Composition for manufacturing a three-dimensional object by extrusion blow molding

Abstract

The present invention relates to a composition for manufacturing a three-dimensional object for transporting, distributing or storing gas, by extrusion blow molding, comprising from 70 to 99.49% by weight of at least one polyamide having a number of carbon atoms per nitrogen atom greater than or equal to 6.5; from 0.50% to 25% of at least one functional polyolefin having a glass transition temperature Tg of less than -25°C; from 0.01 to 5% by weight of at least one additive, the composition having a melt viscosity greater than 40 000 Pa.s. The present invention also relates to a method for preparing the composition and to the use of the composition for manufacturing a three-dimensional object. The present invention also relates to a method for preparing the three-dimensional object. The present invention also relates to the three-dimensional object manufactured by extrusion blow molding, as well as to the three-dimensional object comprising a sealing layer.

Description

[0001] Composition for manufacturing a three-dimensional object by extrusion blow molding

[0002] technical field

[0003] The present invention relates to compositions for the manufacture of a tank by extrusion blow molding as well as their use for the preparation of tanks intended for the transport, distribution or storage of gas and the process of preparing said tanks.

[0004] Technical background

[0005] One of the goals in the automotive sector is to offer increasingly less polluting vehicles. Thus, electric or hybrid vehicles with batteries aim to gradually replace internal combustion engine vehicles, such as gasoline or diesel vehicles.

[0006] However, the battery is a relatively complex component of the vehicle. Depending on its location within the vehicle, it may need protection from impacts and the external environment, which can include extreme temperatures and varying humidity. It is also essential to prevent any risk of flames. Furthermore, it is important that its operating temperature does not exceed 55°C to avoid damaging the battery cells and to preserve its lifespan. Conversely, for example in winter, it may be necessary to raise the battery's temperature to optimize its performance.

[0007] Furthermore, the electric vehicle still suffers today from several problems, namely battery range, the use in these batteries of rare earth elements whose resources are not inexhaustible, as well as a problem of electricity production in different countries to be able to recharge the batteries.

[0008] Hydrogen therefore represents an alternative to the electric battery, since it can be transformed into electricity by means of a fuel cell and thus power electric vehicles.

[0009] However, storing hydrogen is technically difficult and expensive due to its very low molar mass and extremely low melting point, especially for mobile storage. Furthermore, hydrogen must be kept under high pressure for efficient storage. This is particularly true for hybrid fuel cell road vehicles, which aim for a range of around 600 to 700 km, or even less for primarily urban use in conjunction with a battery-powered electric system.

[0010] Type IV tanks are designed for storing hydrogen (H2) under high pressure. They consist of a composite shell and an inner liner made of polymer material. This liner must withstand the tank's internal pressure (e.g., 700 bar) while also being resistant to impacts and heat sources. The filling and emptying cycles of H2 place thermomechanical stresses on the polymer liner. Compressing a gas within a finite volume causes it to heat up, while expanding it results in cooling. The operating temperature range for a Type IV tank must be between -40°C, or even -60°C and 80°C. Due to the cylindrical geometry of a Type IV tank, geometric discontinuities in the polymer liner are inevitable, leading to areas of concentrated deformation and stress.The composition of the second liner must therefore include ductile materials to withstand thermo-mechanical changes. For storage volumes exceeding a certain size (generally 50 L or more) and for large production runs, the inner liners of hydrogen tanks are commonly manufactured using blow molding. This technique involves vertically extruding a tubular parison. This extruded parison is secured at one end in a mold, air is then blown through, and the other end is also sealed to trap the blown air within the hollow parison. The resulting pressure forces the molten polymer against the mold surface, thus forming the liner.

[0011] The polymer composition plays a crucial role in this manufacturing process. The parison's thickness must be sufficient to prevent thinning of the part near the die and to avoid melt tearing. The polymer must also exhibit good tensile strength and sufficient swelling during the blow molding stage.

[0012] Furthermore, the finished part must be suitable for hyperbaric storage. In other words, it must be able to withstand mechanical fatigue, meaning it must delay the initiation and propagation of fatigue cracks. Finally, it is preferable that part of the composition be recyclable.

[0013] Application EP 0495363 relates to polyamide compositions based on a polyamide (PA) alloy and special olefin-acid anhydride copolymers and their use for the production of shaped hollow bodies.

[0014] International application W020027031 relates to a composition based on polyamide 6 (PA6), shock modifier and metal halide.

[0015] Application FR2996556 relates to a liner for the storage of gas, in particular compressed natural gas (CNG), methane or hydrogen comprising a composition based on branched polyamide and shock modifier.

[0016] Application CA3101967 relates to polyamide compositions for blow molding based on PA 6 and shock modifier and consequently.

[0017] Application EP3725848 proposes a resin composition comprising a polyamide and an impact-resistant material.

[0018] Application EP2782964 relates to a molding composition comprising a polyamide, a shock modifier, a copolymer comprising styrene and a dicarboxylic anhydride derivative and additives.

[0019] Application EP1170334 describes a molding composition based on polyamide and at least two polyolefin copolymers for improved impact resistance.

[0020] Application EP0977810 proposes a thermoplastic composition comprising a polyamide-based matrix and at least one impact resistance modifying agent for use in blow molding processes for manufacturing parts or articles.

[0021] Application WO9413740 relates to a blow molding and extrusion composition comprising a polyamide and a grafted polymer or a mixture of grafted or non-grafted polymer.

[0022] Application JP2001302908 relates to a composition for a blow-molding article based on polyamide and modified polyolefin. Application EP1352934 describes metal surfaces coated with a polyamide-based layer consisting of a mixture of polyamide and a polyolefin functionalized with an unsaturated carboxylic acid anhydride.

[0023] Application EP2649130 describes a liner for gas storage comprising a composition including a mixture of polyamide and a polyolefin functionalized by an anhydride.

[0024] It turns out that the compositions described in the prior art do not allow us to meet this compromise of properties, which relate both to the processability of the composition and to the mechanical properties of the final part, i.e. the liner, especially when the final part is intended for large tanks.

[0025] Technical problem to solve

[0026] Indeed, it is necessary to provide increasingly high-performance compositions with suitable physicochemical and thermomechanical properties. First, with regard to environmental concerns, it is important to offer easily recyclable compositions. Second, during the manufacturing process of parts in the extrusion blow molding stage, high parison strength, good tensile strength, sufficient swelling, and increased fatigue resistance are required.

[0027] The inventors discovered that the use of the composition according to the invention makes it possible to solve both the problems related to the processability of the material in the molten state and also the requirements of the finished product, in particular the mechanical strength of the part.

