FR3057570A1 - PROCESS FOR THE PREPARATION OF A MASTER MIXTURE, COMPRISING A DIENE ELASTOMER, A REINFORCING ORGANIC CHARGE AND AN ANTIOXIDANT AGENT - Google Patents

Abstract

The subject of the invention is a process for preparing a masterbatch comprising a diene elastomer, a reinforcing filler and an antioxidant and having a dispersion of the reinforcing filler in the elastomeric matrix having a Z-score of greater than or equal to 80, the diene elastomer comprises at least natural rubber, the process comprising the following successive steps: a. Introduce, to obtain a dried mass, a coagulum in at least one heated continuous mixer; b. Pass the mass leaving the continuous mixer in a cylinder tool to obtain a ribbon; then c. Divide the master batch into two parts including a first and a second portion of the output flow of the cylinder tool; d. Introduce the antioxidant agent to the first part; e. Combine the first part and the second part; and F. Introducing the combined portions in a continuous mixer so as to obtain a masterbatch comprising an antioxidant; wherein all of the antioxidant present in the masterbatch obtained at the end of step f) is introduced in step d).

Description

Holder (s): COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN Limited partnership with shares, MICHELIN RECHERCHE ET TECHNIQUE S.A. Limited company.

Extension request (s)

Agent (s): MANUF FSE PNEUMATIQUES MICHELIN Limited partnership with shares.

FR 3 057 570 - A1 (54) PROCESS FOR THE PREPARATION OF A MASTER MIXTURE, COMPRISING A DENE ELASTOMER, A REINFORCING ORGANIC FILLER AND AN ANTIOXIDANT AGENT.

(© The subject of the invention is a process for preparing a masterbatch, comprising a diene elastomer, a reinforcing filler and an antioxidant agent and having a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 80, the diene elastomer comprises at least natural rubber, the process comprising the following successive steps:

at. Introduce, to obtain a dried mass, a coagulum in at least one continuous heated mixer;

b. Pass the mass leaving the continuous mixer through a cylinder tool to obtain a ribbon; then

vs. Divide the masterbatch into two parts including a first and a second part of the flow leaving the cylinder tool;

d. Introduce the antioxidant agent to the first part;

e. Combine the first part and the second part; and

f. Introduce the combined parts into a continuous mixer so as to obtain a masterbatch comprising an antioxidant agent;

wherein all of the antioxidant present in the masterbatch obtained at the end of step f) is introduced during step d).

i

Process for the preparation of a masterbatch comprising a diene elastomer, a reinforcing organic filler and an antioxidant agent

The present invention aims to improve the industrial efficiency of the processes for preparing masterbatches comprising a diene elastomer and a reinforcing organic filler finely dispersed in the elastomeric matrix.

The term “masterbatch” (commonly known by its English name “masterbatch”) means a composite based on an elastomer into which a filler and possibly other additives have been introduced. In the context of the present invention, the elastomer comprises natural rubber.

According to the invention, the masterbatch is particularly used for the manufacture of reinforced diene rubber compositions intended for the manufacture of tires or semi-finished products for tires, in particular treads for these tires.

In 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.

There are different methods for obtaining a masterbatch 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 elastomer particles 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 document US Pat. No. 6,048,923, 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 with respect 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 mixture 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.

The coagulum is usually dried to produce a masterbatch by a continuous process comprising the following successive steps:

Spinning (or "de-watering"), most often in an extruder. The product drained is usually called “pellet” to designate the coagulum granules. The level of volatile matter, mainly water, is usually 10% to 20% by weight.

Drying, mixing and plasticization (in English "masticate") in a continuous mixer, most often a Banbury mixer or a Unimix Continuous Mixer sold by Farrel Corporation (this mixer is also designated under the abbreviation "FCM"). During this step the mixture is chewed and heated. It is during this stage that the various optional additives are added, and in particular the antioxidant agent which is an additive considered to be necessary. The product recovered at the outlet is usually called "chunk" to denote the mass recovered. This mass is usually at a temperature ranging from 140 ° C to 200 ° C. The level of volatile matter, essentially water, is usually 1% to 3% by weight. In the presence of natural rubber in the elastomeric matrix, this mass has a very high Mooney viscosity (thus for higher carbon black levels at 65 phr, the Mooney viscosity is above the measurement capacities of the devices, ie greater than 200 MU; we can speak of "overtoque") and is therefore very difficult to work at a flow rate compatible with a manufacturing process. industrial scale. Thus, in practice, for black levels higher than 65 phr, at the outlet of the mixer part of the mass is sent to the cylinder tools, the rest is usually discarded. The rest can represent a significant quantity, which can for example correspond to half of the production leaving the mixer.

plasticization by passage of part of the mass recovered at the outlet of the continuous mixer in cylinder tools (in English Roll Mill). These cylinder tools are in contact with ambient air. At the outlet of the cylinder tools, the strip (or “strip”) usually has a temperature ranging from 110 ° C. to 160 ° C. and a volatile matter content of less than 1% by weight.

End of line which can notably include granulation steps, compaction in the form of bales, ...

Possibly storage.

Thus the current processes are not economical due to a significant loss (for example of almost half) of the production between the continuous mixing and plasticization stages due to the too high Mooney viscosity of the product when the elastomeric matrix comprises natural rubber.

Surprisingly, it has been found that it is possible to increase the flow rate of the plasticization step, which can be identical to the flow rate of the spinning and mixing steps. In other words, it has been found possible to send the entire mass leaving the continuous mixer to the cylinder tool (s).

