Flame-retardant polymeric material composition for use in 3D printing

Abstract

The invention relates to a flame-retardant material composition for use in 3D printing, comprising or consisting of: - 30% to 60% by weight, relative to the total weight of the composition, of at least one polyolefin from renewable or petroleum-based resources; - 5% to 20% by weight, relative to the total weight of the composition, of at least one fibrous material; - 20% to 50% by weight, relative to the total weight of the composition, of at least one intumescent agent acting in the condensed phase; - 2.5% to 20% by weight, relative to the total weight of the composition, of at least one flame retardant acting in the gas phase; - 0.5% to 5% by weight, relative to the total weight of the composition, of at least one inorganic compound selected from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more thereof.

Description

[0001] Title: Flame-retardant polymer material composition suitable for 3D printing

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] The field of the invention is that of flame retardant materials.

[0004]

[0002] More specifically, the invention relates to a 3D printable flame retardant material composition complying with the EN45545 fire safety standard and its specific fire / smoke requirement HL2-R1 for applications in the railway industry. The invention also relates to a method for manufacturing a flame retardant material comprising the composition which is the subject of the present invention as well as a method for preparing a three-dimensional shaped product by means of 3D printing, from the flame retardant material composition which is the subject of the present invention.

[0005] STATE OF THE ART

[0006]

[0003] 3D printing, also called additive manufacturing, is a shaping process, intended to produce objects by adding layer by layer a material corresponding to the successive cuts of a 3D model. This technology would be of great interest in many industrial sectors such as the railway sector. Indeed, players in the transport industry are constantly looking for solutions to maintenance problems. The stakes are colossal since the immobilization of a train costs several tens of thousands of euros per day. Consequently, the supply of spare parts is of capital importance. To this end, the railway industry has identified additive manufacturing in recent years as an effective solution to the maintenance problem, since this process offers considerable advantages.These include the replacement of obsolete parts (ability to produce complex shapes), short manufacturing lead times, long-term cost savings due to the absence of specific molds or tools, the production of small volumes, or the opportunity to review the design of certain parts to integrate new functionalities and / or make them more durable.

[0007]

[0004] On the other hand, despite these clear advantages, the use of 3D printing for railway spare parts currently remains very limited and mainly dedicated to rapid prototyping. Indeed, additive manufacturing is still limited to a narrow range of materials, with a very high immediate investment cost in materials and machines. The example of the SNCF confirms this situation since a third of the 150,000 references in the catalog could be 3D printed, yet only around a hundred references are in operation today because the performance required for these components is not yet achievable via such a manufacturing process.

[0008]

[0005] For a component to be used by a railway operator, the materials must be compatible with the railway industry's fire safety standards: EN 45545 (AFNOR, Railway applications - Fire protection in railway vehicles - Part 2: Requirements for the fire behavior of materials and components. 2013). This regulation serves to reduce the probability of fire occurring on board railway vehicles, limit the spread of fire in the event of a fire, minimize the consequences of the fire on passengers and equip and arrange the vehicle in such a way as to facilitate the exit of passengers in the event of a fire, so that they can reach a safe area without external assistance when the fire is declared.

[0009]

[0006] The EN 45545 standard is structured according to the vehicle and the part used. It lists three risk levels ("Hazard Level" in English terminology) HL1, HL2 and HL3 according to the categories, types and design of the vehicles. Concerning the parts, there are, for the standard in force dating from 2020, 28 types of requirements ("Requirements" in English terminology) R1 to R28 depending on the application, the final use of the part and its location in the vehicle. Each requirement is accompanied by a series of tests to be carried out for each part concerned, in order to determine its behavior in the face of fire, smoke and toxicity.

[0010]

[0007] For example, requirement R1 at hazard level HL2 includes three fire scenarios to be validated. All the criteria to be achieved are summarized in Table 1 below:

[0011] [Table 1]

[0012] Table 1: Fire performance to be achieved to meet the HL2-R1 requirement of standard EN 45545.

[0013]

[0008] All the criteria to be achieved (summarized in Table 1) highlight technological challenges. Among them, we can first identify a barrier linked to the lack of knowledge and studies on the development of flame-retardant materials, 3D printable and compatible with the EN 45545 standard. This fire / smoke standard, adapted to the railway sector, requires the materials developed to meet criteria when exposed to certain very specific fire scenarios. In particular, it is possible to cite the lateral flame propagation test (ISO 5658-2) and the smoke production test (ISO 5659-2). Due to this lack of scientific hindsight, the prediction of the fire behavior of the materials developed is complex and requires in-depth study. Few tests study the gases or smoke emitted during exposure to the fire scenario.In addition, the vertical position of the lateral flame spread test requires the tested material to have a certain structure to prevent it from flowing, burning and allowing the flame to spread. In addition, the samples are generally subjected to a defined heat flux (as in the case of the cone calorimeter test (ISO5660-1)). In the case of the lateral flame spread test (ISO 5658-2), the materials developed must act on a more or less high set of fluxes (Critical Extinction Flux (CFE) ranging from 50kW / m. 2 at 0 kW / m 2). This requires the flame retardants used to act quickly and under different thermal constraints. A very specific combination of components is therefore necessary to achieve the various flame retardant performances required by the HL2-R1 criterion of EN 45545. However, it is important to note that some companies offer materials that comply with this standard, such as Stratasys with Antero 800 NA, which is a thermoplastic based on Polyetherketoneketone (PEKK) (A. Essop, “Stratasys announces rail industry solution for 3D printing spare train parts”, 3D printing industry, 2019) or Mitsubishi with a flame retardant polycarbonate, Xantar MX4500. Despite this, few solutions exist and all those proposed are very expensive and not always suitable because they combine a multitude of performances when only one is sometimes necessary to comply with the standard.The use of these materials, without other alternatives, is therefore not profitable and is detrimental to the expansion of 3D printing technology.

[0014]

[0009] In addition, the size of the test pieces required by the lateral flame propagation test (ISO 5658-2) is not suitable for most conventional shaping processes and 3D technologies, particularly 3D printing processes. The creation of specific molds or tools to achieve the desired dimension is therefore essential to design for technologies other than 3D printing, but this proves to be very expensive. As far as 3D printing technologies are concerned, the vast majority are equipped with a 300*300 mm plate. 2surface area, which would therefore involve modifying the size of said technologies or at least their plates or else, proceeding with gluing segments of test specimens in order to reach the standardized size. This brake therefore requires reflection and research on the design and conception of these test specimens.

[0015]

[0010] Another obstacle related to the 3D printing shaping process is also important to mention. This process by deposition of fused filament has created anisotropy and porosity that can potentially influence the functional properties of the materials tested. In addition, a challenge related to the printing of certain polymer matrices such as polyolefins (polypropylene (PP) or polyethylene (PE)) for example must be considered. Warping phenomena, uncontrolled flow of the material to be printed ("stringing" in Anglo-Saxon terminology) or adhesion problems can occur and must be addressed to ensure the printability of the developed flame-retardant material.

