Antivibration rubber composition

Abstract

The invention relates to an antivibration rubber article comprising at least one rubber element which comprises a rubber composition based on at least one elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the molar fraction of the ethylene units in the copolymer being within a range extending from more than 50% to 95%; a reinforcing filler; and a crosslinking system comprising a dithiocarbamate and a particular xanthate polysulfide having more than 2 consecutive sulfur atoms.

Description

[0001] ANTI-VIBRATION RUBBER COMPOSITION

[0002] The present invention relates to anti-vibration rubber compositions, as well as to rubber vibration isolation articles comprising such compositions.

[0003] Anti-vibration products, also called vibration dampers, are commonly used, particularly in the automotive sector, but also in any element undergoing or generating vibrations. These products make it possible in particular to reduce vibrations coming from a so-called vibration-generating source of a machine, such as an engine, in order to avoid damaging other elements of the machine or to improve user comfort.

[0004] It is known to use ethylene-propylene-diene monomer (EPDM) copolymers as the main component of anti-vibration articles, due to their ability to reduce vibrations at temperatures above 60°C. Application KR10-2014-0078243 for example describes compositions for anti-vibration articles comprising EPDM, carbon black, a plasticizing oil and a crosslinking system.

[0005] Anti-vibration products made from rubber must have numerous properties. In particular, they must have good ozone resistance in order to limit the appearance of cracks and delay or even prevent the tearing of these products.

[0006] Furthermore, these articles must advantageously have low energy dissipation during normal use of the machine, i.e. at low frequencies (of the order of 1 Hz), in order to limit heating as much as possible and thus increase the service life of the anti-vibration articles. On the other hand, they must advantageously have high energy dissipation at high frequencies (between 20 and 700 Hz) which correspond to vibration peaks, in order to limit as much as possible the vibrations transmitted to the rest of the machine and potentially to the user of the machine, and potentially also in order to reduce the noise pollution perceived by the user.

[0007] Thus, manufacturers are always looking for solutions to increase the lifespan of anti-vibration articles, for example by reducing energy dissipation at low frequencies, while further reducing vibrations at high frequencies. Continuing its research, the Applicant unexpectedly discovered that a particular composition based on a specific highly saturated copolymer makes it possible to solve this technical problem.

[0008] Thus, the subject of the invention is a rubber composition based on at least:

[0009] - an elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the molar fraction of ethylene units in the copolymer being within a range from more than 50% to 95%,

[0010] - a reinforcing charge,

[0011] - a crosslinking system comprising a dithiocarbamate and a xanthate polysulfide of formula (I), in which,

[0012] ° Ri and R2, identical or different, represent a linear, branched or cyclic hydrocarbon group, C1-C20, optionally comprising one or more heteroatoms, Ri and R2 being able to form together a cycle,

[0013] 0 n is strictly greater than 2.

[0014] The invention also relates to an anti-vibration article comprising at least one rubber element which comprises a composition according to the invention.

[0015] I- DEFINITIONS

[0016] The expression "based on" used to define the constituents of a catalytic system or a composition means the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other, at least partially, during the different phases of manufacturing the catalytic system or the composition. In the case of a composition, it can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0017] The term “elastomer matrix” means all the elastomers in the composition, including the copolymer defined below. Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a copolymer are expressed as a molar percentage relative to the total monomer units of the copolymer.

[0018] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts of elastomer present in the rubber composition considered.

[0019] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0020] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated.

[0021] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, i.e. they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0022] Unless otherwise stated, all glass transition temperature “Tg” values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999).

[0023] II- DESCRIPTION OF THE INVENTION

[0024] II- 1 Elastomer matrix

[0025] According to the invention, the elastomer matrix of the composition comprises at least one copolymer containing ethylene units and 1,3-diene units, the molar fraction of ethylene units in the copolymer being in a range from more than 50% to 95%. In the present, the “copolymer containing ethylene units and 1,3-diene units, the molar fraction of ethylene units in the copolymer being in a range from more than 50% to 95%” may be designated by “the copolymer” or by “the copolymer containing ethylene units and 1,3-diene units” for the sake of simplification of wording.

