FR3029930A1 - FLANK FOR PNEUMATIC - Google Patents

Abstract

The invention relates to a tire sidewall having a rubber composition based on at least one blend of polyisoprene, synthetic rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler comprising carbon black and silica, a crosslinking system, characterized in that the reinforcing filler mainly comprises carbon black, the carbon black content ranges from 20 to 30 parts per hundred parts of elastomer, phr, and the silica content ranges from 1 to 7 and that the total level of reinforcing filler is less than or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a Z score greater than or equal to 75.

Description

The present invention relates to a tire sidewall based on a rubber composition, and more particularly for tires used in civil engineering. The flanks of the tires used for Civil Engineering represent about 15% of the total mass of the tires, thus a large mass, which when the tread is partially worn, has a very important impact on the rolling resistance of the tire. It is therefore interesting to try to reduce the hysteresis of the flanks of such tires in order to have an impact on the rolling resistance of these tires.

One of the ways to reduce the hysteresis is to lower the amount of reinforcing filler present in the flanks. However, it is known that the reduction of the reinforcing filler content generally leads to a deterioration of the mechanical properties such as fatigue resistance and boundary properties and reinforcement.

Indeed, the sidewalls of civil engineering tires are subjected to very strong stresses both in terms of bending deformation, aggression and thermal These prolonged static or dynamic stresses of the flanks in the presence of ozone, show cracks or cracks more or less marked whose propagation under the effect of the persistence of stresses can cause significant damage to the flank concerned. It is therefore important that the compositions constituting the tire sidewalls for civil engineering in particular have very good mechanical properties, and therefore generally with a high reinforcing filler content. The Applicants have surprisingly discovered, on the contrary, the knowledge of those skilled in the art that compositions lightly loaded with carbon black but having a very good dispersion of the filler in the elastomeric matrix, made it possible to obtain flanks presenting The invention therefore relates to a sidewall for a tire, having a rubber composition based on at least one polyisoprene, natural rubber or polyisoprene blend. synthesis, and polybutadiene BR, a reinforcing filler comprising carbon black and silica, a crosslinking system, characterized in that the reinforcing filler mainly comprises carbon black, that the carbon black content ranges from 20 to 30 parts per hundred parts of elastomer, phr, and the silica content is from 1 to 7 phr and that the total level of filler reinforces is less than or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a note Z greater than or equal to 75. According to one embodiment variant of the invention, the total rate of reinforcing filler is less than or equal to 33. pc. P10-3493 / SC 3029930 - 2 - Preferably, the carbon black content of the composition is less than or equal to 28 phr, more preferably less than or equal to 26 phr. The silica content is preferably from 2 to 5 phr.

Advantageously, the level of synthetic rubber or synthetic polyisoprene ranges from 20 to 80 phr and the level of BR ranges from 20 to 80 phr. According to one embodiment of the invention, the content of synthetic rubber or synthetic polyisoprene ranges from 50 to 80 phr. According to another embodiment of the invention, the level of BR ranges from 50 to 80 phr. According to one embodiment of the invention, the composition is obtained from a first masterbatch comprising at least polyisoprene and carbon black, and having a dispersion of carbon black in the elastomeric matrix having a Z-score greater than or equal to 90. In particular, the first masterbatch is obtained by liquid phase mixing from a polyisoprene latex and an aqueous carbon black dispersion. Preferably it is obtained according to the following process steps: feeding a continuous stream of a polyisoprene latex to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, supplying a continuous flow of a fluid comprising carbon black under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture, drying the coagulum obtained previously in order to recover the first masterbatch .

The invention also relates to a method for manufacturing a tire sidewall having a rubber composition based on at least one blend of polyisoprene, synthetic rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler comprising black of carbon and silica, a crosslinking system, characterized in that the reinforcing filler predominantly comprises carbon black, the carbon black content is from 20 to 30 parts per hundred parts of elastomer, pce, and the silica content ranges from 1 to 5 phr and the total amount of reinforcing filler is less than or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a Z score greater than or equal to 80, which comprises the following steps: P10-3493 / SC 3029930 - 3 - preparing a first masterbatch comprising at least polyisoprene and carbon black, and having a dispersion of the carbon black in the elastomeric matrix a With a Z mark greater than or equal to 90, incorporate the silica, the BR and the other constituents of the composition, except for the crosslinking system, into the first masterbatch in a mixer by thermomechanically kneading the mixture all the way through. to reach a maximum temperature of between 130 ° C. and 200 ° C., to cool the assembly to a temperature below 100 ° C., then to incorporate: the crosslinking system; Kneading the whole up to a maximum temperature below 120 ° C. The invention finally relates to a tire comprising a sidewall as described above, in particular a tire intended to equip civil engineering vehicles.

