DUCTILE FIRE-RETARDANT POLYAMIDE COMPOSITIONS AND THEIR USE, PARTICULARLY FOR RAILROAD APPLICATIONS

Abstract

The present invention relates to a flame-retardant composition comprising by weight: (a) 33 to 83%, in particular 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide having an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass, (b) 10 to 25%, in particular 14 to 20%, of at least one phosphinate-type flame retardant, (c) 5 to 20%, in particular 5 to 15%, of at least one functionalized polyolefin, (d) 2 to 8%, in particular 2 (e) 6% of at least one plasticizer, (a) 0 to 10%, in particular 0.1 to 5% of at least one additive, said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%

Description

Title of the invention: DUCTILE FIRE-RETARDANT POLYAMIDE COMPOSITIONS AND THEIR USE, PARTICULARLY FOR RAILROAD APPLICATIONS

[0001] The present invention relates to ductile flame-retardant polyamide compositions and their use in particular for railway applications and the preparation of tubes, in particular corrugated tubes.

[0002] The railway sector tends to use materials with high mechanical resistance and good resistance to aging.

[0003] More recently, materials used in trains must meet technical requirements in terms of fire resistance. These requirements depend on the type of object and its use in the train. The EN 45545 standard sets out different specifications depending on the material category. Polyamide tubes correspond to categories R22 and R23.

[0004] The products are classified according to their oxygen limit index as well as the density and toxicity of the fumes they generate during combustion. Three classifications, HL1, HL2, or HL3, can be achieved depending on their fire properties.

[0005] The higher this classification, the more the product can be used in a wide range of train types, whereas a product classified as HL1 cannot be used in an underground metro, for example.

[0006] The HL2 category now covers the majority of the existing market and is the target in general, which means in particular a limit oxygen level (LOI) measurement > 28.

[0007] Beyond this fire resistance, the materials used in trains are also subjected to numerous mechanical stresses which cover the following properties:

[0008] - Flexibility: the modulus must be between 500 and 1200 MPa,

[0009] - Flexibility / Bendability: Ability to deform a tube without kinking, associated with the com behavior at the plasticity threshold (low stress and high elongation)

[0010] - Tensile strength: the elongation at break in tension must be greater than 100%

[0011] - Shock resistance over a temperature range down to -30°C,

[0012] - Fatigue resistance.

[0013] These properties must be maintained over time. The products must therefore be able to withstand accelerated thermal aging for several days at 150°C.

[0014] Finally, the extrusion of the polyamide must remain easy, which limits the viscosity that the formulation may exhibit.

[0015] Prior art already describes flame-retardant formulations as in US20170037198 which describes formulations for the railway field focusing specifically on a PA12 matrix.

[0016] However, these formulations do not meet all the above-listed requirements, in particular for mechanical properties.

[0017] Still in the railway field, the international application WO 2013 / 092302 deals with glass fiber reinforced polyamides and flame retardanted by a melamine derivative.

[0018] Finally, US application 2007 / 0021535 combines the use of phosphinate, melamine cyanurate and polyol as a flame retardant of a polyamide.

[0019] Nevertheless, the same disadvantages relating to the above-listed requirements, in particular for mechanical properties, remain.

[0020] New products must therefore be developed to allow good protection of equipment and passengers in the event of fire.

[0021] A more advanced formulation presenting an improved compromise between mechanical strength and fire resistance is therefore necessary.

[0022] The present invention therefore relates to a flame-retardant composition comprising by weight:

[0023] (a) from 33 to 83%, in particular from 50 to 78.9%, of at least one aliphatic polyamide semi-crystalline having an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0024] (b) from 10 to 25%, in particular from 14 to 20% of at least one type of flame retardant phosphinate,

[0025] (c) from 5 to 20%, in particular from 5 to 15% of at least one functionalized polyolefin,

[0026] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0027] (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive,

[0028] said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0029] The inventors therefore found that a semi-crystalline aliphatic polyamide, in particular proportions and having a particular inherent viscosity, associated with a phosphinate-type flame retardant, a functionalized polyolefin and a plasticizer, all three in a similarly particular proportion, with optionally an additive, made it possible to constitute a composition meeting all the above-listed requirements.

[0030] The viscosity of the semi-crystalline aliphatic polyamide matrix is ​​essential, particularly for fatigue resistance. An inherent viscosity that is too low, A viscosity below 1.2 will not be sufficiently resistant to fatigue. A viscosity that is too high, above 1.6, especially above 1.5, will prevent the composition from being shaped, particularly into corrugated tubes.

