FR3143032A1 - COMPOSITE FOR RUBBER ARTICLE - Google Patents

Abstract

The invention relates to a composite comprising at least one reinforcing element embedded in a rubber composition, the rubber composition being based on at least one isoprene elastomer, at most 50 phr of a copolymer of ethylene and a 1,3-diene, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer, at least 30 phr of a reinforcing inorganic filler, and a crosslinking system.

Description

COMPOSITE FOR RUBBER ARTICLE Technical field of the invention

The present invention relates to the field of reinforced rubber compositions, and more particularly to plies comprising metal or textile reinforcements embedded in a rubber composition, these plies being intended to be used in particular in vehicle tires, conveyor belts or belts.

Prior art

The performance of a vehicle tire, whether pneumatic, i.e. capable of supporting the load of the vehicle by means of a pressurized gas, or non-pneumatic, i.e. capable of supporting the load of the vehicle without the means of a pressurized gas, for example by means of stays, a conveyor belt or a belt, is partly linked to the rigidity of some of their constituents. Indeed, resistance to deformation is an important characteristic making it possible to respond to the stresses to which these objects are subjected.

This need for rigidity is particularly essential in the calendered plies of the crown plies or in the low zones, which are the zones close to the rim, of a vehicle tire. In addition to rigidity, the mixtures concerned must meet a broader specification including low hysteresis, adhesion with the reinforcement, the lowest possible scalability in the raw state (i.e. before crosslinking of the rubber composition) and in the cured state (after crosslinking).

• L’augmentation du taux de charge renforçante (noir ou silice),
• L’utilisation de résines thermodurcissantes qui constituent un réseau secondaire interpénétré avec le réseau charge-élastomère-vulcanisation.

The required rigidity levels can be achieved by two main levers:

• Increasing the rate of reinforcing filler (black or silica),
• The use of thermosetting resins which constitute a secondary network interpenetrated with the filler-elastomer-vulcanization network.

However, increasing the reinforcing filler rate can lead to an increase in hysteresis and a deterioration in the processability of raw mixes, particularly due to the increase in raw stiffness and the possible appearance of a decohesion phenomenon. Furthermore, the use of thermosetting resins can constitute an additional source of dissipation that can penalize hysteretic performance. In addition, some resin-hardener systems used in tires are known to release formaldehyde and must therefore be handled with special measures.

Other avenues have been explored to increase the stiffness of compositions. For example, document WO2014/114607 teaches the use of a highly saturated diene elastomer to increase the stiffness of rubber compositions without degrading the hysteretic properties. Since these compositions are mainly intended to be used in the treads of tires, this document does not address the issues of adhesion or the resistance to cracking of such compositions. However, the presence of reinforcing elements, and therefore of interfaces between elements of mechanical rigidity and very different behaviors (the reinforcing element and the rubber composition), can cause phenomena that are difficult to predict, particularly with regard to the properties of crack propagation, energy dissipation or adhesion.

Document WO2020/074806 teaches the use of a blend of natural rubber and a copolymer of ethylene and a 1,3-diene with a carbon black to obtain good cohesion and ozone resistance properties, which are sought after when used in the sidewalls of vehicle tires.

Continuing its research, the applicant discovered that a composite comprising at least one reinforcing element embedded in a rubber composition, the rubber composition being based on at least one isoprene elastomer, at most 50 pce of a copolymer of ethylene and a 1,3-diene, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer, at least 30 pce of an inorganic reinforcing filler, and a crosslinking system allowed a very good expression of the stiffness/hysteresis compromise without penalizing the other performances expected for a composition used in a sheet, in particular adhesion and resistance to cracking.

Detailed description of the invention

The invention relates to a composite comprising at least one reinforcing element embedded in a rubber composition, the rubber composition being based on at least one isoprene elastomer, at most 50 pce of a copolymer of ethylene and a 1,3-diene, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer, at least 30 pce of a reinforcing inorganic filler, and a crosslinking system.

Preferably, the rubber composition comprises a metal oxide and a stearic acid derivative, the ratio of the content of metal oxide and stearic acid derivative, in pce, being greater than 2.

Preferably, the rubber composition comprises less than 10 pce, preferably less than 5 pce of plasticizer.

Preferably, the copolymer of ethylene and a 1,3-diene comprises at least 60 mol% of ethylene units, preferably at least 65 mol% of ethylene units, more preferably at least 70 mol% of ethylene units.

Preferably, the 1,3-diene units of the copolymer of ethylene and a 1,3-diene are those of a 1,3-diene having 4 to 12 carbon atoms, preferably those of 1,3-butadiene, isoprene, 1,3-pentadiene, an aryl-1,3-butadiene and a mixture of these units.

Preferably, the reinforcing inorganic filler of the rubber composition is silica.

