WO2017216484A1 - Reinforced rubber composition for tires - Google Patents
Reinforced rubber composition for tires Download PDFInfo
- Publication number
- WO2017216484A1 WO2017216484A1 PCT/FR2017/051538 FR2017051538W WO2017216484A1 WO 2017216484 A1 WO2017216484 A1 WO 2017216484A1 FR 2017051538 W FR2017051538 W FR 2017051538W WO 2017216484 A1 WO2017216484 A1 WO 2017216484A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- composition
- boron nitride
- composition according
- hexagonal boron
- phr
- Prior art date
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- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- YXFVVABEGXRONW-UHFFFAOYSA-N toluene Substances CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 1
- FBBATURSCRIBHN-UHFFFAOYSA-N triethoxy-[3-(3-triethoxysilylpropyldisulfanyl)propyl]silane Chemical group CCO[Si](OCC)(OCC)CCCSSCCC[Si](OCC)(OCC)OCC FBBATURSCRIBHN-UHFFFAOYSA-N 0.000 description 1
- 239000012936 vulcanization activator Substances 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000001993 wax Substances 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- AUMBZPPBWALQRO-UHFFFAOYSA-L zinc;n,n-dibenzylcarbamodithioate Chemical compound [Zn+2].C=1C=CC=CC=1CN(C(=S)[S-])CC1=CC=CC=C1.C=1C=CC=CC=1CN(C(=S)[S-])CC1=CC=CC=C1 AUMBZPPBWALQRO-UHFFFAOYSA-L 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
- C08K5/548—Silicon-containing compounds containing sulfur
-
- 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
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
- C08K2003/382—Boron-containing compounds and nitrogen
- C08K2003/385—Binary compounds of nitrogen with boron
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/002—Physical properties
- C08K2201/006—Additives being defined by their surface area
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/019—Specific properties of additives the composition being defined by the absence of a certain additive
Definitions
- the present invention relates to diene rubber compositions reinforced by a reinforcing filler, in particular for the manufacture of tires or semi-finished products for tires, in particular to the treads of these tires.
- Fatty acids such as stearic acid
- Sulfenoic acid are known to be essential constituents of sulfur vulcanization systems used to vulcanize rubber compositions reinforced with a reinforcing filler. They also contribute to obtaining a rubber composition having good mechanical properties.
- the sulfur vulcanization systems usually comprise sulfur, zinc oxide and stearic acid at a rate ranging from 1 to 2 phr.
- Zinc oxide the primary vulcanization accelerator, makes it possible to accelerate the vulcanization reaction, which is interesting on the industrial level. Due to its low propensity
- zinc oxide is used with a stearic acid which forms a salt with zinc oxide.
- compositions comprising hexagonal boron nitride as a reinforcing filler and a coupling agent. of this filler, it is possible to obtain rubber compositions having good mechanical properties while also maintaining good thermal conductivity properties and improving hysteresis.
- a first subject of the invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler and a vulcanization system, characterized in that the composition comprises, as a reinforcing filler, hexagonal boron nitride having a BET specific surface area greater than or equal to 10 m 2 / g and at a level ranging from 30 to 350 parts per hundred parts of elastomer (phr), at least one organosilicon coupling agent capable of binding the nitride hexagonal boron to the diene elastomer, said composition being devoid of fatty acid or having a fatty acid level strictly less than 0.5 phr.
- the invention relates to a composition as defined above devoid of fatty acid or having a fatty acid level strictly less than 0.3 phr.
- the invention relates to a composition as defined above, in which the organosilicon coupling agent is chosen from polysulfide silanes, silanes bearing azodicarbonyl functional groups, and silanes carrying at least one functional group. thiol, silanes carrying at least one blocked thiol function and polyorganosiloxanes.
- the invention relates to a composition as defined above, in which the coupling agent is a polysulfide silane of general formula (I)
- x is an integer or fractional number greater than or equal to 2; preferably x is an integer or fractional number ranging from 2 to 8;
- R2 R2 in which:
- radicals R 1 substituted or unsubstituted, which are identical to or different from each other, represent a C 1 -C 18 alkyl group, a C 5 -C 18 cycloalkyl or a C 6 -C 18 aryl radical;
- radicals R 2 substituted or unsubstituted, which are identical to or different from each other, represent a hydroxyl, a Ci-Cis alkoxyl group or a C 5 -C 18 cycloalkoxyl radical.
- the fatty acid is a carboxylic acid comprising from 14 to 28 carbon atoms, preferably from 16 to 20 atoms, more preferably the fatty acid. is stearic acid.
- the invention relates to a composition as defined above, in which the vulcanization system comprises a zinc oxide at a rate ranging from 0.5 to 10 phr.
- the invention relates to a composition as defined above, wherein the diene elastomer is a substantially unsaturated elastomer.
- the invention relates to a composition as defined above, wherein the diene elastomer is an elastomer having a molar ratio of conjugated diene monomers greater than 15%.
- the invention relates to a composition as defined above in which the diene elastomer is chosen from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, copolymers of isoprene and mixtures of these elastomers.
- the invention relates to a composition as defined above in which the hexagonal boron nitride content ranges from 60 to 250 phr.
- the invention relates to a composition as defined above wherein the hexagonal boron nitride is the majority reinforcing filler of the composition.
- the invention relates to a composition as defined above in which the hexagonal boron nitride is the only reinforcing filler of the composition.
- the invention relates to a composition as defined above in which the hexagonal boron nitride is used in a blend with another reinforcing filler, this other reinforcing filler being present in the composition with a content of less than 30 phr. .
- the invention relates to a composition as defined above in which the level of coupling agent represents from 0.1 to 7% by weight relative to the amount of hexagonal boron nitride, preferably from 0 to , 2 to 5% by weight.
- the invention relates to a composition as defined above further comprising a plasticizer system, preferably with a plasticizer system level ranging from 5 to 150 phr, preferably from 10 to 130 phr, more preferably from 20 to 100 phr.
- the invention relates to a composition as defined above in which the plasticizer system mainly comprises a plasticizing resin having a glass transition temperature Tg greater than or equal to 20 ° C.
- the invention also relates to a semi-finished article comprising at least one composition as defined above.
- the semi-finished article may be a tread.
- the invention also relates to a tire comprising at least one composition as defined above or comprising at least one semi-finished article as defined above.
- BET specific surface area The BET specific surface area ("mass area") of hexagonal boron nitride particles and silica particles is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society "(Vol 60, page 309, February 1938), more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: one hour at 160 ° C. - relative pressure range p / po:
- the standard used to measure the BET specific surface area of the silica is transposed such as to measure the BET specific surface area of the hexagonal boron nitride.
- the thermal diffusimetry experiment consists in measuring the thermal diffusivity of a sample of the material. Diffusion corresponds to the surface velocity of penetration and attenuation of a thermal wave in a medium. Thermal diffusivity and thermal conductivity are synonymous.
- ⁇ is the thermal conductivity of the material in [W-rn 1 -K "1 ];
- p is the density of the material in [kg.m 3 ]
- C is the specific heat capacity of the material in [J.kg '.K 1 ];
- the measurement is performed on a NETZSCH LFA447 instrument marketed by the NETZSCH company.
- the principle of measurement is based on a rubber sample that is flashed with a Xenon lamp; the flash being preset by the manufacturer.
- a capacitor allows the lamp to be supplied with a voltage between 190V and 304V.
- the Xenon lamp emits a flash that causes a temperature rise in the sample.
- An infrared sensor detects the rise in temperature and delivers a voltage. This voltage can be amplified if its amplitude is not sufficient.
- the output thermogram allows the determination of diffusivity from the analysis software.
- the software is based on the Cape-Lehman model considering the total integration of the energy emitted.
- graphite varnish is by means of a rapid spray to about thirty centimeters of the sample.
- the measurement of the thickness of the sample is verified. It is made using a Mitutoyo micrometer, accurate to a micron.
- Traction data processing also makes it possible to draw the modulus curve as a function of the elongation.
- the module used here is the nominal secant modulus (or apparent) measured in first elongation, calculated by reducing to the initial section of the specimen.
- the nominal secant moduli (or apparent stresses, in MPa) at 100% and 300% of elongation respectively noted MSA100 and MSA300 are measured at first elongation at 23 ° C. ⁇ 2 ° C.
- the MSA300 / MSA100 ratio is an indicator parameter for evaluating a strengthening of a rubber composition.
- the glass transition temperature Tg is measured in a known manner by DSC (Differential Scanning Calorimetry), according to the ASTM D3418 (1999) standard.
- tan ( ⁇ ) max is measured on a viscoanalyzer (Metravib V A4000), according to the ASTM D5992-96 standard.
- the response of a sample of vulcanized composition (cylindrical specimen 4 mm in thickness and 400 mm 2 in section), subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz, is recorded under normal conditions. temperature (23 ° C) according to ASTM D 1349-99.
- a peak-to-peak deformation amplitude scan is performed. 0.1 to 50% (first cycle), then 50% to 1% (return cycle). The result exploited is the loss factor (tan ⁇ ).
- tan ( ⁇ ) max the maximum value of tan ⁇ observed (tan ( ⁇ ) max) is indicated. It also records the response of a sample of vulcanized composition subjected to a sinusoidal stress in alternating simple shear during a temperature sweep, subjected to a sinusoidal stress at imposed stress of 0.7 MPa and at a frequency of 10 Hz, at a temperature of 60 ° C and the dynamic shear complex modulus (G *) is measured at 60 ° C.
- the invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler and a vulcanization system, characterized in that the composition comprises, as reinforcing filler, hexagonal boron nitride having a surface area. BET specific greater than or equal to 10m 2 / g and at a rate ranging from 30 to 350 parts per hundred parts of elastomer, at least one organosilicon coupling agent capable of binding the hexagonal boron nitride to the diene elastomer, said composition being devoid of fatty acid or having a fatty acid level strictly less than 0.5 phr.
- composition based on is meant a composition comprising the mixture and / or the reaction product in situ of the various constituents used, some of these constituents being capable of or intended to react with one another at least in part, during the various phases of manufacture of the composition, or during the subsequent firing, modifying the composition as it was initially prepared.
- the compositions as implemented for the invention may be different in the uncrosslinked state and in the crosslinked state. In the present description, unless otherwise expressly indicated, all the percentages (%) indicated are percentages by weight.
- any range of values designated by the expression “between a and b” represents the range of values from more than “a” to less than “b” (that is, terminals a and b excluded) while any range of values designated by the expression “from a to b” means the range of values from “a” to "b” (i.e. including the strict bounds a and b).
- the abbreviation “pce” (phr: part per cent elastomer, usually “phr” in English for "per hundred part of rubber”) means parts by weight of one component per hundred parts by weight of elastomer (s). present in the rubber composition.
- major means in the sense of the present invention, a compound that represents the largest amount by weight or weight among the compounds of the same type. In other words, the mass of this compound represents more than 50% of the total mass of the compounds of the same type in the composition.
- a so-called majority reinforcing filler is the reinforcing filler representing the largest mass relative to the total mass of the reinforcing fillers of the composition. In other words, the mass of this reinforcing filler represents more than 50% of the total weight of the reinforcing fillers in the composition.
- fatty acid means a carboxylic acid whose hydrocarbon chain comprises from 14 to 28 carbon atoms, said chain being saturated or unsaturated.
- the carbon products mentioned in the description may be of fossil origin or biobased. In the latter case, they can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. These include polymers, plasticizers, fillers, etc.
- compositions according to the invention comprise at least one diene elastomer.
- elastomer or “diene” rubber must be understood in a known way (one means one or more) elastomer derived at least in part (ie, a homopolymer or a copolymer) of monomers dienes (monomers carrying two double bonds carbon-carbon, conjugated or not).
- diene elastomers can be classified in two categories: “essentially unsaturated” or “essentially saturated”.
- the term “essentially unsaturated” is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%); this is how elastomers dienes such as butyl rubbers or copolymers of dienes and alpha-olefins EPDM type do not fall within the above definition and may be particularly described as "essentially saturated” diene elastomers (low diene origin or very low, always less than 15%).
- the term “highly unsaturated” diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
- diene elastomer can be understood more particularly and may be used in the compositions according to the invention:
- diene elastomer any type of diene elastomer
- the person skilled in the art of the tire will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of the type (a) or (b) above.
- 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, 2-methyl-3-isopropyl 1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene.
- 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, 2-methyl-3-isopropyl 1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-he
- vinylaromatic compounds are suitable for example styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.
- the copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units.
- the aforementioned elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and amounts of modifying and / or randomizing agent used.
- the elastomers can be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization.
- a coupling agent for coupling with carbon black
- functional groups comprising a C-Sn bond (carbon-tin) or amino functional groups such as aminobenzophenone for example.
- aminobenzophenone for example.
- silanol or polysiloxane functional groups having a silanol end as described, for example, in FR 2 740 778 or US Pat. No.
- alkoxysilane groups as described for example in FR 2,765,882 or US 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US 2006 / 0089445) or polyether groups (as described for example in EP 1 127 909 or US 6,503,973, WO 2009/000750 and WO 2009/000752).
- elastomers such as SBR, BR, NR or IR
- the diene elastomer of the composition according to the invention is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated as BR), synthetic polyisoprenes (abbreviated to IR), and natural rubber ( abbreviated NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers.
- BR polybutadienes
- IR synthetic polyisoprenes
- NR natural rubber
- Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (abbreviated as SBR), isoprene-butadiene copolymers (abbreviated to BIR), copolymers of isoprene-styrene (abbreviated to SIR) and copolymers of isoprene-butadiene-styrene (abbreviated as SBIR).
- SBR butadiene-styrene copolymers
- BIR isoprene-butadiene copolymers
- SBIR copolymers of isoprene-butadiene-styrene
- the diene elastomer is predominantly (ie, for more than 50 phr) an SBR, whether it is an SBR prepared in emulsion (abbreviated to ESBR) or a SBR prepared in solution (abbreviated SSBR), or a blend (mixture) SBR / BR, SBR / NR (or SBR / IR), BR / NR (or BR / IR), or SBR / BR / NR (or SBR / BR / IR).
- an SBR elastomer In the case of an SBR elastomer (ESBR or SSBR), an SBR having an average styrene content, for example between 10% and 35% by weight, or a high styrene content, for example 35% by weight, is used in particular. at 55%, a vinyl content of the butadiene part of between 15% and 70%>, a content (mol%) of trans-1,4 bonds of between 15% and 75% and a glass transition temperature Tg of between -10 ° C and -65 ° C, preferably greater than or equal to -50 ° C.
- the diene elastomer of the composition represents at least 50% by weight of all the elastomers present in the composition; it may especially be a copolymer of styrene and butadiene.
- the elastomeric matrix of the composition according to the invention more preferably comprises at least one SBR with a content ranging from 60 to 100 phr, more preferably from 80 to 100 phr.
- the composition may comprise at least one SBR used in a blend with natural rubber or a synthetic polyisoprene which has a content ranging from 1 to 40 phr, and preferably ranging from 5 to 25 phr.
- the composition according to the invention may contain one or more synthetic elastomers other than diene, or even with polymers other than elastomers, for example thermoplastic polymers.
- composition according to the invention comprises at least as reinforcing filler, in particular majority, hexagonal boron nitride.
- Boron nitride is a chemical compound comprising boron and nitrogen of crude chemical formula BN. Boron nitride exists under several crystalline structures, including the hexagonal structure (h-BN).
- hexagonal boron nitride (h-BN) used as a filler in the compositions according to the invention is in the form of particles. Will be considered equivalent in the following description expressions "Hexagonal boron nitride particle (s)", “hexagonal boron nitride (s)”, “h-BN” and "hBN”.
- the h-BN is in the form of particles, in particular of medium size nano metric, that is to say, an average size strictly less than 1 micrometer. More particularly, the h-BN is chosen with an average size of less than or equal to 500 nanometers.
- the mean size of the h-BN particles ranges from 1 to 500 nm, preferably from 5 to 350 nm and even more preferably from 10 to 250 nm.
- Suitable for the invention are hexagonal boron nitrides whose BET specific surface area is greater than or equal to 10 m 2 / g, preferably greater than or equal to 15 m 2 / g and even more preferably greater than or equal to 20 m 2 / g.
- hexagonal boron nitrides sold by MK Impex Corp. may be mentioned. under the trade name "MK-hBN-N70" having a BET surface area of 25 m 2 / g and an average particle size of 70 nm and "MK-hBN-050" having a BET specific surface area of 20 m 2 / g and an average particle size of 500 nm.
- Mention may also be made of hexagonal boron nitrides marketed by ESK Ceramics GmbH & Co under the trade name "Boronid SCPI”.
- the level of hexagonal boron nitride in the composition may range from 60 to 250 phr.
- the hexagonal boron nitride may be used in blending with other fillers, in particular with an organic filler and / or a reinforcing inorganic filler.
