WO2021005719A1 - A rubber composition - Google Patents

A rubber composition Download PDF

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Publication number
WO2021005719A1
WO2021005719A1 PCT/JP2019/027176 JP2019027176W WO2021005719A1 WO 2021005719 A1 WO2021005719 A1 WO 2021005719A1 JP 2019027176 W JP2019027176 W JP 2019027176W WO 2021005719 A1 WO2021005719 A1 WO 2021005719A1
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WO
WIPO (PCT)
Prior art keywords
rubber composition
vulcanization accelerator
composition according
epoxy
phr
Prior art date
Application number
PCT/JP2019/027176
Other languages
French (fr)
Inventor
Tomoya Sakurada
Original Assignee
Compagnie Generale Des Etablissements Michelin
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Generale Des Etablissements Michelin filed Critical Compagnie Generale Des Etablissements Michelin
Priority to PCT/JP2019/027176 priority Critical patent/WO2021005719A1/en
Publication of WO2021005719A1 publication Critical patent/WO2021005719A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
    • B32B25/14—Layered products comprising a layer of natural or synthetic rubber comprising synthetic rubber copolymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
    • B32B25/04—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B25/042—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material of natural rubber or synthetic rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
    • B32B25/12—Layered products comprising a layer of natural or synthetic rubber comprising natural rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
    • B32B25/16—Layered products comprising a layer of natural or synthetic rubber comprising polydienes homopolymers or poly-halodienes homopolymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B60C1/0016—Compositions of the tread
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
    • C08L9/06—Copolymers with styrene

