Flame-retardant thermoplastic polyurethane composition

Abstract

Disclosed is a thermoplastic polyurethane composition comprising 84 wt% to 97 wt% of a thermoplastic polyurethane and 3 wt% to 16 wt% of a flame retardant, based on the total weight of the thermoplastic polyurethane composition, where the flame retardant comprises an ionic liquid and a phosphorus-containing ester. Articles produced from the thermoplastic polyurethane composition and uses thereof are also provided.

Description

Technical Field

[0001] The present disclosure relates to flame retardant thermoplastic polyurethane compositions, articles produced therefrom, and uses of the articles. Background Art

[0002] Thermoplastic polyurethanes (TPU) are suitable for many applications, such as wires, cables, pipes, etc. Since TPU itself is flammable, flame retardant TPU is highly desirable in applications such as aircraft, electric vehicles, appliances, buildings, and construction.

[0003] Conventional flame retardant TPUs are usually doped with nitrogen or phosphorus-based flame retardants, such as melamine cyanurate, ammonium polyphosphate, aluminum hypophosphite, diphenyl cresyl phosphate. One of the problems with these flame retardants is that the improvement in flame retardancy is poor. In order to achieve UL 94V0 rating, about 20% to 30% by weight of flame retardant is required. Such a high amount will affect the compatibility and mechanical strength of the TPU composition. In addition, the large amount of flame retardants also increases production costs.

[0004] Ionic liquids have been reported as flame retardants. However, they also degrade the mechanical properties of the TPU matrix.

[0005] CN111909503A describes a thermoplastic polyurethane composition containing 3% by weight of tributylmethylammonium tributyl phosphate. The tensile strength of the polyether and polyester polyurethanes decreased by 20% and 30%, respectively.

[0006] US20150353832A1 teaches the use of phosphinate ionic liquids as flame retardants and simultaneously as melt viscosity reducers for polymer processing.

[0007] CN105440652A discloses a flame retardant thermoplastic polyurethane elastomer with an intumescent flame retardant and an ionic liquid. The ionic liquid is preferably a dialkyl imidazolium ionic liquid, such as 1-ethyl-3-methyl imidazolium hexafluorophosphate. The intumescent flame retardant comprises aluminum hypophosphite, ammonium polyphosphate, diethyl aluminum hypophosphite, and the like.

[0008] Nevertheless, flame retardant thermoplastic polyurethane compositions having low flame retardant dosage and good mechanical strength are still desired. Summary of the invention

[0009] One object of the present disclosure is to overcome the problems of the prior art discussed above and to provide a flame retardant thermoplastic polyurethane composition that requires a small amount of added flame retardant while maintaining physical properties such as tensile strength, abrasion loss, elongation at break, etc.

[0010] Surprisingly, the present inventors have found that the above objects can be achieved by a thermoplastic polyurethane composition comprising 84 wt % to 97 wt % of a thermoplastic polyurethane and 3 wt % to 16 wt % of a flame retardant, based on the total weight of the thermoplastic polyurethane composition, wherein the flame retardant comprises an ionic liquid and a phosphorus-containing ester.

[0011] According to another aspect of the present disclosure, an article is provided, the article being produced from the thermoplastic polyurethane composition.

[0012] Further aspects of the present disclosure provide uses of the article.

[0013] It has surprisingly been found in the present application that by incorporating phosphorus-containing esters and ionic liquids into thermoplastic polyurethane compositions, the polyurethane compositions exhibit good flame retardancy and at the same time good mechanical properties. DETAILED DESCRIPTION

[0014] Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by those skilled in the art to which the present disclosure belongs. As used herein, unless otherwise indicated, the following terms have the meanings assigned to them below.

[0015] As used herein, the articles "a" and "an" refer to one or to more than one (ie, to at least one) of the grammatical object of the article. For example, "an element" means one element or more than one element.

[0016] Unless otherwise indicated, all percentages (%) are by weight.

[0017] Here, the phosphorus-containing ester refers to a class of organic phosphorus compounds, including organic phosphates, organic phosphonates or organic phosphinates.

