Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • 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
• • 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
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • 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
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/04—Ingredients treated with organic substances
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
  • C08L25/04—Homopolymers or copolymers of styrene
  • C08L25/08—Copolymers of styrene
  • C08L25/10—Copolymers of styrene with conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons

Definitions

• the present invention relates to diene rubber compositions which can be used for the manufacture of tires or semi-finished products for tires, in particular treads for these tires, as well as to reinforcing fillers capable of reinforcing such rubber compositions.
• compositions reinforced with silica Since the publication of this application EP-A-0 501 227, the interest in compositions reinforced with silica has been very largely revived. However, silicas are generally more difficult to disperse than carbon blacks. On the other hand, the compositions loaded with silica, compared with those loaded with carbon black, have in known manner the drawback of having on the one hand an implementation (ie an aptitude for transformation or "processabihty") in the more difficult raw state, on the other hand a very high electrical resistance.
• compositions having both improved hysteresis and adhesion properties, but also easy processing in the raw state, a high level of reinforcement, and therefore of wear resistance, as well as conductivity high electric power were therefore highly desirable for tire manufacturers.
• the Applicant discovered during its research a new composition which, thanks to a particular reinforcing filler, makes it possible, unexpectedly, to meet these different contradictory requirements.
• a first subject of the invention relates to a sulfur-vulcanizable rubber composition which can be used for the manufacture of tires, comprising at least one diene elastomer, a reinforcing filler and a coupling agent ensuring the connection between the reinforcing filler and the elastomer, this composition being characterized in that said reinforcing filler consists entirely or partly of a so-called "modified" carbon black having the following characteristics:
• compositions of the invention thanks to this modified black and to its specific combination of characteristics, in particular its particular surface properties, have not only improved hysteresis and adhesion properties, but also a high electrical conductivity.
• Rubber compositions comprising as reinforcing filler carbon blacks with modified surface, covered with a siliceous layer, have certainly been described in recent patent applications (see for example EP-A-0 711 805, EP-A -0 799 854, EP-A-0 799 867, WO96 / 037547); these new compositions and their potential for application in tires are still poorly understood by tire manufacturers.
• the compositions of the invention have at least the notable advantage that the aluminous surface layer deposited on the surface of their reinforcing filler, made of oxides and / or aluminum hydroxides which, in known manner, are more stable and chemically more reactive than silicon oxides, will therefore be more adherent to black particles and more reactive than a siliceous layer can be.
• the compositions of the invention have the advantage of having an implementation in the raw state which is facilitated.
• Patent application WO97 / 42256 describes diene rubber compositions which can incorporate, as reinforcing filler, carbon blacks treated directly in the reactor for synthesizing carbon black with various metal compounds, especially in the form of '' oxides, hydroxides or carbides of different metals (e.g. aluminum, zinc, magnesium, calcium, titanium, vanadium, cobalt, nickel, zirconium, tin, antimony, chromium, neodymium, lead, tellurium, barium, cesium, iron , molybdenum).
• metal compounds especially in the form of '' oxides, hydroxides or carbides of different metals (e.g. aluminum, zinc, magnesium, calcium, titanium, vanadium, cobalt, nickel, zirconium, tin, antimony, chromium, neodymium, lead, tellurium, barium, cesium, iron , molybdenum).
• the blacks thus treated at very high temperature in the synthesis reactor consist in fact of aggregates or hybrid particles in two phases, formed by an intimate mixture of carbon black and metallic compound, the metallic compound being located both inside and near the surface of the aggregates; it is specified in particular that the metal atom content can reach 50% or even 99% of the mass of the final aggregate (% by mass).
• hybrid charges if they were released by any means from their fraction of metallic compound, for example by an appropriate chemical treatment, would have neither the morphology nor the properties of a conventional carbon black, but those of carbonaceous residues with high porosity.
• the treated carbon blacks described in WO97 / 42256 should not be confused with carbon blacks only coated with a layer of metallic compound which, after elimination of such a coating, would find their initial structure.