Preferably, the rubber composition comprises from 30 to 150 pce of silica.

Preferably, the rubber composition does not comprise carbon black, or comprises less than 10 pce, preferably less than 5 pce.

Preferably, the reinforcing element comprises a textile or metal wire element.

Preferably, the metal wire element is an elementary metal monofilament or an assembly of several elementary metal monofilaments.

Preferably, the reinforcing element comprises a textile wire element made of a thermoplastic or non-thermoplastic polymeric material.

The invention also relates to a vehicle tire comprising a composite according to the invention.

Definitions

The carbon-containing 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. This includes in particular polymers, plasticizers, fillers, etc.

Any range of values designated by the expression "between a and b" represents the range of values greater than "a" and less than "b" (i.e. excluding the limits a and b) while any range 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). The abbreviation "pce" means parts by weight per hundred parts of elastomer (of the total of elastomers if several elastomers are present).

By the expression "based on" composition, it is meant in the present description a composition comprising the mixture and/or the in situ reaction product of the different constituents used, some of these basic constituents (for example the elastomer, the filler or the constituents of the vulcanization system or other additive conventionally used in a rubber composition intended for the manufacture of tires) being capable of, or intended to react with each other, at least in part, during the different phases of manufacture of the composition intended for the manufacture of tires for vehicles.

In the present application, the term "all the monomer units of the elastomer" or "all the monomer units of the elastomer" means all the repeating units constituting the elastomer which result from the insertion of the monomers into the elastomer chain by polymerization. Unless otherwise indicated, the contents of a monomer unit or repeating unit in the highly saturated diene elastomer are given as a molar percentage calculated on the basis of all the monomer units of the elastomer.

Copolymer of ethylene and a 1,3-diene

The rubber composition of the composite according to the invention comprises at most 50 pce of a copolymer of ethylene and a 1,3-diene, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer.

The copolymer of ethylene and a 1,3-diene is a highly saturated, preferably random, diene elastomer, which comprises ethylene units resulting from the polymerization of ethylene. As is known, the expression "ethylene unit" refers to the -(CH ₂ -CH ₂ )- unit resulting from the insertion of ethylene into the elastomer chain. The copolymer of ethylene and a 1,3-diene is rich in ethylene units, since the ethylene units represent more than 50 mol% of all the monomer units of the elastomer.

Preferably, the copolymer of ethylene and a 1,3-diene comprises at least 60 mol% of ethylene units, preferably at least 65 mol% of ethylene units, more preferably at least 70 mol% of ethylene units. In other words, the ethylene units in the copolymer of ethylene and a 1,3-diene preferably represent at least 60 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene, more preferably at least 65 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. Even more preferably, the ethylene units represent at least 70 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene.

Preferably, the ethylene units in the copolymer of ethylene and a 1,3-diene represent at most 90 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. More preferably, the ethylene units represent at most 85 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. Even more preferably, the ethylene units represent at most 80 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene.

According to an advantageous embodiment, the copolymer of ethylene and a 1,3-diene comprises from 60% to 90% by mole of ethylene unit, particularly from 60% to 85% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene. More advantageously, the copolymer of ethylene and a 1,3-diene comprises from 60% to 80% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene.

According to another advantageous embodiment, the copolymer of ethylene and a 1,3-diene comprises from 65% to 90% by mole of ethylene unit, particularly from 65% to 85% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene. More advantageously, the copolymer of ethylene and a 1,3-diene comprises from 65% to 80% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene.

According to yet another advantageous embodiment of the invention, the copolymer of ethylene and a 1,3-diene comprises from 70% to 90% by mole of ethylene unit, particularly from 70% to 85% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene. More advantageously, the copolymer of ethylene and a 1,3-diene comprises from 70% to 80% by mole of ethylene unit, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene.

The copolymer of ethylene and a 1,3-diene being a copolymer of ethylene and a 1,3-diene, it also comprises 1,3-diene units resulting from the polymerization of a 1,3-diene. As is known, the expression “1,3-diene unit” or “diene unit” refers to the units resulting from the insertion of the 1,3-diene by a 1,4 addition, a 1,2 addition or a 3,4 addition in the case of isoprene for example. The 1,3-diene units are those for example of a 1,3-diene having 4 to 12 carbon atoms, such as 1,3-butadiene, isoprene, 1,3-pentadiene, an aryl-1,3-butadiene. Preferably, the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes, one of which is 1,3-butadiene. More preferably, the 1,3-diene is 1,3-butadiene, in which case the copolymer of ethylene and a 1,3-diene is a copolymer of ethylene and 1,3-butadiene, preferably random.