The subject of the invention is thus a process for preparing a masterbatch, comprising a diene elastomer, a reinforcing filler and an antioxidant agent, and having a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 80, the diene elastomer comprises at least natural rubber, the process comprises the following successive stages:

a) Introducing, to obtain a dried mass, a coagulum into at least one continuous heated mixer, said coagulum comprises said diene elastomer and said reinforcing organic filler dispersed with a Z score greater than or equal to 80 in the dried mass;

b) Pass the mass leaving the continuous mixer through a cylinder tool to obtain a ribbon; then

c) Divide the masterbatch into two parts including a first part of the flow leaving the cylinder tool and a second part of the flow leaving the cylinder tool;

d) Introduce the antioxidant agent to the first part of the masterbatch;

e) Combine the first part and the second part of the masterbatch; and

f) introducing the combined parts into a continuous mixer so as to obtain a masterbatch comprising an antioxidant agent;

in which all of the antioxidant agent present in the masterbatch obtained at the end of step f) is introduced during step d).

In one embodiment, the two parts of the divided masterbatch comprise the first part with 20% of the output flow from the cylinder tool and the second part with 80% of the output flow from the cylinder tool.

In one embodiment, the method also comprises the step of recovering following step b) said masterbatch having a moisture content of less than 1% by weight

In one embodiment, all of the mass leaving the continuous mixer of step a) is sent to the cylinder tool of step b).

In one embodiment, the masterbatch advantageously has a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 90.

In one embodiment, prior to step a), the coagulum is obtained by mixing in the liquid phase from a latex of the diene elastomer and from an aqueous dispersion of the reinforcing organic filler. In particular, it is obtained according to the following stages:

- Supply a continuous flow of the latex of the diene elastomer to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet,

- Supply a continuous flow of a fluid comprising a reinforcing organic charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture,

- Wring out the coagulum obtained previously in order to recover the wrung out coagulum from step a).

In one embodiment, in step a), the continuous mixer is a 5 FCM. At the outlet of the continuous mixer of step a) the mass advantageously has a volatile matter content of less than 5% by weight. At the end of step b) the ribbon advantageously has a volatile matter content of less than 1% by weight.

In one embodiment, the reinforcing filler is a carbon black. The carbon black content is advantageously between 40 and 90 phr, preferably between 45 and 80 phr.

In one embodiment, the diene elastomer is advantageously a natural rubber.

In one embodiment, the antioxidant agent is an N-alkyl-N’-phenylparaphenyldiamine corresponding to formula (I):

wherein R ¹ represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms.

The subject of the invention is also a process for the preparation of a rubber composition comprising the following steps:

(A) Preparation of a masterbatch comprising a diene elastomer, a reinforcing filler and an antioxidant agent by the process according to the invention;

(B) Thermo-mechanical mixing at high temperature of the masterbatch obtained following step (A) with the other constituents of the rubber composition, with the exception of the vulcanization system; and (C) mechanical work at a temperature below the temperature of step (B) of the product resulting from step (B) and incorporation of the vulcanization system.

The inventors have indeed found that when part of the antioxidant is injected at the inlet of the continuous mixer, then it is possible to reduce the residence time of the masterbatch in the cylinder tool and also to increase the flow rate of the plasticization step, which can be identical to the flow rate of the spinning and mixing steps. Thus, the entire mass leaving the continuous mixer can be plasticized during production.

I- MEASUREMENTS AND TESTS

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

Mooney plasticity

An oscillating consistometer is used as described in French standard NF T 43-005 35 (1991). The Mooney plasticity measurement is made according to the following principle: the composition in the raw state (i.e., before baking) is molded in a cylindrical enclosure heated to 115 ° C. After 5 minutes of preheating, the rotor (small) rotates within the test tube at 0.04 revolutions / minute and the torque useful for maintaining this movement is measured after 10 minutes of rotation. The Mooney plasticity (MS 5 + 10) is expressed in Mooney unit (MU, with 1 MU = 0.83 Newton.meter). When the viscosity is too high, the rotor cannot turn and you cannot measure the torque.

Dispersion

In a known manner, the charge dispersion in an elastomeric matrix can be represented by the note Z, which is measured, after crosslinking, according to the method described by S. Otto and Al in Kautschuk Gummi Kunststoffe, 58 Jahrgang, NR 78 / 2005, in accordance with ISO standard 11345.

The calculation of note Z is based on the percentage of area in which the load is not dispersed ("% area not dispersed"), as measured by the "disperGRADER +" device supplied with its operating mode and its software. 'DisperDATA' operation by Dynisco according to the equation:

Z = 100 - (% area not dispersed) /0.35

The percentage of non-dispersed surface is measured by 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 high Z score, the better the dispersion of the charge in the elastomeric matrix (a Z score of 100 corresponding to a perfect dispersion and a Z score of 0 to a poor dispersion). It will be considered 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

These 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. We measure in second elongation (ie, after an accommodation cycle at the rate of extension provided for the measurement itself) the nominal secant module (or apparent stress, in MPa) at 100% elongation (noted MAI00). The tensile measurements to determine the secant accommodated modules are carried out at a temperature of 23 ° C +/- 2 ° C, and under normal humidity conditions (50 +/- 5% relative humidity).

Tearable

The tear off indices are measured at 100 ° C. One determines in particular the force to be exerted to obtain the rupture (FRD, in Mpa) on a test-tube of dimensions 10 x 105 x 2,5 mm notched in the center of its length on a depth of 5 mm, to cause the rupture of the test tube.

Dynamic properties

The dynamic properties and in particular tan (ô) max, representative of hysteresis, are measured on a viscoanalyzer (Metravib VA4000), according to the standard.

ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 4 mm thick and 400 mm ² in section) is recorded, subjected to a sinusoidal stress in alternating single shear, at the frequency of 10 Hz, under normal conditions of temperature (23 ° C) according to ASTM D 1349-99. A deformation amplitude sweep is carried out from 0.1% to 100% peak-peak (outward cycle), then from 100% to 0.1% peak-peak (return cycle). The exploited results are the complex dynamic shear modulus (G *) and the loss factor tan (ô). For the return cycle, we indicate the maximum value of tan (ô) observed, noted tan (ô) max.

Fatigue MFTR: MFTRA test:

The resistance to fatigue, expressed in number of cycles or in relative units (ur), is measured in a known manner on a non-notched test piece subjected to repeated low frequency pulling up to an elongation of 20%, at using a Monsanto device (MFTR type), until the test piece breaks, according to French standard NF T46-021.

II. DETAILED DESCRIPTION OF THE INVENTION

In 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 (i.e. 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).

"Pce" means "parts by weight per hundred parts of elastomer".

II-l) Process for preparing a masterbatch

The process for preparing a masterbatch according to the invention comprises the following successive steps:

a) Introducing, in order to obtain a dried mass, a coagulum into at least one continuous heated mixer, said coagulum comprises said diene elastomer and said reinforcing filler dispersed with a Z score greater than or equal to 80;

b) Pass the mass leaving the continuous mixer through a cylinder tool to obtain a ribbon; then

c) Divide the masterbatch into two parts including a first part of the output flow to the cylinder tool and a second part of the output flow to the cylinder tool;

d) Introduce the antioxidant agent to the first part of the masterbatch;

e) Combine the first part and the second part of the masterbatch; and

f) introducing the combined parts into a continuous mixer so as to obtain a masterbatch comprising an antioxidant agent;

in which all of the antioxidant agent present in the masterbatch obtained at the end of step d) is introduced during step c).

The method according to the invention allows that during step b) all of the mass leaving the continuous mixer is sent to said cylinder tool. Thus, compared to the processes of the prior art, significant savings are possible.

The flow rates of steps a) and b) are advantageously greater than 500 kg / h, more advantageously greater than 600 kg / h, for example ranging from 600 kg / h to 1300 kg / h.

The process being a continuous process and all of the mass leaving the continuous mixer being sent to the cylinder tool of step b), the flow rates of steps a) and b) are advantageously identical. By "identical debits" is meant, within the meaning of the present invention, flow rates not exceeding 10% of losses.

In step a), the coagulum advantageously has a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 90. The masterbatch obtained at the end of the process retains this very good dispersion. This step a) allows drying, mixing with any additives introduced into the mixer, and plasticization to obtain a masterbatch in the form of a dried mass. Any additives added do not include an antioxidant.

Prior to step a) the coagulum is advantageously obtained by mixing in the liquid phase from a latex of the diene elastomer and from an aqueous dispersion of the reinforcing organic filler.

In particular, the coagulum is obtained according to the following steps:

Feeding a continuous flow of the latex of the diene elastomer to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet,

- Supply a continuous flow of a fluid comprising a reinforcing organic charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture,

- Wring out the coagulum obtained previously in order to recover the wrung out coagulum from step a).

The coagulum introduced during step a) is advantageously in the form of granules.

The coagulum introduced during step a) has advantageously been wrung to a volatile matter content ranging from 8% to 20% by weight, usually around 15% by weight. Volatile matter is mainly water.

The coagulum is advantageously introduced during step a) at a flow rate greater than 500 kg / h, more advantageously greater than 600 kg / h, even more advantageously ranging from 600 kg / h to 1300 kg / h.

During step a) the continuous mixer is advantageously an FCM. Conventionally, at the outlet of the continuous mixer of step a), or of the last continuous mixer when several mixers are used, the mass is at a temperature between 140 ° C. and 200 ° C.

At the outlet of the continuous mixer of step a), or of the last continuous mixer when several mixers are used, the mass advantageously has a volatile matter content of less than 5% by weight.

Often, as soon as the level of reinforcing organic filler is 65 phr or more, at the outlet of the continuous mixer of step a), or of the last continuous mixer when several mixers are used, the mass has a Mooney viscosity greater than 200 UM. That is, the mass has such a high Mooney viscosity that it cannot be measured.

Step b) allows a plasticization of the dried mass obtained following step a). A masterbatch in the form of a ribbon is obtained at the outlet of the cylinder tools.

The flow rate of step b) is advantageously greater than 500 kg / h, more advantageously greater than 600 kg / h, even more advantageously ranging from 600 kg / h to 1300 kg / h.

During step b), the entire mass at the outlet of the continuous mixer of step a), or of the last continuous mixer when several mixers are used, is sent to the cylinder tool (s).

Following the plasticization, a ribbon is recovered. This ribbon, at the outlet of step b), is advantageously at a temperature between 110 ° C and 160 ° C. This tape, at the output of step b), advantageously has a volatile matter content of less than 1% by weight, generally from 0.3% to 0.5% by weight.

The flow rate of step b) is advantageously greater than 500 kg / h, more advantageously greater than 600 kg / h, even more advantageously ranging from 600 kg / h to 1300 kg / h.

Following these steps, the ribbon, at the outlet of the cylinder tool, is introduced into a continuous mixer. Any type of continuous mixer can be used, the extruders being for example well suited.

Other additives can be added. They are preferably added during step a) but they can also be added during step f). By way of example of these other additives, mention may, for example, be made of fillers (which may be identical or different from the fillers already present in the coagulum; as an example of fillers, mention may be made of zinc oxide), d other diene elastomers which meet the definitions given below, of other masterbatch or a complement of masterbatch provided that they do not contain an antioxidant agent if they are added during step a) , plasticizers, processing aids (e.g. stearic acid, liquid polymers, oil, hydrocarbon waxes), resins, flame retardants, extension oils, lubricants, stabilizers ( such as hydroxylamine sulfate), and mixtures thereof.