• a subject of the invention is also the use of a rubber composition in accordance with the invention for the manufacture of rubber articles, in particular tires or semi-finished rubber products intended for these tires, these semi articles -finishes being chosen in particular from the group consisting of treads, underlayments intended for example to be placed under these treads, crown plies, sides, carcass plies, heels, protectors, chambers air or waterproof inner rubber for tubeless tires.
• the invention relates more particularly to the use of such a rubber composition for the manufacture of sidewalls or treads, due to its good hysteretic properties.
• the subject of the invention is also these tires and these rubber articles themselves when they comprise a rubber composition in accordance with the invention.
• composition in accordance with the invention is particularly suitable for making tire treads intended to equip passenger vehicles, vans, two wheels and heavy goods vehicles, airplanes, civil engineering, agrarian or handling vehicles, these treads which can be used in the manufacture of new tires or for retreading used tires.
• FIG. 1 a diagram of a device capable of measuring the ultrasonic disaggregation speed ( ⁇ ) of a charge in the form of agglomerates (fig. 1);
• the reinforcing fillers used are characterized as indicated below.
• the BET specific surface is determined in a known manner, 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 AFNOR-NF-T45-007 (November 1987).
• the average size (by mass) of the particles is conventionally measured after dispersion, by ultrasonic deagglomeration, of the feed to be analyzed in an aqueous solution containing 15% ethanol and 0.05% of a nonionic surfactant (% by volume).
• particle used in the present application must be understood in its usual generic sense of aggregate, and not in that of any elementary particle which may form part of this aggregate (by aggregate, we must understand in a known manner an indivisible whole of elementary particles, produced during the synthesis of the charge).
• the deagglomeration speed noted ⁇ is measured in the test called “ultrasonic deagglomeration test", at 10% power of a 600 watt probe.
• This test makes it possible to continuously measure the change in the size of the particle agglomerates during a sonification, according to the indications below.
• the assembly used consists of a laser granulometer (type “Mastersizer S”, sold by Malvern Instruments - He-Ne laser source emitting in the red, wavelength 632.8 nm) and its preparer ("Malvern Small Sample Unit MSX1 "), between which was inserted a continuous flow treatment cell (Bioblock M72410) fitted with an ultrasound probe (1/2 inch sonicator type Vibracell of 600 watts sold by the company Bioblock).
• a small amount (15 mg) of filler to be analyzed is introduced into the preparer with 160 ml of an aqueous solution containing 20% by mass of ethanol, the circulation speed being fixed at its maximum. At least three consecutive measurements are made to determine according to the known Fraunhofer calculation method (Malvern calculation matrix 3 $$ D) the initial mean diameter (by volume) of the agglomerates, denoted d v [0]. The sonication is then established at a power of 10% (ie 10% of the maximum position of the "tip amplitude") and the evolution of the mean diameter in volume d v [t] as a function of time is followed for approximately 8 minutes " t "at a rate of approximately every 10 seconds.
• Fraunhofer calculation matrix 3 $$ D the initial mean diameter (by volume) of the agglomerates
• FIG. 1 shows schematically an example of mounting of the measuring device usable for carrying out this ultrasonic disaggregation test.
• This device consists of a closed circuit 1 in which a flow 2 of agglomerates of particles in suspension in a liquid can circulate.
• This device essentially comprises a sample preparer 10, a laser granulometer 20 and a processing cell 30.
• the sample processor 10 (“Malvern Small Sample Unit MSX1”) is intended to receive the charge sample to be tested (as it is or already in suspension in the liquid 3) and to send it through the circuit 1 to a speed set (potentiometer 17), in the form of a flow 2 of liquid suspension.
• This preparer 10 simply consists of a receiving tank which contains, and through which circulates, the suspension to be analyzed.
• the preparer 10 is connected to a laser granulometer 20 ("Mastersizer S") whose function is to continuously measure, at regular time intervals, the average size "d v " of the agglomerates, as flow 2 passes, using a cell 23 to which are coupled the automatic recording and calculation means of the particle size analyzer 20.
• Mastersizer S a laser granulometer 20
• laser particle size analyzers exploit, in known manner, the principle of light diffraction by solid objects suspended in a medium whose refractive index is different from that of the solid. According to Fraunhofer's theory, there is a relationship between the size of the object and the angle of diffraction of light (the smaller the object, the larger the angle of diffraction).
