Rubber composition comprising a hydrocarbon wax based on a cut derived from pyrolysis

Abstract

The invention relates to a rubber composition based on at least one elastomer matrix, a reinforcing filler, a crosslinking system and a hydrocarbon wax based on a cut derived from the pyrolysis of a feedstock comprising predominantly polyethylene, said cut comprising at most 5 wt.-% compounds containing at most 24 carbon atoms and at most 5 wt.-% compounds containing at least 38 carbon atoms.

Description

[0001] Rubber composition comprising a hydrocarbon wax based on a cut resulting from pyrolysis

[0002] Technical field of the invention

[0003] The present invention relates to the field of rubber compositions, in particular rubber compositions for pneumatic tires.

[0004] Prior art

[0005] Tires, and more generally rubber products such as conveyor belts and non-pneumatic tires, are complex objects made up of a multitude of components. For example, a tire is made up of more than 200 different raw materials.

[0006] While some raw materials, such as natural rubber, are derived from renewable resources, many tire components are still derived from fossil resources. It is therefore crucial to seek to minimize the use of these resources by biosourcing or recycling used materials.

[0007] However, the recycling of materials, for example from used rubber or plastic articles, is still limited, particularly due to the major impact of the constituents on the performance of the tire. Indeed, the recycling of materials can have a negative overall environmental impact due to the degradation of the performance of tires using these materials.

[0008] Much research has been conducted in the field of product recycling for use in tires, particularly on the recovery of oils from the pyrolysis of tire waste. For example, documents EP 0928817, WO 2013 / 170358 and JP2017 / 008214 teach the production of tire-grade carbon black from the pyrolysis of tire chips. Other research focuses on the recovery of intermediate products. Document WO 90 / 14409 focuses on the separation of tire waste pyrolysis oils by distillation in order to recover valuable chemical compounds, in particular limonene.

[0009] Document CA 3 032 242 describes the catalytic depolymerization of plastics for the manufacture of monomers and waxes. However, the use of the effluents produced is not addressed. Continuing its research, the applicant discovered that a rubber composition comprising a hydrocarbon wax resulting from the pyrolysis of a feedstock comprising mainly polyethylene exhibits improved fatigue resistance performance while preserving the other characteristics.

[0010] Definitions

[0011] 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.

[0012] A Cn compound means a compound containing n carbon atoms. Similarly, a Cn'Cm compound means a set of compounds containing n to m carbon atoms.

[0013] A heteroatom is an atom other than carbon or hydrogen, for example nitrogen, sulfur, oxygen.

[0014] By majority is meant, in a known manner, representing at least 50% by weight.

[0015] Detailed description of the invention

[0016] The invention relates to a rubber composition based on at least one elastomeric matrix, a reinforcing filler, a crosslinking system and a hydrocarbon wax based on a cut resulting from the pyrolysis of a filler mainly comprising polyethylene, said cut comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms.

[0017] Rubber composition Elastomer

[0018] The rubber composition according to the invention comprises at least one elastomer, preferably diene. By diene type elastomer, it is recalled that should 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). These diene elastomers can be classified into two categories :"essentially unsaturated" or "essentially saturated". "Essentially unsaturated" is generally understood to mean 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 may 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.

[0019] The term “diene elastomer” which may be used in the rubber compositions in accordance with the invention is understood in particular 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.

[0020] The other monomer can be ethylene, an olefin or a diene, conjugated or not.

[0021] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3'-dienes, such as 1,3'-butadiene and isoprene.

[0022] Suitable olefins are vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic chromoolefins with 3 to 12 carbon atoms.

[0023] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, methyl-, para-methylstyrene, the commercial mixture "vinyltoluene", para-tert-butylstyrene.

[0024] Suitable aliphatic chromoolefins are, in particular, acyclic aliphatic chromoolefins having from 3 to 18 carbon atoms.

[0025] The diene elastomer is preferably a diene elastomer of the highly unsaturated type, in particular a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), polybutadienes (BR), butadiene copolymers, isoprene copolymers and mixtures 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 mixtures of such copolymers.

[0026] 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.

[0027] 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.

