Thermoplastic polyurethane elastomer composition

Abstract

To provide a thermoplastic polyurethane elastomer composition, which has excellent tensile strength while containing a fire retardant in such an amount that excellent flame retardancy is exhibited.SOLUTION: Provided is a thermoplastic polyurethane elastomer composition, comprising: a thermoplastic polyurethane elastomer; an inorganic flame retardant which is at least one of a metal hydroxide and a metal hydrate; a phosphorus-based flame retardant; and a melamine-based flame retardant. Relative to 100 pts.mass of the thermoplastic polyurethane elastomer, the inorganic flame retardant, the phosphorus-based flame retardant, and the melamine-based flame retardant are contained in proportions of 5-50 pts.mass, 15-50 pts.mass, and 25-50 pts.mass, respectively. The thermoplastic polyurethane elastomer is a carbonate-based thermoplastic polyurethane elastomer having a plurality of carbonate bonds in an elastomer molecular chain.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic polyurethane elastomer composition. [Background technology]

[0002] Thermoplastic elastomers have rubber-like properties and excellent flexibility, and are therefore widely used as a substitute for vulcanized rubber and polyvinyl chloride resin in automotive parts, electronic and electrical equipment parts, molded product materials such as films, and covering materials for communication cables, electric wires, etc. These molded product materials and covering materials may sometimes be required to be flame retardant.

[0003] Conventionally, various flame retardants have been investigated for the purpose of improving the flame retardancy of resin compositions. Examples of such flame retardants include halogen-based flame retardants such as chlorine-based and bromine-based flame retardants, inorganic flame retardants such as metal hydroxides and metal hydrates, phosphorus-based flame retardants such as aliphatic condensed phosphate esters, and melamine-based flame retardants such as melamine isocyanurate. For example, Patent Document 1 discloses a thermoplastic polyurethane resin composition to which a melamine-based flame retardant has been added. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3862289 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional thermoplastic polyurethane resin compositions are evaluated for flame retardancy based on various test methods. While those that meet the standards certainly have excellent flame retardancy, it is counterproductive if other physical properties are neglected, resulting in a composition that is unsuitable for the intended application. For example, high tensile strength is required for applications such as covering electrical wires, but adding a large amount of flame retardant can deteriorate this physical property.

[0006] The present invention has been made in view of the above circumstances, and provides a thermoplastic polyurethane elastomer composition which contains a flame retardant in an amount that exhibits excellent flame retardancy, yet has excellent tensile strength. [Means for solving the problem]

[0007] [1] A thermoplastic polyurethane elastomer composition comprising a thermoplastic polyurethane elastomer, an inorganic flame retardant which is at least one of a metal hydroxide and a metal hydrate, a phosphorus-based flame retardant, and a melamine-based flame retardant, wherein the inorganic flame retardant, the phosphorus-based flame retardant, and the melamine-based flame retardant are contained in an amount of 5 to 50 parts by mass, 15 to 50 parts by mass, and 25 to 50 parts by mass, per 100 parts by mass of the thermoplastic polyurethane elastomer, and the thermoplastic polyurethane elastomer is a carbonate-based thermoplastic polyurethane elastomer having a plurality of carbonate bonds in the molecular chain of the elastomer. [2] The thermoplastic polyurethane elastomer composition according to [1], wherein the phosphorus-based flame retardant comprises an aliphatic condensed phosphate ester. [3] The thermoplastic polyurethane elastomer composition according to [1] or [2], wherein the inorganic flame retardant is aluminum hydroxide. [4] The thermoplastic polyurethane elastomer composition according to any one of [1] to [3], which has flame retardancy that satisfies the requirements of UL 1581 VW-1 and UL 1581 Cable Flame Test. [5] The thermoplastic polyurethane elastomer composition according to any one of [1] to [4], wherein when a No. 5 dumbbell test piece as specified in JIS K 6251:2010 is prepared, the tensile strength measured in accordance with JIS K 7161-2:2014 is 25 MPa or more. [6] The thermoplastic polyurethane elastomer composition according to [5], wherein the tensile strength of the test piece after immersion in hot water at 80°C for 168 hours has a rate of change within ±30% of the tensile strength before immersion in the hot water. [Effects of the Invention]