• a treatment cell 30 Interposed between the preparer 10 and the laser granulometer 20 is finally a treatment cell 30 equipped with an ultrasonic probe 35 (converter 34 and probe head 36) intended to continuously break up the agglomerates of particles as flow 2 passes.
• an ultrasonic probe 35 (converter 34 and probe head 36) intended to continuously break up the agglomerates of particles as flow 2 passes.
• the treatment cell 30 is placed between the outlet 22 of the particle sizer 20 and the inlet 11 of the preparer 10, in such a way that, in operation, the flow 2 of particles leaving the preparer 10 first passes through the laser granulometer 20 before entering the treatment cell 30.
• This arrangement has two major advantages for the measurements: on the one hand, the air bubbles due to the action of the ultrasonic probe are eliminated on passing through the preparer 10 (which is in the open air), that is to say before entering the granulometer 20; they therefore do not disturb the measurement of laser diffraction; on the other hand, the homogeneity of the suspension is improved by prior passage through the preparer 10.
• the treatment cell 30 is preferably arranged in such a way that the flow 2 of particles which enters it, via an inlet 31, passes first in front of the head 36 of the ultrasonic probe 35;
• this unconventional arrangement (flow 2 enters from the bottom 31 of the cell, and not from the top 32) has the following advantages: on the one hand, all of the circulating suspension 2 is forced to pass in front of the end 36 of the ultrasound probe 35, the most active area in terms of deagglomeration; on the other hand, this arrangement allows a first degassing after sonification in the body of the treatment cell 30 itself, the surface of the suspension 2 then being in contact with the atmosphere by means of a pipe 33 of small diameter .
• the flow 2 is preferably thermostatically controlled by means of a cooling circuit 40 disposed, at the level of the cell 30, in a double envelope surrounding the probe 35, the temperature being controlled for example by a temperature probe 14 immersed in the liquid 3 at the level of the preparer 10.
• the arrangement of the various elements of the measuring device is optimized so as to limit as much as possible the circulating volume, that is to say the length of the connection pipes (for example flexible pipes ). 1-2. Characterization of rubber compositions
• Hysteretic losses are measured by rebound at 60 ° C on the 6th shock, and expressed in% according to the following relationship:
• PH (%) 100 [(W 0 -Wt) / W 0 ], with W 0 : energy supplied; Wt: energy returned.
• the dynamic properties, noted ⁇ G * and tan ( ⁇ ) max , measured as a function of the deformation, are carried out at 10 Hertz with a peak-peak deformation ranging from 0.15% to 50%.
• the non-linearity ⁇ G * is the difference in shear modulus between 0.15% and 50% of deformation, expressed in MPa.
• the hysteresis is expressed by the measurement of tan ( ⁇ ) max which corresponds to the maximum of tan ( ⁇ ).
• compositions according to the invention comprise as basic constituents at least one diene elastomer, a reinforcing filler and an agent. coupling between the reinforcing filler and the elastomer, said reinforcing filler being made up wholly or partly of a modified carbon black as described in detail below.
• iene elastomer or rubber in known manner an elastomer derived at least in part (i.e. a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).
• diene elastomer a diene elastomer derived at least in part from conjugated diene monomers, having a rate of units or units of diene origin (conjugated dienes) which is greater than 15% (% in moles).
• diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not enter into the preceding definition and can be qualified in particular as "essentially saturated diene elastomers". "(rate of motifs of diene origin low or very low, always less than 15%).
• the expression “highly unsaturated” diene elastomer is understood in particular to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
• 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C1-C5 alkyl) -1,3-butadienes such as, for example, are suitable.
• Suitable vinyl-aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tertiobutylstyrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene. , vinylnaphthalene.
• the copolymers can contain between 99% and 20% by weight of diene units and from 1% to 80% by weight of vinyl aromatic units.
• the elastomers can 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 quantities of modifying and / or randomizing agent used.
• the elastomers can be, for example, block, statistics, sequences, microsequences, be prepared in dispersion or in solution.