[0031] The range of plasticizers makes it possible to provide the composition with a sufficiently low modulus without compromising cold shock resistance.

[0032] The functionalized polyolefin range makes it possible to obtain good fatigue resistance without significantly increasing the fire sensitivity of said composition.

[0033] The range of flame retardants makes it possible to obtain sufficient fire resistance without making the product too fragile.

[0034] This is therefore a compromise which can only be achieved by the particular selection of the ranges of the different constituents of the composition.

[0035] Advantageously, said composition is intended for a railway application.

[0036] Regarding semi-crystalline aliphatic polyamide (a)

[0037] Said at least one semi-crystalline aliphatic polyamide (a) is present from 33 to 83%, in particular from 50 to 78.9% by weight in the composition.

[0038] Semi-crystalline polyamide is understood to be a material which is generally solid at room temperature, and which softens when the temperature increases, in particular after passing its glass transition temperature (Tg), and which may exhibit a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature decreases below its crystallization temperature.

[0039] Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2:2013 and 11357-3:2013 respectively.

[0040] The average number molecular mass Mn of said semi-crystalline polyamide is preferably in a range from 10000 to 85000, in particular from 10000 to 60000, preferably from 10000 to 50000, even more preferably from 12000 to 50000.

[0041] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0042] The term polyamide includes both homopolyamides and copolyamides.

[0043] Said at least one aliphatic semi-crystalline 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 mixtures thereof.

[0044] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, said at least one lactam may be chosen among a lactam in the C6 to Cl8 range, preferentially in C9 to Cl8, more preferentially in C10 to C18, more preferentially in ClO to Cl1. A lactam in the C8 to Cl8 range is notably decanolactam, rundecanolactam.

[0045] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, it may therefore comprise a single lactam or several lactams.

[0046] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, said at least one amino acid may be chosen from an amino acid in C6 to Cl8, preferably in C9 to Cl8, more preferably in C10 to C18, more preferably in ClO to Cl1.

[0047] A C6 to C18 amino acid is in particular 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid and 11-aminoundecanoic acid and its derivatives, in particular N-heptyl-11-aminoundecanoic acid.

[0048] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, it may therefore comprise a single amino acid or several amino acids.

[0049] Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single amino acid and said amino acid is chosen from 10-aminodecanoic acid, and 11-aminoundecanoic acid, advantageously 11-aminoundecanoic acid.

[0050] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine X in C4-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12, with at least one diacid Y in C4-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12, then said at least one diamine in X is an aliphatic diamine and said at least one diacid Y is an aliphatic diacid.

[0051] The diamine can be linear or branched. Advantageously, it is linear.

[0052] Said at least one diamine X in C4-C36 may in particular be selected 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-dodecamethylediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids.

[0053] Advantageously, said at least one diamine X is in C6-C18 and selected from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, the 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.

[0054] Advantageously, said at least one diamine X in C6 to C12, is in particular selected from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0055] Advantageously, the diamine X used is in C12 C10, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0056] Said at least one dicarboxylic acid Y in C4 to C36 may be selected from succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and diacids obtained from fatty acids.

[0057] The diacid can be linear or branched. Advantageously, it is linear.

[0058] Advantageously, said at least one dicarboxylic acid Y is in C6 to Cl8 and is selected from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0059] Advantageously, said at least one dicarboxylic acid Y is in C6 to C12 and is selected from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid.

[0060] Advantageously, said at least one dicarboxylic acid Y is in C12 C10 and is selected from sebacic acid, undecanedioic acid, dodecanedioic acid.

[0061] When said aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y it can therefore comprise a single diamine or several diamines and a single dicarboxylic acid or several dicarboxylic acids.

[0062] Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single diamine X with a single dicarboxylic acid Y.

[0063] In one embodiment, said at least one polyamide is a long-chain polyamide having a number of carbons per nitrogen atom greater than or equal to 8, in particular greater than or equal to 9, especially greater than or equal to 10.

[0064] In another embodiment, said at least one semi-crystalline aliphatic polyamide is selected from the polyamides PA610, PA612, PA1010, PA1012 and PAU.

[0065] Advantageously, said at least one semi-crystalline aliphatic polyamide is selected from the polyamides PA 1010, PA 1012 and PAU, in particular PAU.

[0066] Regarding the phosphinate-type flame retardant (b)

[0067] Said at least one phosphinate-type flame retardant (c) is present from 10 to 25%, in particular from 14 to 20% by weight in the composition.