[0028] Brief description of the invention

[0029] The present invention relates to a composition for manufacturing a three-dimensional object, preferably a tank for the transport, distribution or storage of gas, by extrusion blow molding, comprising:

[0030] - from 70 to 99.49%, in particular from 89 to 98%, especially from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0031] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin, having a glass transition temperature Tg below -25°C measured according to ISO 6721-4:2019;

[0032] - from 0.01 to 5% of at least one additive, in particular from 0.1 to 2% by weight relative to the total weight of the composition; the composition having a viscosity in the molten state greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0033] The present invention also relates to a method for preparing the composition according to the invention, comprising a compounding step under primary vacuum at a pressure of 80,000 Pa to 0.1 Pa, preferably under secondary vacuum at a pressure of 10,000 Pa to 1 Pa, of said composition at a molten polymer temperature above 280 °C, preferably above 300 °C, preferably between 300 and 350 °C, with an average residence time of 20 seconds to 10 minutes, preferably between 45 seconds and 6 minutes. The present invention also relates to the use of the composition according to the invention to manufacture a three-dimensional object, preferably a tank, by extrusion blow molding.

[0034] The present invention also relates to a method for manufacturing a three-dimensional object, preferably a tank, comprising an extrusion-blowing step of a composition according to the invention.

[0035] The present invention also relates to a three-dimensional object, preferably a tank, manufactured from the composition according to the invention by extrusion blow molding.

[0036] The invention finally relates to the use of the three-dimensional object according to the invention, for the transport, distribution or storage of gas, preferably hydrogen, nitrogen, carbon dioxide, natural gas, methane, even more preferably hydrogen.

[0037] Other advantageous characteristics of the composition according to the invention are specified below.

[0038] -The composition includes a polyamide with an average molar mass greater than 15,000 g / mol 1 , preferably greater than 20,000 g / mol 1 , preferably in a manner exceeding 30,000 g.mol 1 .

[0039] -The composition includes a polyamide selected from PA610, PA612, PA 614, PA 10, PAU and PA12, preferably from PA610, PA612, PAU and PA12, and mixtures thereof.

[0040] -The functional polyolefin of the composition has a glass transition temperature Tg of less than -30°C, preferably less than -35°C as measured according to ISO 6721-4:2019.

[0041] -The functional polyolefin has epoxy, anhydride and / or isocyanate functions, preferably maleic anhydride functions.

[0042] -Functional polyolefin has grafted functions.

[0043] -The additive is chosen from an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a flame retardant, a nucleating agent, a chain extender and a colorant, preferably the additive is an antioxidant.

[0044] Other advantageous characteristics of the three-dimensional object according to the invention are specified below.

[0045] -The three-dimensional object, intended for the transport, distribution or storage of gas, preferably dihydrogen, characterized in that it comprises a sealing layer comprising a composition according to the invention.

[0046] -The object is a hydrogen storage tank.

[0047] -The object comprises at least one layer of composite reinforcement, said innermost layer of composite reinforcement being welded or not, to said sealing layer according to the invention, preferably the outermost adjacent sealing layer.

[0048] -The object has a volume greater than 20 L, preferably a volume greater than 100 L, and even more preferably greater than 300 L.

[0049] Brief description of the figure: Figure 1 is a graph of a mechanical analysis of DMA according to ISO 6721-4:2019 performed on dry samples according to the invention and comparative. The graph expresses tan 6 as a function of temperature expressed in °C.

[0050] Detailed description

[0051] Other features, aspects, objects and advantages of the present invention will become even clearer upon reading the description that follows.

[0052] Unless otherwise stated, all percentages are mass percentages.

[0053] In this text, the quantities indicated for a given species may apply to that species according to all its definitions (as mentioned in this text), including more restricted definitions.

[0054] It is specified that the expressions "from ... to ..." and "between ... and ..." used in this description should be understood as including each of the mentioned limits.

[0055] Polyamide

[0056] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (Tables 1 and 2), and is well known to those skilled in the art. Thus, PAU signifies that it is obtained by polycondensation of amino-11-undecanoic acid. PA12 is obtained by polycondensation of lauryllactam. PA1010 is obtained by polycondensation of decanediamine (10) and decanedioic acid (10). PA1012 is obtained by polycondensation of decanediamine (10) and dodecanedioic acid (12).

[0057] The word "polyamide" covers both homopolyamides and copolyamides.

[0058] The invention is now described in more detail and in a non-limiting manner in the following description.

[0059] Polyamides are obtained by a polycondensation reaction of monomers, which can be amino acids or lactams, denoted Z, or chains of diacids and diamines, denoted XY, where X represents a diamine and Y a diacid. Thus, an amide group is formed by the reaction of an amine group with an acid group.

[0060] For the purposes of this invention, a unit is understood to be a Z or XY link resulting from the polycondensation of monomers.

[0061] For the purposes of this invention, the term "motif" means the sequence Z, the sequence X, or the sequence Y. In other words, unit Z consists of a motif Z, and unit XY consists of a motif X and a motif Y.

[0062] For the purposes of this invention, the C / N ratio means the average number of carbon atoms per nitrogen atom per unit.

[0063] In the case of a PA Z homopolyamide, where Z designates a repeating unit obtained from an amino acid or a lactam, the number of carbon atoms per nitrogen atom is the number of carbon atoms in the repeating unit. For example, PA 11 obtained by polycondensation of amino-11-undecanoic acid has a C / N ratio of 11.

[0064] In the case of a PA XY homopolyamide, where X represents a unit obtained from a diamine and Y represents a unit obtained from a diacid, the number of carbon atoms per nitrogen atom is the average number of carbon atoms present in the XY unit. For example, PA 612, obtained by polycondensation of hexanediamine, a C6 diamine, and dodecanedioic acid, a C12 diacid, is characterized by a C / N ratio of 9, calculated as (6+12) / 2 = 9.

[0065] For copolyamides, for example with the structure XaYa / XbYb, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is performed in molar proportion of the different amide units, that is, the XaYa and XbYb units. Thus, coPA 6T / 66, containing 60% 6T and 40% 66, is characterized by a C / N ratio of 6.6, obtained from the following calculation: 0.60x[(6+8) / 2]+0.40x[(6+6) / 2] = 6.6.

[0066] The composition according to the invention comprises at least one polyamide.

[0067] The polyamide content is 70 to 99.49%, preferably 89 to 98%, even more preferably 91 to 96% by weight relative to the total weight of the composition.

[0068] Polyamide has a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than or equal to 8.5.

[0069] The number-average molar mass of polyamide can be greater than 15,000 g / mol 1 , preferably greater than 20,000 g / mol 1 , preferably in a manner exceeding 30,000 g.mol 1 .

[0070] Polyamide can be a homopolyamide or a copolyamide or a mixture of these.

[0071] Preferably, the polyamide is a semi-crystalline aliphatic polyamide.

[0072] The term "semi-crystalline", in the sense of the invention, designates a polyamide which has a melting temperature (Tf) in DSC according to ISO 11357-3:2013, and an enthalpy of crystallization during the cooling step at a rate of 20K / min in DSC measured according to ISO 11357-3:2013 greater than 20 J / g, preferably greater than 30 J / g.

