CA2969049C - Tyre sidewall - Google Patents

Abstract

The invention relates to a tyre sidewall having a rubber composition based on at least one blend of polyisoprene, natural rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler comprising carbon black and silica, a crosslinking system, characterized in that the reinforcing filler predominantly comprises carbon black, that the content of carbon black ranges from 20 to 30 parts per hundred parts of elastomer, phr, and the content of silica ranges from 1 to 7 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 value greater than or equal to 75.

Description

FLANGE FOR TIRE
The present invention relates to a sidewall for a tire based on a composition of rubber, and more particularly for tires used for the Civil Engineering.
The sidewalls of tires used for Civil Engineering represent approximately 15% of the total mass of the tires, therefore a significant mass, which when the strip of bearing is partially worn, has a very significant impact on the resistance to tire rolling.
fi is therefore interesting to try to reduce the hysteresis of the sides of such tires in order to have an impact on the rolling resistance of these tyres.
One of the ways to decrease the hysteresis is to lower the amount of load reinforcing present in the sides. However, it is known that the decrease in the rate of charge reinforcement generally leads to a deterioration of the mechanical properties as fatigue strength and boundary properties and reinforcement.
Indeed, the sidewalls of Earthmover tires are subjected to very strong solicitations both in terms of bending deformation, aggression and thermal These prolonged static or dynamic stresses on the sidewalls in the presence ozone, show more or less marked cracks or cracks, the size of which propagation under the effect of the persistence of the stresses can cause a damage important on the flank concerned. It is therefore important that the compositions constituting the tire sidewalls for Earthmover in particular, have very good mechanical properties, and therefore generally with high filler content reinforcing.
The plaintiffs have discovered, surprisingly and on the contrary, knowledge of the person skilled in the art, that compositions weakly charged with black of carbon but having a very good dispersion of the filler in the matrix elastomeric, made it possible to obtain sidewalls presenting both resistance to improved fatigue while maintaining very good stiffness properties The subject of the invention is therefore a sidewall for a tire, having a composition of rubber based on at least one blend of polyisoprene, natural rubber or synthetic polyisoprene, and polybutadiene BR, a reinforcing filler including carbon black and silica, a crosslinking system, characterized in that than the load reinforcing mainly comprises carbon black, that the black content of carbon ranges from 20 to 30 parts per hundred parts of elastomer, phr, and the rate of silica ranges from 1 to 7 phr and the total rate of reinforcing filler is less than or equal to 35 phr, the dispersion filler in the elastomeric matrix having a higher Z rating or equal to 75.

- 2 -According to a variant embodiment of the invention, the total charge rate reinforcing is less than or equal to 33 pce.
Preferably, the carbon black content of the composition is lower or equal to 28 phr, more preferably less than or equal to 26 phr.
The silica content preferably ranges from 2 to 5 phr.
Advantageously, the rate of natural rubber or synthetic polyisoprene goes from 20 to 80 pce and the rate of BR ranges from 20 to 80 pce.
According to one embodiment of the invention, the rate of natural rubber or of synthetic polyisoprene ranges from 50 to 80 phr.
According to another embodiment of the invention, the BR rate ranges from 50 to 80 pc.
According to one embodiment of the invention, the composition is obtained at from one first masterbatch comprising at least polyisoprene and carbon black carbon, and having a dispersion of the carbon black in the elastomeric matrix having a Z score greater than or equal to 90.
In particular, the first masterbatch is obtained by phase mixing liquid to from a polyisoprene latex and an aqueous dispersion of carbon black carbon.
Preferably, it is obtained according to the following process steps:
- feed a continuous flow of a polyisoprene latex to a zone of mixed a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, - feeding a continuous flow of a fluid comprising carbon black under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture, - dry the coagulum obtained previously in order to recover the first mixture master.
The invention also relates to a method of manufacturing a sidewall for tire having a rubber composition based on at least one blend of polyisoprene, natural rubber or synthetic polyisoprene, and polybutadiene BR, a charge reinforcement comprising carbon black and silica, a system of crosslinking, characterized in that the reinforcing filler mainly comprises black of carbon, that the carbon black content ranges from 20 to 30 parts per hundred parts of elastomer, pce, and the silica rate ranges from 1 to 5 pce and the total charge rate reinforcing is less