[0028] Preferably, the composition according to the invention comprises at least 50 pce of at least one butadiene elastomer, preferably chosen from the group consisting of polybutadienes, butadiene copolymers and their mixtures, preferably chosen from the group consisting of polybutadienes, butadiene-styrene copolymers and their mixtures.

[0029] According to a preferred embodiment of the invention, the butadiene elastomer is a butadiene copolymer having a glass transition temperature Tg of less than -20°C, preferably between -20°C and -110°C, more preferably between -60°C and -110°C, more preferably between -60°C and -90°C. Such elastomers are known to those skilled in the art and described for example in documents WO2015 / 185394 and WO2017 / 168099.

[0030] Preferably and according to this embodiment, the composition according to the invention comprises at least 70 pce, preferably at least 90 pce, of at least one butadiene copolymer, preferably a butadiene-styrene copolymer.

[0031] Preferably, according to any one of the embodiments of the invention, the composition according to the invention further comprises at least 20 pce of an isoprene elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes and their mixtures. Reinforcing filler

[0032] The rubber composition according to the invention comprises a reinforcing filler. Any type of reinforcing filler known for its ability to reinforce an elastomeric composition suitable for the manufacture of pneumatic tires may be used, for example an organic filler such as carbon black, a reinforcing inorganic filler such as silica, or a blend of these two types of filler, in particular a blend of carbon black and silica.

[0033] Suitable carbon blacks are all carbon blacks, in particular HAF, ISAF, SAF type blacks conventionally used in tires (so-called tire grade blacks). Among the latter, mention will 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 even, 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 / PO ■ 0.1 to 0.3].

[0034] 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 pneumatic grade carbon black. Such a filler is generally characterized, in a known manner, by the presence of hydroxyl groups (-OH) on its surface.

[0035] Suitable inorganic reinforcing fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiOa) or of the aluminous type, in particular alumina (AlaOs).

[0036] The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica. The precipitated silica may be produced from raw materials derived from inorganic sand (silicon dioxide from inorganic sand), recycled materials such as foundry sands, end-of-life tires and in particular end-of-life tire treads comprising mainly silica as a reinforcing filler or from bio-sourced raw materials such as organic waste from plants, preferably inedible organic waste from plants.

[0037] Plants with silicon dioxide in their tissues include mustard, especially mustard husks, grasses, and especially among grasses bamboo leaves, corn cobs, sugarcane bagasse, rice, wheat, especially rice husks, and wheat husks.

[0038] Silica derived from non-renewable raw materials such as natural inorganic sand is usually obtained by heating sand in a glass furnace in the presence of sodium carbonate. The resulting sodium silicate is then solubilized in water, possibly in the presence of a base such as, for example, sodium hydroxide. A synthetic precipitated silica is formed from this aqueous solution by controlled treatment of the silicate with an acid (for example, a mineral acid and / or an acidifying gas such as, for example, carbon dioxide). Sometimes, an electrolyte (for example, sodium sulfate) may be present to promote the formation of precipitated silica particles. The recovered precipitated silica is an amorphous precipitated silica.

[0039] Silica derived from bio-based raw materials such as those mentioned above may for example be obtained by burning the bio-based raw material so as to recover the ash of this bio-based material which mainly contains silicon dioxide. For example for rice husks, and in a process equivalent to that above for silicas based on mineral or recycled raw materials, the rice husk ash is generally treated with a strong base such as, for example, sodium hydroxide, to form an aqueous silicate solution (for example, sodium silicate), after which a precipitated synthetic silica is formed by controlled addition of an acid (for example, a mineral acid and / or an acidifying gas such as, for example, carbon dioxide) in which an electrolyte (for example, sodium sulfate) may be present to promote the formation of precipitated silica particles derived from rice husks.The recovered precipitated silica is an amorphous precipitated silica. As is known, silica from rice husk ash is called RHA silica (Rice Husk Ash Silica). Bio-sourced silicas are available, for example, from suppliers such as Solvay, Evonik, Quechen, Wilmar International, Wuxi, etc. In summary, the synthesis of a precipitated silica that can be used in the context of the invention can be carried out from a sodium silicate obtained entirely from bio-sourced, recycled, or non-renewable raw materials, but also from a mixture of bio-sourced and / or recycled and / or non-renewable raw materials (such as commonly used sands).

