Rubber composition and hose incorporating it.

Abstract

The invention relates to a rubber composition which can be used to form at least one layer of a pipe in the crosslinked state, and to a pipe (10) of which at least one layer (11, 13) is made of this composition. The invention applies to any pipe for transferring a fluid under pressure, preferably to a multilayer pipe for a motor vehicle. The rubber composition according to the invention, based on at least one elastomer, comprises a reinforcing filler and a crosslinking system comprising sulfur and / or a peroxide, the reinforcing filler comprising at least one recycled carbon black from grinding and thermal decomposition of used rubber-based articles, and a functionalized lignin in powder form. Fig. 1

Description

Title of the invention: Rubber composition and hose incorporating it. Technical field

[0001] The invention relates to a rubber composition based on at least one elastomer which can be used to form at least one layer of a pipe in the crosslinked state, and to a pipe of which at least one layer is made of this composition. The invention applies to a single-layer or multi-layer pipe for conveying a fluid under pressure, preferably a multi-layer pipe conveying a fluid at a pressure equal to or greater than 2.105 Pa, the fluid possibly being a liquid (e.g. water or a coolant), a gas or a supercritical fluid (e.g. in an air conditioning circuit), a gas mixture (e.g. air in an air intake circuit), or a fuel. The invention generally applies to any pipe for transferring a fluid for a heat engine, an electric motor or for a fuel cell (e.g.hydrogen) of a motor, rail, aquatic, air or space vehicle, as well as for any industrial or residential installation transporting a fluid under pressure. Prior art

[0002] In a known manner, a rubber hose for a motor vehicle cooling circuit usually comprises an inner layer designed to be in contact with the coolant conveyed, at least one reinforcing reinforcement surmounting the inner layer (typically a reinforcement formed from knitted, braided or covered yarns, for example made of PET, aramid or rayon), and an outer layer surmounting the reinforcement and exposed to the air surrounding the hose. These inner and outer layers are typically made of a rubber composition reinforced by a filler comprising a carbon black of fossil origin and of reinforcing grade (i.e. conventional carbon black usually referred to as “virgin”, generally obtained by thermal decomposition or incomplete combustion of hydrocarbons), possibly coupled or replaced by a mineral reinforcing inorganic filler, such as a silica or a kaolin, for example.

[0003] In recent years, attempts have been made to couple such a carbon black with another reinforcing filler of neither fossil nor mineral origin, i.e. a bio-sourced filler (derived from biomass), such as lignin, in order to reduce the proportion of fossil or mineral ingredients in the composition and, in return, to increase the proportion of bio-sourced ingredients. The following patent documents may be cited in particular: relating to rubber compositions for pipes comprising a partly bio-sourced reinforcing filler.

[0004] WO 2023 / 025808 A1 presents a peroxide-crosslinked rubber composition, for example for a hose, which comprises: - to its examples 1-2: 150 parts by weight of an EPDM rubber, 70 pce of a lignin “L1” modified by hydrothermal treatment and 60 pce of a virgin carbon black “N-550”, and - to its examples 3-4: 100 parts by weight of an EPDM rubber, 50 pce of a lignin “L2” modified by hydrothermal treatment and 50 pce of virgin carbon black “N-550”.

[0005] EP 4 059 996 A1 presents a sulfur-crosslinked rubber composition, for example for a hose, which comprises: - in his example Ab: 100 parts by weight of a nitrile-butadiene rubber (NBR), 40 pce of a “HTC” lignin modified by hydrothermal treatment and 20 pce of a virgin carbon black “N550”, - in its example Bb: 100 parts by weight of a polychloroprene rubber (CR), 40 pce of the lignin “HTC” and 20 pce of the virgin carbon black “N550”, - in its example Cb: 100 parts by weight of EPDM rubber, 40 pce of “HTC” lignin and 20 pce of virgin carbon black “N550”, - in its example Db: 100 parts by weight of a natural rubber (NR), 40 pce of the lignin “HTC” and 20 pce of the virgin carbon black “N550”, - in its example Es: 100 parts by weight of a bromobutyl rubber (BIIR), 5 pce of the lignin “HTC” and 55 pce of a virgin carbon black “N660”, and - in its example Eb: 100 parts by weight of a bromobutyl rubber (BIIR), 40 pce of the lignin “HTC” and 20 pce of the virgin carbon black “N660”.