Definitions

  • the field of the invention is that of rubber compositions intended in particular for laminates, in more particular for articles, for example, tires, shoes, conveyors or caterpillar tracks, in still more particular for tires, in especial for treads of tires, in more especial for treads of tires capable of rolling over ground surface covered with snow.
  • the snow tires classified in a category of use “snow”, identified by an inscription the alpine symbol (“3-peak-mountain with snowflake”), marked on their sidewalls, mean tires whose tread patterns, tread compounds and/or structures are primarily designed to achieve, in snow conditions, a performance better than that of normal tires intended for normal on-road use with regard to their abilities to initiate, maintain or stop vehicle motion.
  • Snowy ground has a feature of having a low friction coefficient and a constant objective of manufacturers of rubber articles is improvement of a grip performance of rubber articles on snow-covered (snowy) ground without deteriorating the durability performance of rubber articles.
  • a specific rubber composition intended in particular for a laminate in more particular for a rubber article, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread, which allows an unexpectedly improved grip performance on snowy ground without deteriorating the durability performance.
  • elastomer matrix is understood to mean, in a given composition, all of the elastomers present in said rubber composition.
  • each Tg DSC glass transition temperature
  • DSC Densilic Acid
  • any interval of values denoted by the expression “between a and b” represents the range of values of more than “a” and of less than “b” (i.e. the limits a and b excluded) whereas any interval of values denoted by the expression “from a to b” means the range of values going from “a” to “b” (i.e. including the strict limits a and b).
  • composition comprising the mixture(s) and/or the product of the reaction of the various constituents used, some of the constituents being able or intended to react together, at least partly, during the various manufacturing phases of the composition, in particular during the vulcanization (curing).
  • a first aspect of the invention is a rubber composition based on at least an elastomer matrix, a reinforcing filler, an epoxy, and a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
  • the specific rubber compositions allows an unexpectedly improved the grip performance on snowy ground without deteriorating the durability performance.
  • the rubber composition according to the invention is based on an elastomer matrix.
  • Elastomer (or loosely “rubber”, the two terms being regarded as synonyms) of the “diene” type is to be understood in a known manner as an (meaning one or more) elastomer derived at least partly (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).
  • diene elastomers can be classified into two categories: “essentially unsaturated” or “essentially saturated”.
  • essentially unsaturated is understood to mean a diene elastomer resulting at least in part from conjugated diene monomers having a content of units of diene origin (conjugated dienes) which is greater than 15% (mol %); thus it is that diene elastomers such as butyl rubbers or diene/ ⁇ -olefin copolymers of the EPDM type do not fall under the preceding definition and may especially be described as “essentially saturated” diene elastomers (low or very low content of units of diene origin, always less than 15%).
  • the expression “highly unsaturated” diene elastomer is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
  • diene elastomer capable of being used in the compositions in accordance with the invention is understood in particular to mean: (a) - any homopolymer obtained by polymerization of a conjugated diene monomer, preferably having from 4 to 12 carbon atoms; (b) - any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with one or more vinyl aromatic compounds preferably having from 8 to 20 carbon atoms.
  • conjugated dienes 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C 1 -C 5 alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1 ,3-butadiene or 2-methyl-3-isopropyl-1 ,3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene or 2,4-hexadiene.
  • 1,3-butadiene 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C 1 -C 5 alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1 ,
  • vinylaromatic compounds styrene, ortho-, meta- or para-methylstyrene, the“vinyltoluene” commercial mixture, para-(tert-butyl) styrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene or vinylnaphthalene.
  • a second aspect of the invention is the rubber composition according to the first aspect, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and the combinations thereof.
  • the copolymers are preferably selected from the group consisting of butadiene copolymers the combinations thereof, more preferably selected from the group consisting of styrene-butadiene copolymers (SBR), butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and the combinations thereof, still more preferably selected from the group consisting of styrene-butadiene copolymers (SBR) and the combinations thereof.
  • SBR styrene-butadiene copolymers
  • BIR butadiene-isoprene copolymers
  • SIR styrene-isoprene copolymers
  • SBIR styrene-butadiene-isoprene copolymers
  • the diene elastomer may have any microstructure which depends on the polymerization conditions used, in particular on the presence or absence of a modifying and/or randomizing agent and on the amounts of modifying and/or randomizing agent employed.
  • This elastomer may, for example, be a block, statistical, sequential or micro sequential elastomer and may be prepared in dispersion or in solution.
  • This elastomer may be coupled and/or star-branched or else functionalized with a coupling and/or star-branching or functionalizing agent.
  • the elastomer matrix comprises more than 50 phr and up to 100 phr, preferably 55 to 95 phr, more preferably 60 to 90 phr, still more preferably 65 to 85 phr, particularly 70 to 80 phr, of a first diene elastomer which is a styrene butadiene copolymer(s), preferably a solution styrene butadiene copolymer(s), and the elastomer matrix comprises no second diene elastomer or comprises less than 50 phr, preferably 5 to 45 phr, more preferably 10 to 40 phr, still more preferably 15 to 35 phr, particularly 20 to 30 phr, of a second diene elastomer which is different from the first diene elastomer.
  • a first diene elastomer which is a styrene butadiene copolymer(s),
  • the first diene elastomer exhibits a glass transition temperature (TgDSC) of less than -40°C (for example, between -40°C and -110°C), preferably less than -45°C (for example, between -45°C and -105°C), more preferably less than -50°C (for example, between -50°C and -100°C), still more preferably less than -55°C (for example, between -55°C and -95°C), particularly at most -60°C (for example, -60°C to -90°C).
  • TgDSC glass transition temperature
  • the second diene elastomer is a polybutadiene(s) (BR) more preferably having a content (molar %) of 1,2-units of between 4% and 80% or those having a content (molar %) of cis-1,4-units of greater than 80%, more preferably greater than 90% (molar %), still more preferably greater than or equal to 96% (molar %).
  • BR polybutadiene(s)
  • the styrene-butadiene copolymer exhibits a styrene unit of less than 30% by weight (for example, between 3 and 30% by weight) per 100% by weight of the styrene-butadiene copolymer, preferably less than 27% by weight (for example, between 5 and 27% by weight), more preferably less than 23% by weight (for example, between 7 and 23% by weight), still more preferably less than 20% by weight (for example, between 10 and 20% by weight), particularly at most 18% by weight (for example, from 12 to 18%).
  • the styrene unit can be determined by 1H NMR method in accordance with ISO 21561.
  • the rubber composition according to the invention is based on a reinforcing filler.
  • a third aspect of the invention is the rubber composition according to the first aspect or the second aspect, wherein the amount of reinforcing filler is more than 10 phr, preferably more than 20 phr, more preferably more than 30 phr, still more preferably more than 40 phr, particularly more than 50 phr.
  • the amount of reinforcing filler is less than 300 phr.
  • the reinforcing filler may comprise a reinforcing organic filler (for example, carbon black), a reinforcing inorganic filler (for instance, silica) or the combinations thereof.
  • a reinforcing organic filler for example, carbon black
  • a reinforcing inorganic filler for instance, silica
  • Use may be made of any type of reinforcing filler known for its capabilities of reinforcing a rubber composition which can be used for the manufacture of the article, for example a reinforcing organic filler, such as carbon black, or a reinforcing inorganic filler, such as silica, with which a coupling agent is combined in a known way.
  • a reinforcing organic filler such as carbon black
  • a reinforcing inorganic filler such as silica
  • a fourth aspect of the invention is the rubber composition according to any one of the first to the third aspects, wherein at least one of the rubber compositions, especially at least the first rubber composition (FC), is such that the reinforcing filler predominately comprises carbon black, that is, the reinforcing filler comprises more than 50% by weight of carbon black per 100% of the reinforcing filler, preferably the reinforcing filler comprises more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, by weight of carbon black per 100% of the reinforcing filler.
  • the reinforcing filler predominately comprises carbon black, that is, the reinforcing filler comprises more than 50% by weight of carbon black per 100% of the reinforcing filler, preferably the reinforcing filler comprises more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, by weight of carbon black per 100% of the reinforcing filler.
  • carbon blacks all carbon blacks conventionally used in tires (“tire-grade” blacks) are suitable, such as for example reinforcing carbon blacks of the 100, 200 or 300 series in ASTM grades (such as for example, the N115, N134, N234, N326, N330, N339, N347 or N375 blacks), or carbon blacks higher series, the 500, 600, 700 or 800 series in ASTM grades (such as for example the N550, N660, N683, N772, N774 blacks).
  • the carbon blacks might for example be already incorporated in an elastomer matrix, for instance, a diene elastomer, in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600).
  • the rubber composition according to the invention is based on an epoxy.
  • the epoxy comprises at least one compound whose molecule comprises at least one epoxide functional group which is a three-membered ring comprising an oxygen atom and two carbon atoms.