By the method according to the invention it is possible to lower the Mooney viscosity of the mixture without degrading its properties. This significantly improves the processability of the mixture on the rollers of the cylinder tool and therefore increases the flow rate on this cylinder tool (s).

It can be seen that the ribbon is little torn and that the ribbon obtained is homogeneous (no tearing at the edges) and easy to work (absence of tendrils).

Step c) allows the masterbatch to be divided into two parts, including a first part of the flow leaving the cylinder tool and a second part of the flow leaving the cylinder tool. The antioxidant is introduced to the first part of the masterbatch. The first part and the second part of the masterbatch are combined, and the combined parts are introduced into a continuous mixer so as to obtain a masterbatch comprising an antioxidant agent.

During step d), all of the antioxidant agent present in the masterbatch obtained at the end of step f) is introduced.

The two parts of the divided masterbatch comprise the first part with 20% of the output flow from the cylinder tool and the second part with 80% of the output flow from the cylinder tool. By deriving 20% of the flow rate at the outlet of the cylinder tool, by introducing 5 phr of antioxidant therein, and by recombining these 20% of the total flow at 80% not loaded with antioxidant at the inlet of the continuous mixer, we obtain a product loaded with 1 pce of antioxidant.

Any type of continuous mixer can be used. For example, extruders are well suited.

II-2) Diene elastomer

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

By elastomer or diene rubber, must be understood in known manner an elastomer derived at least in part (i.e., a homopolymer or a copolymer) of diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

These diene elastomers can be classified into two categories: essentially unsaturated or essentially saturated. Generally understood by essentially unsaturated, a diene elastomer derived at least in part from conjugated diene monomers, having a rate of units or units of diene origin (conjugated dienes) which is greater than 15% (% by moles); This is how diene elastomers such as butyl rubbers or copolymers of dienes and of alpha-olefins of the EPDM 20 type do not enter into the preceding definition and can be qualified in particular as essentially saturated diene elastomers (proportion of units of weak or very weak diene origin, always less than 15%). In the category of essentially unsaturated diene elastomers, the term “highly unsaturated diene elastomer” is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

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

By synthetic diene elastomers capable of being used in accordance with the invention, more particularly means by diene elastomer:

(a) - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

(b) - any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;

(c) - a ternary copolymer obtained by copolymerization of ethylene, of an aolefin 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;

(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.

As conjugated dienes, 1,3-butadiene, 2-methyl-1,3butadiene, 2,3-di (C1-C5 alkyl) -1,3-butadienes such as, for example, 2,3-dimethyl are suitable. -1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, an ary 1-1,3-butadiene, 1,3-pentadiene, 2,4hexadiene. Examples of vinyl aromatic compounds are styrene, ortho-, meta-, para-methylstyrene, the commercial vinyl-toluene mixture, paratertiobutylstyrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene, vinylnaphthalene.

The 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 amine 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 FR 2 740 778 or US6013 718, and WO 2008/141702), alkoxysilane groups (as described for example in FR 2 765 882 or US 5 977 238), carboxylic groups (as described for example in WO 01/92402 or US 6 815 473, WO 2004/096865 or US 2006/0089445) or also polyether groups (as described for example in EP 1 127 909 or US 6 503 973, WO 2009/000750 and WO 2009/000752). As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type.

Polybutadienes are suitable and in particular those having a content (molar%) in units -1,2 of 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 between 5% and 60% by weight and more particularly between 20% and 50%, a content (molar%) of -1,2 bonds of the butadiene part 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 re - 5 ° C. and - 50 ° C. In the case of butadiene-styrene-isoprene copolymers, those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40% are suitable, a isoprene content between 15% and 60% by weight and more particularly between 20% and 50%, a butadiene content between 5% and 50% by weight and more particularly between 20% and 40%, a content ( molar%) in units -1.2 of the butadiene part of between 4% and 85%, a content (molar%) in trans units -1.4 of the butadiene part of between 6% and 80%, a content (% molar) in units -1.2 plus -3.4 of the isoprenic part between

5% and 70% and a content (mol%) 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.

In 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 to BR), synthetic polyisoprenes (IR), butadiene copolymers, copolymers of isoprene 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 i soprene-butadiene copolymers - styrene (SBIR).

As stated above, the liquid phase mixing methods are preferably used to allow masterbatches to be obtained based on diene elastomer and reinforcing organic filler having a very good dispersion of the reinforcing organic filler in the elastomer. Thus, in particular for the production of the master mixture of diene elastomer and of reinforcing organic filler, 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 d elastomer dispersed in water. The invention therefore preferably relates to the latex of diene elastomers, the diene elastomers being those defined above.

More particularly, for natural rubber (NR) which composes all or part of the elastomer according to the invention, this natural rubber exists in different forms as detailed in Chapter 3 "Latex concentrates: properties and composition", by K.F. Gaseley, A.D.T. Gordon and TD Pendle in "Naturel Rubber Science and Technology", AD Roberts, Oxford University Press - 1988. In particular, several forms of natural rubber latex are marketed: so-called "field latex" , so-called “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 prevent 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. The NR latex can be modified physically or chemically beforehand (centrifugation, enzymatic treatment, chemical modification, etc.) The latex can be used directly or be previously diluted in water to facilitate its implementation.

It will be noted that it is possible to envisage using one or more natural rubber latexes as a blend, or a blend of one or more natural rubber latexes with one or more synthetic rubber latexes.

Thus, 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 as an emulsion), or in a diene elastomer synthetic initially in solution (for example an SBR prepared in solution) which is emulsified in a mixture of organic solvent and water, generally by means of a surfactant.

