Crosslinked molded body, method for producing crosslinked molded body, and covering material

Abstract

Provided is a crosslinked molded body which maintains flexibility as an elastomer material and mechanical properties, and which exhibits high heat resistance that achieves a balance between hot rigidity in a high temperature environment and thermal ageing resistance. The crosslinked molded body is characterized by being obtained by crosslinking a resin composition containing a thermoplastic polyester elastomer resin (A) in which a hard segment formed from a polyester comprising an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components is bound to a soft segment formed from an aliphatic polycarbonate.

Description

Crosslinked molded article, method for manufacturing a crosslinked molded article, and coating material

[0001] This invention relates to a highly heat-resistant crosslinked molded article that uses a thermoplastic polyester elastomer resin and achieves both hot rigidity in high-temperature environments and heat aging resistance while maintaining flexibility and mechanical properties as an elastomer material.

[0002] In recent years, there has been a growing trend to replace metal and rubber parts with thermoplastic resins in automobiles and home appliances. Furthermore, with the increasing performance of automobiles and home appliances, the distance between parts is decreasing, and resin parts are increasingly exposed to extremely high temperatures. Given these development trends, there is a strong demand for the development of resin compositions that possess both heat resistance and flame retardancy.

[0003] In response to the above requirements, thermoplastic polyester elastomer resins such as polyether ester type, polyester ester type, and polycarbonate ester type are widely used as materials with excellent heat resistance and mechanical properties. Note that the aforementioned polyether ester type, polyester ester type, and polycarbonate ester type refer to the types that constitute the soft segment of the hard segment and soft segment that make up the thermoplastic polyester elastomer resin.

[0004] In particular, among the thermoplastic polyester elastomer resins mentioned above, the polycarbonate ester type has excellent heat aging resistance and oil swelling resistance, and there are many practical examples of applications requiring a very high level of heat resistance (see, for example, Patent Documents 1 to 5).

[0005] However, because the thermoplastic polyester elastomer resin containing the polycarbonate ester type soft segment is a thermoplastic resin, its usable temperature range is limited to the crystalline melting point of the hard segment constituting the thermoplastic polyester elastomer resin. In reality, even with the polycarbonate ester type, the development of a material usable in the high-temperature range of around 190°C has not yet been achieved.

[0006] While the melting point of thermoplastic polyester elastomer resins can be controlled to some extent by increasing the proportion of hard segment components or adjusting the blockiness (chain length), it is not possible to exceed the melting point potential caused by the type of hard segment component. Even if the heat aging resistance caused by soft segments can be improved, this has not yet led to an expansion of the usable temperature range of molded articles obtained using thermoplastic polyester elastomer resins.

[0007] To address the above issues, Patent Documents 6 to 8 disclose a method for crosslinking a molded article (e.g., a cable, a bellows-type molded article, etc.) obtained using a thermoplastic polyester elastomer resin that satisfies specific constituent requirements by irradiating the molded article with an electron beam. While this method achieves either a short-term improvement in heat resistance in high-temperature environments or a long-term improvement in heat resistance, it only achieves either a short-term or long-term effect, and has not yet achieved both. Furthermore, Patent Document 8, which mentions long-term heat resistance improvement, has a low usable temperature of 150°C, which is insufficient to satisfy the performance requirements and demands in the high-temperature range of around 190°C that is practically necessary.

[0008] Japanese Patent Publication No. 7-39480, Japanese Patent Publication No. 10-182782, Japanese Patent Publication No. 2001-206939, Japanese Patent Publication No. 2001-240663, Japanese Patent Publication No. 4244067, Japanese Patent Publication No. 3663275, Japanese Patent Publication No. 2014-196501, Japanese Patent Publication No. 2023-49227

[0009] This invention was conceived in view of the current situation, and aims to provide a highly heat-resistant crosslinked molded article that maintains the flexibility and mechanical properties of an elastomer material while simultaneously achieving high hot rigidity and heat aging resistance in high-temperature environments.

[0010] As a result of diligent research to achieve the above objective, the inventors of the present invention have discovered that a crosslinked molded article obtained by crosslinking a resin composition containing a specific thermoplastic polyester elastomer resin can achieve both hot rigidity and heat aging resistance in high-temperature environments while maintaining flexibility and mechanical properties, thereby exhibiting high heat resistance, and have completed the present invention.

[0011] That is, the present invention has the following configurations (1) to (11): (1) A crosslinked molded article characterized by being obtained by crosslinking a resin composition containing a thermoplastic polyester elastomer resin (A) in which a hard segment formed from a polyester comprising an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components is bonded to a soft segment formed from an aliphatic polycarbonate. (2) The elongation at break (absolute value) measured in accordance with JIS K6251 is 200% or more, and the storage modulus E' at 220°C obtained by dynamic viscoelasticity measurement in accordance with JIS K7244 is 1.0 × 10 ５(1) A cross-linked molded article characterized by having a Pa of 30% or more. (3) A cross-linked molded article characterized by having a gel fraction of 30% by mass or more. (4) A cross-linked molded article characterized by having an elongation at break (absolute value) of 80% or more after heat treatment at 190°C for 240 hours, as measured in accordance with JIS K6251. (5) A cross-linked molded article characterized in that the thermoplastic polyester elastomer resin (A) contains 30 to 75% by mass of the hard segment and 25 to 70% by mass of the soft segment. (6) A cross-linked molded article characterized in that the resin composition contains a flame retardant (B). (7) A cross-linked molded article characterized in that the resin composition contains a carbodiimide compound (C). (8) The crosslinked molded article according to (1), wherein the resin composition further contains a flame retardant (B) and a carbodiimide compound (C), and the thermoplastic polyester elastomer resin (A) contains 30 to 65% by mass of the hard segment and 35 to 70% by mass of the soft segment. (9) A method for producing a crosslinked molded article according to any one of (1) to (8), comprising a step of extrusion molding. (10) A method for producing a crosslinked molded article according to (9), further comprising a step of irradiation with an electron beam. (11) A coating material characterized by being obtained by a crosslinked molded article according to any one of (1) to (8).

[0012] The present invention is useful because it can provide a highly heat-resistant crosslinked molded article that maintains the flexibility and mechanical properties of an elastomer material while simultaneously achieving hot rigidity and heat aging resistance in high-temperature environments.

[0013] The present invention relates to a crosslinked molded article characterized by being obtained by crosslinking a resin composition comprising a thermoplastic polyester elastomer resin (A) in which a hard segment formed from a polyester comprising an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components is bonded to a soft segment formed from an aliphatic polycarbonate. A molded article obtained by extrusion molding or the like from a resin composition containing the thermoplastic polyester elastomer resin (A) is simply referred to as a "molded article," and a crosslinked article obtained by crosslinking the resin composition or the molded article is referred to as a "crosslinked molded article."

[0014] [Thermoplastic polyester elastomer resin (A)] Thermoplastic polyester elastomer resin (A) (hereinafter sometimes referred to as "component (A)") is a compound formed by bonding a hard segment made of a polyester having aromatic dicarboxylic acid and aliphatic and / or alicyclic diol as constituent components, and a soft segment made of aliphatic polycarbonate.

