Thermoplastic polyurethane elastomer composition

Abstract

To provide a thermoplastic polyurethane elastomer composition that contains a molybdate flame retardant. exhibits high flame retardancy and tensile strength, and further demonstrates superior water resistance.SOLUTION: A thermoplastic polyurethane elastomer composition contains a thermoplastic polyurethane elastomer, a molybdate flame retardant, a phosphorous flame retardant, and a carbodiimide compound. Relative to 100 pts.mass of the thermoplastic polyurethane elastomer, the molybdate flame retardant is more than 20 pts.mass and 50 pts.mass or less, the phosphorous flame retardant is more than 15 pts.mass and 50 pts.mass or less, and the carbodiimide compound is 0.3 pt.mass or more.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Since thermoplastic elastomers have rubber-like properties and excellent flexibility, they are widely used as alternative materials for vulcanized rubber and vinyl chloride resins in molded product materials such as automotive parts, electronic and electrical equipment parts, films, and coating materials for communication cables and electric wires. Flame retardancy may be required for these molded product materials and coating materials.

[0003] Conventionally, a flame retardant may be blended for the purpose of enhancing the flame retardancy of a thermoplastic polyurethane elastomer composition. For example, Patent Document 1 discloses a production method in which a hindered amine-based flame retardant and a phosphine-based flame retardant are individually mixed with a thermoplastic polyurethane elastomer, and then the respective mixtures are integrated to obtain a target composition. According to this production method, a composition excellent in mechanical properties can be obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a flame retardancy test for a resin composition for coating a cable, UL 1581 VW-1 or UL 1581 Cable Flame Test standards may be used as evaluation criteria. If a large amount of a flame retardant is blended into the resin composition, the flame retardancy will be improved, but there is a concern that mechanical properties such as tensile strength for coating the cable will deteriorate. Furthermore, it has been difficult to impart excellent water resistance while maintaining the mechanical properties.

[0006] The inventors noted that while incorporating a molybdate flame retardant into a resin composition does not significantly improve flame retardancy, it does make it easy to maintain tensile strength. Therefore, they searched for another flame retardant that, when used in combination with a molybdate flame retardant, could enhance flame retardancy while maintaining tensile strength. Furthermore, they diligently investigated how to impart excellent water resistance without compromising the effectiveness of these flame retardants.

[0007] The present invention has been made in view of the above circumstances, and provides a thermoplastic polyurethane elastomer composition containing a molybdate flame retardant, exhibiting excellent flame retardancy and tensile strength, and also having excellent water resistance. [Means for solving the problem]

[0008] [1] A thermoplastic polyurethane elastomer composition comprising a thermoplastic polyurethane elastomer, a molybdate flame retardant, a phosphorus-based flame retardant, and a carbodiimide compound, wherein the composition contains, per 100 parts by mass of the thermoplastic polyurethane elastomer, the molybdate flame retardant in proportion to more than 20 parts by mass and 50 parts by mass or less, the phosphorus-based flame retardant in proportion to more than 15 parts by mass and 50 parts by mass or less, and the carbodiimide compound in proportion to 0.3 parts by mass or more. [2] The thermoplastic polyurethane elastomer composition according to [1], further comprising the molybdate flame retardant and other flame retardants other than the phosphorus-based flame retardant, wherein the total content of the molybdate flame retardant, the phosphorus-based flame retardant and the other flame retardants is 40 to 80 parts by mass per 100 parts by mass of the thermoplastic polyurethane elastomer. [3] The thermoplastic polyurethane elastomer composition according to [1] or [2], comprising an organophosphorus compound as the phosphorus-based flame retardant. [4] The thermoplastic polyurethane elastomer composition according to any one of [1] to [3], wherein the thermoplastic polyurethane elastomer is a carbonate-based thermoplastic polyurethane elastomer having multiple carbonate bonds in the molecular chain of the elastomer. [5] A thermoplastic polyurethane elastomer composition according to any one of [1] to [4], having flame retardancy that meets the requirements of UL 1581 VW-1 and UL 1581 Cable Flame Test. [6] A thermoplastic polyurethane elastomer composition according to any one of items [1] to [5], wherein when a No. 5 dumbbell-shaped test specimen as specified in JIS K 6251:2010 is constructed, the tensile strength measured in accordance with JIS K 7161-2:2014 is 25 MPa or more. [7] The thermoplastic polyurethane elastomer composition according to [6], wherein the tensile strength of the test specimen after immersion in 80°C hot water for 168 hours is within ±30% of the tensile strength before immersion in the hot water.