Particularly 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 by 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, and 1951, Vol. VI, n ° 1, pp. 7381. Concerning comparative examples of implementation of said cold process, one can for example refer to the article Vi Industrial and Engineering Chemistry, 1948,

Flight. 5 40, n ° 5, pp. 932-937, E. J. Vandenberg, G. E. Hulse, Hercules Powder Company, Wilmington, Delaware + and in the article Vi Industrial and Engineering Chemistry, 1954, Vol. 46, n ° 5, pp. 1065-1073, J. R. Miller, H. E. Diem, B. F. Goodrich Chemical Co., Akron, Ohio.

In 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 mixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.

II-3) Reinforcing filler

The reinforcing filler comprises a reinforcing organic filler. As reinforcing organic filler, all carbon blacks are suitable. As carbon blacks, all carbon blacks, in particular blacks of the HAF type, are suitable,

ISAF, SAF conventionally used in tires (black known as pneumatic grade). 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 NI 15, N134, N234, N326, N330, N339, N347, N375, or else, depending on 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 sold by the company Cabot Corporation under the name EcoblackTM "CRX 2000" or "CRX4000".

One could consider using the reinforcing organic filler alone or in combination with a reinforcing inorganic filler. 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 non-black filler (non black filler) as opposed to carbon black, this inorganic filler being capable of reinforcing on its own, without other means than a possible intermediate coupling agent, a rubber composition intended for the manufacture of a tire tread, in other words able to replace, 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, which may require to be used as reinforcing filler the use of a coupling agent or system intended to ensure a bond stable chemical between the isoprene elastomer and said filler. Such an inorganic filler can therefore be used alone or with a coupling agent to allow the reinforcement of the rubber composition in which it is included. The 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. As inorganic fillers, in particular mineral fillers of the siliceous type, in particular silica (S1O2), or of the aluminous type, in particular of alumina (AI2O3) are suitable. The silica used can be any silica known to those 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 m ² / g, preferably from 30 to 400 m ² / g. As highly dispersible precipitated silicas (known as HDS), mention may be made, for example, of the Ultrasil 7000 and Ultrasil 7005 silicas from the company Evonik, the Zeosil 1165MP silicas,

1135MP and 1115MP from the company Rhodia, the Hi-Sil silica 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 application WO 03/16837.

To couple the reinforcing inorganic filler to the diene elastomer, use is made in known manner of a coupling agent (or bonding 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. Polysulphurized silanes, said to be symmetrical or asymmetrical according to their particular structure, are used in particular, as described for example in applications WO03 / 002648 (or US 2005/016651) and W003 / 002649 (or US 2005/016650).

Preferably, the total charge rate (carbon black and, where appropriate, inorganic charge such as silica) is between 40 and 200 phr, more preferably between 40 and 150 phr and even more preferably between 40 and 100 phr, the optimum being known in different ways according to 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 passenger vehicles or for commercial vehicles such as Heavy goods vehicles.

According to one embodiment of the invention, the reinforcing filler is carbon black. Carbon black is advantageously used, the rate of which varies from 40 to 90 phr, advantageously from 45 to 80 phr.

Advantageously, the masterbatch does not include a coupling agent, even in the presence of an inorganic reinforcing filler.

Advantageously, the masterbatches and the compositions thus produced are capable of being used in applications for tires. The rubber compositions for tires based on masterbatches and inorganic filler according to the invention can also comprise, in a known manner, a covering agent and, where appropriate, a coupling agent.

II-4) Antioxidant agent

One or more antioxidants can be used as the antioxidant. The antioxidant agent can be of the amine, phenol, imidazole, metal salt of carbamate, para-phenylene diamine (s) and / or dihydrotrimethylquinoline (s), polymerized quinine, wax or any other antioxidant commonly used in elastomer formulations. .

By way of specific example, there may be mentioned: N- (1,3-dimethylbutyl) -N'-phenyl-pphenylenediamine (6-PPD, sold for example under the brands

ANTIGENE® 6C by Sumitomo Chemical Co., Ltd. NOCLAC® 6C by Ouchi Shinko

Chemical Industrial Co., Ltd.), the Ozonon 6C product marketed by Seiko

Chemical Co., Ltd., 1,2-dihydro-2,2,4-trimethyl quinoline polymerized (TMQ, sold for example under the brand Agerite Resin D, by RT Vanderbilt), butylhydroxytoluene (BHT), and butylhydroxyanisole (BHA ).

The antioxidant agent is advantageously an N-alkyl-N’-phenylparaphenyldiamine corresponding to formula (I):

(I) in which R ¹ represents an alkyl group, linear or branched, having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms.

Preferably, R ¹ represents an alkyl having from 2 to 8 carbon atoms, preferably chosen from the group consisting of ethyl, propyl (ie, n-propyl, isopropyl), butyl (ie, n-butyl, sec-butyl and tert -butyl), pentyl, hexyl, heptyl and octyl, or a cycloalkyl group having 5 to 8 carbon atoms (cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl), more preferably a cyclohexyl group.

More preferably, compounds are used whose R ¹ groups are branched, of formulas (I -bis) below:

(I-bis) in which R ⁴ , R ⁵ , identical or different from each other, each represent an alkyl group the number of carbon atoms of which conforms to the preferred definitions given above for R ¹ .

As more preferred examples of branched radicals R ¹ , mention will be made in particular of isopropyl, 1,3-dimethylbutyl and 1,4-dimethylpentyl.