[0040] Preferably, the precipitated silica, whether obtained from mineral, recycled or bio-sourced raw materials, has a BET specific surface area as well as a CTAB specific surface area, both less than 450 m 2 / g, preferably within a range of 30 to 400 m 2 / g, especially from 60 to 300 m 2 / g.

[0041] Any type of precipitated silica can be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art.

[0042] Examples include the silicas described in applications WG03 / 016215-A1 and W003 / 016387-A1. Commercial HDS silicas include the silicas “Ultrasil ® 5000GR”, “Ultrasil ® 7000GR” from Evonik, and the silicas “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from Solvay. As non-HDS silica, the following commercial silicas can be used: ■ “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” silicas from Evonik, “Zeosil® 175GR” silicas from Solvay, “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” silicas from PPG, “K160”, “K185”, “K195” silicas from Wilmar International.

[0043] 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.

[0044] The reinforcing inorganic filler used, in particular if it is silica, preferably has a BET surface area of ​​between 45 and 400 m2 / g, more preferably between 60 and 300 m2 / g. Preferably, the reinforcing filler of the rubber composition according to the invention comprises from 10 to 150 phr, preferably from 50 to 130 phr of silica. In a preferred arrangement, the reinforcing filler mainly comprises silica and preferably consists of silica.

[0045] To couple the reinforcing inorganic filler to the elastomer, it is optionally possible to use in a known manner an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the elastomer, in particular organosilanes, or bifunctional polyorganosiloxanes.

[0046] In particular, polysulfurized silanes, called "symmetrical" or "asymmetrical" depending on their particular structure, may be used, as described for example in applications W003 / 002648 (or US 2005 / 016651) and W003 / 002649 (or US 2005 / 016650).

[0047] Examples of polysulfurized silanes include polysulfides (particularly disulfides, trisulfides or tetrasulfides) of bis-(alkoxyl(Cl-C4)-alkyl(Cl _ C4)silyl-alkyl(Cl _ C4)), such as bis(3) polysulfides _trimethoxysilylpropyl) or bis(3 _ triethoxysilylpropyl). Among these compounds, bis(3) tetrasulfide is used in particular _ triethoxysilylpropyl), abbreviated TESPT, of formula [(C2H5O)3Si(CH2)3S2]2 or bis-(triethoxysilylpropyl) disulfide, abbreviated TESPD, of formula [(C2H5O)3Si(CH2)3S]2. Also mentioned as preferred examples are polysulfides (in particular disulfides, trisulfides or tetrasulfides) of bis-(monoalkoxyl(Cl-C4)-dialkyl(Cl _ C4)silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide as described in patent application US 2004 / 132880.

[0048] As coupling agent other than polysulfurized alkoxysilane, mention will be made in particular of bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides as described in patent applications WO 02 / 30939 and WO 02 / 31041, or silanes or POS bearing azodicarbonyl functional groups, as described for example in patent applications WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534.

[0049] In the rubber compositions in accordance with the invention, the content of coupling agent is preferably in a range from 5 to 18% by weight relative to the quantity of silica, preferably in a range from 8 to 12% by weight relative to the quantity of silica. Those 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 on its surface functional sites, 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.

[0050] In a preferred arrangement in which the rubber composition according to the invention comprises an isoprene elastomer, the rubber composition preferably comprises at least 25 phr of carbon black.

[0051] Crosslinking system

[0052] The rubber composition according to the invention preferably comprises a sulfur-based crosslinking system comprising a metal oxide, a stearic acid derivative and a vulcanization accelerator. This is then 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.

[0053] Sulphur is preferably used at a rate ranging from 1 to 20 pce, preferably from 1 to 10 pce.

[0054] 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"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0055] The crosslinking system may also optionally include a vulcanization retarder. Hydrocarbon wax

[0056] The rubber composition according to the invention comprises a hydrocarbon wax based on a cut resulting from the pyrolysis of a filler mainly comprising polyethylene, said cut comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms.

