EP4076981A2

EP4076981A2 - Method for producing a rubber composition comprising a rubber crumb

Info

Publication number: EP4076981A2
Application number: EP20842282.4A
Authority: EP
Inventors: Etienne Fleury; Mathilde LACOSTE
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2019-12-18
Filing date: 2020-12-10
Publication date: 2022-10-26
Also published as: WO2021123574A2; CN115298041B; FR3105239A1; FR3105239B1; US20230028202A1; CN115298041A

Abstract

The invention concerns a method which responds to this problem scenario. The invention therefore relates to a method for producing a rubber composition based on at least one diene elastomer, a reinforcing filler, a rubber crumb and a crosslinking system, said method comprising at least the following steps: incorporating the reinforcing filler into the diene elastomer in one or more portions and mixing; when the temperature of the mixture reaches a temperature of more than 100°C, adding the rubber crumb; continuing mixing to a maximum temperature of between 120°C and 190°C; cooling the mixture to a temperature of less than 100°C; incorporating the crosslinking system, and mixing to a maximum temperature of less than 110°C.

Description

PROCESS FOR PREPARING A RUBBER COMPOSITION INCLUDING A RUBBER POWDER

The invention relates to the manufacture of rubber compositions comprising rubber powder, in particular for use in rubber articles, such as tires.

[002] It is interesting today for manufacturers to be able to reuse products made from recycled rubber in rubber articles. Rubber powder is of particular interest in this context since it results from the recycling by shredding of rubber articles. They are generally used as fillers in mixtures used to produce parts which are not subjected to high mechanical or dynamic stresses.

[003] It would nevertheless be interesting to be able to use them in more highly technical articles, by better controlling the properties of the compositions containing them. [004] As a result, it is necessary to know how to best prepare the rubber compositions which comprise rubber powder, in order to obtain the best possible performance for these compositions.

[005] It is known in the state of the art that rubber powder can be used in tires. For example, document WO2018 / 115714 A1 describes the use of certain rubber powder in compositions for tires. In this document, the compositions are prepared, in the usual manner for tire compositions, in two mixing stages called “non-productive phase” and “productive phase”. During the productive phase, all the ingredients except the crosslinking system are introduced at the same time, then mixed with a rise in temperature, and during the productive phase, the crosslinking system is added, with a lower rise in temperature.

[006] Also, document WO2010 / 039327 A1 proposes a process for preparing compositions in which the elastomers are mixed beforehand with the powder to form a masterbatch ("masterbatch" in English) then this mixture is used for the preparation of rubber compositions comprising all the ingredients.

[007] The known processes for the preparation of these compositions do not make it possible to combine a simplicity of preparation in two stages, with a minimum duration of the process, and good performance of the compositions, in particular in terms of fatigue and abrasion.

[008] Thus, a need for such solutions exists for manufacturers in the field, in order to have both the simplest and most economical process possible and good properties of the compositions.

[009] The Applicant has now found a method which addresses this problem. The invention therefore relates to a process for preparing a rubber composition based on at least one diene elastomer, a reinforcing filler, a rubber crumb and a crosslinking system, said process comprising at least the following steps: the diene elastomer in one or more times the reinforcing filler and mixing; when the temperature of the mixture reaches a temperature above 100 ° C, add the rubber crumb; continue mixing up to a maximum temperature between 120 ° C and 190 ° C; cooling the mixture to a temperature below 100 ° C; incorporate the crosslinking system and mix to a maximum temperature of less than 110 ° C.

The invention likewise relates to a process for preparing a rubber article implementing the process of the invention.

The invention also relates to a rubber article prepared according to the process of the invention, and preferably a tire comprising a composition prepared according to the process of the invention, preferably in all or part of its tread. In this case, the tire according to the invention will preferably be chosen from the tires intended to be fitted to a two-wheeled vehicle, a passenger vehicle, or even a so-called “heavy vehicle” (that is to say metro, buses, off-road vehicles, road transport vehicles such as trucks, tractors, trailers), or even airplanes, civil engineering, agrarian or handling equipment.

