A composition comprising a thermoplastic polyisocyanate polyaddition product and a flame retardant

Abstract

1. A composition comprising a thermoplastic polyisocyanate polyaddition product and a flame retardant, the composition being essentially free of melamine cyanuric acid, the polyaddition product being obtained by reacting a substance reactive towards isocyanates, a polyisocyanate and a chain extender, finally in the presence of a catalyst, an additive, and the flame retardant comprising a phosphinate.

Description

Technical Field

[0001] The present invention relates to a composition comprising a thermoplastic polyisocyanate polyaddition product and a phosphinate flame retardant.

Background Art

[0002] Thermoplastic polyurethanes having flame retardants are widely described. See, for example, WO2014 / 016406, WO2015 / 128213, WO2017 / 032658 or WO2017 / 032659.

[0003] Extremely specific requirement profiles for extremely specific applications are increasingly being demanded. US8,479,887B2 claims an elevator system in which an extremely specific thermoplastic material is used. Similarly, US8,387,780B2 claims a load-bearing member using a melamine-based adhesion improver.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the requirements for flame retardancy are constantly increasing, and very specific requirement profiles are being created for various applications.

[0006] The problem to be solved by the present invention was to find a thermoplastic polyaddition product having both high flame retardancy and good mechanical properties and suitable for use in high-load flexible assemblies.

[0007] Surprisingly, this problem could be solved by the composition according to claim 1.

Means for Solving the Problem

[0008] A first embodiment of the present invention relates to a composition comprising a thermoplastic polyisocyanate polyaddition product and a flame retardant. The composition does not contain melamine cyanurate, and the polyaddition product is a. a substance reactive with isocyanate b. a polyisocyanate c. a chain extender finally d. a catalyst e. an additive is obtained by reacting in the presence of, The flame retardant contains phosphinate.

Mode for Carrying Out the Invention

[0009] "Not containing melamine cyanurate" means that cyanuric acid is not contained to an extent that provides efficient flame retardant properties. In a preferred embodiment, melamine cyanurate is contained in the composition in less than 5% by mass, preferably less than 3% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, and most preferably less than 0.1% by mass based on the total composition.

[0010] In the second embodiment, in the composition according to Embodiment 1 or a preferred embodiment thereof, the phosphinate is contained at 30% by mass, preferably 5% to 25% by mass, more preferably 5% to 20% by mass, more preferably 5% to 19% by mass, more preferably 5% to 18% by mass, and most preferably 10% to 15% by mass based on the total composition.

[0011] A phosphinate is a salt of phosphinic acid or a phosphinic acid ester, and preferably has the general formula R1R2(P=O)OMe. Me in this formula is a metal, preferably selected from the group consisting of aluminum, calcium, or zinc, and most preferably aluminum.

[0012] In a preferred embodiment, the moieties R1 and R2 are aliphatic or aromatic, and more preferably have 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 3 carbons. It is preferred that at least one of the moieties R1 or R2 is aliphatic, and it is more preferred that both of the moieties R1 and R2 are aliphatic, also called dialkylphosphinates. The aliphatic moieties R1 and R2 are preferably selected from the group consisting of methyl-group, ethyl-group, propyl-group, butyl-group, pentyl-group, hexyl-group, heptyl-group, octyl-group, nonyl-group, and dodecyl-group, or a mixture thereof, more preferably selected from the group consisting of methyl-group, ethyl-group, and propyl-group, and it is highly particularly preferred that R1 and R2 are ethyl-radicals.

[0013] The most preferred phosphinate is aluminum diethylphosphinate.

[0014] The flame retardant is used in the composition in the form of a single substance or a mixture of a plurality of substances, either of the same type of flame retardant or different types of flame retardants. In a preferred embodiment, the content of phosphinate in the total flame retardant is between 50% by mass and 100% by mass, more preferably between 70% by mass and 100% by mass, even more preferably between 90% by mass and 100% by mass, and still even more preferably between 95% by mass and 100% by mass. In another preferred embodiment, the flame retardant preferably consists of phosphinate as outlined above, and most preferably consists of aluminum diethyl phosphinate.

[0015] In a preferred embodiment including any of the embodiments or any features of the preferred embodiments outlined above, the content of the flame retardant in the composition is 5% by mass to 20% by mass, preferably 8% by mass to 15% by mass, based on the total composition.

