ELASTOMER LAMINATE

Abstract

An elastomer laminate comprises at least two adjacent layers, the first layer consisting of a composition based on 20 to 100 phr of at least one copolymer comprising ethylene units and units of a formula CH.sub.2?CRCH?CH.sub.2, the ethylene units in the copolymer representing more than 50 mol % of the monomer units, R representing a hydrocarbon chain having 3 to 20 carbon atoms, 0 to 80 phr of at least one diene elastomer having a weight content of diene units of greater than 50%, 10 to 100 phr of a plasticizing system comprising at least one plasticizing resin having a glass transition temperature above 20? C. and/or at least one plasticizer that is liquid at 23? C., a reinforcing filler, and a crosslinking system, and the second layer consisting of a composition based on a diene elastomer having a weight content of diene units of greater than 50% and a crosslinking system.

Claims

1.-15. (canceled)

16. An elastomer laminate comprising at least two adjacent layers, the first layer consisting of a rubber composition based on: 20 to 100 phr of at least one copolymer comprising ethylene units and units of a 1,3-diene of formula (I), the ethylene units in the copolymer representing more than 50 mol % of monomer units of the copolymer,
CH.sub.2?CRCH?CH.sub.2(I), R representing a hydrocarbon chain having 3 to 20 carbon atoms; 0 to 80 phr of at least one diene elastomer having a weight content of diene units of greater than 50%; 10 to 100 phr of a plasticizing system comprising at least one plasticizing resin having a glass transition temperature above 20? C. and/or at least one plasticizer that is liquid at 23? C.; a reinforcing filler; and a crosslinking system, and the second layer consisting of a rubber composition based on a diene elastomer having a weight content of diene units of greater than 50% and a crosslinking system.

17. The elastomer laminate according to claim 16, wherein the 1,3-diene of formula (I) of the copolymer of the first layer is myrcene, ?-farnesene or a mixture of myrcene and ?-farnesene.

18. The elastomer laminate according to claim 16, wherein the copolymer further comprises a second 1,3-diene selected from 1,3-butadiene, isoprene or a mixture thereof.

19. The elastomer laminate according to claim 16, wherein the content of the copolymer of ethylene and of a 1,3-diene of formula (I) in the rubber composition of the first layer is within a range extending from 20 to 90 phr, and wherein the diene elastomer having a weight content of diene units of greater than 50% is present in the rubber composition of the first layer at a content within a range extending from 10 to 80 phr.

20. The elastomer laminate according to claim 16, wherein the diene elastomer having a weight content of diene units of greater than 50% of the rubber composition of the first layer is selected from the group consisting of polybutadienes (BRs), natural rubber (NR), synthetic polyisoprenes (IRs), butadiene copolymers, isoprene copolymers and mixtures thereof.

21. The elastomer laminate according to claim 16, wherein the plasticizing system comprises a plasticizer that is liquid at 23? C. and a plasticizing resin having a glass transition temperature above 20? C.

22. The elastomer laminate according to claim 16, wherein the plasticizer that is liquid at 23? C. of the rubber composition of the first layer is selected from the group consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures thereof.

23. The elastomer laminate according to claim 16, wherein the content of plasticizer that is liquid at 23? C., in the rubber composition of the first layer, is within a range extending from 1 to 49 phr.

24. The elastomer laminate according to claim 16, wherein the plasticizing resin having a glass transition temperature above 20? C. of the rubber composition of the first layer is selected from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C.sub.5 fraction homopolymer or copolymer resins, C.sub.9 fraction homopolymer or copolymer resins, ?-methylstyrene homopolymer or copolymer resins and mixtures thereof.

25. The elastomer laminate according to claim 16, wherein the content of plasticizing resin having a glass transition temperature above 20? C., in the rubber composition of the first layer, is within a range extending from 1 to 99 phr.

26. The elastomer laminate according to claim 16, wherein the content of reinforcing filler in the rubber composition of the first layer is within a range extending from 30 to 200 phr.

27. The elastomer laminate according to claim 16, wherein the diene elastomer having a weight content of diene units of greater than 50% of the rubber composition of the second layer is selected from the group consisting of polybutadienes (BRs), natural rubber (NR), synthetic polyisoprenes (IRs), butadiene copolymers, isoprene copolymers and mixtures thereof.