[0018] Organic phosphates are a class of organic phosphorus compounds with the general structure O═P(OH)2(OR), O═P(OH)(OR)2, O═P(OR)3, where R is an alkyl group or an aryl group, with a central phosphate ester molecule having alkyl or aromatic substituents. Exemplary organic phosphates include triethyl phosphate, triphenyl phosphate.

[0019] Organic phosphonates are organic phosphorus compounds containing C—PO(OH)2, C—PO(OH)(OR) or C—PO(OR)2 groups, wherein R is an alkyl group or an aryl group.

[0020] Organic phosphinates are organophosphorus compounds containing the following groups:

[0021]

[0022] wherein R is an alkyl or aryl group.

[0023] Unless indicated otherwise, temperature refers to room temperature and pressure refers to ambient pressure.

[0024] Unless otherwise stated, the term ionic liquid refers to salts having a melting point below 100°C.

[0025] According to the present disclosure, a thermoplastic polyurethane composition is provided. Based on the total weight of the thermoplastic polyurethane composition, the thermoplastic polyurethane composition comprises:

[0026] 84% to 97% by weight of thermoplastic polyurethane, and

[0027] 3 wt% - 16 wt% of flame retardant,

[0028] The flame retardant comprises ionic liquid and phosphorus-containing ester.

[0029] Preferably, according to the procedure of Underwriters Laboratories Bulletin 94 entitled "Tests for Flammability of Plastic Materials, UL94", a sheet having a thickness of 2 mm prepared from the thermoplastic polyurethane composition achieves UL94 V0 rating.

[0030] Flame retardants

[0031] The flame retardant according to the present disclosure comprises an ionic liquid and a phosphorus-containing ester. It has been found that the use of an ionic liquid and a phosphorus-containing ester simultaneously can enhance flame retardancy and thus reduce the total amount of flame retardant required. Due to the reduction in the amount of flame retardant, the deterioration of the mechanical properties of the thermoplastic polyurethane composition can be alleviated.

[0032] Preferably, the ionic liquid is a phosphorus-based ionic liquid. More preferably, the ionic liquid has the formula:

[0033]

[0034] Among them, M + represents a monovalent cation selected from the group consisting of ammonium, quaternary ammonium, imidazolium, guanidinium, pyridinium, pyridazinium, 1,2,4-triazolium, triazine, sulfonium, phosphazenium and phosphonium cations. Preferably, M + More preferably, M + represents a quaternary alkylphosphonium or a quaternary arylphosphonium.

[0035] R1 and R2 are each independently selected from hydrogen, hydroxy, C1-C18 alkyl, aryl, C1-C18 alkoxy, aryl, (C3-C10) heterocyclyl, (C3-C10) cycloalkyl, (C3-C10) heterocyclyl(C1-C8) alkyl, aryl(C1-C8) alkyl, heteroaryl and heteroaryl(C1-C8) alkyl groups, each of which is unsubstituted or substituted with one or two halogen atoms, -NO2, -CF3, -OCF3, -OCH3, -CO2H, -NH2, -OH, -SH, -NHCH3, -N(CH3)2, -CN, -SCH3, -SO3H, -CH═CH—CH2—CH═CH2, -P((C1-C5) alkyl)2 and -P(O)(OEt)2 or a mixture of substituents.

[0036] Preferably, the ionic liquid has a weight percentage of 0.2 wt% to 2.8 wt%, preferably 0.3 wt% to 1.5 wt%, more preferably 0.5 wt% to 1.0 wt%, based on the total weight of the thermoplastic polyurethane composition.

[0037] Phosphorus-containing esters include one or more organic phosphates, organic phosphonates, and organic phosphinates. Phosphorus-containing esters preferably include one or more selected from trialkyl phosphates, triaryl phosphates, halogenated phosphates, and organic phosphonates. More preferably, phosphorus-containing esters include one or more selected from the following items: resorcinol bis(diphenyl phosphate) (abbreviated as "RDP"), bisphenol A bis(diphenyl phosphate) (abbreviated as "BDP"), tolyl diphenyl phosphate (abbreviated as "CDP"), monomer resorcinol dixylyl phosphate, polymerized resorcinol dixylyl phosphate, tricresyl phosphate, triethyl phosphate (TEP), tricresyl phosphate, triphenyl phosphate, tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP), dimethyl methylphosphonate (DMMP) and dimethyl propanephosphonate (DMPP).