[0009] [8] A method for producing a thermoplastic polyurethane elastomer composition comprising a thermoplastic polyurethane elastomer, a molybdate flame retardant, a phosphorus-based flame retardant, and a carbodiimide compound, comprising blending the molybdate flame retardant in a ratio of more than 20 parts by mass and 50 parts by mass or less, the phosphorus-based flame retardant in a ratio of more than 15 parts by mass and 50 parts by mass or less, and the carbodiimide compound in a ratio of 0.3 parts by mass or more, per 100 parts by mass of the thermoplastic polyurethane elastomer, and kneading these at 170°C or higher. [8] According to this, a thermoplastic polyurethane elastomer of the desired type can be obtained that is less susceptible to thermal degradation even when kneaded at temperatures above 170°C, maintains sufficient tensile strength, and also exhibits excellent water resistance. [Effects of the Invention]

[0010] The thermoplastic polyurethane elastomer composition of the present invention contains a molybdate flame retardant and a phosphorus-based flame retardant in predetermined proportions, thus exhibiting excellent flame retardancy and tensile strength. Furthermore, the added carbodiimide compound can impart water resistance without impairing the properties of the other flame retardants. [Modes for carrying out the invention]

[0011] In this specification and the claims, the lower and upper limits of the numerical ranges indicated by "~" are to be included within those numerical ranges.

[0012] Thermoplastic polyurethane elastomer composition A first aspect of the present invention is a thermoplastic polyurethane elastomer composition (TPU composition) comprising a thermoplastic polyurethane elastomer, a molybdate flame retardant, a phosphorus-based flame retardant, and a carbodiimide compound. The TPU composition of this embodiment contains, per 100 parts by mass of thermoplastic polyurethane elastomer (TPU), a molybdate flame retardant in an amount greater than 20 parts by mass and less than or equal to 50 parts by mass, a phosphorus-based flame retardant in an amount greater than 15 parts by mass and less than or equal to 50 parts by mass, and the carbodiimide compound in an amount of 0.3 parts by mass or more. The effects of the present invention can be fully obtained with this proportion.

[0013] In the TPU composition of this embodiment, the content of the molybdate flame retardant per 100 parts by mass of TPU is preferably more than 20 parts by mass and 40 parts by mass or less, more preferably more than 20 parts by mass and 35 parts by mass or less, and even more preferably more than 20 parts by mass and 30 parts by mass or less. Within the above preferred range, the effects of the present invention can be obtained even more reliably.

[0014] In the TPU composition of this embodiment, the content of the phosphorus-based flame retardant per 100 parts by mass of TPU is preferably 16 to 45 parts by mass, more preferably 17 to 42 parts by mass, even more preferably 18 to 38 parts by mass, and particularly preferably 19 to 35 parts by mass. Within the above preferred range, the effects of the present invention can be obtained even more reliably.

[0015] In the TPU composition of this embodiment, the content of the carbodiimide compound per 100 parts by mass of TPU is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.2 parts by mass or more, and particularly preferably 1.5 parts by mass or more. As a guideline, the upper limits for the lower limits mentioned above are 5 parts by mass or less, 4 parts by mass or less, and 3 parts by mass or less. When it is within the above - mentioned preferred range, the effects of the present invention can be obtained more surely.

