Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
  • C08J3/205—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase
  • C08J3/21—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase
  • C08J3/215—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase at least one additive being also premixed with a liquid phase
• • 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
  • C08K9/00—Use of pretreated ingredients
  • C08K9/02—Ingredients treated with inorganic substances
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2309/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08J2309/10—Latex
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2321/00—Characterised by the use of unspecified rubbers
  • C08J2321/02—Latex

Definitions

• the invention relates to the preparation of a masterbatch of diene elastomer and reinforcing filler, the reinforcing filler consisting of a filler coated at least partially with silica, comprising at least said reinforcing filler, a metal salt and a latex of diene elastomer, in particular of a natural rubber latex.
• masterbatch refers to an elastomer-based composite in which a filler and possibly other additives have been introduced.
• the present invention relates in particular to the use of such a masterbatch for the manufacture of diene rubber compositions reinforced with a filler, for the manufacture of tires or semi-finished products for tires, in particular treads of these tires.
• carbon black has such aptitudes, which is not generally the case for inorganic fillers, in particular silicas. Indeed, for reasons of mutual affinities, these inorganic filler particles have an unfortunate tendency in the elastomeric matrix to agglomerate with each other. These interactions have the detrimental consequence of limiting the dispersion of the charge and therefore the reinforcing properties to a level substantially lower than that which it would be theoretically possible to achieve if all the bonds (inorganic filler / elastomer) that can be created during the mixing operation, were actually obtained; these interactions tend on the other hand to increase the consistency in the green state of the rubber compositions and thus to make their implementation ("processability") more difficult than in the presence of carbon black.
• reinforcing fillers at least partially covered with silica are particularly advantageous, in particular reinforcing fillers consisting of carbon black coated at least partially with silica as described in particular in the publications WO98 / 13428 and EP 711 805 B1, reinforcing fillers consisting of metal oxide coated at least partially with silica as described in particular in publication FR2888243.
• Another type of solution has been envisaged, which consists in improving the dispersibility of the filler in the elastomeric matrix by mixing the elastomer and the "liquid" phase filler.
• an elastomer in the form of latex has been used which is in the form of elastomer particles dispersed in water, and an aqueous dispersion of the filler, that is to say a dispersed silica. in water, commonly called “slurry” silica.
• slurry silica
• contacting the elastomer latex and the slurry does not allow coagulation within the medium. liquid, coagulation which should make it possible to obtain a solid which, after drying, results in obtaining the desired elastomer and silica masterbatch.
• silica aggregates are typically hydrophilic in nature and have affinity to water, so silica aggregates have more affinity with water than with the elastomer particles themselves.
• US Pat. No. 5,763,388 proposes the incorporation of silica into the rubber latex by treating the silica with a coupling agent, mixing the silica thus treated in the presence of conventional coagulation agents.
• the patent EP1321488 also proposes to put in contact an aqueous dispersion with negatively charged silica and a diene elastomer latex, with an emulsion containing a polysulfide coupling agent, in the presence of a coagulation agent such as a polyamine .
• the EPI patent 323775 also proposes bringing into contact an aqueous dispersion containing an inorganic filler such as a silica with an elastomer latex in the presence of a coagulation agent which may be constituted according to the list envisaged in this document by sodium or potassium chlorides, other salts, acids, etc. More preferentially, this method describes an additional step allowing the in situ formation of the inorganic filler during mixing between the aqueous dispersion comprising a precursor capable of forming the filler. inorganic, with the latex before adding a coagulation agent.
• a coagulation agent which may be constituted according to the list envisaged in this document by sodium or potassium chlorides, other salts, acids, etc. More preferentially, this method describes an additional step allowing the in situ formation of the inorganic filler during mixing between the aqueous dispersion comprising a precursor capable of forming the filler. inorganic, with the latex before adding a coagulation agent.
• the Applicants have surprisingly discovered a simplified method for obtaining a masterbatch of diene elastomer and reinforcing filler, the reinforcing filler being constituted by a filler coated at least partially with silica, prepared in "liquid" phase using a specific salt in a small amount determined, without the need for the addition of other additives or coagulation agents.