[0057] Hydrocarbon wax means a wax that consists only of carbon and hydrogen atoms.

[0058] Such properties enable the rubber composition according to the invention to achieve the desired performance.

[0059] The said hydrocarbon wax is based on a cut resulting from the pyrolysis of a charge mainly comprising polyethylene. The method of obtaining the wax gives it rubber composition properties different from similar waxes in terms of structure.

[0060] Preferably, the charge comprising mainly polyethylene which is pyrolyzed comprises at least 60% by weight of polyethylene, preferably at least 70% by weight of polyethylene, preferably at least 80% by weight of polyethylene, preferentially at least 90% by weight of polyethylene and very preferably consists of polyethylene.

[0061] Preferably, the hydrocarbon wax has alkenic functions at the end of the chain.

[0062] The hydrocarbon wax used in the invention is capable of being obtained by a process comprising at least ■ a) A step of pyrolysis of the feedstock comprising mainly polyethylene making it possible to obtain at least one pyrolysis effluent b) A step of separation of the pyrolysis effluent into an intermediate effluent comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms, at least one effluent of light compounds and at least one effluent of heavy compounds.

[0063] Such a process may, for example, correspond to the process described in document CA 3 032 242. Step a) of pyrolysis

[0064] The feedstock, mainly comprising polyethylene, feeds a pyrolysis stage preferably carried out at a temperature between 300 and 600°C, making it possible to obtain a pyrolysis oil.

[0065] Pyrolysis means the thermal decomposition of compounds in an inert or oxygen-deficient atmosphere, i.e. comprising less than 5% by volume, preferably less than 3% by volume and more preferably less than 2% by volume of oxygen, preferably in an inert atmosphere.

[0066] The pyrolysis step is preferably carried out at a pressure of less than 1 bar under an inert atmosphere, for example under a nitrogen atmosphere.

[0067] The pyrolysis step can be carried out in a pyrolysis reactor, and can be operated continuously, semi-continuously or in batch processing. Such reactors are well known to those skilled in the art.

[0068] Preferably, the pyrolysis step of the process for obtaining the hydrocarbon wax comprises pyrolysis by microwave thermal assistance. The thermal power required for the pyrolysis is, in this case, provided by microwave radiation.

[0069] Preferably in this configuration, the power delivered by the microwave device of the microwave thermal assistance pyrolysis is between 0.1 and 10 kW / kg load, preferably between 0.1 and 5 kW / kg load, preferably between 0.5 and 4 kW / kg load and preferably between 1 and 4 kW / kg load.

[0070] When the pyrolysis step is operated continuously or semi-continuously, it can be implemented in several zones.

[0071] Step b) separation of pyrolysis oil

[0072] The pyrolysis oil is then treated in a separation step so as to obtain a wax comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms.

[0073] Any separation known to those skilled in the art can be implemented. Since pyrolysis oil is a hydrocarbon effluent, such a separation is well known to those skilled in the art and does not present any difficulty. For example, the pyrolysis oil is treated in a first separation step, called topping, to separate the lightest fraction comprising the compounds having at most 16 carbon atoms. Such a separation step can be implemented by any means known to those skilled in the art, for example by evaporation in a distillation column, in an evaporator such as a wiped film evaporator, or by any other means.

[0074] The effluent comprising the heavier compounds is treated in a second separation stage so as to separate the fraction comprising the compounds having 16 to 28 carbon atoms.

[0075] Finally, the residual fraction is treated in a final separation step, called tailing, in order to separate the fraction comprising compounds having more than 36 carbon atoms.

[0076] Other additives

[0077] The rubber composition according to the invention may preferably comprise additives commonly used in elastomeric compositions particularly intended for the manufacture of vehicle tires, such as, for example, pigments, protective agents, such as antiozonant waxes, antiozonants or chemical antioxidants, plasticizing agents other than those described above, antifatigue agents, reinforcing resins, or acceptors (for example, a phenolic novolak resin) or donors (for example HMT or H3M) of methylene.

