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
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • 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
  • C08J2309/06—Copolymers with styrene
  • C08J2309/08—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 synthetic diene elastomer and silica comprising at least one silica (modified) and a synthetic diene elastomer latex, in particular of butadiene and styrene copolymer.
• masterbatch (commonly referred to by its English name as “masterbatch”) means 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 inorganic filler-reinforced diene rubber compositions 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.
• HD type silicas having a BET surface area of between 100 and 250 m 2 / g.
• a high surface area silica HD referring in the field of "Green Tires” is in particular the silica "Zeosil 1165 MP" (BET surface equal to about 160 m 2 / g) marketed by Rhodia.
• the use of this silica "Zeosil 1165 MP" makes it possible to obtain good compromises in terms of tire performance, in particular satisfactory wear resistance and rolling resistance.
• the advantage of using a high surface area silica resides mainly in the possibility of increasing the number of bonds of the silica with the elastomer and therefore of increasing the level of reinforcement thereof.
• Another type of solution has been envisaged which consists, in order to improve the dispersibility of the filler in the elastomeric matrix, of mixing the elastomer and the "liquid" phase filler.
• an elastomer in the form of a latex is used in the form of elastomer particles dispersed in water, and aqueous dispersion of the filler, that is to say a silica dispersed in water, commonly called “slurry”.
• slurry silica dispersed in water
• 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.
• 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 Applicants have surprisingly discovered a method for obtaining a silica-elastomer masterbatch prepared in the "liquid" phase without using a coagulation agent or a coupling agent.
• Such a method allows, moreover, not only to achieve a very good rate of return (greater than 80% by mass) by respecting the feed rate previously introduced and with good dispersion of the filler in the elastomeric matrix.
• the method for preparing a masterbatch of synthetic diene elastomer and silica comprises the following successive stages:
• the coagulum recovery step is performed by a filtering operation.
• the coagulum recovery step is performed by a centrifugation operation.
• the synthetic elastomer latex is a latex of butadiene copolymer and styrene, SBR, and more preferably still the synthetic elastomer latex is an SBR prepared in emulsion.
• the silica is a precipitated silica.
• the metallic element is aluminum, one of the following conditions being preferably satisfied:
• the formulation pH is greater than 5.5 and the aluminum doping rate of the silica is greater than or equal to (2 * pH-10).
• the invention also relates to a masterbatch of synthetic diene elastomer and silica prepared according to the method which comprises the following successive steps:
• the subject of the invention is also a rubber composition based on at least one masterbatch of synthetic diene elastomer and of silica prepared according to the method according to the invention, as well as a finished or semi-finished article. , a tire tread a tire or semi-finished product comprising at least one such rubber composition.
• diope means silica with a metallic element, the fact of modifying the surface of the silica so as to integrate this metallic element in the mesh of the peripheral layers of the silica and / or on the surface of this silica .
• doped silica in particular silica “doped” aluminum, a silica possessing a metal element, in particular aluminum, in the mesh of its peripheral layers and / or on its surface.
• This method is used to determine the surface aluminum of doped silicas by atomic emission spectrometry (ICP-AES). These silicas are prepared by doping with a commercial silica.
• the measurements will be done in duplicate. It is preferable to make a blank procedure during each series of measurements (preparation in the same conditions but without sample). The raw silicas before doping will also be analyzed.
• the verification indicator is prepared in each series of measurements in the same way as the above standards by introducing 1 ml of aluminum standard solution at 1 g / l of a different batch. It validates the calibration. The verification cookie does not keep after use. d) -4- ICP-AES Assay:
• Verification standard E5 (theoretical value: 50mg / l)
• Plasma and nebulization settings Plasma and nebulization settings:
• Spray chamber cyclonic type (Scott chamber)
• Plasma gas flow 12 1 / min
• Sheathing gas flow rate 0.2 1 / min
• the uncertainty of measurement was determined on the ICP-AES spectrometer: Jobin Yvon Activa M at the rate of three measurements per day during 6 days. The uncertainty given is three standard deviations.
• the pH is measured according to the following method deriving from the ISO 787/9 standard (pH of a suspension at 5% in water)
• Reaction medium stirred with mechanical stirring (about 650 rpm)
• the quantity of product analyzed must be weighed to 0.0 lmg and between 20 and 30 mg.
• 2nd segment Dynamic from 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 - P0.
• 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
• B is the percentage of organic material (range 250-550 ° C)
• C is the percentage of losses (between 550 and 750 ° C)
• D is the percentage of residue (above 750 ° C).
• the coagulation yield corresponds to the ratio of the recovered dry mass (from which the mass of volatile matter as defined in the ATG measurement protocol has been removed in the preceding paragraphs) to the initial target mass. multiplied by one hundred.
• the method for preparing a masterbatch of synthetic diene elastomer and silica according to the invention comprises the following successive stages:
• a latex of synthetic diene elastomer in particular a latex of butadiene and styrene copolymer, SBR, and the doped silica dispersion,
• the silica is doped with an at least divalent metal element.