I. MEASUREMENTS AND TESTS USED The rubber compositions are characterized, before and after curing, as indicated below. Dispersion In a known manner, the charge dispersion in an elastomeric matrix can be represented by the note Z, which is measured, after crosslinking, according to the method described by S. Otto and Al in Kautschuk Gummi Kunststoffe, 58 Jahrgang, NR 7-8 / 2005, in accordance with ISO 11345. Calculation of the Z score is based on the percentage of area in which the charge is not dispersed ("% undispersed area") as measured by "disperGRADER +" apparatus supplied with its operating mode and "30 disperDATA" operating software by Dynisco according to the equation: Z = 100 - (% undispersed area) /0.35 The percentage of undispersed area is to him, measured by a camera observing the surface of the sample under an incident light at 30 °. Clear spots are associated with filler and agglomerates, while dark spots are associated with the rubber matrix; digital processing transforms the image into a black and white image, and allows the determination of the percentage of undispersed surface, as described by S. Oto in the aforementioned document. The higher the note Z, the better the dispersion of the filler in the elastomeric matrix (a score Z of 100 corresponding to a perfect dispersion and a Z 40 score of 0 to a mediocre dispersion). Consider that a note Z greater than or equal to 80 P10-3493 / SC 3029930 - 4 - corresponds to a surface having a very good dispersion of the charge in the elastomeric matrix. Tensile tests These tests make it possible to determine the elastic stress and the properties at break; those carried out on the cooked mixtures are made in accordance with the AFNOR-NF-T46-002 standard of September 1988. It is measured at a temperature of 100 ° C. ± 2 ° C., and under normal humidity conditions (50 ± 5%). relative humidity), according to the French standard NF T 40-101 10 (December 1979), the stresses at break (in MPa) and the elongations at break (in%) are also measured, the energy at break (Rupture energy) being the product of the breaking stress and elongation at break. The nominal secant modulus (or apparent stress, in MPa) at 100% elongation (denoted MA100) and at 300% elongation (denoted MA300) is also measured at a temperature of 23 ° C. ± 2 ° C. Dynamic Property The tan (8) max dynamic property is measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 4 mm in thickness and 400 mm 2 in section), subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz and at a temperature of 60 °, is recorded. C, according to ASTM D 1349-99. A strain amplitude sweep of 0.1 to 50% (forward cycle) followed by 50% to 0.1% (return cycle) is carried out. The result exploited is the loss factor (tan 6). For the return cycle, the maximum value of tan 6 observed (tan (8) max) is given between the values at 0.1% and at 50% of deformation (Payne effect). Fatigue test Fatigue resistance, expressed as cycle number or relative unit (ur), is measured in a known manner on 12 test pieces subjected to repeated low frequency repetitions up to an elongation of 75%, at 23 ° C. ° C, using a Monsanto device ("MFTR" type) until the test piece breaks, according to ASTM D4482-85 and ISO 6943. The result is expressed in relative units (ur). A value greater than that of the control, arbitrarily set at 100, indicates an improved result, i.e., improved fatigue strength of the rubber samples. DETAILED DESCRIPTION OF THE INVENTION In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight. On the other hand, any range of values referred to as "between a and b" represents the range of values from more than a to less than b (i.e., terminals a and b excluded) while any range of values designated by the expression "from a to b" means the range from a to b (i.e., including the strict limits a and b).

Diene Elastomer By elastomer or "diene" rubber, it is to be understood in a manner known to mean one or more elastomers derived at least in part (ie, a homopolymer or a copolymer) from monomers dienes (monomers carrying two double bonds 15 carbon-carbon conjugated or unconjugated). These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". The term "essentially unsaturated" is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%). ; Thus, 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 "essentially saturated" diene elastomers ( units of diene origin 25 low or very low, always less than 15%). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

As these definitions are given, the term "diene elastomer" can be understood more particularly to mean the compositions in accordance with the invention: (a) - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms ; (B) - any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having 8 to 20 carbon atoms; (c) - a ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, for example elastomers obtained with starting from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene; (d) - a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

Although it applies to any type of diene elastomer, one skilled in the art of the tire will understand that the present invention is preferably carried out with essentially unsaturated diene elastomers, in particular of the type (a) or ( b) above.

