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 a tank

[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, in particular 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 motor vehicles (PH-EV or "Plug-In Electric Vehicle" in English) are generally subjected cyclically to high internal pressures, for example up to 400 mbar, in particular in certain fully electric driving modes, as well as to significant increases and / or fluctuations in temperature.

[0004] Thus, fuel tanks intended for rechargeable hybrid motor vehicles are subject to demanding specifications in terms of resistance to damage, in particular due to pressure and heat, and must for this reason in particular have improved mechanical properties compared to the fuel tanks of conventional thermal engines.

[0005] Indeed, traditional tanks, such as multi-layer tanks obtained by blowing polyethylene (PE), usually have difficulty withstanding the pressure and heat conditions generally observed in rechargeable hybrid motor vehicles without being deformed significantly, 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 crosslinked high-density polyethylene (HDPE), or from thermosetting polymers, such as epoxy resins (or polyepoxides) or polyurethanes, have already been proposed.

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

[0008] Tanks obtained from crosslinked high-density polyethylenes have, as for them, mechanical properties may prove unsatisfactory, in particular such tanks are still too sensitive to fining and suffer a significant loss of their cold impact resistance properties. Indeed, the permanent covalent bonds present within crosslinked high-density polyethylenes make them too fragile for the intended application. Furthermore, tanks obtained from such crosslinked polyolefins are not recyclable, which leads to a high cost when they are replaced or in the event of aging.

[0009] Finally, to obtain a crosslinked polyolefin tank, the part first produced from non-crosslinked polyolefin must be subjected to a treatment, usually under radiation or using peroxides, to accomplish the crosslinking. Such a process is expensive and also does not allow uniform crosslinking of all the polymer chains but leaves a large fraction of non-crosslinked polymer.

[0010] In addition to this, tanks obtained from thermosetting polymers, such as epoxies (or polyepoxides) or polyurethanes, have the disadvantages of being poorly resistant to shocks, of being difficult to reshape in the event of cracks and of not being able to be recycled, particularly at the end of the vehicle's life.

[0011] Indeed, given the fact that the chemical reactions that led to the formation of polyepoxides or polyurethanes are irreversible, the reservoirs obtained from such thermosetting polymers cannot be remelted, which means that they cannot be repaired in the event of cracks or be remodeled for a second life. In particular, the risks of cracks are linked to the high crosslinking density within thermosetting polymers, and their propagation is favored by their low ductility, particularly in the case of polyepoxides.

[0012] Furthermore, thermosetting polymers are difficult to use to obtain fuel tanks due to their low deformability.

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

[0014] In view of the above, 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 linked to their recycling, their remodeling and their implementation.

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

[0016] In particular, the invention aims to propose 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 reshapable for subsequent 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 having a resistance to brittleness at a temperature greater than or equal to 0°C.

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

[0019] The composition according to the invention thus makes it possible to overcome the previously mentioned drawbacks, in particular by leading to fuel tanks, preferably used in rechargeable hybrid vehicles, having improved mechanical properties, in particular having improved resistance to finning including under high pressure and temperature conditions.

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

[0021] Furthermore, 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 zones of the fuel tanks.

[0022] In other words, the composition according to the invention makes it possible to make the welding zones of the 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 linked to chemical attack, of fuel tanks.

[0024] Preferably, the composition according to the invention makes it possible to protect the reservoir 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 which are recyclable or remodelable for later use, including at the end of the life of the plug-in hybrid vehicle. In particular, in the event of a crack, the tanks obtained from the composition according to the invention are more easily repairable than tanks obtained from thermosetting polymers.

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

[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, 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 subject 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 indicated previously, the composition advantageously makes it possible to improve the mechanical properties, preferably the resistance to brittleness, more preferably the resistance to pressure, of at least one tank, in particular a fuel tank, preferably a fuel tank for a rechargeable 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 attacks.

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

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

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

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

[0038] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the description and the examples which follow.

[0039] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, in particular in the expressions “between” and “ranging from.... to...”.

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

[0041] As indicated previously, the composition according to the invention can be likened to a dynamic network in which the interatomic bonds are interatomic bonds whose distribution within the polymer network can vary under the effect of internal exchange reactions, without the number of covalent bonds changing on average. The interatomic bonds capable of varying are said to be exchangeable and are distinguished from the so-called reversible bonds by the fact that the latter break and are remade when the temperature is raised or lowered, whereas on 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 crosslinking rate of the polymer network.

[0044] In other words, the dynamic network is comparable to a chemically crosslinked 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 non-crosslinked polymer is soluble in this solvent at room temperature, for example ranging from 20 to 37°C, or at a higher temperature. By non-reactive, we mean that this solvent is not likely to break any bond in the network.

