Elastomeric composition exhibiting good dispersion of the filler in the elastomeric matrix

0001The invention relates to a rubber composition based on at least one inorganic filler, in particular silica, and a masterbatch based on a diene elastomer and carbon black, said masterbatch having a very good dispersion of carbon black in the elastomeric matrix and the composition exhibiting good dispersion of all of its charge from the composition in its elastomeric matrix. The term "masterbatch" (commonly known by its English name "masterbatch"): a composite based on elastomer into which a filler and possibly other additives have been introduced.

0002The present invention relates in particular to the use of such a masterbatch for the manufacture of diene rubber compositions reinforced with a blend of organic filler and inorganic filler, intended for the manufacture of tires or semi-finished products finishes for tires, in particular treads for these tires.

0003In order to obtain the optimum reinforcement and hysteresis properties imparted by a load in a tire tread and thus a high wear resistance and a low rolling resistance, it is generally known that this charge is present in the elastomeric matrix in a final form which is both as finely divided as possible and distributed as homogeneously as possible. However, such conditions can only be achieved insofar as this filler has a very good ability, on the one hand to be incorporated into the matrix during mixing with the elastomer and to disaggregate, on the other hand to disperse homogeneously in this matrix.

0004Since fuel economy and the need to protect the environment have become a priority, it has been necessary to produce tires with reduced rolling resistance without penalizing their wear resistance. This has been made possible in particular thanks to the use, in the treads of these tires, of new rubber compositions reinforced at least partially with inorganic fillers, in particular specific silicas of the highly dispersible type, capable of competing from the point of reinforcing view with conventional carbon black of pneumatic grade, while offering these compositions a lower hysteresis, synonymous with lower rolling resistance for the tires comprising them, as well as improved grip on wet, snowy or icy conditions.

0005However, for reasons of mutual affinities, these particles of inorganic charge have an unfortunate tendency, in the elastomeric matrix, to agglomerate between them. These interactions have the harmful consequence of limiting the dispersion of the filler and therefore the reinforcing properties to a level substantially lower than that which it would be theoretically possible to achieve if all the bonds (inorganic filler / elastomer) capable of being created. during the mixing operation, were actually obtained; on the other hand, these interactions tend to increase the consistency in the raw state of the rubber compositions and therefore to make their implementation ("processability") more difficult than in the presence of carbon black, and this even for so-called silicas. highly dispersible.

0006There are different methods for obtaining a master mixture of diene elastomer and reinforcing filler. In particular, one type of solution consists, in order to improve the dispersibility of the filler in the elastomeric matrix, in mixing the elastomer and the filler in the "liquid" phase. To do this, use was made of an elastomer in the form of a latex which is in the form of particles of elastomer dispersed in water, and of 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 the document<patcit id="pcit0001" dnum="US6048923A"><text>US 6,048,923</text></patcit>, make it possible to obtain a master mixture of elastomer and of filler having a very good dispersion of the filler in the elastomeric matrix, very improved compared to the dispersion of the filler in the elastomeric matrix capable of being obtained during the mixing in solid phase of elastomer and reinforcing filler. This process consists in particular in incorporating a continuous flow of a first fluid consisting of an elastomer latex into the mixing zone of a coagulation reactor, in incorporating a second continuous flow of a second fluid consisting of an aqueous dispersion of loading 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 filler before the outlet orifice of the coagulation reactor and then to dry the coagulum obtained.

0007<patcit id="pcit0002" dnum="EP1873191A"><text>EP1873191</text></patcit> discloses a rubber composition obtained from a first masterbatch comprising carbon black and butadiene. This process is particularly suitable for producing a masterbatch with very good dispersion, from a natural rubber latex and carbon black. In fact, the application of this process is made particularly favorable by the ability of natural rubber latex and carbon black to coagulate together spontaneously. Conversely, silica does not spontaneously coagulate with natural rubber latex because silica aggregates are typically hydrophilic in nature and have more affinity for water than with the elastomer particles themselves. Furthermore, such a method has a limit as to the level of carbon black present in the masterbatch, but the subsequent incorporation of carbon black in solid form to allow an increase in the overall charge rate in the elastomeric matrix, does not allow not keep the benefits obtained for hysteresis. In addition, this process is also limited in practice, as to the type of diene elastomer capable of being used to have joint coagulation of the carbon black and the elastomer with natural rubber; the advantage of using other elastomers for numerous pneumatic applications has long been recognized.

0008The Applicant has surprisingly discovered that, unlike the effect of adding carbon black in solid form and a second elastomer, identical or different from the first, and contrary to the knowledge of a person skilled in the art on the difficulties dispersing and using silica in an elastomeric matrix, incorporating silica and a second elastomer, including if this second elastomer is different from the first, in a master mixture of diene elastomer and carbon black having a very good dispersion of carbon black in the matrix of diene elastomer, in particular master mixes prepared according to the above-mentioned process, made it possible to obtain new master mixtures having a hysteresis improved while retaining good dispersion of the entire load in the elastomeric matrix then made up of the two elastomers.

0009A subject of the invention is therefore a rubber composition based on at least one diene elastomer, a reinforcing filler comprising at least carbon black and an inorganic filler with an inorganic filler content less than or equal to 50 parts by weight for one hundred parts of elastomer, characterized in that the composition is obtained from a first masterbatch comprising at least a first diene elastomer and carbon black, and having a dispersion of carbon black in the elastomeric matrix having a Z score greater than or equal to 90, to which is added the inorganic filler and at least one second elastomer, identical or different from the first elastomer.

0010Preferably, this first masterbatch is obtained by mixing in the liquid phase from a latex of the first diene elastomer and an aqueous dispersion of carbon black, and even more preferably it is obtained according to the following process steps:<ul id="ul0001" list-style="dash" compact="compact"><li>supplying a continuous flow of a latex from a first diene elastomer to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet,</li><li>supplying a continuous flow of a fluid comprising a charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture,</li><li>dry the coagulum obtained previously in order to recover the first masterbatch.</li></ul>

0011According to an advantageous embodiment, the weight fraction of the first diene elastomer in the elastomeric matrix is ​​greater than or equal to 50%, and preferably greater than or equal to 60%.

0012According to a preferred embodiment, the first diene elastomer is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers, and more preferably the first diene elastomer is natural rubber.

0013According to another preferred embodiment, the second elastomer is a diene elastomer. Preferably, the second elastomer is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers and even more preferably it is chosen from natural rubber , a polybutadiene and a copolymer of butadiene and styrene.

0014According to another preferred embodiment, the second elastomer is chosen from non-diene elastomers.

0015According to yet another preferred embodiment, the inorganic filler of the composition is a silica or a carbon black coated with silica.

0016The invention also relates to a process for obtaining a composition based on at least one diene elastomer, a reinforcing filler comprising at least carbon black and an inorganic filler with an inorganic filler content less than or equal to 50 parts in weight per hundred parts of elastomer which comprises the following stages:<ul id="ul0002" list-style="dash" compact="compact"><li>preparing a first masterbatch comprising the diene elastomer and carbon black, this first masterbatch having a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 90,</li><li>incorporate the inorganic filler, the second elastomer and the other constituents of the composition, with the exception of the crosslinking system, into the first masterbatch in a mixer by thermomechanically kneading everything until a maximum temperature of between 130 ° C. and 200 ° C,</li><li>cool the assembly to a temperature below 100 ° C.,</li><li>then incorporate: the crosslinking system;</li><li>mix everything up to a maximum temperature below 120 ° C.</li></ul>

0017According to a preferred variant embodiment of the method, the inorganic filler and the second elastomer are introduced simultaneously and preferably in the form of a second masterbatch previously prepared.

0018According to another preferred embodiment, the inorganic filler and the second elastomer are introduced separately; the inorganic filler being introduced before or after the second elastomer.

0019According to another preferred embodiment, the introduction of the inorganic filler and / or of the second elastomer is offset in time from a few tens of seconds to a few minutes relative to the introduction of the first masterbatch into the mixer. Advantageously, the masterbatch is produced in the liquid phase from at least one elastomer latex and a dispersion of carbon black.

0020The invention also relates to a masterbatch of diene elastomer and reinforcing filler which comprises at least one diene elastomer and a reinforcing filler comprising at least carbon black and an inorganic filler with an inorganic filler content less than or equal to 50 parts. by weight per hundred parts of elastomer, obtained by addition to a first masterbatch comprising at least the diene elastomer and the carbon black, and having a dispersion of carbon black in the elastomeric matrix having a Z score greater than or equal to 90, of the inorganic filler and of at least one second elastomer, identical or different from the first elastomer.

0021Preferably, the first masterbatch is obtained by mixing in the liquid phase from a diene elastomer latex and an aqueous dispersion of carbon black, and even more preferably it is obtained according to the following process steps:<ul id="ul0003" list-style="dash" compact="compact"><li>supplying a continuous flow of a diene elastomer latex to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet,</li><li>supplying a continuous flow of a fluid comprising a charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture,</li><li>dry the coagulum obtained previously in order to recover the first masterbatch.</li></ul>

0022According to an advantageous embodiment, in the masterbatch the weight fraction of the first diene elastomer in the elastomeric matrix is ​​greater than or equal to 50%, and preferably greater than or equal to 60%.

