Composition of curable rubber, suitable to produce a tire and tire containing this composition

ES 2 238 352 T3

DESCRIPTION

Vulcanizable rubber composition usable to make a tire, and a tire comprising this composition.

The present invention relates to a vulcanizable rubber composition that is primarily intended for the manufacture of tire tires, and a tire whose tread comprises said composition, which exhibits improved hysteresis and physical properties in the vulcanized state, preserving at the same time satisfactory wear properties in the unvulcanized state.

Since fuel economy and the need to conserve the environment have become a priority, it is desirable to produce mixtures having good mechanical properties and as low a hysteresis as possible in order to be able to use them in the form of rubber compositions. usable for the manufacture of various semi-finished products that enter into the composition of tires, such as for example, underlayers, sidewalls, treads, and to obtain tires having low rolling resistance.

To achieve this objective, numerous solutions have been proposed which consist mainly in modifying the structure of the diene polymers and copolymers at the end of the polymerization by means of functionalizing, coupling or forming agents of a star-shaped structure. Most of these solutions have concentrated on the use of functionalized polymers that are active against carbon black, in order to obtain a good interaction between the polymer thus modified and carbon black.

As an illustration of this prior art regarding reinforcing fillers constituted by carbon black, mention may be made, for example, of US patent 3,135,716, which describes the reaction of living diene polymers at the end of the chain with a polyfunctional organic coupling agent to obtain polymers with improved properties. Likewise, US patent 3 can be cited. 244,664, which discloses the use of tetraalkoxysilanes as a coupling or star-forming agent of diene polymers.

The use of silica as a reinforcing filler in vulcanizable rubber compositions, mainly intended to enter the constitution of tire treads, is ancient. However, this use has been very limited, due to the unsatisfactory level of certain physical properties of such compositions, mainly resistance to abrasion.

This is the reason why it has been proposed to use, to alleviate these drawbacks, functionalized diene polymers instead of non-functionalized polymers that were previously used, and in particular polymers functionalized by derivatives of alkoxysilanes, such as tetraethoxysilanes. Mention may be made, for example, of US Pat. 5,066,721, which describes a rubber composition comprising an alkoxysilane functionalized diene polymer having at least one non-hydrolyzable alkoxy moiety, allowing removal of polymerization solvent by steam stripping.

A drawback of these functionalization reactions resides in the coupling reactions that accompany them, which generally requires the use of an excess of alkoxysilane and / or intense kneading, to minimize these coupling reactions.

Another drawback of these reactions resides in the subsequent use of the steam stripping operation, which is necessary to remove the polymerization solvent.

Indeed, in a general way, experience shows that the functionalized polymers obtained undergo macrostructure evolutions during this dragging operation, which leads to a severe degradation of their properties, unless limited to using an alkoxysilane as functionalizing agent it belongs to a restricted family, such as that described in the aforementioned US Patent 5,066,721.

Accordingly, it appears from the foregoing that the use of diene polymers comprising an alkoxysilane function to obtain rubber compositions comprising silica as a reinforcing filler is not satisfactory, despite the improved physical properties of these compositions.

This is the reason why investigations have been carried out on other functionalization reactions, always with a view to obtaining such rubber compositions.

As an example, French patent 2,740,778 in the name of the applicant may be cited, which discloses the use of diene polymers that carry a silanol function at the end of the chain or a polysiloxane block having a silanol end. For example, a functionalizing agent consisting of a cyclic polysiloxane, such as hexamethylcyclotrisiloxane, is used. The functionalized polymers obtained can be separated from the reaction medium, which leads to their formation, by extraction of the solvent with steam, without changing their macrostructure and, consequently, their physical properties.

These functionalized polymers are intended to be incorporated into vulcanized compositions that comprise, as reinforcing filler, silica in a majority quantity, comprising, for example, a mixture of silica

ES 2 238 352 T3 and carbon black. It has been established that these polymers confer properties similar to those of rubber, mainly hysteresis and reinforcement in the vulcanized state, which are improved with respect to those of control compositions based on non-functionalized diene polymers, and which are at least analogous to those of of compositions based on diene polymers comprising an alkoxysilane function.