[0073] The said semi-crystalline aliphatic polyamide is derived from a repeating motif obtained by polycondensation of: at least one amino acid in the C9 to C18 range, preferably in the C18 to C12 range, or at least one lactam in the C9 to C18 range, preferably in the C18 to C12 range, or at least one diamine Ca in the C4-C36 range, preferably C6-C18, preferably C6-C12, more preferably C10-C12 range, with at least one dicarboxylic acid Cb in the C4-C36 range, preferably C6-C18, preferably C6-C12, more preferably C10-C12 range, or a mixture thereof, provided that the number of carbon atoms per nitrogen atom of the repeating motif is greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably above 8.5.

[0074] Examples of C9 to C18 amino acids include 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid and their derivatives, including N-heptyl-11-aminoundecanoic acid.

[0075] A lactam in the C9 to C18 range is notably lauryllactam.

[0076] Said at least one diamine Ca in C4-C36 may in particular be chosen from 1,4-butanediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids.

[0077] Advantageously, said at least one diamine Ca is in C6-C18 and selected from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine.

[0078] Said at least one Cb dicarboxylic acid in C4 to C36 may be selected from succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids.

[0079] Advantageously, said at least one dicarboxylic acid Cb is in C6 to C18 and is selected from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0080] Preferably, the polyamide is chosen from PA610, PA612, PA 614, PA 10, PAU and PA12, preferably from PA610, PA612, PAU and PA12, and mixtures thereof.

[0081] In one embodiment, the polyamide is a blend of two polyamides having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, in a weight proportion range of 5 / 95 to 95 / 5.

[0082] In another embodiment, which is preferred, the polyamide is a single polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5. By "single polyamide" is meant one or more polyamides having the same repeating unit, that is to say an identical repeating unit, within their polymer chain.

[0083] It has been observed that the crystallinity of the polyamide matrix is ​​better when it is made of a single polyamide, the higher crystallinity leading to lower permeability of the composition, once implemented as a liner for gas storage or transport applications, such as hydrogen.

[0084] The polyamide according to the invention has an inherent viscosity in m-cresol greater than 1.45, advantageously greater than 1.55, very advantageously greater than 1.6 as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass.

[0085] Functional polyolefin

[0086] The functional polyolefin content is 0.50% to 25%, preferably 2% to 20%, and even more preferably 4% to 15% by weight relative to the total weight of the composition. The term "functional polyolefin" refers to a functionalized polyolefin.

[0087] A functional polyolefin can be blended with a non-functionalized polyolefin.

[0088] The functionalized polyolefin can be selected from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the grafting ratio is, for example, 0.01 to 5% by weight:

[0089] - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing, for example, 35 to 80% by weight of ethylene;

[0090] - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM);

[0091] - the block copolymers styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS);

[0092] - ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate;

[0093] - ethylene and alkyl (meth)acrylate copolymers, containing up to 40% by weight of alkyl (meth)acrylate;

[0094] - ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0095] The functionalized polyolefin can also be selected from ethylene / propylene copolymers predominantly in propylene grafted with maleic anhydride and then condensed with mono-amino polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0096] The functionalized polyolefin may also be a co- or ter polymer of at least the following motifs: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0097] As an example of functionalized polyolefins of this latter type, we can cite the following copolymers, where ethylene preferably represents at least 60% by weight and where the ter monomer (the functional group) represents, for example, from 0.1 to 13% by weight of the copolymer:

[0098] - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers;

[0099] - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers;

[0100] - ethylene / vinyl acetate copolymers or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate.

[0101] In the preceding copolymers, (meth)acrylic acid can be salified with Zn or Li.

[0102] The term "alkyl (meth)acrylate" refers to methacrylates and alkyl acrylates in Cl to C8, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0103] Furthermore, the aforementioned polyolefins can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, etc. capable of reacting with them or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0104] Preferably, the composition according to the invention does not include cross-linked polyolefin, particularly for the recycling aspects of the composition.

[0105] The copolymers mentioned above can be copolymerized statistically or sequentially and exhibit a linear or branched structure.

[0106] Preferably, the functional polyolefin has grafted functions.

[0107] Functionalized polyolefins can be selected from any polymer containing alpha olefin motifs and motifs bearing polar reactive functions such as epoxy, carboxylic acid, or carboxylic acid anhydride groups. Examples of such polymers include terpolymers of ethylene, alkyl acrylate, and maleic anhydride or glycidyl methacrylate, such as Lotader® from SK Global Chemical, or polyolefins grafted with maleic anhydride, such as Orevac® from SK Global Chemical, as well as terpolymers of ethylene, alkyl acrylate, and (meth)acrylic acid. Also included are homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamino polyamide oligomers.

[0108] Functional polyolefin can exhibit selected functions from among polyepoxy, polyanhydrides, and polyisocyanates, in particular maleic polyanhydrides and polyepoxy.

[0109] Preferably, the functional polyolefin has a glass transition temperature (Tg) below -30°C, preferably below -35°C. The glass transition temperature (Tg) of the functional polyolefin in the composition according to the invention is determined according to ISO 6721-4:2019.

[0110] Additive

[0111] The content of additives is from 0.01 to 5% by weight relative to the total weight of the composition, preferably from 0.1 to 2% by weight relative to the total weight of the composition.

[0112] The additive can be chosen from a catalyst, an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a flame retardant, a nucleating agent, a chain extender and a colorant, preferably the additive is an antioxidant.

[0113] In one embodiment, the additive is chosen from a catalyst, an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a flame retardant, a chain extender and a colorant.

[0114] The antioxidant may in particular be a copper complex-based antioxidant of 0.01 to 5% by weight, preferably 0.01 to 1% by weight.

[0115] The antioxidant can be of organic or inorganic origin, preferably the antioxidant is of organic origin.

[0116] The thermal stabilizer can be an organic stabilizer or, more generally, a combination of organic stabilizers, such as a phenol-type primary antioxidant (for example, like that found in BASF's Irganox® 245, 1098, or 1010), or a phosphite-type secondary antioxidant. The UV stabilizer can be a HALS (Hindered Amine Light Stabilizer) or a UV blocker (for example, BASF's Tinuvin® 312).

[0117] The light stabilizer can be of the hindered amine type (for example, Tinuvin® 770 from BASF), a phenolic stabilizer or a phosphorus-based stabilizer.

[0118] The lubricant can be a fatty acid type lubricant such as stearic acid.

[0119] The flame retardant may be a halogen-free flame retardant, as described in US 2008 / 0274355, and in particular a phosphorus-based flame retardant, for example, a metal salt selected from a metal salt of phosphinic acid, in particular dialkyl phosphinate salts, including aluminum diethylphosphinate or aluminum diethylphosphinate, a metal salt of diphosphinic acid, a mixture of an aluminum phosphinate-based flame retardant and a nitrogen synergist or a mixture of an aluminum phosphinate-based flame retardant and a phosphorus synergist, a polymer containing at least one metal salt of phosphinic acid, in particular on an ammonium base such as an ammonium polyphosphate, sulfamate or pentaborate, or on a melamine base such as melamine, melamine salts, melamine pyrophosphates and melamine cyanurates, or based on cyanuric acid,another polymer containing at least one metallic salt of diphosphinic acid or red phosphorus, antimony oxide, zinc oxide, iron oxide, magnesium oxide, or metallic borates such as zinc borate, or phosphazene, phospham, or phosphoxynitride, or a mixture thereof. They may also be halogenated flame retardants such as brominated or polybrominated polystyrene, brominated polycarbonate, or brominated phenol.