0023According to a preferred embodiment, the first diene elastomer of the masterbatch is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers, and more preferably the first diene elastomer is a natural rubber.

0024According to another preferred embodiment, the second elastomer of the masterbatch is a diene elastomer. Preferably, the second elastomer is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers and even more preferably it is chosen from natural rubber , a polybutadiene and a copolymer of butadiene and styrene.

0025According to another preferred embodiment, the second elastomer of the masterbatch is chosen from non-diene elastomers.

0026According to yet another preferred embodiment, the inorganic filler of the masterbatch is a silica or a carbon black covered with silica.

0027The invention also relates to a process for the preparation of a masterbatch which comprises at least one diene elastomer, a reinforcing filler comprising at least carbon black and an inorganic filler with an inorganic filler content less than or equal to 50 parts by weight for one hundred parts of elastomer, obtained by addition to a first masterbatch of diene elastomer and carbon black produced according to the following steps:<ul id="ul0004" list-style="dash" compact="compact"><li>supplying a continuous flow of a diene elastomer latex to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet,</li><li>supplying a continuous flow of a fluid comprising a charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture,</li><li>dry the coagulum obtained previously in order to recover the first masterbatch,</li></ul>inorganic filler and at least one second elastomer, identical to or different from the first elastomer, by thermomechanically kneading.

0028According to a preferred variant embodiment of the method, the inorganic filler and the second elastomer are introduced simultaneously and preferably in the form of a second masterbatch previously prepared.

0029According to another preferred embodiment, the inorganic filler and the second elastomer are introduced separately; the inorganic filler being introduced before or after the second elastomer.

0030According to another preferred embodiment, the introduction of the inorganic filler and / or of the second elastomer is offset in time from a few tens of seconds to a few minutes relative to the introduction of the first masterbatch into the mixer.

0031The invention finally relates to a finished or semi-finished article, a tire tread, a tire and a semi-finished product comprising a composition as described above or a masterbatch as described above.

<u>I. - MEASUREMENTS AND TESTS</u>

0032The rubber compositions are characterized, before and after curing, as indicated below.

Mooney plasticity

0033An oscillating consistometer is used as described in the French standard NF T 43-005 (1991). The Mooney plasticity measurement is carried out according to the following principle: the composition in the raw state (ie, before baking) is molded in a cylindrical enclosure heated to 100 ° C. After one minute of preheating, the rotor (small) rotates within the test tube at 2 revolutions / minute and the torque useful for maintaining this movement is measured after 4 minutes of rotation. The Mooney plasticity (MS 1 + 4) is expressed in "Mooney unit" (MU, with 1 MU = 0.83 Newton.meter).

Dispersion

0034In 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 standard 11345. The calculation of note Z is based on the percentage of surface in which the load is not dispersed ("% surface not dispersed"), as measured by the "disperGRADER +" device supplied with its operating mode and its software. exploitation "DisperDATA" by the company Dynisco according to the equation: <maths id="math0001" num=""><math display="block"><mrow><mi mathvariant="normal">Z</mi><mo>=</mo><mo>−</mo><mfenced separators=""><mo>%</mo><mrow><mspace width="1em" /><mi mathvariant="normal">undispersed surface</mi></mrow></mfenced><mo>/</mo><mn mathvariant="normal">0.35</mn></mrow></math><img file="EP2652015B1_D0001.tif" /></maths>

0035The percentage of non-dispersed surface is measured by means of a camera observing the surface of the sample under incident light at 30 °. Clear dots are associated with filler and agglomerates, while dark dots 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 non-dispersed surface, as described by S. Otto in the aforementioned document. The higher the note Z, the better the dispersion of the charge in the elastomeric matrix (a Z note of 100 corresponding to a perfect dispersion and a Z note of 0 to a poor dispersion). We will consider that a note Z greater than or equal to 80 corresponds to a surface having a very good dispersion of the charge in the elastomeric matrix.

Tensile tests

0036These tensile tests make it possible to determine the elasticity stresses and the breaking properties. Unless otherwise indicated, they are carried out in accordance with French standard NF T 46-002 of September 1988. The module is measured at second extension (ie, after an accommodation cycle at the rate of extension provided for the measurement itself). nominal secant (or apparent stress, in MPa) at 100% elongation (noted MA100). The traction measurements to determine the secant accommodated modules are carried out at a temperature of 23 ° C +/- 2 ° C, and under normal hygrometry conditions (50 +/- 5% relative humidity).

0037The stresses at break (in MPa) and the elongations at break (in%) are also measured. All these tensile measurements are carried out at a temperature of 60 ° C ± 2 ° C, and under normal humidity conditions (50 ± 5% relative humidity), according to French standard NF T 40-101 (December 1979 ).

Dynamic properties

0038Dynamic properties and in particular tan (δ)_max, representative of hysteresis, are measured on a viscoanalyzer (Metravib VA4000), according to standard ASTM D 5992-96. The response of a sample of vulcanized composition is recorded (cylindrical specimen 4 mm thick and 400 mm² of section), subjected to a sinusoidal stress in alternating single shear, at the frequency of 10Hz, under normal temperature conditions (23 ° C) according to standard ASTM D 1349-99, or according to the cases at a different temperature, in particularly in the examples cited, the measurement temperature is 60 ° C. A deformation amplitude sweep is carried out from 0.1% to 50% peak-peak (outward cycle), then from 50% to 0.1% peak-peak (return cycle). The exploited results are the complex dynamic shear modulus (G *) and the loss factor tan (δ). For the return cycle, we indicate the maximum value of tan (δ) observed, noted tan (δ)_max,

<u>II. DETAILED DESCRIPTION OF THE INVENTION</u>

0039The invention relates to a composition based on at least one diene elastomer, a reinforcing filler comprising at least carbon black and an inorganic filler with an inorganic filler content less than or equal to 50 parts by weight per hundred parts of elastomer. , this composition being obtained from a first masterbatch comprising at least a first diene elastomer and carbon black, and having a dispersion of carbon black in the elastomeric matrix having a Z score greater than or equal to 90, to which is added the inorganic filler and at least one second elastomer, identical or different from the first elastomer. It will be noted that in the concept of pce: "parts by weight per hundred parts of elastomer", all of the elastomers present in the final composition are taken into account.

0040In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by mass. On the other hand, any range of values ​​designated by the expression "between a and b" represents the range of values ​​going from more than a to less than b (ie limits a and b excluded) while any range of values ​​designated by the expression "from a to b" signifies the range of values ​​going from a to b (that is to say including the strict limits a and b).

II-1) Elastomer

0041Usually, the terms “elastomer” and “rubber” are used interchangeably in the text.

0042The composition according to the invention comprises at least a first diene elastomer and a second elastomer identical or different from the first, which may or may not therefore be a diene elastomer.

0043The term “diene” elastomer or rubber should be understood in a known manner to mean an elastomer derived at least in part (ie, a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

0044These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". In general, the term "essentially unsaturated" means a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (% by moles); This is how diene elastomers such as butyl rubbers or copolymers of dienes and of alpha-olefins of the EPDM type do not enter into the preceding definition and can be qualified in particular as "essentially saturated" diene elastomers (content of reasons of weak or very weak diene origin, always less than 15%). In the category of “essentially unsaturated” diene elastomers, the expression “highly unsaturated” diene elastomer is understood in particular to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

0045Among these diene elastomers, a distinction is also made between natural rubber and synthetic elastomers.

0046By synthetic diene elastomers capable of being used in accordance with the invention, more particularly means by diene elastomer:<ol id="ol0001" compact="compact" ol-style=""><li>(a) - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;</li><li>(b) - any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;</li><li>(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 of 6 to 12 carbon atoms, such as for example the elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene;</li><li>(d) - a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated, in particular chlorinated or brominated, versions of this type of copolymer.</li></ol>

0047As conjugated dienes, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C alkyl) are suitable, in particular.₁-VS₅) -1,3-butadienes such as for example 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3- butadiene, 2-methyl-3-isopropyl-1,3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Examples of vinyl aromatic compounds are styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tertiobutylstyrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene, vinylnaphthalene.

0048The copolymers can contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl aromatic units. The elastomers can have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used. The elastomers can be, for example, block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they can be coupled and / or starred or functionalized with a coupling and / or star-forming or functionalizing agent. For coupling to carbon black, mention may, for example, be made of functional groups comprising a C-Sn bond or amino functional groups such as aminobenzophenone for example; for coupling to an inorganic filler such as silica, mention may, for example, be made of silanol or polysiloxane functional groups having a silanol end (as described for example in<patcit id="pcit0003" dnum="FR2740778"><text>FR 2 740 778</text></patcit> or <patcit id="pcit0004" dnum="US6013718A"><text>US 6,013,718</text></patcit>, and <patcit id="pcit0005" dnum="WO2008141702A"><text>WO 2008/141702</text></patcit>), alkoxysilane groups (as described for example in <patcit id="pcit0006" dnum="FR2765882"><text>FR 2,765,882</text></patcit> or <patcit id="pcit0007" dnum="US5977238A"><text>US 5,977,238</text></patcit>), carboxylic groups (as described for example in <patcit id="pcit0008" dnum="WO0192402A"><text>WO 01/92402</text></patcit> or <patcit id="pcit0009" dnum="US6815473B"><text>US 6,815,473</text></patcit>, <patcit id="pcit0010" dnum="WO2004096865A"><text>WO 2004/096865</text></patcit> or <patcit id="pcit0011" dnum="US20060089445A"><text>US 2006/0089445</text></patcit>) or polyether groups (as described for example in <patcit id="pcit0012" dnum="EP1127909A"><text>EP 1,127,909</text></patcit> or <patcit id="pcit0013" dnum="US6503973B"><text>US 6,503,973</text></patcit>, <patcit id="pcit0014" dnum="WO2009000750A"><text>WO 2009/000750</text></patcit> and <patcit id="pcit0015" dnum="WO2009000752A"><text>WO 2009/000752</text></patcit>). As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type.

