阅读说明：本技术 橡胶组合物 (Rubber composition ) 是由 J-C·阿劳约达席尔瓦 F·勒梅勒 A·特里格尔 于 2019-09-11 设计创作，主要内容包括：本发明涉及橡胶组合物,所述橡胶组合物包含至少50phr的乙烯和1,3-二烯的共聚物、炭黑和硫化体系,所述共聚物包含至少50摩尔％的乙烯单元,所述硫化体系包含硫和硫化促进剂,所述硫化促进剂为主促进剂和次促进剂的混合物,次促进剂的量和促进剂总量之间的重量比小于0.7。这种组合物在内聚力和固化性质之间表现出良好折衷。(The invention relates to a rubber composition comprising at least 50phr of a copolymer of ethylene and a1, 3-diene, the copolymer comprising at least 50 mol% of ethylene units, carbon black and a vulcanization system comprising sulfur and a vulcanization accelerator which is a mixture of a primary accelerator and a secondary accelerator, the weight ratio between the amount of secondary accelerator and the total amount of accelerators being less than 0.7. Such compositions show a good compromise between cohesion and curing properties.)

1. Rubber composition based at least on a highly saturated diene elastomer, carbon black and a vulcanization system comprising sulphur and a vulcanization accelerator,

-the highly saturated diene elastomer is a copolymer of ethylene and a1, 3-diene comprising at least 50 mol% of ethylene units based on monomer units of the copolymer,

-the content of highly saturated diene elastomer in the rubber composition is at least 50phr,

the vulcanization accelerator is a mixture of a primary accelerator and a secondary accelerator,

-the mass ratio between the amount of secondary accelerator and the total amount of accelerators, which is the sum of the amount by mass of primary accelerator and the amount by mass of secondary accelerator in the rubber composition, is less than 0.7,

the mass ratios are calculated from the quantities expressed in phr.

2. The rubber composition according to claim 1, wherein the primary accelerator is a sulfenamide, preferably N-cyclohexyl-2-benzothiazyl sulfenamide.

3. The rubber composition according to any one of claims 1 and 2, wherein the secondary accelerator is a thiuram disulfide, preferably tetrabenzylthiuram disulfide.

4. Rubber composition according to any one of claims 1 to 3, wherein the mass ratio between the amount of secondary accelerator and the total amount of accelerators is greater than 0.05, preferably between 0.05 and 0.7.

5. Rubber composition according to any one of claims 1 to 4, wherein the mass ratio between the amount of secondary accelerator and the total amount of accelerators is less than 0.5, preferably less than or equal to 0.3.

6. The rubber composition according to any one of claims 1 to 5, wherein the sulfur content is less than 1phr, preferably between 0.3phr and 1 phr.

7. Rubber composition according to any one of claims 1 to 6, wherein the sulphur content is less than 0.95phr, preferably between 0.3phr and 0.95 phr.

8. Rubber composition according to any one of claims 1 to 7, wherein the sulphur content is less than 0.8phr, preferably between 0.3phr and 0.8 phr.

9. The rubber composition according to any one of claims 1 to 8, wherein the mass ratio between the sulfur content and the total amount of accelerators is less than 1, said mass ratio being calculated from the contents and amounts expressed in phr.

10. Rubber composition according to any one of claims 1 to 9, wherein the mass ratio between the sulphur content and the total amount of accelerators, calculated from the contents and amounts expressed in phr, is less than or equal to 0.7, preferably less than 0.6.

11. The rubber composition according to any one of claims 1 to 10, wherein the 1, 3-diene is 1, 3-butadiene.

12. The rubber composition according to any one of claims 1 to 11, wherein the highly saturated diene elastomer comprises at least 65 mol% of ethylene units, preferably from 65 mol% to 90 mol% of ethylene units.

13. The rubber composition according to any one of claims 1 to 12, wherein the content of highly saturated diene elastomer in the rubber composition varies within a range of from 80phr to 100phr, preferably from 90phr to 100 phr.

14. The rubber composition according to any one of claims 1 to 13, wherein the carbon black content is between 25phr and 65 phr.

15. A tire comprising a rubber composition as defined in any one of claims 1 to 14, preferably in a tire tread.

Technical Field

The field of the invention is that of rubber compositions based on highly saturated diene elastomers intended for use in tires, in particular in the treads thereof.

