Rubber composition based on pyrolysis carbon black and epoxy resin

Abstract

The present invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler containing pyrolysis carbon black, a cross-linking system, between 1 and 30 phr of an epoxy resin and between 0.5 and 15 phr of a hardener.

Description

Description Title of the invention: RUBBER COMPOSITION BASED ON A PYROLYSIS CARBON BLACK AND AN EPOXY RESIN Technical field of the invention

[0001] The present invention relates to rubber compositions intended in particular for the manufacture of tires or semi-finished products for tires. The present invention also relates to a finished or semi-finished rubber article comprising a rubber composition according to the invention, as well as a pneumatic or non-pneumatic tire comprising at least one rubber composition according to the invention. Prior art

[0002] It is known to use in certain parts of pneumatic tires, rubber compositions having high rigidity during low deformations of the pneumatic tire as presented in application WO 02 / 10269. Resistance to low deformations is one of the properties that a pneumatic tire must have to respond to the stresses to which it is subjected.

[0003] This stiffening can be achieved by increasing the rate of reinforcing filler or by incorporating certain reinforcing resins into the rubber compositions constituting the parts of the tire.

[0004] The reinforcing resins conventionally used to increase the rigidity of rubber compositions are reinforcing resins based on a methylene acceptor / donor system. The terms "methylene acceptor" and "methylene donor" are well known to those skilled in the art and widely used to designate compounds capable of reacting together to generate, by condensation, a reinforcing resin in a three-dimensional network which is superimposed and interpenetrates with the reinforcing filler / elastomer network on the one hand and with the elastomer / sulfur network on the other hand (if the crosslinking agent is sulfur). Conventionally, the methylene acceptor is a phenolic resin.Novolac phenolic resins have already been used in rubber compositions, particularly intended for pneumatic tires or tire treads, for applications as varied as adhesion or reinforcement: see for example patent EP 0 649 446 Bl.

[0005] The methylene acceptor described above is combined with a curing agent capable of crosslinking or curing it, also commonly called a "methylene donor" or simply "hardener". Crosslinking of the resin is then caused during the curing of the rubber matrix, by formation of methylene bridges between the carbons in the ortho and para positions of the phenolic nuclei of the resin and the methylene donor, thus creating a three-dimensional resin network.

[0006] Application WO 2011 / 045342 describes rubber compositions comprising an epoxy resin pair with an amine hardener. These compositions, in addition to the advantage of avoiding the formation of formaldehyde, exhibit, after crosslinking, higher rigidities than conventional compositions while retaining acceptable rolling resistance. Application WO 2018 / 002538 describes rubber compositions comprising an epoxy resin and an amine hardener comprising at least two primary amine functions located on at least one six-atom aromatic ring which aim to improve the compromise between processability, in particular scorching time, and rigidity compared to known rubber compositions.

[0007] In order to minimize the environmental impact of the manufacturing of rubber products, particularly tires, new reinforcing fillers derived from the recycling of rubber products have been developed. These so-called "pyrolysis" carbon blacks have reinforcing properties. However, due to their nature, different from carbon blacks produced directly from fossil resources, so-called "ASTM blacks", the interactions between pyrolysis carbon blacks and other components of rubber compositions and their impact on the performance of rubber products are still poorly defined.

[0008] It is always desirable to further improve the properties of rubber compositions, and in particular the compromise between rigidity and hysteretic losses, without degrading the raw properties of these compositions, while minimizing the environmental impact of these compositions.

[0009] Unexpectedly, the Applicant discovered during its research that the combination of an epoxy resin and a pyrolysis carbon black makes it possible to improve the rigidity at low deformations and the hysteretic losses of a rubber composition without degrading the raw properties, in particular the viscosity of the compositions, while minimizing the environmental impact of such compositions. Detailed description of the invention Definitions

[0010] The carbon-containing compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This includes polymers, plas- tifiers, fillers, etc. Diene elastomers

[0011] The rubber composition according to the invention comprises at least one diene elastomer. By diene-type elastomer, it is recalled that it must be understood an elastomer which is derived at least in part (i.e. a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0012] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". "Essentially unsaturated" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or patterns of diene origin (conjugated dienes) which is greater than 15% (mol %); thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the preceding definition and can in particular be described as "essentially saturated" diene elastomers (low or very low content of patterns of diene origin, always less than 15% (mol %)). The diene elastomers included in the rubber composition according to the invention are preferably essentially unsaturated.

[0013] The term diene elastomer capable of being used in the rubber compositions in accordance with the invention is particularly 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 at least one other monomer.

[0014] The other monomer can be ethylene, an olefin, or a diene, conjugated or not.

[0015] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0016] Suitable olefins are vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0017] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene.