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

[0046] For the purposes of the present invention, interatomic bonds are dynamic and exchangeable bonds forming interatomic bonds 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, similar to a non-reactive solvent, is not such as to affect the interatomic bonds.

[0049] Thus, the presence of fuel, similar to a non-reactive solvent, brought into 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 linked 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 the imperfections of the network formed during its synthesis. Typically, the exchangeable bond networks obtained by radical grafting have insoluble fractions of between 30% and 66%.

[0052] The interatomic bonds may be selected from the group consisting of ethylenic double bonds -C=C-, ester bonds -COO-, amide bonds -CONH-, -, urethane vinylogous bonds -OOC-CH=C-NH-, imine bonds -C=N-, hydrazone bonds -C=N-NH-, oxime bonds -C=NO-, aldol bonds -C(OH)-C(CHO)-, allyl 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 bonds -COO-.

[0056] The interatomic bonds may undergo exchangeable reactions such as those selected from the group consisting of transesterification reactions, transcarbonation, exchange by transcarbamoylation of urethanes, transamination of imines, transamination of vinyl urethane, silyl ether type exchange, transesterification assisted by (oxime-promoted transesterification), olefin metathesis, boronic ester-based bond exchange, disulphide-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, including transesterification reactions.

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

[0060] The composition according to the invention comprises a polymer network capable of being obtained from at least one semi-crystalline polymer.

[0061] Preferably, the semi-crystalline polymer has a glass transition temperature of less than -40°C and even more preferably less than -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 and 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 carrying 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 comonomer carrying 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 devoid of 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 copolymers of ethylene and methacrylic acid ester and glycidol.

[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 capable of being 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 polymer fragments preferably obtained from one or more semi-crystalline polymers as defined previously.

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

[0072] Preferably, the catalyst(s) is(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 nitrogenous bases and guanidines, metal 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 metal catalysts, in particular organometallic complexes, inorganic metal salts, organic metal 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 (tetramethyl guanidine), TBD (triazabicyclodecene), MTBD (methyltriazabicyclodecene) and mixtures thereof.

[0077] Preferably, the catalyst(s) is(are) selected 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(s) is(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(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(s) is(are) chosen from the group consisting of organic acid salts of potassium, cesium, zinc, in particular carboxylic acid salts of zinc and / or TBD.

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

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

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

[0084] Preferably, the polymer is chosen from the group consisting of copolymers of ethylene and methacrylic acid ester and glycidol, 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% in moles (corresponding to 0.25 to 2 molar equivalents) relative to the reactive functions, preferably the epoxy functions, present in the polymer network.

[0085] As indicated previously, the composition according to the invention is ductile at a temperature less than or equal to 0°C and has a high resistance to brittleness 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 still less than or equal to -20°C, even better still less than or equal to equal to -30°C.

[0087] The composition according to the invention has a 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 creep resistance, it is meant in the sense of the present invention that when the composition is shaped to obtain a mechanical part, in particular an automobile 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] The deformation can in particular be measured using deformation sensors.

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

[0091] The composition according to the invention has in particular a high creep resistance measured at a temperature ranging from 0°C to 180°C, more preferably ranging from 0°C to 100°C, even better ranging 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 creep resistance beyond this at temperatures of +35°C (in other words, at temperatures greater than or equal to 35°C).

[0093] Ductility is measured by a rate of elongation 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 deformation of 2% in shear. However, at a temperature above 170°C, the composition is capable of relaxing the stresses after a duration greater than 1000 seconds and particularly 50% of the initial stress is relaxed after a duration of 16 hours whatever the temperature tested between 170°C and 200°C while retaining its modulus of elasticity.

[0095] According to a preferred general characteristic, the composition according to the invention comprises at least one insoluble fraction of at least 70% by weight in a solvent which 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 one insoluble fraction of at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight, relative to the total weight of the composition.

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

[0098] The good non-reactive solvent can be for example xylene at 125°C.

[0099] The solvent swelling test is a conventional test known to a person skilled in the art.

[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-bottomed flask under reflux at a temperature of 125°C for a period of 24 hours. The solvent is then removed and the swollen sample was weighed using a precision balance. The sample is then dried under vacuum at a temperature of 140°C for a period of 12 hours and then weighed again.

[0101] In addition to this desirable property of insolubility in a non-reactive solvent such as xylene, representative of the 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 may be, for example, a xylene / butanol mixture at 150°C.

[0103] The reactive solvent mixture redissolution test can be carried out by mixing 0.2 g of 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 carried out using a digestion bomb, at 150°C under magnetic stirring and for a period 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 previously. Use of the composition

[0105] As indicated previously, the invention also relates to the use of at least one composition, as defined previously, for the manufacture of at least 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 plug-in hybrid motor vehicle.