[0038] Preferably, the phosphorus-containing ester has a weight percentage of 1 wt% to 18 wt%, more preferably 2 wt% to 15 wt%, still more preferably 3 wt% to 10 wt%, based on the total weight of the thermoplastic polyurethane composition.

[0039] The weight ratio of the ionic liquid to the phosphorus-containing ester is preferably 1:100-1:0.7, preferably 1:50-1:2, more preferably 1:20-1:5. At the preferred weight ratio, the total amount of the two flame retardants can be reduced, while the mechanical strength and other properties can be maintained or even improved.

[0040] In addition to ionic liquids and phosphorus-containing esters, halogenated compounds, for example, halogenated polyols, and solids such as diethylaluminum hypophosphite, aluminum hypophosphite, aluminum trihydroxide, ammonium polyphosphate (APP), red phosphorus, expanded graphite and melamine are suitable as auxiliary flame retardants.

[0041] The flame retardant can be added to the thermoplastic polyurethane during or after synthesis by an extruder, mixer, grinder, etc. in liquid, masterbatch pellets or powder form (if any powdered flame retardant is used as an auxiliary flame retardant).

[0042] The ionic liquid and the phosphorus-containing ester can be added to the thermoplastic polyurethane composition simultaneously or separately. The ionic liquid can be premixed with the phosphorus-containing ester to form a flame retardant mixture.

[0043] Thermoplastic polyurethane

[0044] In order to prepare a thermoplastic polyurethane composition, a thermoplastic polyurethane is required, which is prepared in the form of pellets in advance or synthesized in situ. For example, the polyurethane can be synthesized by reacting a polyol component and an isocyanate component. In various embodiments, the polyol component comprises,

[0045] Polyether polyols, polyester polyols or mixtures thereof; and

[0046] One or more chain extenders.

[0047] The isocyanate component may include one or more selected from the group consisting of a monomeric, oligomeric or polymeric isocyanate, a prepolymer of an isocyanate and an active hydrogen-containing compound terminated with an isocyanate group, or a polymeric alkyl or aryl isocyanate.

[0048] Preferably, the thermoplastic polyurethane has a weight average molecular weight in the range of 50,000 Da to 500,000 Da.

[0049] Preferably, the thermoplastic polyurethane composition has a hardness of Shore 40A to Shore 80D, preferably Shore 50A to Shore 98A, as determined according to DIN ISO 48-4.

[0050] Polyol components

[0051] The polyol component comprises polyether polyol, polyester polyol or a mixture thereof and one or more chain extenders.

[0052] Polyether polyols and polyester polyols are collectively referred to as polyols. Polyols refer to polyhydroxy compounds. Preferably, polyhydroxy compounds having a functionality of 1.9 to 2.1 and a hydroxyl value of 30 mg KOH / g to 200 mg KOH / g are examples of higher molecular weight compounds having at least two reactive hydrogen atoms.

[0053] Suitable polyester polyols can be produced, for example, by organic dicarboxylic acids with 2 to 12 carbons, preferably aliphatic dicarboxylic acids with 4 to 6 carbons, and polyvalent alcohols with 2 to 12 carbons, preferably 2 to 6 carbons, preferably glycols. The example of dicarboxylic acids includes succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. Dicarboxylic acids can be used individually or in mixtures. Instead of free dicarboxylic acids, corresponding dicarboxylic acid derivatives can also be used, such as dicarboxylic acid monoesters or diesters or dicarboxylic acid anhydrides with alcohols having 1 to 4 carbons. The dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid in the amount ratio of 20-35:35-50:20-32 weight portions are preferred, especially adipic acid. Examples of divalent and polyvalent alcohols, especially diols, include ethylene glycol, diethylene glycol, 1,2- and 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, glycerol and trimethylolpropane. Ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or a mixture of at least two of these diols is preferred, especially ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