• This method makes it possible in particular to achieve a very good rate of return (greater than 80% by mass) by respecting the charge rate previously introduced and with a good dispersion of the charge in the elastomeric matrix.
• the method for preparing a masterbatch of diene elastomer and reinforcing filler, the reinforcing filler consisting of a filler coated at least partially with silica, according to the invention comprises the following successive stages:
• the molar ratio of metal cations defined as the number of moles of metal cations of the metal salt per charge unit area of reinforcing (expressed in mol / m 2) is between 9.3 * 10 "7 and 1.875 * 10 -5 mol / m 2 .
• the diene elastomer latex is a natural rubber latex, and in particular a concentrated latex of natural rubber.
• the silica covering the charge is a precipitation silica.
• the amount of reinforcing filler during the bringing into contact of two dispersions is between 20 phr and 150 phr, parts per hundred parts by weight of elastomer, preferably between 30 phr and 100 phr, preferably between 30 phr and 90 phr and even more preferably 30 phr and 70 phr.
• the metal salt is a magnesium salt, preferentially chosen from magnesium sulphates, magnesium halides, magnesium nitrates, magnesium phosphates, magnesium carbonates and chromates of magnesium. magnesium and more preferably still the metal salt is a magnesium sulfate.
• the molar ratio of metal cations is between 1.25 * 10 -6 and 1.875 * 10 -5 mol / m 2.
• the invention also relates to a masterbatch of diene elastomer and reinforcing filler, prepared according to the method which comprises the following successive stages: to prepare at least one reinforcing filler dispersion in water,
• the molar ratio of metal cations defined as the number of moles of metal cations of the metal salt per unit of reinforcing filler surface (expressed in mole per m 2 of reinforcing filler surface) is between 9.3 * 10 "7 and 1875 * 10 ⁇ 5 mol / m 2 .
• the subject of the invention is also a rubber composition based on at least one masterbatch as mentioned above, as well as a finished or semi-finished article, a tire tread or a tire or product. semi-finished product comprising at least one such rubber composition.
• the molar ratio of metal cations is defined as the number of moles of metal cations of the metal salt per unit area of reinforcing filler (expressed in mol / m 2 ), the reinforcing filler surface unit being defined as the mass of filler reinforcement considered multiplied by BET specific surface area.
• a mass ml of metal salt having a molar mass Ml and a number N of metal atoms per molecule of salt, added to a mass m2 of reinforcing filler (regardless of whether or not the reinforcing filler is already dispersed in an aqueous solution) having a specific surface area measured by BET S2 (in m 2 / g)
• the molar level of metal cations expressed in mol / m 2 is equal to: [(ml / Ml) * N] / (m2 * S2 ).
• the BET surface area is determined according to the method of BRUNAUER - EMMET - TELLER described in "The Journal of the American Chemical Society", Vol. 60, page 309, February 1938 and corresponding to standard NF T 45007.
• the purpose of this procedure is to quantify the categories of constituents of the rubber mixes. There are 3 temperature ranges that each correspond to a category of constituents: - between 250 and 550 ° C, corresponding to organic materials: elastomers, oils, vulcanizing agents ...
• the quantity of product analyzed must be weighed to 0.0 lmg and between 20 and 30 mg.
• 2nd segment dynamics of 550 to 750 ° C at 10 ° C / min, in air (or 02) (40 ml / min)
• the blank curve is made following the procedure described in the TGA User's Manual.
• the TGA takes into account, in order to determine the losses, the mass of the sample P2 which it calculates at the effective start of the measurement from the weight of the crucible, which is essential for the calculation of the residue; P2 is calculated by the TGA taking into account the mass P3 (Crucible + sample) at time T0 - PO.
• volatile matter rate then calculated by the apparatus is erroneous since a part of MV, volatile matter (PI - P2) evaporated during the wait between the preparation and the actual start of the measurement.