3 or equal to 35 phr, the dispersion of the filler in the elastomeric matrix having a Z grade greater than or equal to 80 which includes the following steps:
- preparing a first masterbatch comprising at least the polyisoprene and black of carbon, and having a dispersion of the carbon black in the matrix elastomeric having a Z score greater than or equal to 90, - incorporate the silica, the BR and the other constituents of the composition, with the exception of crosslinking system, to the first masterbatch in a mixer in kneading thermomechanically all until reaching a maximum temperature between 130C and 200C, - cool the assembly to a temperature below 100 C, - then incorporate: the crosslinking system;
- mix everything to a maximum temperature of less than 120°C.
According to another embodiment, a sidewall for a tire is proposed, having a rubber composition based on at least one blend of a first material and of polybutadiene BR, the first material being selected from the group comprising the polyisoprene, natural rubber and synthetic polyisoprene, a filler reinforcing comprising carbon black and silica, a crosslinking system, characterized in that the reinforcing filler mainly comprises carbon black, which the rate of black of carbon ranges from 20 to 30 parts per hundred parts of elastomer, pce, and the rate of silica ranges from 1 to 7 phr and the total rate of reinforcing filler is less than or equal to 35 pce, the dispersion of the filler in the elastomeric matrix having a Z rating greater than or equal to 75.
According to another embodiment, there is provided a manufacturing method on one side for a tire having a rubber composition based on at least one cutting of a first material and polybutadiene BR, the first material being selected among the group .. including polyisoprene, natural rubber and polyisoprene from synthesis, a filler reinforcement comprising carbon black and silica, a system of crosslinking, characterized in that the reinforcing filler mainly comprises black of carbon, that the carbon black content ranges from 20 to 30 parts per hundred parts of elastomer, pce, and the rate of silica ranges from 1 to 5 phr and that the total rate of reinforcing filler is less than or equal to 35 pce, the dispersion of the filler in the elastomeric matrix having a grade Z
greater than or equal to 80 which includes the following steps:
Date Received/Date Received 2021-09-24 3a - preparing a first masterbatch comprising at least the polyisoprene and the carbon black, and having a dispersion of the carbon black in the matrix elastomeric with a Z score greater than or equal to 90, - incorporate the silica, the BR and the other constituents of the composition, to except for the crosslinking system, to the first masterbatch in a mixer by thermomechanically kneading the whole until reaching a maximum temperature between 130 C and 200 C, - cool the assembly to a temperature below 100 C, - then incorporate: the crosslinking system;
- mix everything to a maximum temperature of less than 120°C.
The invention finally relates to a tire comprising a sidewall as described previously, 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 shown below after.
Dispersion In a known manner, the dispersion of filler in an elastomeric matrix may be represented by the grade Z, which is measured, after cross-linking, according to the method described by S.
Otto and Al in Kautschuk Gummi Kunststoffe, 58 Jahrgang, NR 7-8/2005, in agreement with the ISO 11345 standard.
The calculation of the Z score is based on the percentage of area in which the load is not dispersed (% undispersed area), as measured by the device disperseGRADER+
supplied with its operating mode and operating software disperDATA
by the Society Dynisco according to the equation:
Z= 100 - (% undispersed area) /0.35 The percentage of undispersed surface is measured using a camera observing the sample surface under incident light at 30 . Dots lights are associated with filler and agglomerates, while dark dots are associated with the matrix of rubber ; digital processing transforms the image into a black image and white, and allows the determination of the percentage of undispersed surface, such as described by S. Otto in the aforementioned document.
Date Received/Date Received 2021-09-24

- 4 -The higher the Z score, the better the dispersion of the load in the matrix elastomeric (a Z score of 100 corresponding to perfect dispersion and a Z-grade from 0 to poor dispersion). It will be considered that a Z score greater than or equal to 80 corresponds to a surface with very good dispersion of the charge in the elastomeric matrix.
Tensile tests These tests make it possible to determine the elasticity stresses and the properties to rupture; those carried out on the cooked mixtures are carried out in accordance with Standard AFNOR-NF-T46-002 of September 1988.
We measure at a temperature of 100 C 2 C, and under normal conditions humidity (50 5% relative humidity), according to French standard NF T 40-(December 1979), the breaking stresses (in MPa) and the elongations at breaking (in %) are also measured, the energy at break (Break Energy) being the product .. stress at break and elongation at break.
We also measure at a temperature of 23 C -I 2 C, the nominal secant modulus (Where apparent stress, in MPa) at 100% elongation (denoted MA100) and at 300%
elongation (denoted MA300).
Dynamic property The dynamic property tan(O)max is measured on a viscoanalyzer (Mctravib VA4000), according to ASTM D 5992-96. Record the response of a sample of vulcanized composition (cylindrical specimen 4 mm thick and 400 mm2 in section), submitted to one sinusoidal stress in alternating simple shear, at the frequency of 10Hz and at temperature of 60 C, according to the ASTM D 1349 ¨ 99 standard. An amplitude sweep is carried out of deformation from 0.1 to 50% (go cycle), then from 50% to 0.1% (return cycle). the exploited result is the loss factor (tan 8). For the return cycle, the value is indicated maximum observed tan (tan(6)max), between the values at 0.1% and at 50% deformation (Payne effect).
Fatigue test Fatigue resistance, expressed in number of cycles or in relative unit (ur), is measured in a known manner on 12 specimens subjected to repeated traction low frequency up to 75% elongation, at 23 C, using a device Monsanto (type .. MFTR ) until failure of the specimen, according to ASTM D4482-85 standards and ISO
6943.
The result is expressed in relative unit (ur). A higher value than of the witness, arbitrarily set to 100, indicates an improved result, i.e. a better fatigue resistance of rubber samples.