0049Polybutadienes are suitable and in particular those having a content (molar%) in units -1,2 between 4% and 80% or those having a content (molar%) of cis-1,4 greater than 80%, polyisoprenes, butadiene-styrene copolymers and in particular those having a Tg (glass transition temperature (Tg, measured according to ASTM D3418) of between 0 ° C and - 70 ° C and more particularly between - 10 ° C and - 60 ° C, a styrene content of between 5% and 60% by weight and more particularly between 20% and 50%, a content (molar%) of -1,2 bonds in the butadiene part of between 4% and 75%, a content ( molar%) in trans-1,4 bonds of between 10% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a Tg of -40 ° C. to - 80 ° C, isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between - 5 ° C. and - 50 ° C. In the case of butadiene-styrene-isoprene copolymers, those with a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15% and 60% are particularly suitable by weight and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content (molar%) in units -1.2 of the butadiene part between 4% and 85%, a content (molar%) in trans units -1.4 of the butadiene part between 6% and 80%, a content (molar%) in units -1.2 plus -3.4 of the isoprene part between 5% and 70% and a content (molar%) of trans units -1.4 of the isoprenic part of between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer having a Tg of between - 5 ° C and - 70 ° C.

0050In summary, the synthetic diene elastomer (s) according to the invention are preferably chosen from the group of highly unsaturated diene elastomers constituted by polybutadienes (abbreviated "BR"), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene copolymers- butadiene-styrene (SBIR).

0051As stated above, the liquid phase mixing methods are preferably used to allow masterbatches to be obtained 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 master mixture of diene elastomer and carbon black, use will more particularly be made of a diene elastomer latex, the elastomer latex being a particular form of the elastomer which is in the form of particles. of elastomer dispersed in water.

0052The invention therefore preferably relates to the latex of diene elastomers, the diene elastomers being those defined above.

0053More particularly, for natural rubber (NR) which is particularly suitable for the invention, this natural rubber exists in different forms, as detailed below. <nplcit id="ncit0001" npl-type="b"><text>chapter 3 "Latex concentrates: properties and composition", by KF Gaseley, ADT Gordon and TD Pendle in "Naturel Rubber Science and Technology", AD Roberts, Oxford University Press - 1988</text></nplcit>. In particular, several forms of natural rubber latex are marketed: so-called “field latex” natural rubber latex, “concentrated natural rubber latex”, epoxidized latex ("ENR"), deproteinized latex or even pre-vulcanized latex. Natural field rubber latex is a latex in which ammonia has been added to avoid early coagulation and the concentrated natural rubber latex corresponds to a field latex which has undergone a treatment corresponding to a washing followed by a new focus. The different categories of concentrated natural rubber latex are listed in particular according to standard ASTM D 1076-06. Among these concentrated natural rubber latexes, there are in particular concentrated natural rubber latexes of so-called quality: "HA" (high ammonia) and of so-called "LA" quality; Advantageously, HA quality concentrated natural rubber latex will be used for the invention. NR latex can be physically or chemically modified beforehand (centrifugation, enzymatic treatment, chemical modification, etc.) The latex can be used directly or be previously diluted in water to facilitate its use.

0054Thus, derived from synthetic elastomer latex, the latex may in particular consist of a synthetic diene elastomer already available in the form of an emulsion (for example a copolymer of butadiene and styrene, SBR, prepared in emulsion), or in a diene elastomer synthetic initially in solution (eg an SBR prepared in solution) which is emulsified in a mixture of organic solvent and water, generally by means of a surfactant.

0055Particularly suitable for the invention is an SBR latex, in particular an SBR prepared in emulsion ("ESBR") or an SBR prepared in solution ("SSBR"), and more particularly an SBR prepared in emulsion. There are two main types of emulsion copolymerization processes of styrene and butadiene, one of them, or hot process (implemented at a temperature close to 50 ° C), being suitable for the preparation of SBR very branched while the other, or cold process (implemented at a temperature which can range from 15 ° C to 40 ° C), makes it possible to obtain more linear SBRs. For a detailed description of the effectiveness of several emulsifiers which can be used in said hot process (as a function of the rates of said emulsifiers), one can for example refer to the two articles of <nplcit id="ncit0002" npl-type="b"><text>CW Carr, 1. M. Kolthoff, EJ Meehan, University of Minesota, Minneapolis, Minesota which appeared in Journal of Polymer Science of 1950, Vol. V, n ° 2, pp. 201-206</text></nplcit>, and of <nplcit id="ncit0003" npl-type="b"><text>1951, Vol. VI, n ° 1, pp. 73-81</text></nplcit>. Regarding comparative examples of implementation of said cold process, one can for example refer to article ½ <nplcit id="ncit0004" npl-type="s"><text>Industrial and Engineering Chemistry, 1948, Vol. 40, n ° 5, pp. 932-937</text></nplcit>, <nplcit id="ncit0005" npl-type="b"><text>EJ Vandenberg, GE Hulse, Hercules Powder Company, Wilmington, Delaware + and article ½ Industrial and Engineering Chemistry, 1954, Vol. 46, n ° 5, pp. 1065-1073, JR Miller, HE Diem, BF Goodrich Chemical Co</text></nplcit>., Akron, Ohio +.

0056In the case of an SBR elastomer (ESBR or SSBR), use is in particular of an SBR having an average styrene content, for example between 20% and 35% by weight, or a high styrene content, for example from 35 to 45%, a content of vinyl bonds in the butadiene part of between 15% and 70%, a content (molar%) of trans-1,4 bonds between 15% and 75% and a Tg of between - 10 ° C and - 55 ° C; such an SBR can advantageously be used in admixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.

0057It will be noted that it is possible to envisage using one or more natural rubber latexes in cutting, one or more synthetic rubber latexes in cutting or a cutting one or more natural rubber latexes with one or more synthetic rubber latexes.

0058As the second elastomer of the composition when it is not a diene elastomer, non-diene butyl elastomers such as poly (isobutylene) homopolymers or copolymers based on poly (isobutylene) are particularly suitable (of course in the case of copolymers with isoprene, we find the diene elastomers described above), as well as halogenated derivatives, in particular generally brominated or chlorinated, of these poly (isobutylene) homopolymers and copolymers based on poly (isobutylene). Also suitable among non-diene elastomers are copolymers of isobutylene and styrene derivatives such as isobutylene and brominated methylstyrene copolymers (BIMS) of which the elastomer named EXXPRO, sold by the company Exxon, is part. Mention may also be made, as non-diene elastomer which is particularly suitable for the invention, of non-diene thermoplastic elastomers (TPE).

0059Advantageously, the weight fraction of the first diene elastomer in the elastomeric matrix is ​​greater than or equal to 50% and preferably greater than or equal to 60%.

II-2) Expenses

0060As carbon blacks, all carbon blacks are suitable, in particular blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks). Among the latter, there may be mentioned more particularly the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example the blacks N115, N134, N234, N326, N330, N339, N347, N375, or even the intended applications, the blacks of higher series (for example N400, N660, N683, N772, N990). As carbon black, carbon blacks partially or entirely covered with silica by a post-treatment are also suitable, or carbon blacks modified in situ with silica such as, without limitation, the fillers which are marketed by the Cabot Corporation under the name Ecoblack ™ "CRX 2000" or "CRX4000". By "inorganic filler" should be understood here, in a known manner, any inorganic or mineral filler, whatever its color and its origin (natural or synthetic), also called "white" filler, "clear" filler or else filler "non-black" ("<i>non-black filler</i>") as opposed to carbon black, this inorganic filler being capable of reinforcing on its own, without other means than an intermediate coupling agent, a rubber composition intended for the manufacture of a tire tread, in d '' Other terms capable of replacing, in its reinforcement function, a conventional carbon black of pneumatic grade for tread. Such a filler is generally characterized by the presence of functional groups, in particular hydroxyl (-OH), on its surface, requiring to be used as reinforcing filler the use of a coupling agent or system intended to ensure chemical bonding stable between the isoprene elastomer and said filler. Such an inorganic filler can therefore be used with a coupling agent to allow the reinforcement of the rubber composition in which it is included. It can also be used with a covering agent (which does not provide a bond between the filler and the elastomeric matrix) in addition to a coupling agent or not (in this case the inorganic filler does not play a reinforcing role ).

0061The physical state in which the inorganic filler is present is immaterial, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term inorganic filler is also understood to mean mixtures of different inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below.