The copolymer of ethylene and a 1,3-diene 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 of ethylene and a 1,3-diene. 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. In this respect, mention may be made of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant. The copolymer of ethylene and a 1,3-diene, 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 A1, WO 2018020122 A1 and WO 2018020123 A1. Advantageously, the copolymer of ethylene and a 1,3-diene is random and is preferably prepared according to a semi-continuous or continuous process such as described in documents WO 2017103543 A1, WO 201713544 A1, WO 2018193193 and WO 2018193194.

The copolymer of ethylene and a 1,3-diene preferably contains units of formula (I) or units of formula (II).

The presence of a 6-membered saturated cyclic unit, 1,2-cyclohexanediyl, of formula (I) in the copolymer may result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. When the copolymer of ethylene and a 1,3-diene comprises units of formula (I) or units of formula (II), the molar percentages of the units of formula (I) and the units of formula (II) in the highly saturated diene elastomer, respectively o and p, preferably satisfy the following equation (eq. 1) or equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene.

0 < o+p ≤ 30 (eq. 1)
0 < o+p < 25 (eq. 2)

Preferably, the copolymer of ethylene and a 1,3-diene comprises units of formula (I) at a molar rate greater than 0% and less than 15%, more preferably less than 10% by molar percentage, molar percentage calculated on the basis of all the monomer units of the copolymer of ethylene and a 1,3-diene.

Isoprenic elastomer

The rubber composition of the composite according to the invention has the essential characteristic of comprising at least one isoprene elastomer.

By "isoprene elastomer" is meant a homopolymer or a copolymer of isoprene, in other words a diene elastomer selected from the group consisting of natural rubber (NR) which can be plasticized or peptized, synthetic polyisoprenes (IR), the various copolymers of isoprene, in particular copolymers of isoprene-styrene (SIR), of isoprene-butadiene (BIR) or of isoprene-butadiene-styrene (SBIR), and the mixtures of these elastomers.

Preferably, the isoprene elastomer is selected from the group consisting of synthetic polyisoprenes, natural rubber, isoprene copolymers and their mixtures, preferably from the group consisting of natural rubber, polyisoprenes comprising a mass content of cis 1,4 bonds of at least 90%, more preferably of at least 98% relative to the mass of isoprene elastomer and their mixtures. Very preferably, the isoprene elastomer is natural rubber.

Preferably, the rubber composition of the composite according to the invention comprises at least 50 phr of isoprene elastomer. Preferably, the level of isoprene elastomer in the rubber composition is greater than 55 phr and less than or equal to 70 phr.

The rate of copolymer of ethylene and of a 1,3-diene useful for the needs of the invention, in particular of copolymer of ethylene and of 1,3-butadiene in the rubber composition, preferably varies in a range from 10 to 40 pce.

Advantageously, the rubber composition comprises from 10 to 40 pce of copolymer of ethylene and 1,3-diene, in particular of copolymer of ethylene and 1,3-butadiene, and from 60 to 90 pce of isoprene elastomer.

Inorganic charge

The rubber composition of the composite according to the invention comprises at least 30 pce of a reinforcing inorganic filler.

By "reinforcing inorganic filler" is meant in the present application, by definition, any inorganic or mineral filler (whatever its color and its natural or synthetic origin), also called "white" filler, "light" filler or even "non-black filler" as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tires, in other words capable of replacing, in its reinforcing function, a conventional tire-grade carbon black; such a filler is generally characterized, in a known manner, by the presence of hydroxyl groups (–OH) on its surface.

Suitable inorganic reinforcing fillers are, in particular, mineral fillers of the siliceous type, in particular silica (SiO ₂ ), or of the aluminous type, in particular alumina (Al ₂ O ₃ ).

Preferably, the reinforcing inorganic filler is silica. The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area both of less than 450 m ² /g, preferably from 30 to 400 m ² /g. Examples of highly dispersible precipitated silicas (known as "HDS") include the silicas "Ultrasil 7000" and "Ultrasil 7005" from Degussa, the silicas "Zeosil 1165MP", "1135MP" and "1115MP" from Rhodia, the silica "Hi-Sil EZ150G" from PPG, the silicas "Zeopol 8715", "8745" and "8755" from Huber, and the silicas with a high specific surface area as described in application WO 03/16837.

The physical state in which the reinforcing inorganic filler is present is immaterial, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and/or aluminous fillers.

The reinforcing inorganic filler used, in particular if it is silica, preferably has a BET surface area of between 45 and 400 m ² /g, more preferably between 60 and 300 m ² /g.

Preferably, the rubber composition of the composite according to the invention comprises from 30 to 150 pce, preferably from 35 to 100 pce of silica.

To couple the reinforcing inorganic filler to the elastomer, it is possible optionally to use in a 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 elastomer, in particular organosilanes, or bifunctional polyorganosiloxanes.