[0006] A disadvantage of the rubber compositions tested in these examples of WO 2023 / 025808 A1 and EP 4 059 996 A1, which use as reinforcing filler a virgin carbon black and a modified lignin, lies in their reduced sustainable mass fraction which is at most 22% in said examples. Statement of the invention

[0007] An aim of the present invention is to provide a rubber composition which can be used to form at least one layer of a pipe in the crosslinked state, the composition in particular overcoming the aforementioned drawback of the prior art, while exhibiting an ability to be processed in the crosslinkable state and properties in the crosslinked state which are both satisfactory for said layer of the pipe.

[0008] This aim is achieved in that the Applicant has just discovered that if a mixed reinforcing filler comprising - recycled carbon black from the grinding and thermal decomposition of used rubber-based articles, and - a functionalized lignin in powder form, then at least one layer of a pipe can be obtained having, in comparison with a “control” rubber composition differing only from the composition of the invention by the use of a virgin carbon black (i.e. non-recycled) coupled with the same functionalized lignin: - in the crosslinkable state: an ability to be implemented and a resistance to scorching which are generally preserved, or even improved, and - in the crosslinked state: physical and mechanical properties which are substantially preserved, or even improved, and which are not generally more penalized than the “control” composition following thermo-oxidative aging, so as to give the pipe implementation characteristics and operating properties at least equivalent compared to a pipe incorporating said “control” composition.

[0009] In other words, a rubber composition according to the invention, which is based on at least one elastomer, can be used to form at least one layer of a pipe in the crosslinked state and comprises a reinforcing filler and a crosslinking system comprising sulfur and / or a peroxide, is such that the reinforcing filler comprises at least one recycled carbon black resulting from grinding and thermal decomposition of used rubber-based articles, and a functionalized lignin in powder form.

[0010] 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%.

[0011] By "at least one recycled carbon black resulting from grinding and thermal decomposition of used rubber-based articles", it is meant that said or each recycled carbon black (i.e. non-virgin carbon black, called "recovered carbon black" in English) is essentially obtained by grinding, then by decomposition at high temperature of the ground material (such as pyrolysis, (vapo)thermolysis or devulcanization) of a used article made of at least one rubber or mainly consisting of at least one rubber (such as a tire, a pipe, a seal, a belt or any other industrial rubber product). By "grinding" and by "ground material" is meant generically in the present description respectively a crushing possibly completed by shredding of the used rubber-based article, and the product of the successive crushing and possibly shredding operations applied to the used articles.

[0012] By "functionalized lignin" is meant in the present description a carbonaceous lignin, whether modified by thermohydrolysis or by another modification / purification process, making it possible to obtain a purified lignin extract. In a known manner, lignin is a major component of lignocellulosic biomass, consisting of a branched macromolecule of phenolic polymer type comprising in particular carbonyl (C=O), aliphatic hydroxyl and phenolic hydroxyl functional groups. The functionalized lignin usable in the invention may in particular have all or part of these functional groups.

[0013] According to exemplary embodiments of the invention, the functionalized lignin in powder form comprises: - particles devoid of CO or COO groups on the surface, and / or - is a kraft lignin, for example derived from the wood of gymnosperm trees, such as conifers.

[0014] It will be noted that the combination of said at least one recycled carbon black and functionalized lignin makes it possible to confer on the crosslinked composition according to the invention (both with sulfur and with peroxide) physical properties (e.g. density, hardness, volume resistivity) and mechanical properties (e.g. secant modulus M100 at 100% deformation, elongation and breaking stress, compression set) which are each sufficient for the pipe according to the invention, of which at least one layer is made up of this composition, to have processing characteristics and operating properties (e.g. pressure resistance, dynamic strength and resistance to aging) equivalent to those of a pipe incorporating said “control” composition (which differs only from the composition of the invention in that the carbon black coupled with the same functionalized lignin is virgin).

[0015] Advantageously, said at least one recycled carbon black may have composition reinforcing properties similar to those of a virgin carbon black of reinforcing grade chosen from the ASTM N300, N400, N500, N600 and N700 series, for example similar to those of a carbon black of the N500 or N600 series (eg similar to those of an N550 or N660 black, without limitation).

[0016] According to another aspect of the invention, the composition comprises, in addition to said at least one elastomer, the crosslinking system and functionalized lignin in powder form: a recycled powder mixture which comprises the product of a thermal decomposition reaction by thermolysis, pyrolysis or devulcanization, applied to a ground material of said used rubber-based articles, the recycled powder mixture comprising said at least one recycled carbon black and being for example micronized, in particular in the case where said reaction is a thermolysis or a pyrolysis.