[0026] By "copolymer containing ethylene units and 1,3-diene units" is meant any copolymer comprising, within its structure, at least ethylene units and 1,3-diene units

[0027] 1,3-diene. The copolymer may thus comprise monomer units other than ethylene units and 1,3-diene units. For example, the copolymer may also comprise alpha-olefin units, in particular alpha-olefin units having from 3 to 18 carbon atoms, advantageously having from 3 to 6 carbon atoms. For example, the alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

[0028] As is well known, the expression "ethylene unit" refers to the -(CH2-CH2)- motif resulting from the insertion of ethylene into the elastomer chain.

[0029] As is known, the expression "1,3-diene unit" refers to the units resulting from the insertion of 1,3-diene by a 1,4-addition, a 1,2-addition or a 3,4-addition in the case of isoprene. The 1,3-diene units are those, for example, of a 1,3-diene or a mixture of 1,3-dienes, the 1,3-diene(s) having from 4 to 12 carbon atoms, such as, in particular, 1,3-butadiene and isoprene. Preferably, the 1,3-diene units are 1,3-butadiene units.

[0030] Advantageously, the ethylene units in the copolymer represent between 55% and 90% by mole of the monomer units of the copolymer.

[0031] Advantageously, the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene, preferably a copolymer of ethylene and

[0032] 1,3-butadiene, i.e. the copolymer does not contain units other than ethylene and 1,3-diene, preferably no units other than ethylene and 1,3-butadiene.

[0033] When the copolymer is a copolymer of ethylene and a 1,3-diene, it advantageously contains units of formula (II) and / or (III). The presence of a saturated 6-membered cyclic unit, 1,2-cyclohexanediyl, of formula (II) as a monomeric unit in the copolymer may result from a series of very specific insertions of ethylene and

[0034] 1,3-butadiene in the polymer chain during its growth.

[0035] -CH2-CH(CH=CH2)- (III)

[0036] For example, the copolymer of ethylene and a 1,3-diene may be devoid of units of formula (II). In this case, it preferably contains units of formula (III).

[0037] When the copolymer of ethylene and a 1,3-diene comprises units of formula (II) or units of formula (III) or units of formula (II) and units of formula (III), the molar percentages of the units of formula (II) and units of formula (III) in the copolymer, respectively o and p, preferably satisfy the following equation (eq. 1), more preferably equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer.

[0038] 0 < o+p < 25 (eq. 1)

[0039] 0 < o+p < 20 (eq. 2)

[0040] According to the invention, the copolymer, preferably the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0041] Advantageously, the number-average mass (Mn) of the copolymer, preferably of the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene) is within a range from 100,000 to 300,000 g / mol, preferably from 150,000 to 250,000 g / mol.

[0042] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described in the examples.

[0043] The copolymer can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one 1,3-diene, preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. Mention may be made in this respect of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP I 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant. The copolymer, including when it is random, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 Al, WO 2018020122 Al and WO 2018020123 Al.

[0044] The copolymer may consist of a mixture of copolymers containing ethylene units and diene units which differ from each other in their microstructures and / or in their macrostructures.

[0045] Advantageously, the content of the copolymer containing ethylene units and 1,3-diene units in the composition is within a range from 30 to 100 phr, from 50 to 100 phr, preferably from 80 to 100 phr. The elastomer matrix may advantageously comprise only, as elastomer, the copolymer containing ethylene units and 1,3-diene units. The compositions according to the invention comprising more than 50 phr, preferably more than 80 phr of the copolymer containing ethylene units and 1,3-diene are particularly advantageous for use in anti-vibration articles intended to be subjected to temperatures above 85°C.

[0046] Alternatively, the elastomer matrix may further comprise a diene elastomer different from the copolymer containing ethylene units and 1,3-diene units (also referred to herein as the "other elastomer").

[0047] When the composition comprises another elastomer, the level of the copolymer containing ethylene units and 1,3-diene units in the composition may be in a range from 30 to 90 phr, preferably from 50 to 80 phr, the level of the other elastomer being in a range from 10 to 70 phr, preferably from 20 to 50 phr.

[0048] The other elastomer of the elastomer matrix of the tire according to the invention is preferably chosen from the group of highly unsaturated diene elastomers such as polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers and blends of these elastomers. The term "highly unsaturated diene elastomer" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or patterns of diene origin (conjugated dienes) which is greater than 50% (mol %).