I- Constituents of the composition prepared by the process

The rubber compositions prepared according to the invention are based on at least one based on at least one diene elastomer, a reinforcing filler, a rubber crumb and a crosslinking system.

By the expression "composition based on" is meant a composition comprising the mixture and / or the in situ reaction product of the different basic constituents used, some of these constituents being able to react and / or being intended to react. between them, at least partially, during the various phases of manufacture of the composition, or during the subsequent cooking, modifying the composition as it is prepared at the start.

[0014] Furthermore, the term "phr" 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 curing. That is to say, in the case of the presence of a rubber crumb, the term "phr" means part by weight per hundred parts of "new" elastomers, therefore excluding from the base 100 the elastomers contained. in the rubber crumb.

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

When reference is made to a "majority" compound, it is understood within the meaning of the present invention that this compound is predominant among the compounds of the same type in the composition, that is to say that it is that which represents the largest quantity by mass among the compounds of the same type and in particular more than 50%, preferably more than 75%. Thus, for example, a majority polymer is the polymer representing the greatest mass relative to the total mass of polymers in the composition. Likewise, a so-called majority filler is that representing the greatest mass among the fillers of the composition. By way of example, in a system comprising a single polymer, the latter is in the majority within the meaning of the present invention; and in a system comprising two polymers, the majority polymer represents more than half of the mass of the polymers. On the contrary, a "minority" compound is a compound which does not represent the largest mass fraction among compounds of the same type.

When reference is made to a "major" unit (or monomer) within the same compound (or polymer), it is understood within the meaning of the present invention that this unit (or monomer) is predominant among units (or monomers) forming the compound (or polymer), that is to say that it is that which represents the largest fraction, by mass among the units (or monomers) forming the compound (or polymer). The compounds mentioned in the description can be of fossil origin or biobased. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This concerns in particular polymers, plasticizers, fillers, etc.

1-1 Elastomer

The elastomer can be selected from the group consisting of diene elastomers and mixtures thereof.

By elastomer (or indiscriminately rubber) "diene", whether natural or synthetic, should be understood in a known manner an elastomer consisting at least in part (ie, a homopolymer or a copolymer) of diene monomer units ( monomers bearing 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” is understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (% by moles); it is thus that diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the preceding definition and can in particular be qualified as "essentially saturated" diene elastomers (content of units of weak or very weak diene origin, always less than 15%).

The term "diene elastomer" is particularly intended to be used in the compositions in accordance with the invention:

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

(b) any copolymer of a diene, conjugated or not, having 4 to 18 carbon atoms and at least one other monomer. The other monomer can be ethylene, an olefin or a diene, conjugated or not.

Suitable conjugated dienes are conjugated dienes having from 4 to 12 carbon atoms, in particular 1, 3-dienes, such as in particular 1, 3-butadiene and isoprene.

Suitable olefins are vinyl aromatic compounds having from 8 to 20 carbon atoms and aliphatic α-monoolefins having from 3 to 12 carbon atoms. Suitable vinyl aromatic compounds, for example, are styrene, ortho-, meta-, para-methylstyrene, the commercial mixture “vinyl-toluene” and para-tert-butylstyrene.

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

[0027] More particularly, the diene elastomer can be:

(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 conjugated dienes with one another or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;

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

Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), polyisoprenes - synthetic (IR), or natural rubber (NR) -, butadiene copolymers, isoprene copolymers , and mixtures of these elastomers. Such butadiene copolymers and isoprene copolymers are more preferably respectively butadiene-styrene copolymers (SBR) and isoprene-styrene copolymers (SIR).

The rubber composition prepared according to the invention may contain a single diene elastomer or a mixture of several diene elastomers.

[0030] According to a preferred embodiment, the diene elastomer is a mixture of at least two diene elastomers chosen from the group consisting of polybutadienes, butadiene-styrene copolymers, natural or synthetic polyisoprenes.

The diene elastomer can be modified, that is to say either coupled and / or starred, or functionalized, or coupled and / or starred and simultaneously functionalized.

