ELASTOMER LAMINATE

Abstract

An elastomeric laminate comprises at least two adjacent cohesive layers, the first layer consisting of a composition based on 10 to 100 phr of a copolymer of ethylene and of a 1,3-diene of formula CH.sub.2═CR—CH═CH.sub.2, the ethylene units in the copolymer representing more than 50 mol % of the monomer units of the copolymer, the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms, from 0 to 90 phr of a diene elastomer having a content by weight of diene unit of greater than 50%, and a crosslinking system; the second layer consisting of a composition based on a diene elastomer having a content by weight of diene unit of greater than 50% and a crosslinking system. Also disclosed is a tire, in particular a tire provided with a sidewall, comprising this composition.

Claims

1.-15. (canceled)

16. An elastomeric laminate comprising at least two adjacent layers: a first layer consisting of a composition based on 10 to 100 phr of a copolymer of ethylene and of a 1,3-diene of formula (I), the ethylene units in the copolymer representing more than 50 mol % of the monomer units of the copolymer,
CH.sub.2═CR—CH═CH.sub.2  (I), the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms, from 0 to 90 phr of a diene elastomer having a content by weight of diene unit of greater than 50%, and a crosslinking system; and a second layer consisting of a composition based on a diene elastomer having a content by weight of diene unit of greater than 50% and a crosslinking system.

17. The elastomeric laminate according to claim 16, wherein the copolymer of the first layer contains ethylene units which represent between 50 mol % and 95 mol % of the monomer units of the copolymer.

18. The elastomeric laminate according to claim 16, wherein the 1,3-diene of the copolymer of the first layer is myrcene or β-farnesene.

19. The elastomeric laminate according to claim 16, wherein a content of the copolymer of ethylene and of a 1,3-diene of formula (I) in the composition of the first layer is within a range extending from 15 to 90 phr.

20. The elastomeric laminate according to claim 16, wherein the diene elastomer having a content by weight of diene unit of greater than 50% is present in the composition of the first layer at a content within a range extending from 10 to 85 phr.

21. The elastomeric laminate according to claim 16, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the 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.

22. The elastomeric laminate according to claim 16, wherein the composition of the first layer comprises from 20 to 80 phr of reinforcing filler.

23. The elastomeric laminate according to claim 16, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the 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.

24. The elastomeric laminate according to claim 16, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the first layer and the diene elastomer having a content by weight of diene unit of greater than 50% of the second layer are polyisoprenes.

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

26. The elastomeric laminate according to claim 16, wherein the composition of the second layer comprises from 20 phr to 80 phr of reinforcing filler.

27. The elastomeric laminate according to claim 16, wherein the first layer has a thickness within a range extending from 0.2 to 120 mm.

28. A tire comprising the elastomeric laminate according to claim 16.

29. The tire according to claim 28, wherein the first layer of the elastomeric laminate constitutes a portion or all of the tire tread and the second layer of the laminate constitutes a portion or all of a tread underlayer.

30. The tire according to claim 28, wherein the first layer of the laminate constitutes a portion or all of at least one sidewall of the tire and the second layer of the laminate constitutes a portion or all of a carcass ply.

Description

III—PREFERRED EMBODIMENTS

[0128] In the light of the above, the preferred embodiments of the invention are described below: [0129] A. Elastomeric laminate comprising at least two adjacent layers: [0130] the first layer consisting: [0131] of a composition based on 10 to 100 phr of a copolymer of ethylene and of a 1,3-diene of formula (I), the ethylene units in the copolymer representing more than 50 mol % of the monomer units of the copolymer,