- 5 -II- DETAILED DESCRIPTION OF THE INVENTION
In this description, unless expressly stated otherwise, all percentages (%) indicated are % by mass. On the other hand, any interval of values designated the expression "between a and b" represents the range of values ranging from more than has less than b (i.e. bounds a and b excluded) while any interval of values designated the expression "from a to b" means the range of values from a to b (that is to say including the strict bounds a and b).
diene elastomer By elastomer or "diene" rubber, must be understood in a known manner one (we means one or more) elastomer derived at least in part (ie, a homopolymer or a copolymer) of diene monomers (monomers carrying two double bonds carbon-carbon, conjugated or not).
These diene elastomers can be classified into two categories:
"basically unsaturated" or "essentially saturated".
"basically unsaturated", a diene elastomer derived at least in part from diene monomers conjugated, having a rate of units or units of diene origin (dienes conjugates) which is greater than 15% (% by moles); this is how diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM
do not fall within the previous definition and may be in particular qualified of "essentially saturated" diene elastomers (level of original units dienic low or very low, always less than 15%). In the category of elastomers diene "essentially unsaturated", is meant in particular by elastomer dienic "highly unsaturated" a diene elastomer having a rate of original units dienic (conjugated dienes) which is greater than 50%.
Given these definitions, the term “elastomer” is understood more particularly dienique capable of being used in the compositions in accordance with the invention:
(a) - any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms;
(b) - any copolymer obtained by copolymerization of one or more dienes conjugates with each other or with one or more aromatic vinyl compounds having from 8 to 20 carbon atoms;
(c) - a ternary copolymer obtained by copolymerization of ethylene, of an a-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having 6 to 12 carbon atoms, such as the elastomers obtained from

- 6 -ethylene, propylene with a non-conjugated diene monomer of the aforementioned type Phone that in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene;
(d) - a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated, especially chlorinated or brominated, versions of this type of copolymer.
Although it applies to any type of diene elastomer, the person skilled in the art of tire will understand that the present invention is preferably implemented work with essentially unsaturated diene elastomers, in particular of the type (a) or (b) above above.
The aforementioned elastomers can have any microstructure which is a function from polymerization conditions used, in particular the presence or not of a agent modifying and/or randomizing agent and quantities of modifying agent and/or randomizing employed. The elastomers can be, for example, block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they can be coupled and/or starred or further functionalized with a coupling agent and/or star or functionalization. For coupling to carbon black, mention may be made, for example, of example of functional groups comprising a C-Sn bond or functional groups amino such as aminobenzophenone for example; for coupling to a load inorganic reinforcing agent such as silica, mention may be made, for example, of groups functional silanol or polysiloxane having a silanol end (as described for example in FR
2,740,778 or US 6,013,718, and WO 2008/141702), alkoxysilane groups (such as described by example in FR 2 765 882 or US 5 977 238), carboxylic groups (such that described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US 2006/0089445) or polyether groups (as described by example in EP 1 127 909 or US 6 503 973, WO 2009/000750 and WO 2009/000752).
Mention may also be made, as functional elastomers, of those prepared by the use of a functional initiator, in particular those bearing an amine or tin function (see by example WO 2010072761).
As other examples of functionalized elastomers, mention may also be made of from elastomers (such as SBR, BR, NR or IR) of the epoxy type.
The elastomeric matrix of the composition in accordance with the invention comprises at less :
- natural rubber, NR, or synthetic polyisoprene, preferably with a rate ranging preferably from 20 pce to 80 pce, - BR, preferably with a content ranging from 20 to 80 pce.
It will be understood that by natural rubber or synthetic polyisoprene, that it may be of only one of these elastomers or of a blend of natural rubber and of one or several synthetic polyisoprene.