[0018] Suitable aliphatic α-monoolefins are, in particular, acyclic aliphatic α-monoolefins having 3 to 18 carbon atoms.

[0019] The diene elastomer is preferably a diene elastomer of the highly unsaturated type, in particular a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), polybutadienes (BR), butadiene copolymers, isoprene copolymers and blends of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-butadiene-styrene copolymers (SBIR), ethylene-butadiene copolymers (EBR) and blends of such copolymers.

[0020] The above diene elastomers can be, for example, block, random, sequenced, microsequenced, and can be prepared in dispersion or in solution; they can be coupled and / or star-shaped or even functionalized with a coupling and / or star-shaped or functionalizing agent, for example epoxidized.

[0021] Preferably, the rubber composition according to the invention comprises at least 50 phr, preferably at least 70 phr, preferably at least 90 phr of at least one isoprene elastomer. In a highly preferred embodiment, the elastomeric composition of the composite according to the invention comprises 100 phr of at least one isoprene elastomer.

[0022] By "isoprene elastomer" is meant a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR) which can be plasticized or peptized, synthetic polyisoprenes (IR), the various copolymers of isoprene, in particular copolymers of isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR), and mixtures of these elastomers.

[0023] Preferably, the isoprene elastomer is chosen from the group consisting of synthetic polyisoprenes, natural rubber, isoprene copolymers and their mixtures, preferably from the group consisting of natural rubber, polyisoprenes comprising a mass content of cis 1,4 bonds of at least 90%, more preferably of at least 98% relative to the mass of isoprene elastomer and their mixtures. Very preferably, the isoprene elastomer is natural rubber.

[0024] In the rubber compositions according to the invention, the elastomer represents a continuous phase within which the other constituents are dispersed. Epoxy resin

[0025] The rubber composition according to the invention comprises between 1 and 30 pce of an epoxy resin.

[0026] The epoxy resins that can be used in the present invention include all polyepoxide compounds. These may be, for example, aromatic epoxy resins, alicyclic epoxides, and aliphatic epoxides. For example, the aromatic epoxy resin may be an amine-aromatic epoxy resin. These resins are preferably novolac epoxy resins, i.e. epoxy resins obtained by acid catalysis, as opposed to resol resins, obtained by basic catalysis.

[0027] Particularly preferred among the aromatic epoxy compounds are epoxy resins selected from the group consisting of 2,2 bis[4-(glycidyloxy)phenyl]propane, poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane and mixtures of these resins.

[0028] By "epoxy resin type" is meant resins based on units of the constituent, i.e. comprising this constituent, or oligomers of this constituent.

[0029] Epoxy resin is a curing resin. A curing resin is a resin that, when incorporated into a rubber composition with a curing agent, increases the rigidity of the rubber composition after crosslinking. However, increasing the rigidity of a rubber composition generally goes hand in hand with an increase in hysteretic losses.

[0030] More preferably, the epoxy resin is chosen from the group consisting of poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane type resins and mixtures of these resins.

[0031] Very preferably, the epoxy resin used in the context of the invention is chosen from the following epoxy resins of generic formula (I) and (II) and their derivatives, i.e. the oligomers of the compounds of generic formula (I) and (II):

[0032] n being an integer expressing the degree of polymerization, n ranging from 1 to 15, preferably from 1 to 10, more preferably from 1 to 5 and very preferably from 1 to 3.

[0033] Examples of commercially available epoxy resins that can be used in the context of the present invention include, for example, the epoxy resin “DEN 439” from the company Uniqema, the epoxy resin “Tris(4-hydroxyphenyl)methane triglycidyl ether” from the company Sigma-Aldrich, the araldite cresol novolac epoxy resin “ECN 1299” from the company Huntsman, the araldite phenol novolac epoxy resin “EPN 1138” from the company Huntsman, the resins “EPPN-502H”, “EPPN-501H” and “EPPN-501HY” from the company Nippon Kayaku, or the resin “EPON 1031” from the company Hexion.

[0034] Preferably, the rubber composition according to the invention does not comprise any hardening resins other than an epoxy resin, and in particular does not comprise any resins of the formophenolic type.

[0035] The amount of epoxy resin is between 1 and 30 phr. Given the amine hardener used in the context of the present invention, below the minimum level of epoxy resin indicated, the intended technical effect is insufficient, whereas above the maximum indicated, there is a risk of excessively high rigidity and excessive penalization of hysteresis and Mooney plasticity. More preferably, the level of epoxy resin in the rubber composition according to the invention is between 10 and 28 phr. The epoxy resin contents of the present invention make it possible to ensure sufficient stiffening of the rubber composition while allowing it to retain elastic-type behavior once crosslinked. Hardener

[0036] The rubber composition according to the invention comprises from 0.5 to 15 phr of a hardener. Any hardener capable of crosslinking the epoxy resin used in the rubber compositions according to the invention may be suitable as a hardener. In particular, the hardener may be chosen from aromatic diamines, aliphatic diamines, anhydrides such as, for example, benzoic anhydride and maleic anhydride, and ureas.