[0016] In a preferred embodiment, the polyisocyanate polyaddition product is thermoplastic polyurethane (TPU). This is preferably prepared by reacting (a) an isocyanate with (b) an isocyanate-reactive compound also called a polyol (having a number average molecular weight of 0.5×10 3 g / mol to 100×10 3 g / mol in a preferred embodiment) and optionally (c) a chain extender (having a molecular weight of 0.05×10 3 g / mol to 0.499×10 3 g / mol) in the presence of optionally (d) a catalyst and / or (e) conventional auxiliaries and / or additives.

[0017] The thermoplastic polyurethane is preferably in the form of powder or granules.

[0018] The components (a) isocyanate, (b) isocyanate-reactive compound, preferably a polyol in a preferred embodiment, and (c) chain extender are collectively called build-up components, either individually or together. The build-up components, catalyst, and / or normal auxiliaries and / or additives are all collectively called input materials.

[0019] In order to adjust the hardness and melt index of the TPU, the molar ratio of the amounts of the structural components (b) and (c) used can be varied. As a result, as the content of the chain extender (c) increases, the hardness and melt viscosity increase, while the melt index decreases.

[0020] The composition containing the polyisocyanate polyaddition product, preferably a thermoplastic polyurethane, preferably has a hardness of 80 Shore A to 60 Shore D. In a preferred embodiment, the hardness of the composition is between 80 Shore A and 54 Shore D, and very preferably, the hardness is 85 Shore A to 50 Shore D. In one preferred embodiment, the hardness is 85 Shore A, in another preferred embodiment 95 Shore A, and in yet another embodiment 50 Shore D. The Shore hardness is preferably measured in accordance with DIN ISO7619-1.

[0021] In a preferred example, the molar ratio of the polyol (b) to the chain extender (c) is in the range of 1:5.5 to 1:15, preferably 1:6 to 1:12. In other preferred embodiments where the polyurethane polyaddition product preferably has a number average molecular weight of 1.0×10 3 g / mol of polytetrahydrofuran (PTHF) and 1,4-butanediol, the molar ratio of PTHF to 1,4-butanediol is preferably 1:2.5, 1.1:2.2 or 1:1.5.

[0022] To prepare the polyisocyanate polyaddition product, preferably a TPU, the build-up components are reacted in the presence of a catalyst (d) and optionally auxiliaries and / or additives (e) in an amount such that the equivalent ratio of the NCO groups of the diisocyanate (a) to the total of the hydroxyl groups of the components (b) and (c) is 0.95 to 1.10:1, preferably 0.98 to 1.08:1, particularly about 1.0 to 1.05:1.

[0023] The polyisocyanate polyaddition product, preferably a thermoplastic polyurethane, preferably has at least 0.1×10 6g / mol, preferably at least 0.4×10 6 g / mol, and in particular having a mass average molecular weight greater than 0.6×10 6 g / mol. The upper limit of the mass average molecular weight of the TPU is generally determined by the processability and the desired property range. Preferably, the number average molecular weight of the TPU does not exceed 0.8×10 6 g / mol. The above-mentioned average molecular weights of the TPU and the build-up components (a) and (b) are mass average values determined by gel permeation chromatography.

[0024] Preferred organic isocyanates (a) are aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates, more preferably tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methyl-pentamethylene 1,5-diisocyanate, 2-ethyl-butylene-1,4-diisocyanate, 1,5-pentamethylene diisocyanate, 1,4-butylene-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), 1,4-bis(isocyanatomethyl)cyclohexane and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), 2,4-paraphenylene diisocyanate (PPDI), 2,4-tetramethylene xylylene diisocyanate (TMXDI), 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate (H12MDI), 1,6-hexamethylene diisocyanate (HDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and / or -2,6-cyclohexane diisocyanate, 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyl-diphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate, or a mixture thereof.

[0025] Preferred is and / or 2,2’-, 2,4’-, and / or 4,4’-diphenylmethane-diisocyanate (MDI), and particularly preferred is 4,4’-diphenylmethane diisocyanate.