[0068] The flame retardant is in particular a metallic salt selected from a metallic salt of phosphinic acid, a metallic salt of diphosphinic acid, a polymer containing at least one metallic salt of phosphinic acid, or a polymer containing at least one metallic salt of diphosphinic acid. The flame retardant may also be a mixture of the aforementioned flame retardants.

[0069] The flame retardant may also be chosen from the following metallic salt of phosphinic acid of formula (I) and the following metallic salt of diphosphinic acid of formula (II):

[0070] [Chem.l] Q R7...... It >~O R2

[0071] [Chem.l] II O—P~ R3—P—O II R1 R2

[0072] with

[0073] RI and R2, independently of each other, denote a linear or branched C1-C6 alkyl group, or an aryl group;

[0074] R3 represents a linear or branched C1-C10 alkylene group, a C6-C10 arylene group, a C6-C10 alkylarylene group, or a C6-C10 arylalkylene group,

[0075] M is an ion of Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, K and / or a protonated amine base

[0076] m denotes an integer from 1 to 4,

[0077] n denotes an integer from 1 to 4,

[0078] x denotes an integer from 1 to 4,

[0079] n and m being chosen so that the salt is neutral, that is to say, that it does not carry an electric charge.

[0080] Preferably, M represents a calcium, magnesium, aluminum or zinc ion.

[0081] Preferably, RI and R2, independently of each other, denote a group methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl and / or phenyl.

[0082] Preferably, R3 represents a group of 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. Regarding functionalized polyolefin (c)

[0083] Said at least one functionalized polyolefin (d) is present from 5 to 20%, in particular from 5 to 15% by weight in the composition.

[0084] The functionalized polyolefin can be a polymer of alpha olefins having reactive motifs (the functionalities); such reactive motifs are acid, anhydride, or epoxy functions. By way of example, one can cite non-functionalized polyolefins grafted or co- or ter-polymerized by unsaturated epoxides such as glycidyl (meth)acrylate, or by carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (the latter being able to be totally or partially neutralized by metals such as Zn, etc.) or even by anhydrides of carboxylic acids such as maleic anhydride.

[0085] An unfunctionalized polyolefin is classically a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, 1-butene, 1-octene, butadiene. Examples include:

[0086] - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene.

[0087] -homopolymers or copolymers of propylene.

[0088] - ethylene / alpha-olefin copolymers such as ethylene / propylene, the EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM).

[0089] - styrene / ethylene-butene / styrene block copolymers (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS).

[0090] - copolymers of ethylene with at least one product selected from the salts or the esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (e.g., methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer can reach 40% by weight.

[0091] A functionalized polyolefin is for example a PE / EPR mixture, the weight ratio of which can vary widely, for example between 40 / 60 and 90 / 10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate for example of 0.01 to 5% by weight.

[0092] The functionalized polyolefin can be selected from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the grafting ratio is, for example, from 0.01 to 5% by weight:

[0093] - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing, for example, 35 to 80% by weight of ethylene;

[0094] - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM).

[0095] - styrene / ethylene-butene / styrene block copolymers (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS).

[0096] - ethylene and vinyl acetate (EVA) copolymers, containing up to 40% in weight of vinyl acetate;

[0097] - ethylene and alkyl (meth)acrylate copolymers, containing up to 40% in weight of alkyl (meth)acrylate;

[0098] - ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0099] The functionalized polyolefin can also be selected from ethylene / propylene copolymers major in propylene grafted with maleic anhydride and then condensed with mono-amino polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0100] The functionalized polyolefin may also be a co- or ter polymer of at least the following motifs: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0101] By way of example of functionalized polyolefins of this latter type, the following copolymers may be cited, where ethylene preferably represents at least 60% by weight and where the ter monomer (the function) represents, for example, from 0.1 to 10% by weight of the copolymer:

[0102] - ethylene / alkyl (meth)acrylate / (meth)acrylic acid copolymers or maleic anhydride or glycidyl methacrylate;

[0103] - ethylene / vinyl acetate / maleic anhydride or methacrylate copolymers glycidyl;

[0104] - ethylene / vinyl acetate or alkyl (meth)acrylate / acid copolymers (meth)acrylic or maleic anhydride or glycidyl methacrylate.

[0105] In the preceding copolymers, (meth)acrylic acid can be salified with Zn or Li.

[0106] The term "alkyl (meth)acrylate" refers to methyl acrylates and alkyl acrylates in Cl to C8, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0107] Furthermore, the aforementioned functionalized polyolefins can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as a diacid, dianhydride, diepoxy, etc. capable of reacting with them or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0108] The copolymers mentioned above can be copolymerized statistically or sequentially and have a linear or branched structure.