[0017] Advantageously, the recycled powder mixture may comprise said at least one recycled carbon black according to a mass fraction of between 80% and 99%, and inorganic substances according to a mass fraction of between 1% and 20% comprising in particular silicon oxides and / or zinc compounds, the recycled powder mixture in micronized form being for example derived from the pyrolysis of used tires.

[0018] By "reinforcing filler" is meant in the present description a filler comprising individual fillers of reinforcing grades for said at least one elastomer which are dispersed homogeneously in the composition, it being specified that the reinforcing filler may further comprise: - a reinforcing organic filler other than said at least one recycled carbon black, e.g. a virgin carbon black of identical or different grade compared to that of the recycled carbon black, and / or another carbon filler (e.g. graphite or carbon nanotubes), and / or - a reinforcing inorganic filler (e.g. a clear filler, such as silica) which can be of mineral or bio-sourced origin.

[0019] According to a preferred embodiment of the invention which may include any of the aforementioned characteristics, the reinforcing filler may further comprise at least one virgin carbon black (i.e. non-recycled) having, for example, a BET specific surface area measured according to the ASTM D 6556 standard which is between 10 and 50 m2 / g and for example 15-30 m2 / g, such as a carbon black of the N500 or N600 series (e.g. N550 or N660, without limitation).

[0020] According to another general characteristic of the invention which may include any of the aforementioned characteristics, the composition may comprise 10-120 pce of said at least one recycled carbon black and 2-90 pce of functionalized lignin (pce: parts by weight per 100 parts of elastomer(s)).

[0021] It will be noted that the incorporation of functionalized lignin into the reinforcing filler does not preclude the use of a high quantity of carbon black in the composition, making it possible to give it satisfactory mechanical properties.

[0022] According to another general characteristic of the invention which may include any one of the aforementioned characteristics, said at least one elastomer may be chosen from ethylene-propylene-diene terpolymers (EPDM), copolymers isobutylene-isoprene (IIR), halogenated isobutylene-isoprene copolymers (XIIR), silicone rubbers, fluorinated silicone rubbers, acrylic rubbers of the polyacrylate (ACM) and polyethylene acrylate (AEM) types, and brominated isobutylene-para-methylstyrene copolymers.

[0023] It will be noted, however, that rubbers other than those mentioned above can be used in the composition according to the invention, depending on the properties sought for the or each layer of the pipe.

[0024] According to a particular embodiment of the invention: - said at least one elastomer is made up of at least one EPDM, - the crosslinking system comprises a peroxide or sulfur, and - the composition comprises 15-100 pce of said at least one recycled carbon black and 5-80 pce of functionalized lignin.

[0025] Preferably, said at least one EPDM, not extended with oil, has: - mass rates of units derived from ethylene of 52-70%, of a non-conjugated diene (such as ethylidene norbornene) of 4-7%, and preferably in addition - a Mooney viscosity ML(l+4) at 125°C of between 70 and 90. For example, a mixture of two non-oil-extended EPDMs can be used, one of which has a mass content of ethylene units of 53-57% and a Mooney viscosity ML(l+4) at 125°C of between 75 and 85, and the other of which has a mass content of ethylene units of 66-70% and a Mooney viscosity ML(l+4) at 125°C of between 80 and 90.

[0026] According to a preferred embodiment of this particular mode of the invention, the composition based on at least one EPDM comprises: - 10-80 pce of said at least one virgin carbon black, having for example a BET specific surface area measured according to the ASTM D 6556 standard which is between 10 and 50 m2 / g, - 15-80 pce of said at least one recycled carbon black, and - 15-80 pce of said functionalized lignin, with the sum of the quantities of said at least one virgin carbon black and said at least one recycled carbon black in the composition being 60-110 pce.

[0027] Even more preferably, according to said preferred example of the invention, the sum of the quantities of said at least one virgin carbon black and said at least one recycled carbon black in the composition based on at least one EPDM is 70-100 phr, and the sum of the quantities of said at least one virgin carbon black, recycled carbon black and functionalized lignin in the composition is 100-130 phr.

[0028] Also preferably, the reinforcing filler comprises: - functionalized lignin according to a mass fraction of 15-30%, and - said at least one virgin carbon black and said at least one recycled carbon black according to a total mass fraction of carbon black of 70-85%.