[0032] Thus, the diene elastomer can be coupled and / or star-shaped, for example by means of a silicon or tin atom which binds the elastomer chains together. The diene elastomer can be simultaneously or alternately functionalized and include at least a functional group. By functional group is meant a group comprising at least one heteroatom chosen from Si, N, S, O, P. Particularly suitable as functional groups are those comprising at least one function such as: silanol, an alkoxysilane, a primary amine , secondary or tertiary, cyclic or not, a thiol, an epoxide.

1-2 Reinforcing load

[0034] The composition according to the invention comprises a reinforcing filler. Any type of so-called reinforcing filler can be used, known for its ability 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 fillers.

Suitable carbon blacks are all carbon blacks, in particular the blacks conventionally used in tires or their treads. Among the latter, we can cite 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 N 115, N134 , N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as available commercially, 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 "filler" non-black ”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 a known manner, certain inorganic fillers reinforcers can be characterized in particular by the presence of hydroxyl (OH) groups at their surface.

As reinforcing inorganic fillers, suitable in particular mineral fillers of the siliceous type, preferably silica (Si02) or of the aluminous type, in particular alumina (Al203). The silica used can be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area as well as a CTAB specific surface area both less than 450 m2 / g, preferably within a range of from 30 to 400 m2 / g, in particular from 60 to 300 m2 / g. Any type of precipitated silica can be used, in particular highly dispersible precipitated silicas (called "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, which may or may not be highly dispersible, are well known to those skilled in the art. Mention may be made, for example, of the silicas described in applications W003 / 016215-A1 and W003 / 016387-A1. Among the commercial HDS silicas, it is possible in particular to use the silicas “Ultrasil 5000GR”, “Ultrasil 7000GR” from the company Evonik, the silicas “Zeosil 1085GR”, “Zeosil 1115 MP”, “Zeosil 1165MP”, “Zeosil Premium 200MP”, “Zeosil HRS 1200 MP” from the Solvay Company. As non-HDS silica, the following commercial silicas can be used: the silicas “Ultrasil VN2GR”, “Ultrasil VN3GR” from the company Evonik, the silica “Zeosil 175GR” from the company Solvay, the silicas “Hi-Sil EZ120G ( -D) ”,“ Hi-Sil EZ160G (-D) ”,“ Hi-Sil EZ200G (-D) ”,“ Hi-Sil 243LD ”,“ Hi-Sil 210 ”,“ Hi-Sil HDP 320G ”from the PPG company.

As other examples of inorganic fillers capable of being used in the rubber compositions of the invention may also be mentioned mineral fillers of the aluminous type, in particular alumina (Al203), oxides of 'aluminum, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications WO99 / 28376-A2, WOOO / 73372-A1, WO02 / 053634-A1, W02004 / 003067-A1, W02004 / 056915-A2, US6610261-B1 and US6747087-B2. Mention may in particular be made of the “Baikalox A125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals) aluminas.

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

Those skilled in the art will understand that, replacing the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, since this reinforcing filler of another nature would be covered with an inorganic layer such as silica, or else would comprise on its surface functional sites, in particular hydroxyls, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. By way of example, mention may be made of carbon blacks partially or completely covered with silica, or carbon blacks modified with silica, such as, without limitation, fillers of the “Ecoblack®” type of the series. CRX2000 ”or the“ CRX4000 ”series from Cabot Corporation.

A person skilled in the art will know how to adapt the total reinforcing filler 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 for a utility vehicle such as a van or weight heavy. Preferably, this level of total reinforcing filler is within 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 a known manner different according to the particular applications targeted.

[0044] According to a variant of the invention, the reinforcing filler is predominantly carbon black. Optionally according to this variant, the reinforcing filler can also comprise silica or another reinforcing inorganic filler.

In the present disclosure, the BET specific surface area is determined by gas paradsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from standard NF ISO 5794-1, annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160 ° C - range of relative pressure p / in: 0.05 to 0.17]

For inorganic fillers such as silica for example, the CTAB specific surface area values were determined according to standard NF ISO 5794-1, appendix G of June 2010. The process is based on the adsorption of CTAB (bromide of N-hexadecyl-N, N, N-trimethylammonium) on the "outer" surface of the reinforcing filler.