The abovementioned 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 be, for example, block, random, sequenced or microsequential, and may be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization. For coupling with carbon black, there may be mentioned, for example, functional groups comprising a C-Sn bond or amine functional groups such as aminobenzophenone for example; for coupling to a reinforcing inorganic filler such as silica, there may be mentioned, for example, silanol or polysiloxane functional groups having a silanol end (as described, for example, in FR 2 740 778 or US Pat. No. 6,013,718, and WO 2008/141702). ), alkoxysilane groups (as described for example in FR 2,765,882 or US 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US Pat. 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). Functional elastomers that can also be mentioned are those prepared by the use of a functional initiator, in particular those carrying an amine or tin function (see, for example, WO 2010072761).

As other examples of functionalized elastomers, there may also be mentioned elastomers (such as SBR, BR, NR or IR) of the epoxidized type. The elastomeric matrix of the composition in accordance with the invention comprises at least: synthetic rubber, NR, or synthetic polyisoprene, preferably with a content preferably ranging from 20 phr to 80 phr, of BR, preferably with a rate ranging from 20 to 80 phr. It will be understood that by natural rubber or synthetic polyisoprene, it may be only one of these elastomers or a blend of natural rubber and one or more synthetic polyisoprene. P10-3493 / SC 3029930 - 7 - Similarly, when speaking of BR, this may be one or more polybutadienes. According to one embodiment of the invention, the level of synthetic rubber or synthetic polyisoprene ranges from 50 to 80 phr, and preferably, the level of BR ranges from 30 to 50 phr. According to another embodiment of the invention, the level of BR ranges from 50 to 80 phr. As BR, are suitable BR having a rate (mol%) of cis-1,4 chains greater than 90%. According to one embodiment of the invention, the composition comprises at least one other diene elastomer, preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), Copolymers of isoprene-styrene (SIR) and copolymers of isoprene-butadiene-styrene (SBIR). More preferentially, this other diene elastomer is constituted by an SBR with a content preferably ranging from 10 to 30 phr, whether it be an emulsion prepared SBR ("ESBR") or a solution-prepared SBR (" SSBR "), or a blend (blend) of 20 SBR / BR, SBR / NR (or SBR / IR), BR / NR (or BR / IR), or SBR / BR / NR (or SBR / BR / IR) . The composition according to the invention may contain another diene elastomer. The diene elastomers of the composition may be used in combination with any type of synthetic elastomer other than diene, or even with polymers other than elastomers, for example thermoplastic polymers. In order to obtain a very good dispersion of the reinforcing filler in the elastomeric matrix according to the invention, it is particularly advantageous to use a masterbatch of diene elastomer and reinforcing filler made in the "liquid" phase. To do this, an elastomer in the form of latex has been used in the form of elastomer particles dispersed in water, and an aqueous dispersion of the filler, that is to say a dispersed filler. in water, commonly called "slurry". Certain processes in particular, such as those described in US Pat. No. 6,048,923, make it possible to obtain a masterbatch of elastomer and filler having a very good dispersion of the filler in the elastomeric matrix, which is greatly improved with respect to the dispersion of the filler in the elastomeric matrix that can be obtained during the solid-phase mixing of elastomer and reinforcing filler. This process includes incorporating a continuous flow of a first elastomer latex fluid into the mixing zone of a coagulation reactor, incorporating a second continuous flow of elastomeric latex. a second fluid consisting of an aqueous charge dispersion under pressure in the mixing zone to form a mixture with the elastomer latex; the mixing of these two fluids being sufficiently energetic to allow the elastomer latex to be almost completely coagulated with the filler before the exit orifice of the coagulation reactor and then to dry the obtained coagulum. This process is particularly suitable for producing a masterbatch having a very good dispersion, from a natural rubber latex and carbon black. Indeed, the application of this process is made particularly favorable by the ability of the natural rubber latex and the carbon black to coagulate together spontaneously. Conversely, the silica does not coagulate spontaneously with the natural rubber latex because the silica aggregates are typically hydrophilic in nature and have more affinity with water than with the elastomer particles themselves. As mentioned above, the liquid phase mixing processes are preferably used to obtain masterbatches based on diene elastomer and carbon black having a very good dispersion of carbon black in the elastomer. Thus, in particular for the production of the first masterbatch of diene elastomer and of carbon black, a diene elastomer latex will more particularly be used, the elastomer latex being a particular form of the elastomer which is in the form of elastomer particles dispersed in water. The invention therefore preferably relates to diene elastomer latices, the diene elastomers being those defined above.