[0015] (Hard Segment Components) The hard segments constituting the thermoplastic polyester elastomer resin (A) are characterized by being formed from a polyester comprising an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components. The aromatic dicarboxylic acid is not particularly limited, and a wide range of ordinary aromatic dicarboxylic acids are widely used, but for example, terephthalic acid or naphthalenedicarboxylic acid (among the isomers, 2,6-naphthalenedicarboxylic acid is preferred) are preferred. Thermoplastic polyester elastomer resin (A) in which terephthalic acid is the aromatic dicarboxylic acid component in the hard segment is excellent in that it easily exhibits high crystallinity, mechanical strength, heat resistance, and chemical resistance due to the symmetry and intermolecular forces of the benzene ring. Furthermore, naphthalenedicarboxylic acid has a structure in which the benzene ring in terephthalic acid is replaced with a naphthalene ring. Due to the high aromaticity and planarity of the naphthalene ring structure, thermoplastic polyester elastomer resins using naphthalenedicarboxylic acid as the aromatic dicarboxylic acid component in the hard segment have higher hydrophobicity and gas barrier properties compared to thermoplastic polyester elastomer resins using terephthalic acid as the aromatic dicarboxylic acid component in the hard segment, resulting in superior heat aging resistance and hydrolysis resistance. On the other hand, the rigidity and asymmetry of the naphthalene ring structure induce an increase in elastic modulus and glass transition temperature. Therefore, in terms of flexibility and low-temperature properties of crosslinked molded articles obtained from resin compositions containing thermoplastic polyester elastomer resins, thermoplastic polyester elastomer resins using terephthalic acid as the aromatic dicarboxylic acid component in the hard segment are superior to thermoplastic polyester elastomer resins using naphthalenedicarboxylic acid as the aromatic dicarboxylic acid component in the hard segment.

[0016] In this invention, the aromatic dicarboxylic acid is used as a component of the polyester, but other dicarboxylic acid components can be used as long as they do not impair the properties of the crosslinked molded article of this invention.

[0017] The content of terephthalic acid or naphthalenedicarboxylic acid relative to 100 mol% of the total dicarboxylic acid components, including the aromatic dicarboxylic acid constituting the polyester, is preferably 70 mol% or more, and more preferably 80 mol% or more.

[0018] Other dicarboxylic acid components besides terephthalic acid and naphthalenedicarboxylic acid mentioned above include, for example, aromatic dicarboxylic acids such as diphenyldicarboxylic acid, isophthalic acid, and 5-sodium sulfisoisophthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and tetrahydrophthalic anhydride; and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, and hydrogenated dimer acid. These may be used individually or in combination of two or more.

[0019] Furthermore, the aliphatic and / or alicyclic diol is not particularly limited, and ordinary aliphatic and alicyclic diols are widely used, but it is preferably mainly alkylene glycols having 2 to 8 carbon atoms. Specific examples of alkylene glycols having 2 to 8 carbon atoms include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. These may be used individually or in combination of two or more. Among these, 1,4-butanediol is particularly preferred for imparting heat aging resistance and crystallinity during molding.

[0020] As constituent components of the polyester, butylene terephthalate units (units consisting of terephthalic acid and 1,4-butanediol) and butylene naphthalate units (units consisting of 2,6-naphthalenedicarboxylic acid and 1,4-butanediol) are preferred from the viewpoint of physical properties, moldability, and cost performance.

[0021] Furthermore, when an aromatic polyester suitable as the polyester constituting the hard segment in the thermoplastic polyester elastomer resin (A) is manufactured in advance and then miscibled and copolymerized with the soft segment component, the aromatic polyester can be easily obtained according to known polyester manufacturing methods. The number average molecular weight (Mn) of the aromatic polyester is preferably 10,000 to 40,000, and more preferably 20,000 to 35,000, from the viewpoint of balancing the molecular weight of the final thermoplastic polyester elastomer resin (A) with the time required for miscibled with the soft segment.

[0022] (Soft Segment Component) The soft segment constituting the thermoplastic polyester elastomer resin (A) is characterized by being formed from an aliphatic polycarbonate. Using the aliphatic polycarbonate for the soft segment is preferable because it provides excellent heat aging resistance and oil swelling resistance to the resulting crosslinked molded article.

[0023] The aliphatic polycarbonate is not particularly limited, but it is preferable that it mainly contains aliphatic diol residues having 2 to 12 carbon atoms. Examples of aliphatic diols constituting the aliphatic diol residues include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,9-nonanediol, and 2-methyl-1,8-octanediol. These may be used individually or in combination of two or more. In particular, from the viewpoint of the flexibility and low-temperature properties of the crosslinked molded article using the resulting thermoplastic polyester elastomer resin, it is preferable to use aliphatic diols having 5 to 12 carbon atoms.

[0024] From the viewpoint of low-temperature properties, the aliphatic polycarbonate constituting the soft segment is preferably one with a low melting point (for example, 70°C or lower) and a low glass transition temperature. Generally, aliphatic polycarbonates (including aliphatic polycarbonate diols) used to constitute the soft segment of polyester elastomers (thermoplastic polyester elastomer resins) include aliphatic polycarbonate diols composed of 1,6-hexanediol. These have a low glass transition temperature of around -60°C and a low melting point of around 50°C, resulting in good low-temperature properties. In addition, copolymers obtained by copolymerizing an appropriate amount of 3-methyl-1,5-pentanediol have a slightly higher glass transition temperature compared to the aliphatic polycarbonate diol before copolymerization, but their melting point is lower or they become amorphous, resulting in good low-temperature properties. Furthermore, aliphatic polycarbonate diols composed of 1,9-nonanediol and 2-methyl-1,8-octanediol have a sufficiently low glass transition temperature of around -70°C and a low melting point of around 30°C, making them suitable for aliphatic polycarbonate diols with good low-temperature properties.

[0025] In this invention, the aliphatic polycarbonate is used as a component of the soft segment, but other diol components can be used as long as they do not impair the properties of the crosslinked molded article of this invention.

[0026] The thermoplastic polyester elastomer resin (A) is preferably a copolymer with a melting point of 150 to 230°C, more preferably 160 to 220°C, and even more preferably 170 to 215°C. The dicarboxylic acid component constituting such a thermoplastic polyester elastomer resin (A) preferably contains 70 mol% or more of terephthalic acid as the aromatic dicarboxylic acid, based on 100 mol% of the total dicarboxylic acid component. Furthermore, the diol component constituting the thermoplastic polyester elastomer resin (A) preferably contains 70 mol% or more of the aliphatic diol, consisting of the aliphatic polycarbonate and 1,4-butanediol, based on 100 mol% of the total diol component.

[0027] The mass ratio of hard segments to soft segments constituting the thermoplastic polyester elastomer resin (A) is preferably 20:80 to 85:15, more preferably 25:75 to 80:20, even more preferably 30:70 to 75:25, particularly preferably 30:70 to 65:35, and most preferably 30:70 to 60:40. When the proportion of soft segments is high (i.e., the proportion of hard segments is low), the flexibility of the resulting cross-linked molded article and the elongation at break after heat treatment can be maintained, but on the other hand, there is a risk that swelling during the oil resistance test will be large. Also, when the proportion of soft segments is low (i.e., the proportion of hard segments is high), swelling during the oil resistance test can be reduced, but on the other hand, there is a risk that the flexibility of the resulting cross-linked molded article and the elongation at break after heat treatment cannot be maintained.