Background

For the same elastomer, the level of stiffness of the rubber composition is defined by the degree of vulcanization of the elastomer, which depends on both the vulcanization kinetics and the residence time of the rubber composition in the vulcanizer. It is known that even if a rubber composition has been removed from a vulcanizer, it continues to cure. When the rubber composition is in the form of a block, continued curing outside the curing press is more pronounced. If the reinforcement of the rubber composition is insufficient upon exiting the curing press, the viscosity of the rubber composition is such that air bubbles form within the rubber composition as it continues to cure outside the curing press. The formation of air bubbles within the rubber composition represents a uniformity defect in the rubber composition and may result in a reduction in the durability of a tire comprising the rubber composition. Therefore, it is desirable that at the end of curing in the vulcanizer, the rubber composition attain sufficient rigidity to prevent the formation of bubbles.

A disadvantage of highly saturated diene elastomers comprising at least 50 mol% of ethylene units is that they vulcanize with slower kinetics than highly unsaturated diene elastomers comprising more than 50 mol% of diene units. Thus, longer residence times in the vulcanizer are required to vulcanize rubber compositions comprising highly saturated diene elastomers, in particular if it is desired to avoid the aforementioned blistering phenomenon. Thus, the lower reactivity of the highly saturated diene elastomer towards vulcanization is manifested by a longer vulcanizer occupation time and a longer production cycle of the rubber composition, with a consequent reduction in productivity at the tyre manufacturing site.

In addition, it is also important to provide a rubber composition having good cohesion. For example, during rolling, the tread is subjected to mechanical stresses and stress factors resulting from direct contact with the ground. As a result, crack initiation sites are created. During the propagation of a crack on the surface or inside the tread, the crack initiation site may cause the material constituting the tread to break. Such tread damage can shorten the useful life of the tire tread. As the mechanical stresses and stress factors to which the tyre is subjected are amplified by the weight to which the tyre is subjected, good cohesion is most particularly sought in the case of tyres mounted on vehicles carrying heavy loads.

There remains a need to provide rubber compositions having an improved compromise between the cohesion properties and the cure time of the vulcanization machine.

Disclosure of Invention

The applicant has found a rubber composition capable of satisfying such a need.

The first subject of the invention is therefore a rubber composition based at least on a highly saturated diene elastomer, carbon black and a vulcanization system comprising sulfur and a vulcanization accelerator,

-the highly saturated diene elastomer is a copolymer of ethylene and a1, 3-diene comprising at least 50 mol% of ethylene units based on monomer units of the copolymer,

-the content of highly saturated diene elastomer in the rubber composition is at least 50phr,

the vulcanization accelerator is a mixture of a primary accelerator and a secondary accelerator,

-the mass ratio between the amount of secondary accelerator and the total amount of accelerators, which is the sum of the amount by mass of primary accelerator and the amount by mass of secondary accelerator in the rubber composition, is less than 0.7,

-calculating the mass ratio from the amounts expressed in phr.

Another subject of the invention is a tire comprising a rubber composition according to the invention.

Detailed Description

I. Detailed description of the invention

Any numerical interval denoted by the expression "between a and b" means a numerical range greater than "a" and less than "b" (i.e. excluding the limits a and b), while any numerical interval denoted by the expression "from a to b" means a numerical range extending from "a" up to "b" (i.e. including the strict limits a and b). The abbreviation "phr" means parts by weight per hundred parts of elastomer (rubber) (the sum of elastomers if multiple elastomers are present).

In the present patent application, the mass ratio between the components of the rubber composition is calculated from the contents or amounts of the components expressed in phr.

In the present description, the expression "composition based on" is understood to mean that the composition comprises a mixture and/or an in situ reaction product of the various components used, some of these essential components (for example elastomers, fillers or components of vulcanization systems or other additives conventionally used in rubber compositions intended for the manufacture of tyres) being susceptible to (or intended for) at least partially co-reacting during the various stages of manufacture of the composition intended for the manufacture of tyres.

In the present patent application, the expression "all the monomeric units of the elastomer" or "the total amount of monomeric units of the elastomer" means repeating units of all the constituents of the elastomer resulting from the insertion of the monomer into the elastomer chain by polymerization. Unless otherwise stated, the content of monomeric or recurring units in a highly saturated diene elastomer is given in mole percentages calculated on the basis of all the monomeric units of the elastomer.

The compounds mentioned in the description may be of fossil or bio-based origin. Where the compound is of bio-based origin, it may be partially or fully derived from biomass or may be obtained from renewable starting materials derived from biomass. In particular, elastomers, plasticizers, fillers, and the like.