More particularly, for natural rubber (NR) which is particularly suitable for the invention, this natural rubber exists in various forms as detailed in Chapter 3, Latex concentrates: properties and composition, K.F. Gaseley, A.D.T. Gordon and T. D. Pendle in "Natural Rubber Science and Technology", A. D. Roberts, Oxford University Press - 1988.

In particular, several forms of natural rubber latex are commercially available: so-called "field latex" natural rubber latexes, "natural latex" rubber latex, latex epoxidized ("ENR"), deproteinized latex or prevulcanized latex. Field natural rubber latex is a latex in which ammonia has been added to avoid early 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. Among these concentrated natural rubber latexes, there are in particular concentrated natural rubber latexes 40 of quality called "HA" (high ammonia) and quality called "LA"; P10-3493 / SC 3029930 will advantageously be used for the invention of concentrated natural rubber latexes of HA quality. The NR latex can be modified beforehand physically or chemically (centrifugation, enzymatic treatment, chemical modification, etc.). The latex can be used directly or be diluted beforehand in water to facilitate its use. Thus, using synthetic elastomer latex, the latex can consist in particular of a synthetic diene elastomer already available in the form of an emulsion, or of a synthetic diene elastomer initially in solution which is emulsified in a mixture of organic solvent and Water, generally by means of a surfactant Reinforcing filler A known filler means a filler known for its ability to reinforce a rubber composition which can be used for the manufacture of tires. Among these reinforcing fillers are organic fillers, such as carbon black and inorganic fillers.

Suitable carbon blacks are all carbon blacks, especially blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks). Among these, the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), for example the N115, N134, N234, N326, N330, N339, N347 or N375 blacks, or else, according to the targeted applications, the blacks of higher series (for example N400, N660, N683, N772, N990). As carbon black, carbon blacks partially or completely covered with silica by a post-treatment, or carbon blacks modified in situ by silica, such as, for example, the fillers marketed by Cabot Corporation under the name EcoblackTM "CRX 2000" or "CRX4000". By "reinforcing inorganic filler" is meant here, in a known manner, any inorganic or inorganic filler whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or still charge "non-black" ("non-black filler") in contrast to carbon black, this inorganic filler being capable of reinforcing alone, with no other means than an intermediate coupling agent, a rubber composition intended for the manufacture of a tire rolling strip, in other words capable of replacing, in its P10-3493 / SC 3029930-reinforcement function, a conventional tire-grade carbon black for tread. Such a filler is generally characterized by the presence of functional groups, in particular hydroxyl (OH), at its surface, thereby requiring the use of an agent or coupling system intended to ensure a stable chemical bond between the elastomer and said charge. As reinforcing inorganic filler, there may be mentioned siliceous fillers, such as silica, or aluminous, silica-alumina, or titanium oxide.

The reinforcing filler for the composition according to the invention comprises a blend of carbon black and silica, in which carbon black is predominant. The degree of carbon black ranges from 20 to 30 parts per hundred parts of elastomer, phr, and the silica content ranges from 1 to 7 phr and the total content of reinforcing filler is less than or equal to 35 phr.

According to an alternative embodiment of the invention, the total amount of reinforcing filler is less than or equal to 33 phr. Preferably, the carbon black content of the composition is less than or equal to 28 phr, more preferably less than or equal to 26 phr.

Advantageously, the silica content ranges from 2 to 5 phr. The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface area both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g, especially between 60 and 300 m2 / g. Highly dispersible precipitated silicas ("HDS") include, for example, "Ultrasil" 7000 and "Ultrasil" 7005 silicas from Degussa, "Zeosil 1165MP", "Zeosil 1135MP" and "Zeosil 1115MP" silicas. and "Zeosil Premium 200 MP" from Rhodia, the "Hi-Sil" silica EZ150G from PPG, the "Zeopol" silicas 8715, 8745 and 8755 from Huber, the high surface area silicas as described in WO 03/016387. It should be noted that the CTAB specific surface area is determined according to the French standard NF T 45-007 of November 1987 (method B).

As reinforcing inorganic filler, mention may also be made of mineral fillers of the aluminous type, in particular alumina (Al 2 O 3) or aluminum (oxide) hydroxides, or reinforcing titanium oxides, for example described in US Pat. 6,610,261 and US 6,747,087.