[0078] In a preferred arrangement, the rubber composition according to the invention may comprise from 20 to 100 phr of plasticizing hydrocarbon resin.

[0079] The term "resin" is reserved in the present application, by definition, for a compound which is solid at room temperature (20°C), as opposed in particular to a liquid plasticizing agent such as an oil.

[0080] Hydrocarbon resins are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, usable in particular as plasticizing agents or tackifying agents in polymer matrices. They are by nature miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluting agents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted to their applications, in particular in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods"). They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, of the aliphatic / aromatic type, i.e. based on aliphatic and / or aromatic monomers.They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Their Tg is preferably greater than 30°C, particularly between 30°C and 95°C.

[0081] Examples of such hydrocarbon resins include those selected from the group consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), dicyclopentadiene homopolymer or copolymer resins (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins, alpha-methyl-styrene homopolymer or copolymer resins and mixtures of these resins.Among the above copolymer resins, mention may be made more particularly of those chosen from the group consisting of (D)CPD / vinylaromatic copolymer resins, (D)CPD / terpene copolymer resins, terpene phenol copolymer resins, (D)CPD / C5 cut copolymer resins, (D)CPD / C9 cut copolymer resins, terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C5 cut / vinylaromatic copolymer resins, and mixtures of these resins.

[0082] The term "terpene" here includes the monomers alpha-pinene, beta-pinene and limonene, preferentially a limonene monomer is used, a compound which is present in the form of three possible isomers, in a known manner: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, racemic of the dextrorotatory and levorotatory enantiomers. Suitable vinylaromatic monomers are, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer derived from a C9 cut (or more generally from a Cs to Cio cut).

[0083] More particularly, mention may be made of resins chosen from the group consisting of (D)CPD homopolymer resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 / styrene cut copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins.

[0084] C5 resins are commercially available, for example sold by Eastman under the name "Piccotac 1105" or "Impera R1507", by Exxon under the name "Escorez 1102", by Kolon under the name "Hikorez Al 100" or by Cray Valley Total under the name "Wingtack98". C5-C9 resins are commercially available, for example sold by Exxon under the name "OPPERA373", by Eastman under the name "Piccotac 8090", by Cray Valley Total under the name "Wingtack STS".

[0085] Preparation of rubber compositions

[0086] The rubber composition in accordance with the invention is manufactured in suitable mixers, using preparation phases well known to those skilled in the art ■ a thermomechanical working or mixing phase, which can be carried out in a single thermomechanical step during which all the necessary constituents, in particular the elastomeric matrix, the hydrocarbon resin, the fillers, and any other various additives, 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 thermomechanically mixing.In the case where the filler, in particular carbon black or silica, 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.

[0087] Thermomechanical mixing is carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes. A second phase of mechanical work is then carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system will be added during the second phase.

[0088] The final composition thus obtained can then be calendered, for example in the form of a sheet or plate, in particular for characterization in the laboratory, or even extruded in the form of a semi-finished (or profile) rubber.

[0089] The composition can be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), can be a semi-finished product which can be used in a tire.

[0090] The curing can be carried out, in a manner known to those skilled in the art, 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 curing temperature, the crosslinking system adopted, the crosslinking kinetics of the composition considered or even the size of the tire.

[0091] Vehicle bandage

[0092] The present invention also relates to vehicle tires comprising a rubber composition based on at least one elastomer and a hydrocarbon wax according to the invention.

[0093] The vehicle tire may be a pneumatic or non-pneumatic tire. Non-pneumatic means that the tire is capable of supporting the vehicle load by means other than pressurized inflation gas, for example by means of guy wires.

[0094] The vehicle tire according to the invention will be chosen from, without limitation, tires intended to equip a two-wheeled vehicle, a passenger vehicle, a “heavy load” vehicle (i.e., a subway, a bus, off-road vehicles, heavy load transport vehicles, such as trucks, tractors or trailers), an aircraft, construction equipment, a heavy agricultural vehicle or a handling vehicle.

[0095] A vehicle tire usually comprises a crown, two sidewalls, two beads, each sidewall connecting each bead to the crown. Each bead comprises at least one circumferential reinforcing element, generally in the form of a bead wire.