[0028] The thermoplastic polyester elastomer resin (A) is characterized by the bonding of hard segments and soft segments. Here, it is preferable that the "bonding" is not achieved by a chain extender such as an isocyanate compound, but rather by direct bonding through ester bonds or carbonate bonds contained in the units constituting the hard segments and soft segments. For example, as a method for synthesizing the thermoplastic polyester elastomer resin (A) by bonding the hard segments and soft segments, it is preferable to obtain the resin by repeatedly performing transesterification and depolymerization reactions for a certain period of time under molten conditions on the polyester constituting the hard segments and the aliphatic polycarbonate constituting the soft segments. The higher the bond energy between the units constituting the hard segments and soft segments, the better the heat resistance of the thermoplastic polyester elastomer resin (A). Therefore, by directly bonding through ester bonds or carbonate bonds contained in the units constituting the hard segments and soft segments, rather than bonding using an isocyanate compound, a crosslinked molded article with better heat aging resistance can be obtained.

[0029] The reduced viscosity of the thermoplastic polyester elastomer resin (A) is preferably 0.6 to 2.0 dl / g, and more preferably 0.6 to 1.8 dl / g. If the reduced viscosity is low, the molecular weight of the polymer constituting the thermoplastic polyester elastomer resin (A) becomes small, which may lead to a decrease in tensile properties and heat aging resistance. On the other hand, if the reduced viscosity is too high, the load on the machine during melt molding may become excessive, and if the molding method for the cross-linked molded article obtained using the thermoplastic polyester elastomer resin (A) is extrusion molding, there is a risk of surface defects such as melt fractures occurring easily.

[0030] The acid value of the thermoplastic polyester elastomer resin (A) is preferably 60 eq / ton or less, and more preferably 50 eq / ton or less. Having the acid value within this range reduces the number of carboxyl terminals that promote hydrolysis of the polymer constituting the resulting thermoplastic polyester elastomer resin (A), resulting in excellent hydrolysis resistance of the crosslinked molded article obtained using the thermoplastic polyester elastomer resin (A), which is preferable.

[0031] The Shore D hardness of the thermoplastic polyester elastomer resin (A), measured in accordance with JIS K6253:2012, is preferably 25 to 65, and more preferably 30 to 55. If the Shore D hardness exceeds the upper limit, the resulting cross-linked molded article may not maintain its flexibility and elongation at break after heat treatment. On the other hand, if the Shore D hardness falls below the lower limit, swelling during the oil resistance test may be excessive. By setting the Shore D hardness within the above range, the article exhibits excellent flexibility, elongation at break after heat treatment, and resistance to oil swelling, which is preferable.

[0032] The thermoplastic polyester elastomer resin (A) can be produced by known methods. For example, any of the following methods can be used: (1) a transesterification reaction of a lower alcohol diester of a dicarboxylic acid, an excess amount of low molecular weight glycol, and a soft segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product; (2) an esterification reaction of a dicarboxylic acid, an excess amount of glycol, and a soft segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product; (3) a method in which a polyester constituting the hard segment is synthesized in advance, an aliphatic polycarbonate constituting the soft segment is added to the obtained polyester, a transesterification reaction is carried out, and randomization occurs; or (4) a method in which the hard segment component and the soft segment component are linked using a chain linker (for example, a polyfunctional isocyanate compound such as diphenylmethane diisocyanate or hexamethylene diisocyanate).

[0033] Furthermore, as a specific method for producing the thermoplastic polyester elastomer resin (A), for example, when producing a thermoplastic polyester elastomer resin (A) mainly composed of an aliphatic polycarbonate diol consisting of terephthalic acid, an aromatic dicarboxylic acid used in the synthesis of the polyester constituting the hard segment, 1,4-butanediol, an aliphatic diol, and 1,6-hexanediol, an aliphatic polycarbonate constituting the soft segment, the method described in Japanese Patent Publication No. 4244067 can be adopted as the manufacturing method. Preferably, the thermoplastic polyester elastomer resin (A) produced by the above method has a melting point difference (Tm1-Tm3) of 0 to 50°C between the melting point (Tm1) obtained in the first measurement and the melting point (Tm3) obtained in the third measurement, when the temperature is raised from room temperature to 300°C at a heating rate of 20°C / min using a differential scanning calorimeter, held at 300°C for 3 minutes, and then cooled to room temperature at a cooling rate of 100°C / min, repeated three times. The fact that the melting point difference (Tm1-Tm3) is in the range of 0 to 50°C means that the transesterification reaction due to thermal history is sufficiently suppressed, and thus it is possible to provide a thermoplastic polyester elastomer resin (A) that is useful in that it is possible to obtain a crosslinked molded article that shows little change in crystallinity and elastic performance over time in a heat aging test, for example.

[0034] The gel fraction of the thermoplastic polyester elastomer resin (A) is preferably less than 10% by mass, more preferably less than 5% by mass, and even more preferably less than 1% by mass, when the gel fraction (insoluble matter) after heat treatment in N-methyl-2-pyrrolidone (NMP) solvent at 150°C for 3 hours. The gel fraction may also be 0% by mass. Having the gel fraction within the above range makes it possible to suppress gelation during the manufacturing of the thermoplastic polyester elastomer resin (A), as well as foreign matter (fish eyes) and appearance defects during melt molding.

[0035] In addition to the thermoplastic polyester elastomer resin (A), the resin composition may optionally further contain a flame retardant (B) and / or a carbodiimide compound (C).

[0036] [Flame retardant (B)] The resin composition preferably contains a flame retardant (B) (hereinafter sometimes referred to as "component (B)") in addition to the thermoplastic polyester elastomer resin (A). If flame retardancy is required in the application to which the crosslinked molded article of the present invention is applied, the flame retardant (B) may be included.

[0037] The aforementioned flame retardants can be broadly classified into halogen-based flame retardants and non-halogen-based flame retardants. Halogen-based flame retardants have high flame retardancy but have a high environmental impact, and their use has been restricted in recent years. Non-halogen-based flame retardants have a lower environmental impact compared to halogen-based flame retardants, but their flame retardancy is inferior to halogen-based flame retardants, so the required content is generally higher. In the case of both halogen-based and non-halogen-based flame retardants, if the content is excessive, the elongation at cleavage of the resulting cross-linked molded article tends to decrease, and this tendency becomes more pronounced with the presence of the cross-linked structure and heat treatment. In other words, halogen-based and non-halogen-based flame retardants have different flame retardancy efficiencies and different optimal content ranges, so these will also be explained below.

[0038] (Halogen-based flame retardant) As the halogenic flame retardant, bromine-based flame retardants can be mentioned. As the bromine-based flame retardant, for example, hexabromocyclododecane, decabromodiphenyl oxide, octabromodiphenyl oxide, tetrabromobisphenol A, bis(tribromophenoxy)ethane, bis(pentabromophenoxy)ethane, tetrabromobisphenol A epoxy resin, tetrabromobisphenol A carbonate, ethylene(bistetrabromophthal)imide, ethylenebispentabromodiphenyl, tris(tribromophenoxy)triazine, bis(dibromopropyl)tetrabromobisphenol A, bis(dibromopropyl)tetrabromobisphenol S, brominated polyphenylene ether (including poly(d)bromophenylene ether etc.), brominated polystyrene (including polydibromostyrene, polytribromostyrene, crosslinked brominated polystyrene etc.), brominated crosslinked aromatic polymer, brominated epoxy resin, brominated phenoxy resin, brominated styrene-maleic anhydride polymer, tetrabromobisphenol S, tris(tribromoneopentyl)phosphate, polybromotrimethylphenylindane, tris(dibromopropyl)-isocyanurate etc. can be mentioned. These may be used in combination of one kind or two or more kinds. Among these, from the viewpoints of compatibility with the thermoplastic polyester elastomer resin (A) and exhibiting high heat aging resistance, brominated polystyrene is preferable.