In particular, polysulfurized silanes, known as "symmetrical" or "asymmetrical" depending on their particular structure, may be used, as described for example in applications WO03/002648 (or US 2005/016651) and WO03/002649 (or US 2005/016650).

Examples of polysulfurized silanes include, in particular, bis-(C1-C4)-alkoxyl-(C1-C4)-alkylsilyl-(C1-C4)-alkyl polysulfides (in particular disulfides, trisulfides or tetrasulfides), such as, for example, bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulfides. Among these compounds, bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula [(C2H5O)3Si(CH2)3S2]2 or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, of formula [(C2H5O)3Si(CH2)3S]2, are used in particular. Also to be mentioned as preferred examples are polysulfides (in particular disulfides, trisulfides or tetrasulfides) of bis-(monoalkoxyl(C1-C4)-dialkyl(C1-C4)silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide as described in patent application US 2004/132880.

As a coupling agent other than polysulfurized alkoxysilane, mention may in particular be made of bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides as described in patent applications WO 02/30939 and WO 02/31041, or silanes or POS bearing azo-dicarbonyl functional groups, as described for example in patent applications WO 2006/125532, WO 2006/125533, WO 2006/125534.

In the elastomeric compositions in accordance with the invention, the content of coupling agent is preferably in a range from 5 to 60% by weight relative to the amount of silica, preferably in a range from 15 to 50% by weight relative to the amount of silica and preferably from 20 to 40% by weight relative to the amount of silica. These levels have proven to be particularly advantageous for obtaining the properties of the composites according to the invention.

The rubber composition of the composite according to the invention may also comprise carbon black.

Suitable carbon blacks are all carbon blacks, in particular HAF, ISAF, SAF type blacks conventionally used in tires (so-called tire grade blacks). Among the latter, mention will be made more particularly of the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, or even, depending on the intended applications, blacks of higher series (for example N660, N683, N772). The carbon blacks could for example already be incorporated into an isoprene elastomer in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600). The BET specific surface area of carbon blacks is measured according to standard D6556-10 [multi-point method (minimum 5 points) – gas: nitrogen – relative pressure range P/P0: 0.1 to 0.3].

Preferably, the rubber composition of the composite according to the invention does not comprise carbon black, or comprises less than 10 pce, preferably less than 5 pce.

Crosslinking system

The rubber composition of the composite according to the invention comprises a crosslinking system.

The crosslinking system may be based either on sulfur or on sulfur donors and/or on peroxide and/or on bismaleimides. Preferably, the crosslinking system is a vulcanization system, i.e. a system based on sulfur (or on a sulfur donor agent) and on a vulcanization accelerator. Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur may be used as a vulcanization accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following sulfenamide compounds: N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), and mixtures of these compounds.

Sulfur is used at a preferential rate of between 0.3 pce and 10 pce, more preferably between 0.3 and 5 pce. The primary vulcanization accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5 pce.

Preferably, the composition of the composite according to the invention comprises a metal oxide and a stearic acid derivative, the ratio of the rate of metal oxide and stearic acid derivative, in pce, being greater than 2. This preferential rate allows good adhesion to the reinforcing element embedded in the rubber composition. The metal oxide is preferably zinc oxide.

The rubber composition of the composite according to the invention preferably comprises a vulcanization accelerator. The vulcanization accelerator is used at a preferential rate such that the sulfur/vulcanization accelerator mass ratio is less than or equal to 5, preferably less than or equal to 4.

Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC"), and mixtures of these compounds.

Crosslinking (or cooking), where appropriate vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.

Various additives

The rubber composition of the composite according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended to be used in a vehicle tire, a conveyor belt or a belt, such as for example processing agents, plasticizers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants.

All plasticizers conventionally used in tires are suitable as plasticizers. In this respect, mention may be made of oils which are preferably non-aromatic or very weakly aromatic, chosen from the group consisting of naphthenic oils, paraffinic oils, MES oils, TDAE oils, vegetable oils, ether plasticizers, ester plasticizers.

Preferably, the rubber composition comprises less than 10 pce, preferably less than 5 pce of plasticizer.

The rubber composition may be manufactured in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first phase of thermo-mechanical working or kneading (sometimes referred to as a "non-productive" phase) at high temperature, up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second phase of mechanical working (sometimes referred to as a "productive" phase) at a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the sulfur or sulfur donor and the vulcanization accelerator are incorporated.

For example, the first (non-productive) phase is conducted in a single thermomechanical step during which all the necessary constituents, any additional processing agents and other various additives, with the exception of the sulfur and the vulcanization accelerator, are introduced into a suitable mixer such as a conventional internal mixer. The total mixing time in this non-productive phase is preferably between 1 and 15 min. After cooling the mixture thus obtained during the first non-productive phase, the sulfur and the vulcanization accelerator are then incorporated at low temperature, generally in an external mixer such as a cylinder mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

The final composition thus obtained is then calendered, for example in the form of a sheet or plate, in particular for characterization in the laboratory, or even extruded, to form for example a rubber profile used for the manufacture of semi-finished products such as a tire reinforcement ply.