• polybutadienes are suitable and in particular those having a content of -1,2 units between 4% and 80% or those having a cis-1.4 content greater than 80%, polyisoprenes, butadiene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content of -1,2 bonds in the butadiene part of between 4% and 65%, a content of trans-1,4 bonds between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content between 5% and 90% by weight and a glass transition temperature (Tg) between -40 ° C and -80 ° C, isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between -25 ° C and -50 ° C.
• Tg glass transition temperature
• butadiene-styrene-isoprene copolymers especially those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15% and 60% are suitable.
• the elastomer can be coupled and / or star or functionalized with a coupling agent and / or star or functionalization.
• the elastomer can also be natural rubber or a blend based on natural rubber with any elastomer, especially diene, synthetic.
• the diene elastomer of the composition in accordance with the invention is chosen from the group of highly unsaturated diene elastomers constituted by polybutadienes, polyisoprenes or natural rubber, butadiene-styrene copolymers, butadiene copolymers -isoprene, isoprene-styrene copolymers, butadiene-styrene-isoprene copolymers, or a mixture of two or more of these compounds.
• the diene elastomer is preferably a butadiene-styrene copolymer prepared in solution having a styrene content of between 20% and 30% by weight, a content of vinyl bonds in the butadiene part of between 15% and 65%, a content of trans-1,4 bonds between 20% and 75% and a glass transition temperature between -20 ° C and -55 ° C, this butadiene-styrene copolymer being optionally used in admixture with a polybutadiene preferably having more than 90% of cis-1,4 bonds.
• composition according to the invention is reinforced, at least in part, with a carbon black with modified surface, called “modified carbon black” or “modified black”, having the following characteristics:
• aluminum oxide and / or hydroxide any aluminum compound corresponding, apart from impurities and water of hydration, to the general formula (I) which follows (a and b real numbers):
• This formula is given with the exception of impurities, it being understood that the aluminum oxides and / or hydroxides present on the surface of the modified carbon black may contain a certain proportion of impurities linked to the process used for the manufacture of the filler.
• the intrinsic dispersibility of a charge can be evaluated using the so-called ultrasonic disagglomeration test described in chapter I above, by measuring its disagglomeration speed ⁇ .
• the modified black has good dispersibility. That is to say that few micron agglomerates are observed by reflection under optical microscopy on a section of prepared rubber composition. according to the rules of art.
• the deagglomeration speed ⁇ is particularly advantageous in particular when the invention is used for the manufacture of treads having low rolling resistance.
• the compositions certainly exhibit easier processing and reduced hysteresis, but there is a decline in the breaking properties and resistance to wear in tires; for BET surfaces greater than 400 m 2 / g, processing in the raw state becomes more difficult (higher Mooney plasticity) and the dispersion of the charge is degraded.
• BET surfaces greater than 400 m 2 / g processing in the raw state becomes more difficult (higher Mooney plasticity) and the dispersion of the charge is degraded.
• sizes d w greater than 400 nm, the particles behave like defects which localize the stresses and are detrimental to wear; sizes d w that are too small, less than 20 nm, on the other hand, will penalize the implementation in the raw state and the dispersion of the charge during this implementation.
• the BET surface is preferably within a range from 50 to 300 m 2 / g and the particle size d w is preferably within a range from 30 to 200 nm.
• the modified carbon black thanks to its aluminous surface layer, also exhibits a high surface reactivity, ie a high rate of reactive surface functions (Al-OH), vis-à-vis the coupling agent, which is particularly favorable to the mechanical properties of the rubber compositions of the invention, that is to say to the reinforcement function fulfilled by the filler.
• a high surface reactivity ie a high rate of reactive surface functions (Al-OH), vis-à-vis the coupling agent, which is particularly favorable to the mechanical properties of the rubber compositions of the invention, that is to say to the reinforcement function fulfilled by the filler.
• the aluminum content (of element Al) present on the surface of the modified carbon black is greater than 0.25%, more preferably greater than 0.5%, even more preferably adjusted in a range between 0.5% and 5% (% by mass of modified black, determined by chemical analysis).