[0029] According to said preferred example of the invention, the composition based on at least one EPDM can advantageously have, in the crosslinked state, a volume resistivity greater than 106 Ohm.cm, preferably 108 Ohm.cm and even more preferably 1012 Ohm.cm, measured according to standard IEC 62631 3.

[0030] It will be noted that these compositions according to the invention based on at least one EPDM thus have a high resistivity thanks to said functionalized lignin, despite the use of a high quantity of carbon black which is known to penalize this resistivity (by increasing the electrical conductivity). This high resistivity makes it possible in particular to minimize the electrochemical degradation of the internal layer of the pipe in contact with the fluid that it carries, when this fluid is a cooling liquid, for example of the glycolated water type, without penalizing the resistance of the pipe to its external environment.

[0031] It will further be noted that the aforementioned quantities used for said at least one recycled carbon black, the functionalized lignin and optionally said at least one virgin carbon black, combined with the use of a suitable plasticizing system, make it possible to limit the Mooney viscosity ML(l+4) at 100°C of the crosslinkable composition (whatever the elastomer matrix used) while preventing its premature crosslinking (scorching), thus making the composition of the invention suitable for being implemented by mixing then extrusion.

[0032] As a plasticizing system for the composition according to the invention, at least one plasticizing oil and / or at least one plasticizing resin may be used, it being specified that the plasticizing system according to the invention preferably comprises at least one oil chosen from mineral oils, oils derived from biomass (including modified or unmodified vegetable oils), and mixtures thereof.

[0033] Even more preferably, at least one oil chosen from paraffinic, naphthenic and aromatic mineral oils is used as plasticizing system, for example a mineral oil that is at least partly naphthenic (which may comprise both paraffinic, naphthenic and aromatic fractions).

[0034] Concerning said crosslinking system, it makes it possible to chemically crosslink the rubber composition by subsequent curing of the hose comprising the or each layer made of the composition, at a temperature for example between 160 and 200°C. This crosslinking system, if it is peroxide, may comprise an organic peroxide and a crosslinking co-agent for example chosen from triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC).

[0035] According to another general aspect of the invention which may relate to any of the aforementioned characteristics, the composition may have a mass fraction of sustainable ingredients (i.e. biosourced and recycled), which sustainable ingredients include said at least one recycled carbon black and said functionalized lignin, which is greater than 25%, preferably greater than 30%, for example equal to or greater than 40%.

[0036] It will be noted that said sustainable ingredients, present in the composition in an amount of more than 25%, 30% or even 40%, may consist of said at least one recycled carbon black and said functionalized lignin, or alternatively also include one or more other sustainable ingredients.

[0037] According to another general aspect of the invention, the crosslinkable rubber compositions of the invention are prepared by implementing a process essentially comprising the following successive steps: (a) introduction of the ingredients of the composition, with the exception of the crosslinking system, into an internal mixer; b) one-stage thermomechanical work in this internal mixer, until reaching a maximum "drop" temperature, for example 20-130°C; c) recovery then cooling of the mixture thus obtained; then d) addition of the crosslinking system to sulfur or peroxide in an external mixer (e.g. with cylinders) at a temperature of 95-105°C, with mechanical work in this external mixer of the crosslinkable composition thus obtained.

[0038] Alternatively, the crosslinking system can be introduced during step b) of thermomechanical working with maximum temperature control at 120°C for example, or during a second introduction into the internal mixer following cooling of the precursor mixture resulting from the first step.

[0039] As evidenced by the results presented in the examples below, the physical (e.g. density, hardness, volume resistivity) and mechanical (e.g. M100 at 100% deformation, elongation and breaking stress, compression set) properties of the crosslinked compositions according to the invention are overall sufficient for the pipes incorporating them to convey a fluid at a pressure of at least 2.105 Pa with good dynamic resistance, even after thermo-oxidative aging at 150°C for 168 h.

[0040] A pipe according to an embodiment of the invention for the transfer of a liquid, gaseous or supercritical fluid for a thermal or electric engine or for a fuel cell of a motor, rail, aquatic, air or space vehicle, the pipe comprising a radially internal rubber tube, at least one layer of reinforcement and a rubber cover layer, is suitable for conveying fluid at a pressure equal to or greater than 2.105 Pa.

[0041] A pipe according to this embodiment of the invention is such that at least one of the inner tube and the cover layer is made of a rubber composition in the crosslinked state as defined above.

