Ductile flame retardant polyamide composition and its use, particularly for trains

Abstract

The present invention comprises, by weight: (a) 30% to 85% by weight, for example 33% to 83% by weight, in particular 50% to 78.9% by weight, of at least one semicrystalline aliphatic polyamide having an intrinsic viscosity in the range of 1.2 to 1.6, in particular in the range of 1.2 to 1.5, in particular in the range of 1.3 to 1.5, in particular strictly below 1.5, in particular in the range of 1.30 to 1.48, measured in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid at a temperature of 20° C. and at a concentration of 0.5%, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt% of at least one phosphinate-based flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8%, in particular 2% to 6%, of at least one plasticizer; (e) 0 to 10%, in particular 0.1% to 5%, of at least one additive; The present invention relates to a flame retardant composition comprising:

Description

[Technical field]

[0001] The present invention relates to a ductile flame retardant polyamide composition and its use, particularly in railroad applications, and for the manufacture of tubes, particularly corrugated tubes. [Background technology]

[0002] In the train sector there is a tendency to use materials with high mechanical strength and good resistance to ageing.

[0003] Nowadays, materials used in trains have to meet technical requirements regarding fire resistance. These requirements vary depending on the type of object and its use inside the train. The EN 45545 standard lays down various specifications depending on the material category. Polyamide tubes fall into the R22 and R23 categories.

[0004] Products are classified according to their limiting oxygen index and the density and toxicity of the smoke produced when burned. Depending on their fire resistance properties, three classes are available: HL1, HL2 and HL3.

[0005] The higher the grade, the more likely the product can be used on large trains, but products classified as HL1 cannot be used on subway trains, for example.

[0006] Currently, the HL2 category covers the majority of the existing market and is the commonly targeted subject, specifically meaning a Limit Oxygen Index (LOI) above 28.

[0007] Apart from this fire resistance, the materials used in trains are also subjected to a number of mechanical stresses, including the following properties: - Flexibility: The elastic modulus must be between 500 and 1200 MPa. - Flexibility / bendability: Ability to deform a tube without cracking (low stress and high elongation), related to the behavior at yield point. - Breaking strength: The tensile elongation at break must exceed 100%. - Impact strength at temperatures ranging down to -30°C. - Fatigue strength.

[0008] These properties must be maintained over time, so the product must be able to withstand accelerated heat aging at 150°C for several days.

[0009] Finally, the polyamide must remain easy to process by extrusion, which may limit the viscosity of the formulation.

[0010] In the prior art, flame-retardant formulations have already been described, such as in the application US patent application 20170037198, which describes formulations for the railway sector with a particular focus on PA12 matrices.

[0011] However, these compounds do not meet all the requirements mentioned above, especially with regard to the mechanical properties.

[0012] In the railway sector, WO 2013 / 092302 deals with glass fibre reinforced polyamides that are flame retarded with melamine derivatives.

[0013] Finally, application US Patent Application No. 2007 / 0021535 uses a combination of phosphinate, melamine cyanurate, and polyols as flame retardants for polyamides.

[0014] However, the same drawbacks associated with the above requirements remain, particularly with regard to the mechanical properties.

[0015] Therefore, new products need to be developed that provide adequate protection for equipment and passengers in the event of a fire.

[0016] There is therefore a need for a more perfect formulation that provides a compromise, particularly an optimal compromise, between mechanical strength and fire resistance.

[0017] The present invention therefore provides a composition comprising, by weight: (a) 30% to 85% by weight, for example 33% to 83% by weight, in particular 50% to 78.9% of at least one semicrystalline aliphatic polyamide having an intrinsic viscosity in the range of 1.2 to 1.6, in particular in the range of 1.2 to 1.5, in particular in the range of 1.3 to 1.5, in particular strictly below 1.5, in particular in the range of 1.30 to 1.48, measured in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid at a temperature of 20° C. and at a concentration of 0.5%, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt% of at least one phosphinate-based flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; The present invention relates to a flame retardant composition comprising:

[0018] Thus, the inventors have discovered that a semi-crystalline aliphatic polyamide having a particular intrinsic viscosity in specific proportions can be combined with at least a phosphinate flame retardant, a functionalized polyolefin, and a plasticizer, all three of which are present in specific proportions, and optionally further combined with additives, to form a composition that meets all of the above requirements.

[0019] The viscosity of the semicrystalline aliphatic polyamide matrix is ​​particularly important for the fatigue strength. If the intrinsic viscosity is too low, i.e. below 1.2, the fatigue strength is not sufficient. Thus, compositions based on semicrystalline aliphatic polyamides with a viscosity below 1.2 will have insufficient mechanical properties for the intended application, in particular as tubes, especially corrugated tubes, for railway applications. Compositions based on semicrystalline aliphatic polyamides with a viscosity below 1.2 will have particularly insufficient fatigue strength. The fatigue strength can be measured by the Lossflex test, as explained in the examples. The compositions according to the invention, i.e. in particular those comprising semicrystalline aliphatic polyamides with a viscosity above 1.2, advantageously fulfill this test, i.e. make it possible to prepare bars that do not break after 400,000 cycles, according to the Lossflex test described in the examples.

[0020] If the viscosity is too high, especially above 1.6, the composition cannot be molded, especially into the shape of a corrugated tube.

[0021] Compositions based on semi-crystalline aliphatic polyamides with viscosities significantly above 1.6 could not be extruded, in particular at standard molding temperatures, in particular at temperatures below 350°C, preferably below 320°C, preferably between 170°C and 300°C, for example between 200°C and 280°C.

[0022] Such compositions must be extruded at significantly higher temperatures and / or at higher shear rates, with the effect of in particular affecting the fire resistance of the resulting tubes, the flame retardants being at least partially or completely degraded under such processing conditions. These compositions therefore have insufficient fire resistance for their intended use, in particular as tubes, in particular corrugated tubes, for railway applications. Compositions based on semicrystalline aliphatic polyamides, in particular with a high viscosity, in particular above 1.6, will in particular have a limiting oxygen index (LOI) lower than the values ​​required to meet categories R22 and R23 of standard EN 45545. Compositions according to the invention, i.e. compositions comprising semicrystalline aliphatic polyamides, in particular with a viscosity of less than 1.6, preferably less than 1.5, preferably strictly less than 1.5, are advantageously able to meet this test, as shown in the examples.

