Thermoplastic elastomer composition and article incorporating it, for example a pipe.

Abstract

The invention relates to a thermoplastic elastomer composition, in particular for use in a single-layer (1) or multi-layer pipe, and to an elastomer or elastomer-textile or metal composite article which incorporates the composition. The composition comprises: (i) at least one elastomer, (ii) at least one polyolefin comprising a recycled polyolefin part and optionally a virgin polyolefin part, (iii) a reinforcing filler, (iv) a plasticizing system, and (v) an antioxidant system. According to the invention, the composition comprises, in mass fractions: - more than 35% of said at least one polyolefin, and - less than 30% of said plasticizing system. Fig. 1

Description

Title of the invention: Thermoplastic elastomer composition and article incorporating it, for example a pipe. Technical field

[0001] The invention relates to a thermoplastic elastomer composition in particular usable in a single-layer or multi-layer pipe, and an elastomer article or elastomer-textile or metal composite which incorporates this composition. The invention applies in particular to a single-layer or multi-layer pipe, for example for a cooling circuit of a battery or an electric motor of a hybrid or electric motor vehicle, it being specified that the invention relates generally to any elastomer or composite article comprising an elastomer material (including seals, anti-vibration devices and any other elastomer element, for example for a battery pack or for a data processing center, without limitation) which is capable of equipping a land vehicle (automobile or rail), aquatic, air or space, as well as any industrial or residential installation. Prior art

[0002] As is known, a hose for a motor vehicle cooling circuit is most often made from rubber(s), and may be of the following type: - single-layer, as for example in document FR 3 130 922 A1 in the name of the Applicant which presents a pipe without reinforcing reinforcement for conveying a cooling fluid at no more than 2.5. 105 Pa and no more than 110°C, consisting of a layer of rubber based on an ethylene-propylene-diene terpolymer (EPDM), or - most often multi-layer, comprising an internal rubber layer designed to be in contact with the cooling fluid, a reinforcing reinforcement egtextile overlying the inner layer, and at least one outer rubber layer overlying the reinforcement, as in document US 11,833,787 B2 in the name of the Applicant which describes an inner layer based on an EPDM, a textile reinforcing reinforcement, an outer layer based on an ethylene-vinyl acetate (EVA) rubber and an intermediate layer based on a mixture of EPDM rubber with an EVA rubber or with an acrylic rubber of the polyacrylate (ACM) or ethylene polyacrylate (AEM) type.

[0003] There has recently been an attempt to use thermoplastic elastomers (TPE) instead of the aforementioned rubbers to manufacture hoses carrying liquids, as for example described in document WO 2022 / 234351 A1 which discloses, for manufacturing at least one layer of a reinforced or spiral hose, the use of a TPE consisting of: (A) 30-80% by weight of a polymeric matrix consisting of 10-35% of a first thermoplastic part (Al) and 20-45% of a second elastomeric part (A2) present in the TPE; (B) 30-55% by weight of at least one plasticizing agent; (C) 0-30% by weight of at least one filler; (D) 0-10% by weight of at least one additive; TPE with a Shore A hardness of 50-85, a mass rate of PCR recycled material (“PCR” for post-consumer) greater than or equal to 50%, and the TPE being present at least 90% of the total weight of the pipe.

[0004] A major drawback of the pipes presented in WO 2022 / 234351 A1 lies in the fact that they are specifically designed to form irrigation, watering or water transport pipes in a swimming pool or spa, and are not suitable for the operating conditions of a cooling circuit of an electric motor or a motor vehicle battery (see in particular the TPE-S and TPV respectively tested in Tables 3 and 6 of WO 2022 / 234351 A1, devoid of reinforcing filler such as carbon black, which have breaking stress values ​​significantly lower than the minimums required for single-layer pipes for such a cooling circuit).

[0005] Indeed, such a cooling circuit requires both mechanical and chemical resistance of the pipe to its electrochemical degradation in contact with the pressurized cooling liquid (usually of the glycolated water type) and its external environment (usually hot air), these requirements having to characterize the same layer in the case of a single-layer pipe. In particular, a pipe for this cooling circuit must have properties at break remaining satisfactory, even after long-term thermal aging in contact with air and glycolated water.

[0006] Another disadvantage of the pipes presented in WO 2022 / 234351 A1 lies in their relatively high amount of plasticizer used. Statement of the invention

[0007] An aim of the present invention is to propose a thermoplastic elastomer composition in particular capable of constituting a single-layer pipe for a cooling circuit of a battery or an electric motor of an electric or hybrid motor vehicle, the pipe in particular overcoming the aforementioned drawbacks without penalizing its suitability for implementation by extrusion, nor its rheological properties, and having mechanical properties and resistance to thermal aging under glycolated water and under air sufficient to be capable of chemically and mechanically resisting prolonged conditions of temperature and pressure adapted to the circulation of a coolant.