[0042] It will be noted that the pipe according to this 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 radially innermost layer of the pipe, or a “crease” between the inner tube and a reinforcing layer or between the inner tube and an intermediate rubber layer. Brief description of the drawings

[0043] 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

[0044] [Fig.l] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to an example of the invention. Fig. 2

[0045] [Fig.2] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to another example of the invention. Fig. 3

[0046] [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

[0047] [Fig.4] is a schematic side and perspective view with partial cutaways of a multilayer pipe according to another example of the invention. Examples of embodiments of the invention

[0048] The multilayer pipe 10 of [Fig.l] is capable of conveying any fluid such as those mentioned above, at a pressure preferably equal to or greater than 2.105 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 rubber composition according to the invention as defined above, eg based on at least one: - EPDM, in particular in the case of a pipe carrying water or a coolant for a thermal or electric engine or for a fuel cell of a motor vehicle, or - ACM or AEM (e.g. Vamac® type), particularly in the case of a pipe carrying air (e.g. air intake of a motor vehicle engine).

[0049] As explained above, the tube 11 and the cover layer 13 may alternatively each be based on at least one IIR or XIIR (halogenated butyl rubber, e.g. chlorinated or brominated), at least one optionally fluorinated silicone rubber (e.g. MQ, PMQ, PVMQ, VMQ, or FMQ, FVMQ) or at least one brominated isobutylene-para-methylstyrene copolymer (e.g. name Exxpro®).

[0050] 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, and a twist obtained by twisting several yarns).

[0051] The multilayer pipe 20 of [Fig. 2] differs from that of [Fig. 1], in that the internal tube 21 is surmounted by an intermediate layer 22 itself surmounted by a reinforcing layer 23 covered with a covering layer 24, it being specified that at least one of the tube 21 and the covering layer 24 is made of a composition according to the invention.

[0052] The multilayer pipe 30 of [Fig. 3] differs from that of [Fig. 2], 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 composition according to the invention.

[0053] The multilayer pipe 40 of [Fig.4] differs from that of [Fig.2], 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 composition according to the invention.

[0054] It will be noted that a multilayer pipe according to the invention could comprise an arrangement of layers differing from those illustrated in Figures 1-4, both in the number of its layers and in their respective functions. Preparation of a control composition C1, of compositions not in accordance with the invention C2-C3 and of compositions according to the invention 11-15:

[0055] The control rubber composition C1, the non-inventive rubber compositions C2-C3 and the inventive rubber compositions 11-15 were prepared essentially by carrying out the following process.

[0056] The ingredients of each composition, with the exception of the crosslinking system, were introduced into a Banbury® type internal mixer. One-step thermomechanical work was then carried out (mixing time: 30 s to 2 min.), until a maximum "drop" temperature of approximately 125°C was reached. The resulting mixture was collected, cooled, and then the crosslinking system was added to an external roller mixer at 100°C, mixing everything for about 2 min. in a mechanical working step.

[0057] The crosslinkable rubber compositions C1-C3 and 11-15 thus obtained were then shaped in the form of cylindrical test pieces to carry out measurements of properties in the uncrosslinked state (Mooney viscosity and roasting time), and in the form of dumbbell-type test pieces to carry out measurements of mechanical properties in the crosslinked state after curing the test piece at 180°C (hardness, secant modulus M100 at 100% deformation and properties at break).

[0058] On each crosslinkable cylindrical test piece, the Mooney viscosity ML(l+4) at 100°C according to the ISO 289-1 standard and the roasting time t5 without premature crosslinking at 135°C according to the ISO 289-2 standard were measured.

[0059] In addition, on each dumbbell-type crosslinked test piece: (a) density, according to ISO 2781, b) Shore A hardness after 3 seconds according to ISO 48-4, c) the secant modulus M100 in uniaxial tension according to ISO 37:2017, d) the breaking stress and elongation at break, in uniaxial tension according to ISO 37:2017, e) compression set: at 25%: 72 h / 130° C after 30 min. according to ISO 815-1 standard (method B), and at 25%: after 72 h / 140° C (specification “FCA”: Fiat Chrysler Automobiles) according to ISO 1817 standard, and f) the volume resistivity measured at 1000 V.

[0060] Each test piece consisting of rubber compositions C1-C3 and 11-15 was subjected to thermo-oxidative aging in hot air for 168 h at 150°C, then the hardness and stress properties and elongation at break were measured again as specified in b) and d) above.