[0108] More preferably, the invention relates to the use of the composition, as defined above, for improving 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 attacks. Method of preparing the composition

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

[0111] The polymer(s) and the catalyst(s) used 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 copolymers of ethylene and methacrylic acid ester and glycidol.

[0113] Preferably, the catalyst(s) is(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(s) is(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 corresponding 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) may be mixed sequentially or at the same time (i.e. in one go) during step i).

[0120] Preferably, the polymer(s), crosslinking agent(s), 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 higher than the melting temperature Tf of said polymer and lower than the hardening temperature T2 of said mixture.

[0122] At the end of the shaping step ii), a polymer 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 crosslinking.

[0124] The polymer 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 is 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] At the end of step iii), the process according to the invention may comprise 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 network composition of polymer comprising at least one polymer network including several exchangeable covalent bonds chosen from the group consisting of ester bonds -COO- 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 copolymers of ethylene and methacrylic acid ester and glycidol.

[0134] Preferably, the reservoir is obtained with a composition, as defined previously, 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 has a fining resistance greater than or equal to 35°C.

[0136] Preferably, the resistance to deformation of the tank is high at a temperature of 35°C, in particular has 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 fining of a fuel tank obtained with a composition according to the invention can for example be measured according to the following protocol: a. mounting a tank, for example filled with 7L of fuel, on a frame in vehicle position with its components (for example with pipe, canister, etc.) and installation of several sensors intended to measure the deformation under the pump gauge module (i.e. under the tank), b. after zeroing the sensors, placing the tank in an oven at a temperature of 45°C and continuously recording the displacement of the sensors due to the deformation of the tank, measuring the temperature and internal pressure of the tank until the displacement of the sensors stabilizes at + / -0.1 mm, c. removal of the tank from the oven 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 fuel, record the deformation and check whether the deformation of the tank 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, 10g of a fatty acid dimer, sold under the trade name Pripol® 1009, were mixed with 0.77g of hydrated zinc acetate Zn(OAc)2 2H2O (corresponding to a [Zn] / [COOH] molar ratio of 0.10). The mixture was slowly heated from 100°C to 180°C, then left at a temperature of 180°C for 4 hours under 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 remove any residual acetic acid.

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

[0145] The sample will be called A

[0146] 1.2. Size exclusion chromatography (SEC) analysis is carried out 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% 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. The molar masses are determined using the so-called "universal calibration" method, considering as Mark-Houwink parameters: KPS = 14.1 x 105 dg x L 1 and aPS = 0.7 for PS and Kpe = 95.4 x 105 dg x L 1 and aPE = 0.640 for PE. The mass distribution curve is presented below. Analysis by the binomial law assuming a perfectly statistical copolymerization reveals that the mass fraction of chains devoid of methacrylic comonomer (GMA) is of the order of 3%. The results are shown in [Fig.l].

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

[0149] 1.3. Preparation of a vitrimer Samples containing dicarboxylic acid or 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) containing 8% by weight of glycidyl methacrylate (i.e. 1.71% mol) were introduced with a hopper 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 nomenclature DNx is used, where x represents the percentage of carboxylic functionality relative to epoxy.

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

[0153] The compositions are indicated in the following table 1:

[0154] [Tables 1] Sample mass of P(E-co-GMA dicarboxylic acid (DA) mass m 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 gelation

[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 tons for 3 minutes.

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

[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 temperature of the pure polymer, and the sample was placed on the aluminum plate to ensure good contact. The upper geometry was progress- sively 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 avoid excessive thinning of the samples before gelation. To monitor the gelation of the samples, the Fourier Transform Mechanical Spectroscopy (FTMS) method was applied. Here, a sample is subjected to oscillatory stress at several frequencies simultaneously (multi-frequency strain overlap), between 1 -64 rad / s, i.e. 1, 2, 4, 8, 16, 32, 64 rad / s and collects data of 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%. The crosslinking is monitored over a period of 250 minutes, after which there was no longer any significant change in G' and G”. The gel times and storage modulus G' and G' ' thus obtained are reported in the following Table 2.

[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 DNs samples, tgei and G' increase as the amount of dicarboxylic acid increases. The achieved value of G' clearly shows that the amount of crosslinker has an influence on the crosslinking density of the samples. The modulus reaches a plateau for all samples except for DN200, 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 a flow of argon 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 with magnetic stirring.

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

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

[0169] 1.6. Characterization of crosslinked DNs samples

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

[0171] Dynamic mechanical analyses (DMA) were carried out using a DMA Q800 (TA Instrument, USA) in tensile mode on a rectangular sample with dimensions of 35 x 5 x 1.5mm at a loading frequency of 1Hz. 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 elastic modulus E' (MPa measured at a temperature of 398 K), the crosslinking density vx>D (mol / cm3) and the elastic molecular weight MXjD (g / mol) were extracted at the rubber plateau at 150°C.