[0026] Polyol The isocyanate-reactive compound (b) has, on statistical average, at least 1.8 and at most 3.0 Zerewitinoff active hydrogen atoms, which number is also called the functionality of the isocyanate-reactive compound (b) and indicates the amount of isocyanate-reactive groups of the molecule calculated theoretically up to 1 molecule from the amount of substance. The functionality is preferably between 1.8 and 2.6, more preferably between 1.9 and 2.2, and particularly 2.

[0027] The compound (b) reactive with isocyanate has a molecular weight between 0.500 g / mol and 8×10 3 g / mol, preferably between 0.7×10 3 g / mol and 6.0×10 3 g / mol, particularly preferably between 0.8×10 3 g / mol and 4.0×10 3 g / mol.

[0028] The isocyanate-reactive compound (b) preferably has a reactive group selected from a hydroxyl group, an amino group, a mercapto group or a carboxylic acid group. The preferred group is a hydroxyl group. These compounds are also called polyols. The polyol (b) is preferably selected from the group consisting of polyester polyols, polyether polyols or polycarbonate diols, more preferably from the group consisting of polyether polyols and polycarbonates. Particularly preferred is a polyether polyol.

[0029] Preferred polyols are polyether polyols, preferably polyether diols, and more preferably those based on ethylene oxide, propylene oxide and / or butylene oxide.

[0030] Another preferred polyether is polytetrahydrofuran (PTHF). In a preferred embodiment, the polytetrahydrofuran has a number average molecular weight between 0.6×10 3 g / mol and 2.5×10 3 g / mol, more preferably between 0.8×10 3 g / mol and 1.4×10 3 g / mol, even more preferably between 0.9×10 3 g / mol and 1.1×10 3 g / mol, and most preferably has a number average molecular weight of 1.0×10 3 g / mol. In another preferred embodiment, the number average molecular weight of PTHF is between 1.6×10 3 g / mol and 2.4×10 3 g / mol, even more preferably between 1.9×10 3 g / mol and 2.1×10 3 g / mol, and most preferably is 2.0×10 3 g / mol.

[0031] The number average molecular weight Mn in the context of the present invention is preferably determined in accordance with DIN 55672-1.

[0032] In another preferred embodiment, the compound (b) reactive with the isocyanate is a polycarbonate diol, preferably an aliphatic polycarbonate diol. Preferred polycarbonate diols are, for example, polycarbonate diols based on alkanediols. Preferred polycarbonate diols are strictly difunctional OH-functional polycarbonate diols, preferably strictly difunctional OH-functional aliphatic polycarbonate diols. Preferred polycarbonate diols are based on butanediol, pentanediol or hexanediol, especially 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentane-(1,5)-diol, or mixtures thereof, and particularly preferred are 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or mixtures thereof. Highly preferred are polycarbonate diols based on 1,4-butanediol and 1,6-hexanediol, polycarbonate diols based on 1,5-pentanediol and 1,6-hexanediol, polycarbonate diols based on 1,6-hexanediol, and mixtures of two or more of these polycarbonate diols.

[0033] Preferably, the polycarbonate diol used has a number average molecular weight Mn in the range of 0.5×10 3 ~4.0×10 3 g / mol, preferably in the range of 0.8×10 3 g / mol to 2.2×10 3 g / mol, particularly preferably in the range of 0.9×10 3 g / mol to 1.1×10 3 g / mol or 1.9×10 3 g / mol to 2.1×10 3 g / mol.

[0034] In a preferred embodiment, the polyol is a mixture of two or more polyols. In a preferred embodiment, the polyol is a mixture of at least one polyether polyol and at least one polycarbonate diol. In other preferred embodiments, the polyol is a single polyol.

[0035] Chain extender In a preferred embodiment, the chain extender (c) is used in the synthesis of polyisocyanate polyaddition products, preferably thermoplastic polyurethanes. The chain extender is preferably an aliphatic, araliphatic, aromatic and / or alicyclic compound with a molecular weight of 0.05×10 3 g / mol to 0.499×10 3 g / mol, and preferably has two groups reactive to isocyanate, also called functional groups. The chain extender can be either a single chain extender or a mixture of at least two chain extenders.