[0061] The following Table 1 details the formulations of compositions C1-C3 and 11-15 prepared as indicated above. [Tables 1] Cl C2 C3 II 12 13 14 15 EPDM 1 * 60 60 60 60 60 60 60 60 EPDM 2 * 40 40 40 40 40 40 40 40 Virgin carbon black * 57.5 115 38.3 19.2 76.6 19.2 Lignin * 57.5 115 38.3 76.6 57.5 19.2 19.2 Recycled carbon black * 38.3 19.2 57.5 19.2 76.6 Plasticizer * 40 40 40 40 40 40 40 40 MgO 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 PEG 4000 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 Processing agent * 3 3 3 3 3 3 3 3 Quinoline antioxidant 1 1 1 1 1 1 1 1 Imidazole antioxidant 1 1 1 1 1 1 1 1 TAC co-agent 1 1 1 1 1 1 1 1 Organic bis-peroxide 10.5 10.5 10.5 10.5 10.5 10.5 10.5 10.5 TOTAL 279.1 279.1 279.1 279.0 279.1 279.1 279.1 279.1 Mass fractions in sustainable ingredients 20% 0% 41% 27% 34% 41% 14% 34%

[0062] The ingredients used for these compositions identified in Table 1 by the sign * had the following characteristics: - EPDM 1: mass content of ethylene units of 55%, ethylidene norbornene units of 5.5%, and Mooney viscosity ML(l+4) at 125°C of 80. - EPDM 2: mass content of ethylene units of 68%, ethylidene norbornene units of 4.9%, and Mooney viscosity ML(l+4) at 125°C of 85. - Virgin carbon black: grade 6, BET specific surface area according to ASTM D 6556 of 20 m2 / g, and iodine adsorption index according to ASTM D 1510 of 20 mg / g. - lignin: kraft lignin from gymnosperm tree wood, such as conifers, marketed by UPM under the reference TSD020-1000. - Recycled carbon black: produced from the pyrolysis of used tires and marketed by Contée under the name Conblack®. - Plasticizer: paraffinic mineral oil. - Implementing agent: mixture of fatty acid derivatives.

[0063] Table 2 below presents the essential rheological properties of the compositions obtained C1-C3 and 11-15, comprising for each of them: - the Mooney viscosity ML(l+4) at 100°C, measured according to ISO 289-1; - the initial roasting time t5 without premature crosslinking, at 135°C according to ISO 289-2; and - rheological properties: times tsl and tlO, t50, t70, t90 (start to end of crosslinking) measured by an oscillating matrix rheometer (20 min. at 180°C) according to ISO 6502 standard. [Tables 2] Cl C2 C3 II 12 13 14 15 ML(l+4) at 100° C 99.3 97.2 109.8 94.3 99.6 104.1 97.5 97.3 Roasting time t5 in min. (30 min. at 135° C) 12.74 13.28 10.65 13.03 12.74 10.35 12.17 10.80 Rheology: time in min. (20 min. at 180°C) tsl 0.61 0.57 0.62 0.54 0.59 0.58 0.52 0.50 tlO 0.64 0.66 0.67 0.60 0.64 0.63 0.58 0.57 t50 1.74 1.96 1.76 1.68 1.73 1.66 1.69 1.63 t70 2.83 3.15 2.82 2.77 2.81 2.74 2.80 2.74 t90 5.4 5.87 5.3 5.37 5.34 5.35 5.48 5.37

[0064] Table 3 below shows the physical and mechanical properties of the obtained crosslinked compositions C1-C3 and 11-15, measured as indicated above on dumbbell-type test pieces. [Tables 3] Cl C2 C3 II 12 13 14 15 Density (g / cm3) 1.109 1.162 1.063 1.133 1.098 1.116 1.150 1.154 Before thermo-oxidative aging Shore A hardness 64 65 65 66 65 66 66 66 Tensile strength (MPa) 9.21 13.4 6.72 8.46 7.04 7.54 9.82 9.33 Elongation at break (%) 323 310 248 302 260 278 260 278 M100 modulus (MPa) 3.88 3.78 3.97 3.46 3.51 3.45 3.94 3.40 After thermo-oxidative aging for 168 h at 150° C Shore A hardness 66 71 67 71 68 71 71 74 A Shore A hardness +2 +6 +2 +5 +3 +5 +5 +8 Tensile strength (MPa) 8.78 12 7.09 7.31 6.68 6.41 8.57 7.62 A (%) tensile strength -5% -10% 6% -14% -5% -15% -13% -18% Elongation at break (%) 195 265 155 138 143 118 161 127 A (%) elongation at break -40% -15% -38% -54% -45% -58% -38% -54% Compression set (CST) 25%: 72 h / 130°C after 30 min. according to ISO 815-1 (method B) 27.4 28.4 28.7 48.3 48.5 71.2 30.1 31.5 25%: 72 h / 140°C “FCA” according to ISO 1817 38.9 43.0 39.1 54.0 52.7 88.2 40.1 44.2 Volume resistivity at 1000 V In Q.cm 6.4.10 13 1.5.106 4.9.10 13 7.2.10 13 5.8.10 13 6.1.10 13 3.2.10 12 6.2.10 13