[0120] The nucleating agent can be silica, alumina, clay or talc, especially talc.

[0121] Composition

[0122] Throughout the description, all percentages are given by weight.

[0123] The composition for manufacturing a three-dimensional object, preferably a tank for the transport, distribution or storage of gas, by extrusion blow molding, includes:

[0124] - from 70 to 99.49%, in particular from 89 to 98%, preferably from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0125] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin, having a glass transition temperature Tg below -25°C measured according to ISO 6721-4:2019;

[0126] -from 0.01 to 5% of at least one additive, preferably from 0.1 to 2% by weight relative to the total weight of the composition; the composition having a viscosity in the molten state greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0127] Preferably, the gas is hydrogen, nitrogen, carbon dioxide, natural gas, or methane. In one embodiment, plasticizers are excluded from said composition.

[0128] Preferably, the composition comprises less than 1%, preferably less than 0.5%, even more preferably 0% by weight of plasticizer relative to the total weight of said composition.

[0129] In one embodiment, plasticizers are excluded from said composition.

[0130] Preferably, the composition comprises less than 1%, preferably less than 0.5%, even more preferably 0% by weight of plasticizer relative to the total weight of said composition.

[0131] It has been observed that repeated hydrogen tank filling / emptying cycles can lead to plasticizer migration from the liner. The resulting exudate, which then appears on the liner surface, comes into contact with the hydrogen and can be carried away by the gas flow. This creates a risk of contamination of the downstream hydrogen distribution system. This distribution system, which includes, for example, pipes and valves, can become clogged, damaging the system's integrity. In one embodiment, the composition comprises less than 0.5%, preferably less than 0.2%, and even more preferably 0% by weight of carbonaceous fillers relative to the total weight of said composition.

[0132] These black carbon-based fillers prevent a satisfactory visual assessment of the liner once it has been manufactured. A white or natural-colored composition is preferred. Indeed, after manufacturing, the liners are visually inspected to ensure their physical integrity: absence of porosity, absence of leaks, a satisfactory surface appearance indicating homogeneity of composition, and homogeneity of color, in particular the absence of yellowing or foreign organic or inorganic contamination.

[0133] Furthermore, the presence of carbon fillers tends to decrease the ductile-brittle transition rate (TDF) of the composition.

[0134] Preferably, the composition does not contain graphene, i.e. the composition includes 0% by weight of graphene relative to the total weight of said composition.

[0135] According to another embodiment, the invention relates to a composition for manufacturing a three-dimensional object / reservoir for the transport, distribution or storage of gas, by extrusion blow molding, comprising:

[0136] - from 70 to 99.49%, in particular from 89 to 98%, especially from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0137] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin;

[0138] -from 0.01 to 5% of at least one additive, in particular from 0.1 to 2% by weight relative to the total weight of the composition; the composition presenting:

[0139] - a molten viscosity greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, and even more preferably greater than 150,000 Pa.s, as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%; and

[0140] - at least one tan 6 value greater than the tan 6 value of the polyamide(s) present in the composition over a temperature range between -80°C and -20°C as measured according to ISO 6721-4:2019 on dry samples, i.e. having a moisture content of less than 0.04% moisture measured according to ISO 15512:2019.

[0141] The term "polyamide(s) present in the composition" means a polyamide comprising the same monomers in the same proportions as the polyamide in the composition. If the composition comprises a mixture of polyamides, it means a mixture of polyamides comprising the same monomers as the polyamides in the composition in the same proportions.

[0142] In other words, neither viscosity nor the chain ends of the polyamide(s) in the polyamide matrix are taken into account in this comparison of tan 6 values.

[0143] In other words, the tan 6 value of the composition must be greater than the tan 6 value of the polyamide matrix of the composition. Indeed, it has been observed by the inventors that the presence of the functional polyolefin causes an increase in the tan 6 value observable in the -80°C to -20°C zone.

[0144] In this particular embodiment, the functional polyamides and polyolefins are those described above.

[0145] According to a first embodiment, the invention relates to a composition for the manufacture of a three-dimensional object / reservoir for the transport, distribution or storage of gas, by extrusion blow molding, comprising:

[0146] - from 70 to 99.49%, in particular from 89 to 98%, especially from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0147] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin;

[0148] -from 0.01 to 5% of at least one additive, in particular from 0.1 to 2% by weight relative to the total weight of the composition;

[0149] - less than 1%, preferably less than 0.5%, even more preferably 0% by weight of plasticizer relative to the total weight of said composition, the composition having a viscosity in the melt state greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0150] According to a second embodiment, the invention relates to a composition for manufacturing a three-dimensional object / reservoir for the transport, distribution or storage of gas, by extrusion blow molding, comprising:

[0151] - from 70 to 99.49%, in particular from 89 to 98%, especially from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0152] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin;

[0153] -from 0.01 to 5% of at least one additive, in particular from 0.1 to 2% by weight relative to the total weight of the composition; the composition does not contain graphene, preferably it does not contain carbon fillers, the composition having a viscosity in the molten state, greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0154] According to a first embodiment, the invention relates to a composition for the manufacture of a three-dimensional object / reservoir for the transport, distribution or storage of gas, by extrusion blow molding, comprising:

[0155] - from 70 to 99.49%, in particular from 89 to 98%, especially from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5;

[0156] - from 0.50% to 25%, preferably from 2 to 20%, even more preferably from 4 to 15% by weight relative to the total weight of the composition of at least one functional polyolefin;

[0157] -from 0.01 to 5% of at least one additive, in particular from 0.1 to 2% by weight relative to the total weight of the composition;

[0158] - less than 1%, preferably less than 0.5%, even more preferably 0% by weight of plasticizer relative to the total weight of said composition,

[0159] - the composition does not contain graphene, preferably it does not contain carbon fillers, the composition having a viscosity in the molten state greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0160] Method for preparing a composition

[0161] The process for preparing a composition according to the invention includes a compounding step under primary vacuum at a pressure ranging from 80,000 Pa to 0.1 Pa, preferably under secondary vacuum at a pressure ranging from 10,000 Pa to 1 Pa and at a temperature of the molten polymer greater than 280 °C, preferably greater than 300 °C, preferably ranging from 300 °C to 350 °C with an average residence time ranging from 20 seconds to 10 minutes, very advantageously from 45 seconds to 6 minutes.

[0162] Composition obtained by process

[0163] According to one embodiment, the composition according to the invention can be obtained by the preparation process described above.