- organic filler carbon blacks are particularly suitable, in particular reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N400, N660, N683, N772).
- any inorganic or mineral filler regardless of its color and origin (natural or synthetic), also called “white” charge, “clear” charge “Or” non-black “charge (“ non-black fi ller ”) as opposed to carbon black, this inorganic filler being able to reinforce on its own, without any other means than an agent of intermediate coupling, a rubber composition for the manufacture of a tire tread, in other words able to replace, in its reinforcing function, a conventional tire grade carbon black for tread.
- Such a filler is generally characterized by the presence of functional groups, in particular hydroxyl (-OH), at its surface, thereby requiring the use of an agent or coupling system intended to ensure a stable chemical bond between the isoprene elastomer and said charge.
- the reinforcing inorganic filler is a filler of the silica or alumina type, silica-alumina, titanium oxide or a mixture of these types of fillers.
- the silica (SiO 2 ) used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica, having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g.
- this other reinforcing filler is present in the composition with a content of less than or equal to 30 phr.
- the total reinforcing filler content ranges from 30 to 350 phr, preferably from 50 to 300 phr, more preferably from 60 to 250 phr.
- the hexagonal boron nitride is the majority reinforcing filler of the composition.
- the hexagonal boron nitride is the only reinforcing filler in the composition of the invention.
- the reinforcing filler described above can also be added, according to the intended application, inert fillers (ie non-reinforcing) such as clay particles, bentonite, talc, chalk, kaolin with a lower rate or equal to 10 phr and preferably less than or equal to 5 phr.
- composition according to the invention comprises at least one organosilicon coupling agent capable of binding the hexagonal boron nitride to the diene elastomer.
- coupling agent also called binding agent is meant a chemical compound whose function is to ensure the connection between the surface of the particles of inorganic fillers, in particular hexagonal boron nitride particles, and the diene elastomer, while facilitating the dispersion of this inorganic filler within the elastomeric matrix.
- coupling agent must be understood in a known manner, an agent capable of establishing a sufficient bond, chemical and / or physical, between the hexagonal boron nitride used as inorganic filler, and the diene elastomer; such a coupling agent, at least bifunctional, has for example as simplified general formula "Y -W-T" in which:
- Y represents a functional group ("Y" function) which is capable of binding physically and / or chemically to the hexagonal boron nitride used as a reinforcing filler;
- T represents a functional group ("T" function) capable of binding physically and / or chemically to the diene elastomer, for example via a sulfur atom.
- W represents a divalent group making it possible to connect Y and T.
- the coupling agents must not be confused with simple inorganic charge-covering agents which, in known manner, may comprise the reactive Y function with respect to the inorganic filler but lack the function.
- T active vis-à-vis the diene elastomer.
- organosilicon compound organic compound containing at least one carbon-silicon bond.
- the coupling agent used in the compositions of the present invention is an organosilicon compound providing a bond between the diene elastomer and the hexagonal boron nitride.
- the function which is intended to ensure the bond with the hexagonal boron nitride is provided by a silylated group, that is to say by the silicon atom carrier group.
- the silyl group comprises at least one hydrolyzable group such as a hydroxyl, an alkoxy.
- organosilicon compounds used as coupling agents are especially suitable polysulfide silanes, silanes carrying azodicarbonyl functional groups, silanes carrying at least one thiol function, silanes carrying at least one blocked thiol function. and polyorganosiloxanes.
- polysulfide silanes the polysulfurized alkoxysilanes and the symmetrical or asymmetric hydoxysilane polysulfides are particularly suitable.
- polysulfide silanes called “symmetrical” or “asymmetrical” silanes, are used according to their particular structure, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005 / 016650).
- polysulphide silanes corresponding to the following general formula (I) are, in particular, but not limited to the following definition:
- x is an integer or fractional number greater than or equal to 2; preferably, x is an integer or fractional number greater than 2 to 8;
- a 1 , A 2 which are identical or different, represent a divalent hydrocarbon radical (preferably a C 1 -C 18 alkylene group or a C 6 -C 12 arylene group, more particularly a C 1 -C 10 alkylene group, in particular a C1-C4 alkylene, especially propylene);
- the radicals R 1 which may be substituted or unsubstituted, which are identical to or different from one another, represent a C 1 -C 18 alkyl group, a C 5 -C 18 cycloalkyl or a C 6 -C 18 aryl ring (preferably C 1 -C 8 alkyl groups); 6 , cyclohexyl or phenyl, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl).
- the radicals R 2 substituted or unsubstituted, which are identical to or different from each other, represent a hydroxyl, a C 1 -C 18 alkoxyl group or a C 5 -C 18 cycloalkoxyl (preferably a group chosen from C 1 -C 6 alkoxyls) and C 6 -C 8 cycloalkoxyls, more preferably still a group selected from C 1 -C 4 alkoxyls, in particular methoxyl and ethoxyl).
- the average value of the "x" is a fractional number preferably between 2 and 5. more preferably close to 4.
- polysulphurized silanes mention may be made more particularly of polysulfides (in particular disulphides, trisulphides or tetrasulphides) of bis- (C 1 -C 4 ) alkoxyl-C 1 -C 4 alkylsilyl-alkyl (C 1 -C 4 ) C4)), such as, for example, bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides.
- polysulfides in particular disulphides, trisulphides or tetrasulphides
- polysulfides in particular disulphides, trisulphides or tetrasulfides
- bis- (monoalkoxyl (Ci-C 4 ) -dialkyl (Ci-C 4 ) silylpropyl) more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide.
- silanes bearing at least one thiol function (-SH) (called mercaptosilanes) and / or of at least one blocked thiol function, such as described for example in the patents or patent applications US 6,849,754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2010/072685 and WO 2008/055986.
- -SH thiol function
- blocked thiol function such as described for example in the patents or patent applications US 6,849,754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2010/072685 and WO 2008/055986.
- the amount of coupling agent used in the composition according to the invention is advantageously less than 20 phr.
- the level of coupling agent represents from 0.05% to 10% by mass relative to the mass of hexagonal boron nitride, preferably from 0.1 to 7% by weight and even more preferably from 0.2 to 5% by weight. mass.
- the rubber compositions of the invention may further comprise at least one plasticizer system.
- the plasticizer system may consist in particular of a plasticizing oil and / or a plasticizing resin and mixtures thereof.
- the compositions of the invention may comprise, for example, an extender oil (or plasticizing oil) and or a plasticizing resin or their mixture, the usual function of which is to facilitate the implementation, by a lowering of the Mooney plasticity.
- an extender oil or plasticizing oil
- a plasticizing resin or their mixture the usual function of which is to facilitate the implementation, by a lowering of the Mooney plasticity.
- these plasticizing oils more or less viscous, are liquids (that is to say, as a reminder, substances having the ability to eventually take the form of their container. ), in contrast to resins or rubbers which are inherently solid.
- the extender oil is chosen from the group consisting of polyolefinic oils (that is to say derived from the polymerization of oils, monoolefins or diolefins), paraffinic oils, naphthenic oils (low or high viscosity), aromatic oils, mineral oils, and mixtures of these oils.
- plasticizing resin is reserved in this application, by definition, to a compound which is solid on the one hand at room temperature (23 ° C.). (As opposed to a liquid plasticizer such as an oil), on the other hand compatible (that is to say miscible at the rate used, typically greater than 5 phr) with the rubber composition for which it is intended, so as to act as a true diluting agent.
- the plasticizer system mainly comprises a plasticizing resin having a glass transition temperature Tg greater than or equal to 20 ° C.
- the vulcanization system is a system based on sulfur or a sulfur donor agent and a primary vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the productive phase as described later, various known secondary accelerators or vulcanization activators such as zinc oxide. guanidine derivatives (in particular diphenylguanidine).
- accelerator any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type accelerators and their derivatives, accelerators of thiuram type, dithiocarbamates of zinc.
- accelerators are for example selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS”), tetrabenzylthiuram disulfide (“TBZTD”), N-cyclohexyl-2-benzothiazyl sulfenamide (“CBS”), N, N dicyclohexyl-2-benzothiazyl sulphenamide (“DCBS”), N-tert-butyl-2-benzothiazyl sulphenamide (“TBBS”), N-tert-butyl-2-benzothiazyl sulphenimide (“TBSI”), zinc dibenzyldithiocarbamate (“ ZBEC ”) and mixtures of these compounds.
- MBTS 2-mercaptobenzothiazyl disulfide
- TBZTD tetrabenzylthiuram disulfide
- CBS N-cyclohexyl-2-benzothiazyl sulf
- Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr.
- the primary vulcanization accelerator such as, for example, zinc oxide, is used at a preferred level of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.
- the composition of the invention is devoid of fatty acid.
- fatty acid means a carboxylic acid whose hydrocarbon chain comprises from 14 to 28 carbon atoms, said chain being saturated or unsaturated.
- the level of fatty acids in the composition is strictly less than 0.5 phr. More preferably, the level of fatty acid is strictly or equal to 0.3 phr, more preferably, the level of fatty acid is from 0 to 0.3 phr.
- the fatty acid is a carboxylic acid whose carbon chain comprises 16 to 20 carbon atoms; more preferably still, the fatty acid is stearic acid.
- the rubber compositions in accordance with the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, in particular treads, such as, for example, protective agents.
- protective agents such as antiozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents, tackifying resins, processing agents as described for example in the application WO 02/10269.
- the rubber compositions of the invention are manufactured in appropriate mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first phase of work or thermo-mechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second phase of mechanical work (sometimes referred to as a "productive" phase) at a lower temperature, typically less than 120 ° C., for example between 23 ° C. and 100 ° C., a finishing phase during which the vulcanization system is incorporated.
- a first phase of work or thermo-mechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C
- a second phase of mechanical work sometimes referred to as a "productive”
- compositions according to the invention can be used alone or in a blend (ie mixture) with any other rubber composition used for the manufacture of semi-finished products and tires. It goes without saying that the invention relates to the rubber compositions described above both in the "raw” or uncrosslinked state (ie before firing) in the so-called “cooked” or crosslinked state, or vulcanized state. (ie after vulcanization).
- compositions of the invention are well suited for the manufacture of semi-finished and finished products for tires, especially for tires intended to equip non-motorized vehicles such as bicycles, motor vehicles of the tourism type, SUVs (Sport Utility Vehicles), two-wheelers (especially motorcycles), airplanes, industrial vehicles chosen from light-duty trucks, heavy goods vehicles (ie subway, buses, road trucks and trailers), off-road vehicles, such as agricultural or engineering machinery, other transport or handling vehicles.
- non-motorized vehicles such as bicycles, motor vehicles of the tourism type, SUVs (Sport Utility Vehicles), two-wheelers (especially motorcycles), airplanes, industrial vehicles chosen from light-duty trucks, heavy goods vehicles (ie subway, buses, road trucks and trailers), off-road vehicles, such as agricultural or engineering machinery, other transport or handling vehicles.
- a semi-finished product is a rubber product intended for the manufacture of a tire. This may be any type of rubber strip, such as in particular treads, crown reinforcement plies (for example working plies, protective plies or hooping plies), carcass reinforcement plies. , flank plies, bead plies, plies of protectors, plies of underlays, plies of rubber blocks and other plies providing the interface between the aforementioned zones of the tires.
- the semi-finished article is a tread.
- the invention also relates to a tire comprising at least one semi-finished article as mentioned above or comprising at least one composition as defined above.
- the tire according to the invention may be intended to equip including non-motorized vehicles such as bicycles, tourism-type motor vehicles, SUV (Sport Utility Vehicles), two wheels (including motorcycles), aircraft, industrial vehicles chosen from vans, heavy goods vehicles (ie subway, buses, road machinery (trucks and trailers)), off-road vehicles, such as agricultural machinery or civil engineering, other transport or handling vehicles.
- non-motorized vehicles such as bicycles, tourism-type motor vehicles, SUV (Sport Utility Vehicles), two wheels (including motorcycles), aircraft, industrial vehicles chosen from vans, heavy goods vehicles (ie subway, buses, road machinery (trucks and trailers)), off-road vehicles, such as agricultural machinery or civil engineering, other transport or handling vehicles.
- the mixture thus obtained is recovered, cooled and the vulcanization system (sulfur and sulfenamide accelerator) is added to an external mixer (homogenizer) at 30 ° C., mixing the whole (productive phase) for about 5 to 6 hours. min.
- the compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties.
- the vulcanization (or baking) is carried out at 150 ° C for 70 minutes.
- compositions according to the invention were prepared according to the method detailed in the previous paragraph, they have the same basic formulation. They are differentiated by the nature of the reinforcing filler, the presence or absence of a coupling agent and the presence or absence of stearic acid. More specifically, the compositions C0, Cl, C2, C3 and C4 are defined as follows:
- the non-conforming composition C0 is a rubber composition comprising silica as a reinforcing filler and an alkoxysilane tetrasulfide coupling agent and stearic acid; this composition C0 is conventionally used for the manufacture of tire tread; the non-conforming composition C1 is a rubber composition comprising hexagonal boron nitride (hBN) as a reinforcing filler and stearic acid, it does not comprise a coupling agent.
- hBN hexagonal boron nitride
- the non-conforming composition C2 is a rubber composition comprising hexagonal boron nitride (hBN) as a reinforcing filler, stearic acid and an alkoxysilane tetrasulfide coupling agent.
- hBN hexagonal boron nitride
- composition according to the invention C3 is a rubber composition comprising hexagonal boron nitride (hBN) as reinforcing filler and an alkoxysilane tetrasulfide coupling agent; it does not include stearic acid
- the non-conforming composition C4 is a rubber composition comprising silica as a reinforcing filler and an alkoxysilane tetrasulfide coupling agent; it does not include stearic acid.
- the formulations of these five compositions are presented in Table 1 which follows, in which the quantities are expressed in phr:
- SBR copolymer comprising 27% styrene and in the polybutadiene part 24% -1,2 units (vinyl), 30%> 1,4 cis units and 46% -1,4 trans units; its glass transition temperature Tg is equal to -52 ° C;
- composition C0 When the stearic acid is removed in the composition C0, a non-compliant composition C4 is obtained. Compared to the composition C0, only the MSAIOO module is increased, the other properties (hysteresis, reinforcement and diffusivity) have not been modified.
- composition C1 has both a substantially lower MSA modulus 100 and an equally lower reinforcement (MSA300 / MSA100). In contrast, its thermal conductivity is improved over that of the composition C0.
- composition Cl having a conductivity equivalent to that of Cl, but which has a better reinforcement (MSA300 / MSA100 is increased significantly), a better hysteresis (significant decrease in Tan ( ⁇ ) max) and better rigidity (MSAIOO module increased).
- MSA300 / MSA100 is increased significantly
- hysteresis significant decrease in Tan ( ⁇ ) max
- rigidity MSAIOO module increased.
- the value of Tan ( ⁇ ) max reached for the composition C3 according to the invention is much lower than that obtained for the rubber matrix conventionally reinforced by a highly dispersible silica ( composition C0 not in accordance with the invention).
- the decrease in the value Tan ( ⁇ ) max is a recognized indicator of a reduction in the rolling resistance of tires and therefore the energy consumption of vehicles.
- the MSA100 value of the composition C3 is improved with respect to the value of MSA100 measured for the composition C0; indicating to the skilled person that the composition C3 has a better rigidity than the composition C0.
Abstract
The invention relates to a rubber composition that is based on at least one diene rubber, a reinforcing filler and a vulcanizing system, characterized in that the composition comprises, as a reinforcing filler, hexagonal boron nitride having a specific surface area BET of at least 10m2/g at a ratio of 30 to 350 parts per hundred parts of rubber, at least one organosilicon linking agent for linking the hexagonal boron nitride to the diene rubber, said composition not containing any fatty acid or a fatty acid content that is strictly lower than 0.5 phr.
Description
COMPOSITION DE CAOUTCHOUC RENFORCEE POUR PNEUMATIQUE REINFORCED RUBBER COMPOSITION FOR PNEUMATIC
[001] La présente invention se rapporte aux compositions de caoutchoucs diéniques renforcées par une charge renforçante, notamment destinées à la fabrication de pneumatiques ou de produits semi-finis pour pneumatiques, en particulier aux bandes de roulement de ces pneumatiques. The present invention relates to diene rubber compositions reinforced by a reinforcing filler, in particular for the manufacture of tires or semi-finished products for tires, in particular to the treads of these tires.