[0049] Preferably, the other elastomer is chosen from the group consisting of polyisoprenes having a molar rate of cis-1,4 bonds greater than 90%. It may be synthetic polyisoprene, natural rubber or one of their mixtures. Preferably, the other elastomer is a natural rubber. II-2 Reinforcing filler

[0050] The rubber composition according to the invention is based on at least one reinforcing filler. Such a reinforcing filler typically consists of nanoparticles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.

[0051] The reinforcing filler may comprise carbon black, silica or a mixture thereof. Advantageously, the reinforcing filler comprises more than 50% by mass, preferably more than 80% by mass, of carbon black. More preferably, the reinforcing filler consists exclusively of carbon black, i.e., the carbon black represents 100% by mass of the reinforcing filler.

[0052] Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772. These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. Carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see, for example, applications WO97 / 36724-A2 or W099 / 16600-A1).

[0053] Among the above-mentioned carbon blacks, those having a BET specific surface area between 10 and 160 m 2 / g, preferably between 10 and 100 m 2 / g, preferably between 20 and 80 m 2 / g, preferably between 20 and 70 m 2 / g, are particularly preferred.

[0054] The BET specific surface area of ​​carbon blacks is measured according to ASTM D6556-10 [multi-point method (minimum 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3],

[0055] Any type of precipitated silica may be suitable, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ® 5000GR”, “Ultrasil ® 7000GR” from the company Evonik, the silicas “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” from Evonik, silica “Zeosil® 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0056] To couple the silica to the diene elastomer, it is possible to use, in a well-known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0057] Preferably, when used, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0058] When a silica-elastomer coupling agent is used, the coupling agent content can easily be adjusted by a person skilled in the art. Typically, the coupling agent content is from 0.5% to 15% by weight relative to the amount of silica.

[0059] The level of reinforcing filler can easily be adjusted by a person skilled in the art depending on the use of the rubber composition. Advantageously, the level of reinforcing filler in the composition is within a range from 15 to 90 phr, preferably from 15 to 70 phr, preferably from 20 to 60 phr.

[0060] Preferably, the carbon black content in the composition is within a range from 15 to 90 phr, preferably from 15 to 70 phr, preferably from 20 to 60 phr, and the composition does not comprise any filler other than carbon black or comprises less than 10 phr, preferably less than 5 phr, more preferably the composition does not comprise any filler other than carbon black.

[0061] When silica is present in the composition, the carbon black content may be in a range from 19 to 69 pce, preferably from 27 to 57 pce, and the silica content in a range from 1 to 35 pce, preferably from 3 to 24 pce.

[0062] II-3 Crosslinking system

[0063] Dithiocarbamate

[0064] The crosslinking system of the composition according to the invention comprises a dithiocarbamate.

[0065] Suitable dithiocarbamates are zinc or copper dithiocarbamates, preferably zinc dithiocarbamates such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc diisopropyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, zinc dihexyldithiocarbamate, zinc diheptyldithiocarbamate, zinc dioctyldithiocarbamate, zinc di(2-ethylhexyl)dithiocarbamate, zinc didecyldithiocarbamate, zinc didodecyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate and mixtures of these compounds.The dithiocarbamate is preferably zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC) or mixtures of these compounds, more preferably zinc dibenzyldithiocarbamate.

[0066] Examples of commercially available dithiocarbamates include zinc dibenzyldithiocarbamate “Perkacit ZBEC” from Performance Additives, zinc dimethyldithiocarbamate Rhenogran ZDMC-80 from Lanxess, and zinc diethyldithiocarbamate “ZDEC” from MLPC International.

[0067] The level of dithiocarbamate in the composition may be in the range of 1 to 20 pce, preferably 2 to 10 pce. Xanthate polysulfide

[0068] The crosslinking system of the composition according to the invention comprises a xanthate polysulfide of formula (I), in which,

[0069] ° Ri and R2, identical or different, represent a linear, branched or cyclic hydrocarbon group, C1-C20, optionally comprising one or more heteroatoms, Ri and R2 being able to form together a cycle,

[0070] 0 n is strictly greater than 2.

[0071] Ri and R2, identical or different, can be saturated or unsaturated. Preferably, they are both saturated.