The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, or beads. Of course, the term "reinforcing inorganic filler" is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible silicas as described above. It will also be possible to add to the composition a coupling agent for coupling the reinforcing inorganic filler, especially silica, to the diene elastomer, such as a polysulfide silane.

Crosslinking System The crosslinking system is preferably a vulcanization system, i.e., a sulfur (or sulfur donor) and a primary vulcanization accelerator system. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the production phase as described later, various known secondary accelerators or vulcanization activators such as zinc oxide. stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine).

The sulfur is used at a preferential level of between 0.5 and 10 phr, more preferably between 1 and 8 phr, in particular between 1 and 6 phr, when the composition of the invention is intended, according to a preferred embodiment of the invention. invention, to constitute an "eraser" (or rubber composition) internal of a tire.

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. Any compound capable of acting as an accelerator for vulcanizing diene elastomers in the presence of sulfur, especially thiazole accelerators and their derivatives, accelerators of the thiuram type, zinc dithiocarbamates, may be used as accelerator. These primary accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazylsulfenamide (abbreviated as "TBBS"), N-tert-butyl-2-benzothiazylsulfenimide (abbreviated as "TB SI") and mixtures thereof . P10-3493 / SC 3029930 - 12 - Other constituents The rubber matrices of the composites according to the invention also comprise all or part of the additives normally used in rubber compositions intended for the manufacture of tires, such as for example agents anti-aging agents, antioxidants, plasticizers or extension oils, whether these are of aromatic or non-aromatic nature, especially very low or non-aromatic oils (eg, naphthenic or paraffinic oils, MES or TDAE oils), agents facilitating the use of the compositions in the green state, anti-eversion agents such as for example sodium hexathiosulphonate or N, N'-m-phenylene biscitraconimide, acceptors and donors of methylene (for example resorcinol , HMT or H3M), metal salts such as organic salts of cobalt or nickel. Those skilled in the art will be able to adjust the formulation of the composition according to their particular needs. Manufacture of rubber compositions The rubber compositions of the invention are manufactured in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first phase of work or thermo-mixing; mechanical (sometimes referred to as "non-productive" phase) at high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second phase of mechanical work (sometimes referred to as a "productive" phase) at a lower temperature, typically less than 120 ° C, for example between 60 ° C and 100 ° C, finishing phase during which the crosslinking or vulcanization system is incorporated . According to one embodiment of the invention, all the basic constituents of the compositions of the invention, with the exception of the vulcanization system, are intimately incorporated, by kneading, during the so-called non-productive first phase. , that is to say that is introduced into the mixer and that is kneaded thermomechanically, in one or more steps, at least these different basic constituents until the maximum temperature between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C. According to a preferred embodiment of the invention, the second elastomer and the inorganic filler are incorporated in the first diene elastomer and carbon black which have previously been prepared in the form of a first masterbatch.

Preferably, this first masterbatch is produced in the "liquid" phase. In order to do this, the diene elastomer in the form of latex, which is in the form of elastomer particles dispersed in water, and an aqueous dispersion of carbon black have been used because, that is, say a charge dispersed in water, commonly called "slurry". More preferably still, the process steps described in document US Pat. No. 6,048,923, which consists in particular in incorporating a continuous flow of a first fluid constituted by the elastomer latex into the mixing zone of a coagulation reactor, will be followed. incorporating a second continuous stream of a second fluid consisting of the aqueous dispersion of carbon black under pressure in the mixing zone to form a mixture with the elastomer latex; the mixing of these two fluids being sufficiently energetic to allow the elastomer latex to be coagulated almost completely with the carbon black before the exit orifice of the coagulation reactor and then to dry the coagulum obtained.