[0016] The TPU composition of this embodiment preferably further contains other flame retardants. Here, other flame retardants refer to flame retardants other than molybdate flame retardants and phosphorus - based flame retardants. As other flame retardants, melamine - based flame retardants are particularly preferred. By containing other flame retardants together with molybdate flame retardants and phosphorus - based flame retardants, the flame retardancy can be further enhanced while maintaining the tensile strength. Furthermore, it is particularly noteworthy that when a melamine - based flame retardant and a carbodiimide compound are contained together, the water resistance of the TPU composition of this embodiment is further improved. In the TPU composition of this embodiment, with respect to 100 parts by mass of TPU, the content of other flame retardants is preferably 5 - 40 parts by mass, more preferably 10 - 35 parts by mass, and even more preferably 15 - 30 parts by mass. When it is within the above - mentioned preferred range, the effects of the present invention can be obtained more surely.

[0017] In the TPU composition of this embodiment, the total content of molybdate flame retardants, phosphorus - based flame retardants and other flame retardants is preferably 40 - 80 parts by mass, more preferably 50 - 75 parts by mass, and even more preferably 55 - 70 parts by mass with respect to 100 parts by mass of TPU. When it is within the above - mentioned preferred range, the effects of the present invention can be obtained even more surely.

[0018] <Thermoplastic polyurethane elastomer (abbreviation: TPU)> As the TPU of this embodiment, a block copolymer having a hard segment block and a soft segment block as repeating units is preferred.

[0019] The hard segment block preferably has a urethane bond formed by the reaction of at least a diisocyanate and diols. 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.

[0020] 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.

[0021] The soft segment block preferably has a urethane bond formed by the reaction of at least a diisocyanate and a polyol. Examples of diisocyanates include those previously exemplified in the description of hard segment blocks. Examples of polyols include polyester polyols, polyether polyols, and polycarbonate polyols.

[0022] 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 diols include those previously exemplified in the description of hard segment blocks. Examples of dicarboxylic acids include succinic acid, adipic acid, sebacic acid, phthalic acid, terephthalic acid, and isophthalic acid.

[0023] Examples of polyether polyols include polyether polyols obtained by condensation polymerization of dicarboxylic acid and glycol; polyethylene glycol; polypropylene glycol; and polytetramethylene glycol. Examples of dicarboxylic acids include those previously exemplified in the explanation of polyester polyols. Examples of glycols include diethylene glycol and propylene oxide adducts.

[0024] Examples of polycarbonate polyols include polycarbonate polyols obtained by the reaction of diols and carbonates, and copolymers of polycaprolactone polyol and polyhexamethylene carbonate. Examples of diols include those previously exemplified in the description of hard segment blocks. Examples of carbonates include ethylene carbonate and diethyl carbonate.

[0025] TPUs can be classified into ester-based TPUs, ether-based TPUs, and carbonate-based TPUs. Here, ester-based TPUs are TPUs that have multiple ester bonds in the molecular chain of the elastomer, ether-based TPUs are TPUs that have multiple ether bonds in the molecular chain of the elastomer, and carbonate-based TPUs are TPUs that have multiple carbonate bonds in the molecular chain of the elastomer. The above bonds contained in the molecular chain of the elastomer originate from the bonds present in the polyol used during the synthesis of the TPU. In this embodiment, carbonate-based TPU is preferred because it exhibits excellent tensile strength.

[0026] The TPU composition of this embodiment may contain one type of TPU or two or more types. From the viewpoint of improving the tensile strength while enhancing the flame retardancy of the TPU composition of this embodiment, the content of carbonate-based TPU in 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 the 100 parts by mass of TPU, the remainder other than the carbonate-based TPU can be arbitrarily selected from ester-based TPU and ether-based TPU.

[0027] From the viewpoint of increasing the tensile strength of the TPU composition of this embodiment, the TPU content relative to the total mass of the TPU composition is preferably 50% by mass or more. Furthermore, considering 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.