[0072] When Ri or R2 comprises one or more heteroatoms, it can be an oxygen, nitrogen or sulfur atom.

[0073] Preferably, R1 and R2, identical or different, represent a linear or branched hydrocarbon group, C1-C12, preferably C2-C5, R1 and R2 being able to form together a cycle.

[0074] Preferably, n is between 2 and 8, preferably between 2 and 5. In other words, n is within a range from more than 2 to less than 8, preferably from more than 2 to less than 5.

[0075] The xanthate polysulfide of formula (I) may be selected from the group consisting of dimethyl xanthate polysulfide, diethyl xanthate polysulfide, dipropyl xanthate polysulfide, diisopropyl xanthate polysulfide and dibutyl xanthate polysulfide (DIXP) and mixtures thereof. Preferably the xanthate polysulfide of formula (I) is diisopropyl xanthate polysulfide (DIXP).

[0076] Xanthate polysulfides of formula (I) are commercially available, for example diisopropyl xanthate polysulfide “Robac AS-100” from RobinsonBrothers, bis[(cyclohexyloxy)thioxomethyl] trisulfide from Chemieliva Pharmaceutical Co. LTD or bis(methoxythiocarbonyl)tetrasulfide from Aurora Fine Chemicals.

[0077] The xanthate polysulfide content of formula (I) may be in a range from 1 to 20 pce, preferably from 2 to 10 pce.

[0078] Other crosslinking agents

[0079] The composition according to the invention makes it possible to avoid the presence of a certain number of compounds usually used in crosslinking systems for rubber compositions.

[0080] Thus, the composition advantageously does not comprise organic peroxide, preferably no peroxide, or comprises less than 1 phr, preferably less than 0.5 phr, preferably less than 0.3 phr, preferably less than 0.2 phr and preferably less than 0.1 phr. More preferably, the composition advantageously does not comprise organic peroxide, preferably no peroxide.

[0081] Furthermore, the composition is advantageously free of sulfur as a vulcanizing agent, or contains less than 0.5 phr, preferably less than 0.3 phr, preferably less than 0.2 phr and most preferably less than 0.1 phr. The sulfur may be molecular sulfur or come from a sulfur-donating agent, such as alkyl phenol disulfides (APDS).

[0082] Furthermore, the composition advantageously does not comprise a crosslinking co-agent comprising an acrylate derivative of formula (IV):

[0083] [X]p A (IV) in which: o [X]p corresponds to a radical of formula (V): in which: • R1, R2 and R3 independently represent a hydrogen atom or a C1-C8 hydrocarbon group chosen from the group consisting of linear, branched or cyclic alkyl groups, alkylaryl groups, aryl groups and aralkyls, and optionally interrupted by one or more heteroatoms, R2 and R3 being able to form together a non-aromatic cycle,

[0084] • (*) represents the point of attachment of the radical of formula (V) to A, o A represents an atom belonging to the group consisting of alkaline earth metals or transition metals, a carbon atom, or a C1-C30 hydrocarbon group optionally interrupted and / or substituted by one or more heteroatoms, o A comprising p free valences, p having a value ranging from 2 to 6, o it being understood that the 2 to 6 radicals X are identical or different.

[0085] Preferably, the composition does not comprise a crosslinking co-agent chosen from the group consisting of (meth)acrylate compounds, maleimide compounds, allylic compounds, vinyl compounds and mixtures thereof.

[0086] Furthermore, the composition according to the invention advantageously does not comprise diphenylguanidine.

[0087] II-4 Possible additives

[0088] The compositions according to the invention, intended to be used in anti-vibration articles, may optionally also comprise all or part of the usual additives usually used in elastomer compositions for such articles, such as for example plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical antiozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described for example in application WO 02 / 10269) or even swelling agents.

[0089] The composition according to the invention may comprise zinc 2-mercaptotolylimidazole (ZMTI). The presence of ZMTI is particularly advantageous when the composition is used in an anti-vibration article intended to be used in an environment where the temperature is higher than 60°C. When ZMTI is present, its level in the composition is advantageously in a range from 1 to 20 phr, preferably from 2 to 10 phr.