[0023] The range of plasticizers allows the composition to have a sufficiently low modulus without compromising cold impact strength.

[0024] Thus, compositions comprising less than 2% plasticizer relative to the total weight of the composition may have insufficient mechanical properties for the intended application, in particular as a tube for railway applications, in particular as a corrugated tube. Compositions comprising less than 2% plasticizer relative to the total weight of the composition may in particular have an excessively high tensile modulus, in particular a tensile modulus of more than 1200 MPa, this parameter being measured as explained in the examples. The compositions according to the invention, i.e. in particular a composition comprising at least 2% by weight plasticizer relative to the total weight of the composition, advantageously make it possible to achieve satisfactory mechanical properties, in particular a tensile modulus of less than 1200 MPa, this parameter being measured as explained in the examples.

[0025] Compositions containing more than 8% plasticizer by weight relative to the total weight of the composition may have insufficient mechanical properties for the intended use, in particular as tubes, especially corrugated tubes, for railway applications. Compositions containing more than 8% plasticizer by weight relative to the total weight of the composition may have insufficient mechanical properties for the intended use, in particular as tubes, especially corrugated tubes, for railway applications. 2The compositions according to the invention, i.e. in particular those containing up to 8% by weight of plasticizer relative to the total weight of the composition, may have satisfactory mechanical properties, in particular a cold notch impact strength of less than 5 kJ / m 2 A cold notch impact strength of 0.1 to 0.2 mm can be achieved, this parameter being measured as described in the examples.

[0026] The range of functionalized polyolefins makes it possible to obtain good fatigue strength and / or good cold impact strength without excessively increasing the fire resistance of the composition.

[0027] Thus, compositions with less than 5% by weight of functionalized polyolefin relative to the total weight of the composition will have insufficient mechanical properties for their intended use, in particular as tubes, especially corrugated tubes, for railway applications. Compositions with less than 5% by weight of functionalized polyolefin relative to the total weight of the composition will in particular have mechanical properties that are insufficient for their intended use, in particular as tubes, especially corrugated tubes, for railway applications. 2 The compositions according to the invention, i.e. in particular those comprising at least 5% by weight of functionalized polyolefin relative to the total weight of the composition, have satisfactory mechanical properties, in particular a cold notch impact strength of less than 5 kJ / m 2 A cold notch impact strength of 0.1 to 0.2 mm can be achieved, this parameter being measured as described in the examples.

[0028] Moreover, compositions with more than 20% by weight of functionalized polyolefin relative to the total weight of the composition have insufficient fire resistance for the intended application, in particular as a tube, in particular as a corrugated tube, for railway applications. Compositions with more than 20% by weight of functionalized polyolefin relative to the total weight of the composition will have a lower than desired limiting oxygen index (LOI), in particular to meet the standard EN 45545 categories R22 and R23. The compositions according to the invention, i.e. compositions with functionalized polyolefins in a content of less than 20% by weight relative to the total weight of the composition, advantageously make it possible to meet this test, as shown in the examples. The flame retardant range defined according to the invention itself makes it possible to obtain sufficient fire resistance, in particular to obtain compositions with a limiting oxygen index (LOI) greater than the desired value, in particular to meet the categories R22 and R23 of EN 45545, without excessively weakening the product and while maintaining satisfactory mechanical properties. Compositions containing less than 10% of flame retardants relative to the total weight of the composition are generally unable to achieve the values ​​required to fulfil the standard EN 45545 for categories R22 and R23, as defined in the examples. Compositions containing more than 30% of flame retardants relative to the total weight of the composition tend to show insufficient mechanical properties, in particular a flame retardancy of 5 kJ / m 2 The compositions according to the invention, i.e. compositions comprising in particular a maximum of 30% by weight, preferably not more than 25% by weight, in particular not more than 22% by weight, of flame retardant relative to the total weight of the composition, may have satisfactory mechanical properties, in particular a cold notch impact strength of less than 5 kJ / m 2 A cold notch impact strength of 0.1 to 0.2 mm can be achieved, this parameter being measured as described in the examples.

[0029] It is therefore a compromise, particularly an optimum, which can only be achieved by specially selecting the ranges of the various components of the composition.

[0030] Advantageously, said composition is intended for railways.

[0031] The invention also encompasses the use of the compositions defined according to the invention for the manufacture of flame retardant articles, in particular tubes, intended for railway applications, in particular for use in trains.

[0032] Semicrystalline aliphatic polyamide (a) The composition of the invention comprises at least one semicrystalline aliphatic polyamide having an intrinsic viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, measured according to standard ISO 307:2007 at a temperature of 20° C. and a concentration of 0.5% by weight, using m-cresol instead of sulfuric acid.

[0033] According to one embodiment, the composition of the invention comprises at least one semicrystalline aliphatic polyamide having an intrinsic viscosity strictly below 1.5, in particular ranging from 1.30 to 1.48, measured according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and at a concentration of 0.5% by weight.

[0034] The at least one semicrystalline aliphatic polyamide (a) is present in a content ranging from 30% to 85% by weight, in particular from 33% to 83% by weight and in particular from 50% to 78.9% by weight, relative to the total weight of the composition.

[0035] Semicrystalline polyamide is understood to mean a material which is generally solid at room temperature, which softens during increasing temperature, in particular after exceeding the glass transition temperature (Tg), which melts rapidly above the so-called melting point (Tm) and which becomes solid again when the temperature falls below the crystallization temperature.

[0036] Tg, Tc, Tm are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013, respectively.

[0037] The number average molecular weight Mn of the semicrystalline polyamide is preferably in the range of 10,000 to 85,000, particularly 10,000 to 60,000, preferably 10,000 to 50,000, and further preferably 12,000 to 50,000.

[0038] The nomenclature used to define polyamides is described in standard ISO 1874-1:2011 “Plastics - Polyamide (PA) moulding and extrusion materials - Part 1: Designation”, in particular page 3 (Tables 1 and 2), and is well known to the person skilled in the art.

[0039] The term polyamide includes both homopolyamides and copolyamides.

[0040] The at least one semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam, or from the polycondensation of at least one amino acid, or from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y, or from mixtures thereof.

[0041] When the at least one semi-crystalline aliphatic polyamide results from the polycondensation of at least one lactam, the at least one lactam may be selected from C6 to C18, preferably C9 to C18, more preferably C10 to C18 and even more preferably C10 to C11 lactams. The C8 to C18 lactam is in particular decanolactam or undecanolactam.