[0164] The composition obtained by said process has, in the molten state, a viscosity greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s, as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

[0165] Use of the composition

[0166] The invention also relates to the use of the composition according to the invention to manufacture a three-dimensional object, preferably a tank.

[0167] Manufacturing method for the three-dimensional object The invention also relates to a manufacturing method for the three-dimensional object, preferably a tank, comprising an extrusion-blowing step of a composition according to the invention.

[0168] Preferably, the extrusion blow molding line of the extrusion-blowing stage is equipped with an accumulator.

[0169] Preferably, the blow molding extrusion step includes the following sub-steps:

[0170] 1. Feeding the extruder with the composition as defined above;

[0171] 2. Extrusion of the composition at a temperature of 205 to 290°C;

[0172] 3. Implementation and expulsion of a tubular parison;

[0173] 4. Cutting and pinching the parison;

[0174] 5. Blowing the parison.

[0175] Preferably, the composition placed in the extruder can be alone or mixed with additives or ground material from production scraps. The material can be in the form of granules (cylindrical or lenticular) or ground material: particles resulting from crushing and grinding production scraps. Preferably, the material is pre-dried to have a moisture content of less than 0.04%, as defined by ISO 15512:2019.

[0176] Next, the mixture is heated and melted in the extruder, which consists of a screw and a barrel. This step produces a homogeneous extrudate (molten material) at the desired temperature. The molten material then flows at a controlled rate through an extrusion head. This extrusion head can be cardioid, double cardioid, or finned, and may or may not include an accumulator. At the end of the extrusion head are a die and a punch, which shape the molten material into a cylindrical form called a tubular parison. The tubular parison is then expelled vertically.

[0177] Regarding the cutting and pinching stage of the parison, the mold consisting of at least two parts will close on the tubular parison, cutting and blocking the ends of the parison.

[0178] For the parison blowing stage, a gas, such as air or nitrogen, is injected into the parison to press it against the mold walls. This step allows the parison to be given the desired geometry.

[0179] The part is then cooled by contact with the temperature-controlled walls of the mold and by circulating the air present inside the part.

[0180] When the part has cooled sufficiently, preferably to a temperature between 80°C and 30°C, the mold is opened and the part is extracted for post-processing if necessary. The sprues are removed.

[0181] Preferably, a tubular parison has a length between 100 and 300cm, preferably between 120cm and 290cm, even more preferably between 150 and 280cm.

[0182] Preferably, the expulsion velocity of the parison is fixed from 0.01 to lm / s, preferably from 0.015 to 0.8 m / s, even more preferably from 0.02 to 0.6 m / s.

[0183] Preferably, the temperature of the extrudate is checked manually using a thermal probe.

[0184] Three-dimensional object The invention also relates to the manufacture of a three-dimensional object, preferably a tank, from the composition according to the invention by extrusion blow molding.

[0185] The invention also relates to a three-dimensional object, preferably a tank for the transport, distribution, or storage of gas, preferably hydrogen, comprising at least one sealing layer having a composition according to the invention. Preferably, the sealing layer is the innermost layer of the structure. It is then in direct contact with the fluid to be transported.

[0186] Preferably, the three-dimensional object is a hydrogen storage tank.

[0187] The three-dimensional object, preferably a tank, can have a volume greater than 20 L, preferably a volume greater than 100 L, and even more preferably greater than 300 L.

[0188] Preferably, the three-dimensional object, preferably the tank, comprises at least one layer of composite reinforcement, said innermost layer of composite reinforcement being welded or not, to said sealing layer according to the invention, preferably the outermost adjacent sealing layer.

[0189] The said composite reinforcement layer is therefore above the said sealing layer which is in contact with the gas, such as hydrogen.

[0190] The composite reinforcement layer can be made of a fibrous material in the form of continuous fibers impregnated by a composition comprising predominantly at least one polymer P.

[0191] One or more layers of composite reinforcement may be present.

[0192] Preferably, the first reinforcement layer is wrapped around the sealing layer, and the other layers, if present, are wrapped one on top of the other over the first reinforcement layer.

[0193] Preferably, only one layer of reinforcement is present and wrapped around said sealing layer.

[0194] In one embodiment, the number of reinforcement layers is from 1 to 10, preferably from 1 to 5, even more preferably from 1 to 3.

[0195] The term "majority" means that said at least one polymer P is present at more than 50% by weight relative to the total weight of said composition.

[0196] Preferably, said at least one major polymer P is present at more than 60% by weight, preferably at more than 70% by weight, preferably at more than 80% by weight, even more preferably at more than or equal to 90% by weight, relative to the total weight of said composition.

[0197] The composition may also include shock modifiers and / or additives.

[0198] Polymer P

[0199] Polymer P can be thermoplastic or thermosetting.

[0200] Thermoplastic polymer P: A thermoplastic, or thermoplastic polymer, is a material that is generally solid at room temperature, which can be semi-crystalline or amorphous, particularly semi-crystalline and which softens when the temperature increases, especially after passing its glass transition temperature (Tg) and flows at a higher temperature when it is amorphous, or which can exhibit a clear melting when passing its so-called melting temperature (Tf) when it is semi-crystalline, and which becomes solid again when the temperature decreases below its crystallization temperature, Te, (for a semi-crystalline) and below its glass transition temperature (for an amorphous).

[0201] Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013 respectively.

[0202] The number-average molecular weight Mn of said thermoplastic polymer is preferably in the range of 10,000 to 40,000, preferably from 10,000 to 30,000. These Mn values ​​can correspond to inherent viscosities greater than or equal to 0.8 as determined in m-cresol according to ISO 307:2007 but by changing the solvent (using m-cresol instead of sulfuric acid and the temperature being 20°C).

[0203] Examples of suitable semi-crystalline thermoplastic polymers in the present invention include: polyamides, particularly those with an aromatic and / or cycloaliphatic structure, including copolymers such as polyamide-polyether copolymers, polyesters, polyaryletherketones (PAEK), polyetheretherketones (PEEK), polyetherketone ketones (PEKK), polyetherketoneetherketone ketones (PEKEKK), polyimides, particularly polyetherimides (PEI) or polyamide-imides, polyylsulfones (PSU), particularly polyarylsulfones such as polyphenylsulfones (PPSU), and polyethersulfones (PES). Semi-crystalline polymers are particularly preferred, especially polyamides and their semi-crystalline copolymers.

[0204] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0205] Polyamide can be a homopolyamide or a copolyamide or a mixture of these.

[0206] Advantageously, semi-crystalline polyamides are semi-aromatic polyamides, in particular a semi-aromatic polyamide of formula X / YAr, as described in EP1505099, in particular a semi-aromatic polyamide of formula A / XT in which A is selected from a motif obtained from an amino acid, a motif obtained from a lactam and a motif corresponding to the formula (Ca diamine). (Cb diacid), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b each being from 4 to 36, advantageously from 9 to 18, the motif (Ca diamine) being chosen from aliphatic diamines, linear or branched, cycloaliphatic diamines and alkylaromatic diamines and the motif (Cb diacid) being chosen from aliphatic diacids, linear or branched, cycloaliphatic diacids and aromatic diacids; X.T denotes a motif obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being from 5 to 36, advantageously from 9 to 18, in particular a polyamide of formula A / 5T, A / 6T, A / 9T, A / 10T or A / 11T, A being as defined above, in particular a polyamide selected from PA MPMDT / 6T, PA11 / 10T, PA 5T / 10T, PA 11 / BACT, PA 11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 11 / MXDT / 10T, one 11 / 5T / 10T.