[0037] Urea hardeners are compounds of general formula (R b R2)N-CO-N(R3, R4) or (Ri, R2)N-CO-(NR3)-R7-(NR4)-CO-N(R5, R6) in which each radical R B at R6 is chosen independently from the group consisting of: • a hydrogen atom, • an alkyl radical having from 1 to 20 carbon atoms, • a cycloalkyl radical having from 5 to 24 carbon atoms, • an aryl radical having from 6 to 30 carbon atoms and • an aralkyl radical having from 7 to 25 carbon atoms.

[0038] In the general formula (R B R2)N-CO-N(R3, R , we understand that the CO group represents a carbon atom linked by a double bond to an oxygen atom, that the group (R B R2)N (respectively N(R3, R ) represents a nitrogen atom linked to a Ri group and to an R2 group by a covalent bond. Such a molecule is represented below.

[0039] In the general formula (R b R2)N-CO-(NR3)-R7-(NRJ-CO-N(R5, RJ, it is understood that the CO group represents a carbon atom linked by a double bond to an oxygen atom, that the group (R bRJN (respectively N(R5, R6)) represents a nitrogen atom linked to a group Ri and to a group R2 by a covalent bond, that the group (NRJ (respectively (NRJ) represents a nitrogen atom linked to a group R3 by a covalent bond and that the group R7 represents a divalent group linked on the one hand to the nitrogen atom carrying the group R3 and on the other hand to the nitrogen atom carrying the group R4.

[0040] Preferably, the hardener is chosen from aromatic diamines and ureas. These families of hardeners in fact present a compromise between crosslinking speed during curing / rigidity of the crosslinked product which is particularly interesting for the rubber compositions according to the invention.

[0041] Very preferably, according to the invention, the aromatic diamine hardener is chosen from the group consisting of the compounds below and mixtures of these compounds:

[0042] Examples of commercially available amine hardeners that can be used in the context of the present invention include, for example, “Ethacure 100” or “Ethacure 300” from Albemarle, “Lonzacure DETDA”, “Lonzacure MDEA” or “Lonzacure MCDEA” from the Lonza company.

[0043] Preferably, the ureas do not comprise an aromatic nucleus.

[0044] Preferably, each radical R h R2, R3 and R4 are hydrogen atoms. The compound with the formula H2N-CO-NH2 is commonly referred to as "urea" or "carbamide".

[0045] Preferably, in the compound of general formula (R B R2)N-CO-(NR3)-R7- (NR4)-CO-N(R5, R6), the radicals R bR2, R5and R6are methyl radicals, R3and R4are hydrogen atom and R7is a bivalent methylphenyl radical. An example of such a diurea compound is the compound Amicure UR2T from the company Evonik, with the formula 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea).

[0046] Very preferably, according to the invention, the ureas are chosen from the compounds carbamide, N, N'-dimethylurea, ethyleneurea, N-phenylurea, 1,3-diphenylurea, 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea), preferably chosen from the compounds urea, N, N'-dimethylurea, N-phenylurea, 1,3-diphenylurea, 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea) and very preferably chosen from the compounds carbamide and N, N'-dimethylurea and 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea) and very preferably is carbamide, also called urea, of formula H2N-CO-NH2.

[0047] The amount of hardener in the rubber composition is in the range from 0.5 to 15 pce. Below the minimum indicated, the intended technical effect has proven insufficient, while above the maximum indicated, there is a risk of penalizing the processing of the rubber compositions in the raw state. Preferably, the hardener content is in the range from 0.5 to 10 pce, preferably in the range from 0.5 to 8 pce. Pyrolysis carbon black

[0048] The rubber composition according to the invention comprises a reinforcing filler comprising pyrolysis carbon black, preferably comprising predominantly pyrolysis carbon black. By predominantly, it is meant that the pyrolysis black represents at least 50% by weight of the total weight of reinforcing filler. Preferably, the pyrolysis black represents at least 70% by weight of the total weight of reinforcing filler, preferably at least 80% by weight of the total weight of reinforcing filler, more preferably at least 90% by weight of the total weight of reinforcing filler. Very preferably, the reinforcing filler consists of pyrolysis black.