[002] Pour obtenir les propriétés de renforcement optimales conférées par une charge dans une bande de roulement de pneumatique et ainsi une haute résistance à l'usure, on sait qu'il convient d'une manière générale que cette charge soit présente dans la matrice élastomérique sous une forme finale qui soit à la fois la plus finement divisée possible et répartie de la façon la plus homogène possible. Or, de telles conditions ne peuvent être réalisées que dans la mesure où cette charge présente une très bonne aptitude, d'une part à s'incorporer dans la matrice lors du mélange avec l'élastomère et à se désagglomérer, d'autre part à se disperser de façon homogène dans cette matrice. In order to obtain the optimum reinforcing properties conferred by a load in a tire tread and thus a high wear resistance, it is known that it is generally appropriate for this load to be present in the matrix. elastomer in a final form that is both finely divided possible and distributed in the most homogeneous way possible. However, such conditions can be achieved only to the extent that this charge has a very good ability, on the one hand to incorporate into the matrix during mixing with the elastomer and to deagglomerate, on the other hand to to disperse homogeneously in this matrix.
[003] Depuis que les économies de carburant et la nécessité de protéger l'environnement sont devenues une priorité, il s'est avéré nécessaire de produire des pneumatiques ayant une résistance au roulement réduite, sans pénalisation de leur résistance à l'usure. Ceci a été rendu possible notamment grâce à la découverte de compositions de caoutchouc renforcées de charges inorganiques spécifiques qualifiées de « renforçantes », notamment des silices dites « hautement dispersibles », capables de rivaliser du point de vue renforçant avec un noir de carbone conventionnel de grade pneumatique, tout en offrant à ces compositions une hystérèse plus faible, synonyme d'une plus basse résistance au roulement pour les pneumatiques les comportant. Toutefois, les charges renforçantes inorganiques de type silice sont connues pour avoir une moins bonne conductivité thermique que les noirs de carbone. [003] Since fuel savings and the need to protect the environment have become a priority, it has been necessary to produce tires with reduced rolling resistance without penalizing their wear resistance. This has been made possible in particular by the discovery of rubber compositions reinforced with specific inorganic fillers described as "reinforcing", in particular so-called "highly dispersible" silicas, capable of competing from a reinforcing point of view with a conventional grade carbon black. pneumatic, while offering these compositions a lower hysteresis, synonymous with a lower rolling resistance for the tires comprising them. However, inorganic reinforcing fillers of silica type are known to have a lower thermal conductivity than carbon blacks.
[004] Or, il est connu des manufacturiers de pneumatiques qu'améliorer la conductivité thermique des compositions ou des articles semi-finis, tels que par exemple une bande de roulement, des nappes formant la ceinture de renforcement présentait beaucoup d'avantages notamment celui de mieux contrôler les échauffements locaux ou de mieux contrôler réchauffement général du pneu. Ces échauffements peuvent conduire à des modifications des propriétés des compositions de caoutchouc et notamment à changer les propriétés mécaniques de ces compositions. [004] However, it is known to tire manufacturers that improving the thermal conductivity of the compositions or semi-finished articles, such as for example a tread, webs forming the reinforcing belt had many advantages including that of to better control local heating or to better control the overall warming of the tire. These heating may lead to changes in the properties of the rubber compositions and in particular to change the mechanical properties of these compositions.
[005] L'amélioration de l'évacuation de la chaleur des compositions de caoutchouc présentant une faible hystérèse reste donc une préoccupation.
[006] Certaines solutions pour améliorer la conductivité thermique ont été proposées et consistent à faire appel à des charges renforçantes dont les propriétés de conductivité thermique sont reconnues telles que les noirs de carbone dérivés de l'acétylène. Ainsi, par exemple, la publication EP 1 767 570 propose différents coupages de noir de carbone utilisés classiquement dans les compositions de caoutchouc pour pneumatiques et de silice avec des noirs de carbone dérivés de l'acétylène dans des bandes de roulement associés à de fort taux de plastifiants (de l'ordre de 100 parties pour cent parties en poids d'élastomère, pce). Cependant l'utilisation de telle quantité de plastifiants risque d'entraîner une dégradation des propriétés mécaniques et hystérétiques des bandes de roulement ainsi obtenues. [005] The improvement of the heat removal of rubber compositions with low hysteresis therefore remains a concern. Some solutions for improving the thermal conductivity have been proposed and consist in using reinforcing fillers whose thermal conductivity properties are recognized such as carbon blacks derived from acetylene. Thus, for example, publication EP 1 767 570 proposes various carbon black blends conventionally used in tire rubber and silica compositions with carbon blacks derived from acetylene in treads associated with high levels of carbon. plasticizers (of the order of 100 parts per hundred parts by weight of elastomer, phr). However, the use of such a quantity of plasticizers may lead to a degradation of the mechanical and hysteretic properties of the treads thus obtained.
[007] Une autre solution proposée par la publication US 2010/0000650, consiste à ajouter du nitrure de bore dans une composition de caoutchouc pour pneumatique à base de noir de carbone ou de silice afin d'améliorer sa conductivité thermique. Cependant, le taux utilisé de nitrure de bore est faible. En effet, l'homme du métier sait qu'un taux important de nitrure de bore risquerait d'entraîner une dégradation des propriétés mécaniques de la composition concernée, voire même une dégradation de la résistance à l'usure des compositions ainsi obtenues. [008] Il existe donc toujours un intérêt à développer de nouvelles solutions pour améliorer la conductivité thermique de compositions de caoutchouc, notamment destinées à la fabrication de pneumatiques ou de produits semi-finis pour pneumatiques. [007] Another solution proposed by publication US 2010/0000650, is to add boron nitride in a tire rubber composition based on carbon black or silica to improve its thermal conductivity. However, the rate used of boron nitride is low. Indeed, the skilled person knows that a high level of boron nitride could lead to degradation of the mechanical properties of the composition concerned, or even degradation of the wear resistance of the compositions thus obtained. [008] There is therefore still an interest in developing new solutions to improve the thermal conductivity of rubber compositions, especially for the manufacture of tires or semi-finished products for tires.
[009] De manière surprenante, les Demanderesses ont trouvé lors de leurs recherches qu'en supprimant ou en limitant le taux d'acides gras à 0,5 pce (partie pour cent parties d'élastomère) dans des compositions comprenant du nitrure de bore hexagonal à titre de charge renforçante et un agent de couplage de cette charge, il est possible d'obtenir des compositions de caoutchouc ayant de bonnes propriétés mécaniques tout en maintenant par ailleurs de bonnes propriétés de conductivité thermique et en améliorant l'hystérèse. [009] Surprisingly, the Applicants have found during their research that by eliminating or limiting the level of fatty acids to 0.5 phr (part per hundred parts of elastomer) in compositions comprising boron nitride As a reinforcing filler and a coupling agent for this filler, it is possible to obtain rubber compositions having good mechanical properties while at the same time maintaining good properties of thermal conductivity and improving hysteresis.
[0010] Les acides gras, tel que l'acide stéarique, sont connus pour être des constituants essentiels des systèmes de vulcanisation au soufre utilisés pour vulcaniser les compositions de caoutchouc renforcées par une charge renforçante. Ils contribuent aussi à l'obtention de composition de caoutchouc ayant de bonnes propriétés mécaniques. Fatty acids, such as stearic acid, are known to be essential constituents of sulfur vulcanization systems used to vulcanize rubber compositions reinforced with a reinforcing filler. They also contribute to obtaining a rubber composition having good mechanical properties.
[0011] En effet, les systèmes de vulcanisation au soufre comprennent usuellement du soufre, de l'oxyde de zinc et de l'acide stéarique à un taux allant de 1 à 2 pce. L'oxyde de zinc, accélérateur primaire de vulcanisation, permet d'accélérer la réaction de vulcanisation, ce qui est intéressant sur le plan industriel. Du fait de sa faible propension
à se mélanger à la matrice élastomérique, on utilise l'oxyde de zinc avec un acide stéarique qui forme un sel avec l'oxyde de zinc. Indeed, the sulfur vulcanization systems usually comprise sulfur, zinc oxide and stearic acid at a rate ranging from 1 to 2 phr. Zinc oxide, the primary vulcanization accelerator, makes it possible to accelerate the vulcanization reaction, which is interesting on the industrial level. Due to its low propensity To mix with the elastomeric matrix, zinc oxide is used with a stearic acid which forms a salt with zinc oxide.
[0012] En l'absence d'acide stéarique, il est connu que les propriétés mécaniques des compositions de caoutchouc sont plus faibles. On observe en particulier une baisse notable de la rigidité. Ceci rend plus difficile l'ajustement des propriétés mécaniques des compositions, notamment pour une utilisation en bande de roulement. In the absence of stearic acid, it is known that the mechanical properties of the rubber compositions are lower. In particular, there is a noticeable decrease in rigidity. This makes it more difficult to adjust the mechanical properties of the compositions, in particular for use in tread.
[0013] Or, de façon surprenante, les Demanderesses ont trouvé qu'en supprimant ou en limitant le taux d'acides gras à 0,5 pce dans des compositions comprenant du nitrure de bore hexagonal à titre de charge renforçante et un agent de couplage de cette charge, il est possible d'obtenir des compositions de caoutchouc ayant de bonnes propriétés mécaniques tout en maintenant par ailleurs de bonnes propriétés de conductivité thermique et en améliorant l'hystérèse. Surprisingly, the Applicants have found that by suppressing or limiting the level of fatty acids to 0.5 phr in compositions comprising hexagonal boron nitride as a reinforcing filler and a coupling agent. of this filler, it is possible to obtain rubber compositions having good mechanical properties while also maintaining good thermal conductivity properties and improving hysteresis.
[0014] En conséquence, un premier objet de l'invention concerne une composition de caoutchouc à base d'au moins un élastomère diénique, une charge renforçante et un système de vulcanisation, caractérisée en ce que la composition comprend à titre de charge renforçante du nitrure de bore hexagonal ayant une surface spécifique BET supérieure ou égale à 10 m2/g et à un taux allant de 30 à 350 parties pour cent parties d'élastomère (pce), au moins un agent de couplage organosilicié capable de lier le nitrure de bore hexagonal à l'élastomère diénique, ladite composition étant dépourvue d'acide gras ou ayant un taux d'acide gras strictement inférieur à 0,5 pce. [0015] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dépourvue d'acide gras ou ayant un taux d'acide gras strictement inférieur à 0,3 pce. Accordingly, a first subject of the invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler and a vulcanization system, characterized in that the composition comprises, as a reinforcing filler, hexagonal boron nitride having a BET specific surface area greater than or equal to 10 m 2 / g and at a level ranging from 30 to 350 parts per hundred parts of elastomer (phr), at least one organosilicon coupling agent capable of binding the nitride hexagonal boron to the diene elastomer, said composition being devoid of fatty acid or having a fatty acid level strictly less than 0.5 phr. Preferably, the invention relates to a composition as defined above devoid of fatty acid or having a fatty acid level strictly less than 0.3 phr.
[0016] Préférentiellement, l'invention concerne une composition telle que définie ci- dessus, dans laquelle l'agent de couplage organosilicié est choisi parmi les silanes polysulfures, les silanes porteurs de groupements fonctionnels azodicarbonyle, les silanes porteurs d'au moins une fonction thiol, les silanes porteurs d'au moins une fonction thiol bloqué et les polyorganosiloxanes. [0017] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus, dans laquelle l'agent de couplage est un silane polysulfure de formule générale (I)Preferably, the invention relates to a composition as defined above, in which the organosilicon coupling agent is chosen from polysulfide silanes, silanes bearing azodicarbonyl functional groups, and silanes carrying at least one functional group. thiol, silanes carrying at least one blocked thiol function and polyorganosiloxanes. Preferably, the invention relates to a composition as defined above, in which the coupling agent is a polysulfide silane of general formula (I)
dans laquelle:
x est un nombre entier ou fractionnaire supérieur ou égal à 2 ; de préférence x est un nombre entier ou fractionnaire allant de 2 à 8 ; in which: x is an integer or fractional number greater than or equal to 2; preferably x is an integer or fractional number ranging from 2 to 8;
les symboles Ai, A2, identiques ou différents, représentent chacun un radical hydrocarboné divalent comportant de 1 à 18 atomes de carbone; the symbols Ai, A 2 , identical or different, each represent a divalent hydrocarbon radical having 1 to 18 carbon atoms;
- les symboles Zl s Z2 , identiques ou différents, répondent chacun à l'une des trois formules ci-après: - Z ls symbols Z 2, identical or different, each correspond to one of the three following formulas:
R1 R1 R2 R1 R1 R2
—Si— R1 ; — Si— R2 ; — Si— R2 , -Si-R1; - Si- R2; - Si- R2,
R2 R2 dans lesquelles: R2 R2 in which:
- les radicaux R1, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkyle en Ci-Cis, un cycloalkyle en C5-C18 ou un aryle en C6-Ci8 , the radicals R 1 , substituted or unsubstituted, which are identical to or different from each other, represent a C 1 -C 18 alkyl group, a C 5 -C 18 cycloalkyl or a C 6 -C 18 aryl radical;
- les radicaux R2, substitués ou non substitués, identiques ou différents entre eux, représentent, un hydroxyle, un groupe alkoxyle en Ci-Cis ou un cycloalkoxyle en C5-C18. the radicals R 2 , substituted or unsubstituted, which are identical to or different from each other, represent a hydroxyl, a Ci-Cis alkoxyl group or a C 5 -C 18 cycloalkoxyl radical.
[0018] Préférentiellement, lorsque l'invention n'est pas dépourvue d'acides gras, l'acide gras est un acide carboxylique comprenant de 14 à 28 atomes de carbone, de préférence de 16 à 20 atomes, plus préférentiellement l'acide gras est l'acide stéarique. Preferably, when the invention is not devoid of fatty acids, the fatty acid is a carboxylic acid comprising from 14 to 28 carbon atoms, preferably from 16 to 20 atoms, more preferably the fatty acid. is stearic acid.
[0019] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus, dans laquelle le système de vulcanisation comprend un oxyde de zinc à un taux allant de 0,5 à 10 pce Preferably, the invention relates to a composition as defined above, in which the vulcanization system comprises a zinc oxide at a rate ranging from 0.5 to 10 phr.
[0020] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus, dans laquelle l'élastomère diénique est un élastomère essentiellement insaturé. Preferably, the invention relates to a composition as defined above, wherein the diene elastomer is a substantially unsaturated elastomer.
[0021] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus, dans laquelle l'élastomère diénique est un élastomère ayant un taux molaire de monomères diènes conjugués supérieur à 15 % . Preferably, the invention relates to a composition as defined above, wherein the diene elastomer is an elastomer having a molar ratio of conjugated diene monomers greater than 15%.
[0022] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle l'élastomère diénique est choisi dans le groupe constitué par les polybutadiènes, les polyisoprènes synthétiques, le caoutchouc naturel, les copolymères de butadiène, les copolymères d'isoprène et les mélanges de ces élastomères.
[0023] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le taux de nitrure de bore hexagonal va de 60 à 250 pce. Preferably, the invention relates to a composition as defined above in which the diene elastomer is chosen from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, copolymers of isoprene and mixtures of these elastomers. Preferably, the invention relates to a composition as defined above in which the hexagonal boron nitride content ranges from 60 to 250 phr.
[0024] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le nitrure de bore hexagonal est la charge renforçante majoritaire de la composition. Preferably, the invention relates to a composition as defined above wherein the hexagonal boron nitride is the majority reinforcing filler of the composition.
[0025] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le nitrure de bore hexagonal est la seule charge renforçante de la composition. Preferably, the invention relates to a composition as defined above in which the hexagonal boron nitride is the only reinforcing filler of the composition.
[0026] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le nitrure de bore hexagonal est utilisé en coupage avec une autre charge renforçante, cette autre charge renforçante étant présente dans la composition avec un taux inférieur à 30 pce. Preferably, the invention relates to a composition as defined above in which the hexagonal boron nitride is used in a blend with another reinforcing filler, this other reinforcing filler being present in the composition with a content of less than 30 phr. .
[0027] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le taux d'agent de couplage représente de 0,1 à 7% massique par rapport à la quantité de nitrure de bore hexagonal, de préférence de 0,2 à 5% massique. Preferably, the invention relates to a composition as defined above in which the level of coupling agent represents from 0.1 to 7% by weight relative to the amount of hexagonal boron nitride, preferably from 0 to , 2 to 5% by weight.
[0028] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus comprenant en outre un système plastifiant, de préférence avec un taux de système plastifiant allant de 5 à 150 pce, de préférence allant de 10 à 130 pce, plus préférentiellement de 20 à 100 pce. Preferably, the invention relates to a composition as defined above further comprising a plasticizer system, preferably with a plasticizer system level ranging from 5 to 150 phr, preferably from 10 to 130 phr, more preferably from 20 to 100 phr.
[0029] Préférentiellement, l'invention concerne une composition telle que définie ci- dessus dans laquelle le système plastifiant comprend majoritairement une résine plastifiante ayant une température de transition vitreuse Tg supérieure ou égale 20°C. [0030] L'invention a également pour objet un article semi-fini comprenant au moins une composition telle que définie ci-dessus. Préférentiellement, l'article semi-fini peut être une bande de roulement. Preferably, the invention relates to a composition as defined above in which the plasticizer system mainly comprises a plasticizing resin having a glass transition temperature Tg greater than or equal to 20 ° C. The invention also relates to a semi-finished article comprising at least one composition as defined above. Preferably, the semi-finished article may be a tread.