- 7 -Similarly, when we talk about BR, it can be one or more polybutadienes.
According to one embodiment of the invention, the rate of natural rubber or of synthetic polyisoprene ranges from 50 to 80 phr, and preferably, the BR content ranges from 30 to 50 pc.
According to another embodiment of the invention, the BR rate ranges from 50 to 80 pc.
As BR, BRs with a rate (% molar) of cis-chains in 1.4 greater than 90%.
According to one embodiment of the invention, the composition comprises at least another diene elastomer, preferably chosen from the group consisting of copolymers of butadiene-styrene (SBR), isoprene-butadiene copolymers (BIR), .. isoprene-styrene copolymers (SIR) and isoprene-styrene copolymers butadiene-styrene (SBIR).
More preferably, this other diene elastomer consists of an SBR
with a rate preferably ranging from 10 to 30 pce, whether it is an SBR prepared in emulsion ("ESBR") or an SBR prepared in solution ("SSBR"), or a coupage (mixture) 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 which can be used in combination with all .. 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 matrix elastomeric in accordance with the invention, it is particularly interesting to use a masterbatch of diene elastomer and reinforcing filler produced by phase liquid . To do this, we used an elastomer in the form of latex.
who is present in the form of elastomer particles dispersed in water, and at a dispersion aqueous of the filler, that is to say a filler dispersed in water, fluently called slurry. Certain processes in particular, such as those described in the document US 6,048,923, make it possible to obtain a masterbatch of elastomer and of filler with very good filler dispersion in the matrix elastomeric, much improved compared to the dispersion of the filler in the matrix elastomeric capable of being obtained during the solid phase mixing of elastomer and charge reinforcing. This method consists in particular of incorporating a continuous flow of a first fluid consisting of an elastomeric latex in the mixing zone of a reactor

- 8 -coagulation, incorporating a second continuous stream of a second fluid consisting of an aqueous dispersion of filler under pressure in the mixing zone to form a mixture with the elastomer latex; the mixing of these two fluids being enough energy to almost completely coagulate the latex of elastomer with the filler before the outlet orifice of the reactor of coagulation then to dry the coagulum obtained.
This process is particularly suitable for making a masterbatch presenting a very good dispersion, from a latex of natural rubber and black carbon. In Indeed, the application of this process is made particularly favorable by the ability that possesses natural rubber latex and carbon black to coagulate whole spontaneously. Conversely, silica does not coagulate spontaneously with latex of natural rubber because silica aggregates are typically hydrophilic in nature and have more affinity with water than with elastomer particles themselves.
As mentioned above, liquid phase mixing processes are preferentially used to make it possible to obtain masterbatches at base diene elastomer and carbon black with very good dispersion of black carbon in the elastomer. Thus, in particular for the realization of the first mixed master of diene elastomer and carbon black, we will use more particularly one diene elastomer latex, the elastomer latex being a form particular of the elastomer which is in the form of dispersed elastomer particles in water.
The invention therefore preferably relates to elastomer latexes dienic, the diene elastomers being those defined above.
More particularly, for natural rubber (NR) which is suitable particularly to invention, this natural rubber exists in different forms such as detail the chapter 3 Latex concentrates: properties and composition, by KF
Gaseley, ADT
Gordon and TD Pendle in Natural Rubber Science and Technology, AD
Roberts, Oxford University Press ¨ 1988.
In particular several forms of natural rubber latex are marketed: the natural rubber latex known as field latex rubber natural, so-called concentrated (concentrated natural rubber latex), latex epoxied ( ENR), deproteinized latexes or even prevulcanized latexes. The latex of rubber natural from the field is a latex in which ammonia has been added to avoid a early coagulation and concentrated natural rubber latex corresponds to a latex of field which has undergone a treatment corresponding to a washing followed by a new concentration. The different categories of natural rubber latex concentrates are listed in particular according to standard ASTM D 1076-06. Among these latexes of rubber natural concentrates, a distinction is made in particular between natural rubber latexes concentrates of so-called quality: HA (high ammonia) and of so-called LA quality; we will use WO 2016/09655

9 PCT/EP2015/079066 advantageously for the invention of concentrated natural rubber latexes of quality HA.
NR latex can be pre-modified physically or chemically (centrifugation, enzymatic treatment, chemical modifier, etc.) The latex can be used directly or be diluted beforehand in water for facilitate its implementation.
Thus, compared to synthetic elastomer latex, the latex can in particular consist of a synthetic diene elastomer already available in emulsion form, or in a synthetic diene elastomer initially in solution which is emulsified in a mixture of organic solvent and water, usually using a surfactant asset Reinforcing charge In a known way, the term “reinforcing filler” means a filler known for its capacities to reinforce a rubber composition usable for the manufacture of tires.
These reinforcing fillers include organic fillers, such as black from carbon and inorganic fillers.
Suitable carbon blacks are all carbon blacks, in particular blacks of type HAF, 1SAF, SAF conventionally used in tires (black said of pneumatic grade). Paimi the latter, mention will be made more particularly of the black from 100, 200 or 300 series carbon reinforcing bars (ASTM grades), such as example the black N115, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, higher series blacks (e.g. N400, N660, N683, N772, N990).
Also suitable as carbon black are carbon blacks partially or completely covered with silica by a post-treatment, or the blacks of carbon .. modified in situ by silica such as, without limitation, the loads which marketed by Cabot Corporation under the name EcoblackTM
CRX2000 or CRX4000.
By "reinforcing inorganic filler", must be understood here, in such a way known, all inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even load "non-black"("non-blackfluer") as opposed to carbon black, this filler inorganic being able to reinforce on its own, with no other means than an agent of coupling intermediate, a rubber composition intended for the manufacture of a Band tire bearing, in other words suitable for replacing, in its function of