[0049] For the purposes of the present invention, the term "pyrolysis carbon black" means a carbon black resulting from a process for the pyrolysis of a carbonaceous polymeric material comprising at least one polymer and one carbon black, hereinafter the material to be pyrolyzed, this material possibly resulting from recycling. Recycling means a process which makes it possible to treat a product which has been used or not in order to reintroduce some of these materials in the production of new objects. By "carbon polymeric material" is meant a material comprising at least one polymer based on hydrogen and carbon. The physical state in which this material to be pyrolyzed is present is indifferent, whether in the form of powder, granules, strip, or any other suitable densified form, crosslinked or not.

[0050] Preferably, the material to be pyrolyzed may be recovered from manufactured articles or products generated during their manufacture / production (such as by-products or scraps); these manufactured articles may be chosen from the group consisting of pneumatic tires, non-pneumatic tires, industrial conveyor belts, transmission belts, rubber seals, rubber hoses, shoe soles and windshield wipers. Even more preferably, the pyrolysis carbon black that can be used in the context of the present invention is a carbon black obtained from a pyrolysis process in which the material to be pyrolyzed is derived from manufactured articles chosen from the group consisting of pneumatic tires and non-pneumatic tires.

[0051] Pyrolysis in the context of the present invention means any type of thermal decomposition in the absence of oxygen and whose raw material is the material to be pyrolyzed as defined above. Pyrolysis carbon blacks are therefore distinguished from so-called industrial and / or ASTM grade carbon blacks in that the carbon raw material used for pyrolysis is a material comprising at least one carbon polymer and one carbon black and not materials derived from petroleum fractions or from coal or from oils of natural origin.

[0052] Pyrolysis carbon blacks are marketed, for example, by the company BlackBear under the reference “BBCT30” or by the company Scandinavian Enviro Systems under the reference “P550”.

[0053] The pyrolysis carbon blacks that can be used in the context of the present invention are distinguished from known carbon blacks such as industrial carbon blacks, in particular so-called “fumac” carbon blacks, in particular by a higher ash content.

[0054] Preferably, the pyrolysis carbon black usable in the context of the present invention has an ash content within a range of 5 to 30% by weight, more preferably ranging from 8 to 25% by weight, even more preferably ranging from 10% to 22% by weight, relative to the total weight of the pyrolysis carbon black.

[0055] Preferably, the pyrolysis carbon black usable in the context of the present invention also has a sulfur content greater than 2% by weight, preferably ranging from 2.5 to 5% by weight, relative to the total weight of the pyrolysis carbon black.

[0056] Preferably, the pyrolysis carbon black usable in the context of the present invention also has a zinc content greater than or equal to 2% by weight, preferably ranging from 2.5 to 8% by weight, relative to the total weight of the pyrolysis carbon black.

[0057] Preferably, the pyrolysis carbon black usable in the context of the present invention has a specific surface area STSA measured according to the ASTM D 6556-2021 standard within a range from 20 to 200 m 2 / g, more preferably ranging from 30 to 90 m 2 / g.

[0058] Preferably, the pyrolysis carbon black usable in the context of the present invention has a void volume measured according to standard ASTM D7854 (2018) and at a pressure of 50 MPa within a range from 30 to 60 ml / 100g, more preferably from 35 to 55 ml / 100g.

[0059] The ash content is determined by calcination in platinum capsules in a muffle furnace at 825°C according to the following protocol. A capsule is previously identified before each series of measurements and is tared to the nearest 0.1 mg and the mass is noted PO. In the capsule, 5 g of pyrolysis carbon black sample is introduced. The capsule is weighed precisely to the nearest 0.1 mg; this mass is noted PI. The capsule and its contents are pre-calcined using a Bunsen burner until fumes appear and the product ignites. Once the product has completely burned, the capsule and its contents are introduced into a muffle furnace heated to 825°C for 1 h. After 1 h, the capsule is removed from the furnace and immediately placed in a desiccator at room temperature. When the capsule and the ash have returned to room temperature, the capsule is weighed again to obtain the mass P2.Finally, it is possible to obtain the ash content (% ash) using the formula below:.

[0060] % ash 100

[0061] The zinc content in the pyrolysis black is measured after calcination of the sample, then recovery of the ash in an acid medium and determination by ICP-AES (inductively coupled plasma atomic emission spectroscopy). The ash contents are obtained by carrying out the protocol already described above. 100 mg of ash (test sample) is taken and placed in a PFA (perfluoroalkoxy) tube for a HotBlock hot plate. Then 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid and 0.5 mL of 40% hydrofluoric acid are added. The tube is closed with its cap and heated at 130 °C for 2 h. After cooling, the contents are then transferred using ultrapure water into a 100 mL PTFE (polytetrafluoroethylene) graduated flask already containing 2 g of boric acid (to neutralize the hydrofluoric acid). The volume is topped up with ultrapure water to the mark. The resulting solution is diluted per 100, by taking 1 mL from a 100 mL PFTE flask, previously containing 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid, 0.5 mL of 40% hydrofluoric acid and 2 g of boric acid. This diluted solution is then filtered through a 0.45 pm GHP syringe filter before being analyzed by ICP-AES. Prior to the analysis of the diluted solution, at least 5 standards are analyzed by ICP-AES at zinc concentrations of 0, 0.5, 1, 2 and 5 mg / L. These standards were prepared in 100 mL volumetric flasks, by diluting a certified commercial solution to a zinc concentration of 1 g / L.