[0031] L'invention a également pour objet un pneumatique comprenant au moins une composition telle que défînie-ci dessus ou comprenant au moins un article semi-fini tel que défini ci-dessus. The invention also relates to a tire comprising at least one composition as defined above or comprising at least one semi-finished article as defined above.
I. MESURES ET TESTS UTILISES I. MEASUREMENTS AND TESTS USED
• Surface spécifique BET
[0032] La surface spécifique (« aire massique ») BET des particules de nitrure de bore hexagonal et des particules de silice est déterminée par adsorption de gaz à l'aide de la méthode de Brunauer-Emmett-Teller décrite dans « The Journal of the American Chemical Society » (Vol. 60, page 309, février 1938), plus précisément selon la norme française NF ISO 9277 de décembre 1996 [méthode volumétrique multipoints (5 points) - gaz: azote - dégazage: une heure à 160°C - domaine de pression relative p/po : • BET specific surface area The BET specific surface area ("mass area") of hexagonal boron nitride particles and silica particles is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society "(Vol 60, page 309, February 1938), more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: one hour at 160 ° C. - relative pressure range p / po:
[0.05 à 0.17]. [0033] La norme utilisée pour mesurer la surface spécifique BET de la silice est transposée telle qu'elle pour mesurer la surface spécifique BET du nitrure de bore hexagonal. [0.05 to 0.17]. The standard used to measure the BET specific surface area of the silica is transposed such as to measure the BET specific surface area of the hexagonal boron nitride.
Diffusivité thermique Thermal diffusivity
[0034] L'expérience de diffusimétrie thermique consiste à mesurer la diffusivité thermique d'un échantillon du matériau. La diffusivité correspond à la vitesse surfacique de pénétration et d'atténuation d'une onde thermique dans un milieu. La diffusivité thermique et la conductivité thermique sont synonymes. The thermal diffusimetry experiment consists in measuring the thermal diffusivity of a sample of the material. Diffusion corresponds to the surface velocity of penetration and attenuation of a thermal wave in a medium. Thermal diffusivity and thermal conductivity are synonymous.
D = À/(p.C) (en m7s) où D = to / (p.C) (in m7s) where
λ est la conductivité thermique du matériau en [W-rn 1 -K"1] ; λ is the thermal conductivity of the material in [W-rn 1 -K "1 ];
p est la masse volumique du matériau en [kg.m 3] ; p is the density of the material in [kg.m 3 ];
C est la capacité thermique massique du matériau en [J.kg '.K 1] ; C is the specific heat capacity of the material in [J.kg '.K 1 ];
[0035] La mesure est effectuée sur un instrument NETZSCH LFA447 commercialisé par la société NETZSCH. Le principe de la mesure repose sur un échantillon de caoutchouc qui est soumis à un flash d'une lampe au Xénon ; le flash étant préréglé par le constructeur. Un condensateur permet l'envoi à la lampe d'une tension comprise entre 190V et 304V. La lampe au Xénon émet ainsi un flash qui provoque une élévation de température au niveau de l'échantillon. Un capteur infrarouge détecte l'élévation de température et délivre une tension. Cette tension peut être amplifiée si son amplitude n'est pas suffisante. Le thermogramme de sortie permet la détermination de la diffusivité à partir du logiciel d'analyse. Le logiciel se base sur le modèle de Cape-Lehman en considérant l'intégration totale de l'énergie émise. The measurement is performed on a NETZSCH LFA447 instrument marketed by the NETZSCH company. The principle of measurement is based on a rubber sample that is flashed with a Xenon lamp; the flash being preset by the manufacturer. A capacitor allows the lamp to be supplied with a voltage between 190V and 304V. The Xenon lamp emits a flash that causes a temperature rise in the sample. An infrared sensor detects the rise in temperature and delivers a voltage. This voltage can be amplified if its amplitude is not sufficient. The output thermogram allows the determination of diffusivity from the analysis software. The software is based on the Cape-Lehman model considering the total integration of the energy emitted.
Préparation des échantillons : Sample preparation:
Découpe des échantillons : Cutting samples:
[0036] A partir de plaques de mélanges cuites d'environ 2 mm d'épaisseur, on découpe à Γ emporte-pièce un disque de 12 mm de diamètre.
Homogénéisation des échantillons : From baked mix plates of about 2 mm thick, is cut with a punch un a disc of 12 mm in diameter. Homogenization of samples:
[0037] Une fois les échantillons découpés, on applique 3 couches de vernis graphite afin d'obtenir des surfaces de mesures homogènes et conductrices. Once the samples cut, applying 3 layers of graphite varnish to obtain homogeneous and conductive measuring surfaces.
[0038] L'application de vernis graphite se fait au moyen d'un spray rapide à une trentaine de centimètres de l'échantillon. The application of graphite varnish is by means of a rapid spray to about thirty centimeters of the sample.
Epaisseur des échantillons : Thickness of the samples:
[0039] La mesure de l'épaisseur de l'échantillon est vérifiée. Elle est réalisée à l'aide d'un micromètre Mitutoyo, précis à un micron près. The measurement of the thickness of the sample is verified. It is made using a Mitutoyo micrometer, accurate to a micron.
Essais de traction [0040] Ces essais de traction permettent de déterminer les modules d'élasticité et les propriétés à la rupture et sont basées sur la norme française NF T 46-002 de septembre 1988. Tensile tests [0040] These tensile tests make it possible to determine the modulus of elasticity and the properties at break and are based on the French standard NF T 46-002 of September 1988.
[0041] Un traitement des enregistrements de traction permet également de tracer la courbe de module en fonction de l'allongement. Le module utilisé ici étant le module sécant nominal (ou apparent) mesuré en première élongation, calculé en se ramenant à la section initiale de l'éprouvette. On mesure en première élongation à 23°C ± 2°C les modules sécants nominaux (ou contraintes apparentes, en MPa) à, 100% et 300% d'allongement notés respectivement MSA100 et MSA300. Le rapport MSA300/MSA100 est un paramètre indicateur pour évaluer un renforcement d'une composition de caoutchouc. Traction data processing also makes it possible to draw the modulus curve as a function of the elongation. The module used here is the nominal secant modulus (or apparent) measured in first elongation, calculated by reducing to the initial section of the specimen. The nominal secant moduli (or apparent stresses, in MPa) at 100% and 300% of elongation respectively noted MSA100 and MSA300 are measured at first elongation at 23 ° C. ± 2 ° C. The MSA300 / MSA100 ratio is an indicator parameter for evaluating a strengthening of a rubber composition.
Température de transition vitreuse Tg [0042] La température de transition vitreuse Tg est mesurée de manière connue par DSC (Differential Scanning Calorimetry), selon la norme ASTM D3418 (1999). Glass transition temperature Tg [0042] The glass transition temperature Tg is measured in a known manner by DSC (Differential Scanning Calorimetry), according to the ASTM D3418 (1999) standard.
Propriétés dynamiques [0043] La propriété dynamique tan(ô)max est mesurée sur un viscoanalyseur (Metravib V A4000), selon la norme ASTM D5992-96. On enregistre la réponse d'un échantillon de composition vulcanisée (éprouvette cylindrique de 4 mm d'épaisseur et de 400 mm2 de section), soumis à une sollicitation sinusoïdale en cisaillement simple alterné, à la fréquence de 10Hz, dans les conditions normales de température (23°C) selon la norme ASTM D 1349-99. On effectue un balayage en amplitude de déformation crête à crête de
0,1 à 50% (cycle aller), puis de 50% à 1 % (cycle retour). Le résultat exploité est le facteur de perte (tan δ). Pour le cycle retour, on indique la valeur maximale de tan δ observée (tan(ô)max). [0044] On enregistre également la réponse d'un échantillon de composition vulcanisée soumis à une sollicitation sinusoïdale en cisaillement simple alterné lors d'un balayage en température, soumis à une sollicitation sinusoïdale à contrainte imposée de 0,7 MPa et à une fréquence de 10 Hz, à une température de 60°C et on mesure le module complexe de cisaillement dynamique (G*) à 60°C. Dynamic Properties The dynamic property tan (δ) max is measured on a viscoanalyzer (Metravib V A4000), according to the ASTM D5992-96 standard. The response of a sample of vulcanized composition (cylindrical specimen 4 mm in thickness and 400 mm 2 in section), subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz, is recorded under normal conditions. temperature (23 ° C) according to ASTM D 1349-99. A peak-to-peak deformation amplitude scan is performed. 0.1 to 50% (first cycle), then 50% to 1% (return cycle). The result exploited is the loss factor (tan δ). For the return cycle, the maximum value of tan δ observed (tan (δ) max) is indicated. It also records the response of a sample of vulcanized composition subjected to a sinusoidal stress in alternating simple shear during a temperature sweep, subjected to a sinusoidal stress at imposed stress of 0.7 MPa and at a frequency of 10 Hz, at a temperature of 60 ° C and the dynamic shear complex modulus (G *) is measured at 60 ° C.
II. DESCRIPTION DETAILLEE DE L'INVENTION II. DETAILED DESCRIPTION OF THE INVENTION
[0045] L'invention concerne une composition de caoutchouc à base d'au moins un élastomère diénique, une charge renforçante et un système de vulcanisation, caractérisée en ce que la composition comprend à titre de charge renforçante du nitrure de bore hexagonal ayant une surface spécifique BET supérieure ou égale à 10m2 /g et à un taux allant de 30 à 350 parties pour cent parties d'élastomère, au moins un agent de couplage organosilicié capable de lier le nitrure de bore hexagonal à Γ élastomère diénique, ladite composition étant dépourvue d'acide gras ou ayant un taux d'acide gras strictement inférieur à 0,5 pce. The invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler and a vulcanization system, characterized in that the composition comprises, as reinforcing filler, hexagonal boron nitride having a surface area. BET specific greater than or equal to 10m 2 / g and at a rate ranging from 30 to 350 parts per hundred parts of elastomer, at least one organosilicon coupling agent capable of binding the hexagonal boron nitride to the diene elastomer, said composition being devoid of fatty acid or having a fatty acid level strictly less than 0.5 phr.
[0046] Par expression « composition à base de », on entend une composition comportant le mélange et/ou le produit de réaction in situ des différents constituants utilisés, certains de ces constituants étant susceptibles de, ou destinés à réagir entre eux, aux moins en partie, lors des différentes phases de fabrication de la composition, ou lors de la cuisson ultérieure, modifiant la composition telle qu'elle est préparée au départ. Ainsi, les compositions telles que mises en œuvre pour l'invention peuvent être différentes à l'état non réticulé et à l'état réticulé. [0047] Dans la présente description, sauf indication expresse différente, tous les pourcentages (%) indiqués sont des pourcentages en masse. By expression "composition based on" is meant a composition comprising the mixture and / or the reaction product in situ of the various constituents used, some of these constituents being capable of or intended to react with one another at least in part, during the various phases of manufacture of the composition, or during the subsequent firing, modifying the composition as it was initially prepared. Thus, the compositions as implemented for the invention may be different in the uncrosslinked state and in the crosslinked state. In the present description, unless otherwise expressly indicated, all the percentages (%) indicated are percentages by weight.
[0048] Par ailleurs, tout intervalle de valeurs désigné par l'expression « entre a et b » représente le domaine de valeurs allant de plus de « a » à moins de « b » (c'est-à-dire bornes a et b exclues) tandis que tout intervalle de valeurs désigné par l'expression « de a à b » signifie le domaine de valeurs allant de « a » jusqu'à « b » (c'est-à-dire incluant les bornes strictes a et b).
[0049] L'abréviation « pce » (pce : partie pour cent élastomère ; usuellement « phr » en anglais pour « per hundred part of rubber ») signifie parties en poids d'un constituant pour cent parties en poids d'élastomère(s) présent(s) dans la composition de caoutchouc. [0050] Par « majoritairement », « à titre majoritaire » ou « majoritaire », on entend au sens de la présente invention, un composé qui représente la plus grande quantité en masse ou en poids parmi les composés du même type. En d'autres termes, la masse de ce composé représente plus de 50 % de la masse totale des composés du même type dans la composition. A titre d'exemple, une charge renforçante dite majoritaire est la charge renforçante représentant la plus grande masse par rapport à la masse totale des charges renforçantes de la composition. En d'autres termes, la masse de cette charge renforçante représente plus de 50 % de la masse totale des charges renforçantes dans la composition. Moreover, any range of values designated by the expression "between a and b" represents the range of values from more than "a" to less than "b" (that is, terminals a and b excluded) while any range of values designated by the expression "from a to b" means the range of values from "a" to "b" (i.e. including the strict bounds a and b). The abbreviation "pce" (phr: part per cent elastomer, usually "phr" in English for "per hundred part of rubber") means parts by weight of one component per hundred parts by weight of elastomer (s). present in the rubber composition. By "majority", "majority" or "majority" means in the sense of the present invention, a compound that represents the largest amount by weight or weight among the compounds of the same type. In other words, the mass of this compound represents more than 50% of the total mass of the compounds of the same type in the composition. By way of example, a so-called majority reinforcing filler is the reinforcing filler representing the largest mass relative to the total mass of the reinforcing fillers of the composition. In other words, the mass of this reinforcing filler represents more than 50% of the total weight of the reinforcing fillers in the composition.
[0051] Par « acide gras », on entend au sens de la présente invention un acide carboxylique dont la chaîne hydrocarbonée comprend de 14 à 28 atomes de carbone, ladite chaîne étant saturée ou insaturée. For the purposes of the present invention, the term "fatty acid" means a carboxylic acid whose hydrocarbon chain comprises from 14 to 28 carbon atoms, said chain being saturated or unsaturated.
[0052] Dans le cadre de l'invention, les produits carbonés mentionnés dans la description peuvent être d'origine fossile ou biosourcée. Dans ce dernier cas, ils peuvent être, partiellement ou totalement, issus de la biomasse ou obtenus à partir de matières premières renouvelables issues de la biomasse. Sont concernés notamment les polymères, les plastifiants, les charges, etc. In the context of the invention, the carbon products mentioned in the description may be of fossil origin or biobased. In the latter case, they can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. These include polymers, plasticizers, fillers, etc.
Elastomère diénique Diene elastomer
[0053] Les compositions selon l'invention comprennent au moins un élastomère diénique. The compositions according to the invention comprise at least one diene elastomer.
[0054] Par élastomère ou caoutchouc « diénique », doit être compris de manière connue un (on entend un ou plusieurs) élastomère issu au moins en partie (i.e., un homopolymère ou un copolymère) de monomères diènes (monomères porteurs de deux doubles liaisons carbone-carbone, conjuguées ou non). By elastomer or "diene" rubber, must be understood in a known way (one means one or more) elastomer derived at least in part (ie, a homopolymer or a copolymer) of monomers dienes (monomers carrying two double bonds carbon-carbon, conjugated or not).
[0055] Ces élastomères diéniques peuvent être classés dans deux catégories : « essentiellement insaturés » ou « essentiellement saturés ». On entend en général par « essentiellement insaturé », un élastomère diénique issu au moins en partie de monomères diènes conjugués, ayant un taux de motifs ou unités d'origine diénique (diènes conjugués) qui est supérieur à 15% (% en moles) ; c'est ainsi que des élastomères
diéniques tels que les caoutchoucs butyle ou les copolymères de diènes et d'alpha- oléfmes type EPDM n'entrent pas dans la définition précédente et peuvent être notamment qualifiés d'élastomères diéniques « essentiellement saturés » (taux de motifs d'origine diénique faible ou très faible, toujours inférieur à 15%). Dans la catégorie des élastomères diéniques « essentiellement insaturés », on entend en particulier par élastomère diénique « fortement insaturé » un élastomère diénique ayant un taux de motifs d'origine diénique (diènes conjugués) qui est supérieur à 50%. These diene elastomers can be classified in two categories: "essentially unsaturated" or "essentially saturated". The term "essentially unsaturated" is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%); this is how elastomers dienes such as butyl rubbers or copolymers of dienes and alpha-olefins EPDM type do not fall within the above definition and may be particularly described as "essentially saturated" diene elastomers (low diene origin or very low, always less than 15%). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
[0056] Ces définitions étant données, on entend plus particulièrement par élastomère diénique susceptible d'être utilisé dans les compositions conformes à l'invention: These definitions being given, the term diene elastomer can be understood more particularly and may be used in the compositions according to the invention:
(a) - tout homopolymère obtenu par polymérisation d'un monomère diène conjugué ayant de 4 à 12 atomes de carbone; (a) - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;
(b) - tout copolymère obtenu par copolymérisation d'un ou plusieurs diènes conjugués entre eux ou avec un ou plusieurs composés vinyle aromatique ayant de 8 à 20 atomes de carbone; (b) - any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;
(c) - un copolymère ternaire obtenu par copolymérisation d'éthylène, d'une a-oléfme ayant 3 à 6 atomes de carbone avec un monomère diène non conjugué ayant de 6 à 12 atomes de carbone, comme par exemple les élastomères obtenus à partir d'éthylène, de propylène avec un monomère diène non conjugué du type précité tel que notamment l'hexadiène-1,4, l'éthylidène norbornène, le dicyclopentadiène; (c) - a ternary copolymer obtained by copolymerization of ethylene, an α-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, for example elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene;
(d) - un copolymère d'isobutène et d'isoprène (caoutchouc butyle), ainsi que les versions halogénées, en particulier chlorées ou bromées, de ce type de copolymère. (d) - a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.