[0042] When said at least one semi-crystalline aliphatic polyamide results from the polycondensation of at least one lactam, it may comprise a single lactam or several lactams.

[0043] When said at least one semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one amino acid, said at least one amino acid may be selected from C6 to C18, preferably C9 to C18, more preferably C10 to C18, and even more preferably C10 to C11 amino acids.

[0044] C6-C18 amino acids are in particular 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid and derivatives thereof, in particular N-heptyl-11-aminoundecanoic acid.

[0045] When said at least one semi-crystalline aliphatic polyamide results from the polycondensation of at least one amino acid, it may comprise a single amino acid or several amino acids.

[0046] Advantageously, said semicrystalline aliphatic polyamide results from the polycondensation of a single amino acid, said amino acid being chosen from 10-aminodecanoic acid and 11-aminoundecanoic acid, advantageously 11-aminoundecanoic acid.

[0047] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine X from C4 to C36, preferably from C6 to C18, preferably from C6 to C12, more preferably from C10 to C12, with at least one diacid Y from C4 to C36, preferably from C6 to C18, preferably from C6 to C12, more preferably from C10 to C12, said at least one diamine X is an aliphatic diamine and said at least one diacid Y is an aliphatic diacid.

[0048] The diamines may be linear or branched, and are preferably linear.

[0049] The at least one C4 to C36 diamine X may be chosen in particular from 1,4-butanediamine, 1,5-pentanediamine, 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 derived from fatty acids.

[0050] Advantageously, said at least one diamine X is C6 to C18 and is chosen 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.

[0051] Advantageously, said at least one C6 to C12 diamine X is chosen in particular from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine and 1,12-dodecamethylenediamine.

[0052] Advantageously, the diamine X used is a C10-C12 diamine, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine and 1,12-dodecamethylenediamine.

[0053] The at least one C4-C36 dicarboxylic acid Y can 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, and diacids derived from fatty acids.

[0054] The diacids may be linear or branched, and are preferably linear.

[0055] Advantageously, said at least one dicarboxylic acid Y is a C6 to C18 dicarboxylic acid and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid and octadecanedioic acid.

[0056] Advantageously, said at least one dicarboxylic acid Y is a C6 to C12 dicarboxylic acid and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid and dodecanedioic acid.

[0057] Advantageously, said at least one dicarboxylic acid Y is a C10-C12 dicarboxylic acid and is chosen from sebacic acid, undecanedioic acid and dodecanedioic acid.

[0058] When said semi-crystalline aliphatic polyamide results from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y, it may comprise a single diamine or multiple diamines and a single dicarboxylic acid or multiple dicarboxylic acids.

[0059] Advantageously, said semi-crystalline aliphatic polyamide results from the polycondensation of a single diamine X with a single dicarboxylic acid Y.

[0060] In one embodiment, said at least one polyamide is a long chain polyamide having 8 or more carbon atoms per nitrogen atom, in particular 9 or more carbon atoms, more particularly 10 or more carbon atoms.

[0061] In another embodiment, the at least one semi-crystalline aliphatic polyamide is selected from polyamides PA610, PA612, PA1010, PA1012 and PA11.

[0062] Advantageously, said at least one semicrystalline aliphatic polyamide is chosen from the polyamides PA1010, PA1012 and PA11, in particular PA11.

[0063] According to one embodiment, the semi-crystalline aliphatic polyamide of the present invention may be a polyether block amide (PEBA).

[0064] Polyether block amide (PEBA) is a copolymer comprising amide units (Ba1) and polyether units (Ba2), the amide units (Ba1) being units derived from at least one amino acid, at least one lactam, or at least one diamine, said diamine being chosen from linear or branched aliphatic diamines, and at least one dicarboxylic acid, said diacid being an aliphatic diacid, XY corresponds to an aliphatic repeat unit selected from units X and Y obtained by polycondensation of Said polyether units (Ba2) are derived in particular from at least one polyalkylene ether polyol, in particular a polyalkylene ether diol.

[0065] According to one embodiment, the semi-crystalline aliphatic polyamide of the present invention is not a polyether block amide (PEBA).

[0066] According to one embodiment, the semi-crystalline aliphatic polyamide according to the invention is not PA12.

[0067] Phosphinic acid flame retardants (b) The composition according to the invention must contain a sufficient amount of phosphinate flame retardant (b) to give the composition the desired fire resistance properties, in particular a HL2 or HL3 hazard level classification according to standard EN 45545, preferably a HL2 hazard level classification according to standard EN 45545.

[0068] The at least one phosphinate-based flame retardant (b) may be present in a content of at least 10% by weight, such as at least 14% by weight, for example at least 15% by weight, for example at least 17% by weight, relative to the total weight of the composition.

[0069] If the amount of phosphinate flame retardant (b) is too low, sufficient fire resistance is not obtained, in particular a HL2 or HL3 hazard level classification according to standard EN 45545, in particular a HL2 hazard level classification according to standard EN 45545 cannot be achieved.

[0070] The phosphinate flame retardant (b) must also not be present in excessive amounts, as this would adversely affect the mechanical properties, and is therefore usually present in a content of up to 40% by weight, typically up to 30% by weight, relative to the total weight of the composition.

[0071] Too high an amount of phosphinate flame retardant (b) may adversely affect the mechanical properties, in particular the tensile strength and / or impact strength and / or fatigue strength may be reduced.

[0072] According to one embodiment, the phosphinate flame retardant (b) is present in a content ranging from 10% to 30% by weight, such as from 10% to 25% by weight, such as from 14% to 25% by weight, such as from 14% to 22% by weight, such as from 17% to 22% by weight, relative to the total weight of the composition. For example, the at least one phosphinate flame retardant (b) may be present in a content ranging from 14% to 20% by weight, relative to the total weight of the composition.

[0073] The flame retardant is in particular a metal salt chosen from metal salts of phosphinic acids, metal salts of diphosphinic acids, polymers comprising at least one metal salt of phosphinic acids or polymers comprising at least one metal salt of diphosphinic acids. The flame retardant may also be a mixture of the abovementioned flame retardants.

