-monoolefins suitable in particular are acyclic aliphatic α-monoolefins having from 3 to 18 carbon atoms.

More particularly, the diene elastomer is:

(a ') any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

(b ') any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms;

(c ') a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated, in particular chlorinated or brominated, versions of this type of copolymer;

(d ') any copolymer obtained by copolymerization of one or more dienes, conjugated or not, with ethylene, an α-monoolefin or their mixture such as for example the elastomers obtained from ethylene, from propylene with a diene monomer unconjugated of the above type.

Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these. elastomers. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). Preferably, the diene elastomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes and their mixtures.

Pro-oxidant

The rubber compositions according to the invention also comprise a pro-oxidant. These compounds are well known to those skilled in the art, sometimes also called peptisers or free radical generators, they are often associated with natural rubber in small amounts. The document W02010 / 039327 discussed above described for example in composition MB2 in Table 1 an amount of 0.15 phr of the DBD peptizer in the masterbatch.

For the purposes of the invention, the presence of such a pro-oxidant is necessary so that the composition comprising a very high level of rubber crumb has the improved rigidity specific to the invention.

For the invention, the pro-oxidant can be any pro-oxidant known to those skilled in the art. It is preferably chosen from the group consisting of the alkali, alkaline earth or lanthanide salts; iron salts; cobalt salts; thiols; organic disulfides and their mixtures.

In the family of alkaline earth, alkali or lanthanide metal salts, the pro-oxidant can advantageously be an acetylacetonate of an alkaline earth, alkali or lanthanide metal.

Preferably, the alkaline-earth, alkali or lanthanide metal of the salt is chosen from the group consisting of lithium, sodium, potassium, calcium, magnesium, lanthanum, cerium, praseodymium, neodymium, samarium , erbium and their mixtures. More preferably, the salt of an alkaline earth metal, alkali metal or lanthanide is a salt of magnesium or of neodymium. In other words, the salt of an alkaline earth, alkali or lanthanide metal is advantageously a magnesium or neodymium acetylacetonate, preferably a magnesium acetylacetonate.

In the family of iron salts, the pro-oxidant can advantageously be chosen from the group consisting of hemin, iron acetylacetonate and their mixtures.

In the family of cobalt salts, the pro-oxidant can advantageously be chosen from the group consisting of abietates, acetylacetonates, tallates, naphthenates, resinates and their mixtures. Preferably, the cobalt salt is Cobalt acetylacetonate (also called Peconal-H or Cobalt (ll) 4-oxopent-2-en-2-olate).

In the family of organic thiols and disulfides, the pro-oxidant can advantageously be chosen from the group consisting of 2,2 'dibenzamido-diphenyldisulfide (DBD), para-tertiobutylphenoldisulfide (APDS) and their mixtures.

The pro-oxidant is preferably chosen from the group consisting of iron salts; cobalt salts; organic disulfides and their mixtures.

Preferably, the pro-oxidant is selected from the group consisting of hemin, iron acetylacetonate, cobalt acetylacetonate, 2,2 'dibenzamido-diphenyldisulfide (DBD), para-tertiobutylphenoldisulfide (APDS) and their mixtures .

More preferably, the pro-oxidant is chosen from the group consisting of hemin, para-tertiobutylphenoldisulfide (APDS) and their mixtures. The level of pro-oxidant in the composition is preferably within a range ranging from 0.1 phr to 15 phr, preferably from 0.1 to 10 phr and more preferably from 0.15 phr to 5 phr. Below this quantity the effect of the pro-oxidant could be insufficient while a greater quantity no longer makes it possible to improve the rigidity and therefore proves to be unnecessary and expensive.

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 the diene elastomer, in particular isoprene, in the form of a masterbatch (see, for example, applications WO97 / 36724-A2 or WO99 / 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 connection between this reinforcing filler and the 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.

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

Preferably for the invention, the composition comprises from 10 to 80 phr of carbon black, more preferably from 30 to 70 phr. If necessary, 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 a 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 may 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.

Crosslinking system

The composition of the tire of the invention 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. It can in particular be based on sulfur, and / or peroxide and / or bismaleimides.

Preferably, 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, it is possible to use various known vulcanization activators such as zinc oxide, stearic acid or equivalent compound such as stearic acid salts and salts. of transition metals, guanidine derivatives (in particular diphenylguanidine), or also known vulcanization retarders.

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. 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 as anti-ozone, anti-ozonants, anti-oxidants, plasticizers, anti-fatigue agents, reinforcing resins, acceptors (for example phenol novolak resin) or methylene donors (for example 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 rubber compositions

The compositions are produced in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first working phase or thermo-mechanical kneading (sometimes called a "non-productive" phase) at high temperature, up to a maximum temperature of between 110 ° C and 200 ° C, preferably between 130 ° C and 180 ° C, followed by a second phase of mechanical work (sometimes called the "productive" phase) at a lower temperature, typically less than 110 ° C, for example between 60 ° C and 100 ° C, finishing phase during which the crosslinking or vulcanization system is incorporated; such phases have been described for example in applications EP A 0501227, EP A 0735088, EP A 0810258, W00005300 or W00005301.

The first (non-productive) phase is preferably carried out in several thermomechanical stages. During a first step, the elastomer and the pro-oxidant are introduced into a suitable mixer such as a usual internal mixer, at a temperature between 20 ° C. and 100 ° C. and, preferably, between 25 ° C. C and 100 ° C.