[0065] All of the properties obtained in Tables 2-3 for compositions 11-15 according to the invention show, in comparison with the control composition C1 (comprising as reinforcing filler a mixture of 50% of the same virgin carbon black and 50% of the same lignin): - in the non-crosslinked state, a generally preserved suitability for use for compositions 11-15 and even improved for II, 12, 14 and 15 (see in particular their reduced viscosity ML(l+4) compared to that of composition Cl); and - in the crosslinked state: mechanical properties generally preserved (even after thermo-oxidative aging) for compositions II, 14 and 15, or even partly improved for composition 14 (see in particular the breaking stress and the M100 modulus before aging of composition 14 which are increased compared to those of composition Cl, as well as the DRC of composition 14 which are of the same order as those of composition Cl), and a resistivity generally preserved for compositions 11-15, or even improved for composition II.

[0066] The properties obtained for compositions 11-15 according to the invention show, in comparison with composition C 2 not in accordance with the invention (comprising as reinforcing filler 100% of the same virgin carbon black): - in the non-crosslinked state, a generally preserved suitability for use for compositions 11-15 and even improved for II (see in particular its viscosity ML(l+4) reduced compared to that of composition C2); and - in the crosslinked state: mechanical properties not too penalized (even after thermo-oxidative aging) for compositions II, 14 and 15, or even partly improved for composition 14 (see in particular the M100 modulus of composition 14 which is increased compared to that of composition C2, as well as the DRC of compositions 14 and 15 which are of the same order as those of composition C2, or even reduced for composition 14 at 72 h / 140° C), and a very clearly improved resistivity for compositions 11-15.

[0067] The properties obtained for compositions 11-15 according to the invention show, in comparison with composition C 3 not in accordance with the invention (comprising as reinforcing filler 100% of the same lignin): - in the uncrosslinked state, a very clearly improved suitability for use for compositions 11-15 (see in particular their viscosities ML(l+4) which are very reduced compared to that of composition C3 and their roasting times t5 which are generally higher compared to those of composition C3); and - in the crosslinked state: overall improved mechanical properties even after thermooxidative aging for compositions 11-15 (see in particular the stresses and elongations at break, as well as the DRCs of compositions 14 and 15 which are of the same order as those of composition C3), and improved resistivity for compositions II, 12, 13 and 15.

[0068] In conclusion, these examples show that: - compositions 11-15 according to the invention, in particular characterized by the coupling of a recycled carbon black to lignin, generally have properties in the non-crosslinked and crosslinked state of the same order as compositions C1-C3, and in particular that - compositions II, 12, 14 and 15, further characterized by the addition of a virgin carbon black to the recycled carbon black and to the lignin, even make it possible to further improve some of these properties compared to those of compositions C1-C3, with even more particularly - compositions 14 and 15, specifically further characterized by a mass fraction of lignin in the reinforcing filler of approximately 17%, make it possible to further improve certain of these properties compared to compositions C1-C3 (in comparison with compositions II and 12, the reinforcing filler of which comprises approximately 33% and 67% lignin, respectively).

[0069] These examples also show that the compositions according to the invention II, 12, 13 and 15 advantageously have a mass fraction of sustainable ingredients (i.e. biosourced and recycled) which is greater than 25%, or even greater than 30% (compositions 12, 13 and 15) and even greater than 40% (composition 13).

Claims

Claims

1. Rubber composition based on at least one elastomer, the composition being usable for forming in the crosslinked state at least one layer of a pipe and comprising a reinforcing filler and a crosslinking system comprising sulfur and / or a peroxide, in which the reinforcing filler comprises at least one recycled carbon black from grinding and thermal decomposition of used rubber-based articles, and a functionalized lignin in powder form.