[0008] The thermoplastic polyurethane elastomer composition of the present invention exhibits excellent tensile strength while containing a flame retardant in an amount that exhibits excellent flame retardancy. Furthermore, the excellent tensile strength is fully maintained even after water immersion treatment. Furthermore, the present invention exhibits excellent flame retardancy without the use of a halogen-based flame retardant, which has a corrosive effect. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Thermoplastic polyurethane elastomer composition> A first embodiment of the present invention is a thermoplastic polyurethane elastomer composition (hereinafter sometimes referred to as a TPU composition) containing a thermoplastic polyurethane elastomer, an inorganic flame retardant which is at least one of a metal hydroxide and a metal hydrate, a phosphorus-based flame retardant, and a melamine-based flame retardant. The TPU composition preferably contains 5 to 50 parts by mass of the inorganic flame retardant, 15 to 50 parts by mass of the phosphorus-based flame retardant, and 25 to 50 parts by mass of the melamine-based flame retardant relative to 100 parts by mass of the thermoplastic polyurethane elastomer. The thermoplastic polyurethane elastomer is preferably a so-called polycarbonate-based TPU having a plurality of carbonate bonds in the molecular chain of the elastomer.

[0010] <Thermoplastic polyurethane elastomer (abbreviation: TPU)> The TPU of this embodiment is preferably a block copolymer having a hard segment block and a soft segment block as repeating units.

[0011] The hard segment block preferably has at least a urethane bond formed by the reaction of a diisocyanate with a diol. Examples of diisocyanates include 1,6-hexamethylene diisocyanate (HDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), hydrogenated XDI, tolylene diisocyanate (TDI), triisocyanate, tetramethylxylene diisocyanate (TMXDI), and 1,3,6-hexamethylene triisocyanate.

[0012] Examples of diols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, dipropylene glycol, and tripropylene glycol.

[0013] The soft segment block preferably has at least a urethane bond formed by the reaction of a diisocyanate with a polyol. Examples of the diisocyanate include the diisocyanates exemplified above in the description of the hard segment block. Examples of the polyol include polyester polyol, polyether polyol, and polycarbonate polyol.

[0014] Examples of polyester polyols include polyester polyols obtained by condensation polymerization of diols and dicarboxylic acids; and polylactone diols obtained by ring-opening polymerization of lactone monomers such as ε-caprolactone. Examples of the diols include the diols exemplified above in the description of the hard segment blocks. Examples of dicarboxylic acids include succinic acid, adipic acid, sebacic acid, phthalic acid, terephthalic acid, and isophthalic acid.

[0015] Examples of polyether polyols include polyether polyols obtained by condensation polymerization of dicarboxylic acids and glycols; polyethylene glycol; polypropylene glycol; and polytetramethylene glycol. Examples of the dicarboxylic acid include the dicarboxylic acids exemplified above in the description of the polyester polyol. Examples of glycols include diethylene glycol and propylene oxide adducts.

[0016] Examples of polycarbonate polyols include polycarbonate polyols obtained by reacting diols with carbonates; copolymers of polycaprolactone polyol and polyhexamethylene carbonate; and the like. Examples of the diols include the diols exemplified above in the description of the hard segment blocks. Examples of carbonates include ethylene carbonate and diethyl carbonate.

[0017] TPUs can be classified into ester-based TPUs, ether-based TPUs, and carbonate-based TPUs. Ester-based TPUs have multiple ester bonds in the elastomer molecular chain, ether-based TPUs have multiple ether bonds in the elastomer molecular chain, and carbonate-based TPUs have multiple carbonate bonds in the elastomer molecular chain. These bonds in the elastomer molecular chain originate from the bonds in the polyol used in the synthesis of the TPU. In this embodiment, carbonate-based TPU is preferred because of its excellent tensile strength.

[0018] The TPU of the present embodiment may be one type or a combination of two or more types. From the viewpoint of improving the tensile strength while enhancing the flame retardancy of the TPU composition of the present embodiment, the content of the carbonate-based TPU per 100 parts by mass of TPU is preferably 50 parts by mass or more and 100 parts by mass or less, more preferably 70 parts by mass or more and 100 parts by mass or less, and even more preferably 90 parts by mass or more and 100 parts by mass or less. Here, of 100 parts by mass of TPU, the remainder other than carbonate-based TPU can be arbitrarily selected from ester-based TPU and ether-based TPU.

[0019] From the viewpoint of increasing the tensile strength of the TPU composition of this embodiment, the content of TPU relative to the total mass of the TPU composition is preferably 50% by mass or more. Furthermore, taking into consideration the addition of each flame retardant, the content is preferably 50 to 80% by mass, more preferably 50 to 70% by mass, and even more preferably 50 to 65% by mass.