[0054] Polyester polyols can be produced by polycondensation of an organic polycarboxylic acid (e.g., an aromatic or preferably aliphatic polycarboxylic acid and / or its derivatives) with a polyvalent alcohol in the presence of a catalyst or preferably in the presence of an esterification catalyst, preferably in an atmosphere of an inert gas (e.g., nitrogen, carbon dioxide, helium, argon, etc.), in a melt at a temperature of 150° C. to 250° C., preferably 180° C. to 220° C., optionally under reduced pressure until the desired degree of polymerization (which is preferably less than 20, especially less than 15). In a preferred embodiment, the esterification mixture is polycondensed at atmospheric pressure and subsequently at a pressure of less than 500 mbar, preferably 50 mbar to 150 mbar at the above temperature to an acid value of less than 1 mg KOH / g. Examples of suitable esterification catalysts include iron catalysts, cadmium catalysts, cobalt catalysts, lead catalysts, zinc catalysts, antimony catalysts, magnesium catalysts, titanium catalysts and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of diluents and / or entrainers, such as benzene, toluene, xylene or chlorobenzene, in order to effect azeotropic distillation of the condensed water.

[0055] To produce the polyester polyol, the organic polycarboxylic acid and / or its derivative is preferably polycondensed with a polyvalent alcohol in a molar ratio of 1:1-1.8, preferably 1:1.05-1.2.

[0056] The resulting polyester polyols preferably have a functionality of 1.9 to 2.1 and a hydroxyl number of 30 to 200 mg KOH / g.

[0057] Polyether polyols obtainable by known methods can also be used as polyols. For example, polyether polyols can be produced by anionic polymerization using an alkali metal hydroxide (such as sodium hydroxide or potassium hydroxide) or an alkali metal alkoxide (such as sodium methoxide, sodium ethoxide or potassium ethoxide or potassium isopropoxide) as a catalyst and adding at least one initiator molecule containing 2 to 8, preferably 3 to 8 reactive hydrogens, or by cationic polymerization of one or more alkylene oxides having 2 to 4 carbons in the alkylene radical using a Lewis acid (such as antimony pentachloride, boron trifluoride etherate, etc.) or bleaching earth as a catalyst.

[0058] Suitable cyclic ethers and alkylene oxides include, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene cyclic ethers and oxides can be used individually, alternately, one after the other or as a mixture. Examples of suitable initiator molecules include: water, organic dicarboxylic acids (such as succinic acid, adipic acid, phthalic acid and terephthalic acid), aliphatic and aromatic (optionally N-monosubstituted, N,N-dialkyl substituted and N,N'-dialkyl substituted) diamines with 1 to 4 carbons in the alkyl radical, such as optionally monosubstituted and dialkyl substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- and 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexanediamine, phenylenediamine, 2,3-, 2,4- and 2,6-toluenediamine and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane.

[0059] Suitable initiator molecules also include alkanolamines such as ethanolamine, diethanolamine, N-methyl and N-ethylethanolamine, N-methyl and N-ethyldiethanolamine, and triethanolamine plus ammonia.

[0060] Preferred are divalent alcohols such as ethylene glycol, 1,2-propylene glycol and 1,3-propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butylene glycol and 1,6-hexanediol.

[0061] The polyether polyol has a functionality of preferably 1.9 to 2.1 and a hydroxyl value of 30 to 200 mg KOH / g.

[0062] Similar to polyester polyols, polyether polyols can be used alone or in the form of a mixture. In addition, they can be mixed with polyester polyols and polycarbonates and / or polycaprolactones.

[0063] Suitable polycarbonates containing hydroxyl groups include those of known type, such as those obtained by reaction of a diol (eg 1,3-propylene glycol, 1,4-butanediol and / or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol) with a diaryl carbonate (eg diphenyl carbonate) or phosgene.