For carbon blacks, the STSA specific surface area is determined according to the ASTM D6556-2016 standard. 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 binding 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, at least bifunctional organosilanes or polyorganosiloxanes are used. By “bifunctional” is meant a compound having a first functional group capable of interacting with the inorganic filler 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 able to interact with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, the said second functional group being able to interact with the diene elastomer.

Preferably, the organosilanes are chosen from the group consisting of polysulphide organosilanes (symmetrical or asymmetrical) such as tetrasulphide.

[0050] bis (3-triethoxysilylpropyl), in short TESPT marketed under the name "Si69" by the company Evonik or bis- (triethoxysilylpropyl) disulfide, in short TESPD marketed under the name "Si75" by the company Evonik, the polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as octanethioate

S- (3- (triethoxysilyl) propyl) sold by the company Momentive under the name "NXT Silane". More preferably, the organosilane is a polysulfurized organosilane.

Of course, mixtures of the coupling agents described above could also be used.

The content of coupling agent in the composition of the invention is advantageously less than or equal to 35 phr, it being understood that it is generally desirable to use as little as possible. Typically the level of coupling agent represents from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler. Its level is preferably within a range ranging from 0.5 to 20 phr, more preferably within a range ranging from 3 to 3 phr. This level is easily adjusted by those skilled in the art according to the level of reinforcing inorganic filler used in the composition of the invention.

I-3 Cross-linking system In the composition of the invention, one can use any type of crosslinking system known to those skilled in the art for rubber compositions.

Preferably, the crosslinking system is a vulcanization system, that is to say based on sulfur (or on a sulfur donor agent) and on a primary vulcanization accelerator. To this basic vulcanization system can be added, incorporated during the first non-productive phase and / or during the productive phase as described later, various secondary accelerators or known vulcanization activators such as oxides. zinc, stearic acid or equivalent compounds, guanide derivatives (in particular diphenylguanidine). Sulfur is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5 phr, in particular between 0.5 and 3 phr.

The system for vulcanizing the composition according to the invention can also comprise one or more additional accelerators, for example compounds of the thiuram family, zinc dithiocarbamate derivatives, sulfenamides, guanidines or thiophosphates. In particular, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, in particular accelerators of the thiazole type as well as their derivatives, accelerators of the zinc thiuram or dithiocarbamate type. These accelerators are more preferably chosen from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyle sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (in abbreviated "ZBEC") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

1-4 Rubber crumb

[0058] The composition of the invention also comprises a rubber crumb (abbreviated "poudrette" in the following).

The powders are in the form of granules, optionally put in the form of a rubber plate. Most often, the rubber powders result from grinding or micronization of cured rubber compositions already used for a first application, for example in tires, they are a material recycling product. The powders are therefore preferably made up of of a composition based on at least one elastomer and one filler. 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 anisometric particles, of a few tens or hundreds of microns.

The rubber crumb preferably has an average size D50 of between 100 and 300 μm, and a particle size distribution such that the ratio of the average sizes D10 / D50 is greater than or equal to 0.5, preferably between 0 , 55 and 0.95 and more preferably between 0.6 and 0.9, and more preferably still between 0.65 and 0.85.

These specific powders can be obtained by various technologies, in particular by cryogenic micronization processes as described in documents US Pat. No. 7,445,170 and US Pat. No. 7,861, 958. According to another embodiment of the invention, the powders can be obtained by other micronization processes known to those skilled in the art and not limited to the cryogenic process alone.

[0063] Depending on the size distribution of objects obtained, the crumb obtained by the cited methods can undergo an additional sieving step so as to control this distribution. The sieving can be carried out by different technologies (vibration, centrifugation, suction) known to those skilled in the art.

Also, commercially available powder such as the “Polydine PD80” powder from the company Lehigh Technologies can be used.

Preferably, the powder is present at a rate within a range ranging from 5% to 40% by weight, preferably from 10% to 30% and more preferably from 15 to 25%. In a typical composition intended for tires, these mass levels correspond to levels of 5 to 100 phr. Preferably, the rate of powder is within a range ranging from 10 to 90 phr, preferentially from 15 to 90 phr, more preferably from 20 to 80 phr, and very preferably from 30 to 70 phr for optimum operation of the invention. .