[0020] <Inorganic flame retardants> The inorganic flame retardant of the present embodiment preferably contains at least one of a metal hydroxide and a metal hydrate. Examples of metal hydroxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, etc. Among these, aluminum hydroxide is preferred because it is excellent in improving flame retardancy. Examples of metal hydrates include zinc borate. Among the inorganic flame retardants, aluminum hydroxide is preferred from the viewpoint of improving the flame retardancy and tensile strength of the present embodiment. In this embodiment, sufficient flame retardancy can be obtained without blending so-called antimony-based flame retardant aids such as antimony trioxide and antimony pentoxide.

[0021] The TPU composition of the present embodiment may contain one type of inorganic flame retardant, or two or more types of inorganic flame retardants. From the viewpoint of improving the tensile strength while enhancing the flame retardancy of the TPU composition of the present embodiment, the content of the inorganic flame retardant per 100 parts by mass of TPU is preferably 5 to 50 parts by mass, more preferably 7 to 30 parts by mass, and even more preferably 9 to 20 parts by mass.

[0022] <Phosphorus-based flame retardants> The phosphorus-based flame retardant of this embodiment is a flame retardant composed of a compound containing a phosphorus atom, which does not fall under the category of the inorganic flame retardant or the melamine-based flame retardant. The phosphorus-based flame retardant preferably has a functional group derived from phosphoric acid or a polyphosphate chain. The phosphorus-based compounds can be broadly classified according to whether or not the phosphoric acid moiety is condensed. Examples of non-condensed types include non-halogen phosphate esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and cresyl di-2,6-xylenyl phosphate; and halogen-containing phosphate esters such as tris(chloropropyl)phosphate and tris(tribromoneopentyl)phosphate. The condensed type includes aromatic condensed phosphate esters and aliphatic condensed phosphate esters. Examples of aromatic condensed phosphate esters include known compounds having a plurality of phosphate ester moieties in which the hydrogen atoms of the hydroxyl groups of phosphate groups are substituted with phenyl groups. Examples of the aliphatic condensed phosphate ester include known compounds having multiple phosphate ester moieties in which the hydrogen atoms of the hydroxyl groups of the phosphate groups are substituted with aliphatic hydrocarbon groups. Here, the aliphatic condensed phosphate ester does not have an aromatic group. Among the phosphorus-based flame retardants, from the viewpoint of improving the flame retardancy and tensile strength of the present embodiment, condensed phosphorus-based flame retardants are preferred, and aliphatic condensed phosphate esters are more preferred.

[0023] In the present invention, in order to distinguish between phosphorus-based flame retardants and melamine-based flame retardants, a flame retardant containing a functional group derived from melamine is not considered to be a phosphorus-based flame retardant but is considered to be a melamine-based flame retardant, even if it has a functional group derived from phosphoric acid.

[0024] The TPU composition of the present embodiment may contain one type of phosphorus-based flame retardant, or two or more types of phosphorus-based flame retardants. From the viewpoint of improving the tensile strength while enhancing the flame retardancy of the TPU composition of the present embodiment, the content of the phosphorus-based flame retardant per 100 parts by mass of TPU is preferably 15 to 50 parts by mass, more preferably 18 to 40 parts by mass, and even more preferably 21 to 30 parts by mass.

[0025] <Melamine-based flame retardants> The melamine-based flame retardant of this embodiment does not fall under the category of inorganic flame retardants, but is a flame retardant made of a compound containing melamine or a melamine derivative, or a compound containing a functional group derived from melamine or a melamine derivative. Even if the compound contains a phosphorus atom or a phosphate group or a functional group derived from phosphoric acid, if the compound contains a functional group derived from melamine, it falls under the category of melamine-based flame retardants, but does not fall under the category of phosphorus-based flame retardants.

[0026] Examples of compounds containing melamine include organic salts containing melamine, such as melamine cyanurate (melamine cyanurate). Examples of melamine derivatives include melam (C6H9N 11 ), Melem (C6H6N 10 These melamine derivatives can be included as salts to form melamine-based flame retardants. Examples of functional groups derived from melamine include monovalent groups in which any one of the hydrogen atoms contained in melamine, melam, or melem has been removed. Among the melamine-based flame retardants, melamine cyanurate is preferred from the viewpoint of improving the flame retardancy and tensile strength of the present embodiment.