[0036] In a preferred embodiment, the chain extender (c) is preferably at least one chain extender selected from the group consisting of 1,2-ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-dimethanolcyclohexane, neopentyl glycol and hydroquinone bis(β-hydroxyethyl) ether (HQEE). Chain extenders selected from the group consisting of 1,2-ethylene glycol, 1,3-propanediol, 1,4-butanediol and 1,6-hexanediol are particularly preferred. Particularly preferred chain extenders are 1,3-propanediol and 1,4-butanediol. In a preferred embodiment, the chain extender is 1,3-propanediol.

[0037] Catalyst In a preferred embodiment, a catalyst (d) is used together with the build-up component. These are, in particular, catalysts that promote the reaction between the NCO groups of the isocyanate (a) and, preferably, the isocyanate-reactive compound (b) having a hydroxyl group, and, when used, the chain extender (c). Preferred catalysts are tertiary amines, in particular triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)-ethanol, diazabicyclo-(2,2,2)-octane. In another preferred embodiment, the catalyst is an organometallic compound, such as a titanium ester, an iron compound, preferably iron(II) acetylacetonate, a tin compound, preferably one of carboxylic acids, particularly preferably tin diacetate, tin dioctoate, tin dilaurate or tin dialkyl salts, even more preferably dibutyltin diacetate, dibutyltin dilaurate, or a bismuth salt of a carboxylic acid, preferably bismuth decanoate.

[0038] Particularly preferred catalysts are tin dioctoate, bismuth decanoate, titanium esters, or mixtures thereof.

[0039] The catalyst (d) is preferably used in an amount of 0.0001 to 0.1 parts by mass per 100 parts by mass of the composition.

[0040] Auxiliaries In addition to the catalyst (d), conventional auxiliaries (e) can also be added to components (a) to (c). Preferred examples include surfactants, fillers, flame retardants, nucleating agents, oxidation stabilizers, lubricants and mold release aids, dyes and pigments, stabilizers as required, preferably stabilizers against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, reinforcing agents and / or plasticizers.

[0041] A stabilizer in the meaning of the present invention is an additive that protects plastics or plastic mixtures from harmful environmental impacts. Examples include primary and secondary antioxidants, sterically hindered phenols, hindered amine light stabilizers, UV absorbers, hydrolysis inhibitors, quenchers, and flame retardants. Examples of commercially available stabilizers are described in Plastics Additives Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), pp. 98 - S136.

[0042] In a preferred design, the UV absorber has a number average molecular weight greater than 0.3×10 3 g / mol, particularly greater than 0.39×10 3 g / mol. Further, a preferred UV absorber should have a molecular weight not exceeding 5×10 3 g / mol, particularly preferably not exceeding 2×10 3 g / mol.

[0043] As the UV absorber, a group containing cinnamate, oxanilide, and benzotriazole is particularly suitable, and benzotriazole is particularly preferred. Examples of particularly suitable benzotriazoles include Tinuvin® - 213, Tinuvin® - 234, Tinuvin® - 312, Tinuvin® - 571, Tinuvin® - 384, and Eversorb® 82.

[0044] Generally, the UV absorber is added in an amount of 0.01% to 5% by mass, preferably 0.1% to 2.0% by mass, particularly 0.2% to 0.5% by mass based on the total TPU mass.

[0045] UV stabilizers based on antioxidants and UV absorbers as described above are often not sufficient to guarantee good stability of TPU against the harmful effects of ultraviolet light. In this case, in addition to antioxidants and UV absorbers, hindered amine light stabilizers (HALS) can be added to the TPU according to the present invention. The activity of HALS compounds is based on the ability to form nitroxyl radicals that interfere with the oxidation mechanism of the polymer. HALS is considered to be a very efficient UV stabilizer for most polymers.

[0046] HALS compounds are well known and commercially available. Examples of commercially available HALS stabilizers are described in Plastics Additive Handbook, 5th Edition, H. Zweifel, Hanser Publishers, Munich, 2001, pages 123 - 136.

[0047] Particularly preferred hindered amine light stabilizers are bis-(1,2,2,6,6-pentamethylpiperidyl) sebacate (Tinuvin® 765, Ciba Spezialitaetenchemie AG) and the condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid (Tinuvin® 622). In particular, when the titanium content of the final product is less than 150 ppm, preferably less than 50 ppm, and particularly less than 10 ppm based on the components used, the condensate of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid (Tinuvin® 622) is preferred.