[0057] Bien qu'elle s'applique à tout type d'élastomère diénique, l'homme du métier du pneumatique comprendra que la présente invention est de préférence mise en œuvre avec des élastomères diéniques essentiellement insaturés, en particulier du type (a) ou (b) ci-dessus. Although it applies to any type of diene elastomer, the person skilled in the art of the tire will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of the type (a) or (b) above.
[0058] A titre de diènes conjugués conviennent notamment le butadiène-1,3, le 2-méthyl- 1,3-butadiène, les 2,3-di(alkyle en Cl-C5)-l,3-butadiènes tels que par exemple le 2, 3-diméthyl- 1,3-butadiène, le 2, 3-diéthyl- 1,3-butadiène, le 2-méthyl-3-éthyl- 1,3- butadiène, le 2-méthyl-3-isopropyl- 1,3-butadiène, un aryl- 1,3-butadiène, le 1,3-pentadiène, le 2,4-hexadiène. [0059] A titre de composés vinylaromatique conviennent par exemple le styrène, l'ortho-, méta-, para-méthylstyrène, le mélange commercial « vinyle-toluène », le para- tertiobutylstyrène, les méthoxystyrènes, les chlorostyrènes, le vinylmésitylène, le divinylbenzène, le vinylnaphtalène.
[0060] Les copolymères peuvent contenir entre 99% et 20% en poids d'unités diéniques et entre 1% et 80%> en poids d'unités vinylaromatique. [0061] Les élastomères précités peuvent avoir toute microstructure qui est fonction des conditions de polymérisation utilisées, notamment de la présence ou non d'un agent modifiant et/ou randomisant et des quantités d'agent modifiant et/ou randomisant employées. Les élastomères peuvent être par exemple à blocs, statistiques, séquencés, microséquencés, et être préparés en dispersion ou en solution ; ils peuvent être couplés et/ou étoilés ou encore fonctionnalisés avec un agent de couplage et/ou d'étoilage ou de fonctionnalisation. Pour un couplage à du noir de carbone, on peut citer par exemple des groupes fonctionnels comprenant une liaison C-Sn (carbone-étain) ou des groupes fonctionnels aminés tels que aminobenzophénone par exemple. Pour un couplage à une charge inorganique renforçante telle que la silice, on peut citer par exemple des groupes fonctionnels silanol ou polysiloxane ayant une extrémité silanol (tels que décrits par exemple dans FR 2 740 778 ou US 6 013 718, et WO 2008/141702), des groupes alkoxysilane (tels que décrits par exemple dans FR 2 765 882 ou US 5 977 238), des groupes carboxyliques (tels que décrits par exemple dans WO 01/92402 ou US 6 815 473, WO 2004/096865 ou US 2006/0089445) ou encore des groupes polyéthers (tels que décrits par exemple dans EP 1 127 909 ou US 6 503 973, WO 2009/000750 et WO 2009/000752). As 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, 2-methyl-3-isopropyl 1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. As vinylaromatic compounds are suitable for example styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene. The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units. The aforementioned elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and amounts of modifying and / or randomizing agent used. The elastomers can be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization. For coupling with carbon black, there may be mentioned for example functional groups comprising a C-Sn bond (carbon-tin) or amino functional groups such as aminobenzophenone for example. For coupling to a reinforcing inorganic filler such as silica, mention may be made, for example, of silanol or polysiloxane functional groups having a silanol end (as described, for example, in FR 2 740 778 or US Pat. No. 6,013,718 and WO 2008/141702). ), alkoxysilane groups (as described for example in FR 2,765,882 or US 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US 2006 / 0089445) or polyether groups (as described for example in EP 1 127 909 or US 6,503,973, WO 2009/000750 and WO 2009/000752).
[0062] On peut aussi citer comme élastomères fonctionnels ceux préparés par l'utilisation d'un amorceur fonctionnel, notamment ceux portant une fonction aminé ou étain (voir par exemple WO 2010072761). It may also be mentioned as functional elastomers those prepared by the use of a functional initiator, especially those carrying an amine or tin function (see for example WO 2010072761).
[0063] Comme autres exemples d'élastomères fonctionnalisés, on peut citer également des élastomères (tels que SBR, BR, NR ou IR) du type époxydés. [0064] L'élastomère diénique de la composition conforme à l'invention est choisi préférentiellement dans le groupe des élastomères diéniques fortement insaturés constitué par les polybutadiènes (en abrégé BR), les polyisoprènes de synthèse (en abrégé IR), le caoutchouc naturel (en abrégé NR), les copolymères de butadiène, les copolymères d'isoprène et les mélanges de ces élastomères. De tels copolymères sont plus préférentiellement choisis dans le groupe constitué par les copolymères de butadiène- styrène (en abrégé SBR), les copolymères d'isoprène-butadiène (en abrégé BIR), les copolymères d'isoprène- styrène (en abrégé SIR) et les copolymères d'isoprène- butadiène-styrène (en abrégé SBIR).
[0065] Selon un mode de réalisation particulier, l'élastomère diénique est majoritairement (i.e., pour plus de 50 pce) un SBR, qu'il s'agisse d'un SBR préparé en émulsion (en abrégé ESBR) ou d'un SBR préparé en solution (en abrégé SSBR), ou un coupage (mélange) SBR/BR, SBR/NR (ou SBR/IR), BR/NR (ou BR/IR), ou encore SBR/BR/NR (ou SBR/BR/IR). Dans le cas d'un élastomère SBR (ESBR ou SSBR), on utilise notamment un SBR ayant une teneur en styrène moyenne, par exemple comprise entre 10% et 35%o en poids, ou une teneur en styrène élevée, par exemple de 35 à 55%, une teneur en liaisons vinyliques de la partie butadiénique comprise entre 15% et 70%>, une teneur (% molaire) en liaisons trans-1,4 comprise entre 15% et 75% et une température de transition vitreuse Tg comprise entre - 10°C et - 65°C, de préférence supérieure ou égale à -50°C. As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type. The diene elastomer of the composition according to the invention is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated as BR), synthetic polyisoprenes (abbreviated to IR), and natural rubber ( abbreviated NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (abbreviated as SBR), isoprene-butadiene copolymers (abbreviated to BIR), copolymers of isoprene-styrene (abbreviated to SIR) and copolymers of isoprene-butadiene-styrene (abbreviated as SBIR). According to a particular embodiment, the diene elastomer is predominantly (ie, for more than 50 phr) an SBR, whether it is an SBR prepared in emulsion (abbreviated to ESBR) or a SBR prepared in solution (abbreviated SSBR), or a blend (mixture) SBR / BR, SBR / NR (or SBR / IR), BR / NR (or BR / IR), or SBR / BR / NR (or SBR / BR / IR). In the case of an SBR elastomer (ESBR or SSBR), an SBR having an average styrene content, for example between 10% and 35% by weight, or a high styrene content, for example 35% by weight, is used in particular. at 55%, a vinyl content of the butadiene part of between 15% and 70%>, a content (mol%) of trans-1,4 bonds of between 15% and 75% and a glass transition temperature Tg of between -10 ° C and -65 ° C, preferably greater than or equal to -50 ° C.
[0066] Préférentiellement, l'élastomère diénique de la composition représente au moins 50%) en masse de l'ensemble des élastomères présent dans la composition ; il peut être notamment un copolymère de styrène et de butadiène. Preferably, the diene elastomer of the composition represents at least 50% by weight of all the elastomers present in the composition; it may especially be a copolymer of styrene and butadiene.
[0067] La matrice élastomérique de la composition conforme à l'invention comprend plus préférentiellement au moins un SBR avec un taux allant de 60 à 100 pce, plus préférentiellement de 80 à 100 pce. The elastomeric matrix of the composition according to the invention more preferably comprises at least one SBR with a content ranging from 60 to 100 phr, more preferably from 80 to 100 phr.
[0068] En particulier, la composition peut comprendre au moins un SBR utilisé en coupage avec du caoutchouc naturel ou un polyisoprène de synthèse qui présent avec un taux allant de 1 à 40 pce, et préférentiellement allant de 5 à 25 pce. [0069] La composition selon l'invention peut contenir un ou plusieurs élastomères synthétiques autres que diénique, voire avec des polymères autres que des élastomères, par exemple des polymères thermoplastiques. In particular, the composition may comprise at least one SBR used in a blend with natural rubber or a synthetic polyisoprene which has a content ranging from 1 to 40 phr, and preferably ranging from 5 to 25 phr. The composition according to the invention may contain one or more synthetic elastomers other than diene, or even with polymers other than elastomers, for example thermoplastic polymers.
Charge renforçante Reinforcing charge
[0070] La composition conforme à l'invention comporte au moins à titre de charge renforçante, notamment majoritaire, du nitrure de bore hexagonal. The composition according to the invention comprises at least as reinforcing filler, in particular majority, hexagonal boron nitride.
[0071] Le nitrure de bore est un composé chimique comprenant du bore et de l'azote de formule chimique brute BN. Le nitrure de bore existe sous plusieurs structures cristallines, dont la structure hexagonale (h-BN). Boron nitride is a chemical compound comprising boron and nitrogen of crude chemical formula BN. Boron nitride exists under several crystalline structures, including the hexagonal structure (h-BN).
[0072] Le nitrure de bore hexagonal (h-BN) utilisé à titre de charge dans les compositions conforme à l'invention se présente sous forme de particules. Seront considérées comme équivalentes dans la description suivante les expressions
« particule(s) de nitrure de bore hexagonal », « nitrure(s) de bore hexagonal », « h-BN » et « hBN ». The hexagonal boron nitride (h-BN) used as a filler in the compositions according to the invention is in the form of particles. Will be considered equivalent in the following description expressions "Hexagonal boron nitride particle (s)", "hexagonal boron nitride (s)", "h-BN" and "hBN".
[0073] De manière préférée, le h-BN se présente sous la forme de particules, notamment de taille moyenne nano métrique, c'est-à-dire une taille moyenne strictement inférieure à 1 micromètre. Plus particulièrement, le h-BN est choisi avec une taille moyenne inférieure ou égale à 500 nanomètre. De préférence, la taille moyenne des particules de h-BN va de 1 à 500 nm, de préférence de 5 à 350 nm et encore plus préférentiellement de 10 à 250 nm. Preferably, the h-BN is in the form of particles, in particular of medium size nano metric, that is to say, an average size strictly less than 1 micrometer. More particularly, the h-BN is chosen with an average size of less than or equal to 500 nanometers. Preferably, the mean size of the h-BN particles ranges from 1 to 500 nm, preferably from 5 to 350 nm and even more preferably from 10 to 250 nm.
[0074] Conviennent pour l'invention des nitrures de bore hexagonal dont la surface spécifique BET est supérieure ou égale à 10 m2/g, de préférence supérieure ou égale à 15 m2/g et encore plus préférentiellement supérieure ou égale à 20 m2/g. [0075] On peut citer comme nitrure de bore h-BN convenant à l'invention, les nitrures de bore hexagonal commercialisés par la société MK Impex Corp. sous le nom commercial « MK-hBN-N70» présentant une surface spécifique BET de 25 m2/g et une taille moyenne de particules égale à 70 nm et « MK-hBN-050 » présentant une surface spécifique BET de 20 m2/g et une taille moyenne de particules égale à 500 nm. On peut également citer les nitrures de bore hexagonal commercialisés, par la société ESK Ceramics GmbH&Co sous le nom commercial « Boronid SCPI ». Suitable for the invention are hexagonal boron nitrides whose BET specific surface area is greater than or equal to 10 m 2 / g, preferably greater than or equal to 15 m 2 / g and even more preferably greater than or equal to 20 m 2 / g. As boron nitride h-BN suitable for the invention, hexagonal boron nitrides sold by MK Impex Corp. may be mentioned. under the trade name "MK-hBN-N70" having a BET surface area of 25 m 2 / g and an average particle size of 70 nm and "MK-hBN-050" having a BET specific surface area of 20 m 2 / g and an average particle size of 500 nm. Mention may also be made of hexagonal boron nitrides marketed by ESK Ceramics GmbH & Co under the trade name "Boronid SCPI".
[0076] Préférentiellement, le taux de nitrure de bore hexagonal dans la composition peut aller de 60 à 250 pce. Preferably, the level of hexagonal boron nitride in the composition may range from 60 to 250 phr.
[0077] Selon un mode de réalisation, le nitrure de bore hexagonal peut être utilisé en coupage avec d'autres charges, notamment avec une charge organique et/ou une charge inorganique renforçante. [0078] A titre de charge organique, conviennent particulièrement les noirs de carbone, notamment les noirs de carbone renforçants des séries 100, 200 ou 300 (grades ASTM), comme par exemple les noirs NI 15, N134, N234, N326, N330, N339, N347, N375, ou encore, selon les applications visées, les noirs de séries plus élevées (par exemple N400, N660, N683, N772). According to one embodiment, the hexagonal boron nitride may be used in blending with other fillers, in particular with an organic filler and / or a reinforcing inorganic filler. As an organic filler, carbon blacks are particularly suitable, in particular reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N400, N660, N683, N772).
[0079] Par « charge inorganique renforçante », doit être entendu ici, de manière connue, toute charge inorganique ou minérale, quelles que soient sa couleur et son origine (naturelle ou de synthèse), encore appelée charge « blanche », charge « claire » ou encore charge « non-noire » (« non-black fîller ») par opposition au noir de carbone, cette charge inorganique étant capable de renforcer à elle seule, sans autre moyen qu'un agent de
couplage intermédiaire, une composition de caoutchouc destinée à la fabrication d'une bande de roulement de pneumatiques, en d'autres termes apte à remplacer, dans sa fonction de renforcement, un noir de carbone conventionnel de grade pneumatique pour bande de roulement. Une telle charge se caractérise généralement par la présence de groupes fonctionnels, notamment hydroxyle (-OH), à sa surface, nécessitant en cela l'emploi d'un agent ou système de couplage destiné à assurer une liaison chimique stable entre l'élastomère isoprénique et ladite charge. By "reinforcing inorganic filler" must be understood here, in known manner, any inorganic or mineral filler, regardless of its color and origin (natural or synthetic), also called "white" charge, "clear" charge "Or" non-black "charge (" non-black fi ller ") as opposed to carbon black, this inorganic filler being able to reinforce on its own, without any other means than an agent of intermediate coupling, a rubber composition for the manufacture of a tire tread, in other words able to replace, in its reinforcing function, a conventional tire grade carbon black for tread. Such a filler is generally characterized by the presence of functional groups, in particular hydroxyl (-OH), at its surface, thereby requiring the use of an agent or coupling system intended to ensure a stable chemical bond between the isoprene elastomer and said charge.
[0080] Préférentiellement, la charge inorganique renforçante est une charge du type silice ou alumine, silice-alumine, oxyde de titane ou un mélange de ces types de charges. Preferably, the reinforcing inorganic filler is a filler of the silica or alumina type, silica-alumina, titanium oxide or a mixture of these types of fillers.
[0081] La silice (Si02) utilisée peut être toute silice renforçante connue de l'homme du métier, notamment toute silice précipitée ou pyrogénée, présentant une surface spécifique BET ainsi qu'une surface spécifique CTAB toutes deux inférieures à 450 m2/g, de préférence de 30 à 400 m2/g. The silica (SiO 2 ) used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica, having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g.
[0082] Préférentiellement, lorsque le nitrure de bore hexagonal est utilisé en coupage avec une autre charge renforçante, cette autre charge renforçante est présente dans la composition avec un taux inférieur ou égal à 30 pce. Preferably, when the hexagonal boron nitride is used in a blend with another reinforcing filler, this other reinforcing filler is present in the composition with a content of less than or equal to 30 phr.
[0083] De préférence, le taux de charge renforçante total va de 30 à 350 pce, de préférence de 50 à 300 pce, plus préférentiellement encore de 60 à 250 pce. Preferably, the total reinforcing filler content ranges from 30 to 350 phr, preferably from 50 to 300 phr, more preferably from 60 to 250 phr.