[0062] These volumetric flasks first contain 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid, 0.5 mL of 40% hydrofluoric acid and 2 g of boric acid. The standard solutions are analyzed by ICP-AES at a wavelength of / .Zn = 202.613 nm. For each standard concentration (c), the zinc signal intensity / .Zn is plotted on a graph / .Zn = f(c), which corresponds to the calibration line (of type y = ax + b). The sample solution (diluted solution) of unknown concentration is then measured under the same conditions as the standards. The measured intensity is related to the concentration using the calibration line obtained previously. The concentration [c]ash in % by mass is thus obtained directly by the software, because the test portion and the volume have been previously recorded. The zinc concentration in pyrolysis black [c]black in mass % is obtained by the following equation: [ L0063] J [c] J noi .r = [c] J ash, res *100*% ashes

[0064] The determination of the sulfur content in pyrolysis blacks is carried out by LECO furnace. LECO sulfur analyzers are designed to measure, in particular, the sulfur content in organic and / or inorganic materials by combustion and non-dispersive infrared detection. Before measuring the sulfur content on the sample, the boats are cleaned and the furnace calibrated. The boats for LECO furnaces are previously cleaned: this involves analyzing the empty boat, under the same conditions as the samples. The preparation of the calibration curve is done from a commercial standard called "BBOT" whose purity is greater than 99.99% and whose carbon (C), hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S) content is guaranteed. This content is as follows: C%: 72.52; H% 6.09; N% 6.51; 0% 7.43 and S% 7.44. Approximately 10 ± 3, 20 ± 3 and 40 ± 3 mg of BBOT are weighed exactly in a pod.The standard / boat assembly is introduced into the combustion furnace, regulated at 1350 °C under pure oxygen. The combination of the furnace temperature and the analysis flow rate causes the sample to combust and release sulfur and / or carbon in the form of SO2(g). After a time of 20 s, oxygen begins to flow through the "lance" to accelerate the combustion of difficult-to-burn materials. Sulfur and / or carbon, in the form of. S02(g), are carried by an oxygen flow through the infrared detection cells. The instrument software plots a straight line connecting the mass of the standard introduced and the observed response (area) on the detector. This produces a calibration line. After carefully cleaning the sampling equipment, approximately 80 + 5 mg of pyrolysis black are weighed exactly and introduced into a LECO furnace boat. The area of ​​the observed SO2 peak is related to the concentration using the calibration line. The instrument software then calculates the mass % of sulfur in the sample using the mass of the sample introduced into the boat.

[0065] Preferably, the rubber composition according to the invention also comprises a carbon black which is not a pyrolysis carbon black within the meaning of the present invention, called ASTM grade carbon black, as defined according to standard ASTM D1765-96.

[0066] The rubber composition according to the invention may also comprise a reinforcing inorganic filler, preferably silica.

[0067] Suitable ASTM grade carbon blacks are all carbon blacks, in particular HAL, ISAE, SAE type blacks conventionally used in pneumatic tires (so-called pneumatic grade blacks). Among the latter, mention may be made more particularly of reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N660, N683, N772). The carbon blacks could, for example, already be incorporated into an isoprene elastomer in the form of a masterbatch (see for example applications WO 97 / 36724 or WO 99 / 16600). The BET specific surface area of ​​carbon blacks is measured according to standard D6556-10 [multi-point method (minimum 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3].

[0068] By "reinforcing inorganic filler" is meant in the present application, by definition, any inorganic or mineral filler (whatever its color and its natural or synthetic origin), also called "white" filler, "light" filler or even "non-black filler" as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tires, in other words capable of replacing, in its reinforcing function, a conventional tire-grade carbon black; such a filler is generally characterized, in a known manner, by the presence of hydroxyl groups (-OH) on its surface.

[0069] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, in particular silica (SiO2), or of the aluminous type, in particular alumina (A12O3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica or of biosourced origin presenting a BET surface area as well as a CT AB specific surface area both less than 450 m 2 / g, preferably 30 to 400 m 2 / g. Examples of highly dispersible precipitated silicas (known as "HDS") include "Ultrasil 7000" and "Ultrasil 7005" silicas from Degussa, "Zeosil 1165MP", "1135MP" and "1115MP" silicas from Rhodia, "Hi-Sil EZ150G" silica from PPG, "Zeopol 8715", "8745" and "8755" silicas from Huber, and high specific surface silicas as described in application WO 03 / 16837.