[0028] <Molybdate Flame Retardant> The molybdate flame retardant of this embodiment is a flame retardant containing a compound containing a molybdenum(VI) oxoanion, that is, a compound containing a salt of molybdic acid. Examples of molybdate flame retardants include molybdate salts such as zinc molybdate, calcium molybdate carbonate, calcium molybdate, potassium molybdate, and sodium molybdate. The molybdate flame retardant of this embodiment also includes those in which the molybdate forms a complex with other inorganic compounds. Examples of other inorganic compounds include magnesium compounds such as magnesium silicate and magnesium hydroxide. Among the above, molybdate flame retardants containing zinc molybdate or calcium molybdate are preferred. The molybdate flame retardant in the TPU composition of this embodiment may be one type or two or more types.

[0029] <Phosphorus-based flame retardant> The phosphorus-based flame retardant in this embodiment does not fall under the category of molybdate flame retardants or melamine-based flame retardants, and is a flame retardant composed of a compound containing a phosphorus atom. The phosphorus-based flame retardant is preferably one having a functional group derived from phosphoric acid or a polyphosphate chain. Phosphorus compounds can be broadly classified based on the presence or absence of condensation of the phosphoric acid moiety. Examples of non-condensing types include non-halogenated phosphate esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and cresyl di2,6-xylenyl phosphate; and halogenated phosphate esters such as tris(chloropropyl) phosphate and tris(tribromoneopentyl) phosphate. Examples of condensation types include aromatic condensed phosphate esters and aliphatic condensed phosphate esters. Examples of aromatic condensed phosphate esters include known compounds having multiple phosphate ester moieties in which a hydrogen atom of the hydroxyl group of the phosphate group is substituted by a phenyl group. Examples of aliphatic condensed phosphate esters include known compounds having multiple phosphate ester moieties in which aliphatic hydrocarbon groups substitute for hydrogen atoms of the hydroxyl groups of the phosphate group. Here, we assume that the aliphatic condensed phosphate ester does not have an aromatic group. Among phosphorus-based flame retardants, organophosphorus compounds consisting of phosphorus-containing organic compounds are preferred from the viewpoint of enhancing flame retardancy while maintaining sufficient tensile strength, condensed phosphorus-based flame retardants are more preferred, and aliphatic condensed phosphate esters are even more preferred. The phosphorus-based flame retardant in the TPU composition of this embodiment may be one type or two or more types.

[0030] <Other flame retardants> Other flame retardants include, for example, melamine-based flame retardants, aluminum hydroxide, and zinc borate. In the TPU composition of this embodiment, a melamine-based flame retardant is preferred because its water resistance is further improved when used in combination with a carbodiimide compound.

[0031] <Carbodiimide compounds> The carbodiimide compound of this embodiment is a compound having a carbodiimide group (-N=C=N-). Its molecular structure may be a cyclic carbodiimide in which the carbodiimide group constitutes part of a ring structure, or an acyclic carbodiimide in which the carbodiimide group does not constitute part of a ring structure. In the case of an acyclic carbodiimide, the parts other than the carbodiimide group may constitute a ring structure, for example, it may have an aromatic ring in the molecule. Furthermore, the number of carbodiimide groups contained within the molecule may be one or two or more. The molecular weight of the carbodiimide compound in this embodiment is preferably 1000 or less, and more preferably 500 or less, because it is easy to disperse in the TPU composition and the water resistance effect is fully exhibited. The carbodiimide compound in the TPU composition of this embodiment may be one type or two or more types.

[0032] <Melamine-based flame retardant> The melamine-based flame retardant in this embodiment does not fall under the category of molybdate flame retardants or phosphorus-based flame retardants, and is a flame retardant comprising a compound containing melamine or a melamine derivative, or a compound containing a functional group derived from melamine or a melamine derivative.

[0033] Examples of compounds containing melamine include melamine cyanurate (melamine cyanurate) and other melamine-containing organic salts. Examples of melamine derivatives include melamine (C6H9N 11 ), Merem (C6H6N 10 These are examples. These melamine derivatives can be included as salts to constitute a melamine-based flame retardant. Examples of functional groups derived from melamine include monovalent groups in which one of the hydrogen atoms present in melamine, melam, or melem has been removed. Among melamine-based flame retardants, melamine cyanurate is preferred from the viewpoint of maintaining sufficient tensile strength while enhancing the flame retardancy of the TPU composition in this embodiment. The melamine-based flame retardant in the TPU composition of this aspect may be one kind or two or more kinds.