  • the epoxy may harden by reacting with at least one co-reactant which is an epoxy hardener.
  • a fifth aspect of the invention is the rubber composition according to any one of the first to the fourth aspects, wherein the amount of epoxy is at least 1 phr, preferably at least 5 phr, more preferably at least 10 phr, still more preferably at least 15 phr, particularly at least 20 phr.
  • the amount of epoxy is at most 50 phr.
  • a sixth aspect of the invention is the rubber composition according to any one of the first to the fifth aspects, wherein the epoxy comprises at least one epoxy resin comprising at least two, preferably more than two, more preferably at least three, epoxide functional groups in a molecule.
  • the epoxy resin is selected from the group consisting of glycidyl ether epoxy resin(s), glycidyl amine epoxy resin(s), glycidyl ester epoxy resin(s), olefin oxidation (alicyclic) epoxy resin(s) and the combinations thereof, preferably selected from the group consisting of glycidyl ether epoxy resin(s) and the combinations thereof, more preferably selected from the group consisting of di-functional glycidyl ether epoxy resin(s), multi-functional glycidyl ether epoxy resin(s) and the combinations thereof, still more preferably selected from the group consisting multi-functional glycidyl ether epoxy resin(s) and the combinations thereof, particularly the multi-functional glycidyl ether epoxy resin(s) selected from the group consisting of oligomer epoxy resin(s), monomer epoxy resin(s) and the combinations thereof.
  • a seventh aspect of the invention is the rubber composition according to the sixth aspect, wherein the epoxy resin has a viscosity of less than 2000 mPa ⁇ s, preferably less than 1500 mPa ⁇ s, more preferably less than 1000 mPa ⁇ s, still more preferably less than 500 mPa ⁇ s, at 150°C.
  • the above viscosity at 150°C can measured in accordance with ASTM D4287.
  • An eighth aspect of the invention is the rubber composition according to the sixth aspect or the seventh aspect, wherein the epoxy resin has an epoxy equivalent weight of less than 500 g/eq, preferably less than 400 g/eq, more preferably less than 300 g/eq, still more preferably less than 200 g/eq, particularly less than 190 g/eq, more particularly less than 180 g/eq, still more particularly less than 170 g/eq.
  • the epoxy resin has an epoxy equivalent weight of less than 500 g/eq, preferably less than 400 g/eq, more preferably less than 300 g/eq, still more preferably less than 200 g/eq, particularly less than 190 g/eq, more particularly less than 180 g/eq, still more particularly less than 170 g/eq.
  • the epoxy equivalent can be determined in accordance with ISO 3001.
  • the rubber composition according to the invention is based on a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
  • the cyclic compound is a compound whose molecule comprising at least one ring (for example, homocyclic ring(s), heterocyclic ring(s)) formed with at least three atoms connected.
  • a ninth aspect of the invention is the rubber composition according to any one of the first to the eighth aspects, wherein the cyclic compound is an unsaturated cyclic compound.
  • the unsaturated cyclic compound is a cyclic compound whose molecule comprising at least one ring formed with at least three atoms connected, and the ring has at least one unsaturated bond (for example, benzene, benzothiazole)
  • the sulphur-based vulcanization accelerator is a vulcanization accelerator comprising at least one sulphur atom in a molecule.
  • the vulcanization accelerator The sulphur-based vulcaositions.ng.e.ce Actin. n but they comprise a hydrocarbon resin. the can promote the sulphur vulcanization reaction in the rubber composition.
  • the sulphenamide type vulcanization accelerator may be N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), 2-(4-morpholinothio)-benzothiazole (MBS), N,N’-dicyclohexyl-2-benzothiazole sulfenamide (DCBS) or the combinations thereof.
  • CBS N-cyclohexyl-2-benzothiazole sulfenamide
  • TBBS N-tert-butyl-2-benzothiazole sulfenamide
  • MBS 2-(4-morpholinothio)-benzothiazole
  • DCBS N,N’-dicyclohexyl-2-benzothiazole sulfenamide
  • a tenth aspect of the invention is the rubber composition according to any one of the first to the ninth aspects, wherein the amount of sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is between 0 and 10 phr.
  • An eleventh aspect of the invention is the rubber composition according to any one of the first to the tenth aspects, wherein the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is selected from the group consisting of thiourea type vulcanization accelerator(s), thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and the combinations thereof, preferably selected from the group consisting of thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and the combinations thereof, more preferably selected from the group consisting of 2-2’-Dithiobis(benzothiazole) (MBTS), Zinc-2-mercaptobenzothiazole (ZMBT), Tetrabenzylthiuram disulfide (TBzTD), Zin
  • a twelfth aspect of the invention is the rubber composition according to any one of the first to the eleventh aspects, wherein the crosslinking system is free of or is further based on sulphenamide type vulcanization accelerator of which the amount in phr is lower than that of the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator, preferably wherein the amount of sulphneamide type vulcanization accelerator is at less than 2 phr, preferably at most 1 phr.
  • the crosslinking system is free of sulphenamide type vulcanization accelerator.
  • the crosslinking system is further based on sulphur, vulcanization activator(s) or the combinations thereof.
  • the amount of sulphur is preferably between 0 and 10 phr.
  • the sulphur in the crosslinking (or vulcanization) system is to say vulcanization sulphur which may be sulphur, sulphur derived from a sulphur-donating agent or the combinations thereof.
  • the vulcanization activator(s) may be based on zinc (pure zinc and/or zinc derivatives (for example, zinc fatty acid salt)), fatty acid (in particular, stearic acid) or the combinations thereof.
  • a thirteenth aspect of the invention is the rubber composition according to any one of the first to the twelfth aspect, wherein the rubber composition is free of or is further based on an epoxy hardener of which the amount in phr is lower than that of the epoxy, preferably wherein the amount of epoxy hardener is less than 20 phr, more preferably less than 15 phr, still more preferably less than 10 phr, still preferably less than 5 phr, particularly less than 1 phr.
  • the epoxy hardener may comprise at least one compound selected from the group consisting of amine compound(s) (for example, polyamidoamine(s), aliphatic amine(s), alicyclic amine(s), aromatic amine(s), fatty aromatic amine(s), amine(s) having ether bond(s), amine(s) having hydroxyl group(s), polyoxypropylene amine(s), modified amine(s) (for example, epoxy modified amine(s), Mannich modified amine(s), amine(s) modified by Michael addition(s), amine salt compound(s) (for example, boron trifluoride amine complex compound(s))), amide compound(s) (for example, polyamide obtained by reacting polyamine), isocyanate compound(s), aromatic diazonium salt compound(s), guanidino compound(s), thiol compound(s) (for example, polythiol), aromatic sulfonium salt compound(s), phenol compound(s), acid anhydride compound(
  • the rubber composition is free of the epoxy hardener.
  • the rubber composition according to the invention may be based on all or a portion(s) of the usual additives generally used in the elastomer composition(s) intended in particular for laminates, in more particular for articles (for example, tires, shoes, conveyors or caterpillar tracks), in more particular for tires, in still more particular for snow tires or winter tires, such as, for example, protection agents, such as antiozone waxes, chemical antiozonants, antioxidants, plasticizing agent (for example, liquid plasticizer(s), hydrocarbon resin(s)), tackifying resins.
  • protection agents such as antiozone waxes, chemical antiozonants, antioxidants, plasticizing agent (for example, liquid plasticizer(s), hydrocarbon resin(s)), tackifying resins.
  • the composition can be also based on coupling activators when a coupling agent is used, agents for covering the reinforcing inorganic filler or more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the filler in the rubber matrix and of a lowering of the viscosity of the compositions, of improving their property of processing in the raw state; these agents are, for example, hydrolysable silanes, such as alkylalkoxysilanes, polyols, polyethers, or hydroxylated or hydrolysable polyorganosiloxanes.
  • hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, or hydroxylated or hydrolysable polyorganosiloxanes.
  • the rubber composition according to the invention may be manufactured in appropriate mixers using two successive preparation phases well known to a person skilled in the art: a first phase of thermomechanical working or kneading (referred to as “non-productive” phase) at high temperature, up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second phase of mechanical working (referred to as “productive” phase) at a lower temperature, typically of less than 110°C, for example between 40°C and 100°C, finishing phase during which sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system are incorporated.
  • a process which can be used for the manufacture of such composition comprises, for example and preferably, the following steps: - incorporating in the elastomer matrix(es), for instance, the diene elastomer(s), in a mixer, the reinforcing filler, the epoxy, during a first stage (referred to as a “non productive” stage) everything being kneaded thermomechanically (for example in one or more steps) until a maximum temperature of between 110°C and 190°C is reached; - cooling the combined mixture to a temperature of less than 100°C; - subsequently incorporating, during a second stage (referred to as a "productive" stage), sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system; and - kneading everything up to a maximum temperature of less than 110°C.
  • the first (non-productive) phase is carried out in a single thermomechanical stage during which all the necessary constituents are introduced into an appropriate mixer, such as a standard internal mixer, followed, in a second step, for example after kneading for 1 to 2 minutes, by the other additives, optional additional filler-covering agents or processing aids, with the exception of sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system.
  • the total kneading time, in this non-productive phase is preferably between 1 and 15 min.
  • sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system are then incorporated at low temperature (for example, between 40°C and 100°C), generally in an external mixer, such as an open mill; the combined mixture is then mixed (the second (productive) phase) for a few minutes, for example between 2 and 15 min.