After a few minutes, preferably from 0.5 to 2 min and a rise in temperature to 90 ° C to 110 ° C, the crumb is added in one go or in parts.

After a few minutes, preferably from 0.5 to 2 min and a rise in temperature to 100 ° C to 120 ° C, the reinforcing fillers, the other ingredients (that is to say, those which remain if all do not have not been started) are added in one go or in parts, with the exception of the crosslinking system during mixing from 20 seconds to a few minutes.

The total duration of the kneading, in this non-productive phase, is preferably between 2 and 10 minutes at a temperature less than or equal to 180 ° C., and preferably less than or equal to 170 ° C. After cooling the mixture thus obtained, the crosslinking system is then incorporated at low temperature (typically less than 100 ° C.), generally in an external mixer such as a cylinder mixer; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min.

The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for 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 crosslinking of the composition can be carried out in a manner known to a person skilled in the art, for example at a temperature between 130 ° C. and 200 ° C., under pressure.

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, diluted 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 a device of the company Mettler Toledo model "TGA / DSC1". About 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.

Tensile tests (after baking)

These tensile tests make it possible to determine the moduli of elasticity and the properties at break and are based on standard NF ISO 37 of December 2005.

One measures at 23 ° C in second elongation (ie, after an accommodation cycle at the rate of extension provided for the measurement itself) the nominal secant module (or apparent stress, in MPa, related to the deformation, without unit ) at 10% elongation (noted MA10).

True stresses at break (in MPa) and elongations at break (in%) can also be measured.

Rubber compositions

The compositions are produced with an introduction of all the constituents on an internal mixer, with the exception of the vulcanization system, as described above. The vulcanizing agents (sulfur and accelerator) are introduced on an external mixer at low temperature (the cylinders constituting the mixer being at around 30 ° C). The powders can be introduced into the internal or external mixer.

The examples presented in Tables 1 to 6 are intended to compare the different rubber properties of the non-conforming compositions (T1 to T4) with the properties of the compositions according to the invention (C1 to C20). The quantities of the ingredients of the compositions are indicated in phr, and for the crumb a line has been added to indicate the quantity in% by mass as mentioned in Tables 1 to 6.

The MA10 modules measured for all the compositions are indicated in the last line of Tables 1 to 6, and it can be observed that the rigidity of the compositions in accordance with the invention is always improved compared to the non-conforming compositions.

References for table 1:

(1) NR: Natural rubber

(2) “OG80” crumb from the company CL PELLING having an acetone extract rate of 7.2% mol, a chloroform extract rate of 7.9% mol and a D50 of 180 pm

(3) Carbon black Grade ASTM N234

(4) Hemin from bovine, purity> 90%, from Aldrich

(5) Stearin “Pristerene 4931” from the company Uniqema

(6) Industrial grade zinc oxide - Umicore company

(7) N-cyclohexyl-2-benzothiazol-sulfenamide ("Santocure CBS" from the company Flexsys). [Table 1]

[Table 2

[Table 3]

[Table 4]

References for table 4:

(8) 2,2 'dibenzamido-diphenyldisulfide (DBD): "Renacit10" from the company Lanxess.

[Table 5]

References for table 5:

(9) para-tertiobutylphenoldisulfide (APDS): "Vultac TB7" from the company Arkema

(10) iron (III) acetylacetonate marketed by Aldrich

(11) hydrated cobalt (II) acetylacetonate sold by the company Aldrich. [Table 6]

References for table 6:

(12) IR: “SKI-3” from the company Nizhnekamsk

(13) SBR styrene content of 15%, content of 1.2: 25% of the butadiene part, Tg of -65 ° C.

Claims

1. A tire comprising a rubber composition based on at least one rubber crumb, a diene elastomer, a pro-oxidant, a reinforcing filler, and a crosslinking system, said rubber crumb representing 30% by mass or more of the composition, and having a ratio of chloroform extract to acetone extract 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 30% to 90% by mass and more preferably from 33% to 80% by mass.

3. A tire according to claim 2 in which the rubber crumb is present at a rate comprised in a range ranging from 35% to 70% by mass, preferably from 50% to 70% by mass.

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

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

6. Tire according to any one of the preceding claims, in which 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.

7. 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.

8. Tire according to any one of the preceding claims, in which the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures thereof; more preferably in the group consisting of natural rubber, synthetic polyisoprenes and their mixtures.

9. Tire according to any one of the preceding claims, in which the pro-oxidant is chosen from the group consisting of iron salts; cobalt salts; organic disulfides and their mixtures, preferably from the group consisting of alkali, alkaline earth or lanthanide salts; iron salts; cobalt salts; thiols; organic disulfides and their mixtures; and more preferably in the group consisting of hemin, iron acetylacetonate, cobalt acetylacetonate, 2,2 'dithiobisbenzanilide (DBD), tertiobutylphenoldisulfide (APDS) and their mixtures.

10. Tire according to any one of the preceding claims, in which the pro-oxidant is present at a rate comprised in a range ranging from 0.1 phr to 15 phr, preferably from 0.1 to 10 phr and more preferably from 0, 15 pce to 5 pce.

11. Tire according to any one of the preceding claims, in which the reinforcing filler is carbon black, preferably at a rate comprised in a range ranging from 10 to 80 phr, more preferably from 30 to 70 phr.