[0084] Préférentiellement, le nitrure de bore hexagonal est la charge renforçante majoritaire de la composition. Preferably, the hexagonal boron nitride is the majority reinforcing filler of the composition.
[0085] Préférentiellement, le nitrure de bore hexagonal est la seule charge renforçante dans la composition de l'invention. [0086] A la charge renforçante précédemment décrite, peuvent être également ajoutés, en fonction de l'application visée, des charges inertes (i.e. non renforçantes) telles que particules d'argile, bentonite, talc, craie, kaolin avec un taux inférieur ou égal à 10 pce et préférentiellement inférieur ou égal à 5 pce. Agent de couplage Preferably, the hexagonal boron nitride is the only reinforcing filler in the composition of the invention. The reinforcing filler described above can also be added, according to the intended application, inert fillers (ie non-reinforcing) such as clay particles, bentonite, talc, chalk, kaolin with a lower rate or equal to 10 phr and preferably less than or equal to 5 phr. Coupling agent
[0087] La composition conforme à l'invention comprend au moins un agent de couplage organosilicié capable de lier le nitrure de bore hexagonal à l'élastomère diénique. The composition according to the invention comprises at least one organosilicon coupling agent capable of binding the hexagonal boron nitride to the diene elastomer.
[0088] Par « agent de couplage », encore appelé agent de liaison, on entend un composé chimique qui a pour fonction d'assurer la liaison entre la surface des particules de
charges inorganiques, notamment les particules de nitrure du bore hexagonal, et l'élastomère diénique, tout en facilitant la dispersion de cette charge inorganique au sein de la matrice élastomérique. [0089] On rappelle ici que par « agent de couplage », on doit entendre de manière connue, un agent apte à établir une liaison suffisante, de nature chimique et/ou physique, entre le nitrure de bore hexagonal utilisé comme charge inorganique, et l'élastomère diénique ; un tel agent de couplage, au moins bifonctionnel, a par exemple comme formule générale simplifiée « Y -W -T » dans laquelle : By "coupling agent", also called binding agent is meant a chemical compound whose function is to ensure the connection between the surface of the particles of inorganic fillers, in particular hexagonal boron nitride particles, and the diene elastomer, while facilitating the dispersion of this inorganic filler within the elastomeric matrix. It is recalled here that "coupling agent" must be understood in a known manner, an agent capable of establishing a sufficient bond, chemical and / or physical, between the hexagonal boron nitride used as inorganic filler, and the diene elastomer; such a coupling agent, at least bifunctional, has for example as simplified general formula "Y -W-T" in which:
- Y représente un groupe fonctionnel (fonction « Y ») qui est capable de se lier physiquement et/ou chimiquement au nitrure de bore hexagonal utilisé à titre de charge renforçante; Y represents a functional group ("Y" function) which is capable of binding physically and / or chemically to the hexagonal boron nitride used as a reinforcing filler;
T représente un groupe fonctionnel (fonction « T ») capable de se lier physiquement et/ou chimiquement à l'élastomère diénique, par exemple par l'intermédiaire d'un atome de soufre. T represents a functional group ("T" function) capable of binding physically and / or chemically to the diene elastomer, for example via a sulfur atom.
W représente un groupe divalent permettant de relier Y et T. W represents a divalent group making it possible to connect Y and T.
[0090] Les agents de couplage ne doivent en particulier pas être confondus avec de simples agents de recouvrement de charges inorganiques qui, de manière connue, peuvent comporter la fonction Y réactive vis-à-vis de la charge inorganique mais sont dépourvus de la fonction T active vis-à-vis de l'élastomère diénique. In particular, the coupling agents must not be confused with simple inorganic charge-covering agents which, in known manner, may comprise the reactive Y function with respect to the inorganic filler but lack the function. T active vis-à-vis the diene elastomer.
[0091] Par composé « organosilicié » (« organosilicon compound » en anglais), on entend un composé organique renfermant au moins une liaison carbone-silicium. By "organosilicon" compound ("organosilicon compound" in English) is meant an organic compound containing at least one carbon-silicon bond.
[0092] L'agent de couplage utilisé dans les compositions de la présente invention est donc un composé organosilicié assurant une liaison entre l'élastomère diénique et le nitrure de bore hexagonal. La fonction qui est destinée à assurer la liaison avec le nitrure de bore hexagonal est assurée par un groupe silylé, c'est-à-dire par le groupe porteur de l'atome de silicium. Le groupe silylé comprend au moins un groupe hydrolysable tel qu'un hydroxyl, un alkoxy. The coupling agent used in the compositions of the present invention is an organosilicon compound providing a bond between the diene elastomer and the hexagonal boron nitride. The function which is intended to ensure the bond with the hexagonal boron nitride is provided by a silylated group, that is to say by the silicon atom carrier group. The silyl group comprises at least one hydrolyzable group such as a hydroxyl, an alkoxy.
[0093] A titre de composés organosiliciés utilisés comme agents de couplage conviennent notamment, les silanes polysulfures, les silanes porteurs de groupements fonctionnels azodicarbonyle, les silanes porteurs d'au moins une fonction thiol, les silanes porteurs d'au moins une fonction thiol bloqué et les polyorganosiloxanes. As organosilicon compounds used as coupling agents are especially suitable polysulfide silanes, silanes carrying azodicarbonyl functional groups, silanes carrying at least one thiol function, silanes carrying at least one blocked thiol function. and polyorganosiloxanes.
[0094] Parmi les silanes polysulfures, conviennent notamment, les alkoxysilanes polysulfurés et les polysulfures d'hydoxysilane, symétriques ou asymétriques.
[0095] On utilise notamment des silanes polysulfurés, dits "symétriques" ou "asymétriques" selon leur structure particulière, tels que décrits par exemple dans les demandes WO03/002648 (ou US 2005/016651) et WO03/002649 (ou US 2005/016650). [0096] Conviennent en particulier, sans que la définition ci-après soit limitative, des silanes polysulfurés répondant à la formule générale (I) suivante:Among the polysulfide silanes, the polysulfurized alkoxysilanes and the symmetrical or asymmetric hydoxysilane polysulfides are particularly suitable. In particular, polysulfide silanes, called "symmetrical" or "asymmetrical" silanes, are used according to their particular structure, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005 / 016650). In particular, polysulphide silanes corresponding to the following general formula (I) are, in particular, but not limited to the following definition:
dans laquelle: in which:
x est un nombre entier ou fractionnaire supérieur ou égal à 2 ; de préférence de x est un nombre entier ou fractionnaire supérieur allant de 2 à 8 ; x is an integer or fractional number greater than or equal to 2; preferably, x is an integer or fractional number greater than 2 to 8;
les symboles Ai, A2, identiques ou différents, représentent un radical hydrocarboné divalent (de préférence un groupement alkylène en Ci -Ci s ou un groupement arylène en C6-C12, plus particulièrement un alkylène en Ci-Cio, notamment en un alkylène C1-C4, en particulier le propylène) ; the symbols A 1 , A 2 , which are identical or different, represent a divalent hydrocarbon radical (preferably a C 1 -C 18 alkylene group or a C 6 -C 12 arylene group, more particularly a C 1 -C 10 alkylene group, in particular a C1-C4 alkylene, especially propylene);
- les symboles Zl s Z2, identiques ou différents, répondent à l'une des trois formules ci-après: - Z ls symbols Z 2, identical or different, correspond to one of the three following formulas:
R1 R1 R2 R1 R1 R2
—Si— R1 ; — Si— R2 ; — Si— R2 , -Si-R1; - Si- R2; - Si- R2,
R2 R2 R2 R2 R2 R2
dans lesquelles: in which:
- les radicaux R1, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkyle en Ci-Cis, un cycloalkyle en C5-C18 ou un aryle en C6-Ci8 (de préférence des groupes alkyle en Ci-C6, un cyclohexyle ou un phényle, notamment des groupes alkyle en C1-C4, plus particulièrement le méthyle et/ou l'éthyle). the radicals R 1 , which may be substituted or unsubstituted, which are identical to or different from one another, represent a C 1 -C 18 alkyl group, a C 5 -C 18 cycloalkyl or a C 6 -C 18 aryl ring (preferably C 1 -C 8 alkyl groups); 6 , cyclohexyl or phenyl, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl).
- les radicaux R2, substitués ou non substitués, identiques ou différents entre eux, représentent un hydroxyle, un groupe alkoxyle en Ci-Cis ou un cycloalkoxyle en C5-C18 (de préférence un groupe choisi parmi des alkoxyles en Ci-Cs et des cycloalkoxyles en Cs-Cs, plus préférentiellement encore un groupe choisi parmi des alkoxyles en C1-C4, en particulier le méthoxyle et l'éthoxyle). the radicals R 2 , substituted or unsubstituted, which are identical to or different from each other, represent a hydroxyl, a C 1 -C 18 alkoxyl group or a C 5 -C 18 cycloalkoxyl (preferably a group chosen from C 1 -C 6 alkoxyls) and C 6 -C 8 cycloalkoxyls, more preferably still a group selected from C 1 -C 4 alkoxyls, in particular methoxyl and ethoxyl).
[0097] Dans le cas d'un mélange d'alkoxysilanes polysulfurés répondant à la formule (I) ci-dessus, notamment des mélanges usuels disponibles commercialement, la valeur moyenne des "x" est un nombre fractionnaire de préférence compris entre 2 et 5, plus préférentiellement proche de 4. Mais l'invention peut être aussi avantageusement mise en œuvre par exemple avec des alkoxysilanes disulfurés (x = 2).
[0098] A titre d'exemples de silanes polysulfurés, on citera plus particulièrement les polysulfures (notamment disulfures, trisulfures ou tétrasulfures) de bis-(alkoxyl(Ci-C4)- alkyl(Ci-C4)silyl-alkyl(Ci-C4)), comme par exemple les polysulfures de bis(3-triméthoxysilylpropyl) ou de bis(3-triéthoxysilylpropyl). Parmi ces composés, on utilise en particulier le tétrasulfure de bis(3-triéthoxysilylpropyl), en abrégé TESPT, de formule [(C2H50)3Si(CH2)3S2]2 ou le disulfure de bis-(triéthoxysilylpropyle), en abrégé TESPD, de formule [(C2H50)3Si(CH2)3S]2. On citera également à titre d'exemples préférentiels les polysulfures (notamment disulfures, trisulfures ou tétrasulfures) de bis-(monoalkoxyl(Ci-C4)-dialkyl(Ci-C4)silylpropyl), plus particulièrement le tétrasulfure de bis-monoéthoxydiméthylsilylpropyl tel que décrit dans la demande de brevet WO 02/083782 précitée (ou US 7 217 751). In the case of a mixture of polysulfurized alkoxysilanes corresponding to the formula (I) above, in particular common commercially available mixtures, the average value of the "x" is a fractional number preferably between 2 and 5. more preferably close to 4. However, the invention can also be advantageously used for example with disulfide alkoxysilanes (x = 2). As examples of polysulphurized silanes, mention may be made more particularly of polysulfides (in particular disulphides, trisulphides or tetrasulphides) of bis- (C 1 -C 4 ) alkoxyl-C 1 -C 4 alkylsilyl-alkyl (C 1 -C 4 ) C4)), such as, for example, bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides. Among these compounds, particular uses of the bis (3-triethoxysilylpropyl), abbreviated TESPT, of formula [(C 2 H 5 0) 3 Si (CH 2) 3S2] 2 or the bis- (triethoxysilylpropyl), abbreviated TESPD, of formula [(C 2 H 5 O) 3 Si (CH 2) 3 S] 2. Mention may also be made, by way of preferred examples, of polysulfides (in particular disulphides, trisulphides or tetrasulfides) of bis- (monoalkoxyl (Ci-C 4 ) -dialkyl (Ci-C 4 ) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide. as described in the aforementioned patent application WO 02/083782 (or US Pat. No. 7,217,751).
[0099] A titre d'exemple d'agents de couplage autres qu'un alkoxysilane polysulfuré, on citera notamment des POS (polyorganosiloxanes) bifonctionnels ou encore des polysulfures d'hydroxysilane (R2 = OH dans la formule (I) ci-dessus) tels que décrits par exemple dans les demandes de brevet WO 02/30939 (ou US 6 774 255), WO 02/31041 (ou US 2004/051210), et WO2007/061550, ou encore des silanes ou POS porteurs de groupements fonctionnels azo-dicarbonyle, tels que décrits par exemple dans les demandes de brevet WO 2006/125532, WO 2006/125533, WO 2006/125534. By way of example of coupling agents other than a polysulfurized alkoxysilane, mention may be made in particular of bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides (R 2 = OH in formula (I) above ) as described for example in the patent applications WO 02/30939 (or US Pat. No. 6,774,255), WO 02/31041 (or US 2004/051210), and WO2007 / 061550, or also silanes or POS bearing functional groups azo-dicarbonyl, as described for example in patent applications WO 2006/125532, WO 2006/125533, WO 2006/125534.
[00100] A titre d'exemples d'autres silanes sulfurés, on citera par exemple les silanes porteurs d'au moins une fonction thiol (-SH) (dits mercaptosilanes) et/ou d'au moins une fonction thiol bloqué, tels que décrits par exemple dans les brevets ou demandes de brevet US 6 849 754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2010/072685 et WO 2008/055986. By way of examples of other sulphurized silanes, mention may be made, for example, of silanes bearing at least one thiol function (-SH) (called mercaptosilanes) and / or of at least one blocked thiol function, such as described for example in the patents or patent applications US 6,849,754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2010/072685 and WO 2008/055986.
[00101] Bien entendu pourraient être également utilisés des mélanges des agents de couplage précédemment décrits, comme décrit notamment dans la demande WO 2006/125534 précitée. Of course, it would also be possible to use mixtures of the coupling agents described above, as described in particular in the aforementioned application WO 2006/125534.
[00102] Le taux d'agent de couplage utilisé dans la composition conforme à l'invention est avantageusement inférieur à 20 pce. Typiquement le taux d'agent de couplage représente de 0,05% à 10% massique par rapport à la masse de nitrure de bore hexagonal, de préférence de 0, 1 à 7% massique et encore plus préférentiellement de 0,2 à 5% massique. The amount of coupling agent used in the composition according to the invention is advantageously less than 20 phr. Typically, the level of coupling agent represents from 0.05% to 10% by mass relative to the mass of hexagonal boron nitride, preferably from 0.1 to 7% by weight and even more preferably from 0.2 to 5% by weight. mass.
Système plastifiant
[00103] Les compositions de caoutchouc de l'invention peuvent comprendre en outre au moins un système plastifiant. Le système plastifiant peut être constitué notamment d'une huile plastifiante et/ ou d'une résine plastifiante et de leurs mélanges. [00104] Ainsi, les compositions de l'invention peuvent comprendre par exemple une huile d'extension (ou huile plastifiante) et ou une résine plastifiantes ou leurs mélange dont la fonction habituelle est de faciliter la mise en œuvre, par un abaissement de la plasticité Mooney. [00105] A température ambiante (23°C), ces huiles plastifiantes, plus ou moins visqueuses, sont des liquides (c'est-à-dire, pour rappel, des substances ayant la capacité de prendre à terme la forme de leur contenant), par opposition notamment à des résines ou des caoutchoucs qui sont par nature solides. [00106] De préférence, l'huile d'extension est choisie dans le groupe constitué par les huiles polyoléfïniques (c'est-à-dire issues de la polymérisation d'o lé fines, monooléfïnes ou dioléfmes), les huiles paraffïniques, les huiles naphténiques (à basse ou haute viscosité), les huiles aromatiques, les huiles minérales, et les mélanges de ces huiles. Plasticizing system The rubber compositions of the invention may further comprise at least one plasticizer system. The plasticizer system may consist in particular of a plasticizing oil and / or a plasticizing resin and mixtures thereof. Thus, the compositions of the invention may comprise, for example, an extender oil (or plasticizing oil) and or a plasticizing resin or their mixture, the usual function of which is to facilitate the implementation, by a lowering of the Mooney plasticity. At room temperature (23 ° C), these plasticizing oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the ability to eventually take the form of their container. ), in contrast to resins or rubbers which are inherently solid. [00106] Preferably, the extender oil is chosen from the group consisting of polyolefinic oils (that is to say derived from the polymerization of oils, monoolefins or diolefins), paraffinic oils, naphthenic oils (low or high viscosity), aromatic oils, mineral oils, and mixtures of these oils.