[0207] T corresponds to terephthalic acid, MXD to m-xylylenediamine, MPMD to methylpentamethylenediamine, and BAC to bis(aminomethyl)cyclohexane. The aforementioned semi-aromatic polyamides defined above have, in particular, a Tg greater than or equal to 80°C.

[0208] Thermosetting polymer P:

[0209] Thermosetting polymers are selected from epoxy or epoxy-based resins, polyesters, vinyl esters, polyisocyanate-based resins, in particular polyisocyanurates, and polyurethanes, or a mixture thereof, in particular epoxy or epoxy-based resins or a polyisocyanate-based resin, in particular polyisocyanurates.

[0210] Advantageously, each layer of composite reinforcement is made of a composition comprising the same type of polymer, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0211] The said composition comprising the said polymer P2j may be transparent to radiation suitable for welding.

[0212] Regarding the constituent fibers of said fibrous material, these are in particular fibers of mineral, organic or vegetable origin.

[0213] Advantageously, the said fibrous material can be siped or unsiled.

[0214] The said fibrous material may therefore include up to 3.5% by weight of a material of an organic nature (such as thermosetting resin or thermoplastic) called ensimage.

[0215] Examples of mineral-based fibers include carbon fibers, glass fibers, basalt or basalt-based fibers, silica fibers, and silicon carbide fibers. Examples of organic-based fibers include thermoplastic or thermosetting polymer-based fibers, such as semi-aromatic polyamide fibers, aramid fibers, polyester fibers, and polyolefin fibers. Preferably, these fibers are based on an amorphous thermoplastic polymer and have a glass transition temperature (Tg) higher than the Tg of the amorphous thermoplastic polymer or blend of the pre-impregnation matrix, or higher than the Tf of the semi-crystalline thermoplastic polymer or blend of the pre-impregnation matrix.Advantageously, these fibers are based on semi-crystalline thermoplastic polymers and have a melting point (Tf) higher than the melting point (Tg) of the amorphous thermoplastic polymer or blend of polymers used in the pre-impregnation matrix, or higher than the Tf of the semi-crystalline thermoplastic polymer or blend of polymers used in the pre-impregnation matrix. Therefore, there is no risk of melting of the organic fibers that make up the fibrous material during impregnation by the thermoplastic matrix of the final composite. Examples of plant-based fibers include natural fibers made from flax, hemp, lignin, bamboo, silk (particularly spider silk), sisal, and other cellulosic fibers, especially viscose.These plant-based fibers can be used pure, treated, or coated with a layer of coating to facilitate adhesion and impregnation of the thermoplastic polymer matrix.

[0216] The fibrous material can also be a fabric, braided or woven with fibers.

[0217] It can also correspond to fibers with retaining threads.

[0218] These constituent fibers can be used alone or in mixtures. Thus, organic fibers can be mixed with mineral fibers to be pre-impregnated with thermoplastic polymer powder and form the pre-impregnated fibrous material.

[0219] Organic fiber rovings are available in various weights and geometries. Furthermore, the constituent fibers of the fibrous material may be a blend of these reinforcing fibers with different geometries. The fibers are continuous.

[0220] Preferably the fibrous material is chosen from glass fibers, carbon fibers, basalt or basalt-based fibers, or a mixture thereof, in particular carbon fibers.

[0221] It is used in the form of a single strand or several strands.

[0222] Use of the three-dimensional object

[0223] The invention also relates to the use of the three-dimensional object according to the invention for the transport, distribution or storage of gas, preferably hydrogen, nitrogen, carbon dioxide, natural gas, methane, and even more preferably hydrogen.

[0224] EXAMPLES l. Preparation of compositions

[0225] The comparative IEC composition and the compositions according to the invention (Cil to CI6) in Table 1 below were prepared by compounding under the following conditions.

[0226] The compositions were manufactured using a ZSK 40 mm twin-screw extruder (Coperion). The barrel temperature was set at 280 °C and the screw speed was 300 rpm with a throughput of 60 kg / h. The compositions were produced under a vacuum of 400 mbar. The PA6 polyamide has a moisture content greater than 0.5%. The other polyamides have a moisture content less than 0.5%, as defined by ISO 15512:2019.

[0227]

[0228] Table 1

[0229] The PA6 used is a polyamide 6 with a number-average molar mass of 20,000 g / mol 1 .

[0230] The PA610 used is a polyamide 610 with a number-average molar mass of 20,000 g / mol 1 .

[0231] The PA612 used is a polyamide 612 with a number-average molar mass of 20,000 g / mol 1 .

[0232] The PAU used is a polyamide 11 with a number-average molar mass of 42,000 g / mol 1 .

[0233] The PA12 used is a polyamide 12 with a number-average molar mass of 35,000 g / mol 1 .

[0234] Lotader® 3410 is a copolymerized polyolefin of maleic anhydride, ethylene and butyl acrylate with a Tg of -14 °C, and sold by SK functional polymer.

[0235] Tafmer® MH5020 C is a grafted polyolefin, exhibiting a Tg of -40 °C, and sold by Mitsui Chemicals.

[0236] Anox NBD TL 89 stabilizer is sold by SI group.

[0237] The molten viscosity of the composition was measured in a planar-planar geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%. In particular, it was measured using an Ares G2 Rotational Rheometer equipped with a 25mm planar-planar geometry at a temperature of 250°C, at 0.292 rad / s (residence time before launch 5 min under nitrogen, strain of 2%, sweep from 628 rad / s to 0.062 rad / s and 3 points per decade, taking one point every 3 cycles, gap of 1.5mm).

[0238] 2. Evaluation of compositions

[0239] The following properties were measured:

[0240] The Rheotens force

[0241] The Rheotens force is determined using a Gottfert Rheotens 71.97 apparatus. A Rheotens apparatus is a device equipped with toothed wheels that pull on a rod at the outlet of a Gottfert Rheotester 2000 capillary rheometer. The shear rate at the capillary is 100 s⁻¹, the die has a length (L / D) of 30 mm and a diameter (D) of 1 mm, the temperature is 250°C, the distance between the rod outlet and the toothed wheel axis is 105 mm, and the wheel acceleration is 2.4 mm / s². This force determines the melt strength of the polyamide; the higher the force, the less the polyamide flows. The polymer is melted at 250°C to perform the Rheotens force analysis.

[0242] A Rheotens force greater than or equal to 0.06mN is acceptable.

