Composition of vitrimer-type polymer network and use in tank manufacturing

Abstract

The present invention relates to a polymer network composition comprising at least one polymer network including several interatomic bonds whose distribution within the polymer network is capable of varying and at least one catalyst capable of promoting exchange reactions within the polymer network; said composition being ductile at a temperature of 0°C and exhibiting creep resistance at a temperature greater than or equal to 0°C.

Description

Title of the invention: Vitrimer-type polymer network composition and use for the manufacture of reservoirs

[0001] The present invention relates to a vitrimer-type polymer network composition, as described below, for use in the manufacture of tanks, in particular fuel tanks, especially fuel tanks in motor vehicles, preferably in plug-in hybrid motor vehicles.

[0002] The invention also relates to a tank, preferably a fuel tank for a plug-in hybrid motor vehicle, obtained from at least one vitrimer-type polymer network composition as defined below.

[0003] Fuel tanks used in plug-in hybrid electric vehicles (PH-EVs) are generally subjected cyclically to high internal pressures, for example up to 400 mbar, particularly in certain all-electric driving modes, as well as to significant increases and / or fluctuations in temperature.

[0004] Thus, fuel tanks for plug-in hybrid motor vehicles are subject to demanding specifications in terms of resistance to damage, in particular due to pressure and heat, and must therefore have improved mechanical properties compared to fuel tanks for conventional internal combustion engines.

[0005] Indeed, traditional tanks, such as multilayer tanks obtained by blowing polyethylene (PE), usually have difficulty withstanding the pressure and heat conditions generally observed in plug-in hybrid motor vehicles without being deformed in a non-negligible way, most often irreversibly, under the action of fining phenomena over time.

[0006] In order to overcome such drawbacks, solutions consisting of implementing fuel tanks from thermoplastic polymers, such as polyamides or polyolefins, such as cross-linked high-density polyethylene (HDPE), or from thermosetting polymers, such as epoxy (or polyepoxide) resins or polyurethanes, have already been proposed.

[0007] However, tanks obtained from polyamides have the disadvantage of being sensitive to external aggressions, such as humidity, and to chemical aggressions, for example to de-icing salts.

[0008] Tanks made from cross-linked high-density polyethylene, on the other hand, exhibit mechanical properties that can prove unsatisfactory. In particular, such tanks are still too sensitive to brittleness and suffer a significant loss of their cold impact resistance. Indeed, the permanent covalent bonds present within cross-linked high-density polyethylene make them too fragile for the intended application. Furthermore, tanks made from such cross-linked polyolefins are not recyclable, which results in high costs when they are replaced or when they age.

[0009] Finally, to obtain a crosslinked polyolefin reservoir, the part initially produced from uncrosslinked polyolefin must be subjected to a treatment, usually under radiation or with the aid of peroxides, to achieve crosslinking. Such a process is costly and does not allow for uniform crosslinking of all polymer chains, leaving a large fraction of uncrosslinked polymer.

[0010] Besides this, tanks obtained from thermosetting polymers, such as epoxies (or polyepoxies) or polyurethanes, have the disadvantages of being weakly resistant to impacts, difficult to reshape in case of cracks and not being able to be recycled, especially at the end of the vehicle's life.

[0011] Indeed, given that the chemical reactions leading to the formation of polyepoxides or polyurethanes are irreversible, tanks made from such thermosetting polymers cannot be remelted, meaning they cannot be repaired if cracked or reshaped for a second life. In particular, the risk of cracking is linked to the high density of crosslinking within thermosetting polymers, and crack propagation is favored by their low ductility, especially in the case of polyepoxides.

[0012] In addition, thermosetting polymers are difficult to implement for obtaining fuel tanks due to their low deformability.

[0013] Conversely, ductility is a property that appears particularly in semi-crystalline polymers between the glass transition temperature (Tg) and the melting temperature (Tm).

[0014] In view of the foregoing, one of the objectives of the present invention is therefore to improve the mechanical properties of fuel tanks, in particular fuel tanks used in plug-in hybrid motor vehicles, while overcoming the difficulties related to their recycling, remodeling and implementation.

[0015] In other words, one of the aims of the present invention is to provide a material capable of improving the mechanical properties of fuel tanks, particularly those used in plug-in hybrid vehicles, while ensuring their recyclability and / or their remodeling, particularly at the end of the life of the motor vehicle, and their ease of implementation.

[0016] In particular, the invention aims to provide a fuel tank, in particular a fuel tank for a plug-in hybrid motor vehicle having improved mechanical properties, in particular having better resistance to pressure over time, better thermal and / or chemical resistance, while being recyclable or remodelable for later use.

[0017] The present invention therefore relates in particular to a polymer network composition comprising at least one polymer network including several interatomic bonds whose distribution within the polymer network is capable of varying and at least one catalyst capable of promoting exchange reactions within the polymer network; said composition being ductile at a temperature less than or equal to 0°C and exhibiting resistance to fining at a temperature greater than or equal to 0°C.

[0018] The composition according to the invention can thus be likened to a dynamic network comprising several interatomic bonds capable of reorganizing themselves within the polymer network under the effect of internal exchange reactions without changing the number of covalent bonds, nor depolymerizing.

[0019] The composition according to the invention thus makes it possible to remedy the aforementioned drawbacks, in particular by leading to fuel tanks, preferably used in plug-in hybrid vehicles, having improved mechanical properties, in particular having improved resistance to fining including under high pressure and temperature conditions.

[0020] The composition according to the invention also makes it possible to increase the pressure resistance, thermal resistance and chemical resistance, including over time, of fuel tanks.