[0096] The vehicle tire also includes a carcass reinforcement anchored in each bead and extending into each sidewall and into the crown. The carcass reinforcement includes a carcass layer including a portion wrapped around each circumferential reinforcing element.

[0097] The crown comprises a tread intended to come into contact with a ground when the vehicle tire is rolling and a crown reinforcement arranged radially between the tread and the carcass reinforcement. The crown reinforcement comprises a working reinforcement comprising at least one working layer. The crown reinforcement also comprises a hoop reinforcement arranged radially outside the working reinforcement, the hoop reinforcement being delimited axially by two axial edges and comprising at least one hoop wire reinforcement element wound circumferentially helically so as to extend axially from one axial edge to the other axial edge of the hoop reinforcement in a main direction of the or each hoop wire reinforcement element.

[0098] Thus, the invention also relates to a vehicle tire provided with a sidewall, as described above, said sidewall comprising at least one rubber composition according to the invention.

[0099] The invention also relates to a vehicle tire, the tread of which comprises a rubber composition according to the invention.

[0100] Measurement methods

[0101] Mooney Plasticity

[0102] The Mooney plasticity measurement is carried out according to the following principle and in accordance with ASTM D-1646. The raw composition is molded in a cylindrical chamber heated to a given temperature, usually 100°C. After one minute of preheating, an L-type rotor rotates within the specimen at 2 revolutions per minute and the torque needed 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).

[0103] Tensile tests

[0104] The tests were carried out in accordance with French standard NF T 46-002 of September 1988. All tensile measurements were carried out under normal temperature (23±2°C) and hygrometry (50±5% relative humidity) conditions, according to French standard NF T 40-101 (December 1979). The nominal secant modulus calculated by reducing to the initial section of the specimen (or apparent stress, in MPa) at 100% and 300% elongation, respectively noted MAioo and MAsoo, was measured in second elongation (i.e. after accommodation) on samples baked for 25 minutes at 150°C.

[0105] The results are expressed in base 100, the value 100 being assigned to the control. A result greater than 100 indicates that the composition of the example considered has greater rigidity than the control.

[0106] The breaking stresses (in MPa) and the breaking strains (in %) were also measured, at 23°C ± 2°C, according to standard NF T 46-002, on raw samples or on samples cooked for 25 minutes at 150°C or 90 minutes at 160°C. The breaking energy is equal to the product of the breaking elongation and the breaking stress.

[0107] Dynamic properties

[0108] The dynamic properties G* and tan(d) are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of crosslinked composition (cylindrical specimen 4 mm thick and 400 mm 2section), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under defined temperature conditions, for example at 0°C, 23°C and 60°C according to ASTM D 1349-99. A strain amplitude sweep is carried out from 0.1 to 100% (forward cycle), then from 100% to 1% (return cycle). The results used are the complex dynamic shear modulus G* and the shear loss modulus G”, as well as the value of tan(d). For the return cycle, the value of G* and the value of G” at 10% strain are indicated, and the maximum value of tan(d) observed. The value of G” measured at 23°C is an indicator of rolling resistance. A low value denotes a lower contribution of the composition to rolling resistance.

[0109] Efflorescence test :

[0110] The efflorescence test measures the propensity of an anti-ozone wax to migrate excessively after a long storage period. The test procedure is as follows.

[0111] After cutting, plates in the form of 2.5 mm thick test pieces are oven-dried at 70°C for 12 hours in air. They are then oven-dried at 40°C in air for 4, 6 and 8 weeks.

[0112] After removal from the oven and return to room temperature for 15 min, a mechanical stimulus consisting of scraping the test piece with a metal blade is applied so as to reveal the efflorescence of the wax.

[0113] The extent of efflorescence (white discoloration on the surface) is then assessed using a subjective scale that is representative of the final appearance of the samples. The values ​​on this subjective scale range from 0 to 3 and correspond to the following aspects for the samples: ■ O-No efflorescence / 1-Slight efflorescence / 2-Moderate efflorescence / 3-Total efflorescence. The lower the value, the better the efflorescence performance.