As discussed above, the powders preferably consist of a composition based on an elastomer and a filler. They can also comprise all the ingredients usually used in rubber compositions such as plasticizers, antioxidants, vulcanization additives, and the like. [0067] Thus, the powder comprises an elastomer, preferably a diene elastomer. This elastomer preferably represents at least 30% by mass, more preferably at least 35% by mass, even more preferably at least 45% by mass of the weight of the crumb, a percentage determined according to the ASTM E1131 standard. It is preferably chosen from the group consisting of polybutadienes, polyisoprenes including natural rubber, butadiene copolymers and isoprene copolymers. More preferably, the molar content of units of diene origin (conjugated dienes) present in the diene elastomer is greater than 50%, preferably between 50% and 70%. According to a preferred embodiment of the invention, the powder contains between 5 and 80% by weight of filler, more preferably between 10% and 75%, and very preferably between 15% and 70%.

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 not 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 (by way of example, according to application WO2009 / 083160 paragraph 1.1). The weight average size of the micrometric particles can be determined by mechanical sieving.

By way of examples of fillers known to be reinforcing by a person skilled in the art, mention will in particular be made of carbon black or a reinforcing inorganic filler such as silica or alumina in the presence of a coupling agent, or their mixtures. [0071] According to a preferred embodiment of the invention, the powder comprises as 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 mass 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 crumb at a rate ranging from 20 to 40% by weight, more preferably from 25 to 35% by weight. Suitable carbon blacks are all carbon blacks, in particular blacks of the HAF, ISAF, SAF, FF, FEF, GPF and SRF type conventionally used in rubber compositions for tires (so-called tire grade blacks).

The powder can contain all the other usual additives which go 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, protection agents, vulcanizing agents. These additives can also be found in the crumb in the form of a residue or a derivative, since they may have reacted during the stages of manufacture of the composition or of crosslinking of the composition from which the crumb is derived.

[0076] The powders can be simple ground materials / micronisates of 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, etc. Preferably for the invention, a powder is used which has not undergone any modification by heat and / or mechanical, and / or biological and / or biological treatment. or chemical.

Regarding the constituents of the powder, it is preferred for the purposes of the invention that the powder has an acetone extract of between 3 and 30% by weight, more preferably between 3 and 15% by weight, more preferably between 3 and 10% by mass.

Also, it is preferable that the powder has a chloroform extract of between 3 and 85% by weight, more preferably between 3 and 20% by weight, more preferably between 5 and 15% by weight. Preferably, the chloroform extract of the rubber crumb has a mass average molecular mass (Mw) of less than 10,000 g / mol, preferably less than 8,000 g / mol. Preferably, in this type of powder, the ratio of the chloroform extract to the acetone extract, expressed as a percentage by mass, is less than 1.5. The characteristics of the rubber powder, as described above, are measured as indicated below.

Measuring the size of the crumb particles: The mass distribution of the size of the crumb particles can be measured by laser granulometry, on a device 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 the ISO-13320-1 standard and makes it possible to determine in particular the D10 and the D50, i.e. the average diameter below which respectively 10% by mass and 50% by mass of the population total particle size is present.

Measurement of the mass fraction of carbon black:

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

Measurement of the acetone extract: [0083] The level of acetone extract is measured according to the ISO1407 standard, using a soxhlet type extractor.

[0084] A 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 manifold of the soxhlet. The soxhlet is then assembled and then heated for 16 hours.

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

We can also calculate the level of elastomer, which corresponds to the level of organic matter determined by thermo-gravimetric analysis from which we subtract the level of acetone extract.

Measurement of the chloroform extract:

The rate of chloroform extract is measured according to the ISO1407 standard, using a soxhlet type extractor. A sample test portion (between 500 mg and 5 g) 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 manifold of the soxhlet. The soxhlet is then assembled and then heated for 16 hours. The sample is weighed after extraction. The rate of chloroform extract corresponds to the loss of mass of the sample during the extraction, relative to its initial mass.