[0074] The flame retardant may also be selected from metal salts of phosphinic acids of formula (I) below and metal salts of diphosphinic acids of formula (II) below. TIFF2025514944000001.tif40170TIFF2025514944000002.tif40170In the formula, R1 and R2 each independently represent a linear or branched C1 to C6 alkyl group or an aryl group; R3 represents a linear or branched C1 to C10 alkylene, C6 to C10 arylene, C6 to C10 alkylarylene, or C6 to C10 arylalkylene group; M is Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na or K ions and / or protonated amine bases; m represents an integer of 1 to 4; n represents an integer of 1 to 4; x represents an integer of 1 to 4; n and m are selected so that the salt is neutral, ie, uncharged.

[0075] Preferably, M represents a calcium, magnesium, aluminium or zinc ion.

[0076] Preferably, R1 and R2 independently of one another represent a methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl and / or phenyl group.

[0077] Preferably, R3 represents a methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene, phenylene, naphthylene, methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene, tert-butylnaphthylene, phenylmethylene, phenylethylene, phenylpropylene or phenylbutylene group.

[0078] According to one embodiment, the flame retardant may be aluminum diethylphosphinate. As an example of such a compound, mention may be made in particular of the product Exolit OP1311 sold by Clariant.

[0079] Regarding functionalized polyolefins (c) The compositions according to the invention must contain a sufficient amount of functionalized polyolefin to impart to the composition the mechanical properties desired for the intended use, particularly good fatigue strength.

[0080] Said at least one functionalized polyolefin (c) is present in an amount ranging from 5% to 20% by weight, in particular from 5% to 15% by weight, relative to the total weight of the composition.

[0081] Functionalized polyolefins can be polymers of alpha-olefins bearing reactive units (functional groups), such as acid, anhydride or epoxy functional groups. Examples include non-functionalized polyolefins grafted or copolymerized or terpolymerized with unsaturated epoxides, such as glycidyl (meth)acrylate, or carboxylic acids or their salts or esters, such as (meth)acrylic acid, the latter of which can be fully or partially neutralized with metals, such as Zn, or carboxylic anhydrides, such as maleic anhydride.

[0082] Non-functionalized polyolefins are typically homopolymers or copolymers of alpha-olefins or diolefins such as ethylene, propylene, 1-butene, 1-octene, butadiene, etc. Examples include: - polyethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene), metallocene polyethylene, propylene homopolymers or copolymers, -Ethylene / alpha olefins such as ethylene / propylene, EPR (short for ethylene propylene rubber), and ethylene propylene diene (EPDM) copolymers; -Styrene / Ethylene Butene / Styrene (SEBS), Styrene / Butadiene / Styrene (SBS), Styrene / Isoprene / Styrene (SIS), Styrene / Ethylene Propylene / Styrene (SEPS) block copolymers, - Copolymers of ethylene and at least one product chosen from salts or esters of unsaturated carboxylic acids, such as alkyl (meth)acrylates (for example methyl acrylate), or vinyl esters of saturated carboxylic acids, such as vinyl acetate (EVA), the proportion of comonomers being possible up to 40% by weight.

[0083] The functionalized polyolefin is, for example, a PE / EPR blend, the weight ratio of which can vary within a wide range, for example between 40 / 60 and 90 / 10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, the degree of grafting being, for example, from 0.01 to 5% by weight.

[0084] The functionalized polyolefins can be chosen from the following (co)polymers grafted with maleic anhydride or with glycidyl methacrylate, the degree of grafting being, for example, between 0.01% and 5% by weight: PE, PP, copolymers of ethylene with propylene, butene, hexene or octene (for example with an ethylene content of 35% to 80% by weight), -Ethylene / alpha olefins such as ethylene / propylene, EPR (short for ethylene propylene rubber), and ethylene propylene diene (EPDM) copolymers; -Styrene / Ethylene Butene / Styrene (SEBS), Styrene / Butadiene / Styrene (SBS), Styrene / Isoprene / Styrene (SIS), Styrene / Ethylene Propylene / Styrene (SEPS) block copolymers, -Ethylene and vinyl acetate copolymer (EVA) (containing up to 40% vinyl acetate by weight), - Copolymers of ethylene and alkyl (meth)acrylates (containing up to 40% by weight of alkyl (meth)acrylates), - A copolymer of ethylene, vinyl acetate (EVA) and alkyl (meth)acrylate, containing up to 40% by weight of comonomer.

[0085] The functionalized polyolefin may also be selected from propylene-based ethylene / propylene copolymers grafted with maleic anhydride and then condensed with a monoaminated polyamide (or polyamide oligomer) (products described in EP 0 342 066).

[0086] The functionalized polyolefin may be a copolymer or terpolymer of at least the following units: (1) ethylene, (2) an alkyl (meth)acrylate or a saturated carboxylic acid vinyl ester, and (3) an anhydride, such as maleic or (meth)acrylic anhydride, or an epoxy, such as glycidyl (meth)acrylate.

[0087] Examples of the latter type of functionalized polyolefins include the following copolymers, in which ethylene preferably constitutes at least 60% by weight and the termonomer (functional group) constitutes, for example, from 0.1% to 10% by weight of the copolymer: ethylene / alkyl(meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers, - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers, Ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0088] In the aforementioned copolymers, the (meth)acrylic acid can be salified with Zn or Li.

[0089] The term "alkyl (meth)acrylate" means C1 to C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0090] Additionally, the above functionalized polyolefins can also be crosslinked by any suitable process or agent, such as diepoxy, diacid, peroxide, etc. The term functionalized polyolefin also includes mixtures of the above polyolefins with difunctional agents, such as diacids, dianhydrides, diepoxy, etc., capable of reacting therewith, or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0091] The copolymers described above may be randomly or sequentially copolymerized and may have a linear or branched structure.

[0092] The molecular weight, MFI index and density of these polyolefins can also vary within wide limits, as will be appreciated by those skilled in the art. MFI is the abbreviation for Melt Flow Index. It is measured according to standard ASTM 1238.

[0093] In one embodiment, the polyolefin is crosslinked.

[0094] According to one embodiment, the functionalized polyolefin may be selected from polyethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylenes, in particular VLDPE (very low density polyethylene).

[0095] As an example of such a compound, mention may in particular be made of the product Orevac IM800 sold by SK Functional Polymer.

[0096] According to one embodiment, the functionalized polyolefin may be selected from ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers, ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers, ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0097] As an example of such a compound, mention may in particular be made of the product Lodater AX8900 sold by SK Functional Polymer.