[0008] This aim is achieved in that the Applicant has unexpectedly discovered that if, in a thermoplastic elastomer composition, an elastomer is combined with a sufficiently high quantity of a polyolefin comprising a recycled part in the presence of a sufficiently small quantity of a plasticizing system, then a composition can be obtained which, via a reinforcing filler and an antioxidant system, is particularly well suited to forming a single-layer pipe or an internal and / or external layer of a multi-layer pipe for the aforementioned cooling circuit, having in particular satisfactory rheological, extrudability, flexibility and mechanical properties at break even after said thermal aging under glycolated water and under air, and therefore a lastingly satisfactory dynamic resistance in this cooling circuit.

[0009] More specifically, a thermoplastic elastomer composition according to the invention comprises: (i) at least one elastomer, (ii) at least one polyolefin comprising a recycled polyolefin part and optionally a virgin polyolefin part, (iii) a reinforcing charge, (iv) a plasticizing system, and (v) an antioxidant system, and said composition comprises, in mass fractions: - more than 35% of said at least one polyolefin, and - less than 30% of said plasticizing system.

[0010] It will be noted that this combination of high and, on the contrary, reduced quantities respectively for the at least partly recycled polyolefin and for the plasticizing system, which goes against the technical prejudice for a person skilled in the art represented by the aforementioned teaching of WO 2022 / 234351 A1, makes it possible in a particularly advantageous manner to confer on the extruded composition both rheological properties, extrudability properties and, in addition, satisfactory mechanical properties which can even be improved after thermal aging, in comparison with the mechanical properties of a reference thermoplastic elastomer composition having a similar formulation but of which said at least one polyolefin is entirely virgin (i.e. is not at least partly recycled).

[0011] It follows that a composition according to the invention is thus particularly well suited to constituting not only a single-layer pipe and an internal layer and / or an external layer of a multi-layer pipe, but also a sealing joint or an anti-vibration device, by way of example and in no way limiting.

[0012] It will also be noted that a thermoplastic elastomer composition according to the invention, which differs from the rubber compositions commonly used for cooling circuit pipes, in particular, has the advantage of being easily shaped (e.g. by extrusion) just like a thermoplastic composition. Detailed description

[0013] By “thermoplastic elastomer composition” is meant in the present description a TPE material preferably belonging to the family of thermoplastic vulcanizates (TPV), even if the following can be used as a variant: - unvulcanized olefinic TPEs (TPE-0 or TPO) for example derived from one or more polyolefin(s) (e.g. polyethylenes and propylenes) and a diene or non-diene elastomer (e.g. chosen from EPDMs, copolymers of ethylene and at least one linear or branched alpha-olefin having from 3 to 20 carbon atoms, such as for example EPM copolymers of ethylene-propylene or POE copolymers of ethylene-octene), or even - certain styrenic TPEs (TPE-S or TPS) derived from olefins (such as ethylene, propylene or butylene) for TPS eg with SEBS blocks for polystyrene-b-poly(ethylene-butylene)-b-polystyrene, SEPS for polystyrene-b-poly(ethylene-propylene)-b-polystyrene, or SEEPS for polystyrene-b-poly(ethylene-ethylene / propylene)-b-polystyrene.

[0014] Generally speaking, it will be noted that the combination of ingredients (i) to (v) above makes it possible to give the compositions according to the invention satisfactory mechanical properties including secant moduli, Shore A hardness, breaking stress and elongation at break which are each sufficiently high, which makes it possible to use, in a first embodiment of the invention, only a single layer to form a single-layer pipe conveying a fluid at a pressure of at most 3.0.105 Pa and at a temperature of at most 120°C, such as a coolant for a low-pressure, low-temperature cooling circuit of a battery or an electric motor of a hybrid or electric motor vehicle.As will be detailed below, these advantageous properties of a composition according to the invention make it also usable in a multi-layer pipe which can incorporate a reinforcing reinforcement, according to a second embodiment of the invention.

[0015] As elastomer(s) which can be used in a composition according to the invention of the TPV type, mention may be made, without limitation, of diene or non-diene elastomers according to a mass fraction of elastomer(s) in the composition inclusively between 10% and 40%, the elastomers preferably being chosen from: - EPDM, - homopolymers or copolymers of butadiene and / or isoprene (eg poly-butadiene BR, polyisoprene IR) and optionally in addition a vinylaromatic comonomer (eg styrene for an SBR), acrylonitrile (eg for an NBR rubber) or branched alpha-olefin such as isobutylene (eg for an IIR butyl rubber), - copolymers of ethylene and at least one linear or branched alpha-olefin having from 3 to 20 carbon atoms, such as for example EPM or POE, and - acrylic rubbers of the polyacrylate (ACM) or ethylene polyacrylate (AEM) type.

[0016] Advantageously, as an elastomer usable in a composition according to the invention of the TPV type, it is possible to use an ethylene interpolymer (copolymer or terpolymer, e.g. an EPDM, EPM, POE or AEM) whose ethylene is biosourced, being for example of plant origin (e.g. derived from cane sugar).