[0016]

[0011] Patent application US20180127567 relates to compositions for the manufacture of public transport vehicle components having improved smoke density and / or heat release performance. This patent application discloses compositions consisting of polypropylene, glass fibers and a flame retardant composition consisting of a mixture of an organophosphorus compound, an organic phosphoric acid compound and zinc oxide. More specifically, it discloses a composition consisting of 45% by weight of polypropylene, 30% of glass fibers and 25% of ADK-STAB FP2200. The inventors of the present invention tested the fire resistance of an object obtained from this composition. The fire results obtained (Critical Extinction Energy Flux according to standard 5658-2 (CFE) = 0 kW / m 2 and maximum average heat emission rate according to standard 5658-2 (MAHRE) = 47 ± 3 kW / m 2are significantly below the values ​​required to comply with the EN45545 railway standard and in particular the R1 requirement of the HL2 hazard level of the said standard. Furthermore, this patent application does not disclose the possibility of producing a part by 3D printing.

[0017]

[0012] To benefit from advantages such as the cost savings related to the choice of compounds used for the materials used in the railway sector and the advantages related to 3D printing for replacing obsolete parts, the short manufacturing time, the long-term cost savings due to the absence of specific molds or tools, the possibility of producing small volumes, or even the opportunity to review the design of certain parts in the railway sector, it would therefore be appropriate to find new compositions of 3D printable materials, the compounds of which have the lowest possible cost, and having a low reaction to fire while limiting the spread of fire and minimizing the opacity and toxicity of the smoke released to comply with the railway standard EN45545 and in particular the requirement R1 of the hazard level HL2 of said standard.

[0018] STATEMENT OF THE INVENTION

[0019]

[0013] To this end, according to a first aspect, the present invention relates to a flame-retardant material composition comprising or consisting of:

[0020] - 30% to 60% by weight of at least one polyolefin from a renewable or petro-sourced resource relative to the total weight of the composition, - 5% to 20% by weight of at least one fibrous material relative to the total weight of the composition,

[0021] - 20% to 50% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition,

[0022] - 2.5% to 20% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0023] - 0.5% to 5% by weight of at least one inorganic compound chosen from zeolites (or zeolitic materials), montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these, relative to the total weight of the composition.

[0024]

[0014] The nature of this composition gives the material which comprises it or is made of it a very good flame retardant property meeting the railway industry standard EN 45545 and particularly the HL2-R1 requirement level. Indeed, the composition has a critical extinction flux (CFE) greater than or equal to 20 kW / m 2 , a maximum average heat emission rate (MAHRE) less than or equal to 90 kW / m 2 , as well as, when exposed to a radiative flux of 50 kW / m 2, it has a cumulative value of specific optical densities during the first 4 minutes of exposure (VOF4) less than or equal to 600, an optical density of the test chamber at 4 min during the test multiplied by a factor which depends on the instrumentation and the size of the specimen (Ds(4)) less than or equal to 300 and a conventional toxicity index (ITCg) less than or equal to 0.9.

[0025]

[0015] Furthermore, such a material comprising or consisting of this composition may be advantageously used for the manufacture of parts by 3D printing. As used herein, the term "3D printing" may be understood in the broadest sense as any process that constructs a three-dimensional (3D) object from a computer-aided design (CAD) model, from a scan or other information or by 3D drawing or any other means to generate a specific 3D shape. Typically, but not necessarily, 3D printing is performed by successively adding material layer by layer, which may be referred to as additive manufacturing. 3D printing may be distinguished from casting processes, forging processes, milling processes and conventional machining.

[0016] Furthermore, the compounds used to produce the composition which is the subject of the present invention have an advantageously low cost compared to that of the compounds of the flame retardant compositions of the prior art.

[0026]

[0017] To this end, the invention further relates to the use of said flame-retardant material composition above for 3D printing.

[0027]

[0018] In preferred embodiments of the present invention, the flame retardant material composition comprises:

[0028] - 35% to 55% by weight of at least one polyolefin from a renewable or petroleum-sourced resource relative to the total weight of the composition,

[0029] - 8% to 12% by weight of at least one fibrous material relative to the total weight of the composition,

[0030] - 35% to 42% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition,

[0031] - 7% to 15% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0032] - 1% to 3% by weight of at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these relative to the total weight of the composition.

[0033]

[0019] According to a particularly preferred embodiment of the present invention, the flame retardant material composition comprises:

[0034] - 40% by weight of at least one polyolefin from a renewable or petroleum-sourced resource relative to the total weight of the composition,

[0035] - 10% by weight of at least one fibrous material relative to the total weight of the composition,

[0036] - 38% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition,

[0037] - 10% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0038] - 2% by weight of at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these, relative to the total weight of the composition.

[0020] It is with the proportions of each of these compounds that the composition which is the subject of the present invention gives the material which comprises it or is made of it the best flame retardant property meeting the railway industry standard EN 45545 and particularly the HL2-R1 requirement level.

[0039]

[0021] In particular embodiments, the invention further meets the following characteristics, implemented separately or in each of their technically operative combinations.

[0040]

[0022] In particular embodiments of the present invention, the polyolefin from a renewable or petroleum-sourced resource is a polyethylene, preferably a high-density polyethylene.

[0041]

[0023] In the present invention, the term “fibrous material” means a material comprising fibers. The fibrous material preferably comprises short fibers and / or long fibers, or continuous fibers. Preferably, the fibrous material comprises short fibers. Short fibers are understood to mean fibers with a length of between 1 μm and 800 μm. Long fibers are understood to mean fibers with a length greater than 800 μm.

[0042]

[0024] In particular embodiments of the present invention, the fibrous material is selected from fiberglass, aramid fiber, basalt fiber, cellulose fiber, flax fiber and carbon fiber. Preferably, the fibrous material is carbon fiber.

[0043]

[0025] In particular embodiments of the present invention, said condensed phase intumescent agent is a phosphate-based compound. Preferably, said condensed phase intumescent agent is selected from a melamine phosphate and a mixture of a piperazine pyrophosphate with at least one additive selected from a melamine phosphate, zinc oxide, a melamine poly(zinc phosphate) and a melamine poly(aluminum phosphate). The melamine phosphate is preferably selected from a melamine pyrophosphate, a melamine orthophosphate and a melamine polyphosphate. The mixture preferably comprises between 45% and 65% by weight of piperazine pyrophosphate and between 30% and 55% by weight of said at least one additive, relative to the total weight of the mixture.Due to the improved flame retardant capacity obtained for the composition, the intumescent agent acting in the condensed phase is preferably a mixture of a piperazine pyrophosphate with melamine phosphate and zinc oxide. Said mixture then preferably comprises between 45% and 65%, preferably between 50% and 60%, by weight of piperazine pyrophosphate, between 30% and 50%, preferably between 35% and 45%, by weight of melamine phosphate, and between 1% and 10%, preferably between 3% and 6%, by weight of zinc oxide, relative to the total weight of said mixture. A product comprising piperazine pyrophosphate and these two additives in the indicated mass quantities, known under the name ADK STAB FP-2500S and marketed by the company ADEKA, can in particular be used as an intumescent agent acting in the condensed phase in the composition which is the subject of the present invention.

[0044]

[0026] In particular embodiments of the present invention, the flame retardant material composition which is the subject of the present invention further comprises expanded graphite. Preferably, the expanded graphite is present in the composition between 5% and 20% by weight relative to the total weight of the composition, preferably 10% by weight relative to the total weight of the composition.

[0045]

[0027] In particular embodiments of the present invention, said gas-phase flame retardant is selected from phosphine oxides, phosphonates, phosphinates, phosphites, phosphazenes and a mixture of two or more thereof. Preferably, said gas-phase flame retardant is selected from alkylphosphinates. Preferably, said gas-phase flame retardant is selected from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-melamine also known as dopo-melamine and an aluminum diethyl phosphinate.