- 10 -reinforcement, a conventional tire grade carbon black for tape of rolling. Such a charge is usually characterized by the presence of groups functional, in particular hydroxyl (n OH), on its surface, thereby requiring the employment of a coupling agent or system intended to provide a stable chemical bond Between the elastomer and said filler.
Mention may be made, as reinforcing inorganic filler, of fillers of the type siliceous, such as silica, or aluminous, silica-alumina, titanium oxide.
The reinforcing filler for the composition in accordance with the invention comprises a cutting of carbon black and silica, wherein the carbon black is majority. The rate of carbon black ranges from 20 to 30 parts per hundred parts elastomer, phr, and the rate of silica ranges from 1 to 7 phr and the total amount of reinforcing filler is less than or equal to 35 pc.
According to a variant embodiment of the invention, the total charge rate reinforcing is less than or equal to 33 pce.
Preferably, the carbon black content of the composition is lower 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 can be any reinforcing silica known to those skilled in the art.
job, in particular any precipitated or fumed silica having a BET surface as well as a CTAB specific surface area both less than 450 m2/g, preferably 30 to 400 m2/g, in particular between 60 and 300 m2/g. As precipitated silicas highly dispersible (so-called "HDS"), mention will be made, for example, of Ultrasil silicas 7000 and Ultrasil 7005 from Degussa, Zeosi11165MP silicas, Zeosil 1135MP, Zeosil 1115MP and Zeosil Premium 200 MP from Rhodia, the .. Hi-Sil EZ150G silica from PPG, Zeopol 8715 silicas, 8745 and 8755 from the Huber Company, silicas with a high specific surface as described in the application WO 03/016387.
Note that the CTAB specific surface is determined according to the standard French NF T
45-007 of November 1987 (method B).
By way of reinforcing inorganic filler, mention will also be made of the fillers minerals of aluminous type, in particular alumina (A1203) or (oxide)hydroxides aluminum, or even reinforcing titanium oxides, for example described in US 6,610,261 and US 6,747,087.

- 11 -The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, or even marbles. Good of course, the term “reinforcing inorganic filler” also means mixtures of various reinforcing inorganic fillers, in particular silicas highly dispersible as described above.
It is also possible to envisage adding to the composition an agent of coupling for coupling the reinforcing inorganic filler, in particular silica, to the elastomer dienic, such as a polysulfide silane.
Cross-linking system The crosslinking system is preferably a vulcanization system, that is say a system based on sulfur (or a sulfur-donating agent) and a accelerator vulcanization primer. To this basic vulcanization system come to add, incorporated during the first non-productive phase and/or during the phase productive as described later, various accelerators secondary or known vulcanization activators such as zinc oxide, stearic acid or compounds equivalents, guanidine derivatives (in particular diphenylguanidine).
Sulfur is used at a preferential rate of between 0.5 and 10 pce, plus preferably between 1 and 8 phr, in particular between 1 and 6 phr when the composition of the invention is intended, according to a preferential mode of the invention, to constitute an internal "gum" (or rubber composition) of a pneumatic.
The primary vulcanization accelerator is used at a preferential rate between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.
Any compound capable of acting as an accelerator can be used as an accelerator.
accelerator vulcanization of diene elastomers in the presence of sulfur, in particular from accelerators of the thiazolcs type as well as their derivatives, accelerators of guys zinc th iuram es, dithio carb am ate s. These primary accelerators are more preferentially chosen from the group consisting of 2-disulphide mercaptobenzothiazyl (abbreviated "MBTS"), N-cyclohexyl1-2-benzothiazyl sulfenamide (abbreviated "CBS"), N,N-dicyclohexyl1-2-benzothiazyl sulfenamide (abbreviated "DCBS"), N-ter-buty1-2-benzothiazyl sulfenamide (abbreviated "TBBS"), N-ter-buty1-2-benzothiazyl sulfenimide (abbreviated "TBSI") and mixtures of these compounds.