  • the final composition thus obtained is subsequently extruded or calendered, for example in the form of a sheet or of a plaque, in particular for laboratory characterization, or else extruded in the form of a rubber profiled element which can be used directly as a laminate or an article, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread.
  • a fourteenth aspect of the invention is a laminate comprising at least two superposed portions comprising a first portion being made of a first rubber composition (FC) based on an elastomer matrix, a reinforcing filler and at least one of an epoxy or epoxy hardener, and a second portion being made of a second rubber composition (SC) different from the first rubber composition, and the second rubber composition (SC) being a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the amount in phr of the epoxy in the first rubber composition (FC) is lower than that in the second rubber composition (SC).
  • FC first rubber composition
  • SC second rubber composition
  • the laminate according to the fourteenth aspect it is possible to build a first layer of a homogeneous rubber composition, as the first rubber composition (FC), and a second layer of a homogeneous rubber composition, as the second rubber composition (SC), then to superpose the first layer onto the second layer or then to superpose the second layer onto the first layer, or to sandwich the other layer(s) or portion(s) between the first layer and the second layer, to get the laminate of the article.
  • FC first rubber composition
  • SC second layer of a homogeneous rubber composition
  • the first portion is adjacent to the second portion.
  • a preferred embodiment of the invention is an article comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably the article comprises a laminate according to the fourteenth aspect.
  • the article is intended to contact with the ground, preferably the article comprises a laminate according to the fourteenth aspect, and at least one of the first portion or the second portion, more preferably each of the portions, is intended to contact with the ground during the service life of the article.
  • the service life means the duration to use the article (for example, the term from the new state to the final state of the article, in case of that the article is a tire, the final state means a state on reaching the wear indicator bar(s) in the tread of tire).
  • the article comprises a laminate according to the fourteenth aspect, and the first portion is arranged nearer to the ground than the second portion.
  • the superposed portions which are the first portion and the second portion are radially superposed portions, that is, the first portion is radially exterior to the second portion.
  • the article comprises a laminate according to the fourteenth aspect, and the second portion is arranged nearer to the ground than the first portion.
  • the superposed portions which are the second portion and the first portion are radially superposed portions, that is, the second portion is radially exterior to the first portion.
  • the “radially” means “in the radial direction” which is a direction perpendicular to the axis of the rotation of a tire.
  • the article is a tire (for example, a tire tread), a shoe (for example, a shoe sole), a conveyor (for example, a conveyor belt) or a caterpillar track (for example, a caterpillar track tread), preferably a tire, a shoe or a caterpillar track, more preferably a tire tread, a shoe sole or a caterpillar track tread, still more preferably a tire tread.
  • a tire for example, a tire tread
  • a shoe for example, a shoe sole
  • a conveyor for example, a conveyor belt
  • a caterpillar track for example, a caterpillar track tread
  • the article is a tire comprising several tire parts which are a tread intended to at least partially contact with the ground, two sidewalls intended to contact with the outside air, but not to contact with the ground, two beads, a crown prolonged by two sidewalls ended by two beads, a carcass reinforcement formed at least one ply reinforced by radial textile cards, the carcass reinforcement passing into the crown and the sidewalls and the carcass reinforcement anchored in the two beads, preferably further comprising crown reinforcement placed between carcass reinforcement and the tread, more preferably further comprising an inner liner intended to protect the carcass reinforcement from diffusion of air coming from a space inside the tire, and the inner liner placed radially inner than carcass reinforcement.
  • a portion made of the rubber composition according to any one of the first to the thirteenth aspects, preferably the laminate according to the fourteenth aspect, is placed in at least one of the above tire parts, between two of the above tire parts, radially outer than one of the above tire parts, radially inner than one of the above tire parts or the combinations thereof.
  • a fifteenth aspect of the invention is a tire comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the tire comprises a laminate according to the fourteenth aspect, more preferably wherein the tire comprising a tread comprising a laminate according to the fourteenth aspect.
  • the tire is a snow tire.
  • the tires are particularly intended to equip passenger motor vehicles, including 4 ⁇ 4 (four-wheel drive) vehicles and SUV (Sport Utility Vehicles) vehicles, and industrial vehicles particularly selected from vans and heavy duty vehicles (i.e., bus or heavy road transport vehicles (lorries, tractors, trailers)).
  • passenger motor vehicles including 4 ⁇ 4 (four-wheel drive) vehicles and SUV (Sport Utility Vehicles) vehicles
  • industrial vehicles particularly selected from vans and heavy duty vehicles (i.e., bus or heavy road transport vehicles (lorries, tractors, trailers)).
  • the vulcanization (or curing) is carried out in a known way at a temperature generally of between 110°C and 190°C for a sufficient time which can vary, for example, between 5 and 90 min depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition(s) under consideration.
  • the invention relates to the rubber composition(s), to the laminate(s), to the article(s), to the tire (s) and the tire tread(s) described above, both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization).
  • the rubber compositions are based on a diene elastomer (a blend of SBR and BR) reinforced with carbon black or a blend of silica (as a reinforcing inorganic filler) and carbon black, at least one of an epoxy comprising an epoxy resin or an epoxy hardener comprising a polyamidoamine and a crosslinking system based on sulphur and 2-mercaptobenzothiazyl disulfide (as a cycle compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) or N-dicyclohexyl-2-benzothiazolesulphenamide (as a cycle compound that is a sulphur-based vulcanization accelerator that is a sulphenamide type
  • Each rubber composition was produced as follows: The reinforcing filler, at least one of the epoxy or the epoxy hardener, the elastomer matrix and the various other ingredients, with the exception of sulphur and the vulcanization accelerator in the crosslinking system, were successively introduced into an internal mixer having an initial vessel temperature of approximately 60°C; the mixer was thus approximately 70% full (% by volume). Thermomechanical working (non-productive phase) was then carried out in one stage, which lasts in total approximately 3 to 4 minutes, until a maximum “dropping” temperature of 165°C was reached.
  • the mixture thus obtained was recovered and cooled and then sulphur and the sulphenamide type vulcanization accelerator were incorporated on an external mixer (homofinisher) at 20 to 30°C, everything being mixed (productive phase) for an appropriate time (for example, between 5 and 12 min).
  • the rubber compositions thus obtained were subsequently calendered, either in the form of sheets (thickness of 2 to 3 mm) or of fine sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which could be used directly, after cutting and/or assembling to the desired dimensions, for example as tire semi-finished products, in particular as tire treads.
  • each of the treads comprises a laminate comprising two radially superposed portions which are a radially external portion and a radially internal portion adjacent to the radially external portion, the laminate being produced by superposition of the sheets of the rubber compositions (C-0 to C-6) respectively.
  • the radially internal and the radially external portions are made of C-0.
  • the radially internal portions are made of C-1 to C-6 respectively, and each of the radially external portions is made of C-1.
  • These tires as snow tires having treads comprising grooves circumferentially and/or axially extending, were conventionally manufactured and in all respects identical apart from the rubber compositions and the laminates of the tire treads. These tires are radial carcass passenger vehicle tires and the size of them is 205/55R16.
  • the durability performance was measured by a low-pressure test which checked after the inflated tires had traveled for a given time at a given temperature and at a given speed, they had undergone no visible delamination, rupture or tearing damage of the tread or carcass and that the inflation pressure measured at least one hour after the end of the test was not below the initial pressure.
  • the test was carried out in accordance with the United States FMVSS (Federal Motor Vehicle Safety Standard) regulation 571. 139 (published on Oct. 1, 2004) applying to “New tires for equipping motor vehicles other than motorcycles and low-speed vehicles with a total loaded weight of 10000 lbs or less and manufactured after 1975.
  • test tires positive in the low pressure test were fitted to the front and rear axles of motor vehicles, under nominal tire inflation pressure, and were subjected to rolling on a circuit in order to reproduce the tires in the worn state. Then, the above snow braking test was done with the worn tires. Each of the worn tires was still in the service life, and in each of them, each radially internal portion made of C-1 to C-5 respectively at least partially appeared on each tread surface and could at least partially contact with the ground.
  • the snow grip index of the examples T-2 to T-5 according to the invention were over 130 in relative units, the base 100 being selected for the reference tire T-1 (it should be remembered that a value of greater than 100 indicates an improved performance), which demonstrates that the examples T-2 to T-5 according to the invention have certainly higher values of the grip performance on snow than that of the reference T-1.
  • the rubber composition according to the invention allows an unexpectedly improved grip performance on snowy ground without deteriorating the durability performance.