However, it has been found that this improvement in the vulcanized state of the hysteresis and reinforcing properties is accompanied, in the unvulcanized state, by an increase in the Mooney viscosity of the compositions tested relative to said control compositions, that is to say, a reduced aptitude for use.

The object of the present invention is to remedy this factual state, and it has been achieved because the applicant firm has just surprisingly discovered that a rubber composition comprising a reinforcing white filler and comprising at least one diene block copolymer, which is intended to interact with said reinforcing white charge, and comprising at least one of its chain ends a polyether block whose molecular weight is substantially between 1000 g / mol and 3000 g / mol, said polyether block responding to the following formula:

O - (CH₂ - CH₂ - O)_n - R (i) where n is a non-zero natural integer and R is a saturated or unsaturated hydrocarbon group, leads to hysteresis properties in small and large deformations that are comparable to those achieved with previously functionalized diene polymers mentioned, while leading to properties for use in the unvulcanized state which are particularly advantageous, since they are close to those obtained with a composition based on a non-functionalized diene polymer.

This diene block copolymer can be obtained in various ways. It can be obtained by sequenced polymerization or by grafting reaction. In the latter case, the diene block copolymer is obtained by reacting a first reactant, consisting of a diene polymer comprising a halogensilane group at the end of the chain, with a second reactant, consisting of a polyether comprising at least one hydroxy radical at the end of the chain.

This reaction is carried out in the presence of a tertiary amine, for example dimethylaminopyridine, and can be carried out in dispersion or in solution. Furthermore, it can be carried out continuously or discontinuously.

The first diene block that is obtained can be, for example, statistical, sequenced or microsequenced.

On the other hand, this first diene block can have any appropriate microstructure, which is a function of the particular conditions for carrying out this reaction, such as the presence or not of a modifying and / or randomizing agent and the amounts of modifying agent and / or randomizing employed.

* By first diene block, we mean any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds. having 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinyl aromatic units.

The most suitable conjugated dienes are 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (Ci to C₅) 1,3-butadiene, 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, phenyl-1,3-butadiene, 1,3-pentadiene and 2,4-hexadiene.

Suitable vinyl aromatic compounds are mainly styrene, ortho-, para-, or meta-methylstyrene, the commercial mixture "vinyl toluene", para-tert-butylstyrene, methoxystyrenes, vinylmesitylene, divinylbenzene and vinylnaphthalene.

Preferably for this first diene block, the following are appropriate:

- polybutadienes, in particular those with a mass content in 1,2 units ranging from 4% to 80%,

- polyisoprenes whose percentage of vinyl units is less than 80%,

- butadiene-styrene copolymers, in particular those which have, on the one hand, a styrene mass content ranging from 4% to 50% and more particularly from 20% to 40% and, on the other hand, mass content of bonds 1 , 2 and trans-1,4 ranging respectively from 4% to 65% and from 30% to 80%,

- butadiene-isoprene copolymers, mainly those with an isoprene mass content ranging from 5% to 90% and a glass transition temperature (Tg) ranging from -80 ° C to -20 ° C,

ES 2 238 352 T3

- isoprene-styrene copolymers, mainly those with a styrene mass content ranging from 5% to 50% and a percentage of vinyl units that is less than 90%,

- Butadiene-styrene-isoprene terpolymers, mainly those with a styrene mass content ranging from 5% to 50% and more particularly ranging from 10% to 40%, a mass isoprene content ranging from 15% to 60% % and more particularly ranging from 20% to 50%, a mass content of butadiene ranging from 5% to 50% and more particularly ranging from 20% to 40%, a mass content in 1,2 units of the butadiene part ranging from 4% to 85%, a mass content in trans 1,4 units of the butadiene part ranging from 6% to 80%, a mass content in 1,2 and 3,4 units of the isoprenic part ranging from 5% to 70%, and a mass in 1,4 trans units of the isoprene part ranging from 10% to 50%.