According to another preferred embodiment of the invention, the inorganic filler and the second elastomer are incorporated in the first master batch also in the form of a second master batch which has been previously prepared. This second masterbatch can be prepared in particular in solid form by thermomechanical mixing of the second elastomer and the inorganic filler; it can also be prepared by any other method and in particular it can also be prepared in the liquid phase. It will be noted in particular that the incorporation of the second elastomer alone and the inorganic filler alone or in the form of a second master batch containing the second elastomer and the inorganic filler, can be carried out simultaneously with the introduction into the mixer of the others. constituents (especially the first diene elastomer or first masterbatch) but also advantageously that this or these incorporations can be shifted in time from a few tens of seconds to a few minutes. In the case of introducing the second elastomer alone and the inorganic filler alone, shifted in time from a few tens of seconds to a few minutes, the inorganic filler can be introduced before, after or simultaneously with the second elastomer. By way of example, the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary constituents (in the form of the case) are introduced into a suitable mixer such as a conventional internal mixer. optionally of masterbatches as specified above), any additional coating or processing agents and other miscellaneous additives, with the exception of the vulcanization system. The total mixing time in this non-productive phase is preferably between 1 and 15 minutes. After cooling the mixture thus obtained during the first non-productive phase, the vulcanization system is then incorporated at low temperature, generally in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min. 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, to form, for example, a rubber profile used for the manufacture of semi-finished products. -finished such as tire sidewalls. The vulcanization (or cooking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, the 15 vulcanization system adopted and the kinetics of vulcanization of the composition under consideration. The examples which follow illustrate the invention, without limiting it.

III. EXAMPLES OF CARRYING OUT THE INVENTION Preparation of Natural Rubber and Carbon Black Masterbatch The first masterbatches of diene elastomer and carbon black having a load dispersion rating in the elastomeric matrix greater than or equal to 90, are made in liquid phase according to the method described in US Patent No. 6,048,923.

Thus, according to the protocol detailed in the aforementioned patent, a masterbatch is prepared from N234 or N134 carbon black, marketed by Cabot Corporation, and field natural rubber latex ("latex latex") from Malaysia with a dry rubber content of 28% and a level of ammonia of 0.3%.

This gives a masterbatch A of natural rubber and carbon black in which the carbon black content is 50 phr and which has a dispersion of black in the natural rubber matrix having a Z score of 90. The compositions CA rubber according to the invention are produced from the first master batch A, to which a second BR elastomer and precipitated silica are added in a solid form according to a conventional method of mixing P10-3493 / SC 3029930 - 15 - powder or granules) "Zeosil 1165MP" marketed by Rhodia. Preparation of the rubber compositions The control compositions TM are produced according to a conventional solid-form mixing process in which the elastomer or elastomers, depending on whether the second elastomer is identical to or different from the first elastomer, and the reinforcing filler, the black of which carbon N234 or N134 marketed by Cabot Corporation and, where appropriate, the precipitation silica "Zeosil 1165MP" marketed by Rhodia, are introduced in solid form. The various compositions are carried out as follows: The following tests are carried out as follows: an internal mixer, filled to 70% and having an initial tank temperature of approximately 90.degree. first master batch A for CA compositions (or natural rubber in solid form and carbon black for TM compositions), a second BR elastomer, a second reinforcing filler (silica), then, after one to two minutes of mixing the various other ingredients with the exception of the vulcanization system. According to an alternative embodiment specified in some of the following tests, the second elastomer and the second reinforcing filler, and the coupling agent, if appropriate, are introduced in the form of a master batch previously produced in solid form. Thermomechanical work (non-productive phase) is then carried out in one step (total mixing time equal to about 5 minutes), until a maximum "falling" temperature of about 165 ° C. is reached. The mixture thus obtained is recovered, cooled and the vulcanization system (sulfur and sulfenamide accelerator) is added to an external mixer at 70 ° C, mixing the whole (productive phase) for about 5 to 6 minutes. In the presence of a coating agent, the latter may also be introduced on external mixer instead of the introduction on internal mixer. The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or in the form of profiles that can be used directly, after cutting and or assembly to the desired dimensions, for example as semi-finished products for tires, in particular as tire sidewalls.

This example is intended to show the improvement in the properties of tire sidewall compositions according to the invention compared to sidewall compositions of a conventional control tire. For civil engineering vehicle as well as compositions for tire sidewalls having a dispersion of the load in the elastomeric matrix not according to the invention. The rubber compositions TM, TM1 and TM2 are prepared "en masse" from a blend of natural rubber and BR, and carbon black and, if appropriate, silica, in solid form as detailed in previous paragraph. The compositions according to the invention CA1 and CA2 are respectively prepared from a first masterbatch A in which are added in solid form a second elastomer, in this case a BR, and silica, according to the detailed method. previously. The levels of reinforcing filler and the nature of these fillers are respectively identical to those of compositions TM1 and TM2. The formulations are presented in Table 1 which follows.