0062Mineral fillers of the siliceous type, in particular silica (SiO), are suitable as inorganic fillers.₂), or of the aluminous type, in particular of alumina (Al₂O₃). The silica used can be any silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface as well as a CTAB specific surface, both less than 450 m²/ g, preferably 30 to 400 m²/ g. As highly dispersible precipitated silicas (known as "HDS"), mention will be made, for example, of Ultrasil 7000 and Ultrasil 7005 from Evonik, Zeosil 1165MP, 1135MP and 1115MP from Rhodia, Hi-Sil EZ150G from the company PPG, the silicas Zeopol 8715, 8745 and 8755 from the company Huber, the silicas with high specific surface as described in the application<patcit id="pcit0016" dnum="WO0316837A"><text>WO 03/16837</text></patcit>.

0063When the compositions of the invention are intended for tire treads with low rolling resistance, the inorganic filler used, in particular if it is silica, preferably has a BET surface of between 45 and 400 m²/ g, more preferably between 60 and 300 m²/ g.

0064Preferably, inorganic fillers whose average size (by mass) is between 20 and 300 nm, more preferably between 20 and 150 nm, are particularly suitable for the present invention. This average size is measured conventionally after dispersion, by ultrasonic deagglomeration, of the filler for analysis in water or an aqueous solution containing a surfactant. For an inorganic filler such as silica, the measurement is carried out using a centrifugal sedimentometer with X-ray detection type "XDC" ("X-rays Disk Centrifuge"), sold by the company Brookhaven Instruments, according to the following operating mode . A suspension of 3.2 g of inorganic filler sample to be analyzed is produced in 40 ml of water, per action for 8 minutes, at 60% power (60% of the maximum position of the "output control"), d '' a 1500 W ultrasonic probe (3/4 inch Vibracell sonicator sold by the company Bioblock); after sonication, 15 ml of the suspension are introduced into the rotating disc at a speed varying between 3000 and 6000 revolutions per minute (the speed being adapted according to the average size of the load: the smaller the size, the faster the speed is high); after sedimentation for 120 minutes, the mass distribution of the particle sizes and the average mass size of the dw particles are calculated by the "XDC" sedimentometer software (dw = ∑ (neither di5) / ∑ (neither di4) with neither number objects of the size or diameter class di).

0065Preferably, the total charge rate (carbon black and inorganic charge such as silica) is between 20 and 200 phr, more preferably between 30 and 150 phr and even more preferably between 30 and 100 phr, the optimum being different known manner depending on the particular applications targeted: the level of reinforcement expected on a bicycle tire, for example, is of course lower than that required on a tire capable of traveling at high speed in a sustained manner, for example a motorcycle tire, a tire for a passenger vehicle or for a commercial vehicle such that Heavyweight.

0066According to a preferred embodiment of the invention, carbon black is used, the rate of which varies from 30 to 80 phr and an inorganic filler, in particular silica, the rate of which varies from 5 to 50 phr, more particularly the total charge of the composition comprising carbon black, the content of which varies from 35 to 70 phr and an inorganic filler, in particular of silica, the content of which varies from 5 to 35 phr, even more preferably the total charge comprising carbon black whose rate varies from 40 to 65 phr and an inorganic filler, in particular silica, whose rate varies from 10 to 30 phr.

II-3) Masterbatches - Rubber composition

0067Advantageously, the masterbatches and the compositions thus produced are capable of being used in tire applications.

0068The rubber compositions for tires based on masterbatches and inorganic filler according to the invention may also comprise, in a known manner, a coupling agent and / or a covering agent and a vulcanization system.

0069To couple the reinforcing inorganic filler to the diene elastomer, use is made in known manner of a coupling agent (or binding agent) at least bifunctional intended to ensure a sufficient connection, of chemical and / or physical nature, between the inorganic filler ( surface of its particles) and the diene elastomer, in particular bifunctional organosilanes or polyorganosiloxanes.

0070Use is made in particular of polysulphurized silanes, known as “symmetrical” or “asymmetrical” according to their particular structure, as described for example in the applications. <patcit id="pcit0017" dnum="WO03002648A"><text>WO03 / 002648</text></patcit> (or <patcit id="pcit0018" dnum="US2005016651A"><text>US 2005/016651</text></patcit>) and <patcit id="pcit0019" dnum="WO03002649A"><text>WO03 / 002649</text></patcit> (or <patcit id="pcit0020" dnum="US2005016650A"><text>US 2005/016650</text></patcit>).

0071Particularly suitable, without the following definition being limiting, so-called "symmetrical" polysulphurized silanes corresponding to the following general formula (III): <maths id="math0002" num="(III)"><math display="block"><mrow><mi mathvariant="normal">Z</mi><mo>−</mo><mi mathvariant="normal">AT</mi><mo>−</mo><msub><mi mathvariant="normal">S</mi><mi mathvariant="normal">x</mi></msub><mo>−</mo><mi mathvariant="normal">AT</mi><mo>−</mo><mi mathvariant="normal">Z</mi><mo>,</mo></mrow></math><img file="EP2652015B1_D0002.tif" /></maths>in which:<ul id="ul0005" list-style="dash" compact="compact"><li>x is an integer from 2 to 8 (preferably from 2 to 5);</li><li>A is a divalent hydrocarbon radical (preferably C alkylene groups₁-VS₁₈ or C arylene groups₆-VS₁₂, more particularly C alkylene₁-VS₁₀, especially in C₁-VS₄, in particular propylene);</li><li>Z has one of the following formulas:</li></ul><chemistry id="chem0001" num="0001"><img file="EP2652015B1_D0003.tif" /></chemistry>in which:<ul id="ul0006" list-style="dash" compact="compact"><li>the radicals R¹, substituted or unsubstituted, identical or different from each other, represent a C alkyl group₁-VS₁₈, C-cycloalkyl₅-VS₁₈ or C aryl₆-VS₁₈ (preferably C alkyl groups₁-VS₆, cyclohexyl or phenyl, especially C 1-4 alkyl groups₁-VS₄, more particularly methyl and / or ethyl).</li><li>the radicals R², substituted or unsubstituted, identical or different from each other, represent a C alkoxyl group₁-VS₁₈ or C-cycloalkoxyl₅-VS₁₈ (preferably a group chosen from C-alkoxyls₁-VS₈ and C-cycloalkoxyls₅-VS₈, more preferably still a group chosen from C alkoxyl₁-VS₄, in particular methoxyl and ethoxyl).</li></ul>

0072In the case of a mixture of polysulphurized alkoxysilanes corresponding to formula (III) above, in particular the usual mixtures commercially available, the average value of "x" is a fractional number preferably between 2 and 5, more preferably close to 4. However, the invention can also be advantageously implemented, for example with disulphurized alkoxysilanes (x = 2).

0073By way of examples of polysulphide silanes, mention will be made more particularly of the polysulphides (in particular disulphides, trisulphides or tetrasulphides) of bis- (alkoxyl (C₁-VS₄) -alkyl (C₁-VS₄) silyl-alkyl (C₁-VS₄)), such as for example bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides. Among these compounds, use is made in particular of bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated as TESPT, of formula [(C₂H₅O)₃If (CH₂)₃S₂]₂ or bis- (triethoxysilylpropyl) disulfide, abbreviated TESPD, of formula [(C₂H₅O)₃If (CH₂)₃S]₂. Mention will also be made, as preferred examples, of the polysulphides (in particular disulphides, trisulphides or tetrasulphides) of bis- (monoalkoxyl (C₁-VS₄) -dialkyl (C₁-VS₄) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide as described in the patent application <patcit id="pcit0021" dnum="WO02083782A"><text>WO 02/083782</text></patcit> (or <patcit id="pcit0022" dnum="US2004132880A"><text>US 2004/132880</text></patcit>).

0074By way of coupling agent other than polysulphurized alkoxysilane, mention may be made in particular of bifunctional POSs (polyorganosiloxanes) or also hydroxysilane polysulphides (R² = OH in formula III above) as described in the patent applications <patcit id="pcit0023" dnum="WO0230939A"><text>WO 02/30939</text></patcit> (or <patcit id="pcit0024" dnum="US6774255B"><text>US 6,774,255</text></patcit>) and <patcit id="pcit0025" dnum="WO0231041A"><text>WO 02/31041</text></patcit> (or <patcit id="pcit0026" dnum="US2004051210A"><text>US 2004/051210</text></patcit>), or else silanes or POSs bearing azo-dicarbonyl functional groups, as described for example in patent applications <patcit id="pcit0027" dnum="WO2006125532A"><text>WO 2006/125532</text></patcit>, <patcit id="pcit0028" dnum="WO2006125533A"><text>WO 2006/125533</text></patcit>, <patcit id="pcit0029" dnum="WO2006125534A"><text>WO 2006/125534</text></patcit>.

0075As a recovery agent, we will generally consider implementation aid agents which are known in a known manner, thanks to an improvement in the dispersion of the inorganic filler in the rubber matrix and to a lowering of the viscosity of the compositions, to improve their ability to be used in the raw state, these agents being, for example, hydrolysable silanes such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialcanol-amines), hydroxylated or hydrolysable POSs, for example α, ω-dihydroxy-polyorganosiloxanes (in particular α, ω-dihydroxy- polydimethylsiloxanes), fatty acids such as, for example, stearic acid.