The compounds of formula (I-bis) above are well known to those skilled in the art. They have been used for a very long time as anti-aging protection agents in rubber compositions for tires, in particular in the belts of such tires, and belong to the family of derivatives of paraphenylenediamine (PPD) such as for example N-isopropyl- N'-phenylparaphenylenediamine (I-PPD)

or N-1,3-dimethylbutyl-N'-phenyl-paraphenylene diamine (6-PPD)

both excellent antioxidants and antiozonants (see for example applications

WO 2004/033548, WO 2005/063510, WO 2005/133666).

The antioxidant agents are usually introduced in an amount ranging from 0.5 phr to 5 phr.

II-5) Other additives

These 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 the latter are of an aromatic or non-aromatic nature, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-fatigue agents, reinforcing resins, acceptors (for example phenolic resin novolak) or methylene donors (for example HMT or H3M) as described for example in application WO 02/10269, a crosslinking system based either on sulfur or on sulfur and / or peroxide and / or donor of bismaleimides, vulcanization accelerators.

Preferably, 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 trio leates ) of glycerol, the plasticizing hydrocarbon resins having a high Tg preferably greater than 30 ° C, and mixtures of such compounds. It 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 of the production of the masterbatch in the liquid phase, additives as described above, oil, antioxidant, coupling agent, collection agent, etc.

II-6) Manufacture of rubber compositions:

The subject of the invention is also a process for the preparation of a rubber composition comprising the following steps:

A) Preparation of a masterbatch comprising a diene elastomer, a reinforcing organic filler and an antioxidant agent by the process according to the invention;

B) Thermo-mechanical mixing at high temperature of the masterbatch obtained following step A) with the other constituents of the rubber composition, with the exception of the vulcanization system;

C) mechanical work at a temperature lower than the temperature in step B) of the product resulting from step B) and incorporation of the vulcanization system.

The rubber compositions of the invention are produced in suitable mixers, using two successive preparation phases (steps B) and C)) according to a general procedure well known to those skilled in the art: a first working or kneading phase thermo-mechanical (sometimes called non-productive phase) at high temperature, up to a maximum temperature between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second phase mechanical work (sometimes called the productive phase) at a lower temperature, typically below 120 ° C, for example between 60 ° C and 100 ° C, the finishing phase during which the crosslinking or vulcanization system is incorporated.

According to one embodiment of the invention, all the basic constituents of the compositions of the invention, with the exception of the vulcanization system, are incorporated intimately, by kneading, during the first so-called non-productive phase, that is to say, one introduces into the mixer and kneads thermomechanically, in one or more steps, 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.

According to a preferred embodiment of the invention, the basic constituents of the compositions of the invention, with the exception of the vulcanization system, are incorporated into the diene elastomer and the reinforcing filler which have been previously prepared in the form of a first masterbatch.

This first masterbatch is carried out in the "liquid" phase. To do this, use was made of the diene 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 carbon black, that is to say a charge dispersed in water, commonly known as a slurry. More preferably still, the process steps described in document US Pat. No. 6,048,923 will be followed, which consists in particular in incorporating a continuous flow of a first fluid consisting of the elastomer latex into the mixing zone of a coagulation reactor, 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 the elastomer latex to be coagulated almost completely with the carbon black before the outlet orifice of the coagulation reactor and then to dry the coagulum obtained according to the process of the invention.

According to another preferred embodiment of the invention, an inorganic filler and a 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 the inorganic filler; it can also be prepared by any other process and in particular it can also be prepared in the liquid phase.

It will be noted in particular that in the case of the incorporation of a second elastomer and / or an inorganic filler, this or these incorporations 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.

It will be noted that in the case of adding an inorganic filler and a second elastomer, these can be introduced separately or in the form of a second masterbatch containing the second elastomer and the inorganic filler. 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.

By way of 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 recovery 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. After 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 cylinder mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

The 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).

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

Any compound capable of acting as an accelerator for the 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 2mercaptobenzothiazyle disulfide (abbreviated MBTS), tetrabenzylthiuram disulfide (TBZTD), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N, N-dicyclohexyl-2benzothiazyle sulfenamide (DCBS) , N-ter-butyl-2-benzothiazyl sulfenamide (TBBS), N-ter-butyl-2-benzothiazyl sulfenimide (TBSI), zinc dibenzyldithiocarbamate (ZBEC) and mixtures of these compounds.

The final composition thus obtained is then calendered for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or also extruded in the form of a rubber profile usable for example as a tread tires for passenger vehicles, trucks etc.

It should be noted that such a composition can advantageously constitute the entire tread. However, the invention also applies to cases where these rubber compositions form only part of a composite tread consisting for example of two radially superposed layers of different formulations (so-called cap-base structure), both intended to enter in contact with the road during the rolling of the tire, during the life of the latter. The part based on compositions in accordance with the invention may then constitute the radially external layer of the tread intended to come into contact with the ground from the start of rolling of the new tire, or on the contrary its radially internal layer intended to come into contact with the ground later.

III EXAMPLES OF IMPLEMENTATION OF THE INVENTION

Example 1

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

The coagulum of natural rubber (100 phr) and of carbon black (72 phr) having a very good note of dispersion of the filler in the elastomeric matrix are produced in the liquid phase according to the method described in patent U. S. Patent No 6,048,923.

They are then dried according to the following processes:

Ml masterbatch (not according to the invention):

At the outlet of the wringer, pellets at a flow rate of 700 kg / h of dry product and loaded with 15% volatile matter (mainly water) are sent to the FCM. 6-PPD is injected at the inlet of the FCM at a rate of 1.2 phr.

At the outlet of the FCM, the mixture called chunk leaves at 165 ° C. and a volatile matter content of between 1 and 3%. The Mooney viscosity measured for this composite (MS) is> 200 and therefore cannot be measured by the machine (overtorque).

Just out of the FCM, only half of the production (350kg / h) is sent to the cylinder tool (Roll Mill), the other half is thrown away.