[00107] Par ailleurs, de manière connue de l'homme du métier, la dénomination « résine plastifiante » est réservée dans la présente demande, par définition, à un composé qui est d'une part solide à température ambiante (23°C) (par opposition à un composé plastifiant liquide tel qu'une huile), d'autre part compatible (c'est-à-dire miscible au taux utilisé, typiquement supérieur à 5 pce) avec la composition de caoutchouc à laquelle il est destiné, de manière à agir comme un véritable agent diluant. Furthermore, in a manner known to those skilled in the art, the term "plasticizing resin" is reserved in this application, by definition, to a compound which is solid on the one hand at room temperature (23 ° C.). (As opposed to a liquid plasticizer such as an oil), on the other hand compatible (that is to say miscible at the rate used, typically greater than 5 phr) with the rubber composition for which it is intended, so as to act as a true diluting agent.
[00108] Elles ont été largement décrites dans les brevets ou demandes de brevet cités en introduction du présent mémoire, ainsi que par exemple dans l'ouvrage intitulé « Hydrocarbon Resins » de R. Mildenberg, M. Zander et G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) dont le chapitre 5 est consacré à leurs applications, notamment en caoutchouterie pneumatique (5.5. « Rubber Tires and Mechanical Goods »). [00109] Elles peuvent être aliphatiques, naphténiques, aromatiques ou encore du type aliphatique/ naphténique/ aromatique c'est-à-dire à base de monomères aliphatiques et/ou naphténiques et/ou aromatiques. Elles peuvent être naturelles ou synthétiques, à base ou non de pétrole (si tel est le cas, connues aussi sous le nom de résines de pétrole). Elles sont préférentiellement exclusivement hydrocarbonées, c'est-à-dire qu'elles ne comportent que des atomes de carbone et d'hydrogène.
[00110] Préférentiellement, le taux de système plastifiant va de 5 à 150 pce, de préférence de 10 à 130 pce et encore plus préférentiellement compris entre 20 à 100 pce, [00111] Préférentiellement, l'invention concerne une composition telle que définie ci-dessus dans laquelle le système plastifiant comprend majoritairement une résine plastifiante ayant une température de transition vitreuse Tg supérieure ou égale 20°C. [00108] They have been widely described in the patents or patent applications cited in the introduction to this memo, as well as for example in the book entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York , VCH, 1997, ISBN 3-527-28617-9), chapter 5 of which is devoted to their applications, in particular pneumatic rubber (5.5 Rubber Tires and Mechanical Goods). They can be aliphatic, naphthenic, aromatic or aliphatic / naphthenic / aromatic type that is to say based on aliphatic and / or naphthenic monomers and / or aromatic. They may be natural or synthetic, whether or not based on petroleum (if so, also known as petroleum resins). They are preferably exclusively hydrocarbon-based, that is to say they contain only carbon and hydrogen atoms. Preferably, the level of plasticizer system ranges from 5 to 150 phr, preferably from 10 to 130 phr, and even more preferably between 20 to 100 phr. Preferably, the invention relates to a composition as defined herein. above in which the plasticizer system mainly comprises a plasticizing resin having a glass transition temperature Tg greater than or equal to 20 ° C.
Système de vulcanisation Vulcanization system
[00112] Le système de vulcanisation est un système à base de soufre ou d'un agent donneur de soufre et d'un accélérateur primaire de vulcanisation. A ce système de vulcanisation de base viennent s'ajouter, incorporés au cours de la première phase non- productive et/ou au cours de la phase productive telles que décrites ultérieurement, divers accélérateurs secondaires ou activateurs de vulcanisation connus tels qu'oxyde de zinc, dérivés guanidiques (en particulier diphénylguanidine). The vulcanization system is a system based on sulfur or a sulfur donor agent and a primary vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the productive phase as described later, various known secondary accelerators or vulcanization activators such as zinc oxide. guanidine derivatives (in particular diphenylguanidine).
[00113] On peut utiliser comme accélérateur (primaire ou secondaire) tout composé susceptible d'agir comme accélérateur de vulcanisation des élastomères diéniques en présence de soufre, notamment des accélérateurs du type thiazoles ainsi que leurs dérivés, des accélérateurs de types thiurames, dithiocarbamates de zinc. Ces accélérateurs sont par exemple choisis dans le groupe constitué par disulfure de 2- mercaptobenzothiazyle (en abrégé « MBTS »), disulfure de tetrabenzylthiurame (« TBZTD »), N-cyclohexyl-2-benzothiazyle sulfénamide (« CBS »), N,N-dicyclohexyl- 2-benzothiazyle sulfénamide (« DCBS »), N-ter-butyl-2-benzothiazyle sulfénamide (« TBBS »), N-ter-butyl-2-benzothiazyle sulfénimide (« TBSI »), dibenzyldithiocarbamate de zinc (« ZBEC ») et les mélanges de ces composés. It is possible to use as accelerator (primary or secondary) any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type accelerators and their derivatives, accelerators of thiuram type, dithiocarbamates of zinc. These accelerators are for example selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), tetrabenzylthiuram disulfide ("TBZTD"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N, N dicyclohexyl-2-benzothiazyl sulphenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulphenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulphenimide ("TBSI"), zinc dibenzyldithiocarbamate (" ZBEC ") and mixtures of these compounds.
[00114] Le soufre est utilisé à un taux préférentiel compris entre 0,5 et 12 pce, en particulier entre 1 et 10 pce. Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr.
[00115] L'accélérateur primaire de vulcanisation, tel que par exemple l'oxyde de zinc, est utilisé à un taux préférentiel compris entre 0,5 et 10 pce, plus préférentiellement compris entre 0,5 et 5,0 pce. The primary vulcanization accelerator, such as, for example, zinc oxide, is used at a preferred level of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.
[00116] Selon une variante de réalisation de l'invention, la composition de l'invention est dépourvue d'acide gras.
[00117] Par « acide gras », on entend au sens de la présente invention un acide carboxylique dont la chaîne hydrocarbonée comprend de 14 à 28 atomes de carbone, ladite chaîne étant saturée ou insaturée. [00118] Selon une variante de réalisation de l'invention, le taux d'acides gras dans la composition est strictement inférieur à 0,5 pce. Plus préférentiellement, le taux d'acide gras est strictement ou égal à 0,3 pce, encore plus préférentiellement, le taux d'acide gras va de 0 à 0,3 pce. [00119] Préférentiellement, lorsque la composition de l'invention n'est pas dépourvue d'acide gras, l'acide gras est un acide carboxylique dont la chaîne carbonée comprenant 16 à 20 atomes de carbone ; plus préférentiellement encore, l'acide gras est l'acide stéarique. Additifs divers According to one embodiment of the invention, the composition of the invention is devoid of fatty acid. For the purposes of the present invention, the term "fatty acid" means a carboxylic acid whose hydrocarbon chain comprises from 14 to 28 carbon atoms, said chain being saturated or unsaturated. According to one embodiment of the invention, the level of fatty acids in the composition is strictly less than 0.5 phr. More preferably, the level of fatty acid is strictly or equal to 0.3 phr, more preferably, the level of fatty acid is from 0 to 0.3 phr. [00119] Preferably, when the composition of the invention is not free of fatty acid, the fatty acid is a carboxylic acid whose carbon chain comprises 16 to 20 carbon atoms; more preferably still, the fatty acid is stearic acid. Various additives
[00120] Les compositions de caoutchouc conformes à l'invention peuvent comporter également tout ou partie des additifs usuels habituellement utilisés dans les compositions d'élastomères destinées à la fabrication de pneumatiques, en particulier de bandes de roulement, comme par exemple des agents de protection tels que cires antiozone, anti-ozonants chimiques, anti-oxydants, des agents anti-fatigue, des résines tackifïantes, des agents de mise en œuvre tels que décrits par exemple dans la demande WO 02/10269. Fabrication des compositions de caoutchouc The rubber compositions in accordance with the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, in particular treads, such as, for example, protective agents. such as antiozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents, tackifying resins, processing agents as described for example in the application WO 02/10269. Manufacture of rubber compositions
[00121] Les compositions de caoutchouc de l'invention sont fabriquées dans des mélangeurs appropriés, en utilisant deux phases de préparation successives selon une procédure générale bien connue de l'homme du métier : une première phase de travail ou malaxage thermo -mécanique (parfois qualifiée de phase « non-productive ») à haute température, jusqu'à une température maximale comprise entre 130°C et 200°C, de préférence entre 145°C et 185°C, suivie d'une seconde phase de travail mécanique (parfois qualifiée de phase « productive ») à plus basse température, typiquement inférieure à 120°C, par exemple entre 23°C et 100°C, phase de finition au cours de laquelle est incorporé le système de vulcanisation. The rubber compositions of the invention are manufactured in appropriate mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first phase of work or thermo-mechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second phase of mechanical work ( sometimes referred to as a "productive" phase) at a lower temperature, typically less than 120 ° C., for example between 23 ° C. and 100 ° C., a finishing phase during which the vulcanization system is incorporated.
[00122] Bien entendu, les compositions conformes à l'invention peuvent être utilisées seules ou en coupage (i.e. mélange) avec toute autre composition de caoutchouc utilisable pour la fabrication de produits semi-finis et de pneumatiques.
[00123] Il va de soi que l'invention concerne les compositions de caoutchouc précédemment décrites tant à l'état « cru » ou non réticulée (i.e. avant cuisson) qu'à l'état dit « cuit » ou réticulé, ou encore vulcanisé (i.e. après vulcanisation). [00124] Les compositions de l'invention sont bien adaptées pour la fabrication de produits semi-finis et finis pour des pneumatiques, notamment pour des pneumatiques destinés à équiper les véhicules sans moteur tels que les bicyclettes, les véhicules à moteur de type tourisme, les SUV (Sport Utility Vehicles), les deux roues (notamment les motos), les avions, les véhicules industriels choisis parmi les camionnettes, les poids- lourds (c'est-à-dire le métro, les bus, les engin routiers (camions et remorques)), les véhicules hors la route, tels que les engins agricoles ou de génie civil, les autres véhicules de transports ou de manutention. Of course, the compositions according to the invention can be used alone or in a blend (ie mixture) with any other rubber composition used for the manufacture of semi-finished products and tires. It goes without saying that the invention relates to the rubber compositions described above both in the "raw" or uncrosslinked state (ie before firing) in the so-called "cooked" or crosslinked state, or vulcanized state. (ie after vulcanization). The compositions of the invention are well suited for the manufacture of semi-finished and finished products for tires, especially for tires intended to equip non-motorized vehicles such as bicycles, motor vehicles of the tourism type, SUVs (Sport Utility Vehicles), two-wheelers (especially motorcycles), airplanes, industrial vehicles chosen from light-duty trucks, heavy goods vehicles (ie subway, buses, road trucks and trailers), off-road vehicles, such as agricultural or engineering machinery, other transport or handling vehicles.
Article semi-fini et pneumatique Semi-finished and pneumatic article
[00125] Un autre objet de la présente invention concerne un article semi-fini comprenant au moins une composition de caoutchouc réticulable ou réticulé telle que définie ci-dessus ou susceptible d'être obtenue par le procédé décrit ci-dessus. [00126] Un produit semi-fini est un produit en caoutchouc destiné à la fabrication de pneumatique. Ce peut être tout type bande de gommes, telle que notamment des bandes de roulement, des nappes d'armature de sommet (par exemple des nappes de travail, des nappes de protection ou des nappes de frettage), de nappes d'armature de carcasse, des nappes de flancs, des nappes de bourrelets, des nappes de protecteurs, des nappes de sous-couches, des nappes de blocs de caoutchouc et autres nappes assurant l'interface entre les zones précitées des pneumatiques. De préférence, l'article semi-fini est une bande de roulement. Another object of the present invention relates to a semi-finished article comprising at least one crosslinkable or crosslinked rubber composition as defined above or obtainable by the method described above. [00126] A semi-finished product is a rubber product intended for the manufacture of a tire. This may be any type of rubber strip, such as in particular treads, crown reinforcement plies (for example working plies, protective plies or hooping plies), carcass reinforcement plies. , flank plies, bead plies, plies of protectors, plies of underlays, plies of rubber blocks and other plies providing the interface between the aforementioned zones of the tires. Preferably, the semi-finished article is a tread.
[00127] L'invention a également pour objet un pneumatique comprenant au moins un article semi-fini tel que mentionné ci-dessus ou comprenant au moins une composition telle que définie ci-dessus. The invention also relates to a tire comprising at least one semi-finished article as mentioned above or comprising at least one composition as defined above.
[00128] Le pneumatique selon l'invention peut être destiné à équiper notamment les véhicules sans moteur tels que les bicyclettes, les véhicules à moteur de type tourisme, les SUV (Sport Utility Vehicles), les deux roues (notamment les motos), les avions, les véhicules industriels choisis parmi les camionnettes, les poids-lourds (c'est-à- dire le métro, les bus, les engin routiers (camions et remorques)), les véhicules hors la route, tels que les engins agricoles ou de génie civil, les autres véhicules de transports ou de manutention.
III- EXEMPLES DE REALISATION DE L'INVENTION The tire according to the invention may be intended to equip including non-motorized vehicles such as bicycles, tourism-type motor vehicles, SUV (Sport Utility Vehicles), two wheels (including motorcycles), aircraft, industrial vehicles chosen from vans, heavy goods vehicles (ie subway, buses, road machinery (trucks and trailers)), off-road vehicles, such as agricultural machinery or civil engineering, other transport or handling vehicles. III-EXAMPLES OF CARRYING OUT THE INVENTION
[00129] Les exemples qui suivent permettent d'illustrer l'invention, cette dernière ne saurait cependant être limitée à ces seuls exemples. The following examples illustrate the invention, the latter can not however be limited to these examples only.
Préparation des compositions de caoutchouc Preparation of rubber compositions
[00130] On procède pour les essais qui suivent de la manière suivante: on introduit dans un mélangeur interne, rempli à 70% et dont la température initiale de cuve est d'environ 90°C, l'élastomère diénique puis la charge (silice ou nitrure de bore hexagonal), la charge en fonction de l'importance du volume qu'elle représente peut être introduite en plusieurs fois. Après une à deux minutes de malaxage, les divers autres ingrédients à l'exception du système de vulcanisation. On conduit alors un travail thermomécanique (phase non-productive) en une étape (durée totale du malaxage égale à environ 5 min), jusqu'à atteindre une température maximale de « tombée » d'environ 150°C. On récupère le mélange ainsi obtenu, on le refroidit puis on ajoute le système de vulcanisation (soufre et accélérateur sulfénamide) sur un mélangeur externe (homo- fmisseur) à 30°C, en mélangeant le tout (phase productive) pendant environ 5 à 6 min. [00131] Les compositions ainsi obtenues sont ensuite calandrées soit sous la forme de plaques (épaisseur de 2 à 3 mm) ou de feuilles fines de caoutchouc pour la mesure de leurs propriétés physiques ou mécaniques. La vulcanisation (ou cuisson) est réalisée à 150 °C pendant 70 minutes. Essai 1 The following tests are carried out in the following manner: an internal mixer, filled to 70% and whose initial tank temperature is approximately 90 ° C., is then introduced into the diene elastomer and then the filler (silica or hexagonal boron nitride), the charge depending on the size of the volume it represents can be introduced in several times. After one to two minutes of mixing, the various other ingredients with the exception of the vulcanization system. Thermomechanical work (non-productive phase) is then carried out in one step (total mixing time equal to about 5 minutes), until a maximum "falling" temperature of about 150 ° C. is reached. The mixture thus obtained is recovered, cooled and the vulcanization system (sulfur and sulfenamide accelerator) is added to an external mixer (homogenizer) at 30 ° C., mixing the whole (productive phase) for about 5 to 6 hours. min. The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties. The vulcanization (or baking) is carried out at 150 ° C for 70 minutes. Trial 1
[00132] Cet essai a pour objet de montrer l'amélioration des propriétés de conductivité thermique, des propriétés mécaniques et hystérétiques d'une composition selon l'invention par rapport à des compositions témoins. [00133] Cinq compositions ont été préparées conformément au procédé détaillé dans le paragraphe précédent, elles ont la même formulation de base. Elles se différencient par la nature de la charge renforçante, la présence ou non d'un agent de couplage et par la présence ou non d'acide stéarique. [00134] Plus précisément, les compositions C0, Cl, C2, C3 et C4 sont définies comme suit : This test is intended to show the improvement of the thermal conductivity properties, mechanical properties and hysteresis of a composition according to the invention compared to control compositions. Five compositions were prepared according to the method detailed in the previous paragraph, they have the same basic formulation. They are differentiated by the nature of the reinforcing filler, the presence or absence of a coupling agent and the presence or absence of stearic acid. More specifically, the compositions C0, Cl, C2, C3 and C4 are defined as follows:
- la composition non-conforme C0 est une composition de caoutchouc comprenant de la silice à titre de charge renforçante et un agent de couplage alcoxysilane tétrasulfure et de l'acide stéarique; cette composition C0 est classiquement utilisée pour la fabrication de bande de roulement de pneumatique ;
- la composition non-conforme Cl est une composition de caoutchouc comprenant du nitrure de bore hexagonal (hBN) à titre de charge renforçante et de l'acide stéarique, elle ne comprend pas d'agent de couplage. the non-conforming composition C0 is a rubber composition comprising silica as a reinforcing filler and an alkoxysilane tetrasulfide coupling agent and stearic acid; this composition C0 is conventionally used for the manufacture of tire tread; the non-conforming composition C1 is a rubber composition comprising hexagonal boron nitride (hBN) as a reinforcing filler and stearic acid, it does not comprise a coupling agent.