0076In the rubber compositions in accordance with the invention, the content of coupling agent is preferably between 0.1 and 12% by mass of the inorganic filler for a CTAB surface of 160 m²/ g more preferably between 4 and 10% by mass of the inorganic load for a CTAB surface of 160 m²/ g; and / or the covering agent content is preferably between 0.1 and 20% by mass of the inorganic filler for a CTAB surface of 160 m²/ g more preferably between 5 and 20% by mass of the inorganic load for a CTAB surface of 160 m²/ g. The content of coupling agent can be adjusted to the specific surface area of ​​the filler.

0077Those skilled in the art will understand that, as an equivalent charge of the reinforcing inorganic charge described in this paragraph, a reinforcing charge of another nature, in particular organic, could be used, as soon as this reinforcing charge is covered with a inorganic layer such as silica, or else would have on its surface functional sites, in particular hydroxyls, requiring the use of a coupling agent to establish the connection between the filler and the elastomer.

0078These rubber compositions in accordance with the invention can also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, in particular treads, such as for example plasticizers or extension, whether these are aromatic or non-aromatic in nature, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents, reinforcing resins, acceptors (for example phenolic novolak resin) or methylene donors (for example HMT or H3M) as described for example in the application <patcit id="pcit0030" dnum="WO0210269A"><text>WO 02/10269</text></patcit>, a crosslinking system based either on sulfur, or on sulfur and / or peroxide and / or bismaleimide donors, vulcanization accelerators.

0079Preferably, these compositions comprise, as preferred non-aromatic or very weakly aromatic plasticizing agent, at least one compound chosen from the group consisting of naphthenic, paraffinic oils, MES oils, TDAE oils, esters (in particular trioleates) glycerol, plasticizing hydrocarbon resins having a high Tg preferably greater than 30 ° C, and mixtures of such compounds.

0080It will be noted that it is also possible to envisage making the masterbatches in accordance with the invention by incorporating therein, in particular before the drying phase, additives as described above, oil, antioxidant, coupling agent, covering agent ...

II-4). Manufacture of rubber compositions and masterbatches

0081The rubber compositions of the invention are produced in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first working or thermo-mechanical mixing phase (sometimes called a "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 mechanical working phase (sometimes called a "productive" phase) at a lower temperature, typically less than 120 ° C, for example between 60 ° C and 100 ° C, finishing phase during which the crosslinking or vulcanization system is incorporated.

0082According 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 intimately, by kneading, during the first so-called non-productive phase, that is to say, one introduces into the mixer and one thermomechanically kneads, in one or more stages, at least these different basic constituents until reaching the maximum temperature of between 130 ° C. and 200 ° C, preferably between 145 ° C and 185 ° C.

0083According to a preferred embodiment of the invention, the second elastomer and the inorganic filler are incorporated in the first diene elastomer and in carbon black which have been previously prepared in the form of a first masterbatch.

0084Preferably, this first masterbatch is produced in the "liquid" phase. To do this, use was made of the diene elastomer in the form of latex which is in the form of particles of elastomer dispersed in water, and of an aqueous dispersion of the carbon black because, that is to say say a charge dispersed in water, commonly called "slurry". Even more preferably, the process steps described in the document will be followed.<patcit id="pcit0031" dnum="US6048923A"><text>US 6,048,923</text></patcit>, 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, in incorporating a second continuous flow of a second fluid constituted by 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 almost complete coagulation of the elastomer latex with the carbon black before the outlet orifice of the coagulation reactor and then drying the coagulum obtained.

0085According to another preferred embodiment of the invention, the inorganic filler and the second elastomer are incorporated into the first masterbatch, also being in the form of a second masterbatch which has been previously prepared. This second masterbatch can be prepared in particular in solid form by thermomechanical mixing of the second elastomer and of the inorganic filler; it can also be prepared by any other process and in particular it can also be prepared in the liquid phase.

0086It 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 masterbatch containing the second elastomer and the inorganic filler, can be carried out simultaneously with the introduction into the mixer of the other constituents (in particular 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 the introduction of the second elastomer alone and of 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.

0087For example, the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer (such as a conventional internal mixer) (in the form where appropriate) masterbatches as specified above), any additional covering or processing agents and other various additives, with the exception of the vulcanization system. The total duration of the kneading, in this non-productive phase, is preferably between 1 and 15 min.

0088After the mixture thus obtained has cooled during the first non-productive phase, the vulcanization system is then incorporated at low temperature, generally in an external mixer such as a roller mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

0089The crosslinking system is preferably a vulcanization system, that is to say a system based on sulfur (or a sulfur donor agent) and on a primary vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the productive phase as described later, various secondary accelerators or known vulcanization activators such as zinc oxide , stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine).

0090Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr. The primary vulcanization accelerator is used at a preferential rate of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr.

0091Any compound capable of acting as an accelerator for vulcanization of diene elastomers in the presence of sulfur, in particular accelerators of the thiazole type and their derivatives, accelerators of the thiuram type, zinc dithiocarbamate, can be used as accelerator (primary or secondary). These accelerators are, for example, chosen from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), tetrabenzylthiuram disulfide ("TBZTD"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N, N -dicyclohexyl-2-benzothiazyle sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyle sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyle sulfenimide ("TBSI"), dibenzyldithiocarbamate zinc (" ZBEC ") and mixtures of these compounds.

0092The 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 also extruded in the form of a rubber profile usable for example as a tread tires for passenger vehicles, trucks etc.

<u>III EXAMPLES OF EMBODIMENT OF THE INVENTION</u>

III.1 Preparation of masterbatch of natural rubber and carbon black

0093The first masterbatches of diene elastomer and carbon black having a charge dispersion score in the elastomeric matrix greater than or equal to 90, are produced in the liquid phase according to the process described in the patent. <patcit id="pcit0032" dnum="US6048923A"><text>US Patent No 6,048,923</text></patcit>.

0094Thus, according to the protocol detailed in the aforementioned patent, a masterbatch is prepared from carbon black N234 marketed by the company Cabot Corporation, and natural field rubber latex (“field latex”) from Malaysia having an extract 28% dry rubber and 0.3% ammonia. A master mixture A of natural rubber and carbon black is thus obtained in which the carbon black content is 50 phr and which has a dispersion of the black in the natural rubber matrix having a Z score of 90.

III-2 Preparation of rubber compositions

0095The control compositions TM are produced according to a conventional method of mixing in solid form in which the elastomer (s), depending on whether the second elastomer is identical to or different from the first elastomer, and the reinforcing filler, including the carbon black N234 sold by the company Cabot corporation and, where appropriate, the precipitation silica Ultrasil 7000 sold by the company Evonik, are introduced in solid form.

0096The control rubber compositions TA not in accordance with the invention are produced from the masterbatch A to which is added according to a conventional method of mixing in solid form a second elastomer and carbon black N234 sold by the company Cabot Corporation.

0097The rubber compositions CA in accordance with the invention are produced from the first masterbatch A to which is added according to a conventional method of mixing in solid form a second elastomer and precipitation silica (powder or granules) Ultrasil VN3 or Ultrasil 7000 marketed by the company Evonik.

0098The different compositions are produced in the following manner:<ul id="ul0007" list-style="none" compact="compact"><li>The following tests are carried out as follows: the first masterbatch A for the TA and CA compositions (or natural rubber in solid form and carbon black) is introduced into an internal mixer, filled to 70% and whose initial tank temperature is approximately 90 ° C. N234 for TM compositions), a second elastomer, identical or different, a second reinforcing filler (carbon black N234 or silica Ultrasil VN3 or Ultrasil 7000), a coupling agent and / or a covering agent if necessary then, after one to two minutes of mixing, the various other ingredients except the vulcanization system. According to an alternative embodiment specified in some of the tests which follow, the second elastomer and the second reinforcing filler, and the coupling agent if necessary, are introduced in the form of a masterbatch produced beforehand in solid form.</li></ul>Thermomechanical work (non-productive phase) is then carried out in one step (total mixing time equal to approximately 5 min), until a maximum "falling" temperature of approximately 165 ° C. is reached.

0099The mixture thus obtained is recovered, cooled, then the vulcanization system (sulfur and sulfenamide accelerator) is added on an external mixer at 70 ° C, mixing the whole (productive phase) for about 5 to 6 min. When the recovery agent is present, the latter can also be introduced on an external mixer instead of the introduction on an internal mixer.

0100The compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or of thin sheets of rubber for the measurement of their physical or mechanical properties, or in the form of profiles which 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 treads.

0101In the variant embodiments specified in some of the tests which follow, the masterbatch of the second elastomer and the second filler (and of the coupling agent if applicable) is produced by the simultaneous introduction or not of the said second elastomer and the said second filler (and of the coupling agent if applicable) on an internal mixer then thermomechanical work is carried out (non-productive phase) in one step (total mixing time equal to approximately 5 min), until a maximum "fall" temperature of about 165 ° C.

III-3 Example 1

0102The purpose of this example is to demonstrate the properties of a rubber composition in accordance with the invention based on a blend of natural rubber and of copolymer of styrene and butadiene, SBR, improved with respect to compositions witnesses based on the same elastomeric blend not in accordance with the invention due to the nature of their reinforcing filler or to their preparation process.