The diene polymer constituting said first reagent can be obtained by reacting a living diene polymer with a dihalogen-dialkyl-silane. According to a preferred embodiment of the invention, this first reactant is obtained, initially, by reacting a living diene polymer with a cyclic organosiloxane (as described in French patent 2,740,778) to obtain a polymer having one end of lithium silanolate, and then, in a second stage, by reacting this last polymer with a dialkyl-dihalogene-silane.

It will be noted that this procedure for obtaining said first reactant has the advantage of reducing the percentage of coupled polymer.

The living diene polymer used for the first time mentioned is obtained anionically by means of a monofunctional or difunctional organometallic initiator, depending on whether it is desired to obtain, for the block copolymer of the invention, a polyether block alone or in each of the two ends of the chain respectively. This initiator is, for example, constituted by an alkyl lithium, preferably n-butyllithium, or a lithium amide.

* As a second reagent, said polyether is such that one of its chain ends is provided with a hydroxy group, its other chain end is provided with an alkyl group or an aryl group, in order to obtain for said block copolymer a polyether block that responds to said formula (i).

Preferably, the chain end of said polyether other than that provided with a hydroxy group is provided with an alkyl group.

A rubber composition according to the invention is obtained by kneading by means of thermo-mechanical working of the block copolymer obtained, on the one hand, with a reinforcing white filler present in the majority of the reinforcing filler used and, on the other, with additives suitable for obtaining a vulcanizable rubber composition.

According to variant embodiments to obtain this composition according to the invention, said block copolymer is used mixed with one or more other elastomers conventionally used in tire tires, such as natural rubber or a mixture based on natural rubber and an elastomer. synthetic, or even another diene elastomer optionally coupled and / or starred, or even partially or entirely functionalized by a block other than a polyether block that responds to said formula (i).

It will be noted that the improvement in the properties of the rubber composition according to the invention will be the higher, the lower the proportion of said conventional elastomers in the composition according to the invention. Advantageously, this or these conventional elastomers may, if necessary, be present in the composition according to the invention in an amount ranging from 1 to 70 parts by weight per 100 parts by weight of elastomeric copolymer comprising at least one polyether block according to the invention.

In the present patent application, "white reinforcing filler" is understood as a "white" filler (that is, inorganic, in particular mineral), sometimes also called a "clear" filler, capable of reinforcing by itself, without any other means. that an intermediate coupling system, a rubber composition intended for the manufacture of tires; in other words, capable of replacing a conventional filler of quality tire carbon black in its reinforcing function.

Preferably, the reinforcing white filler is wholly or at least mostly silica (SiO₂). The silica used can be any reinforcing silica known to the person skilled in the art, mainly any precipitated or fumed silica that has a BET surface, as well as a CTAB specific surface, both less than 450 μm.²/ g, even if highly dispersible precipitated silicas are preferred.

In the present disclosure, the BET specific surface is determined in a known manner, according to the Brunauer-Emmet-Teller method described in The Journal of the American Chemical Society ”Vol. 60, page 309, February 1938 and corresponding to the AFNOR- standard. NFT-45007 (November 1987); the CTAB specific surface is the external surface determined according to the same AFNOR-NFT-45007 standard of November 1987.

By highly dispersible silica, it is understood any silica which has a very important ability to deagglomerate and for dispersion in an elastomeric matrix, observable in a manner known by electron or optical microscopy, in thin sections. As non-limiting examples of such preferred highly dispersible silicas, one can

ES 2 238 352 T3 mention Perkasil KS 430 silica from Akzo, BV 3180 silica from Degussa, Zeosil 1165 MP and 1115 MP silicas from Rhodia, Hi-Sil 2000 silica from PPG, Zeopol 8741 or 8745 silicas from the Huber company, treated precipitated silicas, such as, for example, the aluminum "doped" silicas described in European patent application 0735088.

The physical state in which the reinforcing white filler is present is indifferent, be it in the form of powder, microbeads, granules, or even balls. Naturally, reinforcing white fillers should also be understood as mixtures of different reinforcing white fillers, in particular highly dispersible silicas, such as those described above.