• Tx load (pcmo) [(D) / (B + C)] * 100
• the coagulation yield corresponds to the ratio of the recovered dry mass (from which the mass of residual volatiles after drying as defined in the ATG measurement protocol has been removed in the preceding paragraphs) on the target mass. initially, multiplied by one hundred.
• the method for preparing a masterbatch of diene elastomer and reinforcing filler, the reinforcing filler consisting of a filler coated at least partially with silica according to the invention comprises the following successive steps: - preparing at least one reinforcing filler dispersion in water,
• the molar ratio of metal cations defined as the number of moles of metal cations of the metal salt per charge unit area of reinforcing (expressed in mol / m 2) is between 9.3 * 10 "7 and 1.875 * 10 -5 mol / m 2 II- 1)
• any filler coated at least partially with silica may be used.
• the filler coated at least partially with silica may consist in particular of carbon black, metal hydroxides, in particular magnesium or aluminum, and crosslinked polymer particles.
• the surface of the reinforcing filler is predominantly (that is to say more than 50% of the surface) covered with silica or totally covered with silica.
• Carbon blacks partially or wholly covered with silica by a post-treatment, or silica blacks modified in situ by silica, such as, without limitation, the charges marketed by Cabot Corporation under the name EcoblackTM are particularly suitable.
• Such a reinforcing filler is preferably covered with a silica content of 10% by weight of the reinforcing filler.
• silica-coated synthetic metal hydroxides whose metal M is selected from the group consisting of Al, Fe, Mg, and mixtures of these metals.
• M represents Al or Mg as described in particular in the publications WO06 / 002993 or WO07 / 003408.
• the reinforcing metal hydroxide may be prepared by any known method of coating ("coating") a mineral or organic filler with silica, applied in the present case to a synthetic metal hydroxide including the metal M is selected from the group consisting of Al, Fe, Mg and mixtures of these metals.
• such a coating method comprises the following steps: starting from a hydroxide suspension of the metal M in water or any solvent suitable for the synthesis of the silica;
• the concentration of the metal hydroxide suspension M is preferably less than 20 g / l, more preferably less than 10 g / l (for example of the order of 5 g / l).
• the filtrate is washed once or several times in the water or the solvent used for the synthesis of the silica, it being specified that the last washing operation is preferably carried out in water.
• the filtrate thus obtained is then dried with drying means capable of limiting the agglomeration of the hydroxide particles during the removal of the water.
• the drying means that can be used are known to a person skilled in the art: it is possible to carry out, for example, freeze-drying, spraying, or under super-critical conditions, or to use any other equivalent means capable of preventing excessive agglomeration, by capillarity, of hydroxide particles when removing water.
• a coating process inspired by at least one of the following known methods can be used: a method for recovering particles by hydrolysis of tetraethylorthosilicate (TEOS) in alcohol (M. Ohmori and E. Matijevic) J. Colloid Inter Sci 160, 288-292 (1993)), a method which itself derives from the known method for the synthesis of silica under the name "Stoeber” (W. Stoeber, A. Fink, E. Bohm J. Colloid Inter Sci 26, 62-69 (1968)); - Silica synthesis method from a sodium silicate precursor (Na 2 SiO 3 ) as described for example in the patent application EP-A-0 407 262;
• TEOS tetraethylorthosilicate
• the level of silica present on the surface of this metal hydroxide represents between 5% and 50%, more preferably between 10% and 40%, in particular between 15% and 35% (% by weight of the total weight of coated hydroxide).
• metal hydroxide any hydroxide including oxide-hydroxide of said metals or mixture of metals, whatever its form, crystalline or amorphous, anhydrous or hydrated, and the nature of its possible impurities.
• the BET specific surface area of this reinforcing metal hydroxide is preferably between 50 and 700 m. 2 / cm 3, more preferably between 100 and 600 m 2 / cm 3 (for example between 200 and 500 m 2 / cm 3); its average particle size, denoted dw, is preferably between 20 and 400 nm, more preferably between 50 and 300 nm (for example between 100 and 200 nm).
• the silica is then dispersed in water, preferably so as to obtain a dispersion whose viscosity is sufficient to be easily "manipulable".
