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
  • C08J3/22—Compounding polymers with additives, e.g. colouring using masterbatch techniques
• • 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
  • C08J3/22—Compounding polymers with additives, e.g. colouring using masterbatch techniques
  • C08J3/226—Compounding polymers with additives, e.g. colouring using masterbatch techniques using a polymer as a carrier
• • 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
  • 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
  • C08J3/2053—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the additives only being premixed with a liquid phase
• • 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
• • 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
  • C08J2307/00—Characterised by the use of natural rubber
  • C08J2307/02—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
  • C08J2407/00—Characterised by the use of natural rubber
  • C08J2407/02—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
  • C08J2409/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08J2409/10—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
  • C08J2415/00—Characterised by the use of rubber derivatives
  • C08J2415/02—Rubber derivatives containing halogen
• • 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
  • C08J2421/00—Characterised by the use of unspecified rubbers
  • C08J2421/02—Latex
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• the invention relates to the preparation of a masterbatch of natural rubber and silica comprising at least one silica (modified) and a natural rubber latex.
• 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.
• this filler 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 filler to be present in the elastomeric matrix under final form that is both finely divided possible and distributed in the most homogeneous way possible.
• 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.
• 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. Therefore, it appears advantageous to use, in tire tread rubber compositions, silicas with a high specific surface area, possibly greater than that conventionally used, of the order of 160 m 2 / g, in particular to improve the wear resistance of these treads. Nevertheless, the dispersibility of the charge and the increase in its specific surface area are considered as antinomic features. Indeed, a large specific surface area implies an increase in the interactions between charge objects, and therefore a poor dispersion thereof in the elastomeric matrix and a difficult implementation.
• 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 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”.
• slurry aqueous dispersion of the filler
• the contacting of the elastomer latex and the slurry does not allow coagulation in the liquid medium, coagulation which should allow to obtain a solid which after drying, results in obtaining the masterbatch of elastomer and silica desired.
• 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 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 natural rubber 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 natural rubber latex is a concentrated latex of natural rubber.
• the silica is a precipitated silica.
• the formulation pH is greater than or equal to 8.5 and the magnesium doping rate of the silica is greater than or equal to 0.4% by weight.
• the invention also relates to a masterbatch of natural rubber and silica prepared according to the method which comprises the following successive stages:
• the subject of the invention is also a rubber composition based on at least one masterbatch of natural rubber and 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.
• silica the silica with magnesium, the fact of modifying the surface of the silica so as to integrate the magnesium in the mesh of the outer layers of the silica and / or on the surface of this silica.
• silica “doped” magnesium a silica having magnesium in the mesh of its peripheral layers and / or on its surface.
• This method is used to determine the surface magnesium of doped silicas by atomic emission spectrometry (ICP-AES). These silicas are prepared by doping with a commercial silica.
• % HN0 3 65 - concentrated sulfuric acid (ex: RP MERCK EF 1.00731.1000)
• 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 control is prepared in each series of measurements in the same manner as the above standards by introducing 1.0 ml of 1000 mg / l magnesium standard solution of a different batch. It validates the calibration. The verification cookie does not keep after use. d) -4- ICP-AES Assay:
• Validation indicator (theoretical value: 10 mg / 1)
• Verification standard E4 (theoretical value: 20mg / l)
• Plasma and nebulization settings Plasma and nebulization settings:
• Spray chamber cyclonic type (Scott chamber) - Pump speed: 20 rpm
• Plasma gas flow 12 1 / min
• Sheathing gas flow rate 0.2 1 / min
• the surface magnesium content of the sample (in mass%):
• 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 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
• B represents the percentage of organic matter (range 250-550 ° C)
• C the percentage of intermediate losses (between 550 and 750 ° C)
• D 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 natural rubber and silica according to the invention comprises the following successive steps:
• magnesium silica is doped.
• 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 magnesium 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 the company Degussa
• the silicas Zeosil 1165MP, 1135MP and 1115MP from the company Rhodia from the company Rhodia
• the silica Hi-Sil EZ150G from PPG from the Zeopol 8715, 8745 and 8755 silicas from Huber
• the high surface area silicas as described in WO 03/16837.
• 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" For example, 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). It may be useful to add to this aqueous dispersion of doped silica, 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.
• an acidifying agent such as strong acids or weak acids
• the elastomer latex is a particular form of elastomer which is in the form of elastomer particles dispersed in water.
• Natural rubber exists in various forms, as detailed in Chapter 3, Latex concentrates: properties and composition, K.F. Gaseley, A.D.T. Gordon and TD Pendle in "Natural Rubber Science and Technology,” AD Roberts, Oxford University Press - 1988.
• latex field natural rubber latexes.
• the so-called “natural concentrated rubber rubber latex” the epoxy latex (“ENR")
• ENR epoxy latex
• Field natural rubber latex is a latex in which ammonia has been added to prevent premature coagulation and the concentrated natural rubber latex is a field latex which has been treated to a wash followed by a new concentration.