0103The rubber compositions TM1 and TM2 are prepared “en masse” from a blend of natural rubber and an SBR, and of carbon black and, where appropriate, of silica, in solid form as detailed in the paragraph. III-2.

0104The control composition TA1 and the composition according to the invention CA2 are respectively prepared from a first masterbatch A into which are added in solid form a second elastomer, in this case an SBR, and a second reinforcing filler, respectively carbon black for TA1 or ultra-silica VN3 for CA2 according to the process detailed in paragraph III-2.

0105The control composition T'A1 and the composition according to the invention C'A2 are respectively prepared from a first masterbatch A into which are added in solid form a masterbatch prepared in also solid form and comprising a second elastomer and a second reinforcing filler, respectively carbon black for T'A1 or ultra-silica VN3 for C'A2 according to the process detailed in paragraph III-2.

0106All the compositions, whatever the manufacturing process, have the following basic formulation (in pce):<ul id="ul0008" list-style="dash" compact="compact"><li>natural rubber 80</li><li>SBR (a) 20</li><li>6PPD (b) 1.5</li><li>Plasticizer (c) 1</li><li>Stearic acid 2</li><li>Zinc oxide (d) 3</li><li>1.1 accelerator</li><li>sulfur 1.1<ol id="ol0002" compact="compact" ol-style=""><li>(a) SSBR with 25% of styrene 25% of polybutadiene units 1-2 and 50% of polybutadiene units 1-4 trans (Tg = - 48 ° C);</li><li>(b) N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine ("Santoflex 6-PPD" from the company Flexsys);</li><li>(c) MES oil ("Catenex SNR" from Shell)</li><li>(d) zinc oxide (industrial grade - Umicore company</li><li>(e) N-cyclohexyl-2-benzothiazyl-sulfenamide ("Santocure CBS" from the company Flexsys).</li></ol></li></ul>

0107In addition to these constituents, the compositions TM1, TM2, TA1, T'A1, CA2 and C'A2 are distinguished from each other by the nature and the rate (in pce) of second reinforcing filler which they include, detailed in the Table 1 below.<tables id="tabl0001" num="0001"><table frame="all"><title><u>Table 1</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="23mm" /><colspec colnum="6" colname="col6" colwidth="22mm" /><colspec colnum="7" colname="col7" colwidth="23mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM1</entry><entry align="center" valign="top">TM2</entry><entry align="center" valign="top">TA1</entry><entry align="center" valign="top">YOU'1</entry><entry align="center" valign="top">CA2</entry><entry align="center" valign="top">This a2</entry></row></thead><tbody><row><entry>N234 (1)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">40</entry><entry align="center">40</entry><entry align="center">40</entry><entry align="center">40</entry></row><row><entry>N234 (2)</entry><entry align="center">55</entry><entry align="center">40</entry><entry align="center">15</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry></row><row><entry>N234 (3)</entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center">15</entry><entry align="center">-</entry><entry align="center">-</entry></row><row><entry>Silica (4)</entry><entry align="center">-</entry><entry align="center">15</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">15</entry><entry align="center">-</entry></row><row><entry>Silica (5)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">1,5</entry></row><row><entry>Silane (6)</entry><entry align="center">-</entry><entry align="center">1,5</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">1,5</entry><entry align="center">1,5</entry></row></tbody></tgroup><tgroup cols="7" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="23mm" /><colspec colnum="6" colname="col6" colwidth="22mm" /><colspec colnum="7" colname="col7" colwidth="23mm" /><tbody><row><entry namest="col1" nameend="col7" align="justify">(1) carbon black from masterbatch A (2) carbon black added to the elastomeric blend or to the masterbatch A by standard mixing in solid form. (3) carbon black from the masterbatch containing the second elastomer added to the masterbatch A by standard mixing in solid form. (4) Silica Ultrasil VN3 added to masterbatch A by standard mixing in solid form. (5) Silica Ultrasil VN3 from the masterbatch containing the second elastomer added to the masterbatch A by standard mixing in solid form. (6) TESPT ("SI69" from Evonik);</entry></row></tbody></tgroup></table></tables>

0108The properties measured before and after well at 150 ° C. for 40 minutes are given in Table 2 which follows.<tables id="tabl0002" num="0002"><table frame="all"><title><u>Table 2</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="14mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM1</entry><entry align="center" valign="top">TM2</entry><entry align="center" valign="top">TA1</entry><entry align="center" valign="top">YOU'1</entry><entry align="center" valign="top">CA2</entry><entry align="center" valign="top">This a2</entry></row></thead><tbody><row><entry><u>Properties before</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Mooney</entry><entry align="center">56</entry><entry align="center">51</entry><entry align="center">51</entry><entry align="center">48</entry><entry align="center">40</entry><entry align="center">42</entry></row><row><entry><u>Properties after</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Note Z</entry><entry align="center">79</entry><entry align="center">45</entry><entry align="center">73</entry><entry align="center">71</entry><entry align="center">65</entry><entry align="center">70</entry></row><row><entry>MA 100</entry><entry align="center">2,1</entry><entry align="center">1,7</entry><entry align="center">2,2</entry><entry align="center">2,2</entry><entry align="center">1,9</entry><entry align="center">1,8</entry></row><row><entry>MA300 / MA100</entry><entry align="center">1,26</entry><entry align="center">1,09</entry><entry align="center">1,37</entry><entry align="center">1,43</entry><entry align="center">1,28</entry><entry align="center">1,28</entry></row><row><entry>Rupture deformation</entry><entry align="center">561</entry><entry align="center">612</entry><entry align="center">541</entry><entry align="center">547</entry><entry align="center">595</entry><entry align="center">609</entry></row><row><entry>Breaking stress</entry><entry align="center">25</entry><entry align="center">24</entry><entry align="center">25,4</entry><entry align="center">26,7</entry><entry align="center">24,5</entry><entry align="center">24,5</entry></row><row><entry>Tan (δ) max</entry><entry align="center">0,206</entry><entry align="center">0,167</entry><entry align="center">0,192</entry><entry align="center">0,196</entry><entry align="center">0,141</entry><entry align="center">0,144</entry></row></tbody></tgroup></table></tables>

0109The comparison of the control composition TM1 for which SBR and carbon black were added (55 phr) with the composition TM2 for which SBR and black (40 phr) and silica (15 phr) were added, shows that the introduction of silica, allows an expected improvement in hysteresis (drop in tanδ) as well as an advantage in deformation at break but at the expense of a significant deterioration in the dispersion of the reinforcing filler (note Z) as well as reinforcement (MA100 / M1300 ).

0110For the composition CA2 produced from the master mixture A having a good dispersion, in accordance with the invention, and compared with the composition TM2, it can be seen that the addition of SBR and silica to the master mixture makes it possible not only to lower the hysteresis but also to keep a good dispersion of the reinforcing filler in the composition and to improve the reinforcement (MA300 / MA100) making it possible to obtain values ​​close to the TM1 control. It is also noted that the lowering of the hysteresis (16%) and the increase in reinforcement (17%) for the composition CA2 in accordance with the invention compared to the control composition TM2, are surprisingly more important than what 'We observe with the addition of SBR and carbon black to the masterbatch by comparing the composition TA1 to the composition TM1 (7% hysteresis reduction and 8% gain in reinforcement).

0111The respective comparison of the compositions C'A2 and CA2 or T'A1 and TA1 shows that the mode of introduction of the second elastomer and of the second filler has no impact on the properties obtained. Thus, the compositions C'A2 and CA2 in accordance with the invention, compared with the control composition TM2 show an increase in the reinforcement and a decrease in the hysteresis greater than that which is obtained by comparing the compositions T'A1 and TA1 respectively. the TM1 composition.

III-4 Example 2

0112The purpose of this example is to demonstrate the properties of a rubber composition according to the invention based on natural rubber, improved with respect to control compositions based on the same elastomer not in accordance with the invention of fact of the nature of their reinforcing filler or their preparation process.

0113The rubber compositions TM3 and TM4 are prepared "in bulk" from natural rubber, and carbon black and, if appropriate, silica, in solid form as detailed in paragraph III-2.

0114The composition according to the invention CA4 is prepared from a first masterbatch A in which is added in solid form a second elastomer identical to the first elastomer therefore consisting of natural rubber and a second reinforcing filler, in this case the Ultrasil VN3 silica according to the process detailed in paragraph III-2.

0115The control composition T'A3 and the composition according to the invention C'A4 are respectively prepared from a first masterbatch A into which are added in solid form a masterbatch prepared in also solid form and comprising a second identical elastomer the first therefore consisting of natural rubber and a second reinforcing filler, respectively carbon black for T'A3 or ultra-silica VN3 for C'A4 according to the process detailed in paragraph III-2.