The elastomers which can be used for the purposes of the present invention are highly saturated diene elastomers comprising ethylene units deriving from the polymerization of ethylene, said highly saturated diene elastomers being preferably random elastomers. In a known manner, the term "ethylene unit" denotes a- (CH) resulting from the insertion of ethylene into the elastomer chain₂-CH₂) -a unit. Due to ethylene unit accountAt least 50 mole% of all monomer units of the elastomer, and therefore the highly saturated diene elastomer is rich in ethylene units.

Preferably, the highly saturated diene elastomer comprises at least 65 mol% of ethylene units. In other words, the ethylene units preferably represent at least 65 mol% of all the monomer units of the highly saturated diene elastomer. More preferably, the highly saturated diene elastomer comprises from 65 to 90 mol% of ethylene units, the mol percentages being calculated on the basis of all the monomer units of the highly saturated diene elastomer.

Since the highly saturated diene elastomer is a copolymer of ethylene and a1, 3-diene, it also comprises 1, 3-diene units resulting from the polymerization of the 1, 3-diene. In a known manner, the term "1, 3-diene unit" denotes a unit obtained by insertion of a1, 3-diene by 1,4-, 1, 2-or 3, 4-addition (in the case of isoprene). The 1, 3-diene unit is, for example, a1, 3-diene containing from 4 to 12 carbon atoms, for example, 1, 3-butadiene, isoprene, 1, 3-pentadiene or aryl-1, 3-butadiene. Preferably, the 1, 3-diene is 1, 3-butadiene, in which case the highly saturated diene elastomer is a copolymer of ethylene and 1, 3-butadiene, said copolymer preferably being a random copolymer.

The highly saturated diene elastomers which can be used for the purposes of the present invention can be obtained according to various synthesis methods known to the person skilled in the art, in particular according to the target microstructure of the highly saturated diene elastomer. In general, it can be prepared by copolymerization of at least one 1, 3-diene (preferably 1, 3-butadiene) and ethylene according to known synthetic methods, in particular in the presence of a catalytic system comprising a metallocene complex. In this connection, mention may be made of the catalytic systems based on metallocene complexes described in EP 1092731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant. Highly saturated diene elastomers (including when they are random elastomers) can also be prepared by a process using a catalytic system of the preformed type (such as the catalytic systems described in WO 2017093654 a1, WO 2018020122 a1 and WO 2018020123 a 1).

The highly saturated diene elastomer in the rubber composition as defined in any of claims 1 to 14 preferably comprises units of formula (I) or units of formula (II).

-CH₂-CH(CH＝CH₂)-(II)

The presence of saturated six-membered ring units of formula (I) (1, 2-cyclohexanediyl) in the copolymer may result from a series of very specific insertions in the polymer chain during the growth of the polymer chain of ethylene and 1, 3-butadiene. When the highly saturated diene elastomer comprises units of formula (I) or units of formula (II), the molar percentages of units of formula (I) and units of formula (II) (o and p, respectively) in the highly saturated diene elastomer preferably satisfy the following equation (equation 1), more preferably equation (equation 2), calculated on the basis of all the monomer units of the highly saturated diene elastomer.

0< o + p.ltoreq.25 (equation 1)

0< o + p <20 (Eq. 2)

The highly saturated diene elastomers which can be used for the purposes of the present invention may consist of a mixture of highly saturated diene elastomers differing from one another in microstructure or macrostructure.

According to the invention, the highly saturated diene elastomer is present in the rubber composition in an amount of at least 50 parts by weight per hundred parts of elastomer (rubber) of the rubber composition (phr). Preferably, the content of highly saturated diene elastomer in the rubber composition varies within the range from 80phr to 100 phr. More preferably, it varies within the range of from 90phr to 100 phr.

The vulcanization system which can be used for the purposes of the present invention is essentially characterized in that it comprises sulfur and a vulcanization accelerator. By definition, the sulfur content and the vulcanization accelerator content of the vulcanization system are both strictly greater than 0 phr. Advantageously, the sulfur content in the rubber composition defined in any one of claims 1 to 15 is greater than 0.3 phr. Advantageously, the amount of vulcanization accelerator (i.e. the sum of the amount of primary accelerator and the amount of secondary accelerator) in the rubber composition defined in any one of claims 1 to 15 is at least 0.5 phr.