According to a preferred embodiment of the invention, the reinforcing filler of the rubber composition comprises a reinforcing white filler in a majority quantity (that is, with a mass fraction of reinforcing white filler in said reinforcing filler that is greater than 50%).

The reinforcing filler of a rubber composition according to the invention may thus contain, as a mixture, in addition to the aforementioned reinforcing filler or fillers, carbon black in a minor amount (that is, according to a mass fraction that is less than 50%). . As carbon blacks, all carbon blacks are suitable, mainly blacks of the type HAF, ISAF, SAF, conventionally used in tires and particularly in tire treads. As non-limiting examples of such blacks, mention may be made of blacks N115, N134, N234, N339, N347, N375.

For example, black / silica mixtures or blacks partially or fully coated with silica are suitable for constituting the reinforcing filler. Silica-modified carbon blacks are also suitable, such as, without limitation, the fillers that are marketed by the company CABOT under the name << CRX 2000 >>, and that are described in international patent WO-A-96/37547 .

In the case in which the reinforcing filler contains only one reinforcing white filler and carbon black, the mass fraction of this carbon black in said reinforcing filler is preferably chosen less than or equal to 30%.

However, experience shows that the aforementioned properties of the composition according to the invention are all the more improved, when the reinforcing filler it comprises contains a higher mass fraction of reinforcing white filler, and that said properties are optimal when said composition contains only a reinforcing white filler, for example silica, as a reinforcing filler. The latter case constitutes a preferred example of a rubber composition according to the invention.

The rubber composition according to the invention also conventionally comprises a reinforcing white filler / elastomeric matrix bonding agent (also called coupling agent), whose function is to ensure sufficient bonding (or coupling), of a chemical nature and / or physical, between said white charge and the matrix, thus facilitating the dispersion of this white charge within said matrix.

Said binding agent, at least bifunctional, has, for example, the simplified general formula "YTX", in which:

- Y represents a functional group ("Y" function) that is able to physically and / or chemically bind to the white charge, said union being able to be established, for example, between a silicon atom of the coupling agent and the hydroxyl groups (OH ) from the surface of the filler (for example surface silanols when it comes to silica),

- X represents a functional group ("X" function) that is capable of being physically and / or chemically bound to the elastomer, for example via a sulfur atom;

- T represents a hydrocarbon group that allows Y and X to be joined.

These bonding agents should not in particular be confused with simple coating agents for the filler in question, which, in a known manner, may have the active Y function vis-à-vis the filler, but are devoid of the X function active vis-à-vis the elastomer.

Such binding agents, of varying efficacy, have been described in a large number of documents and are well known to those of skill in the art. In fact, any bonding agent known for, or capable of, effectively ensuring, in the diene rubber compositions usable for the manufacture of tires, the bond between the silica and the diene elastomer can be used, such as, for example, organosilanes, mainly polysulfurized alkoxysilanes or mercaptosilanes, or polyorganosiloxanes carrying the aforementioned X and Y functions.

In particular, polysulfurized alkoxysilanes are used, such as those described for example in US patents 3,842,111, US 3,873,489, US 3,978,103, US 3,997,581, US Pat. US 4,002,594 or more recently US 5,580,919, US 5,583,245, US 5,663,396, US 5,684,171, US 5,684,172, US 5 696,197, which describe such known compounds in detail.

They are particularly suitable for the composition of the invention, without the following definition being limiting, alkoxy5

ES 2 238 352 T3 so-called "symmetric" polysulfurized silanes that respond to the following general formula (I):

(I) Z - A - S_n - A - Z, in which:

- n is an integer from 2 to 8;

- A is a divalent hydrocarbon radical;

- Z responds to one of the following formulas:

R¹ R¹

II —Yes —R¹ ; —Yes —R²

R² —Yes - R²,

R²

R²_Rtwo in which:

- radicals R¹, substituted or unsubstituted, identical or different from each other, represent an alkyl group of C₁C₁₈, C cycloalkyl₅-C₁₈ or C aryl₆-C₁₈;

- radicals R², substituted or unsubstituted, identical or different from each other, represent an alkoxy group of C₁C₁₈ or C cycloalkoxy₅-C₁₈.