[0070] The BET specific surface area of ​​silica is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" Vol. 60, page 309, February 1938, more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure range p / po: 0.05 to 0.17). The CT AB specific surface area of ​​silica is determined according to the French standard NF T 45-007 of November 1987 (method B).

[0071] Also suitable as reinforcing inorganic fillers are mineral fillers of the aluminous type, in particular alumina (A12O3) or aluminum (oxide)hydroxides, or reinforcing titanium oxides, for example described in US 6,610,261 and US 6,747,087.

[0072] The physical state in which the reinforcing inorganic filler is present is irrelevant, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers.

[0073] A person skilled in the art will understand that, as a filler equivalent to the reinforcing inorganic filler described in this paragraph, a reinforcing filler of another nature, in particular organic, could be used, provided that this reinforcing filler is covered with an inorganic layer such as silica, or else comprises functional sites on its surface, in particular hydroxyl sites, making it possible to establish the bond between the filler and the elastomer in the presence or absence of a covering or coupling agent.

[0074] 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, 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 may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0075] Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TES PD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0076] The coupling agent content is preferably less than 12 phr, it being understood that it is generally desirable to use as little as possible. Typically when a reinforcing inorganic filler is present, the coupling agent content represents from 0.5% to 15% by weight relative to the amount of inorganic filler. Its content is preferably within a range of 0.5 to 15 phr. This content is easily adjusted by a person skilled in the art according to the content of inorganic filler used in the rubber composition.

[0077] The rate of reinforcing filler, the reinforcing filler preferably comprising mainly, or even exclusively, pyrolysis carbon black, is preferably within a range from 20 to 200 phr, preferably from 30 to 150 phr, preferably from 40 to 100 phr, preferably from 50 to 80 phr. Crosslinking system

[0078] The crosslinking system may be any type of system known to those skilled in the art in the field of rubber compositions for tires. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0079] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in especially diphenylguanidine), or even known vulcanization retardants.

[0080] Sulphur is used at a preferential rate of between 0.5 and 12 pce, in particular between 1 and 10 pce. The vulcanisation accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 8.0 pce.

[0081] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds. Various additives

[0082] The rubber compositions in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions for pneumatic tires, such as, for example, plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents.

[0083] Preferably, the rubber composition according to the invention does not comprise nitrile compounds or comprises less than 10 phr, preferably less than 5 phr, preferably less than 2 phr, very preferably less than 1 phr and even more preferably less than 0.5 phr.

[0084] The rubber composition can be either in the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization).

[0085] Finished or semi-finished rubber article and pneumatic tire

[0086] The present invention also relates to a finished or semi-finished rubber article comprising a rubber composition according to the invention. Particularly preferred rubber articles are, for example, conveyor belts, straps, inflatable articles.

[0087] The present invention also relates to a pneumatic or non-pneumatic tire which comprises a rubber composition according to the invention. By non-pneumatic tire is meant a tire capable of supporting the load of a vehicle by a means other than a pressurized gas, for example by means of stays.

[0088] It is possible to define three types of zones within the bandage: • The radially outer zone in contact with the ambient air, comprising the so-called outer layers, these layers essentially comprising the tread and the outer sidewall of the tire. An outer sidewall is an elastomeric layer arranged outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead so as to totally or partially cover the area of ​​the carcass reinforcement extending from the crown to the bead. • The radially inner zone in contact with the inflation gas or other means of holding the load, this zone generally consisting, in the case of pneumatic tires, of the layer impervious to the inflation gases, sometimes called the inner waterproof layer or inner rubber (“inner liner” in English). • The inner zone of the bandage, i.e. the zone between the outer and inner zones. This zone includes layers or plies which are herein referred to as inner layers of the bandage. These are, for example, carcass plies, tread sub-layers, bandage belt plies or any other layer which is not in contact with the ambient air or the inflation gas of the bandage or any other load-bearing means.

[0089] The rubber composition defined in the present description is particularly well suited to the internal and external layers of the bandages, and in particular, for the external layers, to the tread compositions and, for the internal layers, to the layers of the so-called "low" zone, at the level of the bead of the bandage such as for example the bead fillers, the crown feet and the combinations of these internal layers.

[0090] The rubber composition according to the invention may also be suitable for the inner and outer layers of non-pneumatic tires, in particular for the treads of non-pneumatic tires and the lower areas of these non-pneumatic tires.