28. The elastomer laminate according to claim 16, wherein the diene elastomer having a weight content of diene units of greater than 50% of the first layer and the diene elastomer having a weight content of diene units of greater than 50% of the second layer are polyisoprenes comprising a weight content of 1,4-cis bonds of at least 90% of the weight of the polyisoprene.

29. The elastomer laminate according to claim 16, wherein the first layer has a thickness within a range extending from 0.2 to 120 mm, and wherein the second layer has a thickness within a range extending from 0.2 to 10 mm.

30. A rubber article comprising the elastomer laminate according to claim 16.

31. The rubber article according to claim 30, wherein the rubber article is selected from the group consisting of pneumatic tires, non-pneumatic tires, caterpillar tracks, conveyor belts and anti-vibratory articles.

Description

IV EXAMPLES

[0235] IV-1 Measurements and Tests Used

[0236] IV-1.1 Determination of the Microstructure of the Elastomers: [0237] a) Determination of the microstructure of the ethylene-butadiene copolymers (Elastomer E1):

[0238] The microstructure of the ethylene-butadiene copolymers is determined by .sup.1H NMR analysis, assisted by .sup.13C NMR analysis when the resolution of the .sup.1H NMR spectra does not make it possible to assign and quantify all the species. The measurements are performed using a Bruker 500 MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83 MHz for carbon observation. For the elastomers which are insoluble but which have the ability to swell in a solvent, a 4 mm z-grad HR-MAS probe is used for proton and carbon observation in proton-decoupled mode. The spectra are acquired at rotational speeds of from 4000 Hz to 5000 Hz. For the measurements on soluble elastomers, a liquid NMR probe is used for proton and carbon observation in proton-decoupled mode. The preparation of the insoluble samples is performed in rotors filled with the analysed material and a deuterated solvent enabling swelling, generally deuterated chloroform (CDCl.sub.3). The solvent used must always be deuterated and its chemical nature may be adapted by those skilled in the art. The amounts of material used are adjusted so as to obtain spectra of sufficient sensitivity and resolution. The soluble samples are dissolved in a deuterated solvent (about 25 mg of elastomer in 1 ml), generally deuterated chloroform (CDCl.sub.3). The solvent or solvent blend used must always be deuterated and its chemical nature may be adapted by those skilled in the art. In both cases (soluble sample or swollen sample): A 300 single pulse sequence is used for proton NMR. The spectral window is set to observe all of the resonance lines belonging to the analysed molecules. The accumulation number is adjusted in order to obtain a signal to noise ratio that is sufficient for the quantification of each unit. The recycle delay between each pulse is adapted to obtain a quantitative measurement. A 30? single pulse sequence is used for carbon NMR, with proton decoupling only during the acquisition to avoid nuclear Overhauser effects (NOE) and to remain quantitative. The spectral window is set to observe all of the resonance lines belonging to the analysed molecules. The accumulation number is adjusted in order to obtain a signal to noise ratio that is sufficient for the quantification of each unit. The recycle delay between each pulse is adapted to obtain a quantitative measurement. The NMR measurements are performed at 25? C. [0239] b) Determination of the microstructure of the ethylene-myrcene copolymers (Elastomer E2):

[0240] The spectral characterization and the measurements of the microstructure of the ethylene-myrcene copolymers are carried out by nuclear magnetic resonance (NMR) spectroscopy.

[0241] Spectrometer: For these measurements, a Bruker Avance III HD 400 MHz spectrometer is used, equipped with a Bruker 5 mm z-grad cryo-BBFO probe.

[0242] Experiments: The .sup.1H experiments are recorded using a radiofrequency pulse with a tilt angle of 30?, the number of repetitions is 128 with a recycle delay of 5 seconds. The HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation).sup.1H-.sup.13C NMR correlation experiments are recorded with a number of repetitions of 128 and a number of increments of 128. The experiments are carried out at 25? C.

[0243] Preparation of the sample: 25 mg of sample are dissolved in 1 ml of deuterated chloroform (CDCl.sub.3).

[0244] Sample calibration: The axes of the .sup.1H and .sup.13C chemical shifts are calibrated with respect to the protonated impurity of the solvent (CHCl.sub.3) at ?.sub.1H=7.2 ppm (for the most shielded signal) and ?.sub.13C=77 ppm (for the least shielded signal).