[0021] In addition, the composition according to the invention makes it possible to improve the weldability of fuel tanks, in particular the resistance to fining of the weld areas of fuel tanks.

[0022] In other words, the composition according to the invention makes it possible to make the welding areas of fuel tanks more resistant.

[0023] The composition according to the invention also makes it possible to reduce the risks of degradation by stress cracking, in particular caused by pressure and / or thermal stress, and by environmental stress cracking, for example related to chemical aggression, of fuel tanks.

[0024] Preferably, the composition according to the invention makes it possible to protect the tank against cracks caused by pressure and / or thermal stress, more preferably by pressure stress.

[0025] Furthermore, the composition according to the invention makes it possible to produce tanks that are recyclable or remoldable for subsequent use, including at the end of the plug-in hybrid vehicle's life. In particular, in the event of a crack, tanks obtained from the composition according to the invention are more easily repaired than tanks obtained from thermosetting polymers.

[0026] The composition according to the invention also makes it possible to induce self-repairing properties in the tanks.

[0027] The composition according to the invention also has the advantage of being able to adapt easily to any type of implementation, for example by extrusion, extrusion blow molding, injection molding.

[0028] Furthermore, when obtaining the tank from the composition, in particular by extrusion blow molding or by injection molding, it is possible to regrind and reuse production waste and scrap such as injection cores and parison residues.

[0029] The composition according to the invention has a ductility making it particularly suitable for use in the manufacture of at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0030] Another object of the present invention also relates to the use of said composition for the manufacture of at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0031] As previously stated, the composition advantageously makes it possible to improve the mechanical properties, preferably the resistance to fining, more preferably the resistance to pressure, of at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0032] In particular, the use of the composition according to the invention makes it possible to prevent cracks within a tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0033] The use of the composition according to the invention also makes it possible to protect at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle, against chemical attack.

[0034] The invention also relates to a tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle, obtained from at least the composition according to the invention, as defined above.

[0035] The tank according to the invention thus exhibits improved mechanical properties, thermal resistance and chemical resistance, including over time.

[0036] The tank according to the invention advantageously has one or more weld zones whose resistance to fining is improved.

[0037] In other words, the mechanical strength of the tank according to the invention, including its weld area(s), is improved.

[0038] Other objects, features, aspects and advantages of the invention will become even clearer upon reading the description and examples that follow.

[0039] In what follows, and unless otherwise indicated, the bounds of a range of values ​​are included in that range, in particular in the expressions "between" and "ranging from... to...".

[0040] Furthermore, the expressions "at least one" and "at least" used in this description are respectively equivalent to the expressions "one or more" and "greater than or equal to". Composition

[0041] As previously stated, the composition according to the invention can be considered a dynamic network in which the interatomic bonds are interatomic links whose distribution within the polymer network can vary under the effect of internal exchange reactions, without the average number of covalent bonds changing. The interatomic bonds that can vary are called exchangeable and are distinguished from so-called reversible bonds by the fact that the latter break and reform when the temperature is raised or lowered, respectively, whereas for exchangeable bonds, the role of temperature is only to accelerate the exchanges without changing the number of bonds.

[0042] In other words, the interatomic bonds are located on the strands of the polymer network and are capable of reorganizing themselves under the effect of internal exchange reactions, facilitated by the presence of at least one catalyst, within the polymer network.

[0043] Thus the distribution of interatomic bonds within the polymer network can vary under the effect of internal exchange reactions without changing the degree of crosslinking of the polymer network.

[0044] In other words, the dynamic network can be likened to a chemically cross-linked polymer network whose topology can be modified, but which nevertheless remains insoluble in a solvent that is both a good solvent and non-reactive. By good solvent, we mean that the same uncross-linked polymer is soluble in this solvent at room temperature, for example, from 20 to 37°C, or at a higher temperature. By non-reactive, we mean that this solvent is not capable of breaking any of the network's bonds.

[0045] Thus the composition according to the invention is in particular a vitrimer-type polymer network, i.e. meeting the definition mentioned above.

[0046] For the purposes of the present invention, interatomic bonds are dynamic and exchangeable bonds forming interatomic links within the polymer network.

[0047] In other words, the interatomic bonds present in the composition are not permanent covalent bonds.

[0048] However, the presence of fuel, which can be considered a non-reactive solvent, is not likely to affect interatomic bonds.

[0049] Thus, the presence of fuel, which can be likened to a non-reactive solvent, in contact with the network may cause the partial dissolution of molecular fragments accidentally not connected to the rest of the network but is not such as to cause the dissociation of the network.

[0050] The fraction of molecular fragments not bound to the network, called the sol fraction or soluble fraction, should preferably be as small as possible. The fraction constituting the main network, called the gel fraction or insoluble fraction, should preferably be as large as possible.

[0051] The existence of a soluble fraction is linked to network imperfections formed during its synthesis. Typically, exchangeable link networks obtained by radical grafting exhibit insoluble fractions ranging from 30% to 66%.

[0052] Interatomic bonds can be chosen from the group consisting of ethylenic double bonds -C=C-, ester bonds -COO-, amide bonds -CONH-, -, urethane vinylogun bonds -OOC-CH=C-NH-, imine bonds -C=N-, hydrazone bonds -C=N-NH-, oxime bonds -C=NO-, aldol bonds -C(OH)-C(CHO)-, allylic ester bonds -COO-CH2-C=C-, thioester bonds -COS-, acetal and hemiacetal bonds -OC(OR'), siloxane bonds -Si-O-Si, sulfonate bonds -SOC, disulfide bonds -SS-, and sulfate bonds.