[0109] The molecular weight, MFI, and density of these polyolefins can also vary considerably, a fact that those skilled in the art will appreciate. MFI, short for Melt Flow Index, is the melt flow index. It is measured according to ASTM 1238.

[0110] In one embodiment, the polyolefin is cross-linked. Regarding the plasticizer (d)

[0111] Said at least one plasticizer (e) may be present from 2 to 8%, in particular from 2 to 8% by weight in the composition.

[0112] The plasticizer may be a plasticizer commonly used in polyamide(s)-based compositions.

[0113] Advantageously, a plasticizer is used which has good thermal stability so that no fumes are formed during the mixing steps of the different polymers and transformation of the composition obtained.

[0114] In particular, this plasticizer may be selected from:

[0115] Benzene sulfonamide derivatives such as n-butyl benzene sulfonamide (BBSA), the ortho and para isomers of ethyl toluene sulfonamide (ETSA), N-cyclohexyl toluene sulfonamide and N-(2-hydroxypropyl) benzene sulfonamide (HP-BSA),

[0116] hydroxybenzoic acid esters such as ethyl-2-hexyl para-hydroxybenzoate (EHPB) and decyl-2-hexyl para-hydroxybenzoate (HDPB),

[0117] tetrahydrofurfuryl alcohol esters or ethers such as oligoethyleneoxy-tetrahydrofurfuryl alcohol, and

[0118] esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate.

[0119] A preferred plasticizer is n-butyl benzene sulfonamide (BBSA).

[0120] Another particularly preferred plasticizer is N-(2-hydroxypropyl)benzenesulfonamide (HP-BSA). The latter has the advantage of preventing the formation of deposits at the screw and / or the extrusion die ("die tears") during an extrusion transformation step.

[0121] A mixture of plasticizers can obviously be used. Regarding additives (e)

[0122] Said at least one of additive (f) may be present from 0 to 10%, in particular from 0.1 to 5% by weight in the composition.

[0123] At least one additive may be selected from stabilizers, colorants, processing aids, surfactants, nucleating agents, pigments, brighteners, antioxidants, lubricants, waxes, flame retardant synergists, or a mixture thereof.

[0124] Advantageously, at least one additive is chosen from antioxidants, colour pigments and flame retardant synergists, in particular nitrogen-based melamine synergists.

[0125] By way of example, the stabilizer may be a UV stabilizer, an organic stabilizer or more generally a combination of organic stabilizers, such as a phenol-type antioxidant (for example, of the type of that of irganox® 245 or 1098 or 1010 from BASF), a phosphite-type antioxidant (for example, irgafos® 126 or Irgafos® 168 from BASF) and possibly other stabilizers such as a HALS, which means Hindered Amine Light Stabiliser or hindered amine-type light stabilizer (for example, Tinuvin® 770 from BASF), an anti-UV (for example, Tinuvin® 312 from BASF), a phosphorus-based stabilizer. One can also use amine-type antioxidants such as Naugard® 445 from Crompton or polyfunctional stabilizers such as Nylostab® S-EED from Clariant.

[0126] This stabilizer can also be a mineral stabilizer, such as a copper-based stabilizer. Examples of such mineral stabilizers include copper halides and copper acetates. Other metals, such as silver, could also be considered, but these are known to be less effective. These copper-based compounds are typically associated with alkali metal halides, particularly potassium.

[0127] Synergistic flame retardant agents include those described in WO2005121234.

[0128] They can be chosen from nitrogen synergists and phosphorus / nitrogen synergists.

[0129] Nitrogen synergists preferably include benzoguanamine, tris(hydroxyethyl)isocyanurate, allantoin, glycolurile, melamine, melamine cyanurate, dicyandiamide, guanidine, carbodiimides.

[0130] Nitrogen synergists preferably comprise melamine condensation products. By way of example, melamine condensation products are melem, melam or melon, or compounds of this type with a higher degree of condensation, or a mixture thereof, and, by way of example, may be prepared by the process described in the United States 5,985,960.

[0131] Phosphorus / nitrogen synergists may include reaction products of melamine with phosphoric acid or with condensed phosphoric acids, or include reaction products of condensation products of melamine with phosphoric acid or condensed phosphoric acids, or include a mixture of the specified products.