• the mass concentration of silica in the dispersion is between 0.1 and 30%.
• the dispersion is sheared by sonification in order to make it possible to obtain stability of the aggregates in the water, which makes it possible to improve the dispersion of the silica in the masterbatch subsequently produced.
• This sonication can notably be carried out using a Vibracell generator manufactured by SONICS and Materials Inc. of 1500 Watts with a piezoelectric converter with PZT crystal (reference 75010), a booster for the probe and a 19mm diameter titanium alloy probe. (for a height of 127mm).
• a Vibracell generator manufactured by SONICS and Materials Inc. of 1500 Watts with a piezoelectric converter with PZT crystal (reference 75010), a booster for the probe and a 19mm diameter titanium alloy probe. (for a height of 127mm).
• the metal salt is then added and the mixture is stirred with a spatula, in order to allow the salt to dissolve.
• the metal salt can advantageously be added to the aqueous silica dispersion before the sonication step, in particular in order to improve the solubilization of the salt in the aqueous dispersion produced. II-2) Metal salt
• the metal salt of at least one divalent metal may in particular consist of a magnesium salt, a calcium salt, an aluminum salt or a zinc salt, and more preferably a magnesium salt.
• magnesium salts magnesium hydrates, magnesium aluminates, magnesium sulphates, magnesium borates, magnesium halides, and in particular magnesium chlorides, magnesium bromides and magnesium fluorides are more particularly suitable. and magnesium iodides, magnesium hydrides, magnesium nitrates, magnesium phosphates, magnesium carbonates and magnesium chromates. Even more preferentially, the magnesium salt is chosen from magnesium sulphates, magnesium halides and magnesium nitrates and even more preferentially the metal salt chosen is a magnesium sulphate.
• the elastomer latex is a particular form of elastomer which is in the form of elastomer particles dispersed in water.
• the invention relates to diene elastomer latices, the diene elastomers being defined as follows:
• elastomer or "diene” rubber it is to be understood in known manner an elastomer derived at least in part (ie, a homopolymer or a copolymer) from monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or otherwise).
• diene elastomers can be classified into two categories: "essentially unsaturated” or "essentially saturated”.
• essentially unsaturated is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%); for example diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins EPDM type do not fall within the above definition and may in particular be described as "essentially saturated” diene elastomers (low or very low diene origin, 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 elastomers there are also natural rubber and synthetic elastomers.
• NR natural rubber
• this natural rubber exists in different forms as detailed in Chapter 3 "Latex concentrates: properties and composition", K.F. Gaseley, A.D.T. Gordon and T. D. Pendle in “Natural Rubber Science and Technology", A. D. Roberts, Oxford University Press - 1988.
• the latex can be used directly or be previously diluted in water to facilitate its implementation.
• diene elastomer By synthetic diene elastomers which can be used in accordance with the invention, the term diene elastomer is more particularly understood to mean:
• 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-hexa
• Suitable vinylaromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the "vinyl-toluene" commercial mixture, para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.
• the copolymers may contain between 99% and 20% by weight of diene units and between 80% and 80% by weight of vinylaromatic units.
• the 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 the 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.
• 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 of the epoxidized type.
• Suitable polybutadienes and in particular those having a content (mol%) in units -1.2 between 4%> and 80%> or those having a content (%> molar) in cis-1,4 greater than 80%> polyisoprenes, butadiene-styrene copolymers and in particular those having a Tg (glass transition temperature (Tg, measured according to ASTM D3418) between 0 ° C. and -70 ° C. and more particularly between -10 ° C.
• Tg glass transition temperature
• butadiene-styrene-isoprene copolymers are especially suitable those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40%, an isoprene content of between 15% and 60%.
• the synthetic diene elastomer (s) according to the invention are preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), butadiene copolymers, copolymers of isoprene and mixtures of these elastomers.
• BR polybutadienes
• IR synthetic polyisoprenes
• butadiene copolymers copolymers of isoprene and mixtures of these elastomers.
• Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-copolymers.