[0090] II-5 Preparation of rubber compositions

[0091] The compositions usable within the framework of the present invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art:

[0092] - a first phase of working or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a conventional internal mixer (for example of the "Banbury" type), in particular the elastomeric matrix, the reinforcing filler, any other various additives, with the exception of the crosslinking system. The incorporation of the possible filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system. The non-productive phase can be carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes.

[0093] - a second phase of mechanical work (so-called "productive" phase), which can be carried out in an external mixer such as a cylinder mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0094] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0095] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for laboratory characterization, or extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber product that can be used, for example, as anti-vibration panels, anti-vibration strips or isolation pads. The final composition can alternatively be molded and crosslinked using techniques known to those skilled in the art in order to produce mounts and bushes. These products can then be used for the manufacture of anti-vibration articles, using techniques known to those skilled in the art.The composition may be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), may be a semi-finished product which may be used as an anti-vibration article, or in an anti-vibration article, for example associated with a metal part, the whole constituting the anti-vibration article.

[0096] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 100°C and 200°C, under pressure.

[0097] II-6 Anti-vibration articles

[0098] The present invention also relates to an anti-vibration article comprising at least one rubber element which comprises a rubber composition according to the invention.

[0099] The rubber compositions in accordance with the invention find numerous applications in anti-vibration articles or devices, in particular as vibration isolators or dampers.

[0100] For example, the anti-vibration article comprising at least one rubber element according to the invention may be chosen from the group consisting of supports, brackets, bushings, pads, bearings, shock absorber pulleys, pipes, buffers and anti-vibration panels.

[0101] The supports can be, for example, anti-seismic supports, bridge supports. The supports can be supports of any shape, for example, cylindrical supports or conical supports. The bearings can be, for example, ribbed bearings, sandwich bearings or even multi-layer ribbed bearings. The bearings can be central bearings or sliding bearings.

[0102] Preferably, the anti-vibration article comprising at least one rubber element is selected from the group consisting of anti-vibration supports and panels, preferably from the group consisting of anti-vibration supports.

[0103] Advantageously, the rubber composition according to the invention constitutes the rubber element of the anti-vibration article. In other words, the rubber element of the anti-vibration article according to the invention does not comprise any composition other than the rubber composition according to the invention. Thus, preferably, the anti-vibration article according to the invention comprises at least one rubber element made of the rubber composition according to the invention. III- EXAMPLES

[0104] III-l Measures and tests used

[0105] Determination of the microstructure of elastomers:

[0106] The microstructure of ethylene and butadiene copolymers is determined by 1H NMR analysis, supplemented by 13C NMR analysis when the resolution of 1H NMR spectra does not allow the attribution and quantification of all species. Measurements are carried out using a BRUKER 500MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83MHz for carbon observation. For non-soluble elastomers but having the ability to swell in a solvent, a 4mm z-grad HRMAS probe is used to observe the proton and carbon in proton-decoupled mode. Spectra are acquired at rotation speeds of 4000Hz to 5000Hz. For measurements on soluble elastomers, a liquid NMR probe is used to observe the proton and carbon in proton-decoupled mode.The preparation of insoluble samples is done in rotors filled with the analyzed material and a deuterated solvent allowing swelling, generally deuterated chloroform (CDCh). The solvent used must always be deuterated and its chemical nature can be adapted by the skilled person. The quantities of material used are adjusted to obtain spectra with sufficient sensitivity and resolution. The soluble samples are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 mL), generally deuterated chloroform (CDCh). The solvent or solvent blend used must always be deuterated and its chemical nature can be adapted by the skilled person. In both cases (soluble sample or swollen sample). For proton NMR, a single 30° pulse sequence is used. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules.The number of accumulations is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement. For carbon NMR, a single 30° pulse sequence is used with proton decoupling only during acquisition to avoid “Nuclear Overhauser” (NOE) effects and remain quantitative. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules. The number of accumulations is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement. NMR measurements are carried out at 25°C.