[0017] According to a preferred example of a composition according to the invention of the TPV type, at least one EPDM is used as elastomer, the mass fraction of said at least one elastomer in the composition then being inclusively between 15% and 25%. In addition, said at least one EPDM is then advantageously not extended with oil, and may have: - mass rates of units derived from ethylene of 40-50%, of a non-conjugated diene (such as ethylidene norbornene, ENB) of 8-10%, and preferably - a Mooney viscosity ML(l+4) at 125°C between 55 and 70.

[0018] Advantageously, a composition according to the invention of the TPE type (i.e. including TPS, TPO and TPV) may comprise said recycled polyolefin part according to a mass fraction greater than 25%, preferably inclusively between 28% and 50%, for example between 30% and 45%.

[0019] By "recycled polyolefin part" of a composition according to the invention of the TPE type (eg TPS, TPO or TPV), is meant in the present description one or more polyolefins which are each non-virgin, i.e. which each come from recycling of the "PIR" or "PCR" type (i.e. from a recycled polyolefin material of the post-industrial (PIR) or post-consumer (PCR) type), or each come from grinding followed by regeneration in an extruder for example twin-screw.

[0020] It will be noted that said at least one polyolefin of a composition according to the invention of the TPE type (eg TPS, TPO or TPV) may comprise said virgin polyolefin part according to a mass fraction in the composition inclusively between 0% and 50%, preferably greater than 0% and less than or equal to 40%, depending on the recycling or regeneration process implemented to obtain said recycled polyolefin part. In addition, said virgin polyolefin part may comprise the same polyolefin as said recycled polyolefin part, or another polyolefin.

[0021] Advantageously, a composition according to the invention of the TPE type (eg TPS, TPO or TPV) may comprise said virgin polyolefin part in a mass fraction greater than 10%, preferably inclusively between 15% and 35%.

[0022] Also advantageously, a composition according to the invention of the TPE type (eg TPS, TPO or TPV) may comprise said recycled polyolefin part and said virgin polyolefin part according to a total mass fraction inclusively between 40% and 70%, preferably between 50% and 68%, for example between 55% and 65%.

[0023] According to another general characteristic of a composition according to the invention of the TPE type (eg TPS, TPO or TPV), said at least one polyolefin may comprise a homopolymer or interpolymer (eg random, segmented or block copolymer) of at least one aliphatic or alicyclic alpha-olefin (such as propylene or butylene, without limitation), including an interpolymer of ethylene and at least one alpha-olefin, for example propylene.

[0024] According to an exemplary embodiment of a composition according to the invention of the TPE type (eg TPS, TPO or TPV), said recycled polyolefin part and optionally said virgin polyolefin part included(s) in said at least one polyolefin each comprise, independently of one another, a homopolymer or a copolymer of propylene, preferably a homopolymer or a copolymer of recycled propylene derived from a recycled polyolefin material of the PIR or PCR type, or a regenerated polyolefin material. For example, said at least one polyolefin comprises: - a homopolymer or copolymer of recycled propylene (PP), according to a mass fraction in said at least one polyolefin inclusively between 50% and 100%, which may be equal to or greater than 75% and less than 100%, and - a homopolymer or copolymer of virgin propylene (PP), according to a mass fraction in said at least one polyolefin inclusively between 0% and 50%, which may be greater than 0% and less than or equal to 25%.

[0025] According to an even more preferential example of a composition according to the invention of the TPV type, at least one EPDM is used as elastomer and, as polyolefin, at least one propylene homopolymer (PP), with in this case: - the mass fraction of said at least one EPDM in the composition inclusively between 15% and 25%, for example between 17% and 22%, and / or - the mass fraction of recycled PP inclusively between 28% and 50%, for example between 30% and 45%, and / or - the mass fraction of virgin PP inclusively between 15% and 35%, for example between 17% and 32%, and / or - the total mass fraction of recycled PP and virgin PP inclusively between 40% and 70%, for example between 50% and 68%.

[0026] By "reinforcing filler" is generally meant in the present description one or more individual fillers of reinforcing grades for an elastomer, which are preferably constituted in whole or in part by a reinforcing carbon black and which are dispersed homogeneously in the composition, it being specified that the reinforcing filler may further comprise an organic filler other than a carbon black (e.g. graphite) and optionally furthermore an inorganic filler, such as a silica or another clear filler.

[0027] Advantageously, said reinforcing filler may comprise a carbon black, which is optionally recycled at least in part and which is for example of ASTM N500 or N600 series, the carbon black being present in the TPE type composition (eg TPS, TPO or TPV) according to a mass fraction inclusively between 1% and 15%, preferably between 4% and 10%.

[0028] It will be noted that this relatively reduced quantity of carbon black in the composition makes it possible in particular to give a single-layer pipe made of this composition a compromise between relatively high resistivity and sufficient reinforcement, and therefore to minimize the electrochemical degradation of the pipe in contact with the fluid that it carries when this fluid is a coolant of the glycolated water type, without penalizing the resistance of the pipe to its external environment.