• SBIR butadiene-styrene
• the latex can in particular consist of a synthetic diene elastomer already available in the form of an emulsion (for example a copolymer of butadiene and styrene, SBR, prepared in emulsion), or a diene elastomer.
• synthetic solution initially for example a SBR prepared in solution
• a surfactant for example a surfactant
• SBR latex in particular an emulsion-prepared SBR (“ESBR”) or an SBR prepared in solution (“SSBR”), and more particularly an SBR prepared in emulsion.
• ESBR emulsion-prepared SBR
• SSBR SBR prepared in solution
• an SBR elastomer (ESBR or SSBR)
• an SBR having an average styrene content for example between 20% and 35% by weight, or a high styrene content, for example 35 to 35% by weight, is used in particular.
• a BR preferably having more than 90% (%> molar) of cis-1,4 bonds.
• one or more natural rubber latexes may be used in the form of a blend, one or more synthetic rubber latexes in a blend or a blend of one or more natural rubber latexes with one or more synthetic rubber latexes.
• Both dispersions are contacted in the presence of a metal salt of at least one divalent metal.
• the salt is added to the aqueous dispersion of reinforcing filler as has been previously explained, that is to say during the formation of the aqueous reinforcing filler dispersion or after its formation.
• the metal salt during the contacting of the aqueous dispersion of reinforcing filler and the elastomer latex.
• any type of apparatus allowing an "effective" mixing of two products in the liquid phase can also be used, so it will be possible to use a static mixer such as static mixers marketed by Noritake Co., Limited, TAH in the US, KOFLO with USA, or TOKUSHU KIKA KOGYO Co., Ltd. or a high shear mixer such as mixers marketed by TOKUSHU KIKA KOGYO Co., Ltd., or by PUC in Germany, by CAVITRON in Germany or by SILVERSON in the UK.
• a static mixer such as static mixers marketed by Noritake Co., Limited, TAH in the US, KOFLO with USA, or TOKUSHU KIKA KOGYO Co., Ltd. or a high shear mixer such as mixers marketed by TOKUSHU KIKA KOGYO Co., Ltd., or by PUC in Germany, by CAVITRON in Germany or by SILVERSON in the UK.
• a coagulum of elastomer and reinforcing filler is formed either in the form of a single solid element in the solution, or in the form of several separate solid elements.
• the molar ratio of metal cations defined as the number of moles of metal cations of the metal salt per unit area of reinforcing filler (expressed in mol / m 2 ), must be between 9.3 * 10 "7 and 1.875 * 10 ⁇ 5 mol / m 2 .
• the metal salt is a magnesium salt
• the molar ratio of metal cations is between 1.25 * 10 -6 and 1.875 * 10 -5 mol / m 2 .
• the volumes of the two dispersions to put in contact and in particular the volume of reinforcing filler dispersion depends on the rate of reinforcing filler aimed for the masterbatch to achieve, taking into account of course the respective concentrations of the dispersions. So the volume will be adapted accordingly.
• the level of reinforcing filler aimed for the masterbatch is between 20 and 150 phr (parts by weight per hundred parts of elastomer), preferably between 30 and 100 phr and more preferably between 30 and 90 phr, more preferably between 30 and 70 pce.
• the solids recovered are filtered or centrifuged. Indeed, the filtering operation that can be carried out using a sieve or filtering cloth, may be unsuitable when the coagulum is in the form of many small and solid elements. In such a case, an additional centrifugation operation is preferably carried out.
• the coagulum obtained is dried, for example in an oven.
• the dry coagulum obtained may advantageously be homogenized in order to ensure the representativity of the sample for measuring the degree of charge, for example by performing a light mechanical work on a cylinder tool.
• the masterbatches thus produced may be used in rubber compositions, in particular for tires.
• the rubber compositions for tires based on the masterbatches according to the invention may also comprise, in known manner, a coupling agent and a vulcanization system.