[0107] Determination of the macrostructure of polymers by size exclusion chromatography (SEC): a) Principle of measurement:

[0108] Size exclusion chromatography (SEC) separates macromolecules in solution according to their size using columns filled with a porous gel. Macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0109] Combined with 3 detectors (3D), a refractometer, a viscometer and a 90° light scattering detector, SEC allows us to understand the absolute molar mass distribution of a polymer. The different number-average (Mn), weight-average (Mw) absolute molar masses and the dispersity (D = Mw / Mn) can also be calculated. b) Preparation of the polymer:

[0110] Each sample is solubilized in tetrahydrofuran at a concentration of approximately 1 g / L. The solution is then filtered through a 0.45 pm porosity filter before injection. c) 3D SEC analysis:

[0111] To determine the number-average molar mass (Mn), and where appropriate the weight-average molar mass (Mw) and the polydispersity index (Ip) of polymers, the method below is used.

[0112] The number-average molar mass (Mn), weight-average molar mass (Mw) and polydispersity index of the polymer (hereinafter referred to as sample) are determined absolutely by triple detection size exclusion chromatography (SEC). Triple detection size exclusion chromatography has the advantage of measuring average molar masses directly without calibration.

[0113] The refractive index increment dn / dc value of the sample solution is measured online using the peak area detected by the refractometer (RI) of the liquid chromatography equipment. To apply this method, it must be ensured that 100% of the sample mass is injected and eluted through the column. The RI peak area depends on the sample concentration, the RI detector constant and the dn / dc value.

[0114] To determine the average molar masses, the previously prepared and filtered lg / l solution is used and injected into the chromatographic system. The equipment used is a "WATERS alliance" chromatographic chain. The elution solvent is tetrahydrofuran containing 250 ppm of BHT (2,6-diter-butyl 4-hydroxy toluene), the flow rate is 1 mL.min' 1, the system temperature of 35°C and the analysis time of 60 min. The columns used are a set of three AGILENT columns with the trade name “PL GEL MIXED B LS”. The injected volume of the sample solution is 100 pL. The detection system is composed of a Wyatt differential viscometer with the trade name “VISCOSTAR II”, a Wyatt differential refractometer with the trade name “OPTILAB T-REX” with a wavelength of 658 nm, a Wyatt multi-angle static light scattering detector with a wavelength of 658 nm and the trade name “DAWN HELEOS 8+”.

[0115] For the calculation of the number-average molar masses and the polydispersity index, the value of the refractive index increment dn / dc of the sample solution obtained above is integrated. The software for processing the chromatographic data is the “ASTRA de Wyatt” system.

[0116] Energy dissipation:

[0117] Rubber compositions were tested in double shear according to ASTM D5992-96 (2011). A double shear specimen consists of two elastomer discs bonded between three cylindrical metal reinforcements. The bonded discs have a diameter of 8.62 mm (die diameter).

[0118] The conditions retained for the dynamic amplitude sweep test are as follows:

[0119] - Test equipment: Metravib DMA + 450 viscoanalyzer,

[0120] - Type of stress: simple shear,

[0121] - Sample holder type: double shear mount; 3.5 mm air gap,

[0122] - Temperature range: ambient (23±2°C) or 100±2°C,

[0123] - Thermal conditioning: none,

[0124] - Load frequency: 1 Hz or 95 Hz

[0125] - Regulated static quantity: none,

[0126] - Regulated dynamic quantity: deformation amplitude from ± 0.1% up to ± 50% (round trip)

[0127] - Glued discs with a diameter of 8.62 mm and a thickness of 2 mm.

[0128] The tan(ô) loss factors are the maximum values ​​recorded on the forward / return deformation curve on new specimens at two frequencies, namely 1 Hz and 95 Hz respectively. For each of these frequencies, measurements were carried out at 23°C and 100°C to be representative of the operating temperatures of the anti-vibration article, for example at 23°C for anti-vibration pads used to attenuate the vibrations of a washing machine, and at 100°C for anti-vibration blocks placed on a heat-generating motor.

[0129] The lower the loss factor tan(ô) at 1 Hz, in absolute value, the better the composition in that it is less dissipative (hysteretic) at the normal operating point of the machine whose vibrations are to be attenuated. The performance of the loss factor tan(ô) 1Hz is calculated according to the formula: (Loss factor tan(ô) 1Hz control) / (Loss factor tan(ô) 1Hz mixture)* 100. A value greater than 100 indicates less dissipation of the mixture and therefore better operation at lower continuous temperatures.