CH.sub.2═CR—CH═CH.sub.2  (I) [0132] the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms; from 0 to 90 phr of a diene elastomer having a content by weight of diene unit of greater than 50%; and [0133] a crosslinking system, [0134] the second layer consisting of a composition based on a diene elastomer having a content by weight of diene unit of greater than 50% and a crosslinking system. [0135] B. Laminate according to embodiment A, wherein the copolymer of the first layer contains ethylene units which represent between 50 mol % and 95 mol %, preferably between 60 mol % and 90 mol %, more preferably between 70 mol % and 85 mol %, of the monomer units of the copolymer. [0136] C. Laminate according to any one of the preceding embodiments, wherein the copolymer of the first layer contains units of the 1,3-diene of 1,2 or 3,4 configuration which represent more than 50 mol % of the units of the 1,3-diene. [0137] D. Laminate according to any one of the preceding embodiments, wherein the symbol R of the copolymer of the first layer represents a hydrocarbon chain having 6 to 16 carbon atoms. [0138] E. Laminate according to any one of the preceding embodiments, wherein the symbol R of the copolymer of the first layer represents an aliphatic chain. [0139] F. Laminate according to any one of the preceding embodiments, wherein the symbol R of the copolymer of the first layer represents an acyclic chain. [0140] G. Laminate according to any of the preceding embodiments, wherein the symbol R of the copolymer of the first layer represents a linear or branched chain. [0141] H. Laminate according to any one of the preceding embodiments, wherein the 1,3-diene of the copolymer of the first layer is myrcene or β-farnesene. [0142] I. Laminate according to any one of the preceding embodiments, wherein the copolymer of the first layer has a glass transition temperature below −35° C., preferably between −90° C. and −35° C. [0143] J. Laminate according to any one of the preceding embodiments, wherein the content of the copolymer of ethylene and of a 1,3-diene of formula (I) in the composition of the first layer is within a range extending from from 15 to 90 phr, preferably from 20 to 80 phr, more preferably from 30 to 80 phr. [0144] K. Laminate according to any one of the preceding embodiments, wherein the diene elastomer having a content by weight of diene unit of greater than 50% is present in the composition of the first layer at a content within a range extending from 10 to 85 phr, preferably 20 to 80 phr, more preferably 20 to 70 phr. [0145] L. Laminate according to any one of the preceding embodiments, wherein the composition of the first layer does not comprise any elastomer other than the copolymer of ethylene and of a 1,3-diene of formula (I) and the diene elastomer having a content by weight of diene unit of greater than 50%. [0146] M. Laminate according to any one of the preceding embodiments, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the 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 the mixtures of these elastomers. [0147] N. Laminate according to any one of the preceding embodiments, wherein the diene elastomer having a content by weight of diene units of greater than 50% of the composition of the first layer is a polyisoprene, preferably comprising a content by weight of 1,4-cis bonds of at least 90%, preferably at least 98%, of the weight of the polyisoprene. [0148] O. Laminate according to embodiment N, wherein the polyisoprene of the composition of the first layer is selected from the group consisting of natural rubber, synthetic polyisoprenes or mixtures thereof. [0149] P. Laminate according to any one of the preceding embodiments, wherein the composition of the first layer comprises a reinforcing filler. [0150] Q. Laminate according to embodiment P, wherein the reinforcing filler of the composition of the first layer consists mainly, preferably exclusively, of carbon black. [0151] R. Laminate according to embodiment P, wherein the reinforcing filler of the composition of the first layer consists mainly of silica. [0152] S. Laminate according to any one of embodiments P to R, wherein the content of reinforcing filler in the composition of the first layer is within a range extending from 20 to 80 phr, preferably from 25 to 70 phr, preferably from 30 to 60 phr. [0153] T. Laminate according to any one of embodiments P to S, wherein the volume fraction of reinforcing filler in the composition of the first layer is within a range extending from 8% to 17%. [0154] U. Laminate according to any one of the preceding embodiments, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the 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 the mixtures of these elastomers. [0155] V Laminate according to embodiment T or U, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the composition of the second layer is a polyisoprene, preferably comprising a content by weight of 1,4-cis bonds of at least 90%, preferably at least 98%, of the weight of the polyisoprene. [0156] W. Laminate according to embodiment V, wherein the polyisoprene of the composition of the second layer is selected from the group consisting of natural rubber, synthetic polyisoprenes or mixtures thereof. [0157] X. Laminate according to any one of the preceding embodiments, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the first layer and the diene elastomer having a content by weight of diene unit of greater than 50% of the second layer are polyisoprenes. [0158] Y Laminate according to any one of embodiments A to W, wherein the diene elastomer having a content by weight of diene unit of greater than 50% of the first layer and the diene elastomer having a content by weight of diene unit of greater than 50% of the second layer are polyisoprenes comprising a content by weight of 1,4-cis bonds of at least 90%, preferably of at least 98%, of the weight of the polyisoprene. [0159] Z. Laminate according to any one of the preceding embodiments, wherein the composition of the second layer comprises a reinforcing filler. [0160] AA. Laminate according to embodiment Z, wherein the reinforcing filler of the composition of the second layer consists mainly, preferably exclusively, of carbon black. [0161] BB. Laminate according to embodiment Z, wherein the reinforcing filler of the composition of the second layer consists mainly of silica. [0162] CC. Laminate according to any one of embodiments Z to BB, wherein the content of reinforcing filler in the composition of the second layer is within a range extending from 20 phr to 80 phr, preferably from 25 to 70 phr, preferably from 30 to 60 phr. [0163] DD. Laminate according to any one of the preceding embodiments, wherein the first layer has a thickness within a range extending from 0.5 to 120 mm, preferably from 1 to 15 mm. [0164] EE. Laminate according to any one of embodiments A to CC, wherein the first layer has a thickness within a range extending from 0.2 to 10 mm, preferably from 0.3 to 5 mm. [0165] FF. Laminate according to any one of the preceding embodiments, wherein the second layer has a thickness within a range extending from 0.2 to 10 mm, preferably from 0.3 to 5 mm. [0166] GG. Tyre comprising a laminate defined in any one of the embodiments A to FF. [0167] HH. Tyre according to embodiment GG, wherein the first layer of the laminate constitutes a portion or all of the tyre tread and the second layer of the laminate constitutes a portion or all of a tread underlayer. [0168] II. Tyre according to embodiment GG, wherein the first layer of the laminate constitutes a portion or all of at least one sidewall of the tyre and the second layer of the laminate constitutes a portion or all of a carcass ply.