Abstract

A rubber composition is based on at least an elastomer matrix, a reinforcing filler, an epoxy, and a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulpheamide type vulcanization accelerator.

Description

A RUBBER COMPOSITION
The field of the invention is that of rubber compositions intended in particular for laminates, in more particular for articles, for example, tires, shoes, conveyors or caterpillar tracks, in still more particular for tires, in especial for treads of tires, in more especial for treads of tires capable of rolling over ground surface covered with snow.
As is known, the snow tires classified in a category of use “snow”, identified by an inscription the alpine symbol (“3-peak-mountain with snowflake”), marked on their sidewalls, mean tires whose tread patterns, tread compounds and/or structures are primarily designed to achieve, in snow conditions, a performance better than that of normal tires intended for normal on-road use with regard to their abilities to initiate, maintain or stop vehicle motion.
JP 2018-188601
Snowy ground has a feature of having a low friction coefficient and a constant objective of manufacturers of rubber articles is improvement of a grip performance of rubber articles on snow-covered (snowy) ground without deteriorating the durability performance of rubber articles.
During their research, the inventor has discovered that a specific rubber composition intended in particular for a laminate, in more particular for a rubber article, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread, which allows an unexpectedly improved grip performance on snowy ground without deteriorating the durability performance.
In the present description, unless expressly stated otherwise, all the percentages (%) indicated are percentages by weight (wt%).
The expression “elastomer matrix” is understood to mean, in a given composition, all of the elastomers present in said rubber composition.
The abbreviation “phr” signifies parts by weight per hundred parts by weight of the elastomer matrix in the considered rubber composition.
In the present description, unless expressly indicated otherwise, each TgDSC (glass transition temperature) is measured in a known way by DSC (Differential Scanning Calorimetry) according to Standard ASTM D3418-08.
Any interval of values denoted by the expression “between a and b” represents the range of values of more than “a” and of less than “b” (i.e. the limits a and b excluded) whereas any interval of values denoted by the expression “from a to b” means the range of values going from “a” to “b” (i.e. including the strict limits a and b).
The expression “based on” should be understood in the present application to mean a composition comprising the mixture(s) and/or the product of the reaction of the various constituents used, some of the constituents being able or intended to react together, at least partly, during the various manufacturing phases of the composition, in particular during the vulcanization (curing).
[Rectified under Rule 91, 09.08.2019]
A first aspect of the invention is a rubber composition based on at least an elastomer matrix, a reinforcing filler, an epoxy, and a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
The specific rubber compositions allows an unexpectedly improved the grip performance on snowy ground without deteriorating the durability performance.
Each of the below aspect(s), the embodiment(s), the instantiation(s), and the variant(s) including each of the preferred range(s) and/or matter(s) may be applied to any one of the other aspect(s), the other embodiment(s), the other instantiation(s) and the other variant(s) of the invention unless expressly stated otherwise.
The rubber composition according to the invention is based on an elastomer matrix.
Elastomer (or loosely “rubber”, the two terms being regarded as synonyms) of the “diene” type is to be understood in a known manner as an (meaning one or more) elastomer derived at least partly (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).
These diene elastomers can be classified into two categories: “essentially unsaturated” or “essentially saturated”. Generally, the expression “essentially unsaturated” is understood to mean a diene elastomer resulting at least in part from conjugated diene monomers having a content of units of diene origin (conjugated dienes) which is greater than 15% (mol %); thus it is that diene elastomers such as butyl rubbers or diene/α -olefin copolymers of the EPDM type do not fall under the preceding definition and may especially be described as “essentially saturated” diene elastomers (low or very low content of units of diene origin, always less than 15%). In the category of “essentially unsaturated” diene elastomers, the expression “highly unsaturated” diene elastomer is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
Although it applies to any type of diene elastomer, a person skilled in the art of tires will understand that the invention is preferably employed with essentially unsaturated diene elastomers.
Given these definitions, the expression diene elastomer capable of being used in the compositions in accordance with the invention is understood in particular to mean:
(a) - any homopolymer obtained by polymerization of a conjugated diene monomer, preferably having from 4 to 12 carbon atoms;
(b) - any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with one or more vinyl aromatic compounds preferably having from 8 to 20 carbon atoms.
The following are suitable in particular as conjugated dienes: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C1-C5 alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1 ,3-butadiene or 2-methyl-3-isopropyl-1 ,3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene or 2,4-hexadiene. The following, for example, are suitable as vinylaromatic compounds: styrene, ortho-, meta- or para-methylstyrene, the“vinyltoluene” commercial mixture, para-(tert-butyl) styrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene or vinylnaphthalene.
A second aspect of the invention is the rubber composition according to the first aspect, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and the combinations thereof.
According to a preferred embodiment of the second aspect, the copolymers are preferably selected from the group consisting of butadiene copolymers the combinations thereof, more preferably selected from the group consisting of styrene-butadiene copolymers (SBR), butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and the combinations thereof, still more preferably selected from the group consisting of styrene-butadiene copolymers (SBR) and the combinations thereof.
The diene elastomer may have any microstructure which depends on the polymerization conditions used, in particular on the presence or absence of a modifying and/or randomizing agent and on the amounts of modifying and/or randomizing agent employed. This elastomer may, for example, be a block, statistical, sequential or micro sequential elastomer and may be prepared in dispersion or in solution. This elastomer may be coupled and/or star-branched or else functionalized with a coupling and/or star-branching or functionalizing agent.
According to a more preferred embodiment of the preferred embodiment, the elastomer matrix comprises more than 50 phr and up to 100 phr, preferably 55 to 95 phr, more preferably 60 to 90 phr, still more preferably 65 to 85 phr, particularly 70 to 80 phr, of a first diene elastomer which is a styrene butadiene copolymer(s), preferably a solution styrene butadiene copolymer(s), and the elastomer matrix comprises no second diene elastomer or comprises less than 50 phr, preferably 5 to 45 phr, more preferably 10 to 40 phr, still more preferably 15 to 35 phr, particularly 20 to 30 phr, of a second diene elastomer which is different from the first diene elastomer.
According to a still more preferred embodiment of the above more preferred embodiment, the first diene elastomer exhibits a glass transition temperature (TgDSC) of less than -40℃ (for example, between -40℃ and -110℃), preferably less than -45℃ (for example, between -45℃ and -105℃), more preferably less than -50℃ (for example, between -50℃ and -100℃), still more preferably less than -55℃ (for example, between -55℃ and -95℃), particularly at most -60℃ (for example, -60℃ to -90℃).
According to a particular embodiment of the above more preferred embodiment or the above still more preferred embodiment, the second diene elastomer is a polybutadiene(s) (BR) more preferably having a content (molar %) of 1,2-units of between 4% and 80% or those having a content (molar %) of cis-1,4-units of greater than 80%, more preferably greater than 90% (molar %), still more preferably greater than or equal to 96% (molar %).
According to a more particular embodiment of the above more preferred embodiment, the above still more preferred embodiment or the above particular embodiment, the styrene-butadiene copolymer exhibits a styrene unit of less than 30% by weight (for example, between 3 and 30% by weight) per 100% by weight of the styrene-butadiene copolymer, preferably less than 27% by weight (for example, between 5 and 27% by weight), more preferably less than 23% by weight (for example, between 7 and 23% by weight), still more preferably less than 20% by weight (for example, between 10 and 20% by weight), particularly at most 18% by weight (for example, from 12 to 18%). The styrene unit can be determined by 1H NMR method in accordance with ISO 21561.
The rubber composition according to the invention is based on a reinforcing filler.
A third aspect of the invention is the rubber composition according to the first aspect or the second aspect, wherein the amount of reinforcing filler is more than 10 phr, preferably more than 20 phr, more preferably more than 30 phr, still more preferably more than 40 phr, particularly more than 50 phr.
According to a preferred embodiment of the invention, the amount of reinforcing filler is less than 300 phr.
The reinforcing filler may comprise a reinforcing organic filler (for example, carbon black), a reinforcing inorganic filler (for instance, silica) or the combinations thereof.
Use may be made of any type of reinforcing filler known for its capabilities of reinforcing a rubber composition which can be used for the manufacture of the article, for example a reinforcing organic filler, such as carbon black, or a reinforcing inorganic filler, such as silica, with which a coupling agent is combined in a known way.
A fourth aspect of the invention is the rubber composition according to any one of the first to the third aspects, wherein at least one of the rubber compositions, especially at least the first rubber composition (FC), is such that the reinforcing filler predominately comprises carbon black, that is, the reinforcing filler comprises more than 50% by weight of carbon black per 100% of the reinforcing filler, preferably the reinforcing filler comprises more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, by weight of carbon black per 100% of the reinforcing filler.
As carbon blacks, all carbon blacks conventionally used in tires (“tire-grade” blacks) are suitable, such as for example reinforcing carbon blacks of the 100, 200 or 300 series in ASTM grades (such as for example, the N115, N134, N234, N326, N330, N339, N347 or N375 blacks), or carbon blacks higher series, the 500, 600, 700 or 800 series in ASTM grades (such as for example the N550, N660, N683, N772, N774 blacks). The carbon blacks might for example be already incorporated in an elastomer matrix, for instance, a diene elastomer, in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600).
The rubber composition according to the invention is based on an epoxy.
The epoxy comprises at least one compound whose molecule comprises at least one epoxide functional group which is a three-membered ring comprising an oxygen atom and two carbon atoms. The epoxy may harden by reacting with at least one co-reactant which is an epoxy hardener.
A fifth aspect of the invention is the rubber composition according to any one of the first to the fourth aspects, wherein the amount of epoxy is at least 1 phr, preferably at least 5 phr, more preferably at least 10 phr, still more preferably at least 15 phr, particularly at least 20 phr.