[0048] HALS compounds are preferably used at a concentration of 0.01% to 5% by weight, particularly preferably 0.1% to 1% by weight, and particularly 0.15% to 0.3% by weight based on the total weight of the thermoplastic polyurethane based on the composition components used.

[0049] Particularly preferred UV stabilizers contain a mixture of phenolic stabilizers, benzotriazoles and HALS compounds in the preferred amounts described above.

[0050] Further information regarding the above auxiliaries and additives can be found in technical literature, for example, Plastics Additives Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001.

[0051] In another preferred embodiment, the composition comprises a filler chemically bonded to at least a portion of the composition. Preferably, the filler comprises polyhedral oligomeric silsesquioxane. In another embodiment, the filler is carbon, preferably carbon nanotubes or carbon fibers. The filler preferably has an extension of less than 1 × 10 -6 meters, preferably less than 0.5 × 10 -6 meters, more preferably less than 1 × 10 -7 meters, 0.5 × 10 -7 meters, less than 1 × 10 -8 meters, 0.5 × 10 -8 meters, most preferably less than 1 × 10 -9 meters.

[0052] Manufacture Polyisocyanate polyaddition products, preferably thermoplastic polyurethanes, can be manufactured discontinuously or continuously by known processes, for example, using a reaction extruder, using a belt process, and applying the "one-shot" method or the prepolymer method, preferably the "one-shot" method. In the "one-shot" method, the components (a), (b), and finally the chain extender (c) to be reacted are mixed with each other. This is done continuously or simultaneously, preferably in the presence of a catalyst (d) and / or an auxiliary (e) in a preferred embodiment. In an extruder process, the structural components (a), (b), finally the chain extender (c), and the catalyst (d) and / or the auxiliary (e) in a preferred form are mixed. The mixing is preferably carried out at a temperature between 100 °C and 280 °C, preferably between 140 °C and 250 °C. The resulting polyurethane is preferably in the form of granules or powder.

[0053] The auxiliary agent of one embodiment is added during the synthesis of polyisocyanate polyaddition products, preferably thermoplastic polyurethanes. In another preferred embodiment, the auxiliary agent (e) is added to the polyisocyanate polyaddition product, preferably thermoplastic polyurethane, after its synthesis, preferably in an extruder.

[0054] A mixture comprising a polyisocyanate polyaddition product, preferably a thermoplastic polyurethane, finally at least one auxiliary agent, and in a preferred embodiment further polymers, is also called a composition.

[0055] A twin-screw extruder is preferred. This is because a twin-screw extruder operates with positive conveying, so that the temperature and the output can be set more precisely in the extruder.

[0056] Use The composition is preferably used for the production of articles by injection molding, calendering, powder sintering, or extrusion. The composition in a preferred embodiment is injection molded, calendered, powder sintered, or extruded to form an article.

[0057] Still another aspect of the present invention is an article produced using the composition or obtained by the method described above.

[0058] In a preferred embodiment, the article is selected from the group consisting of a coating, a damping element, a bellows, a foil, a fiber, a shaped body, a roofing or flooring material for buildings and transportation, a nonwoven fabric, preferably a gasket, a roll, a shoe sole, a hose, a cable, a cable connector, a cable sheath, a pillow, a laminate, a profile, a strap, a saddle, a foam by additional foaming of a composition, a plug connection, a trailing cable, a solar cell module, an automobile lining, a wiper blade, a load support member of an elevator, a roping arrangement, a drive belt of a machine, a passenger conveyor, a handrail of a passenger conveyor, a modifier for a thermoplastic material, or a mixture thereof. A modifier means a substance that affects the properties of another material and is preferably in the form of a powder or granules.

[0059] Another aspect of the present invention is the composition or foam beads made in its preferred embodiments. These foam beads, and shaped bodies made therefrom, may be used in various applications (see, for example, WO94 / 20568, WO2007 / 082838A1, WO2017030835, WO2013 / 153190A1, WO2010010010, which are incorporated herein by reference).

[0060] In a highly preferred embodiment, this composition is used in a flexible load-bearing assembly, preferably a load-bearing assembly of an elevator, a roping arrangement, a drive belt for a machine, a passenger conveyor, preferably a handrail of a passenger conveyor. Such an assembly includes at least one cord, and in other preferred embodiments at least two cords, which are partially or completely covered by the composition of the present invention.