[0039] [Flame retardant aid] From the viewpoint of the synergistic effect of flame retardancy, the resin composition can contain a flame retardant aid in combination with the flame retardant (B). For example, when the halogen-based flame retardant is used as the flame retardant (B), it is preferable to use an antimony oxide compound in combination as the flame retardant aid. As the antimony oxide compound, antimony trioxide, antimony pentoxide, sodium antimonate etc. can be mentioned.

[0040] As the total content by the combination of the flame retardant and the flame retardant aid, when using the halogen-based flame retardant (for example, bromine-based flame retardant) and the flame retardant aid (for example, antimony trioxide), it is preferably 5 to 40 parts by mass with respect to 100 parts by mass of the thermoplastic polyester elastomer resin (A). When the total content is less than the above range, the flame retardancy becomes insufficient. When the total content exceeds the above range, there may be a problem that mechanical properties such as elongation at break of the obtained crosslinked molded body decrease. By using the total content within the above range, a resin composition capable of obtaining a crosslinked molded body particularly excellent in flame retardancy and heat aging resistance can be prepared.

[0041] (Non-halogen-based flame retardant) Examples of the non-halogen-based flame retardant include nitrogen-based flame retardants, phosphorus-based flame retardants, silicon-based flame retardants, metal hydroxides, and metal borates. From the viewpoint of flame retardancy, phosphorus-based flame retardants are preferred.

[0042] Examples of the phosphorus-based flame retardant used in the present invention include organic phosphorus compounds and inorganic phosphorus compounds.

[0043] Examples of the organic phosphorus compound include phosphates, phosphonates, phosphinates, and phosphites. More specifically, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, octyldiphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, triphenyl phosphate, trixylenyl phosphate, tris(isopropylphenyl)phosphate, diethyl-N,N-bis(2-hydroxyethyl)aminomethyl phosphonate, bis(1,3-phenylenediphenyl)phosphate, and the like. These may be used alone or in combination of two or more. Among them, from the viewpoint of flame retardancy, metal phosphinate salts are preferred, and aluminum phosphinate salts are more preferred.

[0044] Examples of the inorganic phosphorus compounds include red phosphorus compounds and inorganic phosphate compounds such as (poly)ammonium phosphate, (poly)melamine phosphate, and (poly)piperazine phosphate. In some industries, there are restrictions on the use of organophosphorus compounds, so the application of inorganic phosphorus compounds may be necessary. In this case, (poly)phosphate compounds are preferred as the inorganic phosphorus compounds.

[0045] Examples of the (poly)phosphate compounds include monomeric orthophosphates and condensed phosphates obtained by a dehydration reaction of orthophosphates, with pyrophosphates, metaphosphates, and polyphosphates being examples of condensed phosphates. The (poly)phosphate compound refers to one or more compounds selected from orthophosphate compounds, pyrophosphate compounds, metaphosphate compounds, and polyphosphate compounds. While there are no particular problems with using any of these (poly)phosphate compounds, a (poly)phosphate compound with a lower molecular weight is preferred from the viewpoint of exhibiting high flame retardancy. Furthermore, a (poly)phosphate compound with a higher molecular weight is preferred from the viewpoint of suppressing bleed-out of phosphorus-based flame retardants and elution during immersion in water. Therefore, among the (poly)phosphate compounds, pyrophosphate compounds are preferred. The (poly)phosphate compound may be a single (poly)phosphate compound or a composite flame retardant containing two or more (poly)phosphate compounds.

[0046] The properties (flame retardancy and thermal stability) of the (poly)phosphate compounds are derived from the chemical structure of their counterions, and each counterion has its own unique characteristics. For example, ammonium (poly)phosphate has excellent flame retardancy but poor processing stability, while melamine (poly)phosphate has excellent processing stability but poor flame retardancy. By using a composite flame retardant containing two or more of the (poly)phosphate compounds, a composition with an excellent balance of multiple properties such as flame retardancy and processing stability can be obtained. In particular, using a composite flame retardant consisting of melamine (poly)phosphate and piperazine (poly)phosphate as the phosphorus-based flame retardant is a preferred embodiment because it allows for a composition with an even better balance of flame retardancy and processing stability (i.e., mechanical properties). Furthermore, using a composite flame retardant consisting of melamine pyrophosphate and piperazine pyrophosphate as the phosphorus-based flame retardant is an even more preferred embodiment from the viewpoint of heat aging resistance.

[0047] The phosphorus-based flame retardant is preferably one that has an average particle size D50 of 20 μm or less and a phosphorus concentration of 15% by mass or more. The upper limit of the average particle size D50 is more preferably 16 μm or less, and even more preferably 12 μm or less. There is no particular limit to the lower limit of the average particle size D50, but it is preferably 0.1 μm or more. If a flame retardant with a large average particle size D50 is used, there is a risk that the surface smoothness of the resulting molded article (extruded article, etc.) will deteriorate and the heat aging resistance will decrease during extrusion molding or other processes in the manufacture of the cross-linked molded article. The lower limit of the phosphorus concentration is preferably 18% by mass or more, and more preferably 20% by mass or more. There is no particular limit to the upper limit of the phosphorus concentration, but it is preferably 30% by mass or less. If a flame retardant with a low phosphorus concentration is used, there is a risk that the flame retardant effect will be poor, requiring the addition of a large amount, making it difficult to achieve both flame retardancy and other properties.

[0048] The average particle size D50 can be measured and analyzed using a laser diffraction particle size distribution analyzer, and the phosphorus concentration can be measured (calculated) using ICP emission spectroscopy.

[0049] The content of the phosphorus-based flame retardant in the resin composition is preferably 5 to 50 parts by mass, more preferably 8 to 45 parts by mass, even more preferably 10 to 40 parts by mass, and particularly preferably 15 to 35 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin (A). If the content of the phosphorus-based flame retardant is below the above range, the flame retardancy is insufficient, and if it exceeds the above range, problems arise such as a decrease in mechanical properties such as elongation at break. By using the phosphorus-based flame retardant in a content within the above range, a crosslinked molded article with particularly excellent flame retardancy and heat aging resistance can be obtained.

[0050] Furthermore, the resin composition may optionally contain non-halogenated flame retardants other than the phosphorus-based flame retardant.

[0051] [Carbodiimide compound (C)] The resin composition preferably contains a carbodiimide compound (C) (hereinafter sometimes referred to as "component (A)") in addition to the thermoplastic polyester elastomer resin (A). Using the carbodiimide compound is preferable because it can suppress the decrease in the heat resistance of the resulting crosslinked molded article, for example, when the flame retardant (B) is used. The carbodiimide compound (C) is a type of acid end-capping agent and is a compound having a functional group that can react with the terminal carboxyl groups of the thermoplastic polyester elastomer resin (A). Examples of functional groups that can react with the terminal carboxyl groups of the thermoplastic polyester elastomer resin (A) include epoxy groups, hydroxyl groups, carbodiimide groups, oxazoline groups, etc.