[0245] Spectral assignment for the copolymers of ethylene and of 1,3-myrcene: In the representations A, B and C below, the symbols R1 and R2 represent the attachment points of the unit to the polymer chain. The signals of the insertion forms of the 1,3-diene A, B and C were observed on the different spectra recorded. According to S. George et al., (Polymer 55 (2014) 3869-3878), the signal of the CH=group No. 8 characteristic of form C exhibits .sup.1H and .sup.13C chemical shifts identical to the CH=group No. 3. The chemical shifts of the signals characteristic of the moieties A, B and C are presented in Table 1. The moieties A, B and C correspond respectively to the units of 3,4 configuration, of 1,2 configuration and of trans-1,4 configuration. The quantifications were carried out from the integration of the 1D .sup.1H NMR spectra using the Topspin software. The integrated signals for the quantification of the various moieties are: [0246] Ethylene: signal at 1.2 ppm corresponding to 4 protons [0247] Total myrcene: signal No. 1 (1.59 ppm) corresponding to 6 protons [0248] Form A: signal No. 7 (4.67 ppm) corresponding to 2 protons [0249] Form B: signal No. 8 (5.54 ppm) corresponding to 1 proton.

[0250] The quantification of the microstructure is carried out in molar percentage (molar %) as follows: Molar % of a moiety=.sup.1H integral of a moiety?100/E(.sup.1H integrals of each moiety).

TABLE-US-00001 TABLE 1 ?.sub.1H (ppm) ?.sub.13C (ppm) Group 5.54 146.4 .sup.8 5.07 124.6 3 + 8 4.97-4.79 112.0 .sup.9 4.64 108.5 7 2.03 26.5 4 2.0-1.79 31.8 5 + 5 + 5 44.5 8 1.59 25.9 and 17.0 1 1.2 36.8-24.0 ethylene CH.sub.2

##STR00003## [0251] c) Determination of the microstructure of the ethylene-butadiene-myrcene terpolymers (Elastomer E3):

[0252] The spectral characterization and the measurements of the ethylene-butadiene-myrcene copolymer microstructure are carried out by nuclear magnetic resonance (NMR) spectroscopy.

[0253] For these measurements, a Bruker Avance III HD 400 MHz spectrometer is used, equipped with a Bruker 5 mm z-grad cryo-BBFO probe. The .sup.1H experiments are recorded using a radiofrequency pulse with a tilt angle of 30?, the number of repetitions is 128 with a recycle delay of 5 seconds. The HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation).sup.1H-.sup.13C NMR correlation experiments are recorded with a number of repetitions of 128 and a number of increments of 128. The experiments are carried out at 25? C.

25 mg of sample are dissolved in 1 ml of deuterated ortho-dichlorobenzene (ODCB).

[0254] The axes of the .sup.1H and .sup.13C chemical shifts are calibrated with respect to the protonated impurity of the solvent at ?.sub.1H=7.2 ppm (for the most shielded signal) and ?.sub.13C=127 ppm (for the least shielded signal).

[0255] The possible monomer units in the terpolymer are CH.sub.2CH(CH?CH.sub.2), CH.sub.2CH?CHCH.sub.2, CH.sub.2CH.sub.2, the 1,2-cyclohexanediyl moiety and the following structures, R.sub.1 and R.sub.2 representing the polymer chain:

##STR00004##

[0256] The 1,2-cyclohexanediyl moiety has the following structure:

##STR00005##

[0257] The signals of the insertion forms of myrcene A were observed on the different spectra recorded. According to S. Georges et al. (S. Georges, M. Bria, P. Zinck and M. Visseaux., Polymer, 55 (2014), 3869-3878), the signal of the CH=group No. 8 characteristic of the form C exhibits identical .sup.1H and .sup.13C chemical shifts to the CH=group No. 3.

[0258] The chemical shifts of the signals characteristic of the polymer are presented in Table 2 (Assignment of the .sup.1H and .sup.13C signals of the ethyl ene-butadiene-myrcene terpolymers other than those of the units of the 1,3-butadiene).

TABLE-US-00002 TABLE 2 ?.sub.1H (ppm) ?.sub.13C (ppm) Group 5.19 125.1 3 + 8 4.86 109.0 7 1.59 and 1.68 247 and 17.6 1 1.3 37.5-24.0 ethylene CH.sub.2

[0259] The quantifications were carried out from the integration of the 1D .sup.1H NMR spectra using the Topspin software.

[0260] The integrated signals for the quantification of the various moieties are: Ethylene: All of the signals between 0.5 ppm and 3.0 ppm by subtracting the aliphatic contributions of the other moieties of the terpolymer. The calculation corresponds to 4 protons of the ethylene moiety.