[0132] In one embodiment, the additives are chosen from antioxidants, colour pigments and flame retardant synergists, in particular nitrogen synergists, especially melamine-based. Regarding the composition

[0133] The flame-retardant composition comprises by weight:

[0134] (a) from 33 to 83%, in particular from 50 to 78.9%, of at least one aliphatic polyamide semi-crystalline having an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, in particular 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0135] (b) from 10 to 25%, in particular from 14 to 20% of at least one type of flame retardant phosphinate,

[0136] (c) from 5 to 20%, in particular from 5 to 15% of at least one functionalized polyolefin,

[0137] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0138] (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive,

[0139] said composition being to the exclusion of PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0140] In one embodiment, said composition comprises by weight:

[0141] (a) from 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide exhibiting an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, especially 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0142] (b) 14 to 20% of at least one phosphinate-type flame retardant,

[0143] (c) from 5 to 20%, in particular from 5 to 15% of at least one functionalized polyolefin,

[0144] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0145] (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive,

[0146] said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0147] In another embodiment, said composition comprises by weight:

[0148] (a) from 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide exhibiting an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, especially 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0149] (b) from 10 to 25%, in particular from 14 to 20% of at least one type of flame retardant phosphinate,

[0150] (c) 5 to 15% of at least one functionalized polyolefin,

[0151] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0152] (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive,

[0153] said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0154] In yet another embodiment, said composition comprises by weight:

[0155] (a) from 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide having an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, especially 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0156] (b) 14 to 20% of at least one phosphinate-type flame retardant,

[0157] (c) 5 to 15% of at least one functionalized polyolefin,

[0158] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0159] (e) from 0 to 10%, in particular from 0.1 to 5% of at least one additive,

[0160] said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0161] In yet another embodiment, said composition comprises by weight:

[0162] (a) from 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide having an inherent viscosity of 1.2 to 1.6, in particular 1.2 to 1.5, especially 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass,

[0163] (b) 14 to 20% of at least one phosphinate-type flame retardant,

[0164] (c) of 5 to 15% of at least one functionalized polyolefin,

[0165] (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer,

[0166] (e) of 0.1 to 5% of at least one additive,

[0167] said composition being to the exclusion of PA12 and the sum of constituents (a) to (e) being equal to 100%.

[0168] In all these embodiments, the invention also covers said compositions in which the term "includes" is replaced by the term "consisting of".

[0169] In a first variant of all these embodiments, said composition is devoid of melamine.

[0170] By melamine is meant both melamine and melamine cyanurate or a nitrogenous compound based on melamine.

[0171] It is quite obvious that in this case, the flame retardant cannot be melamine or melamine cyanurate or a nitrogenous compound based on melamine.

[0172] The presence or absence of melamine depends on the processing temperature of the product and in the case of a high temperature, the melamine will be too sensitive to temperature.

[0173] In a second variant of these embodiments, said composition is devoid of PEBA.

[0174] In a third variant of all these embodiments, said composition is devoid of reinforcing fibers.

[0175] In a fourth variant of all these embodiments, said composition is devoid of melamine and PEBA.

[0176] In a fifth variant of all these embodiments, said composition is devoid of melamine and reinforcing fibers.

[0177] In a sixth variant of all these embodiments, said composition is devoid of PEBA and reinforcing fibers.

[0178] In a seventh variant of all these embodiments, said composition is devoid of melamine, PEBA and reinforcing fibers.

[0179] In one embodiment, said composition is intended for a railway application. Regarding PEBA that may be excluded

[0180] Poly ether block amide (PEBA) are copolymers with amide motifs (Bal) and polyether motifs (Ba2), said amide motif (Bal) corresponding to an aliphatic repeating motif selected from a motif obtained from at least one amino acid or a motif obtained from at least one lactam, or an XY motif obtained from polycondensation:

[0181] - of at least one diamine, said diamine being chosen from an aliphatic diamine linear or branched, or an aromatic diamine, or a mixture thereof, and

[0182] - of at least one dicarboxylic acid, said diacid being chosen from a diacid ali- phatic or an aromatic diacid,

[0183] said polyether motifs (Ba2) being in particular derived from at least one polyalkylene ether polyol, in particular a polyalkylene ether diol.

[0184] Regarding reinforcing fibres that may be excluded.

[0185] Reinforcing fibres may in particular be chosen from reinforcing fibres of mineral, organic or vegetable origin.