• aluminum may be particularly mentioned.
• This "doping" step of the silica can advantageously be carried out according to the protocol detailed in the patent application WO 02/051750.
• the doping level obtained corresponds to the percentage by weight of aluminum per hundred parts by weight of silica.
• any silica S1O2 known to those skilled in the art, especially any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m 2 / g, preferably 30 to 400 m 2 / g.
• HDS highly specific silicas
• the silicas “Ultrasil” 7000 and “Ultrasil” 7005 from Degussa the "Zeosil” silicas 1165MP, 1135MP and 1115MP from Rhodia.
• the silica "Hi-Sil EZ150G” from PPG the silica "Hi-Sil EZ150G “from PPG, the” Zeopol "silicas 8715, 8745 and 8755 from the Huber Company, high surface area silicas as described in application WO 03/16837.
• a doped silica having a doping level greater than or equal to 2% by weight and even more preferably greater than 2.5% by weight is produced, the doping level representing the content of aluminum present in the doped silica expressed by weight.
• the doped silica obtained is then dispersed in water, preferably so as to obtain a dispersion whose viscosity is sufficient to be easily "manipulable".
• a dispersion whose viscosity is sufficient to be easily "manipulable”.
• an aqueous dispersion of silica doped with a silica content in water of 4% by weight can be produced.
• the dispersion is sonifée to allow to obtain a stability of the aggregates in water, which improves the aqueous dispersion of silica doped in the master batch then produced.
• This sonification 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).
• an acidifying agent such as strong acids or weak acids, to allow the pH of the aqueous dispersion of doped silica to be modified in order to obtain at the time of setting contact of the two dispersions described in the following, the pH of the targeted formulation.
• elastomer or "diene” rubber By 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 diene monomers (monomers carrying two carbon-carbon double bonds). carbon, conjugated or not). These diene elastomers can be classified into two categories: "essentially unsaturated” or "essentially saturated”.
• essentially unsaturated is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%);
• diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the above definition and may in particular be described as "substantially 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%.
• iene elastomer can be understood more particularly to be used in the compositions according to the invention:
• 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 may for example be blocks, statistics, sequenced, microsequenced, and prepared in dispersion or 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 of between 4% and 80% or those having a content (%> molar) in cis-1,4 greater than 80%>, the polyisoprenes, copolymers of butadiene-styrene and in particular those having a Tg (glass transition temperature (Tg, measured according to ASTM D3418) of between 0 ° C. and -70 ° C. and more particularly between -10 ° C. and -60 ° C.
• Tg glass transition temperature
• styrene content between 5%> and 60%> by weight and more particularly between 20%> and 50%>, a content (%> molar) in -1,2 bonds of the butadiene part of between 4% and 75%, a content (mol%) of trans-1,4 bonds of between 10% and 80%), butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90%. by weight and a Tg of -40 ° C to -80 ° C, the isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg between - 5 C and - 50 ° C.
• butadiene-styrene-isoprene copolymers those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40%, in particular an isoprene content of between 15% and 50% by weight are suitable.
• the diene elastomer (s) of the composition 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, isoprene copolymers and mixtures of these elastomers.
• BR polybutadienes
• IR synthetic polyisoprenes
• IR butadiene copolymers
• BIR isoprene-butadiene copolymers
• SIR isoprene-styrene copolymers
• SIR isoprene-styrene copolymers
• the synthetic diene elastomer latex may 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 an elastomer synthetic diene solution initially in solution (for example an SBR prepared in solution) which is emulsified in a mixture of organic solvent and water, generally by means of 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.
• a vinyl ring 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 Tg of between -10 ° C. and - 55 ° C;
• SBR can be advantageously used in admixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.
• Both dispersions are brought into contact. To allow the proper mixing of these solutions, they are for example poured into a beaker with magnetic stirring. 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.
• 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
• mixers such as high shear mixers are preferred.
• a coagulum of elastomer and silica is formed either as a single solid element in the solution, or in the form of several separate solid elements.
• formulation pH of this new dispersion is measured according to the protocol described previously in the tests.
• pH of formulation is between 3.5 and 5.5 and silica doping rate of silica greater than or equal to 0.5% by weight;
• pH of formulation is greater than 5.5 and doping rate by silica aluminum greater than or equal to (2 * pH-10).
• the volumes of the two dispersions to put in contact and in particular the silica dispersion volume depends on the target silica level for the masterbatch to be produced. So the volume will be adapted accordingly.
• the target silica content 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 90 phr. and 70 pce. II-4) Recovery of the formed solid.
• the solids recovered are filtered or centrifuged. Indeed, the filtering operation that can be performed using a filtration screen, 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 masterbatches thus produced are capable of being used in rubber compositions, in particular for tires.
• the tire rubber compositions based on the masterbatches according to the invention also comprise, in a known manner, a coupling agent and a vulcanization system.