[0173] In swelling tests of most samples, 0.2g of samples were added to 40mL of xylene and 1.5g of BHT antioxidant 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 content TGei (weight percentage), swelling ratio Q (weight percentage), crosslinking density vXjS (mol / cm3) and the elastic molecular weight Mx>s (g / mol) could thus be determined. All the results are presented in Table 4. Dynamic Mechanical Analysis (DMA) Swelling Test Sample E' VX,D MxD Tcel (wt%) Q (wt%) vx,s MXjS DN25 1.41 1.4.104 6550 87.5 463 1.6.104 5670 DN50 2.52 2.5.104 3660 93.7 322 3.3.104 5780 DN75 2.88 2.9.104 3200 95.1 232 5.5.104 1680 DN100 3.79 3.8.104 2430 88.7 186 7.3.104 1270 DN200 4.01 4.0.104 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 rate of non-functionalized chains revealed in Example 1.2. These gel rates significantly higher than 70% indicate a high resistance to hydrocarbons, desirable in use as fuel tank material.

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

[0177] In the rheometer, a strain of 2% 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 a double-column Instron 6800 machine. Displacements were recorded with a non-contact AVE 2 video extensometer.

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

[0180] [Fig.2] and [Fig.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] Preparation of pre-vitrimer DNioo on a larger scale (larger quantity) was produced on a Rondol “Ail in One 10 mm C3432” vertical extruder, consisting 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 set temperature of 125°C is applied. The screw profile is as follows, from top to bottom: 13x feed screw elements, 2x mixing screw blocks at 60°, 2x mixing screw blocks at 90°, 6x feed screw elements, 2x mixing screw blocks at 60°, 6x feed screw elements, 3x mixing screw blocks at 60°, 5x 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 flow rate of 120g / h and a total residence 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 outlet of the extruder column, the extruded filament was cut into pellets and directly transferred into a Rondol Medika 50kN injection molding machine.

[0186] The temperature was constant at 115°C across 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 tests were obtained (dumbbell specimens + injection core).

[0187] The 0.6g (29 wt. %) injection cores are taken and inserted back 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 tank was prepared with a vitrimer according to the invention, having in particular a ductility less than or equal to -40°C, and implemented with the same blowing machine. The conditions were adjusted to maintain a constant weight of 8.2 kg between the two tanks.

[0191] Both tanks were filled with 7 liters of E10 type gasoline.

[0192] The tanks were carefully capped 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 PE-HD 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 using a conventional method before being welded (mirror welding at over 250°C) to obtain a coolant reservoir, for example.

[0199] Above a temperature of 80°C, this part presents several failure modes by fining, rupture of the weld zone (zone of weakest 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 signs of the modes of previously mentioned failures.

[0201] This is attributed to the dynamic bonds that 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

Claims

1. A polymer network composition comprising at least one polymer network including a plurality of 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 a resistance to brittleness at a temperature greater than or equal to 0°C.

2. Polymer network composition according to claim 1, characterized in that the interatomic bonds, the distribution of which within the polymer network is capable of varying, are chosen from the group consisting of ethylenic double bonds -C=C-, ester bonds -COO-, amide bonds -CONH-, urethane vinylogous bonds -OOC-CH=C-NH-, imine bonds -C=N-, hydrazone bonds -C=N-NH-, oxime bonds -C=NO-, aldol bonds -C(OH)-C(CHO)-, allyl ester bonds -C00-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.

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

4. Polymer network composition 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. A polymer network composition according to any one of the preceding claims, characterized in that the polymer network is obtainable 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 copolymers (EVAc), ethyl acrylate, ethylene vinyl acetate ... butyl, poly(ethylene-co-glycidyl methacrylate), preferably copolymers of ethylene and methacrylic acid ester and glycidol such as poly(ethylene-co-glycidyl methacrylate).

6. Polymer network composition according to any one of the preceding claims, characterized in that the catalyst(s) is(are) chosen 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. A polymer network composition according to any one of the preceding claims, characterized in that the catalyst(s) is or are capable of promoting transesterification reactions.

8. A polymer network composition according to any one of the preceding claims, characterized in that it comprises at least one 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. A polymer network composition 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 has a resistance to brittleness at a temperature greater than or equal to 35°C.

10. Use of at least one composition as defined according to any one of the preceding claims for the manufacture of at least one tank, preferably a fuel tank, in particular a fuel tank for a plug-in hybrid motor vehicle.

11. Tank, preferably fuel tank, in particular 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.

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