[0052] The carbodiimide compound (C) is a compound having at least one carbodiimide group represented as (-N=C=N-) in its molecule, and is capable of reacting with the terminal groups of the thermoplastic polyester elastomer resin (A). Compared with other acid end-canceling agents, the carbodiimide compound (C) exhibits superior reactivity with terminal carboxyl groups and improved heat aging resistance of the resulting crosslinked molded article.

[0053] Examples of the carbodiimide compound (C) include diphenylcarbodiimide, dicyclohexylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, diisopropylcarbodiimide, dioctyldecylcarbodiimide, di-o-toluylcarbodiimide, di-p-toluylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, and di-3,4-dichloro Phenylcarbodiimide, di-2,5-dichlorophenylcarbodiimide, p-phenylene-bis-o-toluylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-di-p-chlorophenylcarbodiimide, 2,6,2',6'-tetraisopropyldiphenylcarbodiimide, hexamethylene-bis-cyclohexylcarbodiimide, ethylene-bis-diphenylcarbodiimide, ethylene-bis-dicyclohexylcarbodiimide, N,N'-di-o-toluylcarbodiimide, N,N'-di Phenylcarbodiimide, N,N'-dioctyldecylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N-toluyl-N'-cyclohexylcarbodiimide, N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-2,6-di-tert-butylphenylcarbodiimide, N-toluyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-aminophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N, N'-di-cyclohexylcarbodiimide, N,N'-di-p-toluylcarbodiimide, N,N'-benzylcarbodiimide, N-octadecyl-N'-phenylcarbodiimide, N-benzyl-N'-phenylcarbodiimide, N-octadecyl-N'-toluylcarbodiimide, N-cyclohexyl-N'-toluylcarbodiimide, N-phenyl-N'-toluylcarbodiimide, N-benzyl-N'-toluylcarbodiimide, N,N'-di-o-ethylphenylcarbodiimide, N,N'-di-p-ethylphenylcarbodiimide, N,Mono or dicarbodimide compounds such as N'-di-o-isopropylphenylcarbodiimide, N,N'-di-p-isopropylphenylcarbodiimide, N,N'-di-o-isobutylphenylcarbodiimide, N,N'-di-p-isobutylphenylcarbodiimide, N,N'-di-2,6-diethylphenylcarbodiimide, N,N'-di-2-ethyl-6-isopropylphenylcarbodiimide, N,N'-di-2-isobutyl-6-isopropylphenylcarbodiimide, N,N'-di-2,4,6-trimethylphenylcarbodiimide, N,N'-di-2,4,6-triisopropylphenylcarbodiimide, N,N'-di-2,4,6-triisobutylphenylcarbodiimide, poly(1,6-hexamethylenecarb) Examples of polycarbodiimides include diimide, poly(4,4'-methylenebiscyclohexylcarbodiimide), poly(1,3-cyclohexylenecarbodiimide), poly(1,4-cyclohexylenecarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(toluylcarbodiimide), poly(diisopropylcarbodiimide), poly(methyl-diisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide). These may be used individually or in combination of two or more types. In particular, it is preferable to use N,N'-di-2,6-diisopropylphenylcarbodiimide, 2,6,2',6'-tetraisopropyldiphenylcarbodiimide, and polycarbodiimide, such as poly(1,6-hexamethylenecarbodiimide), poly(4,4'-methylenebiscyclohexylcarbodiimide), poly(1,3-cyclohexylenecarbodiimide), poly(1,4-cyclohexylenecarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), and poly(3,3'-dimethyl-4,It is more preferable to use polycarbodiimides such as 4'-diphenylmethanecarbodiimide, poly(naphthylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(toluylcarbodiimide), poly(diisopropylcarbodiimide), poly(methyl-diisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide). In particular, from the viewpoint of reactivity with thermoplastic polyester elastomer resin (A) and low outgassing, poly(1,4-cyclohexylenecarbodiimide) and poly(triisopropylphenylenecarbodiimide) are even more preferable.

[0054] The content of the carbodiimide compound (C) in the resin composition is preferably 5 parts by mass or less, and more preferably 4 parts by mass or less, per 100 parts by mass of the thermoplastic polyester elastomer resin (A). The carbodiimide compound (C) is added for the purpose of improving heat aging resistance, hydrolysis resistance, and bending fatigue resistance by chain extension, but if the content is too high, an increase in decomposition gas of the carbodiimide compound (C) may occur.

[0055] In addition to the carbodiimide compound (C), the resin composition may also contain general-purpose acid end-canceling agents such as epoxy compounds and oxazoline compounds.

[0056] The total content ratio of the thermoplastic polyester elastomer resin (A), the flame retardant (B), and the carbodiimide compound (C) in the resin composition (where (B) and (C) are optional components) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of maintaining the oil-resistant swelling properties inherent in the thermoplastic polyester elastomer resin (A).

[0057] Furthermore, when the resin composition contains the thermoplastic polyester elastomer resin (A), flame retardant (B), and carbodiimide compound (C), it is preferable that the thermoplastic polyester elastomer resin (A) contains 30 to 65% by mass of the hard segment and 35 to 70% by mass of the soft segment, and more preferably 35 to 60% by mass of the hard segment and 40 to 65% by mass of the soft segment. By including the flame retardant (B) in the resin composition, the flame retardancy of the crosslinked molded article can be improved, but on the other hand, the flexibility as an elastomer material decreases, resulting in a decrease in heat resistance. To suppress this, the heat resistance and flame retardancy can be adjusted in a good balance by keeping the content ratio of the hard segment component lower than usual. In addition, by including the carbodiimide compound (C), the heat resistance is improved, which increases the design freedom in the content ratio of the hard segment component, making it possible to achieve a higher level of balance between flexibility, heat resistance, and flame retardancy, and is useful.

[0058] [Antioxidants] The resin composition may contain antioxidants in addition to the above-mentioned components (A) to (C) from the viewpoint of improving heat aging resistance and retention stability. Examples of such antioxidants include general-purpose antioxidants such as aromatic amine-based, hindered phenol-based, phosphorus-based, and sulfur-based antioxidants. These may be used individually or in combination of two or more.

[0059] Examples of the aromatic amine-based antioxidants include amines and their derivatives such as N,N-diphenylethylenediamine, N,N-diphenylacetamidine, N,N-diphenylfluamidine, N-phenylpiperidine, dibenzylethylenediamine, triethanolamine, phenothiazine, N,N'-di-sec-butyl-p-phenylenediamine, 4,4'-tetramethyl-diaminodiphenylmethane, P,P'-dioctyl-diphenylamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, and 4,4'-bis(4-α,α-dimethylbenzyl)diphenylamine, as well as reaction products of amines and aldehydes, and reaction products of amines and ketones.