[0046]

[0028] Throughout the present invention, said at least one inorganic compound is advantageously chosen from zeolites or zeolitic materials. Throughout the present invention, preferably said at least one inorganic compound is chosen from aluminosilicates, boron and aluminum phosphosilicates (BAPOS), Silicoaluminophosphates (SAPOS), Aluminophosphates (AIPOS), silicates, aluminas, magnesium oxides, zinc oxides. Throughout the present invention, even more preferably, said at least one inorganic compound is chosen from a zeolite chosen from aluminosilicates, boron and aluminum phosphosilicates (BAPOS), Silicoaluminophosphates (SAPOS) and Aluminophosphates (AIPOS).Throughout the present invention, particularly preferably, said at least one inorganic compound is a zeolite with a Si / Al ratio equal to or close to 1, such as zeolite 4A, zeolite 5A, zeolite Y and zeolite 13X. Zeolite 4A is a particularly preferred zeolite for the composition which is the subject of the present invention. The inorganic compound useful in the present invention may also be referred to as a “synergistic compound or agent”.

[0047]

[0029] It goes without saying that in the case where the intumescent agent used is a mixture of a piperazine pyrophosphate with melamine phosphate and zinc oxide, another source of zinc oxide as an inorganic compound can be used and this, in amounts so as to reach 0.5 to 5% by weight relative to the total weight of the composition.

[0048]

[0030] In a preferred embodiment of the present invention, the flame retardant material composition comprises or consists of:

[0049] - 30% to 60% by weight, for example 35% to 55% by weight of at least one polyolefin from a renewable or petro-sourced resource relative to the total weight of the composition,

[0050] - 5% to 20% by weight, for example 8% to 12% by weight of at least one fibrous material relative to the total weight of the composition,

[0051] - 20% to 50% by weight, for example 35% to 42% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition,

[0052] - 2.5% to 20% by weight, for example 7% to 15% by weight, of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0053] - 0.5 to 5%, for example 1% to 3% by weight of at least one inorganic compound of zeolite type chosen from aluminosilicates, bisacylphosphane oxides (BAPOS), Silicoaluminophosphates (SAPOS) and Aluminophosphates (AIPOS) relative to the total weight of the composition.

[0054]

[0031] For example, the flame retardant material composition comprises or consists of:

[0055] - 30% to 60% by weight, for example 35% to 55% by weight of at least one polyolefin from a renewable or petroleum-sourced resource,

[0056] - 5% to 20% by weight, for example 8% to 12% by weight of at least one fibrous material,

[0057] - 20% to 50% by weight, for example 35% to 42% by weight of at least one phosphate-based compound as an intumescent agent acting in the condensed phase, - 2.5% to 20% by weight, for example 7% to 15% by weight of at least one alkyphosphinate as a flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0058] - 0.5 to 5%, for example 1% to 3% by weight of at least one aluminosilicate zeolite,

[0059] The said % by weight being expressed in relation to the total weight of the composition.

[0060]

[0032] In a particularly preferred embodiment of the present invention, the flame retardant material composition comprises:

[0061] - 40% by weight of high density polyethylene relative to the total weight of the composition,

[0062] - 10% by weight of carbon fibers relative to the total weight of the composition,

[0063] - 38% by weight relative to the total weight of the composition of a mixture comprising between 45% and 65% of piperazine pyrophosphate relative to the total weight of said mixture, between 30% and 50% of melamine phosphate relative to the total weight of said mixture, and between 1% and 10% of zinc oxide relative to the total weight of said mixture,

[0064] - 10% by weight of aluminum diethyl phosphinate relative to the total weight of the composition,

[0065] - 2% by weight of a zeolite 4A or a zeolite Y, preferably a zeolite 4A, relative to the total weight of the composition.

[0066]

[0033] In particular embodiments of the present invention, the flame retardant material composition comprises at least one polymeric additive selected from stabilizers, antioxidants, colorants, pigments, mold release agents, plasticizers, treatment agents, antimicrobial agents, slip agents, antistatic agents, conductive additives, insulating additives, anti-drip agents, other flame retardants, and combinations of two or more thereof. Preferably, said at least one polymeric additive is present in the composition at a level of 0.1% to 10% by weight, preferably 0.1% to 5% by weight, relative to the total weight of the composition.

[0067]

[0034] According to a second aspect, the present invention relates to a 3D printing powder, a 3D printing granule or a 3D printing filament, comprising or consisting of the flame-retardant material composition which is the subject of the present invention.

[0035] According to a third aspect, the present invention relates to the use of a composition which is the subject of the present invention, a 3D printing powder, a 3D printing granule or a 3D printing filament which is the subject of the present invention, for 3D printing.

[0068]

[0036] According to a fourth aspect, the present invention relates to a part intended for the railway industry comprising or consisting of the flame-retardant material composition which is the subject of the present invention.

[0069]

[0037] According to a fifth aspect, the present invention relates to a means of rail transport comprising a part comprising or consisting of the flame-retardant material composition which is the subject of the present invention. Such a means of rail transport is, for example, a train.

[0070]

[0038] According to a sixth aspect, the present invention relates to a method for manufacturing a flame-retardant material comprising or strictly consisting of the composition which is the subject of the present invention, said method comprising the following steps of:

[0071] - heating said at least one polyolefin from a renewable or petroleum-sourced resource;

[0072] - adding to the heated polyolefin said at least one fibrous material, said at least one intumescent agent acting in the condensed phase, said at least one flame retardant agent acting in the gas phase and said at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these, so as to obtain the flame retardant material composition which is the subject of the present invention, the polyolefin being present in the composition at a level of 30% to 60% by weight, preferably 35 to 55% by weight, relative to the total weight of the composition, the fibrous material at 5% to 20% by weight, preferably 8 to 12% by weight, relative to the total weight of the composition, the intumescent agent acting in the condensed phase at 20% to 50% by weight, preferably from 35 to 42% by weight, relative to the total weight of the composition,the flame retardant agent acting in the gas phase from 2.5% to 20% by weight, preferably from 7 to 15% by weight, relative to the total weight of the composition and the inorganic compound from 0.5% to 5% by weight, preferably from 1 to 3% by weight, relative to the total weight of the composition;,

[0073] - mixing of the flame retardant material composition;

[0074] - cooling said composition so as to obtain the flame retardant material.

[0075]

[0039] In particular, the present invention relates to a method for manufacturing a flame-retardant material comprising or strictly consisting of the composition which is the subject of the present invention, said method comprising the following steps of:

[0076] - heating said at least one polyolefin from a renewable or petroleum-sourced resource;

[0077] - adding to the heated polyolefin said at least one fibrous material, said at least one intumescent agent acting in the condensed phase, said at least one flame retardant agent acting in the gas phase and said at least one inorganic compound chosen from aluminosilicates, boron and aluminum phosphosilicates (BAPOS), silicoaluminophosphates (SAPOS), aluminophosphates (AIPOS), silicates, aluminas, magnesium oxides and zinc oxides, preferably chosen from aluminosilicates, boron and aluminum phosphosilicates (BAPOS), silicoaluminophosphates (SAPOS), and aluminophosphates (AIPOS), so as to obtain the flame retardant material composition which is the subject of the present invention, the polyolefin being present in the composition at a level of 30% to 60% by weight, preferably 35 to 55% by weight, the fibrous material of 5% to 20% by weight, preferably 8 to 12% by weight,the intumescent agent acting in the condensed phase from 20% to 50% by weight, preferably from 35 to 42% by weight, the flame retardant agent acting in the gas phase from 2.5% to 20% by weight, preferably from 7 to 15% by weight, and the inorganic compound from 0.5% to 5% by weight, preferably from 1 to 3% by weight, the % by weight being expressed relative to the total weight of the composition;,

[0078] - mixing of the flame retardant material composition;

[0079] - cooling said composition so as to obtain the flame retardant material.