[0261] Form A: signal No. 7 (4.86 ppm) corresponding to 2 protons.

[0262] The proportion of form C is not directly accessible but can be calculated from the signal No. 3+8 by subtracting the contribution of the form A.

[0263] PB1-4: Signal between 5.71 ppm and 5.32 ppm corresponds to 2 protons (by removing the PB1-2 contribution).

[0264] PB1-2: signal between 5.11 ppm and 4.92 ppm corresponds to 2 protons.

[0265] Cyclohexane rings: signal between 1.80 ppm and 1.70 ppm corresponds to 2 protons.

[0266] The quantification of the microstructure is carried out in molar percentage (molar %) as follows:

molar % of a moiety=.sup.1H integral of a moiety*100/?(.sup.1H integrals of each moiety). [0267] c) Determination of the microstructure of the ethylene-butadiene-farnesene terpolymers (Elastomers E4 and E5):

[0268] The spectral characterization and the measurements of the ethylene-butadiene-farnesene copolymer microstructure are carried out by Nuclear Magnetic Resonance (NMR) spectroscopy. For these measurements, a Bruker Avance III HD 400 MHz spectrometer is used, equipped with a Bruker 5 mm z-grad cryo-BBFO probe. The .sup.1H experiments are recorded using a radiofrequency pulse with a tilt angle of 30?, the number of repetitions is 128 with a recycle delay of 5 seconds. The HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation).sup.1H-.sup.13C NMR correlation experiments are recorded with a number of repetitions of 128 and a number of increments of 128. The experiments are carried out at 25? C. 25 mg of sample are dissolved in 1 ml of deuterated ortho-dichlorobenzene (ODCB). The axes of the .sup.1H and .sup.13C chemical shifts are calibrated with respect to the protonated impurity of the solvent at ?.sub.1H=7.2 ppm (for the most shielded signal) and ?.sub.13C=127 ppm (for the least shielded signal). The possible monomer units in the terpolymer are CH.sub.2CH(CH?CH.sub.2), CH.sub.2CH?CHCH.sub.2, CH.sub.2CH.sub.2, the 1,2-cyclohexanediyl moiety and the following structures, R.sub.1 and R.sub.2 representing the polymer chain.

##STR00006##

[0269] The signals of the insertion form of farnesene A were observed on the different spectra recorded. The signal of the CH=group No. 11 characteristic of the form C exhibits identical .sup.1H and .sup.13C chemical shifts to the CH=groups No. 3 and No. 7.

[0270] The chemical shifts of the signals characteristic of the polymer are presented in Table 3 (Assignment of the .sup.1H and .sup.13C signals of the ethylene-butadiene-farnesene terpolymers other than those of the units of the 1,3-butadiene).

TABLE-US-00003 TABLE 3 ?.sub.1H (ppm) ?.sub.13C (ppm) Group 5.25 125.0 7 5.15 125.0 3, 11 4.87 109.0 14 1.59 and 1.67 24.6 and 17.5 1, 13 1.28 38-24.0 ethylene CH.sub.2

[0271] The quantifications were carried out from the integration of the 1D .sup.1H NMR spectra using the Topspin software.

[0272] The integrated signals for the quantification of the various moieties are: Farnesene moiety form A from the signal No. 14 CH.sub.2? for 2 protons, Farnesene moiety form C from the signals No. 3, 11 and No. 7 CH?(by subtracting the contribution of the form A), for 2 protons,

[0273] Farnesene moiety form B: from the signal No. 11, specific to this form, for 1 proton.

[0274] PB1-4: Signal between 5.71 ppm and 5.32 ppm corresponds to 2 protons (by removing the PB1-2 contribution).

[0275] PB1-2: signal between 5.11 ppm and 4.92 ppm corresponds to 2 protons.

[0276] Cyclohexane rings: signal between 1.80 ppm and 1.70 ppm corresponds to 2 protons.

[0277] Ethylene moiety by integrating all of the aliphatic signals (from ? 0.5 to 3 ppm) and by subtracting the contribution of all the other aliphatic moieties (PB1-4, PB1-2, EBR ring, farnesene forms A and C).

[0278] The quantification of the microstructure is carried out in molar percentage (molar %) as follows:

molar % of a moiety=.sup.1H integral of a moiety*100/?(.sup.1H integrals of each moiety).