[0060] Examples of the hindered phenol antioxidants include 3,5-di-t-butyl-4-hydroxytoluene, n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,3,5-trimethyl-2,4,6'-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, and calcium(3,5-di-t-butyl-4-hydroxybenzyl-monoethyl-phosphate). ), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butylanilino)-1,3,5-triazine, 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, bis[3,3-bis(4'-hydroxy-3'-t-butylphenyl)butyrate] glycol ester, triphe Nol, 2,2'-ethylidenebis(4,6-di-t-butylphenol), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-oxamidebis[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,1,3-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) Examples include socianurates, 3,5-di-t-butyl-4-hydroxyhydrocinnamic ahydrotriester with-1,3,5-tris(2-hydroxyethyl)-S-triazine-2,4,6(1H,3H,5H), N,N-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnaamide), and 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0061] Examples of phosphorus-based antioxidants include phosphoric acid, phosphorous acid, hypophosphorous acid derivatives, phenylphosphonic acid, polyphosphonates, and diphosphite compounds containing phosphorus. Specific examples include tris(mixed, mono, and dinolylphenyl) phosphite, tris(2,3-di-t-butylphenyl) phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, 1,1,3-tris(2-methyl-4-di-tridecylphosphite-5-t-butylphenyl)butane, tris(2,4-di-t-butylphenyl) phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol-di-phosphite, and tetrakis(2,4-di-t Examples include (-butylphenyl)-4,4'-biphenylene phosphatite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylenediphosphonite, triphenyl phosphite, diphenyldecyl phosphite, tridecyl phosphite, trioctyl phosphite, toridedecyl phosphite, trioctadecyl phosphite, trinonylphenyl phosphite, toridedecyltrithiophosphite, and others.

[0062] Examples of sulfur-based antioxidants include sulfur-containing compounds such as thioethers, dithioates, mercaptobenzimidazoles, thiocarbanilides, and thiodipropion esters. Specific examples include dilauryl thiodipropionate, distearyl thiodipropionate, didodecyl thiodipropionate, ditetradecyl thiodipropionate, dioctadecyl thiodipropionate, pentaerythritol tetrakis(3-dodecylthiopropionate), thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropyl xanthate, and trilauryl trithiophosphite. In particular, thioether-based antioxidants having a thioether structure can be suitably used because they receive oxygen from oxidized substances and reduce them.

[0063] The antioxidant content in the resin composition is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin (A). If the antioxidant content is less than the above range, sufficient improvement in retention stability during processes such as melt molding of the resin composition and in the heat aging resistance of the crosslinked molded article cannot be obtained. If the content is more than the above range, inhibition of the crosslinking reaction by electron beam irradiation of the molded article, as described later, may occur, or bleed-out of the antioxidant contained in the crosslinked molded article may occur.

[0064] [Polyamide Resin] The resin composition may contain a polyamide resin from the viewpoint of improving the heat aging resistance of the resulting crosslinked molded article. The polyamide resin is a polymer compound having amide bonds in its molecular chain, and examples include polyamides obtained from diamines having aliphatic hydrocarbon groups having 2 to 20 carbon atoms or their substituted aliphatic hydrocarbon groups, or aromatic hydrocarbon groups having 6 to 16 carbon atoms or their substituted aromatic hydrocarbon groups, and dicarboxylic acids having aliphatic hydrocarbon groups having 2 to 20 carbon atoms or their substituted aliphatic hydrocarbon groups, or aromatic hydrocarbon groups having 6 to 16 carbon atoms, or their substituted aromatic hydrocarbon groups; polymers obtained from lactams; polymers obtained from ω-aminocarboxylic acids.

[0065] Examples of the polyamide resin include polymers obtained by the reaction of carboxylic acid components such as adipic acid, sebacic acid, linoleic acid, and dodecanedionic acid with diamine components such as ethylenediamine, hexamethylenediamine, and metaxylylenediamine. Other examples include polyamide 4, polyamide 6, polyamide 7, polyamide 8, polyamide 9, polyamide 11, and polyamide 12 obtained from lactams or ω-aminocarboxylic acids, polyamide 66, polyamide 69, polyamide 610, polyamide 611, polyamide 612, polyamide 6T, polyamide 6I, and polyamide MXD6 obtained from diamines and dicarboxylic acids, and copolymers thereof such as polyamide 6 / 66, polyamide 6 / 610, polyamide 6 / 6T, polyamide 6I / 6T, and polyamide 6 / 66 / 12. These may be used individually or in combination of two or more. Of these, polyamide 6 and / or a copolymerized polyamide resin with two or more elements having a melting point close to that of the thermoplastic polyester elastomer resin (A) is preferred because it is less likely to generate unmelted foreign matter during melt molding, and a copolymerized polyamide resin with two or more elements is more preferred.

[0066] The amine value of the polyamide resin is preferably 50 to 2000 eq / t, more preferably 70 to 1000 eq / t, even more preferably 100 to 700 eq / t, and particularly preferably 100 to 550 eq / t. Having the amine value within the above range is preferable because it greatly improves the heat aging resistance of the resulting cross-linked molded article.

[0067] The polyamide resin content in the resin composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 7 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin (A). If the amount of polyamide resin is greater than the above range, the oil swelling resistance, chemical resistance, and low water absorption of the thermoplastic polyester elastomer resin (A) may be impaired, and if it is less than the above range, the effect of improving the heat aging resistance of the resulting crosslinked molded article may be small.

[0068] [Weather-resistant stabilizers] When weather resistance is required for the crosslinked molded article of the present invention, it is preferable to include an ultraviolet absorber and / or a hindered amine compound in the resin composition. Examples of weather-resistant stabilizers include benzophenone-based, benzotriazole-based, triazole-based, nickel-based, and salicyl-based light stabilizers.

[0069] Specifically, the weather-resistant stabilizers include 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, p-t-butylphenyl salicylate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, and 2-[2'-hydroxy- 3',5'-bis(α,α-dimethylbenzylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenazotriazoazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzothiriazole, 2,5-bis-[5'-t-butylbenzoxazolyl-(2)]-thiophene, bis(3,5-di-t-butyl-4-hydroxybenzylphosphate monoethyl ester) nickel salt, 2-E A mixture of 85-90% toxic-5-t-butyl-2'-ethyl oxalic acid bis-anilide and 10-15% 2-ethoxy-5-t-butyl-2'-ethyl-4'-t-butyl oxalic acid bis-anilide, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-ethoxy-2'-ethyl oxalic acid bis-anilide, 2-[2'-hydrooxy-5'-methyl-3'-(3'',4'' Examples of light stabilizers include ,5'',6''-tetrahydrophthalimidomethyl)phenyl]benzotriazole, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-hydroxy-4-i-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, and phenyl salicylate. These may be used individually or in combination of two or more.

[0070] The proportion of the weather-resistant stabilizer in the resin composition is preferably 0.1 to 5% by mass, based on the mass of the resin composition (100% by mass).

[0071] [Other Additives] The resin composition may contain other resins, coloring pigments, inorganic and organic fillers, coupling agents, tack enhancers, quenchers, metal deactivators and other stabilizers, etc., to the extent that they do not impair the properties of the crosslinked molded article of the present invention.

[0072] The melt flow rate (MFR) of the resin composition can be measured at 230°C and under a load of 2.16 kg in accordance with the flow test method for thermoplastic plastics specified in JIS K7210. The MFR value is not particularly limited, but varies depending on the manufacturing method of the molded article (assumed molding method). For example, in extrusion molding, the MFR at the molding temperature is preferably 1 to 200 g / 10 min, and more preferably 2 to 100 g / 10 min. In injection molding, it is preferably 5 to 200 g / 10 min, and more preferably 10 to 100 g / 10 min. In blow molding, it is preferably 0.1 to 5 g / 10 min, and more preferably 0.2 to 3 g / 10 min. If the MFR value deviates from the above range, it may become impossible to manufacture the molded article in each manufacturing method (molding method).