• coupling agent is understood to mean, in known manner, an agent capable of establishing a sufficient bond, of a chemical and / or physical nature, between an inorganic filler (or the inorganic surface of a filler) and the elastomer diene; such a coupling agent, at least bifunctional, has for example as simplified general formula "Y-Z-X", in which:
• Y represents a functional group ("Y" function) which is capable of binding physically and / or chemically to the inorganic filler (or to the inorganic surface of a filler), such a bond can be established, for example, between a silicon atom of the coupling agent and the hydroxyl (OH) groups of the surface of the charge (for example surface silanols when it is silica);
• X represents a functional group ("X" function) capable of binding physically and / or chemically to the diene elastomer, for example via a sulfur atom;
• Z represents a divalent group making it possible to connect Y and X.
• Coupling agents in particular silica / diene elastomer have been described in a very large number of documents, the best known being bifunctional organosilanes bearing alkoxyl functions (that is to say, by definition, “alkoxysilanes”) to title of functions "Y” and, as functions "X", functions capable of reacting with the diene elastomer such as for example polysulfide functions.
• TESPT bis 3-triethoxysilylpropyl tetrasulfide
• the coupling agent in the preparation of the masterbatch so as to obtain directly a masterbatch of elastomer and reinforcing filler also comprising a coupling agent.
• the coupling agent may thus be added before or during the bringing into contact of the aqueous dispersion of reinforcing filler and of the diene elastomer latex
• These rubber compositions in accordance with the invention may also comprise all or part of the usual additives normally used in elastomer compositions intended for the manufacture of tires, in particular treads, for example plasticizers or lubricating oils. extension, whether these are aromatic or non-aromatic, pigments, protective agents such as anti-ozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents, reinforcing resins, acceptors (for example phenolic novolac resin) or methylene donors (for example HMT or H3M) as described for example in the application WO 02/10269, a crosslinking system based on either sulfur or sulfur donors and / or peroxide and / or bismaleimides, vulcanization accelerators.
• plasticizers or lubricating oils for example plasticizers or lubricating oils.
• protective agents such as anti-ozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents, reinforcing resins, acceptors (for example
• these compositions comprise, as preferred non-aromatic or very weakly aromatic plasticizing agent, at least one compound selected from the group consisting of naphthenic, paraffinic, MES, TDAE oils, esters (especially trioleate) oils.
• glycerol the hydrocarbon plasticizing resins having a high Tg preferably greater than 30 ° C, and mixtures of such compounds.
• compositions can also contain, in addition to the coupling agents, coupling activators, covering agents (comprising, for example, the only Y function) of the reinforcing filler or, more generally, processing aid agents capable of in a known manner, by improving the dispersion of the filler in the rubber matrix and by lowering the viscosity of the compositions, to improve their ability to use in the green state, these agents being examples of hydrolysable silanes such as alkylalkoxysilanes (especially alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanolamines), hydroxylated or hydrolyzable POSs, for example ⁇ , ⁇ -dihydroxy-polyorganosiloxanes (in particular ⁇ , ⁇ -dihydroxy-polydimethylsiloxanes), fatty acids such as, for example, stearic acid.
• 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 thermomechanical mixing (sometimes called phase “non-productive") 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 mechanical working phase (sometimes referred to as "Productive” phase) at lower temperature, typically below 120 ° C, for example between 60 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system or vulcanization.
• a first phase of work or thermomechanical mixing sometimes called phase "non-productive”
• a second mechanical working phase sometimes referred to as "Productive” phase
• all the basic constituents of the compositions of the invention are intimately incorporated, by kneading, with the diene elastomer during the first so-called non-productive phase, that is, that is to say that is introduced into the mixer and that is kneaded thermomechanically, in one or more steps, at least these various basic constituents until the maximum temperature between 130 ° C and 200 ° C, preferably between between 145 ° C and 185 ° C.
• the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary constituents, the possible coating agents, are introduced into a suitable mixer such as a conventional internal mixer. or other complementary additives and other additives, with the exception of the vulcanization system.
• the total mixing time in this non-productive phase is preferably between 1 and 15 minutes.
• the vulcanization system is then incorporated at low temperature, usually in an external mixer such as a cylinder mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.
• a covering agent When a covering agent is used, its incorporation can be carried out completely during the non-productive phase, at the same time as the load, or in total during the productive phase, at the same time as the vulcanization system, or split over the two successive phases.