[0029] According to another general characteristic of a composition according to the invention of the TPE type (eg TPS, TPO or TPV) with reference to any one of the aforementioned characteristics, the composition may comprise: - said plasticizing system according to a mass fraction inclusively between 3% and 25%, preferably between 4% and 15% and for example between 5% and 12%, - preferably with a mass fraction of carbon black in the composition inclusively between 1% and 15%, for example between 4% and 10%.

[0030] As a plasticizing system according to the invention, at least one plasticizing oil and / or at least one plasticizing resin may be used, it being specified that said plasticizing system preferably comprises at least one oil chosen from mineral oils, bio-sourced oils derived from biomass (including modified or unmodified vegetable oils), and mixtures thereof.

[0031] Even more preferably, at least one oil chosen from paraffinic, naphthenic and aromatic mineral oils is used as plasticizing system, e.g. a mineral oil that is at least partly naphthenic (which may comprise both paraffinic, naphthenic and aromatic fractions).

[0032] It will be noted that said plasticizing system used according to the aforementioned reduced mass fraction according to the invention, in comparison with the significantly higher mass fractions conventionally used in pipes, nevertheless makes the compositions of the invention having the aforementioned characteristics suitable for being implementation by mixing then extrusion, or only by reactive extrusion.

[0033] According to another general characteristic of the invention, the composition, in the case where it is of the TPV type, comprises a crosslinking system which is free of phenolic resin and zinc oxide (ZnO) and which preferably comprises an organic peroxide as crosslinking agent and a crosslinking coagent chosen from triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), and acrylate-based coagents such as ethylene glycol dimethacrylate (EGDMA).

[0034] Alternatively, a composition according to the invention of the TPV type could comprise a sulfur crosslinking system, optionally in addition to a peroxide crosslinking agent.

[0035] Said crosslinking system of a TPV composition according to the invention makes it possible to chemically crosslink this composition preferably by reactive extrusion, and in addition, because this crosslinking system is completely free of ZnO, it makes it possible not to inhibit the anti-rust system used in the cooling circuit (the ZnO used as a crosslinking activator in the rubber compositions of the prior art is known to interact unfavorably with this anti-rust system).

[0036] Generally speaking, with reference to any of the aforementioned characteristics, said antioxidant system of a composition according to the invention of the TPV type may advantageously comprise: - a first antioxidant, preferably heterocyclic aromatic, for example based on polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, and - a second antioxidant based on a thioether, for example distearyl disulfide, and preferably said antioxidant system further comprises a third antioxidant based on an aromatic amine.

[0037] It will be noted that this mixed and preferably ternary antioxidant system advantageously makes it possible to confer on the TPV compositions according to the invention improved mechanical properties after thermal aging in air and in glycolated water, in comparison with the mechanical properties of a reference TPV composition of similar formulation but of which said at least one polyolefin is entirely virgin (i.e. is not at least partly recycled).

[0038] According to other characteristics of the compositions according to the invention of TPV type, these compositions can have: - a continuous phase comprising said at least one polyolefin, and a discontinuous phase comprising nodules of said at least one elastomer (for example at least one EPDM) which are dispersed in said at least one polyolefin, and - a stress and elongation at break, measured in uniaxial tension according to ISO 37:2017 after aging for 3000 h at 120°C in contact with air and glycolated water, respectively, which are greater than the stress and the elongation at break of said reference TPV composition where said at least one polyolefin is for example made of a virgin propylene homopolymer.

[0039] According to another general aspect of the invention with reference to any of the aforementioned characteristics, the compositions according to the invention of the TPE type (eg TPS, TPO or TPV) can be prepared by mixing in an internal mixer followed by twin-screw extrusion, or alternatively by a single reactive twin-screw extrusion step.

[0040] According to another general aspect of the invention with reference to any one of the aforementioned characteristics, an elastomer or elastomer-textile or metal composite article according to the invention comprises or is made up of an extrudate formed from a composition according to the invention of the TPE type (eg TPS, TPO or TPV), the article being in particular chosen from single-layer pipes, multi-layer pipes optionally reinforced by a textile reinforcement, sealing joints for motor vehicles or for buildings, anti-vibration devices and support, wedging or protection elements for battery packs or for data processing centers.

[0041] Advantageously and without limitation, the article may be an extruded single-layer or multi-layer pipe for a cooling circuit of a battery or an electric motor of an electric or hybrid motor vehicle, preferably a single-layer pipe which is made of said TPE type composition (eg TPS, TPO or TPV) and which can be used to convey a cooling fluid of a battery at a pressure of at most 3.0. 105 Pa and at a temperature of at most 120°C.