- 12 -Other constituents The rubber matrices of the composites in accordance with the invention comprise also all or part of the additives usually used in composition of rubber intended for the manufacture of tires, such as for example agents anti-aging, antioxidants, plasticizers or oils extension than these the latter are aromatic or non-aromatic in nature, in particular oils very weakly or non-aromatic (eg, naphthenic or paraffinic oils, MES oils or TDAE), agents facilitating the implementation of the compositions in the state cruo of antireversion agents such as for example sodium hexathiosulfonate or N,N'-m-phenylene-biscitraconimide, methylene acceptors and donors (for example resorcinol, HMT or H3M), metallic salts such as salts organic cobalt or nickel.
A person skilled in the art will know how to adjust the formulation of the composition according to of its special needs.
Manufacture of rubber compounds The rubber compositions of the invention are made in mixers appropriate, using two successive preparation phases according to a procedure general well known to those skilled in the art: a first phase of work or mixing thermo-mechanical (sometimes referred to as the "non-productive" phase) at high temperature, up to a maximum temperature between 130 C and 200 C, preferably Between 145 C and 185 C, followed by a second phase of mechanical work (sometimes qualified as "productive" phase) at lower temperature, typically below 120 C, by example between 60 C and 100 C, finishing phase during which incorporated the cross-linking or vulcanization system.
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 incorporated way intimately, by kneading, during the first so-called non-productive phase, i.e.
to say that introduced into the mixer and kneaded thermomechanically, one or several steps, at least these different basic constituents up to reach the maximum temperature between 130 C and 200 C, preferably between Between 145 C and 185 C.
According to a preferred embodiment of the invention the second elastomer and the inorganic filler are incorporated into the first diene elastomer and the black of carbon which have been previously prepared in the form of a first masterbatch.

- 13 -Preferably, this first masterbatch is produced in the liquid phase.
For this to do, we used the diene elastomer in the form of latex which present under form of elastomer particles dispersed in water, and to a dispersion aqueous of carbon black because, i.e. a filler dispersed in water, commonly called slurries. More preferably still, the process steps will be followed described in the document US 6,048,923, which consists in particular in incorporating a continuous flow of one first fluid consisting of the elastomer latex in the mixing zone of one coagulation reactor, to incorporate a second continuous flow of a second fluid consisting of the aqueous dispersion of carbon black under pressure in the zone of mixing to form a mixture with the elastomer latex; mixing death two fluids being sufficiently energetic to allow coagulation nearly completely the elastomer latex with the carbon black before the orifice of exit from coagulation reactor and then drying the coagulum obtained.
According to another preferred embodiment of the invention, the filler inorganic and the second elastomer are incorporated into the first masterbatch by presenting themselves also in the form of a second masterbatch which will have been previously prepare.
This second masterbatch can be prepared in particular in solid form by thermomechanical mixing of the second elastomer and the inorganic filler;
he can also be prepared by any other process and in particular it can be also prepared in the liquid phase.
It will be noted in particular that the incorporation of the second elastomer alone and the charge inorganic alone or in the form of a second masterbatch containing the second elastomer and inorganic filler, can be carried out simultaneously to the intro in the mixer of the other constituents (in particular the first elastomer dienic or first masterbatch) but also advantageously that this or these incorporations can be shifted in time by a few tens of seconds to a few minutes. In the case of the introduction of the second elastomer alone and of the inorganic filler alone, delayed in time by a few tens of seconds to a few minutes, the inorganic filler can be introduced before, after or simultaneously with the second elastomer.
For example, the first (non-productive) phase is conducted in one single step thermomechanical process during which, in a suitable mixer, Phone than a usual internal mixer, all the necessary constituents (in the form the case masterbatches as specified above), any officers additional covering or implementation and other additives various, to except for the vulcanization system. The total mixing time, in this phase non-productive, is preferably between 1 and 15 min.

- 14 -After cooling the mixture thus obtained during the first phase Nope-productive, we then incorporate the vulcanization system at low temperature, usually in an external mixer such as a roller mixer; the all 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 under the shape of a sheet or a plate, in particular for characterization in laboratory, or further extruded, for example to form a rubber profile used for the manufacture of semi-finished products such as tire sidewalls.
The vulcanization (or curing) is carried out in a known manner at a temperature generally between 130 C and 200 C, for a sufficient time which can vary for example between 5 and 90 min depending in particular on the temperature of baking, vulcanization system adopted and the vulcanization kinetics of the composition considered.
The following examples illustrate the invention, without however limiting it.
III. EXAMPLES OF REALIZATION OF THE INVENTION
Preparation of masterbatch of natural rubber and carbon black The first masterbatches of diene elastomer and carbon black presenting a load dispersion note in the upper elastomeric matrix or equal to 90, are produced in the liquid phase according to the process described in the US patent Patent No 6,048,923.
Thus, according to the protocol detailed in the aforementioned patent, a masterbatch to from carbon black N234 or N134, marketed by Cabot Corporation, and fields natural rubber latex (field latex) in origin from Malaysia with a dry rubber extract of 28% and a rate of ammonia 0.3%.
A masterbatch A of natural rubber and carbon black is thus obtained.
carbon in which the content of carbon black is 50 phr and which has a dispersion black in the natural rubber matrix having a Z rating of 90.
The CA rubber compositions in accordance with the invention are made from go from first masterbatch A to which is added according to a conventional process of mixing