The sulphur is usually provided in the form of molecular sulphur or a sulphur donor, preferably in the form of molecules. Sulfur in molecular form is also referred to by the term "molecular sulfur". The term "sulfur donor" means any compound that releases a sulfur atom, optionally bound in the form of polysulfide chains, which can be inserted into polysulfide chains formed during vulcanization and bridging of elastomer chains. The sulfur content of the rubber composition is preferably less than 1phr, preferably between 0.3phr and 1 phr.

According to a more preferred embodiment of the invention, the sulfur content of the rubber composition is less than 0.95phr, preferably between 0.3phr and 0.95 phr.

According to an even more preferred embodiment of the invention, the sulfur content in the rubber composition is less than 0.8phr, preferably between 0.3phr and 0.8 phr.

The vulcanization accelerator is a mixture of a primary accelerator and a secondary accelerator. The term "primary accelerator" means either a single primary accelerator or a mixture of primary accelerators. Similarly, the term "secondary accelerator" means a single primary accelerator or a mixture of secondary accelerators. Thus, the primary accelerator (whether or not it is in the form of a mixture) and the secondary accelerator (whether or not it is in the form of a mixture) constitute the sole accelerators of the rubber composition. By definition, the content of both primary and secondary accelerators in the vulcanization system is strictly greater than 0 phr.

As (primary or secondary) vulcanization accelerator, any compound capable of acting as vulcanization accelerator of the diene elastomer in the presence of sulfur can be used, in particular accelerators of the thiazole type and their derivatives, of the sulfenamide type (for primary accelerators), or of the thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type (for secondary accelerators).

As examples of primary accelerators, mention may in particular be made of sulfenamide compounds, such as N-cyclohexyl-2-benzothiazylsulfenamide ("CBS"), N-dicyclohexyl-2-benzothiazylsulfenamide ("DCBS"), N-tert-butyl-2-benzothiazylsulfenamide ("TBBS") and mixtures of these compounds. The primary accelerator is preferably a sulfenamide, more preferably N-cyclohexyl-2-benzothiazolyl sulfenamide.

As examples of secondary accelerators, mention may in particular be made of thiuram disulfides, such as tetraethylthiuram disulfide, tetrabutylthiuram disulfide ("TBTD"), tetrabenzylthiuram disulfide ("TBZTD"), and also mixtures of these compounds. The secondary accelerator is preferably thiuram disulfide, more preferably tetrabenzylthiuram disulfide.

Preferably, the vulcanization accelerator is a mixture of a sulfenamide and thiuram disulfide. The vulcanization accelerator is advantageously a mixture of N-cyclohexyl-2-benzothiazylsulfenamide and thiuram disulfide, more advantageously a mixture of N-cyclohexyl-2-benzothiazylsulfenamide and tetrabenzylthiuram disulfide.

According to the invention, the mass ratio between the amount of secondary accelerator and the total amount of accelerators, which is the sum of the amount by mass of primary accelerator and the amount by mass of secondary accelerator in the rubber composition, is less than 0.7. In other words, the mass content or amount by mass of the secondary accelerator accounts for less than 70 mass% of the total amount of the accelerator. Preferably, the mass ratio between the amount of secondary accelerator and the total amount of accelerator is greater than 0.05, more particularly between 0.05 and 0.7.

Preferably, the mass ratio between the amount of secondary accelerator and the total amount of accelerators is preferably less than 0.5, even more preferably less than or equal to 0.3. These preferred ranges enable even further optimization of the compromise between cohesion properties and curing time of the vulcanizer by greatly reducing the vulcanization time, while maintaining good ultimate properties, even in the presence of crack initiation sites in the rubber composition.

According to a preferred embodiment, the mass ratio between the sulphur content and the total amount of accelerators in the rubber composition is less than 1, preferably less than or equal to 0.7, more preferably less than 0.6. The use of such a ratio makes it possible to obtain a composition having further improved cohesion properties.

According to a particularly preferred embodiment of the invention, the sulfur content in the rubber composition is less than 1phr and the mass ratio between the sulfur content and the total amount of accelerators in the rubber composition is less than 1. These two conditions, related to the sulphur content and to the mass ratio between sulphur content and total amount of accelerator, make it possible to obtain compositions with even higher cohesion. The cohesive properties can be further improved when the sulphur content and the mass ratio between the sulphur content and the total amount of accelerator are relatively low and in particular within the preferred ranges of the sulphur content mentioned in claims 7 and 8 and the mass ratio between the sulphur content and the total amount of accelerator mentioned in claim 10.