[0042] As explained above, the mechanical properties of the TPE composition and consequently of the single-layer pipe which can be made from it are sufficient for it to convey a coolant with good dynamic resistance under these temperature and pressure conditions. The single-layer pipes according to said first embodiment of the invention can thus have reduced internal and external diameters in comparison with the reinforced pipes of the prior art, which consequently appear oversized for a low-pressure and low-temperature circuit. As a result, the pipes according to said first embodiment of the invention have a significantly reduced manufacturing cost compared with the reinforced pipes known for automotive cooling circuits.

[0043] A pipe according to a second embodiment of the invention is of the multilayer type, comprising a radially internal layer, a radially external layer and optionally a reinforcing reinforcement (e.g. textile or metallic), with the internal layer and / or the external layer which are made of a composition according to the invention of the TPE type (e.g. TPS, TPO or TPV) as defined above, with reference to any one of the aforementioned characteristics.

[0044] As reinforcement, at least one reinforcement can be used textile or not covering the internal layer (e.g. a frame formed of knitted, braided or covered threads, for example in PET, aramid or rayon).

[0045] A pipe according to said second embodiment of the invention can be used for the transfer of a liquid, gaseous or supercritical fluid at a pressure which can be greater than 3.105 Pa and / or at a temperature which can be greater than 120°C.

[0046] It will be noted that a pipe according to this second embodiment of the invention may further comprise a barrier layer made of a plastic material, based on at least one thermoplastic polymer. This barrier layer may form the most radially internal layer of the pipe, or else an “inter-fold” between the internal tube and a reinforcing layer or between the internal tube and an intermediate layer.

[0047] A fluid circuit according to the invention, in particular for cooling a battery or an electric motor for a hybrid or electric motor vehicle, comprises a plurality of single-layer and / or multi-layer pipes mounted on connectors, for example thermoplastic, and it can be characterized in that at least one (and preferably each) of the pipes is as defined above.

[0048] By the expression "based on", it is meant in the present description that the composition or ingredient considered comprises predominantly by weight the constituent concerned, i.e. according to a mass fraction greater than 50%, preferably greater than 75% and possibly up to 100%. Brief description of the drawings

[0049] Other characteristics, advantages and details of the invention will emerge from reading the following description of several exemplary embodiments of the invention, given for illustrative purposes in relation to the attached drawings, among which: Fig.l

[0050] [Fig.l] is a schematic side and perspective view of a single-layer pipe according to the invention. Fig. 2

[0051] [Fig.2] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to an example of the invention. Fig. 3

[0052] [Fig.3] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to another example of the invention. Fig. 4

[0053] [Fig.4] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to another example of the invention. Fig. 5

[0054] [Fig.5] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to another example of the invention. Fig. 6

[0055] [Fig.6] is an atomic force microscope (AFM) image illustrating the morphology of a reference composition not in accordance with the invention. Fig. 7

[0056] [Fig.7] is an MFA image illustrating the morphology of a first composition according to the invention. Fig. 8

[0057] [Fig.8] is an MFA photograph illustrating the morphology of a second composition according to the invention. Fig. 9

[0058] [Fig.9] is a stress-strain graph, before aging, of said reference composition and of said second composition according to the invention. Fig. 10

[0059] [Fig. 10] is a stress-strain graph after thermal aging in glycolated water, of said reference composition and of said second composition according to the invention. Fig. 11

[0060] [Fig. 11] is a stress-strain graph after thermal aging in air, of said reference composition and of said second composition according to the invention. Examples of embodiments of the invention

[0061] The single-layer pipe 1 of [Fig. 1] is capable of conveying a fluid such as a coolant, at a pressure of at most 3. 105 Pa and a temperature of at most 120° C, and it can be assembled with two connectors, for example thermoplastic. This pipe 1 is made of a TPE composition according to the invention (eg TPS, TPO or TPV) as defined above.

[0062] The multilayer pipe 10 of [Fig. 2] is capable of conveying any fluid such as those mentioned above, at a pressure which may be equal to or greater than 3.105 Pa, and it comprises a radially internal tube 11, a reinforcing layer 12 and a radially external covering layer 13, it being specified that at least one of the tube 11 and the covering layer 13 is made of a TPE composition according to the invention (eg TPS, TPO or TPV) as defined above.

[0063] The reinforcing layer 12 may comprise, without limitation, a knit, braid or cover based on multifilament yarns made from one or more textile material(s), for example from a polyamide (e.g. aramid), polyester (e.g. PET) or rayon (the term “yarn” usually designating both a yarn based on a multitude of elementary filaments of small diameter which are twisted together, than a twist obtained by twisting several yarns).

[0064] The multilayer pipe 20 of [Fig. 3] differs from that of [Fig. 2], in that the internal tube 21 is surmounted by an intermediate layer 22 itself surmounted by a reinforcing layer 23 covered by a covering layer 24, it being specified that at least one of the tube 21 and the covering layer 24 is made of a TPE composition according to the invention.