[0130] The higher the loss factor tan(ô) at 95 Hz, the better the composition in that it is more dissipative and therefore helps to attenuate vibrations when the machine resonates with its motor.

[0131] The damping coefficient corresponds to the loss factor tan(ô) at 95 Hz divided by the loss factor tan(ô) at 1 Hz.

[0132] The damping coefficient performance is calculated using the formula: (damping coefficient of the tested mixture) / (damping coefficient of the control)*100. A value greater than 100 indicates a better capacity of the tested composition to be low-dissipative during normal machine operation while improving vibration damping when higher frequencies occur.

[0133] III-2 Preparation of compositions

[0134] In the following examples, the rubber compositions were produced as described in point II-5 above. In particular, the “non-productive” phase was carried out in a 2.5 liter mixer for 3.5 minutes, for an average paddle speed of 50 revolutions per minute until a maximum drop temperature of 160°C was reached. The “productive” phase was carried out in a cylinder tool at 23°C for 5 minutes.

[0135] The crosslinking of the composition was carried out at a temperature of 170°C at t99, under pressure.

[0136] III-3 Rubber composition tests

[0137] The examples presented below aim to compare the performances of loss factor tan(ô) at 1 Hz and the damping coefficients at 23°C and 100°C of three compositions in accordance with the present invention (13, 14 and 15) and of two control compositions not in accordance with the invention (C1, C2) with five control compositions not in accordance with the invention (T1 to T5).

[0138] Compositions C1, C2, 13, 14 and 15 differ respectively from compositions T1 to T5 only by the nature of the copolymer. Compositions C1, C2, 13, 14 and 15 differ from each other by the nature of the crosslinking system used. The pce rates of compound (11) of formulation T2 and C2 were adjusted to iso-mole of compound (10) of composition TL. The rates of compounds (10), (11) and (12) of composition T3 and 13 were adjusted so that their sum was iso-mole of compound (10) of composition T1.

[0139] Table 1 shows the tested compositions (in pce), as well as the results obtained. Compositions Cl and Tl did not crosslink, so it was not possible to carry out tests on these compositions.

[0140] The results obtained for compositions Cl, C2, 13, 14 and 15 are expressed as a percentage base 100 relative to the control composition Tl, T2, T3, T4 and T5 respectively.

[0141] [Table 1]

[0142] (1) EPDM “Keltan 3960Q” from Lanxess

[0143] (2) Ethylene-butadiene copolymer with 80 mol% of ethylenic units prepared according to a process for the polymerization of ethylene and butadiene in accordance with example 4-2 of patent EP 1 954 705 B 1 in the name of the Applicants, the polymerization time being adjusted so as to obtain a molar mass Mn = 153,000 g / mol with a polydispersity index equal to 1.9

[0144] (3) Carbon black grade N550 according to ASTM D-1765 (4) Industrial grade zinc oxide from Umicore

[0145] (5) stearic acid “Pristerene 4931” from Uniqema company

[0146] (6) 2,2,4-trimethyl-l,2-dihydroquinoline “Pilnox TMQ” from Nocil

[0147] (7) Nl,3-dimethylbutyl-N-phenylparaphenylenediamine “Santoflex 6-PPD” from Flexsys

[0148] (8) Antioxidant wax “Cera SER AO 32” from the company SER Wax Industry

[0149] (9) Zinc diacrylate (ZD A) “Dymalink SR633” from Cray Valley Company

[0150] (10) Zinc dibenzyldithiocarbamate “Perkacit ZBEC” from Performance Additives

[0151] (11) Dipropyl xanthate polysulfide “Robac AS-100” from RobinsonBrothers

[0152] (12) Zinc methylmercaptobenzimidazole “Vanox ZMTI” from Vanderbilt Chemicals

[0153] The results presented in Table 1 above show that only the compositions in accordance with the invention, i.e. those comprising both a copolymer containing ethylene units and 1,3-diene units, the molar fraction of the ethylene units in the copolymer being in a range from more than 50% to 95%, a dithiocarbamate and a xanthate polysulfide of formula (I), make it possible to improve the damping coefficients at 23°C compared to compositions comprising EPDM. The compositions in accordance with the invention also make it possible to improve the damping coefficients at 100°C when they contain ZMTI, which allows their use in a wider range of applications. Thus, the compositions in accordance with the invention have a better service life, due to their lower continuous heating while maintaining an excellent level of reduction of vibrations at high frequencies.