Measurement of the average molecular masses of the chloroform extract:

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

The measurement of the weight average molecular mass (Mw) of the chloroform extract is carried out by size 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 5 pm) followed by 2 PL GEL MIXED E columns (300 x 7.5 mm 3 pm) from the company Agilent. These columns are placed in a column oven thermostatically controlled at 35 ° C. The mobile phase used is non-antioxidant tetrahydrofuran. The flow rate of the mobile phase is 1 ml / min. The RI detector is also thermostatically controlled at 35 ° C. The chloroform extract is dried under a stream of nitrogen. The dry extract is then taken up at 1 g / l in non-antioxidant tetrahydrofuran at 250 ppm for 2 hours with stirring. The solution obtained is filtered using a syringe and a 0.45 μm disposable PTFE syringe filter. 100 μl of the filtered solution is injected into the chromatographic system conditioned at 1 ml / min and 35 ° C. The results of Mw are provided by integration of the chromatographic peaks detected by an RI detector above a value of 2000 g / mol. The Mw is calculated from a calibration performed using standard polystyrenes.

I-5 Other possible additives

The rubber compositions in accordance with the invention optionally also include all or part of the usual additives usually used in elastomer compositions intended in particular for the manufacture of treads, such as for example pigments, protective agents such as as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, plasticizers (such as oils or plasticizing resins), anti-fatigue agents, reinforcing resins, methylene acceptors (eg phenolic novolak resin) or methylene donors (eg HMT or H3M).

Of course, the compositions prepared according to the invention can be used alone or as a blend (ie, as a mixture) with any other rubber composition which can be used for the manufacture of rubber articles, and according to a preferred embodiment, of tires. .

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

II- Process for the preparation of rubber compositions

The method of the invention uses, in a manner known to those skilled in the art, two successive preparation phases in suitable mixers; a first phase of thermo-mechanical work or mixing (sometimes qualified as "non-productive" phase) at high temperature, followed by a second phase of mechanical work (sometimes qualified as "productive" phase) at lower temperature, phase of finish in which the crosslinking system is incorporated; such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

The invention relates to a process for preparing a rubber composition based on at least one diene elastomer, a reinforcing filler, a rubber crumb and a crosslinking system, said process comprising at least the following steps: incorporating the reinforcing filler into the diene elastomer all at once or several times and mixing (step A); when the temperature of the mixture reaches a temperature above 100 ° C, add the rubber crumb (step B); continue mixing up to a maximum temperature of between 120 ° C and 190 ° C (step C); cooling the mixture to a temperature below 100 ° C (step D); incorporate the crosslinking system and mix to a maximum temperature of less than 110 ° C (step E).

It is understood that in the method of the invention, steps A to D correspond to the non-productive phase, while step E corresponds to the productive phase. If the prepared composition comprises other ingredients, optional, in addition to the diene elastomer, the reinforcing filler, the rubber crumb and the crosslinking system, these ingredients are preferably introduced during step A Preferably, they are incorporated simultaneously into the diene elastomer. Also preferably, they are incorporated simultaneously with the reinforcing filler.

[00101] One of the advantages of the invention is to understand the two usual preparation steps, without requiring the prior manufacture of a masterbatch, allowing optimum manufacturing time and simple equipment.

Preferably, during step A, the reinforcing filler is incorporated when the diene elastomer reaches a temperature above 50 ° C, preferably above 80 ° C.

Preferably, during step B, the rubber crumb is added when the mixture reaches a temperature above 110 ° C, preferably above 120 ° C. Preferably, during step C, the mixing is continued up to a maximum temperature of between 130 ° C and 180 ° C, preferably between 140 ° C and 170 ° C.

Preferably, during step D, the mixture is cooled to a temperature below 80 ° C, preferably below 60 ° C. Preferably, steps A to C are carried out in a first mixer, preferably an internal mixer.

Preferably, steps A to C are carried out over a period of time within a range ranging from 1 to 7 minutes, preferably from 2 to 5 minutes.

Preferably, step E is carried out in a second mixer, preferably an external mixer.

Preferably, step E is carried out over a period of time ranging from 5 to 15 minutes, preferably 8 to 12 minutes.