[0034] In the present invention, in the sense of distinguishing between the phosphorus-based flame retardant and the melamine-based flame retardant and the molybdate-based flame retardant, the flame retardant containing molybdate, even if it contains a functional group derived from a phosphorus atom or melamine, does not fall under the phosphorus-based flame retardant and the melamine-based flame retardant, and is considered to fall under the molybdate-based flame retardant.

[0035] In the present invention, in the sense of distinguishing between the phosphorus-based flame retardant and the melamine-based flame retardant, the flame retardant containing a functional group derived from melamine, even if it contains a phosphorus atom, does not fall under the phosphorus-based flame retardant and falls under the melamine-based flame retardant.

[0036] <Other optional components> The TPU composition of this aspect may contain components (optional components) other than those described above, if necessary. Examples of the optional components include solvents, plasticizers, softeners such as process oils, fillers such as talc, carbon black, calcium carbonate, and various additives such as ultraviolet absorbers, antioxidants, processing stabilizers, and colorants. From the viewpoint of sufficiently 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 this aspect is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0037] <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 kneading (mixing) by a conventional method so that each component becomes uniform in the composition. Examples of the method for 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 knead at a resin temperature of 200°C or lower. On the other hand, since there is an advantage in improving productivity, it is preferable to knead at 170°C or higher.

[0038] <Form of TPU composition> The specific form of the TPU composition in this embodiment may be pellets, beads, or powders that are easily subjected to other molding processes, or it may be a molded article formed by known molding methods such as press molding, injection molding, or extrusion molding. The molded products are not particularly limited and include, for example, automotive parts, electronic and electrical equipment parts such as personal computers and photocopiers (e.g., keyboards, toner seals, cleaning blades, etc.), film materials such as raincoats, water hose materials, watch bands, figurines (three-dimensional models of people or characters, etc.), tool grips (screwdriver handles, etc.). Molded articles of the TPU composition obtained by the manufacturing method of the present invention are excellent not only in flame retardancy but also in tensile strength and water resistance, making them particularly useful for coating electric wires (cables).

[0039] (Tensile strength) When the TPU composition of this embodiment constitutes a No. 5 dumbbell-shaped test specimen as specified in JIS K 6251:2010, the tensile strength measured according to JIS K 7161-2:2014 is preferably 25 MPa or higher, more preferably 26 MPa or higher, and even more preferably 27 MPa or higher. The upper limit is not particularly limited, and considering the balance with flexibility and elongation, for example, around 45 MPa can be given as a guideline. The aforementioned tensile strength can be adjusted by the inherent tensile strength of the TPU used and the content of each flame retardant.

[0040] (water resistance) Preferably, the tensile strength of the test specimen after immersion in 80°C hot water for 168 hours is within ±30% of the tensile strength before immersion in the hot water. If the rate of change remains within the above range even after this immersion treatment, the TPU composition can be said to have high water resistance. Therefore, the rate of change is more preferably within ±25%, even more preferably within ±20%, particularly preferably within ±15%, and most preferably within ±10%.

[0041] (Flame retardant) The TPU composition of this embodiment preferably has flame retardancy that satisfies at least one of the requirements 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 methods. [Examples]

[0042] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions in these examples.