According to a preferred embodiment of the invention, the amount of epoxy is at most 50 phr.
A sixth aspect of the invention is the rubber composition according to any one of the first to the fifth aspects, wherein the epoxy comprises at least one epoxy resin comprising at least two, preferably more than two, more preferably at least three, epoxide functional groups in a molecule.
According to a preferred embodiment of the sixth aspect, the epoxy resin is selected from the group consisting of glycidyl ether epoxy resin(s), glycidyl amine epoxy resin(s), glycidyl ester epoxy resin(s), olefin oxidation (alicyclic) epoxy resin(s) and the combinations thereof, preferably selected from the group consisting of glycidyl ether epoxy resin(s) and the combinations thereof, more preferably selected from the group consisting of di-functional glycidyl ether epoxy resin(s), multi-functional glycidyl ether epoxy resin(s) and the combinations thereof, still more preferably selected from the group consisting multi-functional glycidyl ether epoxy resin(s) and the combinations thereof, particularly the multi-functional glycidyl ether epoxy resin(s) selected from the group consisting of oligomer epoxy resin(s), monomer epoxy resin(s) and the combinations thereof.
A seventh aspect of the invention is the rubber composition according to the sixth aspect, wherein the epoxy resin has a viscosity of less than 2000 mPa・s, preferably less than 1500 mPa・s, more preferably less than 1000 mPa・s, still more preferably less than 500 mPa・s, at 150℃.
The above viscosity at 150℃ can measured in accordance with ASTM D4287.
An eighth aspect of the invention is the rubber composition according to the sixth aspect or the seventh aspect, wherein the epoxy resin has an epoxy equivalent weight of less than 500 g/eq, preferably less than 400 g/eq, more preferably less than 300 g/eq, still more preferably less than 200 g/eq, particularly less than 190 g/eq, more particularly less than 180 g/eq, still more particularly less than 170 g/eq.
The epoxy equivalent can be determined in accordance with ISO 3001.
[Rectified under Rule 91, 09.08.2019]
The rubber composition according to the invention is based on a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
The cyclic compound is a compound whose molecule comprising at least one ring (for example, homocyclic ring(s), heterocyclic ring(s)) formed with at least three atoms connected.
A ninth aspect of the invention is the rubber composition according to any one of the first to the eighth aspects, wherein the cyclic compound is an unsaturated cyclic compound.
The unsaturated cyclic compound is a cyclic compound whose molecule comprising at least one ring formed with at least three atoms connected, and the ring has at least one unsaturated bond (for example, benzene, benzothiazole)
The sulphur-based vulcanization accelerator is a vulcanization accelerator comprising at least one sulphur atom in a molecule. The vulcanization acceleratorThe sulphur-based vulcaositions.ng.e.ce Actin.
n but they comprise a hydrocarbon resin.
the can promote the sulphur vulcanization reaction in the rubber composition.
[Rectified under Rule 91, 09.08.2019]
The sulphenamide type vulcanization accelerator may be N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), 2-(4-morpholinothio)-benzothiazole (MBS), N,N’-dicyclohexyl-2-benzothiazole sulfenamide (DCBS) or the combinations thereof.
[Rectified under Rule 91, 09.08.2019]
A tenth aspect of the invention is the rubber composition according to any one of the first to the ninth aspects, wherein the amount of sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is between 0 and 10 phr.
[Rectified under Rule 91, 09.08.2019]
An eleventh aspect of the invention is the rubber composition according to any one of the first to the tenth aspects, wherein the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is selected from the group consisting of thiourea type vulcanization accelerator(s), thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and the combinations thereof, preferably selected from the group consisting of thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and the combinations thereof, more preferably selected from the group consisting of 2-2’-Dithiobis(benzothiazole) (MBTS), Zinc-2-mercaptobenzothiazole (ZMBT), Tetrabenzylthiuram disulfide (TBzTD), Zinc ethylphenyldithiocarbamate (ZEPC), Zinc dibenzyldithiocarbamate (ZDBzC) and the combination thereof.
[Rectified under Rule 91, 09.08.2019]
A twelfth aspect of the invention is the rubber composition according to any one of the first to the eleventh aspects, wherein the crosslinking system is free of or is further based on sulphenamide type vulcanization accelerator of which the amount in phr is lower than that of the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator, preferably wherein the amount of sulphneamide type vulcanization accelerator is at less than 2 phr, preferably at most 1 phr.
[Rectified under Rule 91, 09.08.2019]
According to a preferred embodiment of the twelfth aspect, the crosslinking system is free of sulphenamide type vulcanization accelerator.
According to a preferred embodiment of the invention, the crosslinking system is further based on sulphur, vulcanization activator(s) or the combinations thereof. The amount of sulphur is preferably between 0 and 10 phr. The sulphur in the crosslinking (or vulcanization) system is to say vulcanization sulphur which may be sulphur, sulphur derived from a sulphur-donating agent or the combinations thereof. The vulcanization activator(s) may be based on zinc (pure zinc and/or zinc derivatives (for example, zinc fatty acid salt)), fatty acid (in particular, stearic acid) or the combinations thereof.
A thirteenth aspect of the invention is the rubber composition according to any one of the first to the twelfth aspect, wherein the rubber composition is free of or is further based on an epoxy hardener of which the amount in phr is lower than that of the epoxy, preferably wherein the amount of epoxy hardener is less than 20 phr, more preferably less than 15 phr, still more preferably less than 10 phr, still preferably less than 5 phr, particularly less than 1 phr.
The epoxy hardener may comprise at least one compound selected from the group consisting of amine compound(s) (for example, polyamidoamine(s), aliphatic amine(s), alicyclic amine(s), aromatic amine(s), fatty aromatic amine(s), amine(s) having ether bond(s), amine(s) having hydroxyl group(s), polyoxypropylene amine(s), modified amine(s) (for example, epoxy modified amine(s), Mannich modified amine(s), amine(s) modified by Michael addition(s), amine salt compound(s) (for example, boron trifluoride amine complex compound(s))), amide compound(s) (for example, polyamide obtained by reacting polyamine), isocyanate compound(s), aromatic diazonium salt compound(s), guanidino compound(s), thiol compound(s) (for example, polythiol), aromatic sulfonium salt compound(s), phenol compound(s), acid anhydride compound(s), basic active hydrogen compound(s), and the combinations thereof.
According to a preferred embodiment of the thirteenth aspect, the rubber composition is free of the epoxy hardener.
The rubber composition according to the invention may be based on all or a portion(s) of the usual additives generally used in the elastomer composition(s) intended in particular for laminates, in more particular for articles (for example, tires, shoes, conveyors or caterpillar tracks), in more particular for tires, in still more particular for snow tires or winter tires, such as, for example, protection agents, such as antiozone waxes, chemical antiozonants, antioxidants, plasticizing agent (for example, liquid plasticizer(s), hydrocarbon resin(s)), tackifying resins.
The composition can be also based on coupling activators when a coupling agent is used, agents for covering the reinforcing inorganic filler or more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the filler in the rubber matrix and of a lowering of the viscosity of the compositions, of improving their property of processing in the raw state; these agents are, for example, hydrolysable silanes, such as alkylalkoxysilanes, polyols, polyethers, or hydroxylated or hydrolysable polyorganosiloxanes.
[Rectified under Rule 91, 09.08.2019]
The rubber composition according to the invention may be manufactured in appropriate mixers using two successive preparation phases well known to a person skilled in the art: a first phase of thermomechanical working or kneading (referred to as “non-productive” phase) at high temperature, up to a maximum temperature of between 110℃ and 190℃, preferably between 130℃ and 180℃, followed by a second phase of mechanical working (referred to as “productive” phase) at a lower temperature, typically of less than 110℃, for example between 40℃ and 100℃, finishing phase during which sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system are incorporated.
[Rectified under Rule 91, 09.08.2019]
A process which can be used for the manufacture of such composition comprises, for example and preferably, the following steps:
- incorporating in the elastomer matrix(es), for instance, the diene elastomer(s), in a mixer, the reinforcing filler, the epoxy, during a first stage (referred to as a “non productive” stage) everything being kneaded thermomechanically (for example in one or more steps) until a maximum temperature of between 110℃ and 190℃ is reached;
- cooling the combined mixture to a temperature of less than 100℃;
- subsequently incorporating, during a second stage (referred to as a "productive" stage), sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system; and
- kneading everything up to a maximum temperature of less than 110℃.
[Rectified under Rule 91, 09.08.2019]
By way of example, the first (non-productive) phase is carried out in a single thermomechanical stage during which all the necessary constituents are introduced into an appropriate mixer, such as a standard internal mixer, followed, in a second step, for example after kneading for 1 to 2 minutes, by the other additives, optional additional filler-covering agents or processing aids, with the exception of sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system. The total kneading time, in this non-productive phase, is preferably between 1 and 15 min.
[Rectified under Rule 91, 09.08.2019]
After cooling the mixture thus obtained, sulphur and the cyclic compound (as the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) in the crosslinking system are then incorporated at low temperature (for example, between 40℃ and 100℃), generally in an external mixer, such as an open mill; the combined mixture is then mixed (the second (productive) phase) for a few minutes, for example between 2 and 15 min.
The final composition thus obtained is subsequently extruded or calendered, for example in the form of a sheet or of a plaque, in particular for laboratory characterization, or else extruded in the form of a rubber profiled element which can be used directly as a laminate or an article, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread.
A fourteenth aspect of the invention is a laminate comprising at least two superposed portions comprising a first portion being made of a first rubber composition (FC) based on an elastomer matrix, a reinforcing filler and at least one of an epoxy or epoxy hardener, and a second portion being made of a second rubber composition (SC) different from the first rubber composition, and the second rubber composition (SC) being a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the amount in phr of the epoxy in the first rubber composition (FC) is lower than that in the second rubber composition (SC).
As for making the laminate according to the fourteenth aspect, it is possible to build a first layer of a homogeneous rubber composition, as the first rubber composition (FC), and a second layer of a homogeneous rubber composition, as the second rubber composition (SC), then to superpose the first layer onto the second layer or then to superpose the second layer onto the first layer, or to sandwich the other layer(s) or portion(s) between the first layer and the second layer, to get the laminate of the article.