[0027] The TPU composition of the present embodiment may contain one type of melamine-based flame retardant, or two or more types of melamine-based flame retardants. From the viewpoint of improving the tensile strength while enhancing the flame retardancy of the TPU composition of the present embodiment, the content of the melamine-based flame retardant per 100 parts by mass of TPU is preferably 25 to 50 parts by mass, more preferably 27 to 45 parts by mass, and even more preferably 29 to 40 parts by mass.

[0028] In the TPU composition of the present embodiment, the relative ratios (by mass) of the content X of the inorganic flame retardant, the content Y of the phosphorus-based flame retardant, and the content Z of the melamine-based flame retardant are preferably X < Y < Z. In this relative ratio, the ratio represented by Y / X is preferably 1.2 to 4.0, more preferably 1.5 to 3.5, and even more preferably 2.0 to 2.9. Also, the ratio represented by Z / X is preferably 2.0 to 6.0, more preferably 2.5 to 5.0, and even more preferably 3.0 to 4.0. With the above relative contents, the flame retardancy of the TPU composition of the present embodiment and the tensile strength after immersion treatment can be further improved.

[0029] <Other optional components> The TPU composition of the present embodiment may contain components other than those described above (optional components) as necessary. Examples of the optional components include solvents, plasticizers, softening agents such as process oils, fillers such as talc, carbon black, and calcium carbonate, and various additives such as ultraviolet absorbers, antioxidants, processing stabilizers, and colorants. From the viewpoint of fully obtaining the effects of the present invention, the content of the above optional components with respect to the total mass of the TPU composition of the present embodiment is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0030] <Method for producing TPU composition> The method for producing the TPU composition according to the present invention is not particularly limited, and it can be obtained by mixing and kneading by a conventional method so that each component becomes uniform in the composition. Examples of the method for mixing and kneading TPU and each flame retardant component include methods using a pressure kneader, a Banbury mixer, etc. When mixing, from the viewpoint of preventing the decomposition of TPU, it is preferable to mix and knead at a resin temperature of 180°C or lower.

[0031] <Form of TPU composition> The specific form of the TPU composition of the present embodiment may be pellets, beads, or powders that are easy to be subjected to another molding process, or molded products molded by known molding methods such as press molding, injection molding, and extrusion molding. The molded article is not particularly limited, and examples thereof include automobile parts, electronic and electrical device parts for personal computers, copy machines, etc. (for example, keyboards, toner seal materials, cleaning blades, etc.), film materials for raincoats, etc., water-discharge hose materials, watch bands, figurines (three-dimensional models of humans, characters, etc.), tool grips (screwdriver handles, etc.), etc. Molded articles of the TPU composition obtained by the production method of the present invention are not only flame retardant but also have excellent tensile strength after water immersion treatment, making them particularly useful for covering electric wires (cables).

[0032] (tensile strength) When the TPU composition of this embodiment is used to form a No. 5 dumbbell-shaped test piece as specified in JIS K 6251:2010, the tensile strength measured according to JIS K 7161-2:2014 is preferably 25 MPa or more, more preferably 26 MPa or more, and even more preferably 27 MPa or more. There are no particular upper limits, and taking into account the balance between flexibility and elongation, a guideline is, for example, about 45 MPa. The tensile strength can be adjusted by the inherent tensile strength of the TPU used and the content of each flame retardant.

[0033] (water resistance) Furthermore, it is preferable that the tensile strength of the test piece after immersion in 80°C water for 168 hours has a change rate of within ±30% of the tensile strength before immersion. If the change rate after this water immersion treatment falls within the above range, the TPU composition can be said to have high water resistance. Therefore, the change rate is more preferably within ±25%, even more preferably within ±20%, particularly preferably within ±15%, and most preferably within ±10%.

[0034] (Flame retardant) The TPU composition of the present embodiment preferably has flame retardancy that satisfies the requirements of at least one of UL 1581 VW-1 and UL 1581 Cable Flame Test. Whether or not the requirements of UL 1581 VW-1 and UL 1581 Cable Flame Test are met can be confirmed by performing the following test method. [Example]

[0035] The present invention will be specifically explained below by showing examples, but the present invention is not limited to the descriptions of these examples.