Reinforcement element

The composite according to the invention comprises at least one reinforcing element embedded in the rubber composition.

By “embedded” is meant that the reinforcing element is completely covered by the rubber composition, with the possible exception of the composite cutting areas.

By reinforcing element is meant an element allowing the mechanical reinforcement of a matrix in which this reinforcing element is intended to be embedded. The reinforcing element comprises a wire element.

The wire element may be metallic or textile. A wire element is understood to mean an element having a length at least 10 times greater than the largest dimension of its section, regardless of the shape of the latter: circular, elliptical, oblong, polygonal, in particular rectangular or square or oval. In the case of a rectangular section, the wire element has the shape of a strip.

A metallic wire element may be a metallic elementary monofilament. Such a metallic elementary monofilament comprises a steel core, optionally coated with one or more layers of a coating which may be metallic and/or based on a non-metallic adhesive composition.

The metal coating comprises a metal selected from zinc, copper, tin, cobalt and alloys of these metals. Examples of alloys of these metals include brass and bronze. The core steel is a carbon steel comprising between 0.1% and 1.2% carbon by mass, at most 11% by mass of chromium, less than 1% by mass of each of the following elements: manganese, silicon, aluminum, boron, cobalt, copper, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, phosphorus, sulfur, nitrogen, the remainder consisting of iron and unavoidable impurities resulting from the production. The steel may have a pearlitic, ferritic, austenitic, bainitic, martensitic microstructure or a microstructure resulting from a mixture of these microstructures.

The elementary metal monofilament has a mechanical strength ranging from 1000 MPa to 5000 MPa. Such mechanical strengths correspond to the steel grades commonly encountered in the tire field, namely, the NT (Normal Tensile), HT (High Tensile), ST (Super Tensile), SHT (Super High Tensile), UT (Ultra Tensile), UHT (Ultra High Tensile) and MT (Mega Tensile) grades, the use of high mechanical strengths possibly allowing improved reinforcement of the matrix in which the reinforcing element is intended to be embedded and a lightening of the matrix thus reinforced.

In the case where the elementary metallic monofilament has a circular section, the diameter of these elementary metallic monofilaments preferably ranges from 0.05 mm to 0.50 mm.

A metal wire element may be an assembly of several elementary metal monofilaments as described above, assembled together in a helix, for example by cabling or twisting the elementary metal monofilaments to form, for example, layered cables comprising several concentric layers of elementary metal monofilaments or stranded cables, each strand comprising several concentric layers of elementary metal monofilaments. Optionally and as described in WO2005071157, such a metal wire element comprises a layer based on a polymeric composition, preferably a composition comprising an elastomer, this layer being arranged between two layers of elementary metal monofilaments of the layered cable or a strand of the stranded cable.

A textile wire element may be an elementary textile monofilament optionally coated with one or more layers of a coating based on an adhesive composition. This elementary textile monofilament is obtained, for example, by melt spinning, solution spinning or gel spinning. Each elementary textile monofilament is made of an organic material, in particular polymeric, or inorganic, such as for example glass or carbon. The polymeric materials may be of the thermoplastic type, such as for example aliphatic polyamides, in particular polyamides 6-6, and polyesters, in particular polyethylene terephthalate. The polymeric materials may be of the non-thermoplastic type, such as for example aromatic polyamides, in particular aramid, and cellulose, natural or artificial, in particular rayon.

A textile wire element may be an assembly of several elementary textile monofilaments as defined above. In a first variant, the assembly comprises from 2 to 7 elementary textile monofilaments each having a substantially circular section with a diameter ranging for example from 0.10 mm to 0.50 mm. In a second variant, the assembly comprises more than 10 elementary textile monofilaments, preferably more than 100 elementary textile monofilaments and more preferably more than 500 elementary textile monofilaments each having a substantially circular section with a diameter ranging for example from 2 µm to 100 µm. In the first and second variants, the assembly formed is commonly called a strand.

A textile wire element may also be an assembly of several assemblies or strands as defined above. In one variant, the materials from which the elementary textile monofilaments of each assembly or strand are made are identical. In another variant, the materials from which the elementary textile monofilaments of each assembly or strand are made are different, the textile wire element then being commonly called a hybrid textile wire element.