According to a preferred embodiment of the fourteenth aspect, the first portion is adjacent to the second portion.
A preferred embodiment of the invention is an article comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably the article comprises a laminate according to the fourteenth aspect.
According to a more preferred embodiment of the preferred embodiment, the article is intended to contact with the ground, preferably the article comprises a laminate according to the fourteenth aspect, and at least one of the first portion or the second portion, more preferably each of the portions, is intended to contact with the ground during the service life of the article.
The service life means the duration to use the article (for example, the term from the new state to the final state of the article, in case of that the article is a tire, the final state means a state on reaching the wear indicator bar(s) in the tread of tire).
According to a still preferred embodiment of the more preferred embodiment, the article comprises a laminate according to the fourteenth aspect, and the first portion is arranged nearer to the ground than the second portion. In case of that the article is a tire, the superposed portions which are the first portion and the second portion are radially superposed portions, that is, the first portion is radially exterior to the second portion.
According to another still preferred embodiment of the more preferred embodiment, the article comprises a laminate according to the fourteenth aspect, and the second portion is arranged nearer to the ground than the first portion. In case of that the article is a tire, the superposed portions which are the second portion and the first portion are radially superposed portions, that is, the second portion is radially exterior to the first portion.
The “radially” means “in the radial direction” which is a direction perpendicular to the axis of the rotation of a tire.
According to a particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment or the other still more preferred embodiment, the article is a tire (for example, a tire tread), a shoe (for example, a shoe sole), a conveyor (for example, a conveyor belt) or a caterpillar track (for example, a caterpillar track tread), preferably a tire, a shoe or a caterpillar track, more preferably a tire tread, a shoe sole or a caterpillar track tread, still more preferably a tire tread.
According to a more particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the other still more preferred embodiment or the particular embodiment, the article is a tire comprising several tire parts which are a tread intended to at least partially contact with the ground, two sidewalls intended to contact with the outside air, but not to contact with the ground, two beads, a crown prolonged by two sidewalls ended by two beads, a carcass reinforcement formed at least one ply reinforced by radial textile cards, the carcass reinforcement passing into the crown and the sidewalls and the carcass reinforcement anchored in the two beads, preferably further comprising crown reinforcement placed between carcass reinforcement and the tread, more preferably further comprising an inner liner intended to protect the carcass reinforcement from diffusion of air coming from a space inside the tire, and the inner liner placed radially inner than carcass reinforcement.
According to a still more particular of the embodiment of the more particular embodiment, a portion made of the rubber composition according to any one of the first to the thirteenth aspects, preferably the laminate according to the fourteenth aspect, is placed in at least one of the above tire parts, between two of the above tire parts, radially outer than one of the above tire parts, radially inner than one of the above tire parts or the combinations thereof.
A fifteenth aspect of the invention is a tire comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the tire comprises a laminate according to the fourteenth aspect, more preferably wherein the tire comprising a tread comprising a laminate according to the fourteenth aspect.
According to a preferred embodiment of the fifteenth aspect, the tire is a snow tire.
According to a more preferred embodiment of the fifteenth aspect or the preferred embodiment, the tires are particularly intended to equip passenger motor vehicles, including 4×4 (four-wheel drive) vehicles and SUV (Sport Utility Vehicles) vehicles, and industrial vehicles particularly selected from vans and heavy duty vehicles (i.e., bus or heavy road transport vehicles (lorries, tractors, trailers)).
The vulcanization (or curing) is carried out in a known way at a temperature generally of between 110℃ and 190℃ for a sufficient time which can vary, for example, between 5 and 90 min depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition(s) under consideration.
The invention relates to the rubber composition(s), to the laminate(s), to the article(s), to the tire (s) and the tire tread(s) described above, both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization).
The invention is further illustrated by the following non-limiting examples.
Example
[Rectified under Rule 91, 09.08.2019]
In the test, seven rubber compositions (C-0, C-1 and C-6: comparative examples, C-2 to C-5: examples according to the invention) were used. The rubber compositions are based on a diene elastomer (a blend of SBR and BR) reinforced with carbon black or a blend of silica (as a reinforcing inorganic filler) and carbon black, at least one of an epoxy comprising an epoxy resin or an epoxy hardener comprising a polyamidoamine and a crosslinking system based on sulphur and 2-mercaptobenzothiazyl disulfide (as a cycle compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator) or N-dicyclohexyl-2-benzothiazolesulphenamide (as a cycle compound that is a sulphur-based vulcanization accelerator that is a sulphenamide type vulcanization). The formulations of the rubber compositions are given at Table 1 with the content of the various products expressed in phr.
Each rubber composition was produced as follows: The reinforcing filler, at least one of the epoxy or the epoxy hardener, the elastomer matrix and the various other ingredients, with the exception of sulphur and the vulcanization accelerator in the crosslinking system, were successively introduced into an internal mixer having an initial vessel temperature of approximately 60℃; the mixer was thus approximately 70% full (% by volume). Thermomechanical working (non-productive phase) was then carried out in one stage, which lasts in total approximately 3 to 4 minutes, until a maximum “dropping” temperature of 165℃ was reached. The mixture thus obtained was recovered and cooled and then sulphur and the sulphenamide type vulcanization accelerator were incorporated on an external mixer (homofinisher) at 20 to 30℃, everything being mixed (productive phase) for an appropriate time (for example, between 5 and 12 min).
The rubber compositions thus obtained were subsequently calendered, either in the form of sheets (thickness of 2 to 3 mm) or of fine sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which could be used directly, after cutting and/or assembling to the desired dimensions, for example as tire semi-finished products, in particular as tire treads.
In order to confirm the effect of the invention, seven tires (T-0, T-1 and T-6: comparative examples, T-2 to T-5: examples according to the invention) comprising treads comprising the rubber compositions (C-0 to C-6) respectively are compared. Each of the treads comprises a laminate comprising two radially superposed portions which are a radially external portion and a radially internal portion adjacent to the radially external portion, the laminate being produced by superposition of the sheets of the rubber compositions (C-0 to C-6) respectively. In T-0, the radially internal and the radially external portions are made of C-0. In T-1 to T-6 respectively, the radially internal portions are made of C-1 to C-6 respectively, and each of the radially external portions is made of C-1.
These tires, as snow tires having treads comprising grooves circumferentially and/or axially extending, were conventionally manufactured and in all respects identical apart from the rubber compositions and the laminates of the tire treads. These tires are radial carcass passenger vehicle tires and the size of them is 205/55R16.
The durability performance was measured by a low-pressure test which checked after the inflated tires had traveled for a given time at a given temperature and at a given speed, they had undergone no visible delamination, rupture or tearing damage of the tread or carcass and that the inflation pressure measured at least one hour after the end of the test was not below the initial pressure. The test was carried out in accordance with the United States FMVSS (Federal Motor Vehicle Safety Standard) regulation 571. 139 (published on Oct. 1, 2004) applying to “New tires for equipping motor vehicles other than motorcycles and low-speed vehicles with a total loaded weight of 10000 lbs or less and manufactured after 1975.
The low-pressure test for the all test tires, except for T-0 and T-6, proved to be positive.
Further, all of the test tires positive in the low pressure test were fitted to the front and rear axles of motor vehicles, under nominal tire inflation pressure, and were subjected to rolling on a circuit in order to reproduce the tires in the worn state. Then, the above snow braking test was done with the worn tires. Each of the worn tires was still in the service life, and in each of them, each radially internal portion made of C-1 to C-5 respectively at least partially appeared on each tread surface and could at least partially contact with the ground.
Furthermore, as snow braking test, a 1,400 cc passenger car provided on all of the four wheels with the same kind of the worn tires under 220 kPa of tire inflation pressure mounted onto 6.5Jx16 rim was run on a snow covered road at a temperature of -10 ℃, the deceleration from 50 to 5 km/h during sudden longitudinal braking while anti-lock braking system (ABS) activated was measured. The above snow tests were conducted on a hard pack snow with a CTI penetrometer reading of about 90 in accordance with Standard ASTM F1805.
In the above test, the snow grip index of the examples T-2 to T-5 according to the invention were over 130 in relative units, the base 100 being selected for the reference tire T-1 (it should be remembered that a value of greater than 100 indicates an improved performance), which demonstrates that the examples T-2 to T-5 according to the invention have certainly higher values of the grip performance on snow than that of the reference T-1.
In conclusion, the rubber composition according to the invention allows an unexpectedly improved grip performance on snowy ground without deteriorating the durability performance.
Figure JPOXMLDOC01-appb-T000001
 (1) Solution SBR with 16% of styrene unit and 24% of unit 1,2 of the butadiene part (TgDSC = -65℃);
(2) BR with 0.3% of 1,2 vinyl; 2.7% of trans; 97% of cis-1,4 (TgDSC = -105℃);
(3) Carbon black (ASTM grade N234 from Cabot);
(4) Silica (“Zeosil 1165MP” from Rhodia (CTAB, BET: about 160 m2/g));
(5) Coupling agent TESPT (“Si69” from Evonik);
(6) Tris(4-hydroxyphenyl)methane triglycidyl ether (from Sigma-Aldrich, viscosity at 150℃: 43 mPa・s, epoxy equivalent weight: 160 g/eq);
(7) Epoxy hardener (polyamidoamine type epoxy hardener, “AP-032 1500 hardener” from Cemedine, viscosity at 25℃: 55000 mPa・s, polyamidoamine: 100%, Triethylenetetramine: 1.4%, Tetraethylenepentamine: 6.4%);
(8) Oleic sunflower oil (“Agripure 80” from Cargill, Weight percent oleic acid: 100%);
(9) MES oil (“Catenex SNR” from Shell);
(10) Hydrocarbon resin C5/C9 type (“Escorez ECR-373” from Exxon, TgDSC= 44℃);
(11) N-dicyclohexyl-2-benzothiazolesulphenamide (“Santocure CBS” from Flexsys);
(12) 2-mercaptobenzothiazyl disulfide (“Nocceler DM-P (DM) [MBTS]” from Ouchi Shinko Chemical Industrial);
(13) Zinc ethylphenyldithiocarbamate (“Nocceler PX [ZEPC]” from Ouchi Shinko Chemical Industrial);
(14) Tetrabenzylthiuram disulfide (“TBzTD” from ARKEMA);
(15) Zinc dibenzyldithiocarbamate (“Nocceler ZTC [ZDBzC]” from Ouchi Shinko Chemical Industrial).