[0036] The details of the raw materials listed in Table 1 are as follows: "Carbonate-based TPU (1)" is Pandex T-9280 manufactured by DIC Covestro Polymers. "Carbonate-based TPU (2)" is ESTANE TS 92AP7 NAT 055 manufactured by Lubrizol. "Carbonate-based TPU (3)" is ET1080-10N manufactured by BASF. "Ether-based TPU resin (1)" is ESTANE 58315 manufactured by Lubrizol. "Ether-based TPU resin (2)" is ET 385-10 manufactured by BASF. "Aluminum hydroxide" is aluminum hydroxide BF-013 manufactured by Nippon Light Metal Co., Ltd. The "phosphorus-based flame retardant" is SR-8100 manufactured by Daihachi Chemical Industry Co., Ltd., and is an aliphatic condensed phosphate ester. "Melamine cyanurate" is MC-2010N manufactured by Sakai Chemical Industry Co., Ltd. The "phosphorus-nitrogen compound" is FRAN CM-6R manufactured by Yamato Chemical Industry Co., Ltd. "Calcium behenate" is CS-7 manufactured by Nitto Kasei Kogyo Co., Ltd. "Phenol-based antioxidant (1)" is Adeka Stab AO-60 manufactured by ADEKA Corporation. "Phenol-based antioxidant (2)" is Adeka Stab AO-80 manufactured by ADEKA Corporation. The "hindered amine light stabilizer" is Adekastab LA-63P manufactured by ADEKA Corporation. The "benzotriazole-based ultraviolet absorber" is JF-77 manufactured by Johoku Chemical Industry Co., Ltd. The "pigment masterbatch" is urethane black DN-20A manufactured by DIC Covestro Polymer.

[0037] <Creating test specimens> The components were mixed in the amounts (parts by mass) shown in Table 1 to prepare the respective formulations. In each test example, 65 g of the prepared compound was placed in a Labo Plastomill (manufactured by Toyo Seiki Co., Ltd.: model number: 4C150, rotor: R30) and kneaded at 160°C and 30 rpm for 2 minutes. The resulting kneaded material was kneaded for 1 minute using a 6-inch roll set at 160°C within 1 minute to produce a 0.5 mm thick sheet. The direction in which the sheet passed through the roll (flow direction) and the direction perpendicular to it can be distinguished for the sheet produced here. Two sheets were prepared, stacked with their flow directions crossing each other, preheated at 170°C for 4 minutes, and then heat-compressed and molded at 170°C and 15 MPa for 4 minutes. Subsequently, the sheets were slowly cooled to room temperature (25°C) while still under pressure to produce 1 mm thick sheet-like test specimens.

[0038] <Physical properties: tensile strength> The test pieces were left to stand in an environment of 23±1°C for 24 hours, and then the tensile strength was measured. Test pieces were punched out using a No. 5 dumbbell as specified in JIS K 6251:2010 and measured in accordance with JIS K 7161-2:2014. The results are shown in Table 1. Products with a tensile strength of 25 MPa or more were judged to be acceptable.

[0039] <Water resistance: Change in tensile strength after immersion in water> The test pieces were completely submerged in 80°C warm water for 168 hours, and then the tensile strength was measured. Specifically, the measurements were carried out in accordance with the above-mentioned JIS standard, and the results are shown in Table 1. Using the tensile strength (the physical property value mentioned above) before immersion as the standard, products with a change rate within ±30% were judged to be acceptable. The results are shown in Table 1. In Table 1, "-" indicates that the measurement was not performed.

[0040] <Flame retardancy (1)> The flame retardancy of the following test cables was evaluated according to the UL 1581 Cable Flame Test method. The test piece prepared above was cut into a size of 30 mm × 350 mm, and the short side was folded in half. This was wrapped in a single layer around the outer circumference of a 10 mm diameter cylinder made of 80# wire mesh and stapled to form a test cable (outer diameter 12 mm, length 350 mm). According to the above test method, the test cable was held vertically and exposed to a burner flame at a 20 degree angle, ignited for 60 seconds, followed by a 30 second break, which was repeated three times to check the degree of combustion. According to the above test method, a product was judged to pass if the burning due to residual flame did not exceed 60 seconds, the indicator flag was not burned by 25% or more, and the surgical cotton at the bottom was not burned by a dropped object. The results are shown in Table 1. Passed products are marked with "○" and failed products are marked with "×".