2. A rubber composition according to claim 1, wherein said at least one recycled carbon black has composition reinforcing properties similar to those of a reinforcing carbon black selected from the ASTM N300, N400, N500, N600 and N700 series, for example similar to those of an N500 or N600 series carbon black.

3. Rubber composition according to one of the preceding claims, in which the composition comprises, in addition to said at least one elastomer, the crosslinking system and the functionalized lignin: a recycled powder mixture which comprises the product of a thermal decomposition reaction, by thermolysis, pyrolysis or devulcanization, applied to a ground material of said used rubber-based articles, the recycled powder mixture comprising said at least one recycled carbon black and being for example micronized, in particular in the case where said reaction is a thermolysis or a pyrolysis.

4. Rubber composition according to one of the preceding claims, in which the recycled powder mixture comprises said at least one recycled carbon black in a mass fraction of between 80% and 99%, and inorganic substances in a mass fraction of between 1% and 20% comprising in particular silicon oxides and / or zinc compounds, the recycled powder mixture in micronized form being for example derived from the pyrolysis of used tires.

5. Rubber composition according to one of the preceding claims, in which the functionalized lignin in powder form: - comprises particles devoid of CO or COO groups on the surface, and / or - is a kraft lignin, for example derived from the wood of gymnosperm trees, such as conifers.

6. Rubber composition according to one of the preceding claims, in which the reinforcing filler further comprises at least one virgin carbon black, having for example a BET specific surface area measured according to standard ASTM D 6556 which is between 10 and 50 m2 / g.

7. Rubber composition according to one of the preceding claims, wherein the composition comprises 10-120 phr of said at least one recycled carbon black and 2-90 phr of functionalized lignin (phr: parts by weight per 100 parts of elastomer(s)).

8. Rubber composition according to one of the preceding claims, wherein said at least one elastomer is chosen from ethylene-propylene-diene terpolymers (EPDM), isobutylene-isoprene copolymers (IIR), halogenated isobutylene-isoprene copolymers (XIIR), silicone rubbers, fluorinated silicone rubbers, acrylic rubbers of the polyacrylate (ACM) and ethylene polyacrylate (AEM) type, and brominated isobutylene-para-methylstyrene copolymers.

9. Rubber composition according to claims 7 and 8, wherein: - said at least one elastomer consists of at least one EPDM, - the crosslinking system comprises a peroxide or sulfur, and - the composition comprises 15-100 phr of said at least one recycled carbon black and 5-80 phr of functionalized lignin.

10. A rubber composition according to claims 6 and 9, wherein the composition comprises: - 10-80 phr of said at least one virgin carbon black, having for example a BET specific surface area measured according to ASTM D 6556 which is between 10 and 50 m2 / g, - 15-80 phr of said at least one recycled carbon black, and - 15-80 phr of said functionalized lignin, with the sum of the amounts of said at least one virgin carbon black and said at least one recycled carbon black in the composition being 60-110 phr.

11. The rubber composition of claim 10, wherein the sum of the amounts of said at least one virgin carbon black and said at least one recycled carbon black in the composition is 70-100 phr, and wherein the sum of the amounts of said at least one virgin carbon black, said at least one recycled carbon black and said functionalized lignin in the composition is 100-130 phr.

12. Rubber composition according to claim 10 or 11, wherein the reinforcing filler comprises: - functionalized lignin according to a mass fraction of 15-30%, and - said at least one virgin carbon black and said at least one recycled carbon black according to a total mass fraction of carbon black of 70-85%.

13. Rubber composition according to one of claims 9 to 12, in which the composition has in the crosslinked state a volume resistivity greater than 106 Ohm.cm, preferably greater than 108 Ohm.cm, measured according to standard IEC 62631 3.

14. A rubber composition according to any preceding claim, wherein the composition has a mass fraction of sustainable ingredients, which include said at least one recycled carbon black and said functionalized lignin, which is greater than 25%, preferably greater than 30%, for example equal to or greater than 40%.

15. Pipe for transferring a liquid, gaseous or supercritical fluid for a thermal or electric engine or for a fuel cell of a motor, rail, aquatic, air or space vehicle, the pipe comprising a radially internal tube, at least one reinforcing layer and a cover layer, the pipe being adapted to convey the fluid at a pressure equal to or greater than 2.105 Pa, in which at least one of the internal tube and the cover layer is made of a rubber composition in the crosslinked state according to one of the preceding claims.

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