[0064] Chain Extender

[0065] Thermoplastic polyurethanes are prepared using chain extenders. Suitable chain extenders preferably include glycols. Typical examples are aliphatic, alicyclic and / or aromatic aliphatic glycols having 2 to 14, more preferably 4 to 10 carbon atoms, such as ethylene glycol, 1,3-propylene glycol, 1,10-decanediol, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, preferably 1,4-butanediol, 1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone.

[0066] Other additives and auxiliaries

[0067] Optionally, other additives and / or adjuvants may be incorporated into the thermoplastic polyurethane composition. Examples include antioxidants, UV stabilizers, lubricants, matting agents, nucleating agents, plasticizers, catalysts, crosslinking agents, fillers, dyes, pigments, hydrolysis inhibitors, fungistatic agents and bacteriostatic agents. The type and / or amount of additives and adjuvants may be determined based on the specific application in which the thermoplastic polyurethane composition is used.

[0068] Isocyanate component

[0069] The isocyanate component in the present disclosure comprises one or more selected from the group consisting of aliphatic isocyanates, alicyclic isocyanates, araliphatic isocyanates and aromatic isocyanates. For example, the isocyanate component may comprise an alkylene diisocyanate having 4 to 12 carbons in the alkylene radical, such as 1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1,4-tetramethylene diisocyanate and preferably 1,6-hexamethylene diisocyanate; alicyclic diisocyanates, such as 1,3- and 1,4-cyclohexane diisocyanate and any mixture of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate) The organic diisocyanates and polyisocyanates are preferably selected from the group consisting of 2,4- and 2,6-toluene diisocyanate and corresponding isomer mixtures, 4,4', 2,2' and 2,4'-dicyclohexylmethane diisocyanate and corresponding isomer mixtures, and preferably aromatic diisocyanates and polyisocyanates, such as 2,4- and 2,6-toluene diisocyanate and corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and corresponding isomer mixtures, 4,4'- and 2,4'-diphenylmethane diisocyanate and mixtures of polymeric MDI and toluene diisocyanate. The organic diisocyanates and polyisocyanates can be used individually or in the form of a mixture.

[0070] preparation

[0071] The preparation of thermoplastic polyurethanes has been described elsewhere but essentially involves the reaction of a polyol and a chain extender with an isocyanate, optionally in the presence of a catalyst.

[0072] The preparation of the thermoplastic polyurethane can be carried out batchwise or continuously by known methods, for example using a reaction extruder or by a belt process or a prepolymer process in a one-step process, preferably by a one-step process.

[0073] Processing

[0074] The thermoplastic polyurethane composition can be processed by conventional methods, including injection molding, compression molding, extrusion, coextrusion, thermoforming casting, sintering, vacuum forming, extrusion, coextrusion, fused deposition modeling, fused filament fabrication, selective laser sintering, selective laser melting, powder bed fusion, sheet lamination, material extrusion, and the like.

[0075] The thermoplastic polyurethane composition may be in the form of a powder, flakes, rods, sheets or blocks, or alternatively may be in the form of pellets or granules by, for example, strand cutting or underwater cutting.

[0076] application

[0077] Various articles can be produced from the thermoplastic polyurethane composition according to the present disclosure. The articles include, among others, artificial leather, films, sheets, molded articles, fibers, automotive interiors, tubes, hoses, profiles, pipes, cable connectors, guy wires, cable sheaths, wires, optical components, electronic components, electrical components, seals, nonwovens, belts, or damping elements.

[0078] These products can be applied to electric vehicles or charging devices for electric vehicles, household appliances, residential or office furniture, buildings, optical devices, electronic devices, electrical devices, etc.

[0079] Example

[0080] Measurement and test methods

[0081] The measurement and test methods are shown in Table 1.

[0082] Table 1 Measurement and test standards

[0083] nature unit Test Standards Shore hardness A DIN ISO 48-4 Tensile strength MPa DIN 53504 Fracture length ％ DIN 53504 Tear strength (trouser shape) kN / m DIN ISO 34-1, (A) Tear strength (angle) kN / m DIN ISO 34-1, B(b) Wear loss <![CDATA[mm 3 ]]> DIN ISO 4649 Flame retardant / UL94V, 2mm Dielectric strength kV / mm ASTM D149 Volume resistivity Ω·cm IEC 62631-3-1:2016 Surface resistance Ω IEC 62631-3-2:2015

[0084] Material

[0085] In the examples shown in Tables 2 and 3, the following materials were used.