[0114] Fatigue measurement

[0115] Fatigue resistance, expressed in number of cycles or in relative unit (ur), is measured in a known manner on 12 specimens subjected to repeated low-frequency tractions up to an elongation of 75%, at 23°C, using a Monsanto device (type “MFTR”) until the specimen breaks, according to standards ASTM D4482-85 and ISO 6943.

[0116] The result is expressed in relative units (ur). A value higher than that of the control, arbitrarily set at 100, indicates an improved result, i.e. better fatigue resistance of the rubber samples.

[0117] Resistance to ozone attack

[0118] The ozone resistance of materials is measured using the following method: ■ after baking and then steaming at 77°C in air for 14 days, 10 specimens are placed on a trapezoid at different elongations ranging from 10% to 100% in steps of 10% elongation along the major axis of the specimen (length of the specimen). The so-called B15 specimens are made from an MFTR plate (called Monsanto) whose two flanges at the ends are used to hold the specimen. The so-called B 15 specimens have the following dimensions: 78.5mm * 15mm * 1.5mm. After 3 and 8 days of exposure to a temperature of 38°C and an ozone level of 50pphm (parts per hundred million), each facies is visually analyzed via a photo using a binocular microscope.Each face is rated out of 20 based on its color: ■ all black = rating of 20 (intact specimen), rupture of the specimen = rating of 0, and between these two extreme ratings, the number and depth of cracks give gray levels to the specimen (measurement assisted by computer processing). This rating out of 20 takes into account all the specimens, with different deformations. The higher the rating, the better the ozone performance. Cooking time.

[0119] The times tO and t90 are determined from a cooking rheogram at 150 or 160°C according to DIN 53529. The alpha value is determined using the following calculation: ■ alpha(t)=(C(t)-Cmin) / (Cmax'Cmin) where C is a pair from the rheogram and t is a time. tO is the time such that alpha(t0)=0. t90 is the time such that alpha=0.90.

[0120] Examples

[0121] Example 1 - Synthesis of hydrocarbon wax

[0122] A pyrolysis step as described in document CA 3 032 242 is fed by a charge comprising 100% by weight of polyethylene (high density polyethylene, known as HDPE) in the form of granules whose largest dimension is between 3 and 5 mm. The microwave pyrolysis step is carried out under an inert nitrogen atmosphere with a power of the order of 600 W. Pyrolysis is stopped when the temperature of the gases at the pyrolysis outlet becomes lower than 50°C.

[0123] The pyrolysis effluent undergoes a first fractionation step in a scraped film evaporator in order to separate mainly the compounds comprising less than 16 carbon atoms. The raffinate comprising the heavier compounds is separated in a second scraped film evaporator in order to separate mainly the compounds comprising less than 28 carbon atoms. The raffinate from this second separation step is treated in a third separation step in a scraped film evaporator in order to separate the compounds comprising mainly more than 36 carbon atoms. The extract collected at the end of this last separation, constituting the hydrocarbon wax, comprises at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms.

[0124] The characteristics of the hydrocarbon wax obtained are presented in Table 1.

[0125] Example 2 - Rubber compositions

[0126] The rubber compositions detailed in Tables 2 and 3 are manufactured with the introduction of all the constituents on an internal mixer, with the exception of the vulcanization system. The vulcanizing agents (sulfur and accelerator) are introduced on an external mixer at low temperature (the rollers constituting the mixer being at 30 °C). The compositions are cured under pressure at 160 °C for compositions A-0, Al and A-2 and 150 °C for compositions A-3 and A-4. To produce these compositions, different waxes are used, the characteristics of which are indicated in the table below.

[0127] [Table 1] (1) C32 Redezon 500 anti-ozone wax from Repsol

[0128] (2) C36 Redezon 7236 anti-ozone wax from Repsol

[0129] Tables 2 and 3 show different rubber compositions using the waxes presented in Table 1 as well as the measurement results obtained.