• the different categories of concentrated natural rubber latex are listed in particular according to ASTM D 1076-06.
• the latex can be used directly or be previously diluted in water to facilitate its implementation.
• 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.
• the pH, here named formulation pH of this new dispersion is measured according to the protocol described previously in the tests.
• the formulation pH is greater than or equal to 8.5 and the magnesium doping rate of the silica is greater than or equal to 0.4% by weight.
• condition (i) is the following: (i) the formulation pH is between 3 and 6 and the magnesium doping rate of the silica is between 0.25 and 0.25; and 0.9% by weight.
• the formulation pH is greater than or equal to 8.5 and the magnesium doping level of the silica is greater than or equal to 0.4% by weight. More particularly, the formulation pH is less than 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 ATG loading rate and the coagulation yield are measured.
• the masterbatches thus produced can be used in rubber compositions, in particular for tires.
• the level of magnesium present in the masterbatch can be limited by limiting the doping rate of the silica to 4.5% by weight.
• 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 to mean, in known manner, an agent capable of establishing a sufficient bond, of a chemical and / or physical nature, 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.
• carriers of alkoxyl functions i.e., by definition, "alkoxysilanes" as "Y” functions and, as "X” functions, functions capable of reacting with the diene elastomer such that for example polysulfide functions.
• TESPT bis 3-triethoxysilylpropyl tetrasulfide
• the coupling agent in the preparation of the masterbatch in order to directly obtain a masterbatch of elastomer and silica also comprising a coupling agent.
• the coupling agent can thus be added before or during the bringing into contact of the aqueous dispersion of doped silica and the natural rubber 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 preferential non-aromatic or very weakly aromatic plasticizing agent, at least one compound chosen from the group consisting of naphthenic, paraffinic, MES, TDAE, ester (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, covering agents (comprising, for example, the only Y function) of the reinforcing inorganic filler or, more generally, processing aid agents capable of in a known manner, by improving the dispersion of the inorganic filler in the rubber matrix and by lowering the the viscosity of the 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), primary, secondary or tertiary amines (for example trialkanol amines), hydroxylated or hydrolysable POSs, for example ⁇ , ⁇ -dihydroxy-polyorganosiloxanes (in particular ⁇ , ⁇ -dihydroxy-polydimethylsiloxanes), fatty acids such as, for example stearic
• compositions may in particular also contain, in addition to the masterbatch, one or more other diene elastomers.
• diene elastomers derived at least in part (ie, a homopolymer or a copolymer) from monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or otherwise ).
• 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 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 work mechanical (sometimes called a "productive" phase) at a lower temperature, typically less than 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 referred to as a "non-productive" phase
• a second phase of work mechanical sometimes called a "productive” phase
• all the basic constituents of the compositions of the invention with the exception of the vulcanization system, namely the masterbatch, the coupling agent (if it is not is not already present in the masterbatch) and the carbon black, if any, are intimately incorporated by mixing with the masterbatch during the so-called non-productive first phase, i.e. at least one of the various basic constituents is introduced into the mixer and mechanically kneaded in one or more steps until the maximum temperature of between 130 ° C. and 200 ° C. is reached, preferably 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, 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 vulcanization system itself is preferably based on sulfur and a primary vulcanization accelerator, in particular a sulfenamide type accelerator.
• a primary vulcanization accelerator in particular a sulfenamide type accelerator.
• various known secondary accelerators or vulcanization activators such as for example zinc oxide, fatty acids such as stearic acid, guanidine derivatives (in particular diphenylguanidine), etc.
• 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.
• 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 slurry thus sheared is introduced into the reactor and 2964.67 ml of demineralized water are added to obtain an initial silica concentration of 40 g / l, ie 3.8% w.
• the medium is stirred at 650 rpm and heated to 60 ° C. (control of the temperature of the medium using a temperature probe integrated into the electrode).
• the Mg (SO 4 ) 7H 2 O salt is added at 15 ml / min and the pH of the medium is adjusted to 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 demineralized water at a concentration of about 10% w.
• the measurement conditions 160 ° C without temperature ramp, duration of 30 minutes
• the taring of the magnesium cup about 2.5 g of sample are introduced into the cup and start the measurement.
• the protocol to be followed for different doping levels is identical with the exception of the amount of magnesium precursor salt to be introduced as summarized in Table 1 which follows in which appear the amounts of magnesium salt used according to the doping levels referred.
• the magnesium-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 charge rate.
• 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 under vacuum in an oven for 24 hours at 65 ° C. under 300mbar in order to remove the last traces of water.
• the ATG loading rate and the coagulation yield are then measured.
• 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 at a given doping rate of the silica.
• 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 at a given doping level different from Example 1.
• tests ⁇ , E'2 and E'3 are distinguished from each other by their formulation pH when the dispersions (aqueous dispersion of silica and elastomer latex) are brought into contact as follows:

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