[0091] The invention particularly relates to tires intended to equip motor vehicles of the passenger car, SUV ("Sport Utility Vehicles"), or two-wheeled type (in particular motorcycles), or airplanes, or even industrial vehicles chosen from vans, "Heavy Goods Vehicles", i.e. metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles, and others.

[0092] The invention relates to articles comprising a rubber composition according to the invention, both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization). Preparation of rubber compositions

[0093] The rubber composition according to the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: - a first working phase or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents, in particular the elastomeric matrix, the fillers, any other various additives, with the exception of the crosslinking system, are introduced into a suitable mixer such as a conventional internal mixer (for example of the 'Banbury' type). The incorporation of the filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system.

[0094] The non-productive phase is carried out at high temperature, up to a maximum temperature between 110°C and 190°C, preferably between 130°C and 180°C, for a duration generally between 2 and 10 minutes. - a second phase of mechanical work (so-called “productive” phase), which is carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 110°C, for example between 40°C and 100°C. The crosslinking system is then added, and everything is then mixed for a few minutes, for example between 2 and 15 min.

[0095] The process for preparing such rubber compositions comprises, for example, the following steps: a. incorporating into a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, by thermomechanically kneading the whole (for example in one or more times), until a maximum temperature of between 110°C and 190°C is reached; b. cooling the whole to a temperature below 100°C; c. then incorporating, during a second step (called "productive"), a crosslinking system; d. kneading the whole to a maximum temperature below 110°C.

[0096] Between 1 and 30 pce of epoxy resin and between 0.5 and 15 pce of a hardener can be introduced, independently of each other, either during the non-productive phase (a) or during the productive phase (c). Preferably, the epoxy resin is introduced during the non-productive phase (a) while the hardener is introduced during the productive phase (c).

[0097] The final rubber composition thus obtained can then be calendered, for example in the form of a sheet, a plate in particular for characterization in the laboratory, or even extruded in the form of a semi-finished (or profile) rubber used for the manufacture of a pneumatic tire.

[0098] The crosslinking of the rubber composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure. Examples Measurement methods

[0099] Mooney Plasticity

[0100] An oscillating consistometer is used as described in the French standard NF T 43-005 (1991). The Mooney plasticity measurement is carried out according to the following principle: the rubber composition in its raw state (ze, before curing) is molded in a cylindrical enclosure heated to 100°C. After one minute of preheating, the rotor rotates within the test piece at 2 revolutions / minute and the torque used to maintain this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU=0.83 Newton.meters).

[0101] It is recalled that, as is well known to those skilled in the art, the lower the Mooney plasticity, the easier the material is to work. Of course, below a certain value (for example 20 UM), the material becomes too liquid to be usable, particularly for manufacturing internal layers.

[0102] Tensile tests

[0103] The tests were carried out in accordance with French standard NF T 46-002 of September 1988. All traction measurements were carried out at a temperature representative of the operating temperature of the rubber compound in the tire (100±2°C) and under normal hygrometry conditions (50+5% relative humidity), according to French standard NF T 40-101 (December 1979).

[0104] The nominal secant modulus calculated by reducing it to the initial section of the specimen (or apparent stress, in MPa) at 10% and 50% elongation noted respectively MA10 and MA50, was measured in second elongation (i.e. after accommodation) on samples cooked for 60 minutes at 150°C. Preparation of the compositions

[0105] The following tests are carried out as follows: we introduce into a internal mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 60°C, successively, the diene elastomer, the reinforcing filler, between 1 and 30 pce of the epoxy resin, as well as the various other ingredients with the exception of the crosslinking system. A thermomechanical work (non-productive phase) is then carried out in one step, which lasts a total of approximately 3 to 4 min, until a maximum "drop" temperature of 165°C is reached.

[0106] The mixture thus obtained is recovered, cooled and then sulfur, a sulfenamide type accelerator and the hardener are incorporated, on a mixer (homo-finisher) at 30°C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

[0107] The rubber compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or extruded in the form of a profile.

[0108] The crosslinking of the rubber composition is carried out at a temperature of 150°C, for 60 min, under pressure.

[0109] [Tableauxl] 1. Natural rubber; 2. Carbon black of grade ASTM N326 (denomination according to ASTM D-1765 standard); 3. “P550” from Scandinavian Enviro Systems, carbon black pyrolysis with a sulfur content of between 2% and 3% by weight relative to the total weight of the pyrolysis black measured according to the method of the description, and the ash content is at most 20% by weight relative to the total weight of the pyrolysis black, measured according to the method of the description 4. Novolac formophenolic resin (“Peracit 4536K” from Perstorp); 5. Epoxy resin (“EPN 1138” from Huntsman); 6. Hexamethylenetetramine (from Degussa); 7. Urea from Univar Solution 8. Zinc oxide (industrial grade - Umicore company); 9. Stearin (“Pristerene 4931” from Uniqema company); 10. Nl,3-dimethylbutyl-N-phenylparaphenylenediamine (“Santoflex 6-PPD” from Flexsys); 11. N-cyclohexyl-benzothiazyl sulphenamide (“Santocure CBS” from Flexsys).