[0130] The results are expressed in base 100, the value 100 being assigned to the control (A'0 for Table 2 and A- 3 for Table 3). A result greater than 100 indicates a value greater than the control value. [Table 2]

[0131] Table 2 References

[0132] (3) Natural rubber

[0133] (4) Polybutadiene Neodymium “Synteca 44” from Syntheos

[0134] (5) Cabot Company ASTM N660 Carbon Black (6) British Petroleum (BP) “Vivatec500” TDAE Oil

[0135] (7) Antioxidant “Vulkanox 4020” from Lanxess

[0136] (8) Antioxidant “Naugard Q” from Chemtura

[0137] (9) TertioButyl'Benzothiazyl-Sulfenamide (TBBS) “DelacS” from the company Chemtura. It is observed that the composition in accordance with the invention has properties equivalent to compositions comprising commercial waxes, both in its behavior during cooking and in its cooking properties, while having better resistance to fatigue.

[0138] [Table 3]

[0139] Table 3 References

[0140] (10) SBR copolymer of styrene and butadiene of Tg -65°C

[0141] (11) Cabot Company ASTM N234 Carbon Black

[0142] (12) Silica “Zeosilll65MP” from Solvay (13) Resin “OPPERA PR 383” from Exxon Mobil

[0143] (14) Oleic sunflower oil from CARGILL

[0144] (15) Silane “SI69” from the company EVONIK

[0145] (16) Diphenyl guanidine “DPG” from AKROCHEM

[0146] (17) Antioxidant “Santoflex 6PPD” from the company FLEXSYS

[0147] It is observed that the composition in accordance with the invention has properties equivalent to compositions comprising commercial waxes, both in its behavior during cooking and in its cooking properties, and has good breaking properties.

Claims

CLAIMS

1. Rubber composition based on at least one elastomeric matrix, a reinforcing filler, a crosslinking system and a hydrocarbon wax based on a cut resulting from the pyrolysis of a filler comprising mainly polyethylene, said cut comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms.

2. Composition according to the preceding claim in which the pyrolysis charge comprises at least 60% by weight of polyethylene, preferably at least 70% by weight of polyethylene, preferably at least 80% by weight of polyethylene, preferentially at least 90% by weight of polyethylene and very preferably consists of polyethylene.

3. Composition according to any one of the preceding claims in which the hydrocarbon wax has alkenic functions at the end of the chain.

4. Composition according to any one of the preceding claims in which the hydrocarbon wax is obtained by a process comprising at least ■ a) A step of pyrolysis of the feedstock comprising mainly polyethylene making it possible to obtain at least one pyrolysis effluent b) A step of separation of the pyrolysis effluent into an intermediate effluent comprising at most 5% by weight of compounds comprising at most 24 carbon atoms and at most 5% by weight of compounds comprising at least 38 carbon atoms, at least one effluent of light compounds and at least one effluent of heavy compounds.

5. Composition according to any one of the preceding claims in which the pyrolysis step of the process for obtaining the hydrocarbon wax comprises pyrolysis by microwave thermal assistance.

6. Composition according to any one of the preceding claims in which the reinforcing filler comprises from 10 to 150 phr, preferably from 50 to 130 phr of silica.

7. Composition according to any one of the preceding claims comprising from 20 to 100 pce of plasticizing hydrocarbon resin.

8. Composition according to any one of the preceding claims comprising at least 50 pce of a butadiene elastomer.

9. Composition according to the preceding claim in which the butadiene elastomer is a butadiene copolymer having a glass transition temperature Tg of less than -20°C, preferably between -20°C and -110°C.

10. Composition according to the preceding claim comprising at least 70 pce, preferably at least 90 pce of at least one butadiene copolymer, preferably a butadiene-styrene copolymer.

11. Composition according to any one of the preceding claims further comprising at least 20 phr of an isoprene elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes and their mixtures.

12. Composition according to the preceding claim comprising at least 25 pce of carbon black.

13. A vehicle tire comprising a rubber composition according to any preceding claim.

14. A vehicle tire having a tread comprising a rubber composition according to any one of claims 1 to 10.

15. A vehicle tire provided with an outer sidewall, said outer sidewall comprising at least one composition according to claim 11 or claim 12.

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