Table 1 Composition: TM TM1 CA1 TM2 CA2 NR (1) 50 50 50 50 50 BR (2) 50 50 50 50 50 Carbon black (3) 38 28 - - - Carbon black (4) - - 28 - - Carbon Black (5) - - - 28 - Carbon Black (6) - - - - 28 Silica (7) - 5 5 5 5 Plasticizer (8) 10 5 5 5 5 Wax 1 1 1 1 1 Antioxidant (9) 3 3 3 3 3 ZnO 2,5 2,5 2,5 2,5 2,5 Stearic acid 1 1 1 1 1 Sulfur 1,1 1,1 1,1 1,1 1,1 Accelerator (10) 0, 9 0.9 0.9 0.9 0.9 (1) natural rubber; (2) BR with 0.5% of 1-2; 1 to 1.5% trans; > 98% cis 1-4 (Tg = -108 ° C); (3) carbon black N234 marketed by Cabot Corporation, added to the elastomer blend by standard mixing in solid form, P10-3493 / SC 3029930 - 17 - (4) carbon black N234 sold by Cabot Corporation, from masterbatch A, (5) carbon black N134 sold by Cabot Corporation, added to carbon black, (6) carbon black N134 sold by Cabot Corporation, from masterbatch A, (7) silica "Zeosil 1165MP" marketed by Rhodia, (8) TDAE oil "Vivatec 500" from Klaus Dahleke, (9) N-1,3-dimethylbutyl-N-phenylparapenylenediamine (Santoflex 6-PPD from Flexsys) (10) N-cyclohexyl-2-benzothiazyl sulfenamide (Santocure CBS from Flexsys). The properties measured after cooking at 150 ° C. for 40 minutes are given in Table 2 below.

Table 2 Composition: TM TM1 CA1 TM2 CA2 Note Z 61 63 81 56 80 MA300 / MA100 1.32 1.17 1.21 1.10 1.21 MITR 100 48 113 40 128 Breakage energy 105686 98746 106729 88513 96819 20 notes that the control compositions TM1 and TM2 which comprise a total level of reinforcing filler less than TM (33 phr instead of 38 phr) and a carbon black content of less than TM (28 phr instead of 38 phr) presents much lower strength than TM (value of MA300 / MA100), properties at degraded limits (energy value at break) and a very large fall in fatigue strength (value of MITR). These results are observed whether it is the same carbon black N234 as for the TM composition (for TM1) or a carbon black N134 (for TM2). Surprisingly, it can be seen that the compositions according to the invention CA1 and CA2, which are distinguished from compositions TM1 and TM2 only by the dispersion of the filler in the elastomeric matrix (note Z), have at the same time a close reinforcement. of that of TM (thus significantly improved with respect to TM1 and TM2, respectively), boundary properties close to those of the TM composition and a fatigue resistance much higher than those of the compositions TM1 and TM2 but also very significantly improved compared to to the TM composition. P10-3493 / SC 3029930 - 18 - Test 2 The object of this test is to show that compositions in accordance with the invention having even lower values of reinforcing filler content nevertheless make it possible to obtain identical or even better properties compared to to the standard control composition used in the sidewall of civil engineering tires. The TM composition has the same meaning as in test 1.

Compositions TM3 and TM4 are prepared "in bulk" from a blend of natural rubber and BR, and carbon black and silica, in solid form as detailed in the paragraph on the preparation of the compositions. The CA3 and CA4 compositions in accordance with the invention are respectively prepared from a first masterbatch A in which a second elastomer, in this case a BR, and silica is added in solid form, according to the detailed process. in the preparation paragraph of the compositions. The levels of reinforcing filler and the nature of these fillers are respectively identical to those of compositions TM1 and TM2.

The formulations are shown in Table 3 which follows. Table 3 Composition: TM TM3 CA3 TM4 CA4 NR (1) 50 50 50 50 50 BR (2) 50 50 50 50 50 Carbon Black (3) 38 26 - - - Carbon Black (4) - - 26 - - Black carbon (5) - - - 26 - Carbon black (6) - - - - 26 Silica (7) - 5 5 5 5 Plasticizer (8) 10 5 5 5 5 Wax 1 1 1 1 1 Antioxidant (9) 3 3 3 3 3 ZnO 2,5 2,5 2,5 2,5 2,5 Stearic acid 1 1 1 1 1 Sulfur 1,1 1,1 1,1 1,1 1,1 Accelerator (10) 0.9 The properties measured after baking at 150 ° C. for 40 minutes are given in Table 4 below. Table 4 5 Composition: TM TM3 CA3 TM4 CA4 Note Z 61 68 80 58 77 MA300 / MA100 1.29 1.09 1.09 1.01 1.09 MITR 100 64 132 52 110 Rupture energy 101681 78287 86626 79907 88384 The same is true of the previous test with compositions according to the invention CA3 and CA4 which make it possible to obtain reinforcing properties and boundary properties closer to the TM composition than those obtained by the TM3 and TM4 compositions, and still more resistant to fatigue properties. improved compared to the control composition TM. These results are even more surprising than the previous ones insofar as the total content of reinforcing filler of the CA3 and CA4 compositions is 31 phr with only 26 phr of carbon black.