[0186] Examples of mineral fibers include carbon fibers, glass fibers, basalt fibers or basalt-based fibers, silica fibers, and silicon carbide fibers. Examples of organic fibers include thermoplastic or thermosetting polymer-based fibers, such as semi-aromatic polyamide fibers, aramid fibers, and polyolefin fibers. Examples of plant-based fibers include natural fibers made from flax, hemp, lignin, bamboo, silk (particularly spider silk), sisal, and other cellulosic fibers, especially viscose.

[0187] In one embodiment, said composition after implementation has a limit oxygen level (LOI) > 28.

[0188] According to another aspect, the present invention relates to a tube, in particular partly corrugated, comprising at least one layer made of a composition as defined above.

[0189] Said tube may be single-layer or multi-layer.

[0190] It can be partly smooth or totally smooth.

[0191] A smooth tube is used in particular for the circulation of gas under pressure.

[0192] It can also be partially ringed.

[0193] A corrugated tube is used in particular to serve as a cable conduit.

[0194] The expression "partly corrugated" means that the pipe has a corrugated tubular shape along part of its length. The corrugated portion may form a single section or several sections of the structure, in which case two corrugated sections are separated by a smooth section.

[0195] The annular part(s) allows(s) to increase the deformation and extension capacity of the tubular structure, particularly in areas where small angles are required.

[0196] Advantageously, the tubular structure is corrugated over at least 10% of its length.

[0197] Advantageously, the tubular structure is corrugated over a proportion of 10 to more than 90% of its length.

[0198] Advantageously, the tubular structure is corrugated over a proportion of 20 to 90% of its length.

[0199] Advantageously, the tubular structure is corrugated in a proportion of 30 to more of 90% of its length.

[0200] Advantageously, the tubular structure is corrugated over a proportion of 40 to more than 90% of its length.

[0201] Advantageously, the tubular structure is corrugated over a proportion of 50 to more than 90% of its length.

[0202] Advantageously, the tubular structure is corrugated over a proportion of 60 to more than 90% of its length.

[0203] Advantageously, the tubular structure is corrugated over a proportion of 70 to more than 90% of its length.

[0204] Advantageously, the tubular structure is corrugated over a proportion of 80 to more than 90% of its length.

[0205] Advantageously, the tubular structure is corrugated over a proportion of more than 90% of its length.

[0206] According to yet another aspect, the present invention relates to the use of a composition as defined above, for the manufacture of fireproof articles for railways, in particular for trains.

[0207] Advantageously, said articles are intended for use inside or outside trains.

[0208] In one embodiment, said articles are obtained by extrusion.

[0209] Advantageously, the article obtained by extrusion is a corrugated tube used as a cable conduit or a smooth tube allowing the circulation of fluid under pressure, in particular gas under pressure, especially compressed air.

[0210] According to another aspect, the present invention relates to the use of a composition as defined above, for the protection of a part made entirely or partly of metal.

[0211] Preferably, the invention relates to this use for giving the metal-based material, on which it is applied, electrical insulation and anti-corrosion properties.

[0212] For the purposes of this invention, metal-based material means metallic elements shaped in whole or in part from metal, or plastic or elastic materials comprising metallic fibers.

[0213] Therefore, the use according to the invention aims to impart electrical insulation and anti-corrosion properties to a part comprising a portion comprising metal, said portion of which is coated by said composition.

[0214] These elements can have very diverse forms: of cable, of wire, of a tube, of a container, of a film or of a plate, preferably of a tube.

[0215] According to yet another aspect, the present invention relates to a method for preparing a railway article comprising an extrusion step of a com- position as defined above. EXAMPLES

[0216] The compositions in Table 1 were prepared by molten mixing of the polymer granules with flame retardants, polyolefins, plasticizers, and additives. This mixing was carried out by compounding on a 40 mm diameter co-rotating twin-screw extruder with a flat temperature profile (T°) at 250°C. The screw speed was 300 rpm and the throughput was 70 kg / h.

[0217] The polyamide(s), polyolefins, and additives are introduced during the compounding process in the main hopper. The flame retardant is added to the molten polymer in the middle of the screw via a side feeder. The plasticizer is also introduced into the molten polymer via a pump.

[0218] The compositions were then injected at a temperature of 250°C to obtain the samples to be tested.

[0219] The compositions (samples) of the invention and comparatives were tested with a commonly used flame propagation test called UL94 according to standard NFT 51072 and carried out in test pieces of thickness 0.8 mm.

[0220] The inherent viscosity (IV) was determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass.