- 15 -in solid form a second BR elastomer and precipitated silica (powder or granules) Zeosil 1165MF' marketed by the company Rhodia.
Preparation of rubber compositions The control compositions TM are produced according to a conventional method of mixing in solid form 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, of which the black of carbon N234 or N134 marketed by Cabot corporation and, on case where applicable, the precipitation silica Zeosil 1165MP marketed by the society Rhodia, are introduced in solid form.
The different compositions are made as follows:
We proceed for the tests which follow in the following way: we introduce in a internal mixer, filled to 70% and whose initial tank temperature is of about 90 C, the first masterbatch A for CA compositions (or rubber natural in solid form and carbon black for TM compositions), a second BR elastomer, a second reinforcing filler (silica), then, after one to of them minutes of mixing, the various other ingredients with the exception of the mixing system vulcanization. According to a variant embodiment specified in some of the essays which follow, the second elastomer and the second reinforcing filler, and the agent of coupling, if any, are introduced in the form of a masterbatch executed previously in solid form.
Thermomechanical work is then carried out (non-productive phase) in one stage (duration total mixing time equal to about 5 min), until reaching a temperature maximum of "drop" of about 165 C.
The mixture thus obtained is recovered, cooled and then the system is added.
of vulcanization (sulphur and sulfenamide accelerator) on an external mixer at 70 C, in mixing everything (productive phase) for about 5 to 6 min. When presence of covering agent, the latter can also be introduced into a mixer external to place of 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, either in the form of usable profiles directly, after cutting and/or assembly to the desired dimensions, by example as semi-finished products for tyres, in particular as sidewalls tires.

- 16 -Trial 1 This example aims to show the improvement of the properties of compositions for sidewalls of tires in accordance with the invention with respect to compositions for sidewalls of a conventional control tire for an Earthmover vehicle as well as only tire sidewall compositions having filler dispersion in the elastomeric matrix not in accordance with the invention.
The rubber compositions TM, TM1 and TM2 are prepared in bulk from go of a blend of natural rubber and BR, and carbon black and, if appropriate, of silica, in solid form as detailed in the previous paragraph.
The compositions in accordance with the invention CA1 and CA2 are respectively prepared to from a first masterbatch A in which are added in the form solid one second elastomer, in this case a BR, and silica, according to the process detailed previously. The rates of reinforcing filler and the nature of these fillers are identical respectively to those of the compositions TM1 and TM2.
The formulations are shown in Table 1 below.
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 the Cabot company Corporation, added to elastomeric cutting by standard mixing in solid form,

- 17 -(4) carbon black N234 marketed by Cabot Corporation, coming from masterbatch A, (5) carbon black N134 marketed by Cabot Corporation, added to carbon black cutting, (6) carbon black N134 marketed by Cabot Corporation, coming from masterbatch A, (7) Zeosil 1165MP silica sold by Rhodia, (8) TDAE Vivatec 500 oil from the company Klaus Dahleke, (9) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine (Santoflex 6-PPD from society flcxsys);
(10) N-cyclohexyl-2-benzothiazyl-sulfenamide (Santocure CBS from the company Flexsys).
The properties measured after curing at 150 C for 40 minutes are given in the Table 2 below.
Table 2 Composition: TM TM1 CA1 TM2 Z-score 61 63 81 56 80 MA300/MA100 1.32 1.17 1.21 1.10 1.21 Rupture energy 105686 98746 It is noted that the control compositions TM1 and TM2 which comprise a rate sum of reinforcing filler less than TM (33 pce instead of 38 pce) and a rate of black from carbon less than TM (28 pce instead of 38 pce) present as expected a reinforcement very clearly lower than that of TM (value of MA300/MA100), of properties at degraded limits (value of Energy at break) as well as that a fall very importance of fatigue resistance (MFTR value). We observe these results he it is the same carbon black N234 as for the TM composition (for TM1) or a carbon black N134 (for TM2).
Surprisingly, it is found that the compositions in accordance with the invention CA1 and CA2 which are distinguished from the compositions TM1 and TM2 only respectively by the dispersion of the filler in the elastomeric matrix (note Z), present at both a reinforcement close to that of TM (therefore significantly improved compared to respectively TM1 and TM2), boundary properties close to those of the TM composition and a much higher resistance to fatigue than those of compositions TM1 and TM2 but also very significantly improved compared to the TM composition.

- 18 -Trial 2 The purpose of this test is to show that compositions in accordance with the invention exhibiting even lower values of reinforcing filler content allow nevertheless to obtain identical or even improved properties compared to the conventional control composition used in the sidewall of an Earthmover tire.
The TM composition has the same meaning as in test 1.
The TM3 and TM4 compositions are prepared in bulk from a blend of natural rubber and BR, and carbon black and silica, in the form solid as detailed in the paragraph on the preparation of the compositions.
The compositions CA3 and CA4 in accordance with the invention are respectively prepared to from a first masterbatch A in which are added in the form solid one second elastomer, in this case a BR, and silica, according to the process detailed in the preparation paragraph of the compositions. Charge rates reinforcing and nature of these fillers are identical respectively to those of the compositions TM1 and TM2.
The formulations are shown in Table 3 below.
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 - -Carbon black (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 0.9 0.9 0.9 0.9