[0243] Water replenishment

[0244] Water reabsorption is determined either in an oven under a controlled atmosphere at 100% RH or in water, in all cases after saturation at 70°C. This water reabsorption is measured by weighing the sample at 23°C at regular sampling times, spaced several days apart, until an equilibrium state is observed. This equilibrium is reached when the sample mass becomes constant (within the measurement uncertainty) for three consecutive sampling times. In the case of conditioning in water, the equilibrium reached corresponds to the water saturation of the polymer at a temperature of 70°C.

[0245] A water recovery rate of less than 5% is acceptable.

[0246] The parish's attire

[0247] The parison's stability allows us to analyze the material's ability to counteract the effect of gravity. Under its weight, a parison extruded horizontally or vertically will flow, thus changing its dimensions.

[0248] The parisons are prepared as follows.

[0249] The granule compositions were extruded on an AX 430 St Blow Molding extrusion line equipped with a 5L accumulator. The granules were pre-dried to a moisture content of less than 0.08%. The moisture content of the granules was measured according to ISO 15512:2019.

[0250] A blow molding extrusion line includes an extruder upstream, whose role is to heat and melt the granules to obtain a homogeneous extrudate at a controlled temperature. The extrudate temperature is manually checked using a temperature probe. The mixture then flows, respectively, into an accumulator, a die, and a punch, which together form a tube of molten material called a tubular parison. The tubular parison has a temperature of 240 to 255°C.

[0251] The paraison holding measurements were carried out as follows:

[0252] A tubular parison weighing 1.2 kg and 190 mm long is extruded with an extrusion velocity set at 0.1 m / s. The diameter of the parison is measured 10 cm below the die. The time required for the parison length to increase by 60% due to creep is measured. A long time is indicative of a viscous material. The temperature is chosen based on the polymer's flow characteristics to minimize parison creep.

[0253] A vertical parison retention of the composition after compounding of 35 seconds or more is acceptable. The swelling rate

[0254] The swelling rate is measured on a tubular parison obtained according to the process described previously in the parison strength test.

[0255] Swelling rate measurements were performed as follows:

[0256] A 25 cm tubular parison is extruded using a blow molding extrusion line as described above. The molten composition expulsion velocity between the die and the punch is set at 0 lm / s, and the extrudate temperature is manually checked using a temperature probe. The parison diameter is measured 10 cm below the die. Five measurements are taken to obtain an average. The swelling ratio is calculated as the ratio of the measured parison diameter to the die diameter. The temperature is selected based on the polymer's flow characteristics to minimize parison creep.

[0257] An extruder swell rate of the compounding composition greater than 1.10 is acceptable, preferably greater than 1.15, preferably greater than 1.20.

[0258] Crack propagation fatigue tests

[0259] The test specimens are prepared with the compositions described above. They are punched from extruded strips. The geometries are DIN 53448 type pull-up dumbbells with a length of 80 mm and a width of 14 mm, with a usable calibrated cross-section of 30 mm in length and 10 mm in width. The specimens are cut from the 4 mm thick extruded strip. A fine notch, 0.8 mm deep, is made on each of the 10 mm wide faces, at the center of the calibrated cross-section. The specimen is therefore doubly notched to a total depth of 1.6 mm in the 4 mm thick extruded strip.

[0260] The samples are dried before mechanical characterization at 80°C under vacuum for 3 days.

[0261] Mechanical tests are performed using an MTS 370 or MTS 810 dynamometer, equipped with a 10 or 25 kN load cell and a crosshead displacement sensor, also fitted with clamping jaws. The reference distance L0 between the jaws is set at 30 mm, and the tests are carried out at ambient temperature in a climate-controlled laboratory at 23°C.

[0262] The characterization test is controlled by displacement of the crossbeam. The fatigue cycling test is performed at a frequency of 1 Hz, meaning that one load and unload cycle lasts 1 second. The maximum displacement limit is set at the beginning of the test. This displacement limit, which corresponds to a deformation limit, is then varied for each subsequent fatigue test.

[0263] The number of cycles until the double-notched specimen breaks is recorded for this maximum deformation limit. After the specimen breaks, the depth of the notches on each face is precisely measured using an optical microscope (30x zoom).

[0264] Determining the number of cycles to failure as a function of the elongation intensity factor

[0265] During fatigue testing with a double-notched specimen, crack propagation occurs in the same plane as the notches. The strain intensity factor is calculated from the imposed deformation and the notch depth. A curve can then be plotted showing the number of cycles to failure as a function of this strain intensity factor.

[0266] The higher the number of cycles to failure, the better the material's performance.

[0267] A number of cycles to failure for DK = 0.007 sqrt (m) greater than 500 is acceptable.

[0268] Fatigue tests by initiation of a critical defect

[0269] The test specimens are machined from the thickness of extruded strips. The machined geometries are axisymmetric hourglass-shaped dumbbells with a diameter of 8 mm and a length of 60 mm, type R4, with a minimum diameter of 4 mm and a radius of curvature of 4 mm. The specimens are taken from the center of the 8 mm thick extruded strip. The samples are dried at 80°C under vacuum for 3 days before mechanical characterization.

[0270] Mechanical tests are performed using an MTS 370 dynamometer, equipped with a 10 kN load cell and a crosshead displacement sensor, also fitted with clamping jaws. The reference distance L0 between the jaws is set at 10 mm, and the tests are carried out at ambient temperature in a climate-controlled laboratory at 23°C.

[0271] The characterization test is driven by displacement of the crossbeam. The fatigue cycling test is performed at a frequency of 1 Hz, meaning that one load and unload cycle lasts 1 second. The maximum displacement limit, corresponding to the desired maximum load limit, is set at the beginning of the test. The maximum displacement limit is then varied for each subsequent fatigue test.

[0272] For this maximum load limit, the number of cycles until the axisymmetric specimen breaks is recorded.

[0273] Determining the number of cycles to failure based on the maximum load

[0274] During fatigue testing with an axisymmetric hourglass specimen, the maximum material deformation is highly localized at the center of the specimen, corresponding to a critical defect. The cycle-to-failure curve of this type of hourglass specimen as a function of the maximum load allows for the evaluation of the material's fatigue performance by the initiation of a critical defect.

[0275] The higher the number of cycles to failure, the better the material's performance.

[0276] A number of cycles before failure greater than 100,000 is acceptable.

[0277] Ductile-Brittle Transition

[0278] The test specimens are machined from the same thickness as the extruded blow-molded liners. The machined geometry is an 80 x 10 x 4 mm bar cut from this thickness. A notch is made in the center of the bar. This is a 4.5 mm deep V-shaped notch (equivalent to ISO 179-1 / leA) supplemented by a 0.5 mm razor-blade notch. The notches are made on the 10 mm wide face. The samples are dried at 80°C under vacuum for 3 days before mechanical characterization.

[0279] Mechanical tests are performed using an MTS370 dynamometer equipped with a 10 kN load cell and a crossbeam displacement sensor, also fitted with a three-point bending setup. The distance between supports is set at 40 mm, and the test temperature at -60°C. The characterization test is driven by crossbeam displacement. The crossbeam displacement speed (and therefore that of the central support) is adjusted to cover a range between 0.001 mm / s and 50 mm / s. This speed is set at the beginning of the loading test. The crossbeam displacement and the resulting force are then recorded at this fixed displacement speed.