[00110] The final composition thus obtained can then be calendered, for example in the form of a sheet or of 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 products for tires. These products can then be used for the manufacture of rubber articles such as tires, according to techniques known to those skilled in the art.

The crosslinking (or curing) can be carried out in a known manner at a temperature generally between 130 ° C and 200 ° C, under pressure, for a sufficient time which can vary for example between 5 and 90 min depending in particular on the baking temperature, the crosslinking system adopted, the crosslinking kinetics of the composition considered or the size of the manufactured article.

The examples which follow illustrate the invention without, however, limiting it. III- Examples of realization of the invention

II 1-1 Characterization of rubber compositions

In the examples, the rubber compositions are characterized after curing as indicated below.

Fatigue: The resistance to fatigue, expressed in number of cycles or in relative unit (ur), is measured in a known manner on 12 test specimens subjected to repeated low-frequency traction up to an elongation of 75%, at 23 ° C, using a Monsanto device (“MFTR” type) until the specimen breaks, according to standards ASTM D4482-85 and ISO40 6943. [00115] The result is expressed in base 100 for easy comparison of results. A value greater than that of the control, arbitrarily set at 100, indicates an improved result, that is to say a better resistance to fatigue of the rubber samples.

Abrasion: [00116] The abrasion measurement can be carried out on an LAT100 abrasimeter, a device known to those skilled in the art, the result of which is a loss of mass per kilometer. The cylindrical test piece conforms to usual practice. It is applied with a fixed load of 75N for example against a circular track. This cylindrical specimen is subjected to a drift of 5.5 degrees. The speed of rotation of the abrasive disc is 12km / h.

The result is expressed in base 100 for easier comparison of the results. A value greater than that of the control, arbitrarily set at 100, indicates a improved result, ie better abrasion resistance of the rubber samples.

III-2 Rubber compositions

[00118] According to process P1, similar to that described in document WO2018 / 115714 A1, the compositions are manufactured in the usual way for tire compositions, in two mixing stages called “non-productive phase” and “productive phase”. During the non-productive phase, the elastomers, the reinforcing filler, the powder and the other ingredients except the crosslinking system are introduced into an internal mixer, at a temperature of 50 ° C. Mixing continues up to a temperature of 160 ° C. The total duration of the non-productive phase is approximately 3 minutes and 30 seconds. After cooling the mixture thus obtained, during the productive phase, the crosslinking system is incorporated at 30 ° C. in an external mixer (roller mixer); the whole is then mixed for 10 minutes. According to the method P2, similar to that described in the document

WO2010 / 039327 A1, the compositions are manufactured in three mixing stages, with two so-called “non-productive” phases and one so-called “productive” phase. During the first non-productive phase, the elastomers and the crumb are introduced into an internal mixer (laboratory, volume 3300cm3) at 50 ° C. Mixing continues for about 2 minutes up to a temperature of 110 ° C. A masterbatch is thus obtained. After cooling, a second non-productive phase is carried out, during which the masterbatch obtained in the first non-productive phase, the reinforcing filler and the other ingredients except the crosslinking system are introduced into an internal mixer at a temperature of 50 ° C. Mixing continues up to a temperature of 160 ° C. The total duration of the two non-productive phases is approximately 5 minutes and 30 seconds. After cooling the mixture thus obtained, the crosslinking system is incorporated during the productive phase at 30 ° C. in an external mixer (roller mixer); the whole is then mixed for 10 minutes. [00120] According to process P3, representative of the process of the invention, the compositions are manufactured in the usual way for tire compositions, in two mixing stages called “non-productive phase” and “productive phase”. During the non-productive phase, the elastomers are introduced into an internal mixer and mixed up to a temperature of 50 ° C. At a temperature of 90 ° C, the load reinforcing agent and the other ingredients except the powder and the crosslinking system are introduced. Then, at a temperature of 140 ° C, the crumb is added. Mixing continues up to a temperature of 160 ° C. The total duration of the non-productive phase is approximately 3 minutes and 30 seconds. After cooling the mixture thus obtained, during the productive phase, the crosslinking system is incorporated at 30 ° C. in an external mixer (roller mixer); the whole is then mixed for 10 minutes.