• coupling agent is understood, in known manner, an agent capable of establishing a sufficient bond, chemical and / or physical, between the inorganic filler and the diene elastomer; 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, such a bond being able to be established, for example, between a silicon atom of the coupling agent and the surface hydroxyl (OH) groups of the inorganic filler (for example surface silanols in the case of 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 as 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 in order to obtain directly a masterbatch of elastomer and silica also comprising a coupling agent.
• the coupling agent can thus be added before or during the contacting of the aqueous dispersion of doped silica and the SBR 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, vulcanization activators.
• additives normally used in elastomer compositions intended for the manufacture of tires, in particular treads for example plasticizers or lubricating oils.
• plasticizers or lubricating oils for example plasticizers or lubricating oils.
• 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 may also contain, in addition to the coupling agents, coupling activators, coating agents (comprising, for example, the only function Y) of the reinforcing inorganic filler or, more generally, processing aids which can be used in a known manner, by improving the dispersion of the inorganic filler in the rubber matrix and by lowering the viscosity compositions, to improve their ability to implement in the green state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes (especially alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), amines primary, secondary or tertiary (for example trialkanol-amines), hydroxylated or hydrolysable POS, for example ⁇ , û-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. implementation and other additives 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, generally in an external mixer such as a roller mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.
• a coating agent When a coating agent is used, its incorporation can be carried out entirely during the non-productive phase, together with the inorganic filler, or in full during the productive phase, together with the vulcanization system, or still 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.
• 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 preferred level of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.
• accelerator 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.
• the pH is maintained at 7.5 during the addition of the aluminum sulphate in order to prevent the sharp increase in the viscosity of the medium
• the suspension thus sheared is introduced into the reactor and 2964.67 ml of demineralized water are added to obtain an initial concentration of 40 g / l, ie 3.8% w.
• the medium is stirred at 650 rpm and is heated to 60 ° C. (using a temperature probe integrated into the electrode and adjust to this temperature)
• the A1 2 (SO 4 ) 3 , 18H 2 O is added at 15 ml / min and the pH of the medium is stabilized at 7.5 by simultaneous addition of sodium hydroxide
• reaction medium is left stirring and heating for 30 minutes (pH regulation at 7.5), then the pH is lowered to 4.5 by addition of H 2 SO 4 .
• the cake obtained is resuspended in demineralised water at a concentration of approximately 10% w.
• a measurement of volatile matter is carried out on the suspension contained in the suspension bottle (for use in the manufacture of masterbatches) in order to know the exact mass concentration of the suspension Material:
• the measurement conditions 160 ° C without temperature ramp, duration of 30 minutes
• taring of the aluminum cup about 2.5 g of sample are introduced into the cup and we start the measurement.
• the aluminum doped silicas previously obtained are dispersed in water so as to obtain a concentration of 4% by weight of silica in water.
• the volume of the aqueous dispersion of doped silica is adjusted in relation to the volume of the latex as a function of the concentration of the silica and the concentration of the latex, so that, when the two dispersions are brought into contact (silica and elastomer latex), ) the desired formulation pH.
• an amount of silica of 50 parts by weight per hundred parts of elastomer was chosen, which corresponds here to 50 phr (in effect the masterbatches described here only comprise silica and the diene elastomer).
• the pH measuring electrode is introduced into the mixture in order to measure the formulation pH.
• the coagulum formed or the solids formed are centrifuged, including in cases where the visual appearance of the coagulum made it possible to envisage a filtering operation.
• 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 thus recovered is dried under a fume hood at room temperature for 24 hours and then in an oven for 24 hours at 65 ° C. under a pressure of 300 mbar in order to remove the last traces of water.
• test E3 (whose formulation pH is 6.5) that the coagulation yield is less than 80% and therefore outside the acceptable tolerance.
• the silica level for the E3 test is also outside the acceptable tolerance (20% deviation from the 50pcmo target), which means only a part of the elastomer has coagulated with the silica.
• Example 1 This example is intended to demonstrate the proper functioning of the method according to the invention, in particular vis-à-vis the formulation pH measured for a silica doping rate distinct from Example 1.
• the tests E '1, E'2 and E'3 were made according to the method detailed in the preceding paragraph with an SBR latex to that cited in Example 1 and with an aluminum doped silica with a doping level of 2.5 % in weight ; the amount of silica during the contacting of the two dispersions being 50 phr.
• the only difference between these three tests consists, during the previously detailed operating method, in modifying the pH of the doped silica aqueous dispersion in order to modify the formulation pH, thus:
• the formulation pH is 7.5.
• test E'3 (whose formulation pH is 7) that the coagulation yield is less than 80% and therefore outside the acceptable tolerance.
• the silica level for the E'3 test is also outside the acceptable tolerance (20% deviation from the 50pcmo target), the very high level of silica obtained shows that a small part of the elastomer has coagulated with silica.
• tests E '1 and E'2 make it possible to obtain masterbatches with both acceptable silica levels (between 40 .mu.m and 60 .mu.C) and a coagulation yield greater than 80%.

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