• the crosslinking system is preferably a vulcanization system, that is to say a system based on sulfur (or a sulfur-donor agent) and a primary vulcanization accelerator.
• a vulcanization system that is to say a system based on sulfur (or a sulfur-donor agent) and a primary vulcanization accelerator.
• various known secondary accelerators or vulcanization activators such as zinc oxide.
• 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 is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr. It is possible to use as accelerator (primary or secondary) any compound capable of acting as accelerator for vulcanization of diene elastomers in the presence of sulfur, in particular thiazole-type accelerators and their derivatives, accelerators of the thiuram type, zinc dithiocarbamates.
• accelerators are for example selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "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 sulfen
• the final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or else extruded in the form of a rubber profile that can be used, for example, as a tread. tire for passenger vehicle.
• Vibracell ultrasound generator manufactured by SONICS and Materials Inc of 1500 Watts (ref: VC1500, 20kHz), with a piezoelectric converter with PZT crystal (reference CV154), a booster for the probe (ref BHN15GD, amplitude increased by 50%) and a standard non-threaded probe (not "high gain”) in 19mm diameter titanium alloy (for a height of 127mm)
• filler A silica-coated carbon black "CRX 4210" marketed by Cabot Corporation (recovery rate 55%, density g / cm 3 , BET specific surface area measured at 145 m 2 / g, with an effective density of 2.064 g / cm 3 ,
• filler B magnesium hydroxide coated with silica prepared according to the process described in publication FR 2,888,243, exhibiting a recovery rate of 100%, BET specific surface area measured 128 m 2 / g, with a specific density of 2.28 g / cm 3
• latex HA grade natural rubber latex, marketed by TRANG LATEX / Beetex (Thailand), having a solids content measured at 61.12%, pH of about
• a quantity of reinforcing filler of 56 parts by weight per hundred parts of elastomer which in this case corresponds to 56 phr (indeed the masterbatches described here only include the reinforcing filler and the diene elastomer), was chosen.
• the suspension of [reinforcing filler + water + salt] was sonified at 60% of the maximum power of the ultrasound generator, for 8 minutes, the beaker of 100 ml being kept at a fixed temperature while being immersed in an ice bath.
• the dispersion thus obtained just sonifée is then maintained with magnetic stirring (500tr / min) until contacting.
• the latex is weighed and its concentration adjusted (dilution by addition of ultrapure water) - put in contact
• the previously obtained dispersion (reinforcing filler + water + salt) is poured into the latex with magnetic stirring (500 rpm).
• the coagulum formed or the solids formed are centrifuged, even in cases where the visual appearance of the coagulum makes it possible to envisage an operation. filtering.
• the centrifugation is carried out, after transfer into a 250mL nalgene flask, using a Sigma 4K15 scoop centrifuge at 8000 rpm for 10 minutes.
• the coagulum in the form of a pellet
• the coagulum thus recovered is dried under a fume hood at room temperature for 24 hours and then under vacuum in an oven for 24 hours at 65 ° C. under 100 to 300 mbar in order to remove the last traces of water.
• the ATG loading rate and the coagulation yield are then measured on the master batch thus produced.
• a slight mechanical work such as on a cylinder tool, to homogenize the coagulum and ensure the representativeness of the sampling of the measurement.
• This example is intended to demonstrate the proper operation of the method according to the invention with reinforcing fillers A or B.
• the metal salt used in this example being a magnesium sulfate MgSO 4, 7H 2 0 as specified in paragraph III-1.
• Tests Al, A2 and B3 were carried out in accordance with the method detailed in the preceding paragraph with:
• tests A1, A2 and B3 are distinguished from each other as follows:
• the molar ratio of metal cations is 1.091 * 10 -5 mol / m 2 (corresponding to a mass of hydrated magnesium sulphate of 1.524 g).
• the method according to the invention makes it possible to obtain masterbatches of diene elastomer and reinforcing filler meeting the desired criteria in terms of the level of charge observed and the yield obtained.

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• 2013
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