[0040] All the embodiments of the composition described above also apply of course to the method of manufacturing a flame retardant material which is the subject of the present invention.

[0041] Thus, for example, it goes without saying that when the intumescent agent used is a mixture of a piperazine pyrophosphate with melamine phosphate and zinc oxide, another source of zinc oxide as an inorganic compound can also be used and this in quantities so as to reach 0.5 to 5% by weight relative to the total weight of the composition.

[0080]

[0042] According to particular embodiments of the present invention, the method for manufacturing a flame-retardant material which is the subject of the present invention comprises an additional step of cutting the cooled composition into granules so as to obtain the flame-retardant material in the form of granules. Such an operation can be carried out for example in a granulator or a grinder, preferably in a granulator. In particular embodiments of the present invention, the step of heating said at least one polyolefin from a renewable or petro-sourced resource is carried out at a temperature of between 140°C and 200°C, preferably between 150°C and 190°C.

[0081]

[0043] In particular embodiments of the present invention, during the step of heating said polyolefin from a renewable or petro-sourced resource, said heating is carried out gradually. Preferably, the heating step is carried out in parallel with a mixing of the polyolefin, for example by shearing.

[0082]

[0044] In particular embodiments of the present invention, the step of cooling the composition is carried out at room temperature.

[0083]

[0045] In particular embodiments of the present invention, the steps of heating, adding to the heated polyolefin said at least one fibrous material, said at least one intumescent agent acting in the condensed phase, said at least one flame retardant agent acting in the gas phase and said inorganic compound, and mixing, are carried out with an extruder.

[0084]

[0046] A particularly preferred embodiment of the present invention consists in adding the polyolefin and the fibrous material to an extruder in a first step, then in a second step, for example in another zone of the extruder, separately or as a mixture, the other ingredients (i.e.: said at least one intumescent agent acting in the condensed phase, said at least one flame retardant agent acting in the gas phase and said at least one inorganic compound). According to this embodiment, the addition of the ingredients other than the polyolefin and the fibrous material can be done by means of a gravimetric or volumetric (preferably gravimetric) dosing device.

[0085]

[0047] According to a seventh aspect, the present invention relates to a method for preparing a three-dimensional shaped product by means of 3D printing, injection, thermoforming or thermocompression from the flame-retardant material composition which is the subject of the present invention.

[0086]

[0048] The present invention particularly relates to a method for preparing a three-dimensional shaped product by means of 3D printing, said method comprising the steps, preferably successive, of:

[0087] - provision of a flame retardant material composition which is the subject of the present invention;

[0088] - heating defined portions of the flame retardant material composition above the glass transition temperature of said composition;

[0089] - preparation of the three-dimensional shaped product from the heated flame retardant material composition;

[0090] - cooling the heated flame retardant material composition to obtain the solid three-dimensional shaped product.

[0091]

[0049] According to embodiments of the method for preparing a three-dimensional shaped product by means of 3D printing, the step of preparing the three-dimensional shaped product from the heated flame-retardant material composition involves depositing successive layers of the heated flame-retardant material composition on a support.

[0092]

[0050] According to embodiments of the method for preparing a three-dimensional shaped product by means of 3D printing, the step of heating the defined parts of the flame-retardant material composition is preferably carried out at a temperature of between 170°C and 270°C, between 180°C and 260°C, between 190°C and 250°C, between 200°C and 240°C, between 210°C and 230°C, between 215°C and 225°C, between 215°C and 220°C, preferably at 220°C.

[0093]

[0051] According to embodiments of the method for preparing a three-dimensional shaped product by means of 3D printing, the cooling step can be carried out at a temperature between room temperature which is approximately 20°C and 120°C, preferably between 20°C and 110°C, between 30°C and 90°C, between 40°C and 100°C, between 60°C and 100°C, between 70°C and 90°C or between 70 and 80°C. Preferably, the cooling step is carried out at room temperature which is approximately 20°C or at a temperature below room temperature.

[0094]

[0052] According to one embodiment of the method for preparing a three-dimensional shaped product by means of 3D printing, the flame retardant material composition is replaced by a 3D printing powder, a 3D printing granule or a 3D printing filament, comprising or consisting of the flame retardant material composition.

[0095] BRIEF DESCRIPTION OF THE FIGURES

[0096]

[0053] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the compositions and processes which are the subject of the present invention, with reference to the appended drawings, in which: Figure 1 is a schematic view of a twin-screw extruder (Haake Rheomex OS PTW16, Thermo Scientific (Waltham, Massachusetts, United States of America)) for implementing the method for manufacturing the flame-retardant material comprising the composition which is the subject of the present invention; Figure 2 groups together 4 images illustrating the study of lateral flame propagation according to the ISO 5658-2 test on a reduced scale for the flame-retardant material of composition according to the present invention.In a) the start of the test (fire start), in b) the development of the intumescent layer and propagation of the flame, in c) the gas phase action of the intumescent barrier (the flame retardant acting in the gas phase), and in d) the cessation of the flame propagation.

[0097] DETAILED DESCRIPTION OF THE INVENTION

[0098]

[0054] The present description is given as a non-limiting example of embodiment.

[0099]

[0055] As a reminder, the present invention relates to a flame-retardant material composition comprising:

[0100] - 30% to 60% by weight of at least one polyolefin from a renewable or petroleum-sourced resource relative to the total weight of the composition,

[0101] - 5% to 20% by weight of at least one fibrous material relative to the total weight of the composition, - 20% to 50% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition,

[0102] - 2.5% to 20% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition,

[0103] - 0.5% to 5% by weight of at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these relative to the total weight of the composition.

[0104]

[0056] Polyolefins from renewable or petro-sourced resources which can be used to produce the composition which is the subject of the present invention are, for example, polyethylenes (such as high-density polyethylenes (HDPE), low-density polyethylenes), polypropylene (PP) (homopolymer and copolymer).

[0105]

[0057] Fibrous materials that can be used to produce the composition that is the subject of the present invention are, for example, organic fibers (i.e. carbon fibers, aramid fibers, cellulose fibers, flax fibers, etc.), mineral fibers (i.e. glass fibers, ceramic fibers, basalt fibers).

[0106]

[0058] Intumescent agents acting in the condensed phase which can be used for producing the composition which is the subject of the present invention are, for example, phosphate-based compounds. Such phosphate-based compounds are, for example, chosen from a melamine phosphate (melamine pyrophosphate, melamine orthophosphate, melamine polyphosphate), triphenyl phosphate (TPP), resorcinol bis(diphenylphosphate) (RDP), diphenyl phosphate (BADP), tricresyl phosphate (TCP) and a mixture of a piperazine pyrophosphate with at least one additive chosen from a melamine phosphate (for example, melamine pyrophosphate, melamine orthophosphate, melamine polyphosphate), zinc oxide, a melamine-poly(zinc phosphate) and a melamine poly(aluminum phosphate).The product ADK STAB FP-2500S (ADK) marketed by the company ADEKA and comprising a piperazine pyrophosphate, a melamine phosphate and zinc oxide can in particular be used as said mixture in the composition which is the subject of the present invention.