[0043] The details of the raw materials listed in Tables 1 and 2 are as follows: The "carbonate-based TPU" is Pandex T-9280 manufactured by DIC Covestropolymer. "Molybdate (1)" is KEMGARD 911C manufactured by Huber, and is a zinc molybdate / magnesium silicate complex. "Molybdate (2)" is KEMGARD 911A manufactured by Huber, and is a calcium molybdate zinc complex. The "phosphorus-based flame retardant" is FireGuard FCX-210 manufactured by Teijin Corporation, and is a phosphorus-based flame retardant containing organophosphorus compounds. The "melamine-based flame retardant" is STABIACE MC-2010N manufactured by Sakai Chemical Industry Co., Ltd., and is melamine cyanurate. "Carbodiimide compound (1)" is TCC-NP, a carbodista manufactured by Teijin Corporation, and is a cyclic carbodiimide. "Carbodiimide compound (2)" is TCC-FP20M, a cyclic carbodiimide manufactured by Teijin Corporation. "Carbodiimide compound (3)" is Stabaxol P manufactured by Rhein Chemie, and is an acyclic carbodiimide compound. "Carbodiimide compound (4)" is Stabaxol P100 manufactured by Rhein Chemie, and is an acyclic carbodiimide compound. The "fatty acid ester-based lubricant" is Roxyol G-32 manufactured by Emery Oleochemicals. "Calcium behenate" is CS-7 manufactured by Nitto Chemical Industries, Ltd. "Phenol-based antioxidant (1)" is ADEKA AO-60 manufactured by ADEKA Corporation. The "phenolic antioxidant (2)" is ADEKA AO-80 manufactured by ADEKA Corporation. The "hindered amine-based light stabilizer" is ADEKA LA-63P, manufactured by ADEKA Corporation. The "benzotriazole-based UV absorber" is JF-77, manufactured by Johoku Chemical Industry Co., Ltd. The "pigment masterbatch" is urethane black DN-20A manufactured by DIC Covestropolymer.

[0044] <Preparation of test specimens> The TPU compositions were prepared by mixing each material in the amounts (unit: parts by mass) listed in Tables 1 and 2. In each test example, 65g of the prepared formulation was placed in a Laboplast Mill (Toyo Seiki Co., Ltd.: Model No.: 4C150, Rotor: R30) and kneaded for 4 minutes at 50 revolutions per minute at a temperature of 170°C. The resulting mixture was kneaded for 1 minute using a 6-inch roll set to 160°C within 1 minute to create a 0.5 mm thick sheet. The sheet created here can be distinguished by the direction in which it passed through the roll (flow direction) and the direction perpendicular to it. Two sheets were prepared, and the flow directions of each sheet were overlapped so that they intersect (cross) each other. After preheating at 170°C for 4 minutes, the sheets were heated and compressed at 170°C and 15 MPa for 4 minutes, and then slowly cooled to room temperature (25°C) while under pressure to produce a 1 mm thick sheet-like test specimen.

[0045] <Physical property: Tensile strength> The test specimens were left to stand in an environment of 23±1℃ for 24 hours, and then their tensile strength was measured. Test specimens were punched out using a No. 5 dumbbell as specified in JIS K 6251:2010, and measured according to JIS K 7161-2:2014. The results are shown in Tables 1 and 2. Products with a tensile strength of 25 MPa or higher were deemed acceptable.

[0046] <Water resistance: Change in tensile strength after immersion> The test specimens were completely submerged in 80°C hot water for 168 hours, after which their tensile strength was measured. Specifically, measurements were taken in accordance with the JIS standards mentioned above. Based on the tensile strength before immersion (the physical property value described above), products with a change rate of ±30% or less were judged to be acceptable. The results are shown in Tables 1 and 2. In the table, "-" indicates that measurement was not performed.

[0047] <Flame retardant (1)> The flame retardancy of the following test cables was evaluated according to the UL 1581 Cable Flame Test procedure. The test specimen prepared as described above was cut to a size of 30 mm x 350 mm, and the shorter side was folded in half. This was then wrapped once around the outer circumference of a 10 mm diameter cylinder made of 80# wire mesh and secured with staples to create the test cable (outer diameter 12 mm, length 350 mm). Following the test method described above, the test cable was held vertically, and the burner flame was applied at a 20-degree angle. The process of ignition for 60 seconds, followed by a 30-second pause, was repeated three times to examine the degree of combustion. According to the above test method, products were judged to be acceptable if the afterburn combustion did not exceed 60 seconds, the indicator flag was not burned by more than 25%, and the surgical cotton at the bottom did not burn due to falling objects. The results are shown in Tables 1 and 2. Acceptable items are marked with "○" and unacceptable items with "×".