[0065] The multilayer pipe 30 of [Fig.4] differs from that of [Fig.3], in that the internal tube 31 is surmounted by an internal reinforcing layer 32 itself surmounted by an intermediate layer 33 covered by an external reinforcing layer 34 then by a covering layer 35, it being specified that at least one of the tube 31, the intermediate layer 33 and the covering layer 35 is made of a TPE composition according to the invention.

[0066] The multilayer pipe 40 of [Fig. 5] differs from that of [Fig. 3], in that the internal tube 41 is surmounted by a barrier layer 42 of plastic material forming an interfold, then by an intermediate layer 43 covered with a reinforcing layer 44, itself surmounted by a covering layer 45, it being specified that at least one of the tube 41, the intermediate layer 43 and the covering layer 45 is made of a TPE composition according to the invention.

[0067] It will be noted that a multilayer pipe according to the invention could comprise an arrangement of layers differing from those illustrated in Figures 2-5, both in the number of its layers and in their respective functions.

[0068] Preparation of the reference composition C1, of the first composition according to the invention II and of the second composition according to the invention 12:

[0069] Three thermoplastic vulcanizate (TPV) compositions were prepared, respectively forming the reference composition C1 and the first and second compositions according to the invention II and I2, for example capable of constituting a single-layer pipe for a cooling circuit, by implementing the following preparation method.

[0070] A mixing step was first implemented in an internal mixer, with incorporation of the ingredients listed below into the mixing cycle (first the elastomer, the polyolefin, the processing agents and the plasticizing system, then the crosslinking system and finally the antioxidant system at the end of the cycle), with a temperature rise due to shearing up to a plateau of 200°C for 8 minutes.

[0071] In a second step, an extrusion step was carried out in a twin-screw extruder at 190°C of the recovered mixture.

[0072] Each of the three TPV compositions C1, C1 and C2 thus obtained was then shaped into H2-sized dumbbell-type test pieces to carry out the measurements of mechanical properties in the crosslinked state (stress / strain curves and resulting properties at break). These properties were measured in uniaxial tension at 23°C according to ISO 37:2017 in the initial state, then after two types of thermal aging.

[0073] The following Table 1 details the formulation of composition C1 (in parts by weight of each ingredient in the composition) thus prepared. [Tables 1] Ingredients Cl EPDM with ethylene mass content of 44%, ENB of 9%, and ML(l+4) at 125°C of 63 60 Polypropylene: “PPH3060” 170 Crosslinking agent: alkylphenol formaldehyde resin 4 Activator: ZnO 3 Processing agents PEG 5 Stearic acid 0.5 Fatty acids 1 lubricant 1 Carbon black: ASTM N500 series 22 Plasticizer: mineral oil of formula [Chem. 1] below 24.8 Antioxidant aromatic amine of formula [Chem. 2] below 1,5 alkyl-dihydroquinoline 1

[0074] [Chem.l]

[0075] [Chem.2]

[0076] The following Table 2 details the formulation of compositions II and 12 (in parts by weight of each ingredient in the composition) thus prepared. [Tables 2] Ingredients II 12 EPDM with ethylene mass content of 44%, ENB of 9%, and ML(l+4) at 125°C of 63 60 60 Polypropylene (PP) with recycled (rPP) and virgin (vPP) fractions: For II: PIR at 50% mass, of recycled PP “PRC50UFO black” For 12: PCR at 70% mass, of recycled PP “rPP1002” 195 170 Crosslinking agent: bis-alkylperoxide 2.4 2.4 Co-crosslinking agent: acrylate-based 1.2 1.2 Processing agent: PEG PEG 5 5 Carbon black: ASTM N500 series 22 22 Plasticizer: mineral oil of formula [Chem. 1] above 24.8 24.8 Antioxidants Aromatic amine of formula [Chem. 2] 1.5 1.5 alkyl-dihydroquinoline 1 1 Thioether: distearyl disulfide 1 1

[0077] Composition II thus contains 195 parts by weight of a post-industrial recycled polyolefin material (i.e. “PIR” type) with the name “PRC50UFO black”, comprising: - 50% by weight of a recycled polypropylene rPP, comprising predominantly by weight a homopolymer or copolymer of propylene, i.e. 97.5 parts by weight of rPP, and - 50% by weight of other ingredients which may comprise predominantly by weight a virgin polypropylene vPP (homopolymer or copolymer of propylene, identical or different from that of rPP), and at least one additive (such as an antioxidant, for example) in trace amounts, i.e. 97.5 parts by weight of these other ingredients. The mass fractions of rPP and vPP in composition II are therefore each approximately 31%, while the respective mass fractions of EPDM, carbon black and plasticizer in composition II are respectively 19%, 7% and 8%.