[0098] Plasticizer (d) Said at least one plasticizer (e) may be present in an amount ranging from 2% to 8% by weight and in particular from 2% to 6% by weight relative to the total weight of the composition.

[0099] The plasticizer may be any plasticizer commonly used in polyamide-based compositions.

[0100] Advantageously, plasticizers are used that exhibit good thermal stability so that no smoke is produced during the steps of mixing the various polymers and converting the resulting composition.

[0101] In particular, this plasticizer benzenesulfonamide derivatives, such as n-butylbenzenesulfonamide (BBSA), ortho and para isomers of ethyltoluenesulfonamide (ETSA), N-cyclohexyltoluenesulfonamide, N-(2-hydroxypropyl)benzenesulfonamide (HP-BSA); Hydroxybenzoic acid esters such as 2-ethylhexyl parahydroxybenzoic acid (EHPB) and 2-hexyldecyl parahydroxybenzoic acid (HDPB), Esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol, and Esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate You can choose from.

[0102] A preferred plasticizer is n-butylbenzenesulfonamide (BBSA).

[0103] Another more particularly preferred plasticizer is N-(2-hydroxypropyl)benzenesulfonamide (HP-BSA), since the latter exhibits the advantage of preventing the formation of deposits in the extrusion screw and / or die ("die roll") during the deformation stage due to extrusion.

[0104] Obviously, mixtures of plasticizers may be used.

[0105] Regarding additive (e) Said at least one additive (f) may be present in an amount ranging from 0% to 10% by weight, and in particular from 0.1% to 5% by weight, relative to the total weight of the composition.

[0106] The at least one additive may be selected from stabilizers, dyes, conversion aids (processing aids), surfactants, nucleating agents, pigments, gloss agents, antioxidants, lubricants, waxes, flame retardant synergists, or mixtures thereof.

[0107] Advantageously, the at least one additive is chosen from antioxidants, colour pigments and flame retardant synergists, in particular melamine-based nitrogen synergists.

[0108] By way of example, the stabilizer may be a UV stabilizer, an organic stabilizer, or more generally a combination of phenolic type antioxidants (e.g., Irganox® 245, 1098, or 1010 types from BASF), phosphorous type antioxidants (e.g., Irgafos® 126 or Irgafos® 168 from BASF), and optionally other stabilizers such as HALS, meaning hindered amine light stabilizers (e.g., Tinuvin® 770 from BASF), UV absorbers (e.g., Tinuvin® 312 from BASF), or phosphorus-based stabilizers. Also usable are amine type antioxidants such as Naugard® 445 from Crompton, or multifunctional stabilizers such as Nylostab® S-EED from Clariant.

[0109] The stabilizer may be a mineral stabilizer, such as a copper-based stabilizer. Examples of such mineral stabilizers include copper halides and copper acetate. Other metals, such as silver, may then be considered, but these are known to be less effective. These copper-based compounds are usually combined with alkali metal halides, especially potassium halides.

[0110] The flame retardant synergists are in particular as described in JGB Publication No. 2005121234.

[0111] Nitrogen synergists and phosphorus / nitrogen synergists can be selected.

[0112] Nitrogen synergists preferably include benzoguanamine, tris(hydroxyethyl)isocyanurate, allantoin, glycoluril, melamine, melamine cyanurate, dicyandiamide, guanidine and carbodiimide.

[0113] The nitrogen synergist preferably comprises a melamine condensation product, for example melem, melam or melon, or higher condensation compounds of this type, or mixtures thereof, which may be prepared, for example, by the process described in US Pat. No. 5,985,960.

[0114] The phosphorus / nitrogen synergist may comprise a reaction product of melamine with phosphoric acid or condensed phosphoric acids, may comprise a reaction product of a melamine condensation product with phosphoric acid or condensed phosphoric acids, or may comprise a mixture of the specified products.

[0115] In one embodiment, the additives are selected from antioxidants, color pigments, and flame retardant synergists, especially nitrogen synergists, and especially melamine-based synergists.

[0116] About the configuration According to one embodiment, the flame retardant composition comprises, by weight: (a) 30% to 85% by weight, for example 33% to 83% by weight, in particular 50% to 78.9% of at least one semicrystalline aliphatic polyamide having an intrinsic viscosity in the range of 1.2 to 1.6, in particular in the range of 1.2 to 1.5, in particular in the range of 1.3 to 1.5, in particular strictly below 1.5, in particular in the range of 1.30 to 1.48, measured in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid at a temperature of 20° C. and at a concentration of 0.5%, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, The total of the components (a) to (e) is 100% by weight.

[0117] According to one embodiment, the composition comprises, by weight: (a) 30% to 85% by weight, for example 33% to 83% by weight, in particular 50% to 78.9% of at least one semicrystalline aliphatic polyamide having an intrinsic viscosity in the range of 1.2 to 1.6, in particular in the range of 1.2 to 1.5, in particular in the range of 1.3 to 1.5, in particular strictly below 1.5, in particular in the range of 1.30 to 1.48, measured in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid at a temperature of 20° C. and at a concentration of 0.5%, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, The compositions exclude PA12.

[0118] According to one embodiment, the composition comprises, by weight: (a) 30% to 85% by weight, for example 33% to 83% by weight, in particular 50% to 78.9% of at least one semicrystalline aliphatic polyamide having an intrinsic viscosity in the range of 1.2 to 1.6, in particular in the range of 1.2 to 1.5, in particular in the range of 1.3 to 1.5, in particular strictly below 1.5, in particular in the range of 1.30 to 1.48, measured in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid at a temperature of 20° C. and at a concentration of 0.5%, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, PA12 is not included, and the total of components (a) to (e) is 100% by weight.

[0119] In one embodiment, the composition comprises, by weight: (a) 50% to 78.9% by weight of at least one semicrystalline aliphatic polyamide, determined according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and at a concentration of 0.5% by weight, having an intrinsic viscosity in the range of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, in particular strictly less than 1.5, in particular 1.30 to 1.48, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 20%, in particular 5% to 15%, of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, PA12 is not included, and the total of components (a) to (e) is 100% by weight.

[0120] In another embodiment, the composition comprises, by weight: (a) 50% to 78.9% by weight of at least one semicrystalline aliphatic polyamide, determined according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and at a concentration of 0.5% by weight, having an intrinsic viscosity in the range of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, in particular strictly less than 1.5, in particular 1.30 to 1.48, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 15% by weight of at least one functionalized polyolefin; (d) from 2% to 8% by weight, in particular from 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, The composition does not, for example, contain PA12 and the sum of components (a) to (e) is equal to 100% by weight.