[0053] Preferably, the interatomic bonds are chosen from the group consisting of ethylenic double bonds -C=C-, ester bonds -COO- and amide bonds -CONH-.

[0054] More preferably, the interatomic bonds are chosen from the group consisting of ethylenic double bonds -C=C- and ester bonds -COO-.

[0055] Even more preferably, the interatomic bonds are ester -COO- bonds.

[0056] Interatomic bonds can undergo exchangeable reactions such as those selected from the group consisting of transesterification reactions, transcarbonation, transcarbamoylation exchange of methanes, transamination of imines, transamination of vinyl urethane, silyl ether exchange, oxime-promoted transesterification, olefin metathesis, boronic ester-based bond exchange, disulfide-based radical reaction.

[0057] Preferably, the interatomic bonds undergo transesterification reactions.

[0058] More preferably, the covalent interatomic bonds are ester bonds -COO- and undergo exchange reactions, in particular transesterification reactions.

[0059] Preferably, the polymer network has an enthalpy of fusion greater than or equal to 5 J / g measured by DSC.

[0060] The composition according to the invention comprises a polymer network that can be obtained from at least one semi-crystalline polymer.

[0061] Preferably, the semi-crystalline polymer has a glass transition temperature below -40°C and even more preferably below -70°C.

[0062] Preferably, the semi-crystalline polymer is chosen from the group consisting of polyethylene, propylene, thermoplastic polyamides, thermoplastic polyimides, polyethylene terephthalate, polybutylene terephthalate, polyethylene oxide, ethylene copolymers such as ethylene vinyl alcohol (EVOH), ethylene vinyl acetate copolymers (EVAc), ethyl acrylate, ethylene butyl acrylate, poly(ethylene-co-glycidyl methacrylate), more preferably, the semi-crystalline polymer is based on polyethylene or polypropylene.

[0063] Preferably, the semi-crystalline polymer is a polyolefin copolymer comprising between 0.5 mol% and 2 mol% of comonomers bearing carboxylic functions such as acrylates, methacrylates, itaconates, maleic anhydride.

[0064] Preferably the copolymer as described above statistically comprises less than 6% by number of chains devoid of co-monomer bearing carboxylic functions, even more preferably less than 3%.

[0065] In the case of a statistical copolymer such as Lotader comprising an olefinic monomer and a functional comonomer, the number of chains lacking a functional comonomer can be evaluated using the experimental mass distribution curve (obtained by size exclusion chromatography) and the binomial law [cf Ricarte et al. Macromolecules 2019, 52, 432-443, supporting information pages S7-S9].

[0066] Preferably, the semi-crystalline polymer is chosen from the group consisting of ethylene copolymers, in particular ethylene and methacrylic acid and glycidol ester copolymers.

[0067] More preferably, the semi-crystalline polymer is poly(ethylene-co-glycidyl methacrylate).

[0068] In particular, poly(ethylene-co-glycidyl methacrylate) corresponds to the following formula:

[0069] Preferably, the composition according to the invention comprises a polymer network that can be obtained from poly(ethylene-co-glycidyl methacrylate) as sold under the trade name Lotader AX8840 or AX8820.

[0070] In other words, the polymer network comprises several polymeric fragments preferably obtained from one or more semi-crystalline polymers as defined above.

[0071] The catalyst(s) is or are capable of promoting exchange reactions such as those chosen from the group described above.

[0072] Preferably, the catalyst(s) is or are capable of promoting transesterification reactions.

[0073] The catalyst(s) are chosen from the group consisting of organic, inorganic, metallo-organic catalysts and their mixtures.

[0074] The catalyst(s) are preferably chosen from the group consisting of organic, inorganic, metallo-organic catalysts and their mixtures, preferably organic, such as nitrogen bases and guanidines, metallic catalysts, such as organic acid salts of alkaline earth metals, organic acid salts of alkali metals, organic acid salts of transition metals, and their mixtures.

[0075] The catalyst(s) may be metallic catalysts, in particular organometallic complexes, inorganic metallic salts, organic metallic salts and mixtures thereof, more particularly organometallic complexes.

[0076] The catalyst(s) may be organic catalysts preferably chosen from nitrogenous bases such as DBU (diazabicycloundecene), DBN (diazabicyclononene), or from the guanidine family such as TMG (tetramethylguanidine), TBD (triazabicyclodecene), MTBD (methyltriazabicyclodecene) and mixtures thereof.

[0077] Preferably, the catalyst or catalysts is or are chosen from the group consisting of organic acid salts of alkali metals, organic acid salts of alkaline earth metals, organic acid salts of transition metals and mixtures thereof.

[0078] Preferably, the catalyst or catalysts is or are chosen from the group consisting of organic acid salts of alkaline earth metals, organic acid salts of transition metals, nitrogenous bases and mixtures thereof, in particular organic acid salts of transition metals and guanidines.

[0079] Preferably, the catalyst(s) is or are chosen from alkali metal salts, zinc salts, magnesium salts, calcium salts, titanium salts, zirconium salts, and mixtures thereof, more preferably zinc salts and / or TBD.

[0080] More preferably, the catalyst or catalysts is or are chosen from the group consisting of organic acid salts of potassium, cesium, zinc, in particular zinc carboxylic acid salts and / or TBD.

[0081] Preferably, the content of the catalyst varies from 25% to 200% by moles (corresponding to 0.25 to 2 molar equivalents) with respect to the reactive functions present in the polymer network.

[0082] Preferably, the composition according to the invention comprises at least one polymer network that can be obtained from a semi-crystalline polymer selected from the group consisting of ethylene copolymers, and at least one metal catalyst, preferably selected from the group of organic acid salts of alkaline earth metals, organic acid salts of transition metals and their mixtures, in particular organic acid salts of transition metals.