In formula (I) above, the number n is preferably an integer from 3 to 5.

In the case of a mixture of polysulfurized alkoxysilanes responding to formula (I) above, mainly the usual commercially available mixtures, the average value of "n" is a fractional number, preferably between 3 and 5, more preferably close to Four.

The radical A, substituted or unsubstituted, is preferably a divalent hydrocarbon radical, saturated or unsaturated, comprising from 1 to 18 carbon atoms. They are mainly suitable for alkylene groups of C₁ -C₁₈ or arylene groups of C₆-C₁₂, more particularly C alkylenes₁-C₁₀, mainly from C₂-C₄, in particular propylene.

Radicals R¹ are preferably C₁-C₆, cyclohexyl or phenyl, mainly C alkyl groups₁-C₄, more particularly methyl and / or ethyl.

Radicals R² are preferably C alkoxy groups₁ -C₈ or C cycloalkoxy₅-C₈, more particularly methoxy and / or ethoxy.

Said so-called "symmetric" polysulfur alkoxysilanes, as well as some of their production processes are described, for example, in recent US patents 5,684,171 and US 5,684,172 which give a detailed list of these known compounds, for n varying from 2 to 8.

Preferably, the polysulfurized alkoxysilane used in the invention is a polysulfide, in particular a tetrasulfide, debis (C₁-C₄) silylpropyl), more preferably debis (trialkoxyl (C₁-C₄) silylpropyl), mainly bis (3-triethoxysilylpropyl) or bis (3-trimethoxysilylpropyl).

As a particularly preferred example, bis (triethoxysilylpropyl) tetrasulfide or TESPT, of formula [(C₂H₅OR)₃Yes (CH₂)₃S₂]₂, marketed for example by the company Degussa under the name Si69 (or X50S when it is supported at 50% by weight on carbon black), or even by the company Witco under the name Silquest A1289 (in both cases a commercial mixture of polysulfides with a mean value for n that is close to 4).

Those skilled in the art will know how to adjust the content of coupling agent in the compositions of the invention depending on the application considered, the elastomeric matrix used and the amount of reinforcing white filler used.

In the rubber compositions according to the invention, the coupling agent content may be in a range from 0.5 to 15% with respect to the reinforcing white filler mass.

It should be well understood that the coupling agent could be previously grafted (by means of the "X" function) on the diene elastomer of the composition of the invention, the elastomer thus functionalized or "pre-coupled" comprising the free "Y" function. for the reinforcing white charge. Likewise, it could be previously grafted (by means of the "Y" function) on the reinforcing white filler, the filler thus "pre-coupled" being then able to be attached to the diene elastomer by means of the free function "X".

However, it is preferred, mainly for reasons of better use of the compositions in the non-state

ES 2 238 352 T3 vulcanized, use the coupling agent, either grafted onto the reinforcing white filler, or in a free state (that is, not grafted).

As for the aforementioned additives that are used in this composition, they can mainly comprise plasticizers, pigments, anti-oxidants, antiozonant waxes, a vulcanization system based on sulfur and / or peroxide and / or bismaleimides, vulcanization accelerators, diluting oils, one or more silica coating agents, such as alkoxysilanes, polyols or amines.

Another subject of the invention is a tire tread, which is such that it comprises a rubber composition, such as the one mentioned above.

Due to the reduced hysteresis that characterizes a rubber composition according to the invention in the vulcanized state, it will be noted that a tire whose tread comprises said composition exhibits an advantageously low rolling resistance.

The aforementioned characteristics of the present invention, as well as others, will be better understood from reading the following description of various embodiments of the invention, given as illustrative and not limiting.

In the examples that follow, the viscosities are inherent viscosities that were measured in toluene, at a concentration of 1 g / l.

I. Example of preparation of a two-block copolymer of styrene-butadiene, on the one hand, and polyether of molecular weight equal to 2000 g / mol, on the other hand

In a 10 liter reactor containing 5.8 liters of toluene, 231 grams of styrene and 410 grams of butadiene were injected, as well as 2000 ppm of tetrahydrofuran (parts per million THF). After having neutralized the impurities in the solution to be polymerized by adding n-BuLi, 0.0032 mol of active n-BuLi were added. The polymerization was carried out at 40 ° C.