0116All the compositions, whatever the manufacturing process, have the following basic formulation (in pce):<ul id="ul0009" list-style="dash" compact="compact"><li>natural rubber (NR) 100</li><li>6PPD (b) 1.5</li><li>Plasticizer (c) 1</li><li>Stearic acid 2</li><li>Zinc oxide (d) 3</li><li>1.1 accelerator</li><li>sulfur 1.1</li></ul>

0117In addition to these constituents, the compositions TM3, TM4, TA3, T'A3, CA4 and C'A4 are distinguished from each other by the nature and the rate (in pce) of second reinforcing filler which they include, detailed in the following table 3.<tables id="tabl0003" num="0003"><table frame="all"><title><u>Table 3</u></title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="26mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="26mm" /><colspec colnum="6" colname="col6" colwidth="27mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM3</entry><entry align="center" valign="top">TM4</entry><entry align="center" valign="top">T'A3</entry><entry align="center" valign="top">CA4</entry><entry align="center" valign="top">C'A4</entry></row></thead><tbody><row><entry>N234 (1)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">42</entry><entry align="center">42</entry><entry align="center">42</entry></row><row><entry>N234 (2)</entry><entry align="center">55</entry><entry align="center">42</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry></row><row><entry>N234 (3)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">13</entry><entry align="center">-</entry><entry align="center">-</entry></row><row><entry>Silica (4)</entry><entry align="center">-</entry><entry align="center">13</entry><entry align="center">-</entry><entry align="center">13</entry><entry align="center">-</entry></row><row><entry>Silica (5)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">13</entry></row><row><entry>Silane (6)</entry><entry align="center">-</entry><entry align="center">1,3</entry><entry align="center">-</entry><entry align="center">1,3</entry><entry align="center">1,3</entry></row></tbody></tgroup><tgroup cols="6" rowsep="0"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="26mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="26mm" /><colspec colnum="6" colname="col6" colwidth="27mm" /><tbody><row><entry namest="col1" nameend="col6" align="justify">(1) carbon black from masterbatch A (2) carbon black added to the elastomeric blend by standard mixing in solid form. (3) carbon black from the masterbatch containing the second elastomer added to the masterbatch A by standard mixing in solid form. (4) Silica Ultrasil VN3 added to masterbatch A by standard mixing in solid form. (5) Silica Ultrasil VN3 from the masterbatch containing the second elastomer, added to masterbatch A by standard mixing in solid form. (6) TESPT ("SI69" from Evonik)</entry></row></tbody></tgroup></table></tables>

0118The properties measured before and after well at 150 ° C. for 40 minutes are given in Table 4 which follows.<tables id="tabl0004" num="0004"><table frame="all"><title><u>Table 4</u></title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="14mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM3</entry><entry align="center" valign="top">TM4</entry><entry align="center" valign="top">T'A3</entry><entry align="center" valign="top">CA4</entry><entry align="center" valign="top">C'A4</entry></row></thead><tbody><row><entry><u>Properties before</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Mooney</entry><entry align="center">89</entry><entry align="center">81</entry><entry align="center">80</entry><entry align="center">67</entry><entry align="center">66</entry></row><row><entry><u>Properties after</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Note Z</entry><entry align="center">66</entry><entry align="center">45</entry><entry align="center">79</entry><entry align="center">63</entry><entry align="center">77</entry></row><row><entry>MA 100</entry><entry align="center">2,5</entry><entry align="center">1,8</entry><entry align="center">2,7</entry><entry align="center">2,0</entry><entry align="center">1,9</entry></row><row><entry>MA300 / MA100</entry><entry align="center">1,24</entry><entry align="center">1,10</entry><entry align="center">1,32</entry><entry align="center">1,30</entry><entry align="center">1,34</entry></row><row><entry>Rupture deformation</entry><entry align="center">614</entry><entry align="center">628</entry><entry align="center">516</entry><entry align="center">610</entry><entry align="center">607</entry></row><row><entry>Breaking stress</entry><entry align="center">26,5</entry><entry align="center">23,1</entry><entry align="center">25,1</entry><entry align="center">26,1</entry><entry align="center">26,0</entry></row><row><entry>Tan (δ) max</entry><entry align="center">0,204</entry><entry align="center">0,162</entry><entry align="center">0,199</entry><entry align="center">0,136</entry><entry align="center">0,134</entry></row></tbody></tgroup></table></tables>

0119Comparison of the control composition TM3 for which NR and carbon black were added (55 phr) with composition TM4 for which NR and black (42 phr) and silica (13 phr) were added , shows that the introduction of silica allows an expected improvement in hysteresis (drop in tanδ) but at the expense of a significant deterioration in the dispersion of the reinforcing filler (note Z) as well as reinforcement (MA100 / M1300).

0120For the composition C'A4 produced from the master mixture A having a good dispersion, in accordance with the invention, and compared with the composition TM4, it can be seen that the addition to the masterbatch A of a masterbatch NR / silica previously produced in standard mixing in solid form makes it possible not only to lower the hysteresis but also to maintain good dispersion of the reinforcing filler in the composition and to improve the reinforcement (MA300 / MA100) allowing higher values ​​of the TM1 control to be obtained. It is also noted that the reduction in hysteresis (17%) and the increase in reinforcement (21%) for the composition C'A4 according to the invention compared with the control composition TM4, are surprisingly more important than what is observed with the addition to the masterbatch A of a masterbatch NR / carbon black previously produced in standard mixing in solid form by comparing the composition T'A3 with the composition TM3 ( 3% hysteresis reduction and 6% gain in reinforcement).

0121The respective comparison of the compositions C'A4 and CA4 shows that the mode of introduction of the second elastomer and of the second filler has no impact on the properties obtained. Thus the composition CA4, in accordance with the invention, compared to the control composition TM2 shows an increase in the strengthening and a decrease in the hysteresis comparable to what is obtained with the composition C'A4, in accordance with the invention, compared with the control composition TM2.

III-5 Example 3

0122The purpose of this example is to demonstrate the obtaining of the improved properties of compositions in accordance with the invention, based on natural rubber but having different reinforcing filler blends (carbon black and silica).

0123The rubber compositions TM5, TM6 and TM7 are prepared "en masse" from natural rubber, carbon black and silica, in solid form as detailed in paragraph III-2.

0124The compositions in accordance with the invention CA5, CA6 and CA7 are prepared from a first masterbatch A into which natural rubber and silica are added in solid form according to the process detailed in paragraph III-2.

0125All the compositions have a basic formulation identical to that of Example 2.

0126They are distinguished from each other by the rates (in phr) of carbon black and silica as specified in Table 5 below.<tables id="tabl0005" num="0005"><table frame="all"><title><u>Table 5</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="23mm" /><colspec colnum="3" colname="col3" colwidth="23mm" /><colspec colnum="4" colname="col4" colwidth="23mm" /><colspec colnum="5" colname="col5" colwidth="22mm" /><colspec colnum="6" colname="col6" colwidth="22mm" /><colspec colnum="7" colname="col7" colwidth="22mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM5</entry><entry align="center" valign="top">TM6</entry><entry align="center" valign="top">TM7</entry><entry align="center" valign="top">CA5</entry><entry align="center" valign="top">CA6</entry><entry align="center" valign="top">CA7</entry></row></thead><tbody><row><entry>N234 (1)</entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center">40</entry><entry align="center">35</entry><entry align="center">35</entry></row><row><entry>N234 (2)</entry><entry align="center">40</entry><entry align="center">35</entry><entry align="center">35</entry><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Silica (4)</entry><entry align="center">10</entry><entry align="center">10</entry><entry align="center">20</entry><entry align="center">10</entry><entry align="center">10</entry><entry align="center">20</entry></row><row><entry>Silane (6)</entry><entry align="center">1</entry><entry align="center">1</entry><entry align="center">2</entry><entry align="center">1</entry><entry align="center">1</entry><entry align="center">2</entry></row></tbody></tgroup><tgroup cols="7" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="23mm" /><colspec colnum="3" colname="col3" colwidth="23mm" /><colspec colnum="4" colname="col4" colwidth="23mm" /><colspec colnum="5" colname="col5" colwidth="22mm" /><colspec colnum="6" colname="col6" colwidth="22mm" /><colspec colnum="7" colname="col7" colwidth="22mm" /><tbody><row><entry namest="col1" nameend="col7" align="justify">(1) carbon black from masterbatch A (2) carbon black added to the elastomeric blend by standard mixing in solid form. (4) Ultrasil VN3 silica added to the elastomeric blend or to the masterbatch A by standard mixing in solid form. (6) TESPT ("SI69" from Evonik)</entry></row></tbody></tgroup></table></tables>

0127The properties measured before and after well at 150 ° C. for 40 minutes are given in Table 6 which follows.<tables id="tabl0006" num="0006"><table frame="all"><title><u>Table 6</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="14mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM5</entry><entry align="center" valign="top">TM6</entry><entry align="center" valign="top">TM7</entry><entry align="center" valign="top">CA5</entry><entry align="center" valign="top">CA6</entry><entry align="center" valign="top">CA7</entry></row></thead><tbody><row><entry><u>Properties before</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Mooney</entry><entry align="center">50</entry><entry align="center">49</entry><entry align="center">62</entry><entry align="center">38</entry><entry align="center">35</entry><entry align="center">49</entry></row><row><entry><u>Properties after</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>MA 100</entry><entry align="center">2,0</entry><entry align="center">1,8</entry><entry align="center">1,7</entry><entry align="center">2,2</entry><entry align="center">1,9</entry><entry align="center">2,0</entry></row><row><entry>MA300 / MA100</entry><entry align="center">1,20</entry><entry align="center">1,20</entry><entry align="center">1,10</entry><entry align="center">1,28</entry><entry align="center">1,31</entry><entry align="center">1,16</entry></row><row><entry>Rupture deformation</entry><entry align="center">574</entry><entry align="center">613</entry><entry align="center">636</entry><entry align="center">563</entry><entry align="center">580</entry><entry align="center">584</entry></row><row><entry>Breaking stress</entry><entry align="center">25,4</entry><entry align="center">26,8</entry><entry align="center">26,8</entry><entry align="center">25,5</entry><entry align="center">26,7</entry><entry align="center">24,4</entry></row><row><entry>Tan (δ) max</entry><entry align="center">0,128</entry><entry align="center">0,109</entry><entry align="center">0,139</entry><entry align="center">0,111</entry><entry align="center">0,083</entry><entry align="center">0,117</entry></row></tbody></tgroup></table></tables>

0128Compared to the control compositions TM5, TM6, TM7, it can be seen that the three compositions CA5, CA6 and CA7, in accordance with the invention and having different reinforcing charge cuts (but all belonging to the ranges of the present invention), all have the compromise of improved properties presented in the previous examples, namely a reduced Mooney value, an improved reinforcement (MA300 / MA100) and a very strong drop in hysteresis (16% to 24%) and this without degradation of the properties of deformation and stress at break.