[0073] There are no particular limitations on the method for adjusting the MFR value of the resin composition to the above range, but it is preferable to include an acid end-capping agent such as a carbodiimide compound (C). In particular, by including a polyfunctional acid end-capping agent and utilizing the chain extension reaction with the carboxyl group ends of the thermoplastic polyester elastomer resin (A), it is possible to adjust the MFR value to the above range. Furthermore, the reduced viscosity and acid value of the thermoplastic polyester elastomer resin (A), the type of acid end-capping agent such as a carbodiimide compound (C), the number of reactive groups thereof, the amount thereof, the increase in acid value due to the decomposition reaction of the thermoplastic polyester elastomer resin (A) by hydrolysis, etc., and the reactivity with other additives can be appropriately adjusted. Specifically, the reduced viscosity and acid value of the thermoplastic polyester elastomer resin (A) and the amount of acid end-capping agent in the resin composition can be increased to further reduce the MFR value. Furthermore, the greater the number of functionalities of the acid end-binding agent in the resin composition, the greater the decrease in MFR compared to the amount of the acid end-binding agent, but at the same time, the more likely it is to form gels. Therefore, the acid end-binding agent is preferably a polycarbodiimide compound, a bifunctional epoxy compound, or a bifunctional oxazoline compound, which do not form a branched structure and only have a linear chain extension effect.

[0074] The acid value of the resin composition is preferably 10 eq / ton or less, and more preferably 5 eq / ton or less. A value of 10 eq / ton or less in the resin composition reduces the number of carboxyl ends that promote hydrolysis of the polyester contained in the resin composition, resulting in excellent hydrolysis resistance of the resulting crosslinked molded article, which is preferable.

[0075] [Method for Manufacturing Resin Composition] The method for manufacturing the resin composition in the present invention is not particularly limited, but for example, it can be manufactured by melting and kneading each component using a known single-screw extruder, twin-screw extruder, kneader, Banbury mixer, roll, etc. Among these, it is preferable to use a twin-screw extruder from the viewpoint of kneadability, continuous productivity, and self-cleaning properties.

[0076] When using the aforementioned twin-screw extruder, it is preferable to appropriately select the extruder barrel temperature and screw configuration to control the shear stress, thermal history, and residence time applied to the polymer, thereby promoting kneading and reaction while suppressing polymer degradation and side reactions.

[0077] The melting temperature of the resin composition during the melt-kneading process is preferably 160 to 280°C, and more preferably 180 to 270°C. If the melting temperature is too low, melting will be insufficient, and unmelted gel is likely to form. If the melting temperature is too high, the resin composition is prone to thermal degradation.

[0078] The screw rotation speed during melt mixing is preferably 50 to 500 rpm, and more preferably 100 to 400 rpm. If the screw rotation speed is too low, the components contained in the resin composition may not melt and react uniformly, and if the screw rotation speed is too high, polymer degradation or side reactions may occur due to shear heat generation.

[0079] Furthermore, the discharge rate during melt-mixing is preferably 5 to 1,000 kg / h, and more preferably 10 to 500 kg / h. If the discharge rate is too low, there is a risk of uneven mixing and excessive heat retention due to a decrease in the resin filling rate in the extruder, while if the discharge rate is too high, the residence time in the extruder becomes too short, which may result in uneven mixing.

[0080] [Method for Manufacturing a Molded Article] The method for manufacturing a molded article in the present invention is not particularly limited, but for example, the resin composition obtained by the method for manufacturing the resin composition can be melt-kneaded to obtain a molded article (before crosslinking) by performing molding processes such as extrusion molding (extrusion film formation, T-die film formation, calender film formation, etc.), injection molding, compression molding, blow molding, etc., using a commonly used molding machine. In particular, in the method for manufacturing a molded article, it is preferable to use extrusion molding from the viewpoint of making it easier to apply a continuous crosslinking process in the crosslinking process described later.

[0081] [Method for Manufacturing a Crosslinked Molded Article] Next, regarding the method for manufacturing a crosslinked molded article, a crosslinked molded article can be obtained by performing a crosslinking step to crosslink the molded article. The obtained crosslinked molded article can be manufactured using a molding step and a crosslinking step to become a highly heat-resistant crosslinked molded article that maintains flexibility and mechanical properties as an elastomer material while simultaneously achieving hot rigidity and heat aging resistance in high-temperature environments.

[0082] The shape of the molded article (before crosslinking) used in the method for manufacturing the crosslinked molded article is not particularly limited, but can be selected according to the molding method, and may be one-dimensional (e.g., linear, rod-shaped, etc.), two-dimensional (e.g., sheet-shaped, film-shaped, etc.), or three-dimensional (e.g., a shape having recesses, protrusions, uneven surfaces, tube shape, hose shape, wire coating shape, etc.).

[0083] (Crosslinking process) The method for manufacturing a crosslinked molded article of the present invention preferably includes a crosslinking process in addition to the molding process such as extrusion molding. By performing the crosslinking process, it is possible to provide a crosslinked molded article that possesses high heat resistance while maintaining mechanical properties in addition to the flexibility of an elastomer material, making it useful.

[0084] The aforementioned crosslinking process refers to a process of forming a crosslinked structure in the thermoplastic polyester elastomer resin (A), and examples of such crosslinking processes include thermal crosslinking, silane crosslinking, and electron beam crosslinking.

[0085] The aforementioned thermal crosslinking is generally performed by incorporating organic oxides or the like into a polymer material and applying a thermal history under a pressurized environment to form a crosslinked structure.

[0086] The silane crosslinking method involves using an organic peroxide to graft vinylsilane onto the polymer constituting the thermoplastic polyester elastomer resin (A), adding a crosslinking promoting catalyst to the graft, melt-molding it, and then immersing it in hot water for an arbitrary amount of time to crosslink the polymer molecules.

[0087] The electron beam crosslinking method involves irradiating the polymer constituting the thermoplastic polyester elastomer resin (A) with an electron beam, and using radicals generated by the energy of the electron beam as a starting point to crosslink the polymer molecules with each other.

[0088] The present invention's method for producing a crosslinked molded article preferably includes an electron beam irradiation step as part of the crosslinking step. As described above, the crosslinked molded article is produced by first forming a molded article from the resin composition by extrusion molding or the like, and then irradiating it with an electron beam. By further irradiating the molded article obtained by the extrusion molding or the like with an electron beam, radicals (active sites) are generated and crosslinked (recombined) on the molecular chains of the polymer constituting the thermoplastic polyester elastomer resin (A), providing a crosslinked molded article that is not only flexible as an elastomer material but also possesses high heat resistance while maintaining mechanical properties, making it very useful. In particular, the electron beam irradiation crosslinking step (electron beam crosslinking) is preferred from the viewpoint of having an overwhelmingly short time required for the crosslinking reaction and excellent productivity.

[0089] The electron beam irradiation can be performed using a known electron beam irradiation apparatus. The conditions for the electron beam irradiation depend on the thickness of the uncrosslinked molded body in the direction of electron beam irradiation, but the following general conditions (acceleration voltage, irradiation dose, etc. during electron beam irradiation) can be exemplified.