Compositions C1 and C2, presented in Table 1 were prepared according to the three different processes P1, P2 and P3, described above. The performances of these methods and compositions prepared are shown in Table 2.

It is noted in Table 2 that the compositions C1 and C2, when they are prepared by the method P3, according to the invention, have the best balance between their performance in abrasion and fatigue, while allowing an optimal duration of the process and therefore very good productivity.

Table 1

(1) NR: natural rubber (2) BR: polybutadiene “CB24” from the company Lanxess; 96% 1,4-cis; Tg = -107 ° C

(3) SBR with 22.5% by weight of styrene unit and for the butadiene part, 15% of unit 1, 2 and 15% of units 1, 4cis (Tg = - 52 ° C) (4) SBR with 15.5% by weight of styrene unit and for the butadiene part, 24% of unit 1, 2 and 28% of units 1, 4cis (Tg = - 65 ° C)

(5) Carbon black Grade ASTM N375

(6) Carbon black Grade ASTM N234 (7) “Polydine PD 80” powder from the company Lehigh Technologies

(8) N- (1, 3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (Santoflex 6-PPD) from the company Flexsys

(9) “Pristerene 4931” stearin from the company Uniqema

(10) Industrial grade zinc oxide - Umicore company (11) N-cyclohexyl-2-benzothiazol-sulfenamide (“Santocure CBS” from the company

Flexsys)

Table 2

Claims

1. Process for preparing a rubber composition based on at least one diene elastomer, a reinforcing filler, a rubber crumb and a crosslinking system, said process comprising at least the following steps A to E:

- step A: incorporate the reinforcing filler into the diene elastomer all at once or several times and mix,

- step B: when the temperature of the mixture reaches a temperature above 100 ° C, add the rubber crumb, - step C: continue mixing up to a maximum temperature between

120 ° C and 190 ° C,

- step D: cool the mixture to a temperature below 100 ° C,

- step E: incorporate the crosslinking system and mix to a maximum temperature below 110 ° C.

2. The method of claim 1 wherein during step A, the reinforcing filler is incorporated when the diene elastomer reaches a temperature above 50 ° C, preferably above 80 ° C.

3. A method according to any one of claims 1 or 2, wherein in step B, the rubber crumb is added when the mixture reaches a temperature above 110 ° C, preferably above 120 ° C.

4. Method according to any one of claims 1 to 3, wherein during step C, the mixing is continued up to a maximum temperature between 130 ° C and 180 ° C, preferably between 140 ° C. and 170 ° C.

5. A method according to any one of claims 1 to 4, wherein in step D, the mixture is cooled to a temperature below 80 ° C, preferably below 60 ° C.

6. Method according to any one of claims 1 to 5, wherein steps A to C are carried out in a first mixer, preferably an internal mixer.

7. A method according to any one of claims 1 to 6, wherein the steps

A to C are carried out over a period of time ranging from 1 to 7 minutes, preferably from 2 to 5 minutes.

8. A method according to any one of claims 1 to 7, wherein step E is performed in a second mixer, preferably an external mixer.

9. Method according to any one of claims 1 to 8, wherein step E is carried out over a period of time ranging from 5 to 15 minutes, preferably 8 to 12 minutes.

10. Method according to any one of the preceding claims, in which the rubber crumb has an acetone extract of between 3 and 30% by weight, preferably between 3 and 15% by weight, more preferably between 3 and 10% by weight.

11. Method according to any one of the preceding claims, in which the rubber crumb has a chloroform extract of between 3 and 85% by weight, preferably between 3 and 20% by weight, more preferably between 5 and 15% by weight.

12. Method according to any one of the preceding claims, in which the rubber crumb has a ratio of the chloroform extract to the acetone extract, expressed as a percentage by mass, of less than 1.5.

13. A method according to any preceding claim wherein the diene elastomer is selected from the group consisting of polybutadienes, polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.

14. A method according to any preceding claim wherein the diene elastomer is a mixture of at least two diene elastomers selected from the group consisting of polybutadienes, butadiene-styrene copolymers, natural or synthetic polyisoprenes.

15. A rubber article comprising a composition obtained by the method according to any one of the preceding claims.