At the exit of the Roll Mill tool, the composite has a temperature around 155 ° C, a Mooney viscosity of 150-170 on average and a volatile matter content <1%, generally around 0.4 %. This composite RM output, called strip, is then sent towards the end of the line.

Masterbatch M2 (according to the invention):

At the exit of the wringer, pellets at a flow rate of 750 kg / h dry product and loaded with 15% volatile matter (mainly water) are sent to the FCM. With this recipe, there is no injection of 6-PPD into the FCM.

At the outlet of the FCM, the mixture called chunk leaves at 165 ° C. and a volatile matter content of between 1 and 3%. The Mooney viscosity measured for this composite (MS) is> 200 and therefore cannot be measured by the machine (overtorque).

Tl

At the exit of the FCM, the entire production (750kg / h) is sent to the cylinder tool (Roll Mill).

At the exit of the Roll Mill tool, the composite has a temperature around 155 ° C, a Mooney viscosity between 125 and 145 and a volatile matter content <1%, generally around 0.4%.

This composite called strip is then sent to the prebreaker where it is mixed with 1.2 pce of 6-PPD. At the exit of prebreaker the composite is sent towards the end of the line.

III-2 Preparation of rubber compositions

Fes different compositions were made from the master mixture Ml or

M2.

The following tests are carried out as follows: the master mixture Ml or M2 is introduced into an internal mixer, filled to 70% and whose initial tank temperature is approximately 60 ° C. Thermomechanical work is then carried out (non-productive phase) in one step (total mixing time equal to approximately 5 min), until a maximum drop temperature of approximately 165 ° C is reached.

The mixture thus obtained is recovered, it is cooled and 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.

The 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.

III-3 Mechanical properties

The purpose of this example is to demonstrate that the properties of a rubber composition obtained with a masterbatch in accordance with the invention have the same mechanical properties as a masterbatch obtained by a conventional process.

Composition C1, not in accordance with the invention, is prepared from a master mixture Ml according to the process detailed in paragraph III-2.

Composition C2 according to the invention is prepared from a masterbatch M2 according to the process detailed in paragraph III-2.

All the compositions have the following basic formulation (in pce):

natural rubber 100 carbon black N234 72 6-PPD (1) 2 Stearic acid 1.5 ZnO (2) 2.5 Sulfur 1.1 CBS (3) 1.1

Table 1 (1) 6-PPD: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine: antioxidant (2) ZnO: Zinc Oxide (3) N-cyclohexyl-2-benzothiazyl-sulfenamide ( "Santocure CBS" of the company

Flexsys); accelerator

The properties measured after baking at 130 ° C for 60 minutes are given in Table 2 below.

Cl C2 MA300 / MA100 1.5 1.6 MFTR (kcycles) 78.6 81.8 G * (MPa) 1.7 1.6 Tan (ô) max 0.22 0.21

Table 2

Cl and C2 products have the same mechanical properties.

Example 2

III, 4 Preparation of masterbatch of natural rubber and carbon black

The coagulum of natural rubber (100 phr) and carbon black (50 phr) having a very good note of dispersion of the filler in the elastomeric matrix are produced in the liquid phase according to the process described in patent L.S. Patent No. 6,048,923.

They are then dried according to the following processes:

M3 masterbatch (not according to the invention):

At the exit of the wringer, pellets at a flow rate of 100 kg / h dry product and loaded with 15% volatile matter (mainly water) are sent to the FCM. 6-PPD is injected at the inlet of the FCM at a rate of 1.2 phr.

At the outlet of the FCM, the mixture called chunk leaves at 160 ° C. and a volatile matter content of between 1 and 3%. The Mooney viscosity measured for this composite (MS) is between 95 and 115.

At the exit of the FCM, the entire production (100 kg / h) is sent to the cylinder tool (Roll Mill).

On leaving the Roll Mill tool, the composite has a temperature around 155 ° C, a Mooney viscosity of 85-95 on average and a volatile matter content <1%, generally around 0.4 %. This composite RM output, called strip, is then sent towards the end of the line.

Masterbatch M4 (according to the invention):

At the exit of the wringer, pellets at a flow rate of 100 kg / h dry product and loaded with 15% volatile matter (mainly water) are sent to the FCM. With this recipe, there is no injection of 6-PPD into the FCM.

At the outlet of the FCM, the mixture called chunk leaves at 165 ° C. and a volatile matter content of between 1 and 3%. The Mooney viscosity measured for this composite (MS) is between 95 and 115.

At the exit of the FCM, the entire production (100 kg / h) is sent to the cylinder tool (Roll Mill).

At the exit of the Roll Mill tool, the composite has a temperature around 155 ° C, a Mooney viscosity between 55 and 65 and a volatile matter content <1%, generally around 0.4%. This composite called strip is then sent to the prebreaker where it is mixed with 1 pce of 6-PPD. At the exit of prebreaker the composite is sent towards the end of the line.

III-5 Preparation of rubber compositions

The various compositions were produced from the masterbatch M3, and

M4.

The following tests are carried out as follows: the master mixture M3 or M4 is introduced into an internal mixer, filled to 70% and whose initial tank temperature is approximately 60 ° C. Thermomechanical work is then carried out (non-productive phase) in one step (total mixing time equal to approximately 5 min), until a maximum drop temperature of approximately 165 ° C is reached.

The mixture thus obtained is recovered, it is cooled and then the vulcanization system (sulfur and sulfenamide accelerator) is added on an external mixer at 70 ° C, mixing everything (productive phase) for about 5 to 6 min.

The 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.

III-6 Mechanical properties

The purpose of this example is to demonstrate that the properties of a rubber composition obtained with a masterbatch in accordance with the invention have the same mechanical properties as a masterbatch obtained by a conventional process.