[0078] Composition 12 thus contains 170 parts by weight of a post-consumer recycled polyolefin material (i.e. “PCR” type) with the name “rPP1002”, comprising: - 70% by weight of a recycled polypropylene rPP, comprising predominantly by weight a homopolymer or copolymer of propylene, i.e. 119 parts by weight of rPP, and - 30% by weight of other ingredients which may comprise predominantly by weight a virgin polypropylene vPP (homopolymer or copolymer of propylene, identical or different from that of rPP), and at least one additive (such as an antioxidant, for example) in trace amounts, i.e. 51 parts by weight of these other ingredients. The mass fractions of rPP and vPP in composition 12 are therefore approximately 41% and 18% respectively, while the respective mass fractions of EPDM, carbon black and plasticizer in composition 12 are approximately 21%, 8% and 9% respectively.

[0079] As illustrated in the photographs of Figures 6-8, the morphological analyses using an atomic force microscope (AFM) show, for each of the three compositions C1, C1 and C2, that the polyolefin thermoplastic phase (PP) is continuous and that the elastomer phase (EPDM) has a structure of elastic nodules dispersed in the rigid matrix of this continuous polyolefin phase. These photographs also show a reduction in the average size of the elastomer nodules in compositions C1 and C2 according to the invention, compared to composition C1.

[0080] It was verified that the rheological and extrudability properties of compositions II and 12 according to the invention were analogous to those of the reference composition C1.

[0081] And as indicated above, uniaxial tensile tests were carried out at 23°C according to the ISO 37:2017 standard on H2 specimens made up of compositions Cl and 12, in the initial state (i.e. before any exposure of the compositions to the fluids and operating conditions characterizing their operation), the results of which are visible in the stress / strain curves of [Fig.9].

[0082] As illustrated in [Fig.9], it was verified that the mechanical properties in tension and in particular the properties at break of composition 12 were analogous in the initial state to those of composition Cl (see the quasi-superposition of the curves of 12 and Cl from low to high deformations).

[0083] These uniaxial tensile tests were then carried out again according to ISO 37:2017 on H2 specimens made up of compositions Cl and 12, but after two separate thermal aging cycles respectively in contact with a cooling liquid made up of glycolated water and in contact with air.

[0084] As illustrated in [Fig. 10], after thermal aging in immersion at 120°C in a 50% / 50% water / glycol solution for a period of 3000 h, it was verified that the tensile properties (measured at 23°C) and in particular the breaking properties of composition 12 were improved compared to those of composition Cl (see the curve of 12 reflecting lower stresses for given deformations, from 80% relative deformation, compared to the stresses ap applied to composition Cl for these same deformations, and higher maximum stresses for 12 compared to Cl at the highest deformations).

[0085] As illustrated in [Fig.l 1], after thermal aging in air at 120°C for a period of 3000 h, it was verified that the tensile properties (measured at 23°C) and in particular the properties at break of composition 12 were also improved compared to those of composition Cl (see the curve of 12 translating lower stresses for given deformations, from 30% relative deformation, compared to the stresses applied to composition Cl for these same deformations, and higher maximum stresses for 12 compared to Cl at the highest deformations).

[0086] In conclusion, compositions II and 12 according to the invention, which are notably characterized in that they comprise a durable polyolefin (e.g. a recycled polypropylene) in a mass fraction greater than 30%, or even greater than 40% (composition 12), and therefore have a reduced carbon footprint compared to the reference composition (carbon footprint reduced by 29% for composition II and by 30% for composition 12), have a resistance to thermal aging that is similar and even improved (cf. composition 12) compared to composition C1, both in contact with a glycolated fluid and with air, which demonstrates the suitability and even the superiority of the compositions according to the invention for constituting in particular a single-layer pipe or the internal and / or external layers of a multi-layer pipe for a cooling circuit of a battery or an electric motor of a motor vehicle.

[0087] It will be noted that this resistance to thermal aging, similar and even improved for the compositions according to the invention, is made possible in particular by the aforementioned mixed antioxidant system, comprising a first antioxidant, preferably heterocyclic aromatic, and a second antioxidant based on a thioether, in addition to the other ingredients of the compositions of the invention.

[0088] It will also be noted that, as the compositions of the invention are free of zinc oxide, they advantageously do not interact with the anti-rust system used in the cooling circuit, which anti-rust system is thus not inhibited and fully ensures its protective function.

Claims

Claims

1. Thermoplastic elastomer composition in particular usable in a single-layer (1) or multi-layer (10, 20, 30, 40) pipe of a cooling circuit of a battery or an electric motor of an electric or hybrid motor vehicle, the composition comprising: (i) at least one elastomer, (ii) at least one polyolefin comprising a recycled polyolefin part and optionally a virgin polyolefin part, (iii) a reinforcing filler, (iv) a plasticizing system, and (v) an antioxidant system, in which the composition comprises, in mass fractions: - more than 35% of said at least one polyolefin, and - less than 30% of said plasticizing system.

2. Composition according to claim 1, wherein the composition comprises said recycled polyolefin part in a mass fraction greater than 25%, preferably inclusively between 28% and 50%, for example between 30% and 45%.

3. A composition according to claim 1 or 2, wherein the composition comprises said virgin polyolefin portion in a mass fraction greater than 10%, preferably inclusively between 15% and 35%.