[0083] More preferably, the composition according to the invention comprises at least one polymer network that can be obtained from at least one polymer selected from the group consisting of ethylene copolymers, more preferably ethylene and methacrylic acid and glycidol ester copolymers, in particular poly(ethylene-co-glycidyl methacrylate) and comprising at least one metal catalyst, preferably selected from the group consisting of organic acid salts of transition metals.

[0084] Preferably, the polymer is chosen from the group consisting of ethylene and methacrylic acid and glycidol ester copolymers, in particular poly(ethylene-co-glycidyl methacrylate) comprising 0.5 mol to 2 mol% of methacrylic comonomer and the content of the catalyst varies from 25% to 200% by moles (corresponding to 0.25 to 2 molar equivalents) with respect to the reactive functions, preferably the epoxy functions, present in the polymer network.

[0085] As previously stated, the composition according to the invention is ductile at a temperature less than or equal to 0°C and exhibits high resistance to fining at a temperature greater than 0°C.

[0086] Preferably, the composition according to the invention is ductile at a temperature less than or equal to -10°C, better less than or equal to -20°C, even better less than or equal to -30°C.

[0087] The composition according to the invention exhibits high resistance to fining at a temperature greater than or equal to 0°C, preferably greater than or equal to +30°C, preferably measured at a temperature greater than or equal to +35°C, more preferably measured at a temperature greater than or equal to +40°C.

[0088] By resistance to shaping, in the context of the present invention, means that when the composition is shaped to obtain a mechanical part, in particular an automotive part, preferably a tank, more preferably a fuel tank, the deformation, measured at a temperature greater than or equal to 0°C, under a pressure of 400 mbar, is less than 15 mm, preferably less than or equal to 10 mm, for in particular 1000 hours.

[0089] Deformation can in particular be measured using deformation sensors.

[0090] The composition exhibits stable resistance to fining over time, i.e., the deformation remains stable for several days, whether after several stress cycles or return to atmospheric pressure (i.e., after stopping the stress).

[0091] The composition according to the invention has in particular a high resistance to fining measured at a temperature ranging from 0°C to 180°C, more preferably from 0°C to 100°C, even better from 35°C to 100°C.

[0092] More preferably, the composition according to the invention is ductile at a temperature less than or equal to -40°C while exhibiting high resistance to fining beyond that at temperatures of +35°C (in other words, at temperatures greater than or equal to 35°C).

[0093] Ductility is measured by an elongation rate just before necking during a tensile test at a temperature less than or equal to 0°C, preferably less than or equal to -40°C, measured in particular by the Charpy method.

[0094] In particular, at 100°C, the composition according to the invention does not relax the stress resulting from an imposed 2% shear strain. However, at a temperature above 170°C, the composition is capable of relaxing the stresses after a period exceeding 1000 seconds, and particularly 50% of the initial stress is relaxed after a period of 16 hours, regardless of the temperature tested between 170°C and 200°C, while maintaining its modulus of elasticity.

[0095] According to a preferred general feature, the composition according to the invention comprises at least an insoluble fraction of at least 70% by weight in a solvent that is both a good solvent and non-reactive, relative to the total weight of the composition.

[0096] Preferably, the composition according to the invention comprises at least an insoluble fraction of at least 80% by weight, more preferably of at least 85% by weight, even more preferably of at least 90% by weight, relative to the total weight of the composition.

[0097] By insoluble fraction, for the purposes of the present invention, means the gel content within the composition which does not dissolve in a good non-reactive solvent during a polymer network swelling test.

[0098] A good non-reactive solvent could be, for example, xylene at 125°C.

[0099] The solvent swelling test is a classic test known to a man of the job.

[0100] The swelling test can be carried out by mixing 0.2 g of a sample in 40 mL of xylene and 1.5 g of BHT, as an antioxidant, in a round-bottom flask under reflux at a temperature of 125°C for 24 hours. The solvent is then removed and the swollen sample is weighed using a precision balance. The sample is then dried under vacuum at a temperature of 140°C for 12 hours and weighed again.

[0101] Apart from this desirable property of insolubility in a non-reactive solvent such as xylene, representative of chemical resistance to contact with the fuel, it is also desirable for the purposes of disassembly at the end of the tank's life and chemical recycling of the material that the composition can be redissolved in a reactive solvent or mixture of solvents.

[0102] The reactive solvent mixture can be, for example, a xylene / butanol mixture at 150°C.

[0103] The redissolution test in a reactive solvent mixture can be carried out by mixing 0.2 g of the sample with a mixture of 30 mL of xylene + 15 mL of butanol and 0.3 g of an organic transesterification catalyst such as triazabicyclodecene (TBD). The test is performed using a digestion bomb, at 150°C under magnetic stirring, for a duration of 24 hours.

[0104] Preferably, the composition according to the invention has a crosslinking density greater than or equal to 1.2.104 mol / cm3, measured during a swelling test as described above. Use of the composition

[0105] As previously stated, the invention also relates to the use of at least one composition, as defined above, for the manufacture of au minus one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0106] Preferably, the invention relates to the use of the composition, as defined above, for the manufacture of at least one fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0107] In particular, the composition according to the invention can be used to manufacture all or part of a tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0108] More preferably, the invention relates to the use of the composition, as defined above, to improve the mechanical properties, preferably the pressure resistance, of at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle.