[0221] Impact resistance was determined according to ISO 179:leA:2010 (Charpy impact) on bars of

[0222] dimension 80mm x 10mm x 4mm, notched, at a temperature of 23°C + / - 2°C under a relative humidity of 50% + / - 10% and at -30°C + / -2°C under a relative humidity of 50% + / - 10% on dry samples.

[0223] The tensile modulus, elongation and stress at break were measured at 23°C according to ISO 527-1:2012 on a dry sample.

[0224] The machine used is an INSTRON 5966 type. The crosshead speed is 1 mm / min for the

[0225] measurement of the modulus and 5 mm / min for the tensile strength and elongation at break. The

[0226] Test conditions are 23°C + / - 2°C, on dry samples.

[0227] Elongation and stress at break and at 50% strain were measured at 23°C according to ISO 527-1:2012 on a dry sample.

[0228] The machine used is of type INSTRON 5966. The speed of the crosshead is 50 mm / min.

[0229] The test conditions are 23°C + / - 2°C, on dry samples.

[0230] Fatigue resistance is measured by a Ross Flex test on a bar of dimension 150 x 20 x 2 mm without notch. The measurement was taken as follows:

[0231]

[0232]

[0233]

[0234]

[0235]

[0236] Number of cycles: 400,000 Temperature: -10°C Flexing frequency: 100 cycles / min Flexing angle: 60° Conditioning of specimens: 7 days at 70°C After 400,000 cycles, the bars obtained from the formulations of the invention E1 to E6 are not broken, whereas those obtained from the comparative compositions are.

[0237] [Tables 1] Reference El E2 E3 E4 E5 E6 PAU (IV=1.45) 68.8 68.8 65.8 68.8 63.8 68.8 Orevac® IM800 10 12 8 8 4 5 Lotader® AX8900 3 2 2 1 Renol® black AF 34132010-ZA 2 2 2 2 2 2 Anox® TL 91 1.2 1.2 1.2 1.2 1.2 1.2 Exolit® OP1311 15 18 15 15 15 20 BBSA 3 3 6 3 3 3 LOI (%) 29 28 29 29 29 30 Notched impact according to ISO179: leA at 23 °C, resilience (kJ / m2) No breakage No breakage No breakage No breakage No breakage No breakage Notched impact according to ISO 179: leA at -30°C, resilience (kJ / m²) 7 8 6 7 7 6 Ross Flex - Unnotched - 400,000 cycles No breakage No breakage No breakage No breakage No breakage Tensile modulus (MPa) ISO 527-1:2012 1010 870 600 810 1030 1050 Stress at 50% elongation (MPa) 26.7 23.4 23.7 27.0 30.5 31.3 Tensile strength (MPa) 26.9 25.1 27.1 27.9 35.2 33.4 Elongation at break (%) 206 186 188 173 157 152

[0238] [Tables2] Reference IEC CE2 CE3 CE4 PAU (IV=1.45) 68.8 61.8 PAU (IV = 1.1) 68.8 PAU (IV=1.8) 68.8 Orevac® IM800 8 8 8 5 Lotader® AX8900 2 2 2 Renol® black AF 34132010-ZA 2 2 2 2 Anox® TL 91 1.2 1.2 1.2 1.2 Exolit® OP1311 15 15 28 20 BBSA 3 3 6 10 LOI (%) 28 Not extrudable 31 29 Notched impact according to ISO179: leA at 23°C, impact strength (kJ / m2) No breakage No breakage No breakage Notched impact according to ISO179: leA at -30°C, impact strength (kJ / m2) 3 2 3 Ross Flex - Non-Notched - 400,000 cycles break break break

[0239] Orevac® IM800: Maleic anhydride grafted VLDPE (very low density polyethylene) (SK functional polymer).

[0240] Lotader® AX8900: ethylene, methyl acrylate and glycidyl methacrylate copolymer (Et / MA / GMA - 68 / 24 / 8 by weight) (SK functional polymer).

[0241] Renol® black AF 34132010-ZA: black master blend marketed by Clariant.

[0242] Anox® TL 91: antioxidant marketed by SI group.

[0243] Exolit® OP1311 is a Clariant product (aluminum diethyl phosphinate-based flame retardant).