4. A composition according to claim 3, wherein the composition comprises said recycled polyolefin portion and said virgin polyolefin portion in a total mass fraction inclusively of between 40% and 70%, preferably between 50% and 68%, for example between 55% and 65%.

5. Composition according to one of the preceding claims, in which the composition comprises said plasticizing system in a mass fraction inclusively between 3% and 25%, preferably between 4% and 15% and for example between 5% and 12%.

6. Composition according to one of the preceding claims, in which said at least one polyolefin comprises: - a homopolymer of at least one alpha-olefin, for example propylene, or - an interpolymer of ethylene and at least one alpha-olefin, for example propylene, said recycled polyolefin part preferably comprising a recycled propylene homopolymer or copolymer from a recycled polyolefin material of post-industrial (PIR) or post-consumer (PCR) type, and for example in which said recycled polyolefin part and said virgin polyolefin part respectively comprise, independently of one another: - a recycled propylene (PP) homopolymer or copolymer, according to a mass fraction in said at least one polyolefin inclusively of between 50% and 100%, and - a virgin propylene (PP) homopolymer or copolymer, according to a mass fraction in said at least one polyolefin inclusively of between 0% and 50%.

7. Composition according to claim 6, wherein the composition is a thermoplastic vulcanizate (TPV), said at least one elastomer being chosen from - EPDMs, - homopolymers or copolymers of butadiene and / or isoprene, and optionally in addition a vinylaromatic comonomer, acrylonitrile or a branched alpha-olefin, - copolymers of ethylene and at least one linear or branched alpha-olefin having from 3 to 20 carbon atoms, and - acrylic rubbers of the polyacrylate (ACM) or polyethylene acrylate (AEM) type, preferably in which said at least one elastomer is chosen from ethylene-propylene-diene terpolymers (EPDM), butyl rubbers (IIR) and ethylene-octene copolymers (POE), and preferably in which the mass fraction of said at least an elastomer in the composition is inclusively between 10% and 40%.

8. The composition of claim 7, wherein the composition comprises a crosslinking system which is free of phenolic resin and zinc oxide and which preferably comprises an organic peroxide as a crosslinking agent and a crosslinking coagent selected from triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), and acrylate-based coagents such as ethylene glycol dimethacrylate (EGDMA).

9. A composition according to claim 7 or 8, wherein said at least an elastomer is an ethylene-propylene-diene terpolymer (EPDM) in which the ethylene is optionally biosourced, and preferably in which the mass fraction of said at least one elastomer in the composition is inclusively between 15% and 25%.

10. Composition according to one of the preceding claims, in which said reinforcing filler comprises a carbon black which is optionally recycled at least in part and which is for example of ASTM N500 or N600 series, said carbon black being present in the composition in a mass fraction inclusively between 1% and 15%, preferably between 4% and 10%.

11. Composition according to one of the preceding claims, in which said antioxidant system comprises: - a first antioxidant, preferably heterocyclic aromatic, for example based on polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, and - a second antioxidant based on a thioether, for example distearyl disulfide, and preferably in which said antioxidant system further comprises a third antioxidant based on an aromatic amine.

12. Composition according to claims 9, 10 and 11, wherein the composition forming said thermoplastic vulcanizate (TPV) comprises a continuous phase comprising said at least one polyolefin, and a discontinuous phase comprising nodules of said at least one elastomer which are dispersed in said at least one polyolefin, and wherein the composition has a stress and an elongation at break, measured in uniaxial tension according to ISO 37:2017 after aging for 3000 h at 120°C in contact with air and glycolated water, respectively, which are higher than the stress and the elongation at break of a reference thermoplastic vulcanizate composition where said at least one polyolefin, devoid of recycled polyolefinic part, is made of a virgin propylene (PP) homopolymer.

13. Composition according to one of the preceding claims, in which said plasticizing system comprises at least one oil chosen from mineral oils, bio-sourced oils derived from biomass such as modified or unmodified vegetable oils, and mixtures thereof, and for example in which said at least one oil is chosen from paraffinic, naphthenic and aromatic mineral oils.

14. Elastomer or elastomer-textile or metal composite article, in particular chosen from single-layer pipes (1), multi-layer pipes (10, 20, 30, 40) optionally reinforced by a textile reinforcement (12, 23, 32, 34, 44), seals for motor vehicles or for buildings, anti-vibration devices and support, wedging or protection elements for battery packs or for data processing centers, in which the article comprises or consists of an extrudate formed from a composition according to one of the preceding claims.

15. An article according to claim 14, wherein the article is an extruded single-layer (1) or multi-layer (10, 20, 30, 40) pipe for a cooling circuit of a battery or an electric motor of an electric or hybrid motor vehicle, and preferably wherein the article is a single-layer pipe (1) which is made of said composition and which is usable for conveying a cooling fluid of a battery at a pressure of at most 3.

0. 105 Pa and at a temperature of at most 120°C.

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