[0110] Replacing ASTM carbon black (composition Cl) with pyrolysis carbon black (composition C.4), adjusting the contents so that the medium strain stiffness (MA50) is maintained, improves the hysteretic loss properties. On the other hand, the raw viscosity is significantly increased, which makes the shaping, and therefore the processability, of this C.4 rubber composition more difficult.

[0111] Replacing a formophenolic resin (composition Cl) with an epoxy resin (composition C.2) with medium deformation rigidity maintained allows a lower raw viscosity to be obtained. On the other hand, the hysteretic loss properties once the rubber composition C.2 is crosslinked are significantly increased.

[0112] The combination according to the invention of an epoxy resin and a pyrolysis carbon black (composition C.3) makes it possible to obtain a rubber composition which has both good processability and interesting performances once crosslinked, with rigidity at average deformations maintained and hysteretic losses similar to those of the control rubber composition C1.

[0113] [T ables 2]

[0114] The constituent references are identical to those in Table 1.

[0115] It is observed in these examples that the combination of a pyrolysis black and an epoxy resin presents a better evolution of rigidity than the combination of a pyrolysis black and a formophenolic resin.

Claims

Claims

1. Rubber composition based on at least: - a diene elastomer; - a reinforcing filler comprising pyrolysis carbon black; - a crosslinking system; - between 1 and 30 pce of an epoxy resin; - between 0.5 and 15 pce of a hardener.

2. A rubber composition according to claim 1 wherein the reinforcing filler also comprises a carbon black other than a pyrolysis carbon black.

3. A rubber composition according to any preceding claim wherein the reinforcing filler also comprises a reinforcing inorganic filler, preferably silica.

4. A rubber composition according to any preceding claim wherein the reinforcing filler comprises predominantly pyrolysis carbon black.

5. A rubber composition according to claim 1 wherein the reinforcing filler consists of pyrolysis carbon black.

6. A rubber composition according to any preceding claim wherein the pyrolysis carbon black has an ash content in a range of 5 to 30% by weight relative to the total weight of pyrolysis carbon black.

7. A rubber composition according to any one of the preceding claims wherein the pyrolysis carbon black usable in the context of the present invention has a sulfur content greater than 2% by weight, preferably ranging from 2.5 to 5% by weight, relative to the total weight of the pyrolysis carbon black.

8. Rubber composition according to any one of the preceding claims in which the diene elastomer is chosen from highly unsaturated diene elastomers, preferably is a diene elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers, preferably chosen from natural rubber and polyisoprene, and preferably is natural rubber.

9. A rubber composition according to any preceding claim wherein the epoxy resin is selected from the group consisting of 2,2 bis[4-(glycidyloxy)phenyl]propane, poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane and mixtures of these resins.

10. Rubber composition according to the preceding claim in which the epoxy resin is selected from the group consisting of resins of the poly[(o-cresylglycidyl ether)-co-formaldehyde], poly[(o-phenylglycidyl ether)-co-formaldehyde], tri(glycidoxyphenyl)methane, tetra(glycidoxyphenyl)ethane type and mixtures of these resins.

11. A rubber composition according to any preceding claim wherein the resin content in the composition is between 10 and 28 phr.

12. A rubber composition according to any one of the preceding claims wherein the hardener is a hardener selected from aromatic diamines, aliphatic diamines, anhydrides, and ureas, preferably selected from aromatic diamines and ureas.

13. Rubber composition according to the preceding claim in which the hardener is a urea hardener chosen from the compounds carbamide, N,N'-dimethylurea, ethyleneurea, N-phenylurea, 1,3-diphenylurea, 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea), preferably chosen from the compounds urea, N,N'-dimethylurea, N-phenylurea, 1,3-diphenylurea, 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea) and very preferably chosen from the compounds carbamide and N,N'-dimethylurea and 1,1'-(4 methyl-m-phenylene) bis(3,3-dimethyl urea) and very preferably is carbamide, also called urea, of formula H2N-CO-NH2.

14. Finished or semi-finished rubber article comprising a rubber composition according to any one of the preceding claims preferably selected from conveyor belts, straps and inflatable articles.

15. A pneumatic or non-pneumatic tire which comprises a corn rubber position according to any one of claims 1 to 10.

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