[0107]

[0059] Flame retardants acting in the gas phase which can be used for producing the composition which is the subject of the present invention are, for example, organic phosphorus compounds such as phosphite oxides, phosphonates, phosphinates, phosphites, phosphazenes and a mixture thereof. Preferably, said flame retardant acting in the gas phase is chosen from alkylphosphinates. Preferably, said flame retardant acting in the gas phase is chosen from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-melamine (dopo-melamine) and an aluminum diethyl phosphinate (for example Exolit OP 1230 marketed by the company Clariant). Another example is dimethyl methyl phosphonate (DMMP).

[0108]

[0060] Inorganic compounds that can be used for producing the composition that is the subject of the present invention are preferably chosen from zeolites or zeolitic materials such as aluminosilicates, boron and aluminum phosphosilicates (BAPOS), silicoaluminophosphates (SAPOS), aluminophosphates (AIPOS). Preferably, said at least one inorganic compound is chosen from zeolitic materials or zeolites such as zeolites Y, zeolites 5A, zeolites 4A. Preferably, zeolite 4A is used as the inorganic compound of the composition that is the subject of the present invention.

[0109]

[0061] The present invention further relates to a method for manufacturing a flame-retardant material comprising or strictly consisting of the composition which is the subject of the present invention, said method comprising the following steps of:

[0110] - heating said at least one polyolefin from a renewable or petroleum-sourced resource;

[0111] - adding to the heated polyolefin said at least one fibrous material, said at least one intumescent agent acting in the condensed phase, said at least one flame retardant agent acting in the gas phase and said at least one inorganic compound, so as to obtain the flame retardant material composition which is the subject of the present invention, the polyolefin being present in the composition at a level of 30% to 60% by weight relative to the total weight of the composition, the fibrous material at a level of 5% to 20% by weight relative to the total weight of the composition, the intumescent agent acting in the condensed phase at a level of 20% to 50% by weight relative to the total weight of the composition, the flame retardant agent acting in the gas phase at a level of 2.5% to 20% by weight relative to the total weight of the composition and the inorganic compound at a level of 0.5% to 5% by weight relative to the total weight of the composition;

[0112] - mixing of the flame retardant material composition;

[0113] - cooling said composition so as to obtain the flame retardant material.

[0062] A. Example of a method for manufacturing a flame retardant material comprising a composition which is the subject of the present invention:

[0114]

[0063] A.1 Compounds

[0115]

[0064] A polyolefin, more particularly High Density Polyethylene (HDPE, SHA7260, Braskem (Sao Paulo, Brazil)) is used for the manufacture of the flame retardant material.

[0116]

[0065] A mixture of piperazine pyrophosphate with additives (melamine phosphate and zinc oxide) is used as an intumescent agent acting in the condensed phase (named ADK STAB FP-2500S, supplied by ADEKA, (Mulhouse, France)), Zeolite 4A is used as an aluminosilicate clay (produced by Alfa Aesar, fisher scientific, (lllkirch-graffenstaden, France)), carbon fiber is used as a fibrous material (distributed by R&G Faserverbundwerkstoffe GmbH (Bonholzstrasse, Waldenbuch)), and an aluminum diethyl phosphinate as a flame retardant agent acting in the gas phase (Exolit OP1230, supplied by Clariant, Muttenz, Switzerland). All the compounds of the developed flame retardant material composition, as well as their mass percentage and role are summarized in Table 2 below.

[0117] [Table 2]

[0118] Table 2: Composition of the flame retardant material

[0119]

[0066] This flame retardant material composition is the composition implemented by the inventors having the best results in fire / smoke performance tests.

[0067] A.2 Extrusion manufacturing process

[0120]

[0068] The manufacture of the flame retardant material was carried out with two different extruders.

[0121]

[0069] First, a twin-screw extruder (Haake Rheomex OS PTW16, Thermo Scientific (Waltham, Massachusetts, United States of America)), with a screw diameter of 16mm and a length to diameter ratio of 40 / 16 L / D, was used to formulate the flame retardant material. This extruder 100 consists of ten heating zones, set to the following temperature profile: Ti: 160°C - T2: 170°C - T3: 180°C - T4: 180°C - Ts: 175°C - Te: 170°C - T7: 175°C - Ts: 155°C - T9: 150°C - T10: 150°C, from a polyolefin polymer feed zone 101 to an outlet die 102 of the flame-retardant material (figure 1). The compounds other than the polymer are introduced at the zone which is at temperature T4, via a gravimetric doser 103. The speed of the extruder is 200 rpm.At the end of the extrusion, a rod 104 of flame-retardant polymer material is obtained and the latter is cooled in air to room temperature and then cut into granules 105 using a granulator or grinder 106 (Thermo Scientific (Waltham, Massachusetts, United States of America). The granules can then be used to produce a product 107 by 3D printing, thermocompression or injection, for example.

[0122]

[0070] In parallel, the same process was carried out by replacing the Haake Rheomex OS PTW16 extruder with another twin-screw extruder consisting of 12 heating zones, set according to the following profile: T1: 180°C - T2: 190°C - T3: 190°C - T4: 190°C - TS: 180 O C - T6: 190 O C - T7: 180 O C - T8: 180 OC - T9: 180°C - T : 190°C - T11: 190°C - T12: 190°C from a polyolefin polymer feed zone to a flame retardant material outlet die. The screw speed applied is 170 rpm and the imposed flow rate is 150 kg / h. The material obtained (rod) is then air cooled to room temperature and then cut into granules at room temperature.

[0123]

[0071] A.3 Formatting

[0124]

[0072] From the granules of the fire-retardant material, plates of standardized dimensions and depending on the fire scenarios considered, were produced by thermocompression using a Fontune press (Fontijne Grotnes BV, Niles, Michigan, United States) or injection (injection press supplied by the manufacturer AMPIA) or 3D printing (pellet additive manufacturing technique or "Pellet Additive Manufacturing" (PAM) in Anglo-Saxon terminology, with the Tool Changer printer supplied by E3D).

[0073] B. Study of the fire / smoke performance of the fire-retardant material

[0125]

[0074] The fire performance of the flame retardant material, described above, was evaluated on a small scale (laboratory) and large scale (certification body). The laboratory scale study implies that a reduction in the size of the tests was made such as for the lateral flame propagation test (ISO 5658-2). Indeed, this fire scenario requires the use of a test piece with a standardized surface area of ​​800*155 mm 2 . This size of test piece requires, among other things, a very large quantity of material. The inventors chose to work on a reduced scale in order to limit this consumption of raw materials. This ISO 5658-2 test consists of measuring the lateral propagation of a flame on the surface of a sample oriented in a vertical position. In the presence of a pilot flame, this sample is exposed to a radiant heat gradient ranging from 50 kW / m 2 at 0 kW / m 2. For the sample to be classified as HL2, the flame must stop at a Critical Extinction Energy Flux (CFE) greater than or equivalent to 20 kW / m 2 .