[0279] IV-1.2 Determination of the Glass Transition Temperature of the Polymers:

[0280] The glass transition temperature is measured by means of a differential calorimeter (differential scanning calorimeter) according to Standard ASTM D3418 (1999).

[0281] IV-1.3 Determination of the Macrostructure of the Polymers by Size Exclusion Chromatography (SEC): [0282] a) Principle of the measurement:

[0283] Size-exclusion chromatography or SEC makes it possible to separate macromolecules in solution according to their size by passage through columns packed with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the bulkiest being eluted first.

[0284] In combination with 3 detectors (3D)a refractometer, a viscometer and a 900 light-scattering detectorSEC gives a picture of the distribution of the absolute molar masses of a polymer. The various number-average (Mn) and weight-average (Mw) absolute molar masses and the dispersity (D=Mw/Mn) can also be calculated. [0285] b) Preparation of the polymer:

[0286] Each sample is dissolved in tetrahydrofuran at a concentration of approximately 1 g/l. The solution is then filtered through a filter with a porosity of 0.45 ?m before injection. [0287] c) 3D SEC analysis:

[0288] In order to determine the number-average molar mass (Mn), and if appropriate the weight-average molar mass (Mw) and the polydispersity index (PI), of the polymers, the method below is used.

[0289] The number-average molar mass (Mn), the weight-average molar mass (Mw) and the polydispersity index of the polymer (hereinafter sample) are determined in an absolute manner by triple detection size exclusion chromatography (SEC). Triple detection size exclusion chromatography has the advantage of measuring average molar masses directly without calibration.

[0290] The value of the refractive index increment dn/dc of the sample solution is measured online using the area of the peak detected by the refractometer (RI) of the liquid chromatography equipment. To apply this method, it must be verified that 100% of the sample mass is injected and eluted through the column. The area of the RI peak depends on the concentration of the sample, on the constant of the RI detector and on the value of the dn/dc.

[0291] In order to determine the average molar masses, use is made of the 1 g/l solution previously prepared and filtered, which is injected into the chromatographic system. The apparatus used is a Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran containing 250 ppm of BHT (2,6-di(tert-butyl)-4-hydroxytoluene), the flow rate is 1 ml.Math.min.sup.?1, the temperature of the system is 35? C. and the analytical time is 60 min. The columns used are a set of three Agilent columns of PL Gel Mixed B LS trade name. The volume of the solution of the sample injected is 100 ?l. The detection system is composed of a Wyatt differential viscometer of Viscostar II trade name, of a Wyatt differential refractometer of Optilab T-Rex trade name of wavelength 658 nm and of a Wyatt multi-angle static light scattering detector of wavelength 658 nm and of Dawn Heleos 8+ trade name.

[0292] For the calculation of the number-average molar masses and the polydispersity index, the value of the refractive index increment dn/dc of the solution of the sample obtained above is integrated. The software for processing the chromatographic data is the Astra system from Wyatt.

[0293] IV-2 Synthesis of the polymers:

[0294] In the synthesis of polymers, all the reactants are obtained commercially except the metallocenes. The butyloctylmagnesium BOMAG (20% in heptane, C=0.88 mol.1.sup.4) originates from Chemtura and is stored in a Schlenk tube under an inert atmosphere. The ethylene, of N35 grade, is obtained from the company Air Liquide and is used without prior purification. The myrcene (purity>95%) and farnesene (purity>95%) are obtained from Sigma-Aldrich.

[0295] The following polymers are synthesized according to the procedure described below: [0296] copolymer of ethylene and 1,3-butadiene: elastomer E1 (not in accordance with the invention) [0297] copolymer of ethylene and myrcene: elastomer E2 (in accordance with the invention) [0298] copolymer of ethylene, butadiene and farnesene: elastomer E3 (in accordance with the invention) [0299] copolymers of ethylene, butadiene and myrcene: elastomers E4 and E5 (in accordance with the invention)

[0300] To a reactor containing, at 80? C., methylcyclohexane and also ethylene (Et) and butadiene (Bd) and/or myrcene (Myr) and/or farnesene (Far) in the proportions indicated in Table 4, butyloctylmagnesium (BOMAG) is added to neutralize the impurities in the reactor, then the catalytic system is added (see Table 4). At this time, the reaction temperature is regulated at 80? C. and the polymerization reaction starts. The polymerization reaction takes place at a constant pressure of 8 bar. The reactor is fed throughout the polymerization with ethylene and butadiene (Bd) and/or myrcene (Myr) and/or farnesene (Far) in the proportions defined in Table 4. The polymerization reaction is stopped by cooling, degassing of the reactor and addition of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from a metallocene, [Me.sub.2SiFlu.sub.2Nd(BH.sub.4).sub.2Li(THF)], a co-catalyst, butyloctylmagnesium (BOMAG), and a preformation monomer, 1,3-butadiene, in the contents indicated in Table 4. It is prepared according to a preparation method in accordance with paragraph II.1 of patent application WO 2017/093654 A1.