When the conversion percentage of the monomers reached 75% (percentage reached after 30 minutes, with an inherent viscosity of the reaction medium then equal to 1.40 dl / g), 0.012 mol of hexamethylcyclotrisiloxane was injected into the reactor in solution in 10 cm³ of toluene previously deaerated. The solution thus obtained was stirred for 30 minutes and at 40 ° C. Then 0.030 mol of dichlorodimethylsilane was added, and then the polymer solution obtained was stirred again for 15 minutes at 40 ° C.

Then they were added, in solution in 50 cm³ of deaerated toluene, 90 grams of a polyether constituted by an anhydrous polyethylene glycol comprising, at one of its chain ends, a methyl group and, at its other chain end, a hydroxy group, as well as 0.005 mol of dimethylaminopyridine. This polymer solution was stirred for one hour and at 60 ° C.

This polyether, marketed by the company FLUKA, had previously been prepared by anionic polymerization of ethylene oxide, and responded to the above-mentioned formula (I), R being a methyl group.

The polymerization was stopped and the obtained copolymer was treated by means of an antioxidant, respectively by adding 0.2 part percent elastomer (pce) of 2,2'-methylene-bis (4-methyl-6-tert-butylphenol). ) and 0.2 pce of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylene diamine.

The block copolymer obtained was then recovered by a conventional steam stripping operation of the solvent, then dried on an instrument at 100 ° C for 10 minutes.

The inherent viscosity of the block copolymer (in toluene) after steam stripping was 1.50 dl / g and the Money ML viscosity (1 + 4.100 ° C) was 30.

Near infrared analysis of the block copolymer showed that the block (SBR) contained 26% by weight of styrene. The butadiene fraction contained as such 41% vinyl linkages.

An analysis by the size exclusion chromatography (SEC) technique showed that there was no free polyether.

The number average molecular weight (Mn) of the block copolymer, determined by osmometry, was 175,000 g / mol.

NMR analysis ¹H of the block copolymer was carried out on a sample that had been subjected to three series of treatments, each consisting of a coagulation in methanol followed by a new solution in toluene. For this NMR analysis¹H a device marketed under the name "BRUKER AC200" was used,

The number of residues [-OCH₂CH₂-] per 100 styrene-butadiene residues, a number that was equal to 1.2, for a chemical shift of 3.42 ppm. Given

ES 2 238 352 T3 said number average molecular weight (Mn) and that of the polyether block (2000 g / mol), which was measured by said SEC technique, it turned out that the percentage of copolymer that comprised a polyether block was approximately 75%.

II. Comparative examples of rubber compositions according to the invention

In the examples that follow, the properties of the compositions of the invention were evaluated as follows:

- Mooney ML viscosity (1 + 4) at 100 ° C: measured according to ASTM: D-1646, titled "Mooney" in the tables.

- Modulus of elongation at 300% (MA 300), at 100% (MA 100) and at 10% (MA. 10): the measurements were made according to the ISO 37 standard.

- Hysteresis losses (PH): measured by rebound at 60 ° C in%. The strain for the measured losses was 40%.

- SHORE A hardness: measurements were made according to DIN 53505.

- Dynamic properties in shear: measured as a function of the deformation, carried out at 10 Hertz with a crest-crest deformation of 0.15% to 50%. The non-linearity expressed is the difference in shear modulus between 0.15% and 50% strain in MPa. Hysteresis is expressed by the measurement of the tangent (tg) delta at 7% strain and at 23 ° C according to ASTM D2231-71 (re-approved in 1977).