[0126]

[0075] Figure 2 illustrates the lateral flame propagation study according to the ISO 5658-2 test on a reduced scale for the flame retardant material of composition comprising 40% HDPE, 38% ADK, 10% carbon fiber, 10% OP1230 and 2% zeolite 4A by weight relative to the total weight of the composition. Part a) of Figure 2 represents the start of the test (fire start), in b) the development of the intumescent layer and flame propagation, in c) the gas phase action of the intumescent barrier (the flame retardant acting in the gas phase), and in d) the cessation of flame propagation.

[0127]

[0076] B.1 Sample 3 mm thick

[0128]

[0077] Table 3 below proves that the flame retardant material described above meets the HL2-R1 requirement of the EN 45545 standard for parts 3 mm thick. Indeed, the material formulation described above makes it possible to obtain a critical extinction flux (CFE) greater than 20 kW / m 2 , a maximum average heat emission rate (MAHRE) less than or equal to 90 kW / m 2 , as well as, when exposed to a radiative flux of 50 kW / m 2 , a cumulative value of the specific optical densities during the first 4 minutes of the test (VOF4) less than or equal to 600 min, an optical density of the test chamber at 4 min during the test multiplied by a factor which depends on the instrumentation and the size of the specimen (Ds(4)) less than or equal to 300, and a conventional toxicity index (ITCg) less than or equal to 0.9 and MAHRE respectively less than 0.9. [Table 3]

[0129] Table 3: Results obtained during small and large scale tests according to requirement HL2-R1 of standard EN 45545 for 3 mm thick parts.

[0130]

[0078] B.2 Sample 6 mm thick

[0131]

[0079] It is important to clarify that a material is HL2-R1 certified over a range of thicknesses. In other words, for a material to be usable over the 3 to 10 mm thickness range, a 10 mm test specimen must also pass all of the fire criteria described in Table 1. Consequently, these same tests were carried out for 6 mm thicknesses on small-scale pressed thermocom samples, and their results are shown in Table 4 below. It is emphasized that the developed flame retardant material also meets the HL2-R1 requirement. [Table 4]

[0132] Table 4: Results obtained during small-scale tests according to requirement HL2-R1 of standard EN 45545 for 6 mm thick parts.

[0133]

[0080] B.3 10 mm thick sample

[0081] Large-scale tests for 10 mm samples (injected specimens) were carried out and the results are shown in Table 5 below. Here too, it is shown that the developed flame retardant material also meets the HL2-R1 requirement.

[0134] [Table 5]

[0135]

[0136] Table 5: Results obtained during large-scale tests according to the HL2-R1 requirement of EN 45545 for 10 mm thick parts.

[0137]

[0082] B.4 Conclusion

[0083] A flame retardant material comprising by weight 40% of a polyolefin (HDPE), 10% of a fibrous material (carbon fiber), 38% of an intumescent agent acting in the condensed phase (ADK), 10% of a flame retardant agent acting in the gas phase (OP1230) and 2% of an inorganic compound (Zeolite 4A), relative to the total weight of the composition of said material, was developed and formulated by extrusion.

[0084] This flame retardant material has been shown to meet the HL2-R1 requirement of EN 45545 over a thickness range of 3 to 6 mm on a small scale for thermocompressed samples and over a thickness range of 3 to 10 mm on a large scale for injected samples. By extension, it is plausible that this material meets the HL2-R1 requirement for injected, thermocom pressed and 3D printed parts with thicknesses ranging from 3 to 10 mm.

[0138]

[0085] This flame retardant material composition can be used by all players in the railway industry since the EN 45545 standard is specific to this industrial sector. This European standard is more demanding than its American counterpart. The HL2-R1 requirement of EN 45545 concerns all interior surfaces of the train, horizontal / vertical (ceilings, walls, window frames, baggage storage areas and display screens) and the exterior surfaces of enclosures containing technical equipment. For example, it is possible to mention the baggage doors / storage area or the control panel within a train. This choice (HL2-R1) is motivated by the fact that there is a real railway need for this category of varied and very critical materials. Indeed, this normative requirement is one of the most important issues to date on the European railway market for small parts.In addition, meeting the HL2-R1 requirement (the strictest) advantageously allows meeting other less strict requirements such as HL2-R2, HL2-R3, HL2-R6, HL2-R22, HL2-R23, HL2-R24, .... Thus the material can be used in several categories of parts.

[0139]

[0086] C. Comparative tests

[0140]

[0087] Multiple formulations were developed (by extrusion) and tested according to different fire scenarios defined by the requirements of EN 45545 (Table 1). The strategy implemented consisted, as mentioned previously, of evaluating the flame retardant performances of the materials developed on a laboratory scale before their validation and certification on a large scale. This approach allowed rapid screening of formulations while saving material during development.

[0141]

[0088] Initially, the inventors identified the test that appeared to be the most critical among the three for meeting the HL2-R1 requirement. The objective is to search for at least three material formulations compatible with this first fire scenario before looking at the other tests. After analyzing the literature, very little research has been done on the lateral flame spread test (ISO 5658-2). Indeed, only the scientific article by M. Fôrsth et al., “Spectrally selective and adaptive surfaces for protection against radiative heating: ITO and VO 2”, Fire and Materials, vol. 38, p. 111-124, 2014, doi: 10.1002 / fam, and no other research has been done on this subject. This may testify to the severity of the performances that this fire scenario requires. For these reasons, the first tests began with this fire scenario.

[0142]

[0089] Plates with dimensions of 100*280 mm 2were shaped by thermocompression (method cited above in part A.3) and then tested in the ISO 5658-2 fire scenario on a reduced scale. In the absence of a flame retardant molecule, the polymer such as, for example, Polypropylene (PP), melts and burns. The flame spreads over the entire sample without stopping, thus giving a measured CFE equal to 0 kW / m 2 .

[0090] Table 6 below summarizes a number of tested and non-retained compositions (not compliant with HL2-R1 (NC)) and some flame retardant material compositions compliant with the HL2-R1 standard according to the present invention. The quantity of polyolefins is not mentioned in Table 6 but the latter are present in the different compositions in as large a proportion as necessary in order to achieve the required quantity of final product (qsp).

[0143] [Table 6]

[0144] Table 6: Tested compositions (VMT= Vermiculite, ZB= Zinc borate, 911C= Kemguard 911 C which is a Zinc molybdate / magnesium silicate complex, Coq= oyster shell particles, AP766= Ammonium Polyphosphate 766)

[0145]

[0091] C.1 Addition of an intumescent agent acting in the condensed phase

[0146]

[0092] Following this first test, various flame retardants were tested in different polyolefin matrices (polypropylene (PP), Polylactide Acid (PLA), High Density Polyethylene (HDPE)). Among the flame retardants tested are the following intumescent agents: commercial intumescent agents acting in the condensed phase such as piperazine pyrophosphate (ADK) or the product with the trade name FlameOff® (FO) marketed by the company FlameOff, chemical intumescent agents acting in the condensed phase (such as Ammonium PolyPhosphate (APP)), or physical intumescent agents acting in the condensed phase such as expanded graphite (EG). There are also ceramizing flame retardants acting in the condensed phase such as magnesium dihydroxide (MDH) (Table 6).