[0301] The microstructure of the elastomers E1 to E5 and the properties thereof are shown in Tables 5 and 6. For the microstructure, Table 5 indicates the molar contents of the ethylene (Eth) units, the 1,3-butadiene units, the 1,2-cyclohexanediyl (ring) moieties, and ?-farnesene or myrcene units. Also shown therein is the molar proportion of the ?-farnesene or myrcene units according to whether they are of 1,4 configuration, 1,2 configuration or 3,4 configuration.

TABLE-US-00004 TABLE 4 Synthesis E1 E2 E3 E4 E5 Metallocene concentration 0.07 0.09 0.09 0.09 0.09 (mmol/l) Alkylating agent 0.36 0.17 0.25 0.2 0.33 concentration (mmol/l) Preformation monomer/Nd 90 90 90 90 90 metal molar ratio Composition of the feed 80/20 (mol % Et/Bd) Composition of the feed 60/40 (mol % Et/Myr) Composition of the feed 81/9/10 (mol % Eth/Btd/Far) Composition of the feed 79/14/7 70/20/10 (mol % Eth/Btd/Myr)

TABLE-US-00005 TABLE 5 Elastomer E1 E2 E3 E4 E5 Et (mol %) 77 74 76 75 68 Bd (mol %) 15 8 13 19 1,2-Cyclohexanediyl (mol %) 8 5 6 7 Far or Myr (mol %) 26 11 6 6 1,4 Far or Myr (mol %/mol % Far 31 36 33 33 or Myr) 1,2 Far or Myr (mol %/mol % Far 4 <1 <1 <1 or Myr) 3,4 Far or Myr (mol %/mol % Far 65 64 67 67 or Myr)

TABLE-US-00006 TABLE 6 Elastomer E1 E2 E3 E4 E5 Tg (? C.) ?40 ?60 ?61 ?49 ?49 Mn (g/mol) 128,888 367,400 200,800 298,000 179,500

[0302] IV-3 Preparation of the rubber compositions:

[0303] In the examples which follow, the rubber compositions were produced as described in point II-4 above. In particular, the non-productive phase was carried out in a 3 litre mixer for 5 minutes, for a mean blade speed of 50 revolutions per minute, until a maximum dropping temperature of 160? C. was reached. The productive phase was carried out in an open mill at 23? C. for 10 minutes.

[0304] IV-4 Rubber tests:

[0305] The adhesion of several rubber compositions comprising a copolymer containing ethylene units and 1,3-diene units to a composition based on natural rubber was compared according to the nature of the copolymer and the content of plasticiser in the composition.

[0306] The layer based on natural rubber to which the adhesion of compositions T1 to T6 (not in accordance with the invention) and of compositions C.sub.1 to C.sub.4 (in accordance with the invention) was tested corresponds to a composition conventionally used as an inner tyre layer, such as a carcass ply or a tread underlayer. The composition (TO) of this layer based on natural rubber is presented in Table 7 below.

[0307] The adhesion of compositions T1 to T6 and C.sub.1 to C.sub.4 to composition TO was compared. The control compositions T1 and T6 are not in accordance with the invention because the elastomer E1, which comprises more than 50 mol % of ethylene units, does not comprise a 1,3-diene unit of formula (I). Control compositions T1 to T5 are not in accordance with the invention because they do not comprise a plasticizing system in accordance with the invention. Compositions T6, C.sub.1, C.sub.2, C.sub.3 and C.sub.4 differ respectively from compositions T1, T2, T3, T4 and T5 solely by the presence of a plasticizing system in accordance with the invention. It may be noted that the silica content has been adjusted in order to keep the volume fraction of filler constant, the volume fraction of filler in a rubber composition being defined as being the ratio of the volume of the filler to the volume of all the constituents of the composition, it being understood that the volume of all the constituents is calculated by adding together the volume of each of the constituents of the composition.