• the effect of lowering the hysteresis may be insufficient, depending on the nature of the compositions used, in particular that of the elastomer, while beyond the maximum recommended rate, it is generally observed more improvement of the hysteresis whereas one is exposed to the risk of leading on the one hand to a too low dispersibility of the modified black, known drawback of white charges compared to carbon black, on the other hand a decrease in adhesion of the aluminous layer to the surface of the carbon black.
• a rate greater than 5% would also require larger quantities of precursor product (aluminum alkoxide) or even longer impregnation times during manufacture, which is economically less advantageous.
• the aluminum content be adjusted between 0.5% and 3%.
• the black modified above can be used alone or combined with another reinforcing filler, for example with a reinforcing silica; in such a case, a highly dispersible precipitated silica is preferably used, in particular when the invention is implemented for the manufacture of tires having a low rolling resistance.
• a highly dispersible precipitated silica is preferably used, in particular when the invention is implemented for the manufacture of tires having a low rolling resistance.
• preferred highly dispersible silicas mention may be made of Perkasil KS 430 silica from Akzo, BV3380 silica from Degussa, Zeosil 1165MP and 1115MP silica from Rhône-Poulenc, Hi-Silica 2000 from PPG, Zeopol 8741 or 8745 from Huber.
• modified black alone or possibly combined with silica, can also be used in cutting, i.e. in admixture, with conventional carbon black.
• the modified black constitutes the majority, i.e. more than 50% by weight, of the total reinforcing filler; it can advantageously constitute the entire reinforcing filler.
• the rate of total reinforcing filler in the compositions of the invention is within a range ranging from 20 to 300 phr, more preferably from 30 to 150 phr. the optimum being different depending on the intended applications: in known manner, the level of reinforcement expected on a bicycle tire, for example, is much lower than that required on a tire for a passenger vehicle or for a utility vehicle such as a heavy vehicle.
• the modified carbon black can be obtained according to the following process:
• the reinforcing carbon blacks conventionally used in tires are suitable, particularly in the treads of these tires, in particular blacks of the HAF ("High Abrasion Furnace"), ISAF ("Intermediate Super Abrasion Furnace”) type. “), SAF ("Super Abrasion Furnace ").
• HAF High Abrasion Furnace
• ISAF Intermediate Super Abrasion Furnace
• SAF Super Abrasion Furnace
• the reinforcing carbon blacks of the 100, 200 or 300 series ASTM grades.
• these starting carbon blacks have the following characteristics:
• BET surface area between 20 and 200 m 2 / g, more preferably between 50 and 170 m 2 / g;
• an average size (by mass) of particles d w of between 20 and 400 nm, more preferably between 30 and 200 nm.
• colloidal suspension in known manner a suspension of solid phase in a liquid whose size of solid objects is less than one micrometer.
• the aluminum alkoxide is dissolved, with stirring and at temperature, in the selected alcohol, for example methanol, ethanol, (iso) propanol, the various isomers of butanol. , then the whole is hydrolyzed by adding water.
• the aluminum alkoxide used is preferably an aluminum alkoxide having from 1 to 6 carbon atoms, for example a methoxide, an ethoxide, an (iso) propoxide or aluminum butoxides, or a mixture of two or more of these compounds.
• the impregnation step can be carried out at room temperature (20 ° C) or at a higher temperature, for example between 30 ° C and 65 ° C depending on the nature of the alcohol or alcohols used, of course below the boiling point of the suspension, it being understood that the chosen temperature may be close to this boiling point.
• the duration of impregnation is chosen to be sufficiently long, from a few minutes to a few hours depending on the case, in order to create sufficient physicochemical interactions between the surface of the carbon black and the aluminum-based compound.
• the colloidal impregnation suspension comprises nitric acid used both as a catalyst for hydrolysis of the alkoxide solution and as a peptizing agent for the colloidal suspension.
• nitric acid used both as a catalyst for hydrolysis of the alkoxide solution and as a peptizing agent for the colloidal suspension.
• the nitric acid will be removed by washing the impregnated black with water.
• the elimination of the alcoholic solvent, after impregnation of the carbon black can be carried out by any suitable means, for example by evacuation under vacuum, with stirring.
• the heat treatment step is preferably carried out under inert gas, for example under argon, the treatment temperature preferably being between 100 ° C. and 900 ° C., more preferably between 150 ° C. and 850 ° C.