The vulcanization system may also include a vulcanization activator, such as a metal oxide (e.g., zinc oxide) or a fatty acid (e.g., stearic acid), in a known manner.

According to the invention, the rubber composition comprises carbon black as reinforcing filler. The reinforcing filler is generally composed of nanoparticles, the average (mass average) size of which is less than one micron, generally less than 500nm, generally between 20nm and 200nm, particularly and more preferably between 20nm and 150 nm.

Any carbon black, in particular carbon black conventionally used in tires or treads thereof (referred to as tire grade carbon black), is suitable for use as the carbon black. Among the tire-grade blacks, mention will more particularly be made of reinforcing blacks of the series 100, 200 and 300, or blacks of the series 500, 600 or 700 (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 blacks. When the rubber composition according to the invention is used in a tread, the carbon black is preferably a carbon black of the 100 or 200 series.

The content of carbon black can vary within wide limits and can be adjusted by the person skilled in the art according to the intended use of the rubber composition, in particular in the field of tires. For the use of the rubber composition in treads (in particular for vehicles intended to carry heavy loads), the content of carbon black in the rubber composition is preferably between 25phr and 65 phr. For such use in the field of heavy goods vehicles, below 25phr the level of reinforcement of the rubber composition may be insufficient, and above 65phr the rubber composition may show excessive hysteresis.

The rubber compositions which can be used for the purposes of the present invention may also comprise all or part of the usual additives conventionally used in elastomeric compositions intended for tires (for example tire treads). Such additives are, for example, fillers (e.g. silica, alumina), processing aids, plasticizers, pigments, protective agents (e.g. antiozone waxes, chemical antiozonants and antioxidants).

The rubber compositions can be manufactured in a suitable mixer using two successive preparation stages according to general procedures known to those skilled in the art: a first stage of thermomechanical working or kneading at high temperature (sometimes called "non-productive" stage), with a maximum temperature between 110 ℃ and 190 ℃, preferably between 130 ℃ and 180 ℃, followed by a second stage of mechanical working at low temperature (sometimes called "productive" stage), generally less than 110 ℃, for example between 40 ℃ and 100 ℃, during which stage sulfur or a sulfur donor and a vulcanization accelerator are added.

For example, the first stage (non-productive) is carried out in a single thermomechanical step, during which all the necessary components, with the exception of the sulphur and the vulcanization accelerator, optionally further processing aids and other various additives, are added to a suitable mixer (for example a conventional internal mixer). The total kneading time in this non-productive phase is preferably between 1 and 15 minutes. After cooling the mixture obtained during the first non-productive phase, sulphur and vulcanization accelerators are then added, usually at low temperature, in an open mixer (for example an open mill); all substances are then mixed (production phase) for several minutes, for example between 2 and 15 minutes.

The rubber composition may be calendered or extruded, preferably to form all or part of a tread molding for a tire.

The tire, which is another subject of the present invention, comprising the rubber composition according to the invention, preferably comprises the rubber composition in its tread, in particular the part of the tread intended to be in contact with rolling ground and consisting wholly or partly of the rubber composition according to the invention. The tire may be in a green form (i.e., before the step of curing the tire) or in a cured form (i.e., after the step of curing the tire). The tire is preferably a tire for vehicles intended to carry heavy loads, such as heavy goods vehicles and civil engineering vehicles.

The above-mentioned and other features of the invention will be more clearly understood from a reading of the following description of several embodiments of the invention, given as a non-limiting illustration.

Examples of the invention

II.1 testing and measurement:

II.1-1 determination of the microstructure of the elastomer:

by passing¹H NMR analysis of the elastomer to determine the microstructure of the elastomer when¹When the resolution of the H NMR spectrum does not allow the assignment and quantification of all species, it can be combined¹³C NMR analysis. Measurements were made using a Bru ker 500MHz NMR spectrometer at a frequency of 500.43MHz for proton observation and a frequency of 125.83MHz for carbon observation.

For insoluble elastomers with swelling capacity in solvent, protons and carbon were observed in proton decoupling mode using a 4mm z-grade HRMAS probe. Spectra were collected at rotation speeds of 4000Hz to 5000 Hz.

For the measurement of soluble elastomers, protons and carbon were observed in proton decoupling mode using a liquid NMR probe.