[0280] Determination of the ductile / brittle transition rate at -60°C (in s 1 )

[0281] This curve allows us to determine whether the material's behavior at -60°C and a fixed loading speed is ductile (i.e., a gradual decrease in force after passing a threshold or local maximum) or brittle (i.e., a sudden decrease in force after passing a threshold or local maximum). The crosshead speed is adjusted incrementally to identify the speed range (mm / s) that allows the transition between the ductile and brittle behavior of the tested sample.

[0282] Finally, we can convert this ductile-brittle transition velocity into a strain velocity using the following approximation: V(sl) = (l / 2)*(6*Width*Transverse velocity) / (Support spacing) 2 The higher this value, the better the material performs.

[0283] A ductile / brittle transition strain rate greater than 1 s-1 is acceptable.

[0284] Sample Recyclability

[0285] The recyclability of a composition refers to its ability to be extruded multiple times to create a three-dimensional object using blow molding without any loss of mechanical properties. It is well known to those skilled in the art that the blow molding process generates at least 10% waste by weight (e.g., carrots). This waste can be pre-cut and reground to generate particles of a size comparable to pellets. These particles are then incorporated into the virgin granules to extrude a three-dimensional object using blow molding. A composition is considered non-recyclable if it will generate defects and inhomogeneities (gelling, degradation, etc.) within the part, resulting in a loss of at least 20% of its mechanical properties.

[0286] Dynamic Mechanical Analysis (DMA)

[0287] DMA mechanical tests are performed on a specimen with a thickness of 1 mm at a tensile strain of 0.1%, at a frequency of 1 Hz, and at a heating rate of 2°C min⁻¹, according to ISO 6721-4:2019. These tests yield a tan θ curve as a function of temperature. The specimens are first dried at 80°C under vacuum to achieve a moisture content of less than 0.04% by weight. The moisture content is measured according to ISO 15512:2019.

[0288] The results are shown in Figure 1 and Table 4 below. Figure 1 expresses tan 6 as a function of temperature in °C. These results compare:

[0289] -a comparative composition consisting of the PAU matrix present in the Cil and CI6 compositions,

[0290] -the composition according to the invention Cil and

[0291] -the composition according to invention CI6.

[0292] The results of the compositions are detailed in tables 2 to 4.

[0293] Table 2

[0294] Table 3

[0295] Table 4

[0296] The results show that the compositions according to the invention make it possible to obtain compositions presenting the best compromise on the different characteristics such as the strength of rheotens, the water reabsorption, the stability of the parison and the recyclability of the composition.

[0297] Furthermore, the compositions according to the invention provide satisfactory properties, such as swelling and mechanical fatigue resistance (low crack propagation and initiation of critical defects). The results of the samples analyzed by DMA are detailed in Figure 1. These results show that at least one tan 6 value of the compositions comprising a functional polyolefin is greater than the tan 6 value of the polymer alone at temperatures of -50°C as well as in the temperature range between -40 and -60°C.

Claims

1. CLAIMS 1. Composition for the manufacture of a three-dimensional object, preferably a tank for the transport, distribution or storage of gas, by extrusion blow molding, comprising: - from 70 to 99.49%, preferably from 89 to 98%, even more preferably from 91 to 96% by weight relative to the total weight of the composition of at least one polyamide having a number of carbons per nitrogen atom greater than or equal to 6.5, preferably greater than or equal to 7.5, even more preferably greater than 8.5; - from 0.50% to 25%, preferably from 2% to 20%, and even more preferably from 4% to 15% by weight relative to the total weight of the composition of at least one functional polyolefin, having a glass transition temperature T g less than -25°C measured according to ISO 6721-4:2019; -from 0.01 to 5% of at least one additive, preferably from 0.1 to 2% by weight relative to the total weight of the composition; the composition having a viscosity in the molten state greater than 40,000 Pa.s, preferably greater than 50,000 Pa.s, even more preferably greater than 150,000 Pa.s as measured in plane-plane geometry according to ISO 6721-10:2015 at a temperature of 250°C, a frequency of 0.292 rad / s and a strain of 2%.

2. Composition according to claim 1, characterized in that it comprises a polyamide with an average molar mass greater than 15,000 g / mol 1 , preferably greater than 20,000 g / mol 1 , preferably in a manner exceeding 30,000 g.mol 1 .

3. Composition according to any one of the preceding claims, characterized in that it comprises a polyamide selected from PA610, PA612, PA 614, PA 10, PAU and PA12, preferably from PA610, PA612, PAU and PA12, and mixtures thereof.

4. Composition according to any one of the preceding claims, characterized in that said functional polyolefin has a glass transition temperature T g less than -30°C, preferably less than -35°C as measured according to ISO 6721-4:2019.

5. Composition according to any one of the preceding claims, characterized in that said functional polyolefin has epoxy, anhydride and / or isocyanate functions, preferably maleic anhydride functions.

6. Composition according to any one of the preceding claims, characterized in that said functional polyolefin comprises grafted functions.

7. Composition according to any one of the preceding claims, characterized in that the additive is selected from an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a flame retardant, a nucleating agent, a chain extender and a colorant, preferably the additive is an antioxidant.

8. A method for preparing a composition as defined in any one of claims 1 to 7, characterized in that it comprises a primary vacuum compounding step at a pressure ranging from 80,000 Pa to 0.1 Pa, at a molten polymer temperature above 280 °C with an average residence time ranging from 20 seconds to 10 minutes.

9. Use of the composition as defined in any one of claims 1 to 7, to manufacture a three-dimensional object, preferably a tank, by extrusion blow molding.

10. Method for manufacturing a three-dimensional object, preferably a tank, characterized in that it comprises an extrusion-blowing step, of a composition as defined in any one of claims 1 to 7.

11. Three-dimensional object, preferably a tank, manufactured from a composition as defined in any one of claims 1 to 7 by extrusion blow molding.

12. Three-dimensional object, preferably a tank, intended for the transport, distribution or storage of gas, preferably dihydrogen, characterized in that it comprises at least one sealing layer comprising a composition as defined in any one of claims 1 to 7.

13. Object according to claim 12, characterized in that it is a hydrogen storage tank.

14. Object according to claim 12 or 13, characterized in that it comprises at least one composite reinforcement layer, said innermost composite reinforcement layer being welded or not, to said sealing layer according to claim 12, preferably the outermost adjacent sealing layer.

15. Object according to any one of claims 12 to 14, characterized in that it has a volume greater than 20 L, preferably a volume greater than 100 L, even more preferably greater than 300 L.

16. Use of the three-dimensional object as defined in any one of claims 11 to 15, for the transport, distribution or storage of gas, preferably hydrogen, nitrogen, carbon dioxide, natural gas, methane, even more preferably hydrogen.

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