• the higher this treatment temperature the more the formula (I) defined above "moves" from the hydroxide to the oxide (decrease in a and increase in b); treatment at a temperature of 800-850 ° C, for example, will lead to an aluminous layer essentially consisting of alumina (Al 2 O 3 ).
• a coupling agent (silica / elastomer), also called bonding agent, which has the function of ensuring the bond between the white filler and the elastomer, while facilitating the dispersion of this white filler within the elastomeric matrix.
• Modified black because of its aluminous surface layer, also requires the use of such a coupling agent to fully ensure its function of reinforcing filler in the rubber composition according to the invention.
• coupling agent filler / elastomer
• a coupling agent is meant more precisely an agent capable of establishing a sufficient connection, of chemical and / or physical nature, between the filler considered and the elastomer, while facilitating the dispersion of this filler within the elastomeric matrix;
• a coupling agent at least bifunctional, has for example as simplified general formula "Y-T-X", in which:
• Y represents a functional group ("Y" function) which is capable of physically and / or chemically binding to the white charge, such a bond being able to be established, for example, between a silicon atom of the coupling agent and the hydroxyl (OH) groups on the surface of the filler (for example surface silanols when it is silica);
• X represents a functional group ("X" function) capable of binding physically and / or chemically to the elastomer, for example via a sulfur atom;
• T represents a hydrocarbon group making it possible to link Y and X.
• Coupling agents should in particular not be confused with simple agents for recovering the charge considered which, of known mother, comprise the active Y function with respect to the charge but are devoid of the active X function vis- against the elastomer.
• any coupling agent known to effectively can be used in diene rubber compositions which can be used for the manufacture of tires the bond or coupling between silica and diene elastomer, such as organosilanes, in particular polysulphurized alkoxysilanes such as polysulphides , in particular tetrasulfides, of bis (trialkoxyl (C 1 -C) -silylpropyl), in particular of bis (3-trimethoxysilylpropyl) or of bis (3-triethoxysilylpropyl).
• organosilanes in particular polysulphurized alkoxysilanes such as polysulphides , in particular tetrasulfides, of bis (trialkoxyl (C 1 -C) -silylpropyl), in particular of bis (3-trimethoxysilylpropyl) or of bis (3-triethoxysilylpropyl).
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• Si69 bis (3-triethoxysilylpropyl) tetrasulfide
• the optimal level of coupling agent, for the modified black in moles per square meter of modified black, calculated from the weight ratio [coupling agent / modified black], of the BET surface area of the modified black and of the molar mass of the coupling agent (noted below), according to the following relation:
• silica if it is used as additional reinforcing white filler, to also determine the optimal rate of additional coupling agent for this silica, in moles per square meter of this filler white.
• the (total) amount of coupling agent used in the compositions in accordance with the invention is between 10 -7 and 10 " 5 moles per square meter of [modified carbon black plus, if appropriate, associated reinforcing white filler More preferably still, the amount of coupling agent is between 5.10 ' 7 and 5.10 " 6 moles per square meter of [modified carbon black plus, if necessary, associated reinforcing white filler].
• compositions in accordance with the invention contain, in addition to the compounds already described, all or part of the constituents usually used in diene rubber compositions intended for the manufacture of tires, such as for example plasticizers, pigments, antioxidants, antiozonants, a cross-linking system based either on sulfur or on donors of sulfur and / or peroxide and / or bismaleimides, vulcanization accelerators, extension oils, etc.
• compositions in accordance with the invention could also contain, in addition to the coupling agents described above, covering agents for white filler, such as for example alkylalkoxysilanes, polyols, amines.
• covering agents for white filler such as for example alkylalkoxysilanes, polyols, amines.
• the rubber compositions are prepared using the diene polymers according to quite known techniques, for example by thermomechanical work in one or two stages in an internal paddle mixer, followed by mixing on an external mixer.
• a conventional one-step process all the necessary constituents, with the exception of the vulcanization system, are introduced into a conventional internal mixer, for example.
• the result of this first mixing step is then taken up on an external mixer, generally a roller mixer, and the vulcanization system is then added to it.