[0109] The invention also relates to the use of said composition for the protection of at least one tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle, against chemical attack. Composition preparation process

[0110] The present invention also relates to a method for preparing a composition according to the invention comprising: (i) at least one mixing step of at least one polymer, as defined above, at least one crosslinking agent, and at least one catalyst as defined above, ii) at least one shaping step of the mixture obtained in step i) at a temperature Ti strictly above the melting temperature Tm of said polymer and below the curing temperature T2 of said mixture, iii) at least one curing step of said mixture to obtain the composition according to the invention.

[0111] The polymer(s) and catalyst(s) implemented during step i) are as defined previously.

[0112] Preferably, the polymer(s) are semi-crystalline, in particular chosen from the group consisting of ethylene copolymers, in particular ethylene and methacrylic acid and glycidol ester copolymers.

[0113] Preferably, the catalyst or catalysts is or are chosen from the group consisting of metal salts, in particular organic acid salts of alkali metals, organic acid salts of alkali or alkaline earth metals, organic acid salts of transition metals, organic catalysts, and mixtures thereof.

[0114] Preferably, the catalyst or catalysts is or are chosen from zinc salts, potassium salts, cesium salts, tin salts, zinc salts, magnesium salts, calcium salts, titanium salts, zirconium salts, organic catalysts and mixtures thereof, more preferably zinc salts and guanidines.

[0115] The crosslinking agent(s) may be chosen from compounds conforming to the following formula:

[0116] HOOC-R-COOH (I)

[0117] Formula (I) in which: R represents a hydrocarbon chain, linear or branched, saturated or unsaturated, cyclic or acyclic, preferably cyclic and / or branched, in Ci_36.

[0118] Alternatively, the crosslinking agent(s) may be a mixture of at least one compound corresponding to formula (I), as described above, and at least one compound corresponding to formula (II): R'-COOH with R' having the same meaning as R in formula (I).

[0119] The polymer(s), the crosslinking agent(s), the catalyst(s) can be mixed sequentially or simultaneously (i.e., all at once) during step i).

[0120] Preferably, the polymer(s), the crosslinking agent(s), the catalyst(s) are mixed in a mixing extruder, for example a DACA twin-screw mixing extruder or any other type of commercially available extruder.

[0121] Preferably, the shaping step ii) is an extrusion of the mixture obtained during step i) at a temperature Ti; the temperature Ti being strictly greater than the melting temperature Tf of said polymer and less than the curing temperature T2 of said mixture.

[0122] At the end of the shaping step ii), a polymeric mixture is obtained in which said polymer, said crosslinking agent and said catalyst have not reacted with each other.

[0123] In other words, at the end of steps i) and ii), the mixture has not undergone cross-linking.

[0124] The polymeric mixture thus obtained is in the form of a viscous liquid.

[0125] In other words, the exchangeable covalent bonds of the polymer network do not do not form at the end of steps i) and ii).

[0126] Preferably, the temperature Ti varies from 104°C to a temperature below 130°C, in particular 115°C.

[0127] During step iii), the mixture obtained in step ii) hardens, i.e. the reactive groups of the polymer react with the crosslinking agent(s).

[0128] Preferably, step iii) takes place at a temperature T2 varying from 140°C to 360°C, more preferably varying from 140°C to 300°C, even more preferably varying from 140°C to 260°C, in particular the temperature T2 is equal to 150°C.

[0129] Preferably, step iii) is carried out by blowing or injection.

[0130] Following step iii), the process according to the invention may include at least one step (iv) of cooling the composition according to the invention. Reservoir

[0131] The invention also relates to a tank, in particular a fuel tank, preferably a fuel tank for a plug-in hybrid motor vehicle, obtained from at least the composition according to the invention, as defined above.

[0132] Preferably, the reservoir is obtained from a polymer network composition comprising at least one polymer network including several exchangeable covalent bonds selected from the group consisting of -COO- ester bonds and at least one catalyst capable of promoting transesterification reactions within the polymer network.

[0133] Preferably, the polymer network is obtained from at least one ethylene copolymer, in particular ethylene and methacrylic acid and glycidol ester copolymers.

[0134] Preferably, the reservoir is obtained with a composition, as defined above, which is preferably ductile at a temperature less than or equal to -40°C.

[0135] Preferably, the reservoir is obtained with a composition, as defined above, which is preferably ductile at a temperature less than or equal to -40°C and exhibits a resistance to fining greater than or equal to 35°C.

[0136] Preferably, the resistance to fining of the tank is raised at a temperature of 35°C, in particular exhibits a deformation of less than 15 mm, preferably less than 10 mm under a pressure of 400 mbar, measured for 1000 hours.

[0137] The resistance to corrosion of a fuel tank obtained with a composition according to the invention can, for example, be measured according to the following protocol: a. mounting of a tank, for example filled with 7L of fuel, on a frame in vehicle position with its components (for example with piping, canister, etc...) and installation of one or more sensors intended to measure the deformation under the gauge pump module (i.e. under the tank), b. After zeroing the sensors, the tank is placed in an oven at a temperature of 45 °C and the displacement of the sensors due to tank deformation is continuously recorded, along with the temperature and the internal tank pressure until sensor displacement stabilizes at + / -0.1 mm c. Removal of the oven tank and depressurization of the system, stabilization of the system for three days at a temperature of 20°C, then recording of the residual displacement of the sensors, d. Repeat step b) with a new 7L of fuel, record the deformation and verify if the tank deformation stabilizes at the same values, e. repetition of cycles until the deformation stabilizes.

[0138] The tank according to the invention has a deformation of less than 15 mm, measured at a temperature greater than or equal to 0°C, in particular at a temperature greater than or equal to +30°C under a pressure of 400 mbar.

[0139] The tank according to the invention has a deformation of less than 10 mm measured at a temperature greater than or equal to 0°C, in particular at a temperature greater than or equal to +30°C under a pressure of 400 mbar.