[0048] <Flame retardant (2)> The flame retardancy of the following test cables was evaluated according to the UL 1581 VW-1 test method. The test specimen prepared as described above was cut to a size of 30 mm x 350 mm, and the shorter side was folded in half. This was then wrapped once around the outer circumference of a 10 mm diameter cylinder made of 80# wire mesh and secured with staples to create the test cable (outer diameter 12 mm, length 350 mm). Following the test method described above, the test cable was held vertically, and the burner flame was applied at a 20-degree angle. The process of igniting for 15 seconds, followed by a 15-second pause, was repeated five times to examine the degree of combustion. According to the above test method, products were judged to be acceptable if the afterburn combustion did not exceed 60 seconds, the indicator flag was not burned by more than 25%, and the surgical cotton at the bottom did not burn due to falling objects. The results are shown in Tables 1 and 2. Acceptable items are marked with "○" and unacceptable items with "×".

[0049] In this embodiment, products that passed both the flame retardancy test (1) and the flame retardancy test (2) described above were considered final approved products.

[0050] [Table 1]

[0051] [Table 2]

[0052] <Rating> The TPU composition of the embodiment according to the present invention passed both a simulated test compliant with UL 1581 Cable Flame Test and a simulated test compliant with UL 1581 VW-1. The reason for using the term "simulated" here is that the conductive wires of the test cable were cylindrical wire mesh, but the test method itself conformed to the respective standards. Therefore, it is clear that similar results can be obtained even with a cable in which the TPU composition according to the present invention is coated with copper wire or the like. Furthermore, the TPU composition according to the present invention also exhibited excellent water resistance. In particular, the high water resistance of Examples 1 to 4, which contained a melamine-based flame retardant along with the carbodiimide compound, was remarkable. On the other hand, in Comparative Example 1, sufficient water resistance could not be obtained due to the low content of the carbodiimide compound. In Comparative Example 2, the flame retardancy was unsatisfactory due to the low content of the molybdate flame retardant and the phosphorus-based flame retardant. In Comparative Example 3, the flame retardancy was unsatisfactory due to the low content of the molybdate flame retardant. In Comparative Example 4, the flame retardancy was unsatisfactory due to the low content of the phosphorus-based flame retardant.

Claims

1. A thermoplastic polyurethane elastomer composition comprising a thermoplastic polyurethane elastomer, a molybdate flame retardant, a phosphorus-based flame retardant, and a carbodiimide compound, A thermoplastic polyurethane elastomer composition comprising, per 100 parts by mass of the thermoplastic polyurethane elastomer, the molybdate flame retardant in a proportion of more than 20 parts by mass and 50 parts by mass or less, the phosphorus-based flame retardant in a proportion of more than 15 parts by mass and 50 parts by mass or less, and the carbodiimide compound in a proportion of 0.3 parts by mass or more.

2. The thermoplastic polyurethane elastomer composition according to claim 1, further comprising the molybdate flame retardant and other flame retardants other than the phosphorus-based flame retardant, wherein the total content of the molybdate flame retardant, the phosphorus-based flame retardant and the other flame retardants is 40 to 80 parts by mass per 100 parts by mass of the thermoplastic polyurethane elastomer.

3. The thermoplastic polyurethane elastomer composition according to claim 2, wherein the phosphorus-based flame retardant comprises an organophosphorus compound.

4. The thermoplastic polyurethane elastomer composition according to claim 3, 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.

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

6. The thermoplastic polyurethane elastomer composition according to claim 5, wherein when a No. 5 dumbbell-shaped test specimen as specified in JIS K 6251:2010 is constructed, the tensile strength measured according to JIS K 7161-2:2014 is 25 MPa or more.

7. The thermoplastic polyurethane elastomer composition according to claim 6, wherein the tensile strength of the test specimen after immersion in 80°C hot water for 168 hours is within ±30% of the tensile strength before immersion in the hot water.

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