• a second step can be added to the internal mixer, essentially for the purpose of subjecting the mixture to an additional heat treatment.
• the carbon black is then placed in a tabular oven (Carbolite CTF 15/75 610 type sold by the company Osi), under a flow of argon (200 ml / min), then subjected to the following thermal cycle: 30 min at 200 ° C, then 1 hour at 800 ° C; the temperature ramps are set at 10 ° C / min.
• a tabular oven Carbolite CTF 15/75 610 type sold by the company Osi
• the disagglomeration speed ⁇ is much higher than the fixed lower limit of 1.10 -3 ⁇ Os (i.e. 2/3 of ⁇ 0 ).
• a speed ⁇ of 3.1.10- 3 ⁇ nr 1 / s should be considered here as particularly high, since it is approximately 100% higher than the speed ⁇ 0 recorded on a highly dispersible control silica (Zeosil 1165MP).
• compositions tested below are prepared in a known manner in laboratory mixers, as follows: the diene elastomer is introduced into an internal mixer filled to 75% and whose temperature is about 70 ° C, then after an appropriate mixing time, for example of the order of 1 minute, all the other ingredients are added, including the filler and, if appropriate, the associated coupling agent, with the exception of the vulcanization system. Thermomechanical work is then carried out for a duration of approximately 5.5 minutes, with an average speed of the pallets of 70 revolutions / min, until a drop temperature of approximately 140 ° C. is obtained. The mixture thus obtained is recovered and then the vulcanization system is added on an external mixer (homo-finisher) at 30 ° C. Vulcanization is carried out at 150 ° C (40 min).
• the SBR elastomer (styrene-butadiene copolymer) is prepared in solution and comprises 25% of styrene, 58% of 1-2 polybutadiene units and 23% of 1-4 trans polybutadiene units.
• compositions are identical except for the following differences:
• composition Nol composition (control) conventional reinforcing filler constituted by a carbon black type N234
• - composition No2 in accordance with the invention: reinforcing filler constituted exclusively by carbon black N234 modified, with which the coupling agent Si69 (TESPT) is associated.
• the Si69 coupling agent was introduced at a rate corresponding to a surface coverage of approximately 9.6 ⁇ 10 -7 mole / m 2 of modified carbon black.
• Tables 2 and 3 successively give the formulation of the different compositions (Table 2 - rate of the different products expressed in phr), their properties before and after cooking at 150 ° C for 40 minutes (Table 3).
• the Mooney plasticity value appears lower on the composition in accordance with the invention than on the control composition, a result which in any case reveals a very good ability to process the composition of the invention raw;
• the composition according to the invention has values of modules, in particular of modules M 100 and M300 indicators in a known manner of the quality of reinforcement, which are at least equal if not greater than those obtained on the control composition;
• composition in accordance with the invention also has very advantageous hysteretic properties, compared to those offered by conventional carbon black, with a very significant reduction in rebound losses (PH), non-linearity ⁇ G * and tan ( ⁇ ) max .
• compositions of the invention unexpectedly exhibit significantly improved hysteresis properties, without their properties of processing in the raw state and of reinforcement after cooking being affected.
• the specific process for preparing the modified black makes it possible to deposit, on the surface of the carbon black particles or aggregates, a fine, stable, highly adherent and distributed aluminous layer of relatively homogeneously (average particle size little modified but strong increase in the BET surface).
• Such a coating quality of its reinforcing filler could explain the unexpected performance of the rubber composition according to the invention, improved both compared to compositions reinforced with conventional carbon black (reduction in hysteresis) and compared to compositions reinforced with precipitated silica even highly dispersible (increased dispersibility; high electrical conductivity).
• compositions of the invention thus offer an interesting alternative to the use of conventional compositions loaded with carbon blacks or highly dispersible silicas, or even carbon blacks coated with a siliceous layer.
• Table 1

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• 1998
  • 1998-11-27 AU AU18761/99A patent/AU1876199A/en not_active Abandoned
  • 1998-11-27 CN CN 98813247 patent/CN1284099A/zh active Pending
  • 1998-11-27 EP EP98963524A patent/EP1034215A1/fr not_active Withdrawn
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