[0147]

[0093] In view of the large number of formulations tested (Table 6), only the results containing ADK (commercial intumescent agent acting in condensed phase) are presented in Table 7. As for Table 6, in Table 7 the quantity of polyolefins is not mentioned but the latter are present in the different compositions in proportions as large as necessary in order to reach the required quantity of final product (qsp).

[0148] [Table 7]

[0149]

[0150] Table 7: Compositions tested with commercial flame retardant ADK in the ISO 5658-2 test.

[0151]

[0094] Two rates, 30 and 40% by mass of ADK were studied. In both cases, it is noted that an insulating barrier called char forms on the surface and slows down the transfer of heat and mass. Tables 6 and 7 highlight that the action in the condensed phase of this flame retardant is not sufficient since the best CFE obtained does not exceed 9 kW / m 2 In addition, the tests observed the development of intumescence which, after a certain time, collapses and allows the flame to spread over the sample.

[0152]

[0095] Following this observation, a search for synergistic agents was undertaken, that is to say additives which cause interactions with the other elements of the system to produce an effect different from or greater than the sum of their individual effects. These will make it possible to reinforce the carbon residue (char) formed by the intumescence phenomenon.

[0153]

[0096] C.2 Addition of a synergistic agent: an inorganic compound

[0154]

[0097] The objective is to try to maintain the fire barrier created by the tank and thus prevent the flame from spreading on the sample to obtain a better CFE. To achieve this goal, inorganic compounds have been tested, including zeolitic materials such as zeolite 4A (Z4A). Zeolites can stabilize the material at high temperature by forming structures stabilizing the polymer. The latter can then participate in the formation of the intumescent barrier. In particular, a synergistic effect caused by zeolite Z4A in the intumescent system created by the ADK was observed since a CFE of 12.7 kW / m 2 is recorded at the end of the test. However, the latter always remains below 20 kW / m 2 expected. In addition, the reinforcement created by the zeolite is not sufficient since a collapse of the tank is always observed during the test.

[0155]

[0098] C.3 Addition of mechanical reinforcement: a fibrous material

[0156]

[0099] In order to ensure the maintenance of the fire barrier created by the tank during the test, a reinforcement composed of glass fibers (FV) was added within the PP polymer matrix. It is important to note that other types of fibers were tested such as carbon fibers (CF), basalt fibers (FB) or cellulose fibers (cellulose). The objective is to try to maintain the carbon barrier formed by the intumescence phenomenon by mechanically reinforcing it to ensure thermal protection throughout the test and thus limit the spread of the flame. Glass fibers were chosen for their insulating properties and their low cost. The presence of these fibers made it possible to increase the CFE by reaching a value of 14.8 kW / m 2 However, due to the vertical orientation of the sample, a collapse of the tank is still observed.

[0157]

[0100] C.4 Study of different ratios (intumescent agent / synergy agent) or nature of the aluminosilicate clay

[0158]

[0101] Still proceeding by iterative method and based on the information deduced from the previous tests with the glass fiber, different natures of zeolites (5A, Y, B) and an organomodified montmorillonite (Cloisite 20A =C20A) were tested to see their influence in terms of protection against fire. From the CFE results obtained and gathered in Table 7, it can be deduced that zeolite 5A does not allow any improvement in terms of protection against fire in a composition comprising a polyolefin (PP), glass fiber (FV), and ADK since a CFE of 8 kW / m 2 is measured. On the other hand, with C20A a more rigid char is formed and maintains its structure throughout the test (no collapse is observed). In addition, with zeolite Y (ZY) a very good CFE is measured (19.5 kW / m 2) closely approaching the expected result.

[0102] By these previous tests, it was highlighted that the nature of the zeolite strongly influences the flame propagation properties of a sample. Moreover, in view of the result very close to the desired objective (CFE above 20 kW / m 2), a modification of the intumescent agent (ADK) / synergizing agent (Zeolite Y) ratio was tested. Tables 6 and 7 summarize the various ratios tested. The best ratio obtained remains the one tested previously (38% / 2%). In addition, it is important to emphasize that the intumescent agent acting in the condensed phase / inorganic compound ratio strongly influences the flame propagation properties of the sample. Indeed, there is an optimal ratio to obtain a synergistic effect between ADK and zeolite, above or below this load, without other compounds in the composition the trend is reversed and antagonistic effects are observed. For example, for a ratio of 39:1, a CFE of 8.6 kW / m 2 is obtained, compared to the ratio 38:2 where a CFE 19.5 kW / m 2 was reached, hence the importance of correctly dosing the zeolite in the formulation.

[0159]

[0103] C.5 Addition of a flame retardant agent acting in the gas phase

[0160]

[0104] The combination of glass fibers (mechanical reinforcement), ADK (intumescent agent acting in condensed phase by forming a char) and zeolite (synergistic agent) makes it possible to considerably reduce the propagation of the flame. However, despite these promising results, the requirement of 20 kW / m 2imposed by the railway standard remains difficult to achieve. The previously added compounds only have an action in the condensed phase, optimizing the protective intumescent layer. To stop the flame propagation at average heat fluxes, the addition of a compound acting in the gas phase was tested. OP1230, an aluminum diethylphosphinate, was chosen because it acts in the gas phase by decomposing and releasing phosphorus free radicals capable of poisoning (inhibiting) the flame (reducing its exothermic effect and slowing down and inhibiting the flame's radical reactions). Thus, this gas phase flame retardant was incorporated into the best formulations tested (Tables 6 and 7), and it is noted that the combination of gas and condensed phase action makes it possible to slow down and stop the flame propagation on the sample. Indeed, better CFEs are measured, ranging from 23 to 20 kW / m respectively 2for formulations composed of PP+10%FV+38%ADK+10%OP1230+2%ZY and PP+10%FV+38%ADK+10%OP1230+2%Z4A, with systematic maintenance of the protective layer.

[0161]

[0105] C.6 Combination of chemical and physical intumescence

[0162]

[0106] The combination of a physical intumescent agent acting in the condensed phase (provided by expanded graphite (EG)) with a chemical intumescent agent (ADK) has been considered. Indeed, EG has an intumescent behavior due to the physical expansion and formation of graphite worms, caused by the sublimation of the insertion compounds trapped between the graphite layers. An entangled network is thus formed and ensures the formation of a protective barrier. Table 7 highlights that the combination of physical and chemical intumescence makes it possible to slow down and stop the flame propagation. CFEs ranging from 21 to 28 kW / m 2are thus respectively obtained for the formulations P P+ 10% FV+38% AD K+ 10% OP 1230+2% C20A+ 10% EG and

[0163] P P+ 10% FV+38% AD K+ 10% OP 1230+2%ZY+ 10% EG.

[0164]

[0107] C.7 Conclusion

[0165]

[0108] To conclude, at the end of these tests three compositions having a CFE greater than 20 kW / m 2 were retained: PP+10%FV+38%ADK+1 0%OP1 230+2%ZY,

[0166] P P+ 10% FV+38% AD K+ 10% OP 1230+2%ZY+ 10% EG, PP+10%FV+38%ADK+1 0%OP1 230+2%Z4A.

[0167]

[0109] The tests were extended to compositions comprising high-density polyethylene (HDPE) instead of polypropylene (PP). The next fourth composition having a CFE greater than 20 kW / m 2 was retained:

[0168] HDPE+10%FC+38%ADK+1 0%OP1 230+2%Z4A.