Example II.1

In this example, the contributions of three elastomers "SBR A, SBR B, SBR C" respectively in the interior of rubber compositions A, B and C, of ​​the tread type for a tire of a passenger car and with only silica as reinforcing filler. These three elastomers had the following characteristics:

-SBR A is a control SBR that was synthesized according to Example I according to the invention, with the exception of the stopping of the polymerization reaction that was carried out with the aid of methanol,

- SBR B is an SBR that has a dimethylsilanol function, which was obtained by adding hexamethylcyclotrisiloxane when the monomer conversion percentage reached 70% (reference can be made to French patent 2,740,778 for a description of this functionalization, and

- SBR C is a functionalized SBR according to the invention, the synthesis of which was described in example 1.

The formulation used for each of these three compositions A, B and C is as follows, in parts by weight per hundred parts of elastomer (pce):

Elastomer Silica (1)

Aromatic oil (2) Binding agent (3) ZnO

Stearic Acid Anti-oxidant (4)

Anti-ozonating wax (5) Sulfur

Sulfenamide (6) Diphenylguanidine

100 pce pce pce

6.4 pce

2.5 pce

1.5 pce

1.9 pce

1.5 pce

1.1 pce pce

1.5 pce with (1) = Rhone-Poulenc ZEOSIL 1165 silica, (2) = oil sold under the name Enerflex 65, (3) = "Si69 Degussa" binding agent, (4) = N- (1, 3-dimethyl-butyl) n-N'-phenyl-p-phenylenediamine (5) = wax "C32ST", (6) = N-cyclohexyl-2-benzothiazyl sulfenamide.

Each composition A, B, C was prepared according to the method described in the European patent EP-A-501227, specifying that a thermo-mechanical work was carried out in two stages that lasted respectively 5 minutes and 4 minutes, for an average speed of the 45 rpm paddles, until an identical maximum dropping temperature of 160 ° C was reached,

ES 2 238 352 T3 while the step of incorporating the vulcanizing system was carried out on "the homoterminador" at 30 ° C. Vulcanization was carried out at 150 ° C for 40 minutes.

The results are collected in Table 1.

TABLE 1

<td>COMPOSITION</td><td>TO</td><td>B</td><td>C</td>

<td>SBR elastomer properties ML (1 + 4) at 100 ° C</td><td> 30</td><td> 30</td><td> 29</td>

<td>Properties in unvulcanized state ML (1 + 4) at 100 ° C</td><td> 53</td><td> 85</td><td> 74</td>

<td>Properties in vulcanized state</td><td></td><td></td><td></td>

<td>Shore hardness</td><td> 65,6</td><td> 58,4</td><td> 59,4</td>

<td>MA 10</td><td> 5,52</td><td> 3,66</td><td> 3,76</td>

<td>MA 100</td><td> 1,74</td><td> 1,62</td><td> 1,87</td>

<td>MA 300</td><td> 1,99</td><td> 2,34</td><td> 2,64</td>

<td>MA300 / MA 100</td><td> 1,14</td><td> 1,44</td><td> 1,41</td>

<td>PH losses (60 ° C, def. 35%)</td><td> 33,0</td><td> 21,3</td><td> 19,2</td>

<td>Dynamic properties as a function of deformation</td><td></td><td></td><td></td>

<td>Delta G * 23 ° C</td><td> 4,03</td><td> 1,16</td><td> 1,13</td>

<td>tg_max 23 ° C</td><td> 0,352</td><td> 0,229</td><td> 0,232</td>

From the above data it can be deduced that when mixed with silica and in relation to the properties of the vulcanized state, the SBR C according to the invention confers on the composition C reinforcing properties that are superior to those obtained with the control SBR A. The same happens for composition B comprising SBR B, compared to said SBR A.

Furthermore, it will be noted that the hysteresis properties with weak and strong deformations of the composition C according to the invention are, on the one hand, clearly improved with respect to those of the control composition A and, on the other hand, are close to those of the composition B.

In relation to the unvulcanized state, it will be noted that composition C of the invention has a Mooney viscosity that is lower than that of composition B. Consequently, composition C of the invention has a usability that is improved with compared to composition B with classic functionalized elastomer.

In other words, it was shown that the incorporation of a functionalized elastomer according to example I of the invention, such as SBR C, into a rubber composition makes it possible to obtain rubber properties for this composition that are clearly improved with respect to of a composition with non-functionalized elastomer, such as SBR A, while exhibiting an improved aptitude for use compared to a composition with classic functionalized elastomer, such as SBR B.