15 P10-3493 / SC

Claims (17)

CLAIMS1) Tire sidewall, having a rubber composition based on at least one blend of polyisoprene, synthetic rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler comprising carbon black and silica, crosslinking, characterized in that the reinforcing filler comprises predominantly carbon black, the carbon black content is from 20 to 30 parts per hundred parts of elastomer, pce, and the silica content ranges from 1 to 7 phr and that the total level of reinforcing filler is less than or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a Z score greater than or equal to 75. 2) blank according to claim 1, wherein the total rate of reinforcing filler is less than or equal to 33 phr. 3) blank according to claim 1, wherein the carbon black content is less than or equal to 28 phr. 4) A blank according to claim 3, wherein the carbon black content is less than or equal to 26 phr. 5) A blank according to any one of the preceding claims, wherein the silica content is from 2 to 5 phr. 6) A blank according to any one of claims 1 to 5, wherein the level of synthetic rubber or synthetic polyisoprene ranges from 20 to 80 phr and the level of BR ranges from 20 to 80 phr. 7) A blank according to claim 6, wherein the rate of synthetic rubber or synthetic polyisoprene ranges from 50 to 80 phr. 8) A sidewall according to any one of claims 6 or 7, wherein the BR level ranges from 30 to 50 phr. 9) A sidewall according to any one of claims 1 to 5, wherein the BR level ranges from 50 to 80 phr. 10) A blank according to any one of the preceding claims, wherein the composition is obtained from a first masterbatch comprising at least polyisoprene and carbon black, and having a dispersion of carbon black in the elastomeric matrix having a Z-score greater than or equal to 90. P10-3493 / SC 3029930 - 21 - 11) A blank according to claim 10, wherein the first masterbatch is obtained by liquid phase mixing from a polyisoprene latex and an aqueous carbon black dispersion. 5 12) A blank according to claim 11, wherein the first masterbatch is obtained according to the following process steps: feeding a continuous stream of a polyisoprene latex to a mixing zone of a coagulation reactor defining an elongated zone method of coagulation extending between the mixing zone and an outlet, supplying a continuous stream of a fluid comprising carbon black under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture, - drying the coagulum obtained previously to recover the first masterbatch. 15 13) A method for manufacturing a sidewall for a tire having a rubber composition based on at least one blend of polyisoprene, synthetic rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler comprising carbon black and the silica, a crosslinking system, characterized in that the reinforcing filler comprises predominantly carbon black, the carbon black content is from 20 to 30 parts per hundred parts of elastomer, pce, and the silica content is from 1 to 5 phr and that the total content of reinforcing filler is less than or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a Z score of greater than or equal to 80 which comprises the following steps: - preparing a first masterbatch comprising at least polyisoprene and carbon black and having a dispersion of the carbon black in the elastomeric matrix having a Z-score greater than or equal to 90, - incor poring the silica, BR and the other constituents of the composition, with the exception of the crosslinking system, to the first masterbatch in a mixer by thermomechanically kneading the mixture until reaching a maximum temperature of between 130.degree. C. and 200.degree. ° C, - cool the assembly to a temperature below 100 ° C, - then incorporate: the crosslinking system; - mix everything up to a maximum temperature below 120 ° C. 35 14) The method of claim 13, wherein the first masterbatch is obtained by liquid phase mixing from a polyisoprene latex and an aqueous dispersion of carbon black. P10-3493 / SC 3029930 - 22 - 15) The method of claim 14, wherein the first masterbatch is obtained according to the following process steps: - supply a continuous stream of a polyisoprene latex to a mixing zone of a coagulation reactor defining an elongated zone coagulation line 5 extending between the mixing zone and an outlet, - supplying a continuous flow of a fluid comprising carbon black under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture, - drying the coagulum obtained previously to recover the first masterbatch. 16. A tire having a sidewall according to any one of claims 1 to 12. 17) A tire intended to equip civil engineering vehicles comprising a sidewall according to any one of claims 1 to 12. P10-3493 / SC