[0121] In yet another embodiment, the composition comprises, by weight: (a) 50% to 78.9% by weight of at least one semicrystalline aliphatic polyamide, determined according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and at a concentration of 0.5% by weight, having an intrinsic viscosity in the range of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, in particular strictly less than 1.5, in particular 1.30 to 1.48, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt%, for example, 14 wt% to 20 wt% of at least one phosphinate flame retardant; (c) 5% to 15% by weight of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0% to 10% by weight, in particular 0.1% to 5% by weight, of at least one additive; Including, The composition does not, for example, contain PA12 and the sum of components (a) to (e) is equal to 100% by weight.

[0122] In yet another embodiment, the composition comprises, by weight: (a) 50% to 78.9% by weight of at least one semicrystalline aliphatic polyamide, determined according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and at a concentration of 0.5% by weight, having an intrinsic viscosity in the range of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, in particular strictly less than 1.5, in particular 1.30 to 1.48, (b) 10 wt% to 30 wt%, for example, 10 wt% to 25 wt%, for example, 14 wt% to 25 wt%, for example, 14 wt% to 22 wt%, for example, 17 wt% to 22 wt% of at least one phosphinate-based flame retardant; (c) 5% to 15% by weight of at least one functionalized polyolefin; (d) 2% to 8% by weight, in particular 2% to 6% by weight, of at least one plasticizer, (e) 0.1% to 5% by weight of at least one additive; The composition does not, for example, contain PA12 and the sum of components (a) to (e) is equal to 100% by weight.

[0123] In all these embodiments, the present invention is also directed to said compositions wherein the term "comprises" is replaced with the term "consisting of."

[0124] The expression "said composition excluding PA12" means, for the purposes of the present invention, that the composition comprises less than 5% by weight of PA12 relative to its total weight, in particular less than 2% by weight, in particular less than 1% by weight, in particular less than 0.5% by weight and in particular 0% by weight.

[0125] In particular, in all embodiments, the present invention is also directed to compositions in which the sum of components (a)-(e) is equal to 100% by weight.

[0126] In a first variant of all these embodiments, the composition is free of melamine and may in particular comprise less than 5% by weight of melamine, in particular less than 2% by weight of melamine or even 0% by weight of melamine relative to the total weight of the composition.

[0127] Melamine is understood to mean both melamine and melamine cyanurate or nitrogen compounds based on melamine.

[0128] In this case it is clear that the flame retardant must not be melamine, melamine cyanurate or nitrogen compounds based on melamine.

[0129] The presence or absence of melamine depends on the processing temperature of the product; at high temperatures, melamine is too temperature sensitive.

[0130] The use of melamine as flame retardant is not possible during the processing of such polymers as are targeted according to the invention, i.e. semicrystalline aliphatic polymers having an intrinsic viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, in particular strictly less than 1.5, determined in accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and a concentration of 0.5% by weight.

[0131] The processing conditions of such semi-crystalline aliphatic polymers, particularly temperature and / or shear, can lead to degradation of such flame retardants, resulting in poor flame retardant properties.

[0132] Therefore, by using melamine as a flame retardant it is not possible to obtain a composition according to the invention having both the desired flame retardant and mechanical properties.

[0133] On the contrary, the inventors have found that only compositions comprising a phosphine-based flame retardant (b) make it possible to obtain an improved, and in particular an optimal, compromise between mechanical strength and flame retardancy.

[0134] According to one embodiment, the composition of the invention may comprise less than 50% by weight, in particular less than 30% by weight, in particular less than 20% by weight, in particular less than 10% by weight, in particular less than 5% by weight of PEBA as defined above.

[0135] In particular, according to one embodiment, the composition of the invention may in particular comprise less than 1% by weight of PEBA, in particular less than 0.5% by weight of PEBA, or even 0% by weight of melamine, relative to the total weight of said composition.

[0136] In a second variation of these embodiments, the composition does not include PEBA.

[0137] According to one embodiment, the composition of the invention may comprise less than 40% by weight, in particular less than 30% by weight, in particular less than 20% by weight, in particular less than 10% by weight, in particular less than 5% by weight of reinforcing fibers as defined above.

[0138] In particular, according to one embodiment, the composition of the invention may in particular comprise less than 1% by weight of reinforcing fibers, in particular less than 0.5% by weight of reinforcing fibers, or even 0% by weight of reinforcing fibers, relative to the total weight of said composition.

[0139] In a third variant of all these embodiments, the composition does not comprise reinforcing fibers.

[0140] In a fourth variant of all these embodiments, the composition is free of melamine and PEBA.

[0141] In a fifth variant of all these embodiments, the composition is free of melamine and reinforcing fibers.

[0142] In a sixth variant of all these embodiments, the composition does not comprise PEBA and reinforcing fibers.

[0143] In a seventh variant of all these embodiments, the composition is free of melamine, PEBA and reinforcing fibers.

[0144] According to one embodiment, the composition of the invention may comprise less than 50% by weight, in particular less than 30% by weight, in particular less than 20% by weight, in particular less than 10% by weight, in particular less than 7.5% by weight, in particular less than 5% by weight of PA12 as defined above.

[0145] In particular, according to one embodiment, the composition of the invention may in particular comprise less than 1% by weight of PA12, in particular less than 0.5% by weight of PA12, and even 0% by weight of PA12, relative to the total weight of said composition.

[0146] In one embodiment, the composition is intended for railway applications.

[0147] Possible exclusion of PEBA Polyether block amides (PEBA) are copolymers comprising amide units (Ba1) and polyether units (Ba2), the amide units (Ba1) being units derived from at least one amino acid, at least one lactam, or at least one diamine, which is chosen from linear or branched aliphatic diamines, aromatic diamines, or mixtures thereof; at least one carboxylic diacid, said diacid being chosen from aliphatic diacids or aromatic diacids, Said polyether units (Ba2) are derived in particular from at least one polyalkylene ether polyol, in particular a polyalkylene ether diol.

[0148] Potentially excluded reinforcing fibers The reinforcing fibres may in particular be chosen from reinforcing fibres of mineral, organic or vegetable origin.