In one embodiment, whether in the case of a metallic or textile wire element, the layer based on a non-metallic adhesive composition is formed by a layer of an adhesion primer making it possible to improve the adhesion of the wire element, for example to an elastomeric matrix. Such adhesion primers are those commonly used by those skilled in the art for the pre-bonding of certain textile fibers (in particular polyester fibers, for example PET, aramid, aramid/nylon). For example, an epoxy-based primer, in particular based on polyglycerol polyglycidyl ether, may be used. A primer based on blocked isocyanate may also be used.

In another embodiment, whether in the case of a metallic or textile wire element, the layer based on a non-metallic adhesive composition is formed by a layer based on a resin and an elastomer latex. Adhesive compositions of the RFL (Resorcinol – Formaldehyde – Latex) type will be mentioned, but also adhesive compositions as described in WO2015118041.

In yet another embodiment, whether in the case of a metallic or textile wire element, there may be a layer of an adhesion primer as described above and coating the wire element, this layer of adhesion primer itself being coated with a layer based on a resin and a latex of one or more elastomers as described above.

In one embodiment, the reinforcing element comprises a wire element and optionally a sheath individually covering the wire element or collectively several wire elements. The sheath may comprise one or more layers, each layer being based on a polymeric composition, for example a [thermoplastic] composition or [as described in WO2010/136389, WO2010/105975, WO2011/012521, WO2011/051204, WO2012/016757, WO2012/038340, WO2012/038341, WO2012/069346, WO2012/104279, WO2012/104280 and WO2012/104281]. In this embodiment, the polymer composition of each layer of the sheath is different from the composition based on the matrix in which the sheathed wire element(s) is intended to be embedded.

In another embodiment, the reinforcing element may be a knit or a fabric.

A knit is an assembly of wire elements as defined above and comprising stitches formed by one or more of these wire elements. Each stitch comprises a loop interwoven with another loop. Examples include jersey or English rib knits for weft knits and charmeuse or atlas knits for warp knits.

A fabric is an assembly of a first family of threaded elements, called warp threaded elements, substantially parallel to each other, and a second family of threaded elements, called weft threaded elements, substantially parallel to each other. Preferably, the threaded elements of the first family are substantially perpendicular to the threaded elements of the second family.

In the embodiment of the composite in which each reinforcing element is a reinforcing wire element, the reinforcing wire elements are arranged parallel to each other and embedded, for example by calendering, in the rubber composition. A so-called straight ply is then obtained, in which the reinforcing wire elements of the ply are parallel to each other and are parallel to a main direction of the ply. Then, if necessary, portions of each straight ply are cut at a cutting angle and these portions are joined together so as to obtain a so-called angled ply, in which the reinforcing wire elements of the ply are parallel to each other and form an angle with the main direction of the angled ply, the angle formed with the main direction then being equal to the cutting angle.

Pneumatic

The vehicle bandage, another object of the invention, comprises a composite in accordance with the invention. Preferably, the bandage comprises a reinforced ply made of a composite in accordance with the invention.

The composite and the bandage according to the invention may be in the raw state (i.e. before crosslinking) or in the cooked state (i.e. after crosslinking).

Examples Preparation of rubber compositions

Seventeen rubber compositions C-1 to C-17, the formulation details of which are given in Tables 1 and 2, were prepared as follows:

The elastomers, the organic or inorganic filler (carbon black or silica) and the various other ingredients, with the exception of the sulphur and the vulcanisation accelerator, are successively introduced into an internal mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 80°C. Thermomechanical work is then carried out (non-productive phase) in one step, lasting a total of approximately 3 to 4 minutes, until a maximum "drop" temperature of 165°C is reached. The mixture thus obtained is recovered, cooled and then the sulphur and the vulcanisation accelerator are incorporated into a mixer (homo-finisher) at 30°C, mixing everything (productive phase) for an appropriate time (for example approximately ten minutes).

The compositions thus obtained are then calendered either in the form of plates (thickness 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or extruded to form, for example, a profile for a tire.

The rubber compositions, with the exception of compositions C-1, C-6 and C-10, contain a highly saturated diene elastomer having a molar ethylene content greater than 50% and natural rubber, in this case comprising 74 mol% of ethylene units.

Tests and measurements

Viscosity measurement Mooney (or plasticity Mooney )

An oscillating consistometer is used as described in the French standard NF T 43-005 (1991). The Mooney plasticity measurement is carried out according to the following principle: the composition in the raw state (before cooking) is molded in a cylindrical enclosure heated to 100°C. After one minute of preheating, the rotor rotates within the test piece at 2 revolutions/minute and the torque useful for maintaining this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU=0.83 Newton.meter). The lower the Mooney value, the lower the viscosity before cooking and the better the processability of the composition.

Tensile tests

The tests were carried out in accordance with French standard NF T 46-002 of September 1988. All tensile measurements were carried out under normal temperature (23±2°C) and hygrometry (50±5% relative humidity) conditions, according to French standard NF T 40-101 (December 1979).