[0244] BBSA (benzyl butyl sulfonamide)

[0245] LOI (limit oxygen level): The EN 45545 standard sets out various specifications for Loads according to the material category. Polyamide pipes correspond to categories R22 and R23, whose fire requirements are as follows (Table 3):

[0246] [Tables3] Requirement Test Method Parameter Unit Min / Ma X HL1 HL2 HL3 R22 Limiting Oxygen Level (LOI) O2 Content (%) Min 28 28 32 Flue Gas Density Ds max Max 600 300 150 CITNP Toxicity Max 1.2 0.9 0.75 R23 Limiting Oxygen Level (LOI) O2 Content (%) Min 28 28 32 Flue Gas Density Ds max Max N / A 600 300 CITNP Toxicity Max N / A 1.8 1.5

[0247] Products are therefore classified according to their oxygen limit index as well as the density and toxicity of the fumes they generate during combustion. Three hazard level classifications (HL1, HL2 or HL3) can be reached depending on their fire properties.

[0248] The higher this classification, the more the polyamide grade can be used in a wide range of train types, whereas a product classified as HL1 cannot be used in an underground metro, for example.

[0249] CIT: Conventional Toxicity Index.

[0250] The examples show the influence of inherent viscosity as well as the influence of the plasticizer range on mechanical criteria and in particular for fatigue resistance and cold shock.

Claims

Demands

1. Flame-retardant composition comprising by weight: (a) from 33 to 83%, in particular from 50 to 78.9%, of at least one semi-crystalline aliphatic polyamide having an inherent viscosity of 1.2 to 1.6, in particular from 1.2 to 1.5, in particular from 1.3 to 1.5, as determined according to ISO 307:2007 but using m-cresol instead of sulfuric acid, a temperature of 20°C and a concentration of 0.5% by mass, (b) from 10 to 25%, in particular from 14 to 20%, of at least one phosphinate-type flame retardant, (c) from 5 to 20%, in particular from 5 to 15%, of at least one functionalized polyolefin, (d) from 2 to 8%, in particular from 2 to 6% of at least one plasticizer, (e) 0 to 10%, in particular 0.1 to 5% of at least one additive, said composition being excluding PA12 and the sum of constituents (a) to (e) being equal to 100%.

2. Composition according to claim 1, characterized in that the semi-crystalline aliphatic polyamide (a) is obtained by polycondensation: of at least one amino acid in the range of C6 to C[8, preferably an amino acid in the range of C9 to C[8, more preferably in the range of C[0 to C[8, in particular in C[0 to Cn, or of at least one lactam in the range of C6 to C[8, preferably an amino acid in the range of C9 to C[8, more preferably in the range of C[0 to C[8, in particular in C[0 to Cn, or of at least one diamine X in the range of C4-C36, preferably C6-C[8, preferably C6-C[2, more preferably C[10-C[2, with at least one dicarboxylic acid Y in the range of C[4-C[36, preferably C[6-C[8, preferably C[6-C[2, more preferably C[10-C[2, with at least one dicarboxylic acid Y in the range of C[4-C[36, preferably C[6-C[8, preferably C[6-C[2, more preferably C[10-C[2, more preferably C[12 ....

3. Composition according to claim 1 or 2, characterized in that the polyamide is a long-chain polyamide having a number of carbons per nitrogen atom greater than or equal to 8, in particular greater than or equal to 9, in particular greater than or equal to 10.

4. Composition according to claim 3, characterized in that said long chain polyamide is selected from PA610, PA612, PA1010, PA1012 and PAU.

5. Composition according to claim 4, characterized in that said at less a semi-crystalline aliphatic polyamide is chosen from PA1010, PA1012 and PAU, in particular PAU.

6. Composition according to any one of claims 1 to 5, 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, a polymer containing at least one metal salt of diphosphinic acid.

7. Composition according to any one of claims 1 to 6, characterized in that the additives are selected from antioxidants, colour pigments and flame retardant synergists, in particular nitrogen synergists, especially melamine-based.

8. Composition according to any one of claims 1 to 7, characterized in that it is devoid of polyether block amides (PEBA).

9. Composition according to any one of claims 1 to 8, characterized in that it is devoid of reinforcing fiber.

10. Tube, in particular partly corrugated, comprising at least one layer made of a composition as defined in any one of claims 1 to 9.

11. Use of a composition as defined in claims 1 to 9, for the manufacture of flame-retardant articles for railways, in particular for trains.

12. Use according to claim 11, characterized in that the articles are intended for use inside or outside trains.

13. Use according to claim 11 or 12, characterized in that the articles are obtained by extrusion.

14. Use according to claim 13, characterized in that the article obtained by extrusion is a corrugated tube used as a cable conduit or a smooth tube allowing the circulation of gas under pressure.

15. Use of a composition as defined in claims 1 to 9, for the protection of a part made entirely or partly of metal.

16. A method for preparing a railway article comprising an extrusion step of a composition as defined in any one of claims 1 to 9.