[0149] Among the fibers of mineral origin, mention may be made, for example, of carbon fibers, glass fibers, basalt fibers or basalt-based fibers, silica fibers or silicon carbide fibers.Among the fibers of organic origin, mention may be made, for example, of fibers based on thermoplastic or thermosetting polymers, such as semi-aromatic polyamide fibers, aramid fibers, polyolefin fibers, etc.Among the fibers of plant origin, mention may be made of natural fibers based on flax, hemp, lignin, bamboo, silk, especially spider silk, sisal, other cellulose fibers, especially viscose fibers.

[0150] In one embodiment, the composition after processing has a Limiting Oxygen Index (LOI)>28.

[0151] According to another aspect, the invention relates to a tube, in particular a partially corrugated tube, comprising at least one layer of a composition as defined above.

[0152] The tube may be a single-wall or multi-wall tube.

[0153] It may be partially smooth or completely smooth.

[0154] In particular, smooth tubes are used for circulating pressurized gas.

[0155] It is also possible to make the signal partially wavy.

[0156] Corrugated tubes are used especially as cable ducts.

[0157] The expression "partially corrugated" means that the pipe has a corrugated tubular shape over part of its length. The corrugated portion may form a single part or multiple parts of the structure, where two corrugated portions are separated by a smooth portion.

[0158] The corrugated sections allow for increased deformation and elongation capabilities of the tubular structure, especially in areas where small angles are required.

[0159] Advantageously, the tubular structure is corrugated over at least 10% of its length.

[0160] Advantageously, the tubular structure is corrugated over a proportion of between 10% and more than 90% of its length.

[0161] Advantageously, the tubular structure is corrugated for between 20% and 90% of its length.

[0162] Advantageously, the tubular structure is corrugated over 30% to 90% or more of its length.

[0163] Advantageously, the tubular structure is corrugated over 40% to 90% or more of its length.

[0164] Advantageously, the tubular structure is corrugated over a proportion of 50% to more than 90% of its length.

[0165] Advantageously, the tubular structure is corrugated over a proportion of between 60% and more than 90% of its length.

[0166] Advantageously, the tubular structure is corrugated over 70% to more than 90% of its length.

[0167] Advantageously, the tubular structure is corrugated over more than 80% to 90% of its length.

[0168] Advantageously, the tubular structure is corrugated over more than 90% of its length.

[0169] According to yet another aspect, the present invention relates to the use of a composition as defined above, for the manufacture of flame-retardant articles for the railway sector, in particular for trains.

[0170] Advantageously, said article is intended for the interior or exterior of a train.

[0171] In one embodiment, the molded article is obtained by extrusion.

[0172] Advantageously, the moulded article obtained by extrusion is a corrugated tube used as a cable duct or a smooth tube allowing the circulation of a pressurised fluid, in particular a pressurised gas, in particular compressed air.

[0173] According to another aspect, the invention relates to the use of a composition such as defined above for the protection of a part comprising, totally or partly, metal.

[0174] Preferably, the invention relates to this use for imparting electrical insulating and anti-corrosive properties to the metal-based materials to which it is applied.

[0175] For the purposes of the present invention, the term "metal-based material" is intended to mean a metal element made entirely or partly of metal, or a plastic or elastic material consisting of metal fibers.

[0176] The use according to the invention is consequently intended to provide electrical insulation and corrosion protection to parts, including parts containing metal, which are coated with said copolymer.

[0177] These elements can have a wide variety of shapes, such as cables, ropes, tubes, containers, films, plates, etc.

[0178] According to yet another aspect, the invention relates to a method for preparing an article for the railway sector, comprising a step of extruding a composition as defined above. EXAMPLES

[0179] Working Example The compositions in Table 1 were prepared by melt blending the polymer granules with flame retardants, polyolefins, plasticizers and additives. The blending was carried out by compounding in a 40 mm diameter co-rotating twin screw extruder with a flat temperature profile (T°) of 250° C. The screw speed was 300 rpm and the throughput was 70 kg / h.

[0180] Polyamides, polyolefins and additives are introduced into the main hopper during the compounding process. Flame retardants are added to the molten polymer midway through the screw via a side feeder. Plasticizers are also pumped into the molten polymer.

[0181] This composition was then injection molded at a temperature of 250° C. to obtain the samples to be tested.

[0182] The compositions (samples) according to the invention and the comparative compositions were tested in a limiting oxygen index measurement carried out in accordance with standard ISO 4589-2:2017 using test specimens of 80 x 10 x 4 mm.

[0183] The smoke density during combustion is measured on a 75 x 75 x 1 mm plate according to standard ISO 5659-2:2017. The maximum opacity is recorded during 10 minutes of combustion.

[0184] The toxicity of the smoke is measured using a 30 g sample at a temperature of 600°C in accordance with standard NF X70-100-1:2006.

[0185] The intrinsic viscosity (IV) was determined according to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, at a temperature of 20° C. and a concentration of 0.5% by weight.

[0186] The impact strength was determined according to ISO 179:1eA:2010 (Charpy impact) on notched bars with dimensions 80 mm x 10 mm x 4 mm, on dry samples at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 10% or at -30°C ± 2°C and a relative humidity of 50% ± 10%.

[0187] Tensile modulus, stress at 50% strain, stress at break and elongation at break were measured on dry samples according to standard ISO 527-1:201 at 23° C. For the applications targeted by the present invention, the target properties are: modulus <1200 MPa, elongation at break >100%, stress at 50% strain <40 MPa, stress at break <50 MPa.

[0188] The machine used is INSTRON type 5966. The crosshead speed is 1 mm / min for the measurement of elastic modulus, and 50 mm / min for the measurements of stress at 50% strain, stress at break, and elongation at break. The test conditions are 23°C ± 2°C, and dry samples are used.