- la composition non-conforme C2 est une composition de caoutchouc comprenant du nitrure de bore hexagonal (hBN) à titre de charge renforçante, de l'acide stéarique et un agent de couplage alcoxysilane tétrasulfure . the non-conforming composition C2 is a rubber composition comprising hexagonal boron nitride (hBN) as a reinforcing filler, stearic acid and an alkoxysilane tetrasulfide coupling agent.
- la composition selon l'invention C3 est une composition de caoutchouc comprenant du nitrure de bore hexagonal (hBN) à titre de charge renforçante et un agent de couplage alcoxysilane tétrasulfure ; elle ne comprend pas d'acide stéarique the composition according to the invention C3 is a rubber composition comprising hexagonal boron nitride (hBN) as reinforcing filler and an alkoxysilane tetrasulfide coupling agent; it does not include stearic acid
- la composition non-conforme C4 est une composition de caoutchouc comprenant de la silice à titre de charge renforçante et un agent de couplage alcoxysilane tétrasulfure ; elle ne comprend pas d'acide stéarique. [00135] Les formulations de ces cinq compositions sont présentées dans le tableau 1 qui suit dans lequel les quantités sont exprimées en pce: the non-conforming composition C4 is a rubber composition comprising silica as a reinforcing filler and an alkoxysilane tetrasulfide coupling agent; it does not include stearic acid. The formulations of these five compositions are presented in Table 1 which follows, in which the quantities are expressed in phr:
[00136] Tableau 1 [00136] Table 1
(1) Copolymère SBR comprenant 27% de styrène et dans la partie polybutadiène 24% de motifs -1,2 (vinyle), 30%> de motifs -1,4 cis et 46%> de motifs -1,4 trans ; sa température de transition vitreuse Tg est égale à -52°C; (1) SBR copolymer comprising 27% styrene and in the polybutadiene part 24% -1,2 units (vinyl), 30%> 1,4 cis units and 46% -1,4 trans units; its glass transition temperature Tg is equal to -52 ° C;
(2) Silice dite hautement dispersible « Zeosil 1165 MP » de la société Solvay ;
(3) Nitrure de bore hBN « MK-hBN-N70» de la société MK Impex Corp présentant une surface spécifique BET de 25m2/g et une taille moyenne de particules égale à 70 nm ; (2) highly dispersible silica Zeosil 1165 MP from Solvay; (3) HBN boron nitride "MK-hBN-N70" from MK Impex Corp having a BET surface area of 25m 2 / g and an average particle size of 70 nm;
(4) Agent de couplage tétrasulfure de bis(3-triéthoxysilpropyl) TESPT («SI69» de la société Evonik) ; (4) bis (3-triethoxysilpropyl) tetrasulfide coupling agent TESPT ("SI69" from Evonik);
(5) Diphénylguanidine (« Perkacit DPG » de la socitéé Flexsys) ; (5) diphenylguanidine ("Perkacit DPG" from Flexsys);
(6) N-l,3-diméthylbutyl-N-phényl-para-phénylènediamine (« Santoflex 6-PPD » de la société Solutia) ; (6) N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine ("Santoflex 6-PPD" from Solutia);
(7) Résine ayant une température de transition vitreuse Tg égale à 60°C «Escorez 2173 » de la société Exxon ; (7) Resin having a glass transition temperature Tg of 60 ° C "Escorez 2173" from Exxon;
(8) N-cyclohexyl-2-benzothiazyl-sulfénamide (« Santocure CBS » de la société Solutia). (8) N-cyclohexyl-2-benzothiazyl sulfenamide ("Santocure CBS" from the company Solutia).
[00137] Les propriétés obtenues après cuisson (environ 70 min à 150°C) à partir de ces compositions sont présentées dans le tableau 2 qui suit: The properties obtained after curing (approximately 70 min at 150 ° C.) from these compositions are presented in Table 2 which follows:
[00138] Tableau 2 [00138] Table 2
[00139] Lorsqu'on supprime l'acide stéarique dans la composition C0, on obtient une composition non conforme C4. Par rapport à la composition C0, seul le module MSAIOO est augmenté, les autres propriétés (hystérèse, renforcement et diffusivité) n'ont pas été modifiées. When the stearic acid is removed in the composition C0, a non-compliant composition C4 is obtained. Compared to the composition C0, only the MSAIOO module is increased, the other properties (hysteresis, reinforcement and diffusivity) have not been modified.
[00140] Par comparaison à la composition C0, on constate que la composition Cl a, à la fois, un module MSA 100 signifîcativement inférieur et un renforcement également inférieur (MSA300/MSA100). En revanche, sa conductivité thermique est améliorée par rapport à celle de la composition C0. In comparison with the composition C0, it can be seen that the composition C1 has both a substantially lower MSA modulus 100 and an equally lower reinforcement (MSA300 / MSA100). In contrast, its thermal conductivity is improved over that of the composition C0.
[00141] L'ajout d'un agent de couplage à la composition Cl permet d'obtenir une composition C2 ayant une conductivité équivalente à celle de Cl, mais qui présente un meilleur renforcement (MSA300/MSA100 est augmenté signifîcativement), une meilleure hystérèse (baisse significative de Tan (δ) max) et une meilleure rigidité (module MSAIOO augmenté).
[00142] De façon surprenante, lorsqu'on supprime l'acide stéarique dans la composition C2, on obtient une composition selon l'invention C3 dont l'hystérèse et la rigidité sont encore améliorées par rapport à la composition C2, pour un renforcement comparable. The addition of a coupling agent to the composition Cl makes it possible to obtain a composition C2 having a conductivity equivalent to that of Cl, but which has a better reinforcement (MSA300 / MSA100 is increased significantly), a better hysteresis (significant decrease in Tan (δ) max) and better rigidity (MSAIOO module increased). Surprisingly, when the stearic acid is removed in the composition C2, a composition according to the invention C3 is obtained, the hysteresis and rigidity of which are further improved with respect to the composition C 2, for a comparable strengthening. .
[00143] La baisse de l'hystérèse et l'augmentation de la rigidité s'effectue pour un module de cisaillement identique (Module G* à 60°C (MPa)) entre les compositions C2 et C3 ; indiquant à l'homme du métier que l'amélioration de ces propriétés est la seule résultante de la suppression de l'acide stéarique. Ce résultat est surprenant car l'acide stéarique est connu pour être un élément contribuant à l'obtention des priorités de rigidité dans une composition de caoutchouc. The decrease of the hysteresis and the increase of rigidity is effected for an identical shear modulus (Module G * at 60 ° C. (MPa)) between the compositions C2 and C3; indicating to the skilled person that the improvement of these properties is the only resultant of the suppression of stearic acid. This result is surprising because stearic acid is known to be a contributing factor in achieving rigidity priorities in a rubber composition.
[00144] Enfin, fait surprenant pour l'homme du métier, la valeur de Tan (δ) max atteint pour la composition C3 selon l'invention est très inférieure à celle obtenue pour la matrice de caoutchouc conventionnellement renforcée par une silice hautement dispersible (composition C0 non conforme à l'invention). La diminution de la valeur Tan (δ) max est un indicateur reconnu d'une réduction de la résistance au roulement des pneumatiques et donc la consommation d'énergie des véhicules. Par ailleurs, on constate également de façon surprenante que la valeur de MSA100 de la composition C3 est améliorée par rapport à la valeur de MSA100 mesurée pour la composition C0 ; indiquant à l'homme du métier que la composition C3 présente une meilleur rigidité que la composition C0.
Finally, surprisingly for those skilled in the art, the value of Tan (δ) max reached for the composition C3 according to the invention is much lower than that obtained for the rubber matrix conventionally reinforced by a highly dispersible silica ( composition C0 not in accordance with the invention). The decrease in the value Tan (δ) max is a recognized indicator of a reduction in the rolling resistance of tires and therefore the energy consumption of vehicles. Furthermore, it is also surprisingly found that the MSA100 value of the composition C3 is improved with respect to the value of MSA100 measured for the composition C0; indicating to the skilled person that the composition C3 has a better rigidity than the composition C0.
Claims
1. Composition de caoutchouc à base d'au moins un élastomère diénique, une charge renforçante et un système de vulcanisation, caractérisée en ce que la composition comprend à titre de charge renforçante du nitrure de bore hexagonal ayant une surface spécifique BET supérieure ou égale à 10m2 /g avec un taux allant de 30 à 350 parties pour cent parties d' élastomère (pce), au moins un agent de couplage organosilicié capable de lier le nitrure de bore hexagonal à Γ élastomère diénique, ladite composition étant dépourvue d'acide gras ou ayant un taux d'acide gras strictement inférieur à 0,5 pce. 1. Rubber composition based on at least one diene elastomer, a reinforcing filler and a vulcanization system, characterized in that the composition comprises as reinforcing filler hexagonal boron nitride having a BET specific surface area greater than or equal to 10m 2 /g with a rate ranging from 30 to 350 parts per hundred parts of elastomer (pce), at least one organosilicon coupling agent capable of linking hexagonal boron nitride to the diene elastomer, said composition being free of acid fatty or having a fatty acid level strictly less than 0.5 pce.
2. Composition selon la revendication 1 , caractérisée en ce qu'elle est dépourvue d'acide gras ou qu'elle a un taux d'acide gras strictement inférieur à 0,3 pce. 2. Composition according to claim 1, characterized in that it is devoid of fatty acid or that it has a fatty acid level strictly less than 0.3 phr.
3. Composition selon la revendication 1 ou 2, dans laquelle l'agent de couplage organosilicié est choisi parmi les silanes polysulfures, les silanes porteurs de groupements fonctionnels azodicarbonyle, les silanes porteurs d'au moins une fonction thiol, les silanes porteurs d'au moins une fonction thiol bloqué et les polyorganosiloxanes. 3. Composition according to claim 1 or 2, in which the organosilicon coupling agent is chosen from polysulphide silanes, silanes carrying azodicarbonyl functional groups, silanes carrying at least one thiol function, silanes carrying at least one minus a blocked thiol function and polyorganosiloxanes.
4. Composition selon la revendication 3, dans laquelle l'agent de couplage est un silane polysulfure de formule générale (I)4. Composition according to claim 3, in which the coupling agent is a polysulfide silane of general formula (I)
dans laquelle: in which:
x est un nombre entier ou fractionnaire supérieur ou égal à 2 ; x is an integer or fractional number greater than or equal to 2;
les symboles Ai, A2, identiques ou différents, représentent chacun un radical hydrocarboné divalent comportant de 1 à 18 atomes de carbone; the symbols Ai, A 2 , identical or different, each represent a divalent hydrocarbon radical comprising from 1 to 18 carbon atoms;
les symboles Zl s Z2 , identiques ou différents, répondent chacun à l'une des trois formules ci-après: the symbols Z ls Z 2 , identical or different, each correspond to one of the three formulas below:
R1 R1 R2 R1 R1 R2
I I
-Si— R1 -Si— R2 -Si— dans lesquelles: -Si— R1 -Si— R2 -Si— in which:
les radicaux R1, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkyle en Ci -Ci s, un cycloalkyle en C5-C18 ou un aryle en C6-Ci8 ,
les radicaux R2, substitués ou non substitués, identiques ou différents entre eux, représentent, un hydroxyle, un groupe alkoxyle en Ci-Cis ou un cycloalkoxyle en C5-C18. 5. Composition selon l'une quelconque des revendications 1 à 4, dans laquelle le système de vulcanisation comprend un oxyde de zinc à un taux allant de 0, the radicals R 1 , substituted or unsubstituted, identical or different from each other, represent a Ci -Ci s alkyl group, a C5-C18 cycloalkyl or a C 6 -Ci8 aryl, the R 2 radicals, substituted or unsubstituted, identical or different from each other, represent a hydroxyl, a C 5 -C 18 alkoxyl group or a C 5 -C 18 cycloalkoxyl. 5. Composition according to any one of claims 1 to 4, in which the vulcanization system comprises a zinc oxide at a level ranging from 0,
5 à 10 pce. 5 to 10 pce.
6. Composition selon l'une quelconque des revendications 1 à 5, dans laquelle l'élastomère diénique est choisi dans le groupe constitué par les polybutadiènes, les polyisoprènes synthétiques, le caoutchouc naturel, les copolymères de butadiène, les copolymères d'isoprène et les mélanges de ces élastomères. 6. Composition according to any one of claims 1 to 5, in which the diene elastomer is chosen from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.
7. Composition selon l'une quelconque des revendications 1 à 6, dans laquelle le taux de nitrure de bore hexagonal va de 60 à 250 pce. 7. Composition according to any one of claims 1 to 6, in which the level of hexagonal boron nitride ranges from 60 to 250 phr.
8. Composition selon l'une quelconque des revendications 1 à 7, dans laquelle le nitrure de bore hexagonal est la charge renforçante majoritaire. 8. Composition according to any one of claims 1 to 7, in which hexagonal boron nitride is the majority reinforcing filler.
9. Composition selon la revendication 8, dans laquelle le nitrure de bore hexagonal est la seule charge renforçante de la composition. 9. Composition according to claim 8, in which hexagonal boron nitride is the only reinforcing filler in the composition.
10. Composition selon la revendication 8, dans laquelle lequel le nitrure de bore hexagonal est utilisé en coupage avec une autre charge renforçante, cette autre charge renforçante étant présente dans la composition avec un taux inférieur ou égal à 30 pce. 10. Composition according to claim 8, in which the hexagonal boron nitride is used in combination with another reinforcing filler, this other reinforcing filler being present in the composition with a level less than or equal to 30 phr.
1 1. Composition selon l'une quelconque des revendications 1 à 10, dans laquelle le taux d'agent de couplage représente de 0, 1 à 7% massique par rapport à la quantité de nitrure de bore hexagonal, de préférence de 0,2 à 5% massique. 1 1. Composition according to any one of claims 1 to 10, in which the level of coupling agent represents 0.1 to 7% by weight relative to the quantity of hexagonal boron nitride, preferably 0.2 at 5% by weight.
12. Composition selon l'une quelconque des revendications 1 à 1 1 , comprenant en outre un système plastifiant, de préférence avec un taux de système plastifiant allant de 5 à 150 pce. 12. Composition according to any one of claims 1 to 1 1, further comprising a plasticizing system, preferably with a level of plasticizing system ranging from 5 to 150 phr.
13. Composition selon la revendication 12, dans laquelle lequel le système plastifiant comprend majoritairement une résine plastifiante de Tg supérieure ou égale 20°C. 13. Composition according to claim 12, in which the plasticizing system mainly comprises a plasticizing resin with a Tg greater than or equal to 20°C.
14. Article semi-fini comprenant au moins une composition définie à l'une quelconque des revendications 1 à 13.
14. Semi-finished article comprising at least one composition defined in any one of claims 1 to 13.
15. Article semi-fini selon la revendication 14, caractérisé en ce qu'il est une bande de roulement. 15. Semi-finished article according to claim 14, characterized in that it is a tread.
16. Pneumatique comprenant au moins une composition définie à l'une quelconque des revendications 1 à 13 ou comprenant au moins un article semi-fini défini aux revendications 14 ou 15.
16. Tire comprising at least one composition defined in any one of claims 1 to 13 or comprising at least one semi-finished article defined in claims 14 or 15.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR1655559A FR3052782B1 (en) | 2016-06-15 | 2016-06-15 | REINFORCED RUBBER COMPOSITION FOR PNEUMATIC |
| FR1655559 | 2016-06-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2017216484A1 true WO2017216484A1 (en) | 2017-12-21 |
Family
ID=56611445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/FR2017/051538 WO2017216484A1 (en) | 2016-06-15 | 2017-06-14 | Reinforced rubber composition for tires |
Country Status (2)
| Country | Link |
|---|---|
| FR (1) | FR3052782B1 (en) |
| WO (1) | WO2017216484A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113736150A (en) * | 2021-07-30 | 2021-12-03 | 山东华勤橡胶科技有限公司 | High-performance tread rubber composite material and preparation method and application thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113736150A (en) * | 2021-07-30 | 2021-12-03 | 山东华勤橡胶科技有限公司 | High-performance tread rubber composite material and preparation method and application thereof |
| CN113736150B (en) * | 2021-07-30 | 2023-11-07 | 山东华勤橡胶科技有限公司 | High-performance tread rubber composite material and preparation method and application thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| FR3052782B1 (en) | 2018-06-01 |
| FR3052782A1 (en) | 2017-12-22 |
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