Composition C3, not in accordance with the invention, is prepared from a masterbatch M3 according to the process detailed in paragraph III-5.

Composition C4 in accordance with the invention is prepared from a masterbatch M4 according to the process detailed in paragraph III-5.

All the compositions have the following basic formulation (in pce):

natural rubber 100 carbon black N234 50 6-PPD (1) 2 Stearic acid 2.5 ZnO (2) 2.7 Sulfur 1.7 CBS (3) 0.75

Table 3 (1) 6-PPD: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine: antioxidant (2) ZnO: Zinc Oxide (3) N-cyclohexyl-2-benzothiazyl-sulfenamide ( "Santocure CBS" of the company

Flexsys); accelerator

The properties measured after baking at 150 ° C for 40 minutes are given in Table 4 below.

C3 C4 MA300 / MA100 1.48 1.53 MFTR (kcycles) 162 183 G * (MPa) 1.32 1.27 Tan (ô) max 0.12 0.12

Table 4

Products C3 and C4 have the same mechanical properties.

By eliminating T injection of 6-PPD at FCM (Farrel Continuous Mixer) 15 upstream from the roll mill on:

• Lower the Mooney of the composite • Increase the flow

And this without degrading the properties of the composite in mixture.

Stopping the injection of 6-PPD into the FCM makes it possible to notably improve the cohesion of the composite on the roll mill, to quickly lower its Mooney and to increase the production rate (for the example of 72pce in black of carbon the increase in flow is 100%; it is more than 30% for the example of 50pce in carbon black).

Example 3

The purpose of this example is to demonstrate that the properties of a desired proportion of antioxidant are obtained from the present invention.

The proportion of final antioxidant desired is around 1%. The fraction of the total flux withdrawn would be around 20% which should be dosed with 5% of antioxidant.

The antioxidant dosage is to be carried out continuously through the feed hole of the extruder installed in bypass of the main flow and receiving 20% of the total flow.

The product leaving the bypass extruder is therefore dosed at 5% antioxidant. It is reinjected into the total flow to produce a product dosed with 1% antioxidant.

Claims (16)

1. Process for the preparation of a masterbatch, comprising a diene elastomer, a reinforcing filler and an antioxidant agent, and having a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 80, the diene elastomer comprises at least natural rubber, the method comprising the following successive steps: a) Introducing, in order to obtain a dried mass, a coagulum into at least one heated continuous mixer, said coagulum comprises said diene elastomer and said reinforcing filler dispersed with a Z score greater than or equal to 80 in the dried mass; b) Pass the mass leaving the continuous mixer through a cylinder tool to obtain a ribbon; then c) Divide the masterbatch into two parts including a first part of the flow leaving the cylinder tool and a second part of the flow leaving the cylinder tool; d) Introduce the antioxidant agent to the first part of the masterbatch; e) Combine the first part and the second part of the masterbatch; and f) introducing the combined parts into a continuous mixer so as to obtain a masterbatch comprising an antioxidant agent; in which all of the antioxidant agent present in the masterbatch obtained at the end of step f) is introduced during step d). 2. Method according to claim 1, in which the two parts of the divided masterbatch comprise the first part with 20% of the flow rate at the outlet of the cylinder tool and the second part with 80% of the flow rate at the outlet of the tool cylinder 3. Method according to claim 1 or claim 2, further comprising the step of recovering following step b) said masterbatch having a moisture content of less than 1% by weight. 4. Method according to any one of claims 1 to 3, in which the entire mass leaving the continuous mixer of step a) is sent to the cylinder tool of step b) · 5. Method according to any one of claims 1 to 4, wherein the masterbatch has a dispersion of the reinforcing filler in the elastomeric matrix having a Z score greater than or equal to 90. 6. Method according to any one of claims 1 to 5, wherein prior to step a) the coagulum is obtained by mixing in the liquid phase from a latex of the diene elastomer and an aqueous dispersion of the reinforcing filler. 7. Method according to claim 6, characterized in that the coagulum is obtained according to the following steps: - Supply a continuous flow of the latex of the diene elastomer to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, - Supply a continuous flow of a fluid comprising a reinforcing organic charge under pressure in the mixing zone of a coagulation reactor to form a coagulated mixture, - Wring out the coagulum obtained previously in order to recover the wrung out coagulum from step a). 8. Method according to any one of claims 1 to 7, wherein at the outlet of the continuous mixer of step a) the mass has a volatile matter content of less than 5% by weight. 9. Method according to any one of claims 1 to 8, wherein at the output of step b) the ribbon has a volatile content of less than 1% by weight. 10. Method according to any one of claims 1 to 9, wherein the reinforcing filler is a carbon black. 11. The method of claim 10, wherein the carbon black content is between 40 and 90 phr, preferably between 45 and 80 phr. 12. Method according to any one of claims 1 to 11, wherein the diene elastomer is a natural rubber. 5 13. Method according to any one of claims 1 to 12, in which the antioxidant agent is an N-alkyl-N’-phenyl-paraphenyldiamine corresponding to formula (I): Wherein R ¹ represents a linear or branched alkyl group having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms. 14. A method of preparing a rubber composition comprising the following steps: 15 (A) Preparation of a masterbatch comprising a diene elastomer, a reinforcing filler and an antioxidant agent by the method according to any one of claims 1 to 13; (B) Thermo-mechanical mixing at high temperature of the masterbatch obtained following step (A) with the other constituents of the rubber composition, 20 with the exception of the vulcanization system; (C) mechanical work at a temperature below the temperature of step (B) of the product resulting from step (B) and incorporation of the vulcanization system.