The nominal secant modulus calculated by reducing it to the initial section of the test piece (or apparent stress, in MPa) at 10% elongation noted MA ₁₀ , was measured in second elongation (i.e. after accommodation), on samples cooked for 60 minutes at 150°C.

Dynamic properties (after cooking)

The dynamic properties tan(d)max at 23°C are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of crosslinked composition (cylindrical specimen 4 mm thick and 400 mm² in section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under the defined temperature conditions, for example at 23°C according to the ASTM D 1349-99 standard. A strain amplitude scan is carried out from 0.1 to 50% (forward cycle), then from 50% to 1% (return cycle). The results used are the loss factor tan(d). For the return cycle, the maximum value of tan(d) observed is indicated, denoted tan(d)max.

It is recalled that, as is well known to those skilled in the art, the value of tan(d)max at 23°C is representative of the hysteresis of the material and therefore of the rolling resistance: the lower the tan(d)max at 23°C, the more the rolling resistance is reduced and therefore improved.

Adhesion tests

Strips are made from three metal wires with a diameter of 0.32 mm placed parallel to each other and embedded in a polyamide 6-6 sheath so as to obtain a strip 0.46 mm thick and 1.45 mm wide.

The strip is covered with RFL glue and then embedded in the tested rubber composition.

To test the adhesion of the tested rubber composition to the strip, a measurement was carried out according to ASTM D2229.

Adhesion levels are characterized by measuring the so-called tear force (denoted Fmax) to tear the strip from the test specimen. The results are expressed on a base of 100, a value greater than 100 indicating a tear force greater than the reference test specimen.

copolymer of ethylene and a 1,3-diene

The copolymer of ethylene and a 1,3-diene used in the following examples is prepared according to the following procedure:

In a 70 L reactor containing methylcyclohexane (64 L), ethylene (5600 g) and 1,3-butadiene (2948 g), butyloctylmagnesium (BOMAG) dissolved in methylcyclohexane and the catalytic system is added. The Mg/Nd ratio is 6.2. The volume of the solution of the catalytic system introduced is 840 mL, the concentration of the solution of the catalytic system in Nd being 0.0065 M. The reaction temperature is regulated at a temperature of 80 °C and the polymerization reaction starts. The polymerization reaction takes place at a constant pressure of 8.3 bars. The reactor is supplied throughout the polymerization with ethylene and 1,3-butadiene in the molar proportions 73/27. The polymerization reaction is stopped by cooling, degassing the reactor and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered after steam stripping and drying to constant mass. The polymerization time is 225 minutes. The weighted mass (6.206 kg) allows the determination of the average catalytic activity of the catalytic system expressed in kilograms of polymer synthesized per mole of neodymium metal and per hour (kg/mol.h). The copolymer has a ML (1+4) value at 100°C equal to 62.

The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from a metallocene, [Me ₂ Si(Flu) ₂ Nd(μ-BH ₄ ) ₂ Li(THF)] at 0.0065 mol/L, a co-catalyst, butyloctylmagnesium (BOMAG) whose BOMAG/Nd molar ratio is equal to 2.2, and a preformed monomer, 1,3-butadiene whose 1,3-butadiene/Nd molar ratio is equal to 90. The medium is heated to 80°C for a period of 5 hours. It is prepared according to a preparation method in accordance with paragraph II.1 of patent application WO 2017093654 A1.

The resulting copolymer of ethylene and a 1,3-diene, a copolymer of ethylene and 1,3-butadiene, is an ethylene-butadiene elastomer, hereinafter referred to as “EBR”.

Example 1

In this example, the proportion of EBR in the NR-EBR blend is varied. The way in which the stiffness/hysteresis compromise evolves (MA ₁₀ /tan(d) ratio) is evaluated. The results are expressed on a base of 100, the value of 100 being assigned, for each series including a given silica content, to the stiffness/hysteresis compromise of the composition not including EBR.

A result greater than 100 indicates that the composition of the example considered has a higher ratio than the control.

(1) Copolymer of ethylene and 1,3-butadiene containing 74 mol% of ethylene unit, 19 mol% of butadiene unit in the form of 1,2 and 1,4 units and 7 mol% of 1,2-cyclohexanediyl unit, of Tg -44°C.

(2) "Zeosil 1165 MP" from Solvay-Rhodia in the form of microbeads, CTAB 160 m²/g, precipitated silica

(3) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from Evonik company

(4) Diphenylguanidine “Perkacit DPG” from Flexsys company

(5) N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine “Santoflex 6PPD” from Flexys

(6) Stearic acid “Pristerene 4931” from Uniqema company

(7) Industrial grade Zinc Oxide from Umicore

(8) N-cyclohexyl-2-benzothiazol-sulfenamide “Santocure CBS” from Flexsys company

We see that the association of an inorganic filler with a blend of natural rubber and an EBR allows a very good expression of the rigidity/hysteresis compromise, this expression being all the more marked as the inorganic filler content is high.