[0086] 1190A, a polyether-based aromatic TPU from BASF Polyurethanes GmbH, tensile strength 50 MPa; tear strength (angle), 89 kN / m; abrasion loss, 40 mm 3 .

[0087] CDP and RDP, from Zhejiang Wansheng Co., Ltd.

[0088] IL-1, an ionic liquid based on quaternary phosphonium cations and organophosphate anions, is used as a flame retardant.

[0089] Butanediol from BASF was used as a chain extender for the synthesis of the thermoplastic polyurethanes of the examples in Table 3.

[0090] Poly(tetramethylene oxide) from BASF with a functionality of 2 and a hydroxyl value of 112.2 mgKOH / g was used as the polyol for the synthesis of the thermoplastic polyurethanes of the examples in Table 3.

[0091] From BASF MS, mainly 4,4′-MDI, was used as the isocyanate for synthesizing the thermoplastic polyurethanes of the examples in Table 3.

[0092] Matting agent based on polystyrene.

[0093] Antioxidant 1010, a sterically hindered phenol from BASF.

[0094] To prepare the flame retardant thermoplastic polyurethane composition, two flame retardants are added to the thermoplastic polyurethane separately. The ionic liquid and the phosphorus-containing ester are added to the thermoplastic polyurethane separately, and then the ionic liquid and the phosphorus-containing ester are evenly dispersed. The mixture is heated at 80°C for several hours until the liquid is evenly dissolved in the matrix of the thermoplastic polyurethane.

[0095] The obtained flame retardant thermoplastic polyurethane composition was molded into a test sheet having a thickness of 2 mm by injection molding to conduct mechanical property and flame retardancy tests.

[0096] Table 2 shows examples of flame retardancy at the UL94V0 level, and Table 3 shows examples of the UL94V2 level.

[0097] Table 2 Properties of thermoplastic polyurethane compositions

[0098]

[0099] According to Table 2, compared with the TPU composition with only phosphorus-containing ester as a flame retardant, the TPU composition with both ionic liquid and phosphorus-containing ester as a co-flame retardant can achieve the same level of flame retardancy at a much lower dosage. In order to achieve approximately the same level of flame retardancy, the TPU composition with both ionic liquid and phosphorus-containing ester shows improvements in mechanical properties, especially tear strength and abrasion loss. Abrasion loss and tear strength are very important for products such as cable sheaths, wires, hoses, pipes, belts, etc. Based on the total weight of the thermoplastic polyurethane composition, in order to achieve good mechanical properties, the weight percentage of the ionic liquid is preferably 0.2 wt%-2.8 wt%, 0.3 wt%-1.5 wt%, and more preferably 0.5 wt%-1.0 wt%. Compared with the original thermoplastic polyurethane Compared with 1190A, the flame retardant thermoplastic polyurethane with ionic liquid and phosphorus-containing ester has less deterioration in tensile strength, tear strength and abrasion loss.

[0100] Table 3 Properties of thermoplastic polyurethane compositions

[0101]

[0102] The TPU in Table 3 was synthesized by an extruder. The isocyanate index calculated as the ratio of the number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the chain extender and the polyol was about 1. During the synthesis of the thermoplastic polyurethane, a flame retardant, a matting agent and an antioxidant were added to the thermoplastic polyurethane.

[0103] According to Table 3, it can be found that the TPU composition with both ionic liquid and phosphorus-containing ester as co-flame retardant can achieve the same level of flame retardancy with much lower dosage and in the presence of other additives. In terms of mechanical strength, elongation at break and abrasion loss, the thermoplastic polyurethane samples with ionic liquid and phosphorus-containing ester are superior to those samples containing only phosphorus-containing ester as flame retardant.