Claims

CLAIMS 1. Rubber composition based on at least: - an elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the molar fraction of ethylene units in the copolymer being within a range from more than 50% to 95%, - a reinforcing charge, - a crosslinking system comprising a dithiocarbamate and a xanthate polysulfide of formula (I), in which, Ri and R2, identical or different, represent a linear, branched or cyclic hydrocarbon group, C1-C20, optionally comprising one or more heteroatoms, Ri and R2 being able to form together a cycle, n is strictly greater than 2.

2. A rubber composition according to claim 1, wherein the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene.

3. A rubber composition according to any preceding claim, wherein the 1,3-diene units are 1,3-butadiene units.

4. Rubber composition according to any one of the preceding claims, in which the content of the copolymer containing ethylene units and 1,3-diene units is within a range from 30 to 100 phr, preferably from 50 to 100 phr.

5. Rubber composition according to any one of the preceding claims, in which the level of reinforcing filler is in a range from 15 to 90 phr, preferably in a range from 20 to 60 phr.

6. A rubber composition according to any one of the preceding claims, wherein in the xanthate polysulfide of formula (I): Ri and R2, identical or different, represent a linear or branched hydrocarbon group, C1-C12, preferably C2-C5, Ri and R2 being able to form together a cycle, n is between 2 and 8, preferably between 2 and 5.

7. A rubber composition according to any one of the preceding claims, wherein the xanthate polysulfide of formula (I) is selected from the group consisting of dimethyl xanthate polysulfide, diethyl xanthate polysulfide, dipropyl xanthate polysulfide, diisopropyl xanthate polysulfide and dibutyl xanthate polysulfide and mixtures thereof, preferably wherein the xanthate polysulfide of formula (I) is diisopropyl xanthate polysulfide.

8. Rubber composition according to any one of the preceding claims, in which the xanthate polysulfide content of formula (I) is within a range from 1 to 20 phr, preferably from 2 to 10 phr.

9. Rubber composition according to any one of the preceding claims, in which the dithiocarbamate is a zinc dithiocarbamate, preferably zinc dibenzyldithiocarbamate.

10. Rubber composition according to any one of the preceding claims, in which the level of dithiocarbamate is within a range from 1 to 20 phr, preferably from 2 to 10 phr.

11. Rubber composition according to any one of the preceding claims, comprising zinc 2-mercaptotolylimidazole at a level in a range from 1 to 20 phr, preferably from 2 to 10 phr.

12. A rubber composition according to any one of the preceding claims, not comprising organic peroxide, preferably no peroxide, or comprising less than 1 phr, preferably less than 0.5 phr, preferably less than 0.3 phr.

13. A rubber composition according to any preceding claim, not comprising sulfur as a vulcanizing agent, or containing less than 0.5 phr, preferably less than 0.3 phr.

14. Rubber composition according to any one of the preceding claims, not comprising a crosslinking co-agent comprising an acrylate derivative of formula (IV): [X]p A (IV) in which: o [X]p corresponds to a radical of formula (V): • R1, R2 and R3 independently represent a hydrogen atom or a C1-C8 hydrocarbon group chosen from the group consisting of linear, branched or cyclic alkyl groups, alkylaryl groups, aryl groups and aralkyls, and optionally interrupted by one or more heteroatoms, R2 and R3 being able to form together a non-aromatic cycle, • (*) represents the point of attachment of the radical of formula (V) to A, o A represents an atom belonging to the group consisting of alkaline earth metals or transition metals, a carbon atom, or a C1-C30 hydrocarbon group optionally interrupted and / or substituted by one or more heteroatoms, o A comprising p free valences, p having a value ranging from 2 to 6, o it being understood that the 2 to 6 radicals X are identical or different.

15. An anti-vibration article comprising at least one rubber element which comprises a rubber composition according to any one of claims 1 to 14, said article preferably being selected from the group consisting of supports, brackets, bushings, pads, bearings, shock absorber pulleys, hoses, buffers and anti-vibration panels, preferably from the group consisting of anti-vibration mounts.

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