[0140] The invention is illustrated in more detail in the following non-limiting examples. Examples

[0141] The following examples serve to illustrate the invention without limiting it.

[0142] 1.1. Preparation of a zinc(II) carboxylate salt with a dicarboxylic acid In a beaker, 10 g of a fatty acid dimer, sold under the trade name Pripol® 1009, were mixed with 0.77 g of hydrated zinc acetate Zn(OAc)2 2H2O (corresponding to a molar ratio [Zn] / [COOH] of 0.10). The mixture was heated slowly from 100°C to 180°C, then left at 180°C for 4 hours with magnetic stirring to allow the acetic acid produced during the reaction and the water to leave the reaction medium.

[0143] The final mixture was then left under vacuum at a temperature of 180°C for one hour to eliminate any residual acetic acid.

[0144] A mixture of partially neutralized dicarboxylic acid with Zn2+ was thus obtained.

[0145] The sample will be designated A

[0146] 1.2. Size exclusion chromatography (SEC) analysis is performed using of an Agilent HT 220 device equipped with a refractometric detector and a stationary phase consisting of two PLgel Olexis columns (Agilent Technology). Elution is carried out at a temperature of 135°C using a mobile phase consisting of 1,2,4-trichlorobenzene (TCB) stabilized by 0.0125% of BHT (2,6-di-tert-butyl-p-cresol).

[0147] The initial copolymer (Lotader AX8840) is dissolved at a concentration of 3 mg per mL in TCB for 30 minutes at a temperature of 135°C. The calibration is based on a collection of standard polystyrene (PS) samples. Molar masses were determined using the universal calibration method, with the following Mark-Houwink parameters: KPS = 14.1 x 10⁵ dg / L and aPS = 0.7 for PS, and Kpe = 95.4 x 10⁵ dg / L and aPE = 0.640 for PE. The mass distribution curve is shown below. Binomial analysis, assuming perfectly statistical copolymerization, reveals that the mass fraction of chains lacking the methacrylic comonomer (GMA) is approximately 3%. The results are shown in Figure 1.

[0148] Figure 1 thus represents the mass fraction of methacrylic comonomers (GMA) on the polymer chain.

[0149] 1.3. Preparation of a vitrimer Samples containing dicarboxylic acid were prepared by extrusion in a DACA twin-screw mini-mixer.

[0150] 3 g of granules of a poly(ethylene-co-glycidyl methacrylate) (called P(E-co-GMA) Samples containing 8% by weight of glycidyl methacrylate (i.e., 1.71 mol%) were introduced via a hopper along with the dicarboxylic acid mixture (0.12 to 0.97 g), sample A. The rotor speed and temperature were set at 300 rpm and 115 °C, respectively, while the mixing time was set at 10 minutes. At the end of the residence time, the samples were extruded as a preheated mixture for further processing.

[0151] For the prepared composition, the DNx nomenclature is used, where x represents the percentage of carboxylic functionality relative to the epoxy.

[0152] All samples were then dried at 150 °C in an oven under an argon flow for 24h, before undergoing any further characterization (DMA, DSC, swelling test, stress relaxation, solubilization in a reactive solvent).

[0153] The compositions are shown in Table 1 below:

[0154] [Tables 1] Sample mass of P(E-co-GMA dicarbo xylic acid (DA) m mass of zinc salt DN25 3g 0.12 0.009g DN50 3g 0.24 0.018g DN75 3g 0.36 0.028g DN100 3g 0.48 0.037g DN200 3g 0.96 0.074g

[0155] 1.4. Monitoring of freezing

[0156] Rheological experiments were carried out to control the time dependence of the shear moduli of the formulated samples. The materials studied here were first obtained by extrusion and compressed into a cylindrical shape using a stainless steel mold (radius r = 25 mm, thickness 1.5 mm) at a temperature of 115°C, applying a pressure of 3 tonnes for 3 minutes.

[0157] The sol-gel transition of the discs thus obtained was monitored using an Anton Paar MCR501 rotary rheometer equipped with a parallel plate geometry of 25 mm. The upper and lower geometries are respectively made of a stainless steel plate and a disposable aluminum plate.

[0158] To minimize thermal degradation, the plate geometry was enclosed in a convection oven under a nitrogen flow rate of 200 L / h. Before starting each experiment, the oven was preheated to a temperature of 115 °C, above the melting point of the pure polymer, and the sample was placed on the aluminum plate to ensure good contact. The upper geometry was then gradually lowered onto the sample for proper adhesion.

[0159] The temperature was then raised to 150 °C and kept constant for the remainder of the experiment. A constant interval was then applied to prevent excessive thinning of the samples before freezing. To monitor the gelation of the samples, Fourier transform mechanical spectroscopy (FTMS) was applied. Here, a sample is subjected to oscillatory stress at several frequencies simultaneously (multifrequency strain overlap), between 1 and 64 rad / s, i.e., 1, 2, 4, 8, 16, 32, 64 rad / s, and data are collected for G'(œ), G"(œ), and the damping factor tan(ô) every 30 s, where co is the angular frequency.

[0160] The final deformation is 4.18%. Crosslinking was monitored for 250 minutes, after which there was no further significant change in G' and G''. The freezing times and storage modulus G' and G'' thus obtained are reported in Table 2 below.

[0161] [Tables2] Sample Tgel (s) G'(œ) DN25 1650 0.44 DN50 1560 0.63 DN75 1620 0.77 DN100 750 1.12 DN200 450 1.49

[0162] For the DNs samples, tgei and G' increase as the amount of dicarboxylic acid increases. The value reached for G' clearly shows that the amount of crosslinking agent influences the crosslinking density of the samples. The modulus reaches a plateau for all samples except DN2oo, where the ratio between acid and epoxide functions is 2:1.