[0169]

[0110] The compositions retained at the end of this phase were tested using a cone calorimeter (ISO 5660-1) and smoke production test (ISO 5659-2).

[0170]

[0111] The cone calorimeter test (ISO 5660-1) makes it possible to evaluate the reaction to fire of materials and in particular to measure the rate of heat released over time by the sample (surface 100*100 mm 2 ) exposed to a radiative heat flux equivalent to 50 kW / m 2 The maximum average heat emission rate (MARHE) is then calculated and must be less than 90 kW / m 2 so that the sample can be classified HL2-R1 in this test.

[0171]

[0112] The objective of the smoke production test (ISO 5659-2) is to ensure that the selected material compositions have a sufficiently low smoke opacity and toxicity to ensure that in the event of a fire the evacuation of people is safe. This test, which is essential for classification to EN45545 HL2-R1, consists of exposing the surface of a sample (75*75mm 2 ) positioned horizontally, at a radiant heat of 50kW / m 2within a closed enclosure, without pilot flame ignition. The optical density value is measured over a given time using an opacimeter. This measurement provides access to the cumulative value of the specific optical densities during the first 4 minutes (VOF4) and to the optical density in the test chamber at 4 min multiplied by a factor that depends on the instrumentation and the size of the specimen (Ds(4)). In parallel, the analysis of the gases resulting from the degradation of the tested sample is analyzed by Fourier Transform Infrared Spectroscopy (FTIR). The concentration of each toxic gas (Carbon Monoxide (CO), Carbon Dioxide (CO2), Hydrogen Bromide (HBr), Hydrochloric Acid (HCl), Hydrogen Cyanide (HCN), Hydrofluoric Acid (HF), Sulphur Dioxide (SO2), Nitrogen Oxides (NOx)) is recorded and compared to a relevant reference in order to determine the value of the conventional toxicity index (ITCg).

[0172]

[0113] The results are illustrated in Table 7 and show compatibility with the HL2-R1 standard for the three compositions. In addition, the modification of the PP polymer matrix substituted by HDPE and the reinforcement (glass fibers replaced by carbon fibers) made it possible to obtain the fourth composition whose results are also in accordance with the HL2-R1 requirement of EN 45545 (Table 7).

Claims

Claims 1. Flame-retardant material composition usable for 3D printing, characterized in that it comprises or is strictly composed of: - 30% to 60% by weight of at least one polyolefin from a renewable or petroleum-sourced resource relative to the total weight of the composition, - 5% to 20% by weight of at least one fibrous material relative to the total weight of the composition, - 20% to 50% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition, - 2.5% to 20% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition, - 0.5% to 5% by weight of at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these, relative to the total weight of the composition.

2. Composition according to claim 1, comprising: - 40% by weight of at least one polyolefin from a renewable or petroleum-sourced resource relative to the total weight of the composition, - 10% by weight of at least one fibrous material relative to the total weight of the composition, - 38% by weight of at least one intumescent agent acting in the condensed phase relative to the total weight of the composition, - 10% by weight of at least one flame retardant agent acting in the gas phase relative to the total weight of the composition, - 2% by weight of at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, zinc oxides and a mixture of two or more of these, relative to the total weight of the composition.

3. Composition according to any one of claims 1 or 2, in which said polyolefin from a renewable or petroleum-sourced resource is a high-density polyethylene.

4. Composition according to any one of claims 1 to 3, wherein said fibrous material is selected from glass fiber, aramid fiber, basalt fiber, cellulose fiber, flax fiber and carbon fiber.

5. A composition according to any one of claims 1 to 4, wherein said condensed phase intumescent agent is a phosphate-based compound.

6. Composition according to claim 5, wherein said intumescent agent acting in the condensed phase is selected from a melamine phosphate and a mixture of a piperazine pyrophosphate with at least one additive selected from a melamine phosphate, zinc oxide, a melamine-poly(zinc phosphate) and a melamine poly(aluminum phosphate).

7. Composition according to any one of claims 1 to 6, wherein said flame retardant acting in the gas phase is chosen from phosphite oxides, phosphonates, phosphinates, phosphites, phosphazenes and a mixture of two or more of these, preferably from alkylphosphinates.

8. The composition of claim 7, wherein said gas phase flame retardant is selected from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-melamine and aluminum diethyl phosphinate.

9. Composition according to any one of claims 1 to 8, in which said inorganic compound is a zeolite chosen from aluminosilicates, boron and aluminum phosphosilicates (BAPOS), Silicoaluminophosphates (SAPOS), Aluminophosphates (AIPOS), preferably is a zeolite with a Silicon / Aluminum (Si / AI) ratio equal to or close to 1, even more preferably is a zeolite 4A or a zeolite Y.

10. Composition according to any one of claims 1 to 9, comprising: - 40% by weight of high density polyethylene relative to the total weight of the composition, - 10% by weight of carbon fibers relative to the total weight of the composition, - 38% by weight relative to the total weight of the composition of a mixture comprising between 45% and 65% of piperazine pyrophosphate relative to the total weight of said mixture, between 30% and 50% of melamine phosphate relative to the total weight of said mixture, and between 1% and 10% of zinc oxide relative to the total weight of said mixture, - 10% by weight of aluminum diethyl phosphinate relative to the total weight of the composition, - 2% by weight of a zeolite 4A or a zeolite Y, relative to the total weight of the composition.

11. 3D printing powder, 3D printing granule or 3D printing filament, comprising or strictly consisting of the flame retardant material composition according to any one of claims 1 to 10.

12. Part intended for the railway industry comprising or being strictly made up of the composition according to any one of claims 1 to 10.

13. Rail transport means comprising a part according to claim 12.

14. Method for manufacturing a flame retardant material comprising or strictly consisting of the composition according to any one of claims 1 to 10, said method comprising the following steps of: - heating of at least one polyolefin from a renewable or petroleum-sourced resource; - addition to the heated polyolefin of at least one fibrous material, at least one intumescent agent acting in the condensed phase, at least one flame retardant agent acting in the gas phase and at least one inorganic compound chosen from zeolites or zeolitic materials, montmorillonites, vermiculites, silicates, aluminas, magnesium oxides, oxides of zinc and a mixture of two or more thereof, relative to the total weight of the composition, so as to obtain a composition of flame retardant material, the polyolefin being present in the composition at a level of 30% to 60% by weight relative to the total weight of the composition, the fibrous material at a level of 5% to 20% by weight relative to the total weight of the composition, the intumescent agent acting in the condensed phase at a level of 20% to 50% by weight relative to the total weight of the composition, the flame retardant agent acting in the gas phase at a level of 2.5% to 20% by weight relative to the total weight of the composition and the inorganic compound at a level of 0.5% to 5% by weight relative to the total weight of the composition; - mixing of the flame retardant material composition; - cooling said composition so as to obtain the flame retardant material.

15. A method of preparing a three-dimensional shaped product by means of 3D printing, injection, thermoforming or thermocompression from the flame retardant material composition according to any one of claims 1 to 10.

16. Method for preparing a three-dimensional shaped product by means of 3D printing according to claim 15, said method comprising the steps, preferably successive, of: - providing a flame retardant material composition according to any one of claims 1 to 10; - heating defined portions of the flame retardant material composition above the glass transition temperature of said composition; - preparation of the three-dimensional shaped product from the heated flame retardant material composition; - cooling the heated flame retardant material composition to obtain the solid three-dimensional shaped product.

Images