- 19 -The properties measured after curing at 150 C for 40 minutes are given in the Table 4 below.
Table 4 Composition: TM TM3 CA3 TM4 Z-note 61 68 80 58 77 MA300/MA100 1.29 1.09 1.09 1.01 1.09 Rupture energy 101681 78287 The same observation is made as for the previous test with compositions according to the invention CA3 and CA4 which make it possible to obtain properties of reinforcement and boundary properties closer to the TM composition than those obtained by the compositions TM3 and TM4, and properties of resistance to fatigue further improved compared to the control composition TM.
These results are even more surprising than the previous ones insofar as where the rate total reinforcing filler of compositions CA3 and CA4 is 31 phr with uniquely 26 phr of carbon black.

Claims (17)

20 1) Sidewall for a tire, having a rubber composition based on au less a blend of a first material and polybutadiene BR, the first material being selected from the group comprising polyisoprene, natural rubber and synthetic polyisoprene, a reinforcing filler comprising carbon black carbon and silica, a crosslinking system, characterized in that the filler reinforcing mainly comprises carbon black, that the carbon black content ranges of 20 to 30 parts per hundred parts of elastomer, pce, and the silica content ranges from 1 to 7 phr and the total rate of reinforcing filler is less than or equal to 35 phr, the load dispersion in the elastomeric matrix having a Z grade superior or equal to 75. 2) Flank according to claim 1, in which the total rate of charge reinforcing is less than or equal to 33 pce. 3) Flank according to claim 1, in which the carbon black content is lower or equal to 28 pce. 4) Flank according to claim 3, in which the carbon black content is lower or equal to 26 pce. 5) Flank according to any one of claims 1 to 4, wherein the rate silica ranges from 2 to 5 phr. 6) Flank according to any one of claims 1 to 5, wherein the rate natural rubber or synthetic polyisoprene ranges from 20 to 80 pce and the rate of BR ranges from 20 to 80 pce. 7) Flank according to claim 6, wherein the rubber content natural or synthetic polyisoprene ranges from 50 to 80 phr. 8) Flank according to any one of claims 6 or 7, wherein the BR rate ranges from 30 to 50 pce. 9) Flank according to any one of claims 1 to 5, wherein the BR rate ranges from 50 to 80 pce. 10) Flank according to any one of claims 1 to 9, wherein the composition is obtained from a first masterbatch comprising at least the polyisoprene and carbon black, and having a dispersion of carbon black carbon in the elastomeric matrix having a Z score greater than or equal to 90. 11) Flank according to claim 10, in which the first masterbatch is obtained by mixing in the liquid phase from a polyisoprene latex and a aqueous dispersion of carbon black. 12) Flank according to claim 11, in which the first masterbatch is obtained according to the following process steps:
- feed a continuous flow of a polyisoprene latex to a zone of mixed a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, - feeding a continuous flow of a fluid comprising carbon black under pressure in the mixing zone of the coagulation reactor to form a coagulated mixture, - dry the coagulum obtained previously in order to recover the first mixed master. 13) Process for manufacturing a sidewall for a tire having a composition of rubber based on at least one blend of a first material and polybutadiene BR, the first material being selected from the group comprising the polyisoprene, natural rubber and synthetic polyisoprene, a filler reinforcement comprising carbon black and silica, a system of crosslinking, characterized in that the reinforcing filler comprises mostly carbon black, that the rate of carbon black ranges from 20 to 30 parts for hundred parts of elastomer, phr, and the silica rate ranges from 1 to 5 phr and that the rate sum 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 :

- preparing a first masterbatch comprising at least the polyisoprene and the carbon black, and having a dispersion of the carbon black in the matrix elastomeric with a Z grade greater than or equal to 90, - incorporate the silica, the BR and the other constituents of the composition, to except for the crosslinking system, to the first masterbatch in a mixer by thermomechanically kneading the whole until reaching a maximum temperature between 130 C and 200 C, - cool the assembly to a temperature below 100 C, - then incorporate: the crosslinking system;
- mix everything to a maximum temperature of less than 120°C. 14) Process according to claim 13, in which the first mixture master is obtained by mixing in the liquid phase from a polyisoprene latex and a aqueous dispersion of carbon black. 15) Process according to claim 14, in which the first mixture master is obtained according to the following process steps:
- feed a continuous flow of a polyisoprene latex to a zone of mixed a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, - feeding a continuous flow of a fluid comprising carbon black under pressure in the mixing zone of the coagulation reactor to form a coagulated mixture, - dry the coagulum obtained previously in order to recover the first mixed master. 16) Tire comprising a sidewall according to any one of claims 1 to 12. 17) Tire intended to equip Civil Engineering vehicles comprising a flank according to any one of claims 1 to 12.