IV—EXAMPLES

[0169] Iv-1 Measurements and Tests Used

[0170] IV-1.1 Determination of the Microstructure of the Elastomers:

[0171] The spectral characterization and the measurements of the microstructure of the copolymers of ethylene and of 1,3-myrcene are carried out by nuclear magnetic resonance (NMR) spectroscopy.

[0172] Spectrometer: For these measurements, a Bruker Avance III HD 400 MHz spectrometer is used, equipped with a Bruker cryo-BBFO z-grad 5 mm probe.

[0173] 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.

[0174] Preparation of the sample: 25 mg of sample are dissolved in 1 ml of deuterated chloroform (CDCl.sub.3).

[0175] 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 δ.sub.1H=7.2 ppm and δ.sub.13C=77 ppm.

[0176] 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.

[0177] The integrated signals for the quantification of the various moieties are:

[0178] Ethylene: signal at 1.2 ppm corresponding to 4 protons

[0179] Total myrcene: signal No. 1 (1.59 ppm) corresponding to 6 protons

[0180] Form A: signal No. 7 (4.67 ppm) corresponding to 2 protons

[0181] Form B: signal No. 8′ (5.54 ppm) corresponding to 1 proton.

[0182] 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/Σ(.sup.1H integrals of each moiety).

TABLE-US-00001 TABLE 1 Assignment of the .sup.1H and .sup.13C signals of Ethylene-Myrcene copolymers δ.sub.1H δ.sub.13C (ppm) (ppm) Group 5.54 146.4 8′ 5.07 124.6 3 + 8″ 4.97-4.79 112.0 9′ 4.67 108.5 7  2.06 26.5 4  2.0-1.79 31.8 5 + 5′ + 5″ 44.5 8  1.59 25.9 and 7.0 1  1.2  36.8-24.0 CH.sub.2 ethylene

##STR00003##

[0183] IV-1.2 Determination of the Glass Transition Temperature of the Polymers:

[0184] The glass transition temperature is measured by means of a differential calorimeter (differential scanning calorimeter) according to Standard ASTM D3418 (1999).

[0185] IV-2 Synthesis of the Polymers:

[0186] In the synthesis of copolymers in accordance with the invention, the 1,3-diene used is myrcene, a 1,3-diene of formula (I) in which R is a hydrocarbon group having 6 carbon atoms: CH.sub.2—CH.sub.2—CH═CMe.sub.2.

[0187] All the reagents are obtained commercially, except the metallocenes. [{Me.sub.2SiFlu.sub.2Nd(μ-BH.sub.4).sub.2Li(THF)}] is prepared according to the procedure described in patent application WO 2007/054224.

[0188] The butyloctylmagnesium BOMAG (20% in heptane, C=0.88 mol.l.sup.−1) originates from Chemtura and is stored in a Schlenk tube under an inert atmosphere. The ethylene, of N35 grade, originates from Air Liquide and is used without prepurification. The myrcene (purity ≥95%) is obtained from Sigma-Aldrich.

[0189] IV-2.1—Copolymer of Ethylene and of 1,3-Butadiene: Elastomer E1

[0190] To a reactor containing, at 80° C., methylcyclohexane, ethylene (Et) and butadiene (Bd) in the proportions indicated in Table 2, butyloctylmagnesium (BOMAG) is added to neutralize the impurities in the reactor, then the catalytic system is added (see Table 2). 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 in the proportions defined in Table 2. The polymerization reaction is halted 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(μ-BH.sub.4).sub.2Li(THF)], a co-catalyst, butyloctylmagnesium (BOMAG), and a preformation monomer, 1,3-butadiene, in the contents indicated in Table 2. It is prepared according to a preparation method in accordance with paragraph II.1 of patent application WO 2017/093654.