The preparation of insoluble samples was carried out in a rotor filled with the analyzed material and a deuterated solvent enabling swelling, typically deuterated chloroform (CDCl 3). The solvent used must always be a deuterated solvent and its chemical properties can be adjusted by the person skilled in the art. The amount of material used is adjusted so as to obtain a spectrum with sufficient sensitivity and resolution.

The soluble sample was dissolved in deuterated solvent, typically deuterated chloroform (CDCl3) (about 25mg of elastomer in 1 mL). The solvent or solvent blend used must always be a deuterated solvent and its chemical properties can be adjusted by the person skilled in the art.

In both cases (soluble or swollen samples):

for proton NMR, a 30 ° simple pulse sequence was used. The spectral window is set to observe all resonance lines belonging to the molecule analyzed. The accumulated number is set so as to obtain a signal-to-noise ratio sufficient to quantify each unit. The cyclic delay between each two pulses is adjusted to obtain a quantitative measurement.

For carbon NMR, a 30 ° simple pulse sequence was used, and proton decoupling was performed only during acquisition, thereby avoiding the nuclear austenite effect (NOE) and maintaining quantitation. The spectral window is set to observe all resonance lines belonging to the molecule analyzed. The accumulated number is set so as to obtain a signal-to-noise ratio sufficient to quantify each unit. The cyclic delay between each two pulses is adjusted to obtain a quantitative measurement.

NMR measurements were carried out at 25 ℃.

II.1-2 mechanical Strength in the presence of crack initiation sites (tear):

tear strength and deformation were measured on samples stretched at 500mm/min to break the samples. The tensile test specimen consists of a rubber sheet of parallelepiped shape, for example, between 1mm and 2mm thick, between 130mm and 170mm long and between 10mm and 15mm wide, the two side edges being longitudinally covered with cylindrical beads (5 mm diameter) for anchoring to the jaws of the tensile tester. Before starting the test, three very thin notches of a length between 15mm and 20mm were cut parallel to the longitudinal direction of the test piece at the median length using razor blades, two notches being located at the ends of the test piece and one notch being located in the center of the test piece. The force applied to obtain a break (N/mm) was measured and the elongation at break was measured. The test was carried out in air at a temperature of 100 ℃. Higher values represent good cohesion of the rubber composition (despite having crack initiation sites).

II.1-3 tensile test:

the elongation at break (EB%) and stress at Break (BS) tests are based on standard NF ISO 37 on H2 dumbbell specimens for 12 months of 2005 and are measured at a traction speed of 500 mm/min. Elongation at break is expressed as percent elongation. The breaking stress is expressed in MPa. All these tensile test measurements were performed at 60 ℃.

II.1-4 curing Properties:

according to DIN 53529-part 3 (6 months 1983), measurements were made at 150 ℃ using a vibrating chamber rheometer. The change in rheological torque over time depicts the change in stiffness of the composition caused by the vulcanization reaction. The measurement was carried out in accordance with standard DIN 53529-part 2 (3 months 1983). Ti is the induction period, i.e. the time required to start the sulfidation reaction. T95 is the time required to reach 95% conversion, i.e. 95% of the difference between the minimum and maximum torque. The first order conversion constant (expressed as K (in min)) calculated between 30% and 80% conversion was also measured^-1Expression)), which enables the evaluation of vulcanization kinetics.

II.2 preparation of rubber composition:

the rubber compositions were prepared in the following manner, and the detailed formulations are given in table 1:

the elastomer, the reinforcing filler and various other ingredients, except sulfur and the vulcanization accelerator, were continuously fed into an internal mixer (final filling degree: about 70 vol%) whose initial vessel temperature was about 80 ℃. Thermomechanical working (non-productive phase) is then carried out in one step, for a total of about 3 to 4 minutes, until a maximum "tapping" temperature of 165 ℃ is reached. The mixture thus obtained is recovered and cooled, then the sulfur and the vulcanization accelerator are introduced into a mixer (homogenizing finisher) at 30 ℃ and all the substances are kneaded (production stage) for a suitable time (for example, about ten minutes).

The compositions thus obtained are subsequently calendered, either in the form of rubber sheets (thickness from 2mm to 3mm) or of rubber sheets (for measuring their physical or mechanical properties), or extruded in the form of tire treads.