Examples

[0061] Example 1 The following table lists compositions in which the individual components are listed by mass ratio (GT). The compounds were each produced using a ZE40A twin-screw extruder type from Berstorff with a 35D processing section length divided into 10 housings. Pelletization was carried out using a standard underwater pelletizer (UWG) from Gala.

[0062] The compound was extruded into a 1.6 mm thick film using a single-screw extruder type Arenz with a 3-zone screw (screw ratio 1:3) equipped with a mixing section. The density, Shore hardness, tensile strength, tear propagation strength, abrasion resistance and elongation at break of the test specimens were measured. The results are summarized in the following table.

[0063] Example 2 TPU1 with a Shore hardness of 90A is based on polytetrahydrofuran polyol (PTHF) with a number average molecular weight of 1000 g / mol, 1,4-butanediol and 4,4'-diisocyanatodicyclohexylmethane and is commercially available from BASF Polyurethanes GmbH, Germany, as Elastollan® 1190A10.

[0064] TPU2 with a Shore hardness of 48D is based on polytetrahydrofuran polyol (PTHF) with a number average molecular weight of 1000 g / mol, 1,3-propanediol and 4,4'-diisocyanatodicyclohexylmethane and is commercially available from BASF Polyurethanes GmbH, Germany, as Ellastollan® 1598A10.

[0065] Aluminum diethylphosphinate (ADP), CAS number: 225789-38-8, water content less than 0.2 mass%, average particle diameter (D50) 20 - 40 μm, commercially available from Clariant Produkte GmbH, Germany, as Exolit® OP1230.

[0066] Example 3 Table 1 This table shows the composition of the materials and their respective mechanical properties.

[0067]

Table 1

[0068] Example 4 Test pieces for cone measurement with dimensions of 200×150×5 mm were injection-molded using an Arburg 520S with a screw diameter of 30 mm. Next, these plates were cut into the size required for cone measurement (100×100×5 mm).

[0069] To evaluate the flame retardancy, in accordance with ISO 5660 Part 1 and Part 2 (2002-12), a sample with a thickness of 5 mm was horizontally tested with a cone calorimeter at a radiation intensity of 35 kW / m 2 .

[0070] The results are summarized in Table 2. In mixture B, the total heat release (THE) and the peak of heat release (PHR) decreased significantly compared to mixture A.

[0071]

Table 2

Claims

1. A composition comprising a thermoplastic polyurethane and a flame retardant, wherein the composition does not contain melamine cyanurate, and the thermoplastic polyurethane is obtained by reacting, finally, a. a substance reactive with isocyanate b. a polyisocyanate c. a chain extender containing 1,3-propanediol in the presence of d. a catalyst e. an additive and the flame retardant contains a phosphinate, wherein the phosphinate is contained in the composition in an amount of 5 to 30% by mass based on the total composition.

2. The composition according to claim 1, wherein the flame retardant is a phosphinate.

3. The composition according to claim 1 or 2, wherein the phosphinate is aluminum phosphinate.

4. The composition according to claim 1 or 2, wherein the phosphinate is aluminum dialkyl-phosphinate.

5. The composition according to claim 4, wherein the alkyl of the phosphinate is independently selected from the group consisting of methyl-, ethyl-, propyl, butyl-, pentyl-, hexyl-, heptyl-, octyl-, nonyl-, and dodecyl-.

6. The composition according to claim 1 or 2, wherein the phosphinate is aluminum diethyl phosphinate.

7. The composition according to any one of claims 1 to 6, wherein the polyisocyanate is diphenylmethane-4,4'-diisocyanate.

8. The composition according to any one of claims 1 to 7, wherein the phosphinate is the only flame retardant in the composition.

9. The composition according to any one of claims 1 to 8, wherein the substance reactive with isocyanate is a polyether diol.

10. The composition according to claim 9, wherein the polyether diol is polytetrahydrofuran or polycarbonate diol.

11. A method of using the composition according to any one of claims 1 to 10 in an elevator system.

12. A method of forming an article by injection molding, calendering, powder sintering, or extrusion of the composition according to any one of claims 1 to 10.

13. An article comprising the composition according to any one of claims 1 to 10 or obtained by the method according to claim 12. ​

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