Example II.2

In this example, within rubber compositions D and E the respective contributions of two mixtures were studied, each one consisting of SBR A according to example II.1 and a polyether, such as that used in example I.

For each of the compositions D and E, the formulation used is the same as in example II.1, except that 100 pce of elastomer are replaced:

ES 2 238 352 T3

- for composition D, for 99 pce of said SBR A and 1 pce of said polyether, and

- for composition E, for 95 pce of said SBR A and 5 pce of said polyether.

For each composition D, E, the kneading method is that described in example II.1, except that said polyether is introduced into the internal mixer at the same time as said SBR A. The results obtained for these two compositions D and E are compared with those previously obtained for compositions A, B and C, in table 2 below.

TABLE 2

<td>COMPOSITION</td><td>TO</td><td>B</td><td>C</td><td>D</td><td>AND</td>

<td>Elastomer properties mere SBR ML (1 + 4) at 100 ° C</td><td> 30</td><td> 30</td><td> 29</td><td> 30</td><td> 30</td>

<td>Properties in state unvulcanized ML (1 + 4) at 100 ° C</td><td> 53</td><td> 85</td><td> 74</td><td> 53</td><td> 43</td>

<td>Properties in state vulcanized Shore hardness</td><td> 65,6</td><td> 58,4</td><td> 59,4</td><td> 62,0</td><td> 66,8</td>

<td>MA10</td><td> 5,52</td><td> 3,66</td><td> 3,76</td><td> 4,47</td><td> 5,70</td>

<td>MA 100</td><td> 1,74</td><td> 1,62</td><td> 1,87</td><td> 1,86</td><td> 2,15</td>

<td>MA 300</td><td> 1,99</td><td> 2,34</td><td> 2,64</td><td> 2,43</td><td> 2,57</td>

<td>MA300 / MA100</td><td> 1,14</td><td> 1,44</td><td> 1,41</td><td> 1,31</td><td> 1,20</td>

<td>PH losses (60 ° C, def. 35%)</td><td> 33,0</td><td> 21,3</td><td> 19,2</td><td> 26,9</td><td> 27,9</td>

<td>Dynamic properties depending on the deformation marion Delta G * 23 ° C</td><td> 4,03</td><td> 1,16</td><td> 1,13</td><td> 2,41</td><td> 4,40</td>

<td>tgm «23⁰C</td><td> 0,352</td><td> 0,229</td><td> 0,232</td><td> 0,294</td><td> 0,340</td>

It follows that when mixed with silica, in relation to the properties in the vulcanized state, the SBR C according to the invention confers on the corresponding composition C reinforcing properties that are superior to those conferred by the control SBR A on compositions A, D and E. The same is true for composition B comprising SBR B, compared to the same compositions A, D and E.

Furthermore, it will be noted that the hysteresis properties with weak and strong deformations of the composition C according to the invention are improved with respect to those of the control composition A and those of the compositions D and E. The same happens for the composition B, in comparison with the same compositions A, D and E.

It will be noted in particular that composition C according to the invention and composition B each have a low strain hysteresis which is significantly lower than those of compositions D and E.

On the other hand, it will be noted that the incorporation into a rubber composition C of a functionalized elastomer according to example I.1 of the invention, such as SBR C, makes it possible to obtain rubber properties for this composition C that are close to those obtained. by incorporation into composition B of the elastomer SBR B with dimethylsilanol function, but with an improved aptitude for use compared to said composition B.

As the results obtained with compositions D and E show, the direct addition of a polyether to a non-functionalized SBR, such as SBR A, does not allow this result to be obtained, regardless of the weight fraction used for this addition.

ES 2 238 352 T3

It will also be noted that composition D, which exhibits rubber properties, and consequently an aptitude for use similar to that of control composition A, differs from the latter,

- due to hysteresis losses lower than those of composition A, and

- for a MA 300 / MA 100 ratio higher than that of this composition A.