[0308] The adhesion measurements were carried out using a T-peel test, also referred to as a 1800 peel test. The peel test specimens are produced by bringing into contact the two layers (the compositions constituting the layers being in the uncured state) for which the adhesion is to be tested. An incipient crack was inserted between the two layers. Each of the layers was reinforced by a composite ply which limits the deformation of said layers under tension. The test specimen, once assembled, was brought to 150? C. under a pressure of 16 bar, for 30 minutes. Strips with a width of 30 mm were then cut out using a cutting machine. The two sides of the incipient crack were subsequently placed in the jaws of an Instron tensile testing machine. The tests were carried out at 20? C. and at a pull speed of 100 mm/min. The tensile stresses were recorded and the latter were standardized by the width of the test specimen. A curve of strength per unit of width (in N/mm) as a function of the movable crosshead displacement of the tensile testing machine (between 0 and 200 mm) was obtained. The adhesion value selected corresponds to the propagation of the crack within the test specimen and thus to the mean stabilized value of the curve. The adhesion values of the examples were also standardized (base 100) relative to the control T1 for compositions T2 to T5 or relative to the control T6 for compositions C.sub.1 to C.sub.4. An index of greater than 100 indicates a greater improvement in adhesion.

[0309] The compositions tested (in phr), as well as the results obtained, are presented in Table 7.

TABLE-US-00007 TABLE 7 Compositions T0 T1 T2 T3 T4 T5 T6 C1 C2 C3 C4 Natural rubber 100 Elastomer E1 (1) 100 100 Elastomer E2 (1) 100 100 Elastomer E3 (1) 100 100 Elastomer E4 (1) 100 100 Elastomer E5 (1) 100 100 N330 (2) 35 Silica (3) 10 48 48 48 48 48 80.5 80.5 80.5 80.5 80.5 Vol. fraction of filler unkn. 16% 16% 16% 16% 16% 16% 16% 16% 16% 16% Coupling agent (4) 1 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Resin (5) 1 Resin (6) 0.5 Resin (7) 38 38 38 38 38 Oil (8) 38 38 38 38 38 DPG (9) 1 1 1 1 1 1 1 1 1 1 Ozone wax (10) 1 1 1 1 1 1 1 1 1 1 Antioxidant(11) 1 2 2 2 2 2 2 2 2 2 2 Stearic acid 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 ZnO (12) 4.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Accelerator(13) 1.5 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Sulfur 1.7 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Adhesion (N/mm) 10 8 4 5 3 14 16 25 25 25 Adhesion (base 100/E1) 100 80 40 50 30 100 115 180 180 180 (1) Elastomers E1 to E5 prepared according to the process described in point IV-2 above (2) Carbon black N330 according to Standard ASTM D-1765-2017 (3) Silica, Zeosil 1165MP, sold by Solvay (4) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, Si69 from Evonik (5) Gum rosin (rosin GEM SPE1) from Diamantino Malho (6) Escorez 1102 tackifying resin from EXXON (Mn 1370 g/mol; PDI = 2.3) (7) Escorez 5000 series petroleum hydrocarbon resin from Exxon Mobil (Tg = 52? C.) (8) MES oil, Catenex SNR, sold by Shell (9) Diphenylguanidine, Perkacit DPG from Flexsys (10) Anti-ozone wax, Varazon 4959 from Sasol Wax (11)N-(1,3-Dimethylbutyl)-N-phenyl-para-phenylenediamine Santoflex 6-PPD from Flexsys (12) Zinc oxide, industrial grade from Umicore (13)N-Cyclohexy1-2-benzothiazolesulfenamide, Santocure CBS, from Flexsys

[0310] These results show that the use of a rubber composition in accordance with the invention comprising the combination of a copolymer containing ethylene units and units of a 1,3-diene of formula (I) and of a plasticizing system in accordance with the invention makes it possible to improve the adhesion to a diene composition, compared to a rubber composition comprising a copolymer containing ethylene units and 1,3-diene units different from the 1,3-diene units of formula (I) and/or compared to a composition not comprising the plasticizing system in accordance with the invention. The improvement in adhesion is much greater for the copolymers which are copolymers of ethylene, a 1,3-diene of formula (I) and a second 1,3-diene chosen from 1, 3-butadiene, isoprene or a mixture thereof in accordance with the invention.