For a lower inorganic filler content, the stiffness/hysteresis trade-off no longer changes significantly depending on the proportion of NR and EBR in the NR:EBR blend.

Example 2

In this example, we evaluate how the stiffness/hysteresis trade-off (MA ₁₀ /tan(d) ratio) evolves by varying the proportion of EBR in the NR-EBR blend for a set of compositions comprising carbon black, and a set of compositions comprising silica. Compositions C-14 and C-17 are adjusted so as to have substantially the same MA ₁₀ stiffness and the same stiffness/hysteresis trade-off.

The results are expressed in base 100, the value of 100 being attributed to the stiffness/hysteresis ratio and to the MA ₁₀ stiffness of the C-4 composition. A result greater than 100 indicates that the composition of the example considered has a higher stiffness (or a higher ratio) than the control.

(1) to (8) same as Table 1

(9) ASTM N347 grade carbon black

(10) Cobalt salt

(11) Cyclohexylthiopthalimide (PVI)

(12) N-tert-butyl-2-benzothiazyl sulfenamide from Flexsys

In Table 2, the compositions were adjusted so that the stiffness at 10% strain (MA10) was similar for the silica-based and carbon black-based blends. The results are expressed in base 100, based on the C-4 composition.

We see that the stiffness at 10% deformation and the stiffness/hysteresis compromise of the compositions C-14 (carbon black) and C-4 (silica) are similar.

It is observed that the association of an inorganic filler with a blend of natural rubber and an EBR allows a better expression of the rigidity/hysteresis compromise than the association of an organic filler with a blend of natural rubber and an EBR.

The data presented in Table 3 are also represented on the .

The cracking rate increases as a function of the restitution energy. These rates increase in approximately the same way as long as the EBR content is below 50 pce. The cracking rate increases significantly faster when the EBR content reaches 50 pce.

Example 3

In this example, the adhesion properties of different compositions are evaluated. Different rubber blocks are tested with the compositions shown in Table 4.

For compositions C-1 to C-4, the reference test piece is the test piece consisting of the rubber composition not comprising EBR (C-1). For compositions C-6 and C-8, the reference test piece is the test piece consisting of the rubber composition not comprising EBR (C-6). For compositions C-14 and C-16, the reference test piece is the test piece consisting of rubber composition C-14.

It is noted that for the compositions tested, the level of adhesion is not significantly impacted by the presence of EBR.

Claims (13)

Composite comprising at least one reinforcing element embedded in a rubber composition, the rubber composition being based on at least one isoprene elastomer, at most 50 pce of a copolymer of ethylene and a 1,3-diene, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer, at least 30 pce of a reinforcing inorganic filler, and a crosslinking system. Composite according to the preceding claim, in which the rubber composition comprises a metal oxide and a stearic acid derivative, the ratio of the content of metal oxide and stearic acid derivative, in pce, being greater than 2. Composite according to any one of the preceding claims in which the rubber composition comprises less than 10 pce, preferably less than 5 pce of plasticizer. Composite according to any one of the preceding claims in which the copolymer of ethylene and a 1,3-diene comprises at least 60 mol% of ethylene units, preferably at least 65 mol% of ethylene units, more preferably at least 70 mol% of ethylene units. Composite according to any one of the preceding claims in which the 1,3-diene units of the copolymer of ethylene and a 1,3-diene are those of a 1,3-diene having 4 to 12 carbon atoms, preferably those of 1,3-butadiene, isoprene, 1,3-pentadiene, an aryl-1,3-butadiene and a mixture of these units. A composite according to any preceding claim wherein the reinforcing inorganic filler of the rubber composition is silica. Composite according to the preceding claim in which the rubber composition comprises from 30 to 150 pce of silica. Composite according to one of claims 6 or 7, in which the rubber composition comprises a coupling agent whose content is in a range from 5 to 60% by weight relative to the quantity of silica, preferably in a range from 15 to 50% by weight relative to the quantity of silica and preferably ranging from 20 to 40% by weight relative to the quantity of silica. Composite according to any one of the preceding claims in which the rubber composition does not comprise carbon black, or comprises less than 10 phr, preferably less than 5 phr. Composite according to any one of the preceding claims in which the reinforcing element comprises a textile or metallic wire element. Composite according to the preceding claim in which the metallic wire element is an elementary metallic monofilament or an assembly of several elementary metallic monofilaments. Composite according to claim 10 in which the reinforcing element comprises a textile wire element made of a thermoplastic or non-thermoplastic polymeric material. A vehicle tire comprising a composite according to any preceding claim.