Claims (15)

  1. [Rectified under Rule 91, 09.08.2019]
    A rubber composition based on at least:
    - an elastomer matrix;
    - a reinforcing filler;
    - an epoxy, and
    - a crosslinking system based on at least one cyclic compound that is a sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
  2. The rubber composition according to Claim 1, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and the combinations thereof.
  3. The rubber composition according to Claim 1 or Claim 2, wherein the amount of reinforcing filler is more than 10 phr.
  4. The rubber composition according to any one of Claims 1 to 3, wherein the reinforcing filler predominately comprises carbon black.
  5. The rubber composition according to any one of Claims 1 to 4, wherein the amount of epoxy is at least 1 phr.
  6. The rubber composition according to any one of Claims 1 to 5, wherein the epoxy comprises at least one epoxy resin comprising at least two epoxide functional groups in a molecule.
  7. The rubber composition according to Claim 6, wherein the epoxy resin has a viscosity of less than 2000 mPa・s at 150℃.
  8. The rubber composition according to Claim 6 or Claim 7, wherein the epoxy resin has an epoxy equivalent of less than 500 g/eq.
  9. The rubber composition according to any one of Claims 1 to 8, wherein the cyclic compound is an unsaturated cyclic compound.
  10. [Rectified under Rule 91, 09.08.2019]
    The rubber composition according to any one of Claims 1 to 9, wherein the amount of sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is between 0 and 10 phr.
  11. [Rectified under Rule 91, 09.08.2019]
    The rubber composition according to any one of Claims 1 to 10, wherein the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator is selected from the group consisting of thiourea type vulcanization accelerator(s), thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and the combinations thereof.
  12. [Rectified under Rule 91, 09.08.2019]
    The rubber composition according to any one of Claims 1 to 11, wherein the crosslinking system is free of or is further based on sulphenamide type vulcanization accelerator of which the amount in phr is lower than that of the sulphur-based vulcanization accelerator other than sulphenamide type vulcanization accelerator.
  13. The rubber composition according to any one of Claims 1 to 12, wherein the rubber composition is free of or is further based on an epoxy hardener of which the amount in phr is lower than that of the epoxy.
  14. A laminate comprising at least two superposed portions comprising a first portion being made of a first rubber composition (FC) based on an elastomer matrix, a reinforcing filler and at least one of an epoxy or epoxy hardener, and a second portion being made of a second rubber composition (SC) different from the first rubber composition (FC), and the second rubber composition being a rubber composition according to any one of Claims 1 to 13, preferably wherein the amount in phr of the epoxy in the first rubber composition (FC) is lower than that in the second rubber composition (SC).
  15. A tire comprising a rubber composition according to any one of Claims 1 to 13, preferably wherein the tire comprises a laminate according to Claim 14, more preferably wherein the tire comprising a tread comprising a laminate according to Claim 14.

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023174788A1 (en) * 2022-03-15 2023-09-21 Compagnie Generale Des Etablissements Michelin Rubber composition comprising an epoxy resin and a hardener

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WO1997036724A2 (en) 1996-04-01 1997-10-09 Cabot Corporation Novel elastomer composites, method and apparatus
WO1999016600A1 (en) 1997-09-30 1999-04-08 Cabot Corporation Elastomer composite blends and methods for producing them
US8877839B2 (en) * 2009-10-14 2014-11-04 Compagnie Generale Des Etablissements Michelin Rubber composition including an expoxide resin
CN107746487A (en) * 2017-10-31 2018-03-02 湖南辰砾新材料有限公司 A kind of high abrasion automobile tire tyre surface rubber composition
JP2018188601A (en) 2017-05-11 2018-11-29 住友ゴム工業株式会社 Rubber composition for studless tire
FR3074182A1 (en) * 2017-11-30 2019-05-31 Compagnie Generale Des Etablissements Michelin HIGH MODULE RUBBER COMPOSITION COMPRISING A VULCANIZATION ULTRA-ACCELERATOR

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WO1997036724A2 (en) 1996-04-01 1997-10-09 Cabot Corporation Novel elastomer composites, method and apparatus
WO1999016600A1 (en) 1997-09-30 1999-04-08 Cabot Corporation Elastomer composite blends and methods for producing them
US8877839B2 (en) * 2009-10-14 2014-11-04 Compagnie Generale Des Etablissements Michelin Rubber composition including an expoxide resin
JP2018188601A (en) 2017-05-11 2018-11-29 住友ゴム工業株式会社 Rubber composition for studless tire
CN107746487A (en) * 2017-10-31 2018-03-02 湖南辰砾新材料有限公司 A kind of high abrasion automobile tire tyre surface rubber composition
FR3074182A1 (en) * 2017-11-30 2019-05-31 Compagnie Generale Des Etablissements Michelin HIGH MODULE RUBBER COMPOSITION COMPRISING A VULCANIZATION ULTRA-ACCELERATOR

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023174788A1 (en) * 2022-03-15 2023-09-21 Compagnie Generale Des Etablissements Michelin Rubber composition comprising an epoxy resin and a hardener
FR3133615A1 (en) * 2022-03-15 2023-09-22 Compagnie Generale Des Etablissements Michelin RUBBER COMPOSITION COMPRISING AN EPOXY RESIN AND A HARDENER

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