[0041] <Flame retardancy (2)> The flame retardancy of the following test cables was evaluated according to the test method of UL 1581 VW-1. The test piece prepared above was cut into a size of 30 mm × 350 mm, and the short side was folded in half. This was wrapped in a single layer around the outer circumference of a 10 mm diameter cylinder made of 80# wire mesh and stapled to form a test cable (outer diameter 12 mm, length 350 mm). According to the above test method, the test cable was held vertically and exposed to a burner flame at an angle of 20 degrees, ignited for 15 seconds, and then rested for 15 seconds, which was repeated five times to check the degree of combustion. According to the above test method, a product was judged to pass if the burning due to residual flame did not exceed 60 seconds, the indicator flag was not burned by 25% or more, and the surgical cotton at the bottom was not burned by a dropped object. The results are shown in Table 1. Passed products are indicated by "○", failed products by "×", and not measured by "-".

[0042] In this example, the product that passed both the flame retardancy (1) and the flame retardancy (2) was determined to be a final passing product.

[0043] [Table 1]

[0044] <Evaluation> The TPU compositions of the examples of the present invention passed both the simulated test conforming to the UL 1581 Cable Flame Test and the simulated test conforming to UL 1581 VW-1. The reason for the term "simulated" here is that the conductive wire of the test cable was a wire mesh cylinder, and the test method itself conformed to each standard. Therefore, it is clear that similar results can be obtained with cables in which the TPU composition of the present invention is used to cover copper wires or the like. On the other hand, in Comparative Example 1, the flame retardancy was unacceptable due to the low content of metal hydroxide, in Comparative Example 2, the flame retardancy was unacceptable due to the low content of phosphorus-based flame retardant, and in Comparative Example 3, the flame retardancy was unacceptable due to the low content of melamine-based flame retardant. In addition, the tensile strength of Comparative Example 4 was unacceptable due to the high content of metal hydroxide, the tensile strength of Comparative Example 5 was unacceptable due to the high content of phosphorus-based flame retardant, and the tensile strength of Comparative Example 6 was unacceptable due to the high content of melamine-based flame retardant. In addition, in Comparative Examples 7 and 8, the tensile strength was unacceptable because the ether-based TPU resin was used instead of the carbonate-based TPU resin. Comparative Example 9 contained a phosphorus-nitrogen compound called FRAN CM-6R manufactured by Daihachi Chemical Industry Co., Ltd., and although it had excellent flame retardancy, the tensile strength after water immersion treatment was significantly reduced.

Claims

1. A thermoplastic polyurethane elastomer composition comprising a thermoplastic polyurethane elastomer, an inorganic flame retardant which is at least one of a metal hydroxide and a metal hydrate, a phosphorus-based flame retardant, and a melamine-based flame retardant, The inorganic flame retardant, the phosphorus-based flame retardant, and the melamine-based flame retardant are contained in an amount of 5 to 50 parts by mass, 15 to 50 parts by mass, and 25 to 50 parts by mass, relative to 100 parts by mass of the thermoplastic polyurethane elastomer, a relative ratio (by mass) of the content X of the inorganic flame retardant to the content Y of the phosphorus-based flame retardant to the content Z of the melamine-based flame retardant is X<Y<Z; In the relative ratio, the ratio represented by Y / X is 2.0 to 2.9, or the ratio represented by Z / X is 3.0 to 4.0; The thermoplastic polyurethane elastomer composition, wherein the thermoplastic polyurethane elastomer is a carbonate-based thermoplastic polyurethane elastomer having a plurality of carbonate bonds in the molecular chain of the elastomer.

2. The thermoplastic polyurethane elastomer composition of claim 1 , wherein the phosphorus-based flame retardant comprises an aliphatic condensed phosphate ester.

3. 3. The thermoplastic polyurethane elastomer composition according to claim 1, wherein the inorganic flame retardant is aluminum hydroxide.

4. The thermoplastic polyurethane elastomer composition according to any one of claims 1 to 3, which has flame retardancy that satisfies the requirements of UL 1581 VW-1 and UL 1581 Cable Flame Test.

5. The thermoplastic polyurethane elastomer composition according to any one of claims 1 to 4, wherein, when a No. 5 dumbbell test piece specified in JIS K 6251:2010 is prepared, the tensile strength measured in accordance with JIS K 7161-2:2014 is 25 MPa or more.

6. 6. The thermoplastic polyurethane elastomer composition according to claim 5, wherein the tensile strength of the test piece after immersion in hot water at 80°C for 168 hours changes by a rate of change within ±30% of the tensile strength before immersion in the hot water.

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