An Elastomer (EBR) was prepared according to the following procedure:

30mg of metallocene ({ Me)₂SiFlu₂Nd(μ-BH₄)₂Li(THF)}₂The symbol Flu represents the formula C₁₃H₈Fluorenyl) was added to the first Steinie bottle in a glove box. The cocatalyst butyloctylmagnesium, previously dissolved in 300ml of methylcyclohexane in the second Steinie bottle, was added to the first Steinie bottle containing the metallocene in the following ratio: 0.00007mol/L of metallocene, 0.0004mol/L of cocatalystAnd (3) preparing. After 10 minutes of contact at room temperature, a catalytic solution was obtained. The catalytic solution is then added to the polymerization reactor. The temperature in the reactor was then raised to 80 ℃. When this temperature was reached, the reaction was started by injecting a gaseous mixture of ethylene and 1, 3-butadiene (80/20 mol%) into the reactor. The polymerization was carried out at a pressure of 8 bar. The ratio of metallocene to cocatalyst was 0.00007mol/L and 0.0004mol/L, respectively. The polymerization was terminated by cooling, degassing of the reactor and addition of ethanol. An antioxidant is added to the polymer solution. The copolymer was recovered by drying in a vacuum oven.

Rubber compositions C5 to C11 are rubber compositions according to the invention. Rubber compositions C12 and C13 are rubber compositions not according to the invention, in which the ratio between the amount by mass of the secondary accelerator and the sum of the amount by mass of the primary accelerator and the amount by mass of the secondary accelerator is not less than 0.7. Compositions C1 to C4, which do not comprise any secondary accelerator, are compositions not according to the invention.

II.3 results:

the results are given in table 2.

The results show that rubber compositions C5 to C11 are rubber compositions that show the best compromise between cohesion properties and curing time in the vulcanization machine. Of these compositions according to the invention, compositions C5 to C10 proved to be the most advantageous in terms of cohesion properties and cure time on the curing press. Composition C13 not in accordance with the invention, in which the secondary accelerator was the sole accelerator in the rubber composition, was able to reduce the curing time of the vulcanizer, but this result was obtained at the expense of the cohesive properties. Composition C12 not according to the invention, in which the secondary accelerator represents more than 70% by mass of the accelerator used, is also capable of reducing the curing time of the vulcanizer, but this result is also obtained at the expense of the cohesive properties.

For compositions C1 to C4 not according to the invention, they had good cohesive properties, but since the curing time of the vulcanizer was very long, these results were obtained at the expense of the curing properties related to productivity.

TABLE 1

Composition comprising a metal oxide and a metal oxide	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13
														EBR(1)	100	100	100	100	100	100	100	100	100	100	100	100	100
Carbon black (2)	40	40	40	40	40	40	40	40	40	40	40	40	40
														Antioxidant (3)	2	2	2	2	2	2	2	2	2	2	2	2	2
Anti-ozone wax	1	1	1	1	1	1	1	1	1	1	1	1	1
														Stearic acid	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
ZnO	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5
														Accelerator 1(4)	1.2	0.8	1.1	1.43	1.13	1.07	1.01	0.95	0.96	0.96	0.66	0.36	-
Accelerator 2(5)	-	-	-	-	0.13	0.19	0.25	0.31	0.10	0.15	0.6	0.9	1.26
														Total accelerator (6)	1.2	0.8	1.1	1.43	1.26	1.26	1.26	1.26	1.06	1.11	1.26	1.26	1.26
Ratio (7)	0	0	0	0	0.1	0.15	0.2	0.25	0.09	0.14	0.48	0.71	1
														Sulfur	0.5	1.5	1.1	0.94	0.56	0.56	0.56	0.56	0.70	0.45	0.56	0.56	0.56
Sulfur/accelerators	0.4	1.8	1	0.66	0.44	0.44	0.44	0.44	0.66	0.41	0.44	0.44	0.44

(1) Elastomer comprising 79 mol% of ethylene units, 7 mol% of 1, 2-cyclohexanediyl units, 8 mol% of 1, 2-units of a butadiene moiety and 6 mol% of 1, 4-units of a butadiene moiety

(2)N234

(3) N- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine (Santoflex 6-PPD from Flexsys Inc.)

(4) N-cyclohexyl-2-benzothiazolesulfenamide (Santocure CBS from Flexsys Co.)

(5) Tetrabenzylthiuram disulfide (Perkacit TBZTD from Flexsys Co.)

(6) Total amount of accelerator

(7) Mass ratio between the amount of accelerator 2 and the total amount of accelerator.

TABLE 2