Claims

1. A thermoplastic polyurethane composition, based on the total weight of the thermoplastic polyurethane composition, comprising: 84% to 97% by weight of thermoplastic polyurethane, and 3 wt% - 16 wt% of flame retardant, The flame retardant comprises an ionic liquid and a phosphorus-containing ester.

2. The thermoplastic polyurethane composition of claim 1, wherein the ionic liquid is a phosphorus-based ionic liquid.

3. The thermoplastic polyurethane composition of claim 2, wherein the ionic liquid has the formula: M + represents a monovalent cation selected from the group consisting of ammonium, quaternary ammonium, imidazolium, guanidinium, pyridinium, pyridazinium, 1,2,4-triazolium, triazine, sulfonium, phosphazenium, and phosphonium cations; and R1 and R2 are each independently selected from hydrogen, hydroxy, C1-C18 alkyl, aryl, C1-C18 alkoxy, aryl, (C3-C10) heterocyclyl, (C3-C10) cycloalkyl, (C3-C10) heterocyclyl(C1-C8) alkyl, aryl(C1-C8) alkyl, heteroaryl and heteroaryl(C1-C8) alkyl groups, each of which is unsubstituted or substituted with one or two halogen atoms, -NO2, -CF3, -OCF3, -OCH3, -CO2H, -NH2, -OH, -SH, -NHCH3, -N(CH3)2, -CN, -SCH3, -SO3H, -CH═CH—CH—CH═CH2, -P((C1-C5) alkyl)2 and -P(O)(OEt)2 or a mixture of substituents.

4. The thermoplastic polyurethane composition according to claim 3, wherein M + represents a phosphonium cation.

5. The thermoplastic polyurethane composition according to claim 1, wherein the ionic liquid has a weight percentage of 0.2 wt%-2.8 wt%, preferably 0.3 wt%-1.5 wt%, more preferably 0.5 wt%-1.0 wt%, based on the total weight of the thermoplastic polyurethane composition.

6. The thermoplastic polyurethane composition of claim 1, wherein the phosphorus-containing ester comprises one or more selected from the group consisting of resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), cresyl diphenyl phosphate, monomeric resorcinol dixylyl phosphate, polymeric resorcinol dixylyl phosphate, tricresyl phosphate, triethyl phosphate, tricresyl phosphate, and triphenyl phosphate.

7. The thermoplastic polyurethane composition according to claim 1, wherein the phosphorus-containing ester has a weight percentage of 1 wt%-18 wt%, preferably 2 wt%-15 wt%, more preferably 3 wt%-10 wt%, based on the total weight of the thermoplastic polyurethane composition.

8. The thermoplastic polyurethane composition according to claim 1, wherein the weight ratio of the ionic liquid to the phosphorus-containing ester is 1:100-1:0.7, preferably 1:50-1:2, more preferably 1:20-1:

5.

9. The thermoplastic polyurethane composition according to any one of claims 1 to 8, wherein the thermoplastic polyurethane has a weight average molecular weight in the range of 50,000 Da to 500,000 Da.

10. The thermoplastic polyurethane composition according to any one of claims 1 to 8, wherein the thermoplastic polyurethane composition has a hardness of Shore 40A to Shore 80D, preferably Shore 50A to Shore 98A, as determined according to DIN ISO 48-4.

11. The thermoplastic polyurethane composition according to any one of claims 1 to 8, wherein a sheet having a thickness of 2 mm prepared from the thermoplastic polyurethane composition achieves UL94 V0 rating according to the procedure of Underwriters Laboratories Bulletin 94 entitled "Tests for Flammability of Plastic Materials, UL94".

12. An article produced from the thermoplastic polyurethane composition according to any one of claims 1 to 11.

13. The article of claim 12, wherein the article is artificial leather, a film, a sheet, a molded product, a fiber, an automotive interior, a tube, a hose, a profile, a pipe, a cable connector, a guy wire, a cable jacket, a wire, an optical component, an electronic component, an electrical component, a seal, a nonwoven fabric, a belt, or a damping element.

14. Use of the article according to claim 12 or 13 in an electric vehicle or a charging device for an electric vehicle, a household appliance, residential or office furniture, a building, an optical device, an electronic device or an electrical device.

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