[0163] 1.5. Solubility in reactive solvent

[0164] Complete crosslinking of the thermolatent DNs mixture was carried out in an oven under an argon flow at 150°C, for a period of 24 hours.

[0165] To confirm the presence of dynamic bonds, approximately 0.5g of each composition was immersed in a reactive solvent consisting of 30mL of xylene, 15mL of butanol, and 0.1g of triazabicyclodecene (TBD) as a transesterification catalyst.

[0166] The mixture is then placed in a stainless steel acid digestion reactor (Parr Instrument Company, Illinois, USA) for a period of 24 hours at a temperature of 150°C and under magnetic stirring.

[0167] The temperature was maintained using a heating plate and a heating collar and the temperature was monitored using a thermocouple.

[0168] At the end of the experiment, only samples DN100 and DN200 were dissolved. Samples DN75, DN50, and DN25 were partially solubilized. The presence of non-exchangeable bonds is thus demonstrated for certain compositions.

[0169] 1.6. Characterization of DNs crosslinked samples

[0170] The DNs samples were characterized after a period of 24 hours in the oven at a temperature of 150°C under argon flow.

[0171] Dynamic mechanical analysis (DMA) was performed using a Q800 DMA (TA Instrument, USA) in tensile mode on a rectangular sample measuring 35 x 5 x 1.5 mm at a loading frequency of 1 Hz. The temperature range studied was from -115°C to 180°C with a heating rate of 3°C / min.

[0172] For the crosslinked samples, the modulus of elasticity E' (MPa measured at a temperature of 398 K), the crosslinking density vXjD (mol / cm3) and the elastic molecular weight MXjD (g / mol) were extracted at the level of the rubbery platform at 150°C.

[0173] During the swelling tests of most of the samples, 0.2g of samples were added to 40mL of xylene and 1.5g of antioxidant BHT in a flask under reflux at 125°C for a period of 24 hours.

[0174] The solvent was then removed in order to weigh the swollen samples. All samples were dried under vacuum for 12 hours at a temperature of 140°C before being weighed again. The gel percentage TGei (weight percentage), swelling ratio Q (weight percentage), crosslinking density vx>s (mol / cm3) and The elastic molecular weight Mx>s (g / mol) was thus determined. All the results are presented in Table 4. Dynamic Mechanical Analysis (DMA) Swelling Test Sample E' VX,D MXjD TGei(wt%) Q (wt%) vx,s MXjS DN25 1.41 1.4 x 10⁴ 6550 87.5 463 1.6 x 10⁴ 5670 DN50 2.52 2.5 x 10⁴ 3660 93.7 322 3.3 x 10⁴ 5780 DN75 2.88 2.9 x 10⁴ 3200 95.1 232 5.5 x 10⁴ 1680 DN100 3.79 3.8 x 10⁴ 2430 88.7 186 7.3 x 10⁴ 1270 DN200 4.01 4.0 x 10⁴ 2300 95.8 187 6.4.104 1450

[0175] The measured gel rates indicate that the xylene-soluble fraction is between 4.2 and 12.5% ​​by mass. This result is obtained thanks to the very low proportion of non-functionalized chains revealed in Example 1.2. These gel rates, substantially above 70%, indicate high resistance to hydrocarbons, desirable for use as a fuel tank material.

[0176] Stress relaxation studies were performed on the DNioo sample under controlled deformation in an Ares-G2 rheometer (TA Instruments, USA) using a torsional loading mode at different temperatures. For this purpose, the samples were pressed at 115°C in a rectangular mold (50 x 16 x 5 mm) and then cured in an oven at a temperature of 150°C for 24 hours.

[0177] In the rheometer, a 2% strain was applied in order to follow the relaxation modulus E' over 60,000s.

[0178] Tensile tests were carried out on dumbbell-shaped specimens measuring 25 x 4 x 1.5 mm, on an Instron 6800 dual-column machine. The displacements were recorded with a non-contact AVE 2 video extensometer.

[0179] The results are presented in Figures 2 and 3, which represent the stress relaxation moduli carried out at temperatures ranging from 170°C to 200°C for approximately 17 hours.

[0180] Figures 2 and 3 show that the samples relax the stresses after a duration of 1000 seconds and 50% of the initial stress is relaxed after 16 hours for all temperatures tested while maintaining a relaxation modulus of 1 MPa beyond this time.

[0181] 1.7. Continuous extrusion and injection and recycling of injection cores

[0182] The preparation of the pre-vitrimer DNioo on a larger scale (larger quantity) was carried out on a Rondol vertical extruder “Ail in One 10 mm C3432”, composed of 9 separate heating zones.

[0183] The temperature profile was established as follows: all heating zones at 115°C except for the last one, where a setpoint temperature of 125°C was applied. The screw profile is as follows, from top to bottom: 13 feed screw elements, 2 mixing screw blocks at 60°, 2 mixing screw blocks at 90°, 6 feed screw elements, 2 mixing screw blocks at 60°, 6 feed screw elements, 3 mixing screw blocks at 60°, 5 feed screw elements, 1 discharge screw element, one screw end (40 D). The screw rotation speed was set to 10 rpm, which corresponds to a final throughput of 120 g / h and a total residence time of 10 min.

[0184] The p(E-CO-GMA) granules were first cooled to low temperature with liquid nitrogen and ground into powder, then mixed with the Pripol / Pripolate mixture.