III-6 Example 4

0129The purpose of this example is to demonstrate the properties of a rubber composition in accordance with the invention based on a blend of natural rubber and polybutadiene, BR, improved with respect to control compositions based on the same elastomeric cutting not in accordance with the invention due to the nature of their reinforcing filler or to their preparation process.

0130The rubber compositions TM8, TM9 and TM10 are prepared “en masse” from a blend of natural rubber and of a BR, and of carbon black and, if appropriate, of silica, in solid form as detailed in paragraph III-2.

0131The control composition TA8 and the compositions according to the invention CA9 and CA10 are respectively prepared from a first masterbatch A into which are added in solid form a second polybutadiene elastomer and a second reinforcing filler respectively of carbon black for the TA8 composition and silica for compositions CA9 and CA10, according to the process detailed in paragraph III-2.

0132All the compositions, whatever the manufacturing process, have the following basic formulation (in pce):<ul id="ul0010" list-style="dash" compact="compact"><li>natural rubber 80</li><li>BR (f) 20</li><li>6PPD (b) 1.5</li><li>Plasticizer (c) 1</li><li>Stearic acid 2</li><li>Zinc oxide (d) 3</li><li>1.1 accelerator</li><li>sulfur 1.1<ul id="ul0011" list-style="none" compact="compact"><li>(f) BR (Nd) with 0.7% of 1-2; 1.7% trans 1-4; 98% cis 1-4 (Tg = - 105 ° C);</li></ul></li></ul>

0133In addition to these constituents, the compositions TM8, TM9, TM10, TA8, CA9 and CA10 are distinguished from each other by the nature and the rate (in pce) of second reinforcing filler which they include, detailed in table 7 which follows.<tables id="tabl0007" num="0007"><table frame="all"><title><u>Table 7</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="33mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="22mm" /><colspec colnum="6" colname="col6" colwidth="24mm" /><colspec colnum="7" colname="col7" colwidth="24mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM8</entry><entry align="center" valign="top">TM9</entry><entry align="center" valign="top">TA8</entry><entry align="center" valign="top">CA9</entry><entry align="center" valign="top">TM10</entry><entry align="center" valign="top">CA10</entry></row></thead><tbody><row><entry>N234 (1)</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">40</entry><entry align="center">40</entry><entry align="center">-</entry><entry align="center">52</entry></row><row><entry>N234 (2)</entry><entry align="center">55</entry><entry align="center">40</entry><entry align="center">15</entry><entry align="center">-</entry><entry align="center">52</entry><entry align="center" /></row><row><entry>Silica (7)</entry><entry align="center">-</entry><entry align="center">15</entry><entry align="center">-</entry><entry align="center">15</entry><entry align="center">15</entry><entry align="center">15</entry></row><row><entry>Silane (6)</entry><entry align="center">-</entry><entry align="center">1,5</entry><entry align="center">-</entry><entry align="center">1,5</entry><entry align="center">1,5</entry><entry align="center">1,5</entry></row></tbody></tgroup><tgroup cols="7" rowsep="0"><colspec colnum="1" colname="col1" colwidth="33mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="22mm" /><colspec colnum="6" colname="col6" colwidth="24mm" /><colspec colnum="7" colname="col7" colwidth="24mm" /><tbody><row><entry namest="col1" nameend="col7" align="justify">(1) carbon black from masterbatch A (2) carbon black added to the elastomeric blend or to the masterbatch A by standard mixing in solid form. (6) TESPT ("SI69" from Evonik) (7) Silica Ultrasil 7000 added to the elastomeric cut or to the masterbatch A by standard mixing in solid form.</entry></row></tbody></tgroup></table></tables>

0134The properties measured before and after well at 150 ° C. for 40 minutes are given in Table 8 below.<tables id="tabl0008" num="0008"><table frame="all"><title><u>Table 8</u></title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="14mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="top">Composition</entry><entry align="center" valign="top">TM8</entry><entry align="center" valign="top">TM9</entry><entry align="center" valign="top">TA8</entry><entry align="center" valign="top">CA9</entry><entry align="center" valign="top">TM10</entry><entry align="center" valign="top">CA10</entry></row></thead><tbody><row><entry><u>Properties before</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Mooney</entry><entry align="center">65</entry><entry align="center">62</entry><entry align="center">54</entry><entry align="center">54</entry><entry align="center">64</entry><entry align="center">57</entry></row><row><entry><u>Properties after</u><u>cooking</u></entry><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /><entry align="center" /></row><row><entry>Note Z</entry><entry align="center">68</entry><entry align="center">61</entry><entry align="center">82</entry><entry align="center">85</entry><entry align="center">64</entry><entry align="center">88</entry></row><row><entry>MA 100</entry><entry align="center">2,3</entry><entry align="center">1,9</entry><entry align="center">2,2</entry><entry align="center">1,9</entry><entry align="center">2,3</entry><entry align="center">2,2</entry></row><row><entry>MA300 / MA100</entry><entry align="center">1,23</entry><entry align="center">1,10</entry><entry align="center">1,31</entry><entry align="center">1,21</entry><entry align="center">1,15</entry><entry align="center">1,32</entry></row><row><entry>Rupture deformation</entry><entry align="center">567</entry><entry align="center">616</entry><entry align="center">573</entry><entry align="center">630</entry><entry align="center">525</entry><entry align="center">507</entry></row><row><entry>Breaking stress</entry><entry align="center">26,0</entry><entry align="center">24,6</entry><entry align="center">26,1</entry><entry align="center">25,8</entry><entry align="center">22,4</entry><entry align="center">23,6</entry></row><row><entry>Tan (δ) max</entry><entry align="center">0,192</entry><entry align="center">0,164</entry><entry align="center">0,202</entry><entry align="center">0,150</entry><entry align="center">0,219</entry><entry align="center">0,198</entry></row></tbody></tgroup></table></tables>

0135The comparison of the control composition TM8 for which BR and carbon black were added (55 phr) with the composition TM9 for which BR and black (40 phr) and silica (15 phr) were added, shows that the introduction of silica, allows an expected improvement in hysteresis (drop in tanδ) as well as an advantage in deformation at break but at the expense of a deterioration in the dispersion of the reinforcing filler (note Z) as well as reinforcement (MA100 / M1300) .

0136For the composition CA9 produced from the master mixture A having a good dispersion, in accordance with the invention, and compared with the composition TM9, it can be seen that the addition of BR and silica to the master mixture not only makes it possible to lower the hysteresis but also to keep a good dispersion of the reinforcing filler in the composition and to improve the reinforcement (MA300 / MA100) allowing values ​​close to the TM8 control to be obtained. It is also noted that the lowering of the hysteresis (9%) and the increase in the reinforcement (10%) for the composition CA9 in accordance with the invention compared to the control composition TM9, are surprisingly greater than this. observed with the addition of BR and carbon black to the masterbatch by comparing the composition TA8 with the composition TM8 (5% increase in hysteresis and 7% gain in reinforcement).

0137Compared to the control composition TM10, it can be seen that the composition CA10 in accordance with the invention and having a reinforcing charge cut different from the composition in accordance with the invention CA9 (but belonging to the ranges of the present invention), presents the compromise of improved properties observed with the composition in accordance with the invention CA9, namely a reduced Mooney value, improved reinforcement (MA300 / MA100) (15%) and a drop in hysteresis (10%), without degrading the deformation and tensile strength properties.

0138All these examples showing compositions having an identical formulation (in particular the same fillers and the same rate of these fillers) but whose mode of preparation, demonstrate the synergy linked to the quality of the dispersion of the filler within the elastomeric matrix and to the nature of the filler added whatever the nature of the second elastomer.

0139It is surprisingly found that the addition of silica and elastomer to a masterbatch showing very good dispersion, unlike the addition of carbon black and elastomer to this same masterbatch, makes it possible to obtain the both good levels of dispersion, high reinforcement and very low hysteresis. These results demonstrate an advantage of the compositions in accordance with the invention in terms of wear, rolling resistance and heat of the tires using these compositions.