[0189] Fatigue strength is measured by Rossflex testing on ten unnotched bars of 150 x 20 x 2 mm. The measurements are carried out as follows: Number of cycles: 400000 Temperature: -10℃ Bending frequency: 100 cycles / min Bending angle: 60° Test specimen conditioning: 70℃ for 7 days After 400,000 cycles, none of the bars obtained from the inventive formulations E1 to E6 have broken, whereas the bars obtained from the comparative compositions CE1, CE3 and CE4 have broken. TIFF2025514944000003.tif202170TIFF2025514944000004.tif157170Orevac® IM800: Maleic anhydride grafted VLDPE (very low density polyethylene) (SK Functional Polymers). Lotader® AX8900: Copolymer of ethylene, methyl acrylate and glycidyl methacrylate (Et / MA / GMA-68 / 24 / 8 by weight) (SK Functional Polymers). Renol® black AF 34132010-ZA: A black masterbatch sold by Clariant. Anox® TL 91: An antioxidant sold by SI Group. Exolit® OP1311 is a product of Clariant (aluminum diethylphosphinate-based flame retardant). Melapur MC25 is a BASF product (melamine cyanurate flame retardant) BBSA (Benzyl butyl sulfonamide) Fire resistance: The EN 45545 standard specifies various specifications depending on the material category. Polyamide tubes correspond to categories R22 and R23 and have the following fire requirements (table 3): TIFF2025514944000005.tif52170

[0190] Products are therefore classified according to their Limiting Oxygen Index and the density and toxicity of the smoke they produce during combustion. Three hazard level classifications, HL1, HL2 and HL3, are achieved according to their fire properties.

[0191] The higher the classification, the more likely the polyamide grade can be used in heavy trains, whereas a product classified as HL1 cannot be used in underground subway trains, for example.

[0192] CIT: conventional toxicity index;

[0193] The examples particularly show the effect of intrinsic viscosity and the range of plasticizers and other ingredients on the mechanical criteria, especially fatigue strength and low temperature impact.

[0194] Corrugated tubes with an outer diameter of 32 mm were extruded at 230° C. using the formulations of Examples E1 to E6 according to the invention, which confirm the mechanical performance and fire resistance of these products.

Claims

1. By weight, (a) Conforming to standard ISO 307:2007, but using m-cresol instead of sulfuric acid, and having an intrinsic viscosity in the range of 1.2 to 1.6, particularly in the range of 1.2 to 1.5, particularly in the range of 1.3 to 1.5, particularly strictly less than 1.5, particularly in the range of 1.30 to 1.48, 30% to 85% by weight, for example 33% to 83% by weight, particularly in the range of 50% to 78.9% by weight of at least one semicrystalline aliphatic polyamide, having an intrinsic viscosity in the range of 1.2 to 1.6, particularly in the range of 1.2 to 1.5, particularly in the range of 1.3 to 1.5, particularly strictly less than 1.5, particularly in the range of 1.30 to 1.48, and (b) at least one phosphinate-based flame retardant in an amount of 10% to 30% by weight, for example, 10% to 25% by weight, for example, 14% to 25% by weight, for example, 14% to 22% by weight, for example, 17% to 22% by weight, (c) 5% to 20%, particularly 5% to 15%, of at least one functionalized polyolefin, (d) at least one plasticizer in an amount of 2% to 8%, particularly 2% to 6%, (e) at least one additive in an amount of 0-10%, particularly 0.1-5%, and A flame-retardant composition containing [a specific substance].

2. Semicrystalline aliphatic polyamide (a) at least one C ６ ~C １８ Amino acids, preferably one C ９ ~C １８ Furthermore, C is given priority. １０ ~C １８ , especially C １０ ~C １１ amino acids, or At least one C ６ - C １８ lactam, preferably one C ９ - C １８ and more preferably C １０ - C １８ and especially C １０ - C １１ amino acid, or at least one C ４ ~C ３６ Prioritizing C ６ ~C １８ Prioritizing C ６ ~C １２ C is preferred. １０ ~C １２ Diamine X and at least one C ４ ~C ３６ Prioritizing C ６ ~C １８ Prioritizing C ６ ~C １２ C is preferred. １０ ~C １２ Dicarboxylic acid Y and The composition according to claim 1, characterized in that it is obtained by polycondensation.

3. The composition according to claim 1, characterized in that the polyamide is a long-chain polyamide having 8 or more carbon atoms per nitrogen atom, particularly 9 or more, and especially 10 or more.

4. The composition according to claim 3, characterized in that the long-chain polyamide is selected from PA610, PA612, PA1010, PA1012, and PA11.

5. The composition according to claim 4, characterized in that the at least one semicrystalline aliphatic polyamide is selected from PA1010, PA1012, and PA11, particularly PA11.

6. The composition according to claim 1, characterized in that the flame retardant is a metal salt selected from a metal salt of phosphinic acid, a metal salt of diphosphinic acid, a polymer containing at least one metal salt of phosphinic acid, and a polymer containing at least one metal salt of diphosphinic acid.

7. The composition according to claim 1, characterized in that the additive is selected from antioxidants, coloring pigments, flame retardant synergies, particularly nitrogen synergies, and particularly melamine-based synergies.

8. The composition according to claim 1, characterized in that it does not contain polyether block amide (PEBA).

9. The composition according to claim 1, characterized in that it does not contain reinforcing fibers.

10. By weight, (a) In accordance with standard ISO 307:2007, but using m-cresol instead of sulfuric acid, and measuring at a temperature of 20°C and a concentration of 0.5 wt%, the intrinsic viscosity is 1.2 to 1.6, particularly 1.2 to 1.5, particularly 1.3 to 1.5, and the intrinsic viscosity is 33% to 83%, particularly 50% to 78.9%, of at least one semicrystalline aliphatic polyamide, (b) 10% to 25% by weight, particularly 14% to 20% by weight, of at least one phosphine-based flame retardant, (c) 5% to 20%, particularly 5% to 15%, of at least one functionalized polyolefin, (d) at least one plasticizer in an amount of 2% to 8%, particularly 2% to 6%, (e) at least one additive in an amount of 0-10%, particularly 0.1-5%, and Includes, Excluding PA12, the sum of components (a) to (e) is 100% by weight. The composition according to claim 1.

11. A tube, particularly a partially corrugated one, comprising at least one layer made of the composition according to claim 1.

12. Use of the composition according to claim 1 for the railway sector, particularly for the manufacture of flame-retardant articles for trains.

13. The use according to claim 12, characterized in that the article is intended for use inside or outside a train.

14. The use according to claim 12, characterized in that the article is obtained by extrusion molding.

15. The use according to claim 14, characterized in that the article obtained by extrusion molding is a corrugated tube used as a cable duct, or a smooth tube that enables the circulation of pressurized gas.

16. Use of the composition according to claim 1 for protecting a part that is made entirely or partially of metal.

17. A method for preparing articles for the railway sector, comprising the step of extruding the composition according to claim 1.