[0185] The mixture was fed into the extruder through the first feed zone of the extruder column. At the exit of the extruder column, the extruded filament was cut into pellets and directly transferred to a Rondol Medika 50kN injection molding machine.

[0186] The temperature was constant at 115 °C on the 4 heating zones of the machine, with an injection speed of 30 mm / s and an injection time of approximately 15 s. Following this method, several 2.1 g samples for tensile testing were obtained (dumbbell specimens + injection core).

[0187] The 0.6g (29 wt. %) injection cores are taken and reinserted into the machine for a second injection cycle.

[0188] 1.8. Preparation of a fuel tank for a plug-in hybrid vehicle

[0189] A first 39-litre tank was obtained from high-density polyethylene (HDPE) sold under the trade name Lupolen 4261 AG by the company LyondellBasell.

[0190] A second reservoir was prepared with a vitrimer according to the invention, having in particular a ductility of -40°C or less, and implemented with the same blow molding machine. The conditions were adjusted to maintain a constant weight of 8.2 kg between the two reservoirs.

[0191] Both tanks were filled with 7 litres of E10 type petrol.

[0192] The tanks were carefully sealed and placed in an ATEX enclosure at a temperature of 40°C for a period of one month.

[0193] The pressure was 35 kPa at the beginning of the test period and 20 kPa at the end of the tests.

[0194] After one month, the pressure was released and the residual deformation on the lower part of the tank was measured for both tanks. The following results were obtained:

[0195] 12.8 mm for the first HDPE tank and 5.3 mm for the tank with the vitrimer.

[0196] These results show that a fuel tank usable for plug-in hybrid vehicles, prepared with a composition according to the invention, can remain under pressure for longer periods than a tank prepared with high-density polyethylene (HDPE).

[0197] 1.9. Preparation of a tank obtained from two injected half-shells then welded

[0198] Two polypropylene half-shells (typically Hostalen PP HP1850 from LyondellBasell) were injected by a conventional method before being welded (mirror weld at over 250°C) to obtain a coolant reservoir for example.

[0199] Beyond a temperature of 80°C, this part exhibits several failure modes by fining, rupture of the weld zone (zone of least macromolecular entanglement) by the pressure generated by the coolant.

[0200] The same part made from a vitrimerized polyolefin, according to the invention, has improved thermal resistance measured up to 150°C without any sign of the failure modes previously mentioned.

[0201] This is attributed to the dynamic bonds which take place throughout the polymer network constituting the part as well as in the weld zone (which is now part of the general network of the part thanks to the covalent bonds).

Claims

Demands

1. Use of at least one composition for the manufacture of at least one fuel tank for a plug-in hybrid motor vehicle; said polymer network composition comprising at least one polymer network including several interatomic bonds whose distribution within the polymer network is capable of varying and at least one catalyst capable of promoting exchange reactions within the polymer network; said composition being ductile at a temperature below or equal to 0°C and exhibiting resistance to fining at a temperature above or equal to 0°C.

2. Use according to claim 1, characterized in that the interatomic bonds, the distribution of which within the polymer network is likely to vary, are selected from the group consisting of ethylenic double bonds -C=C-, ester bonds -COO-, amide bonds -CONH-, urethane vinylogum bonds -OOC-CH=C-NH-, imine bonds -C=N-, hydrazone bonds -C=N-NH-, oxime bonds -C=NO-, aldol bonds -C(OH)-C(CHO)-, allylic ester bonds -COO-CH2-C=C-, thioester bonds -COS-, acetal and hemiacetal bonds -OC(OR'), siloxane bonds -Si-O-Si, sulfonate bonds -SOC, disulfide bonds -SS-, and bonds sulfate.

3. Use according to claim 1 or 2, characterized in that the interatomic bonds, the distribution of which within the polymer network is likely to vary, are chosen from the group consisting of ethylenic double bonds -C=C- and ester bonds -COO-, preferably ester bonds -COO-.

4. Use according to any one of the preceding claims, characterized in that the polymer network has an enthalpy of fusion greater than or equal to 5 J / g measured by DSC.

5. Use according to any one of the preceding claims, characterized in that the polymer network is capable of being obtained from at least one semi-crystalline polymer, preferably selected from the group consisting of polyethylene, propylene, thermoplastic polyamides, thermoplastic polyimides, polyethylene terephthalate, polybutylene terephthalate, polyethylene oxide, ethylene copolymers such as ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc) copolymers, ethyl acrylate, ethylene butyl acrylate, poly(ethylene-co-glycidyl methacrylate), preferably ethylene and methacrylic acid glycidol ester copolymers such as poly(ethylene-co-glycidyl methacrylate).

6. Use according to any one of the preceding claims, characterized in that the catalyst or catalysts is or are selected from the group consisting of organic, inorganic, metallo-organic catalysts and mixtures thereof, preferably organic, such as nitrogenous bases and guanidines, metallic, such as organic acid salts of alkaline earth metals, organic acid salts of alkali metals, organic acid salts of transition metals, and mixtures thereof.

7. Use according to any one of the preceding claims, characterized in that the catalyst(s) is or are capable of promoting transesterification reactions.

8. Use according to any one of the preceding claims, characterized in that it comprises at least a fraction insoluble in a non-reactive solvent of at least 70% by weight, preferably a fraction insoluble in a non-reactive solvent of at least 85% by weight, relative to the total weight of said composition.

9. Use according to any one of the preceding claims, characterized in that it is ductile at a temperature less than or equal to -40°C and exhibits resistance to fining at a temperature greater than or equal to 35°C.

10. Fuel tank for a plug-in hybrid vehicle, obtained from at least one composition as defined according to any one of claims 1 to 9.