[0191] IV-2.2—Copolymer of Ethylene and of Myrcene: Elastomer E2

[0192] To a reactor containing, at 80° C., methylcyclohexane, ethylene and myrcene (My) in the proportions indicated in Table 2, butyloctylmagnesium (BOMAG) is added to neutralize the impurities in the reactor, then the catalytic system is added (see Table 2). 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 myrcene in the proportions defined in Table 2. The polymerization reaction is halted 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(μ-BH.sub.4).sub.2Li(THF)], a co-catalyst, butyloctylmagnesium (BOMAG), and a preformation monomer, 1,3-butadiene, in the contents indicated in Table 2. It is prepared according to a preparation method in accordance with paragraph II.1 of patent application WO 2017/093654.

[0193] The microstructure of the polymers and the properties thereof are shown in Tables 3 and 4.

TABLE-US-00002 TABLE 2 Synthesis E1 E2 Metallocene concentration 0.07 0.039 (mmol/l) Alkylant agent concentration 0.36 0.2 (mmol/l) Preformation monomer/Nd 90 90 metal molar ratio Composition of the feed 80/20 — (mol % Et/Bd) Composition of the feed — 65/35 (mol % Et/My)

TABLE-US-00003 TABLE 3 Elastomer E1 E2 Et (mol %) 78 76 Bd (mol %) 14 1,2-Cyclohexanediyl (mol %)  8 My (mol %) — 24 1,4 Myrcene (mol %/mol % My) — 29 1,2 Myrcene (mol %/mol % My) —  4 3,4 Myrcene (mol %/mol % My) — 67

TABLE-US-00004 TABLE 4 Tg Elastomer (° C.) E1 −40 E2 −63

[0194] IV-3 Preparation of the Rubber Compositions:

[0195] 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.

[0196] IV-4 Rubber Tests:

[0197] The adhesion of several rubber compositions comprising a mixture of natural rubber and copolymer of ethylene and of 1,3-diene on a composition based on natural rubber was compared according to the nature and the content of the copolymer of ethylene and of 1,3-diene.

[0198] The adhesion measurements were carried out using a T-type peel test, also referred to as 180° peeling. The peeling 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 traction. 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 brand 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 standardized relative to a control (base 100). An index of greater than 100 indicates a greater improvement in adhesion.

[0199] The adhesion of compositions C1 to C6, in accordance with the invention, was compared with controls T1 to T6 not in accordance with the invention which differ respectively from compositions C1 to C6 only by the nature of the 1,3-diene: 1,3 diene of formula (I) for compositions C1 to C6 and 1,3-butadiene for compositions T1 to T6 (the elastomers E1 and E2 were prepared according to the process described in point IV.2 above).

[0200] The layer based on natural rubber on which the adhesion was tested corresponds to a composition conventionally used in the inner layer of a tyre, such as a carcass ply or a tread underlayer, comprising 100 phr of natural rubber.

[0201] The compositions tested (in phr), as well as the results obtained, are presented in Table 5.

TABLE-US-00005 TABLE 5 Compositions T1 C1 T2 C2 T3 C3 T4 C4 T5 C5 T6 C6 NR(1) 60 60 80 80 20 20 40 40 60 60 80 80 Elastomer E1 40 — 20 — 80 — 60 — 40 — 20 — Elastomer E2 — 40 — 20 — 80 — 60 — 40 — 20 N234(2) 40 40 40 40 — — — — — — — — Silica(3) — — — — 48 48 48 48 48 48 48 48 Coupling — — — — 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 agent(4) DPG(5) — — — — 1 1 1 1 1 1 1 1 Antioxidant(6) 2 2 2 2 2 2 2 2 2 2 2 2 Anti-ozone 1 1 1 1 1 1 1 1 1 1 1 1 wax(7) 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 ZnO(8) 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(9) 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Sulfur 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Adhesion 100 263 100 142 100 152 100 164 100 206 100 109 (1)NR: Natural rubber (2)Carbon black N234 according to Standard ASTM D-1765-2017 (3)Silica, Zeosil 1165MP, sold by Solvay (4)Liquid silane triethoxysilylpropyltetrasulfide (TESPT) Si69 from Evonik (5)Diphenylguanidine, Perkacit DPG from Flexsys (6)N-(1,3-Dimethylbutyl)-N-phenyl-para-phenylenediamine Santoflex 6-PPD from Flexsys (7)Anti-ozone wax, Varazon 4959 from Sasol Wax (8)Zinc oxide, industrial grade from Umicore (9)N-Cyclohexyl-2-benzothiazolesulphenamide Santocure CBS from Flexsys

[0202] These results show that the use of a rubber composition in accordance with the invention comprising a copolymer of ethylene and of 1,3-diene of formula (I) makes it possible to improve the adhesion on a diene composition compared to a rubber composition not in accordance with the invention comprising a copolymer of ethylene and of 1,3-diene, this being regardless of the nature of the reinforcing filler.