[0090] The acceleration voltage during electron beam irradiation is a parameter that affects the thickness through which the electron beam penetrates. The preferred setting for the acceleration voltage varies depending on the thickness and specific gravity of the sample, but generally, a range of 10 kV to 10,000 kV is preferred, 50 kV to 5,000 kV is more preferred, and 100 kV to 1,500 kV is even more preferred. If the acceleration voltage of the electron beam is low, the electron beam penetration capability in the thickness direction parallel to the electron beam irradiation direction becomes small, so the crosslinking reaction by electron beam irradiation is limited to the surface of the crosslinked molded product obtained by extrusion molding or the like, and the effect of the crosslinking reaction of the resulting crosslinked molded product is limited. On the other hand, if the acceleration voltage is high, the size of the irradiation device becomes unnecessarily large, which is undesirable from the viewpoint of manufacturing costs.

[0091] The irradiation dose during electron beam irradiation is an indicator of the amount of energy irradiated and is a parameter that depends on the degree of crosslinking (gel fraction) after irradiation. The irradiation dose (total irradiation dose) is preferably 100 kGy to 3,000 kGy, more preferably 150 kGy to 2,000 kGy, even more preferably 300 kGy to 1,500 kGy, and particularly preferably 500 kGy to 1,500 kGy. If the irradiation dose is insufficient, the crosslinking effect on the main chain of the polymer constituting the thermoplastic polyester elastomer resin (A) will be insufficient, and the heat resistance improvement effect of the resulting crosslinked molded article will not be sufficiently obtained. On the other hand, if the irradiation dose is excessively high, it will have a large impact on the decomposition reaction of the main chain of the polymer constituting the thermoplastic polyester elastomer resin (A), which may result in a decrease in the heat aging resistance, flexibility, and elongation at break of the resulting crosslinked molded article, as well as yellowing of the resulting crosslinked molded article. Furthermore, in order to suppress heat generation during irradiation and deformation and shrinkage of the associated cross-linked molded body, the electron beam irradiation is preferably performed repeatedly at a low irradiation dose. For example, the irradiation dose per session is preferably 200 kGy or less, more preferably 150 kGy or less, and even more preferably 100 kGy or less.

[0092] As a method to promote crosslinking other than increasing the electron beam irradiation dose, for example, compounds having unsaturated bonds, such as triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylallyl cyanurate, trimethylallyl isocyanurate, and triallylphenyl cyanurate, can be included in the resin composition as crosslinking aids to promote crosslink formation. This makes it possible to improve the degree of crosslinking (gel fraction) of the resulting crosslinked molded article even with the same electron beam irradiation dose. On the other hand, there are concerns that the use of the crosslinking aids in high-temperature environments may result in bleed-out of the crosslinking aids.

[0093] Another method for promoting crosslinking, other than adding the aforementioned crosslinking aid, is to reduce the content of the antioxidant. In the aforementioned crosslinking by electron beam irradiation, the crosslinking reaction proceeds starting from radicals generated by the energy of the electron beam, but the antioxidant may hinder crosslinking by capturing these radicals. Therefore, by reducing the content of the antioxidant, an improvement in the degree of crosslinking (gel fraction) of the resulting crosslinked molded article can be expected. On the other hand, reducing the content of the antioxidant reduces the amount of antioxidant remaining in the crosslinked molded article after crosslinking, which reduces its contribution to improving the heat aging resistance of the crosslinked molded article and is therefore undesirable.

[0094] Furthermore, as a method for promoting crosslinking other than reducing the content of the antioxidant, for example, a method containing the carbodiimide compound (C) can be mentioned. Compared to a resin composition that does not contain the carbodiimide compound (C), the resin composition containing the carbodiimide compound has a higher degree of crosslinking (gel fraction) and a higher storage modulus E' above the melting point of the thermoplastic polyester elastomer resin (A), and crosslinking is more easily promoted. In addition, by including the carbodiimide compound (C), it is possible to increase the degree of crosslinking (gel fraction) of the resulting crosslinked molded article, and the effect of improving heat aging resistance due to the carbodiimide compound (C) can also be obtained. Unlike the method of reducing the content of the antioxidant, the inclusion of the carbodiimide compound (C) is preferable and very useful because there is no trade-off between the heat aging resistance and the degree of crosslinking of the crosslinked molded article.

[0095] The crosslinked molded article may be a crosslinked molded article using only the resin composition, or it may be a composite crosslinked molded article formed by bonding (or joining) a member (crosslinked molded article) made of the resin composition and a member (crosslinked molded article) made of a resin composition containing other resins. Furthermore, the composite crosslinked molded article may be directly bonded (fused) between the members without an adhesive (layer) in between.

[0096] The cross-linked molded article of the present invention preferably has an elongation at break (absolute value) of 200% or more, more preferably 250% or more, even more preferably 300% or more, and particularly preferably 350% or more, as measured in accordance with JIS K6251. When the elongation at break satisfies the above range, the cross-linked molded article has excellent flexibility, toughness, and retention of elongation at break after heat treatment. On the other hand, if the elongation at break is smaller than the above range, the toughness and retention of elongation at break after heat treatment of the cross-linked molded article tend to decrease.

[0097] In order for the elongation at severance to satisfy the range, it is preferable to adjust the mass ratio (mass%) of the hard segments and soft segments constituting the thermoplastic polyester elastomer resin (A) to hard segments:soft segments = 20:80 to 85:15, more preferably 25:75 to 80:20, even more preferably 30:70 to 75:25, particularly preferably 30:70 to 65:35, and most preferably 30:70 to 60:40. It is also preferable to employ means such as including the carbodiimide compound (C) in order for the elongation at severance to satisfy the range. Furthermore, when the mass ratio of the hard segment component is greater than 65% by mass, when the content of the flame retardant (B) is high, or when the degree of crosslinking of the crosslinked molded article is high, the elongation at severance of the crosslinked molded article tends to be low. Therefore, by setting the mass ratio of the hard segment component to 65% by mass or less, the elongation at severance of the crosslinked molded article can be improved, making it easier to obtain a crosslinked molded article with excellent flexibility and toughness. Furthermore, the elongation at break of the cross-linked molded article also depends on the manufacturing method (molding process) of the cross-linked molded article. For example, in injection molding, which has a high shear rate, the shear orientation of the resin composition in the cross-linked molded article tends to be pronounced, and the elongation at break tends to be small. Therefore, among the manufacturing methods (molding processes) of the cross-linked molded article, it is preferable to use extrusion molding or blow molding, which have a relatively low shear rate and do not cause resin orientation.

[0098] The crosslinked molded article of the present invention has a storage modulus E' at 220°C of 1.0 × 10⁻¹⁴, as determined by dynamic viscoelasticity measurement in accordance with JIS K7244. ５ It is preferable that the pressure be Pa or higher, and 2.0 × 10５ Pa or higher is more preferable, 5.0 × 10 ５ Pa or higher is even more preferable, 1.0 × 10 ６ A value of Pa or higher is particularly preferred. Here, the storage modulus E' is a value obtained by dynamic viscoelasticity measurement in accordance with JIS K7244, and can be rephrased as an indicator of stiffness at that temperature. When the storage modulus E' satisfies the above range, a crosslinked molded article can be obtained that has excellent hot stiffness in the temperature range above the melting point of the thermoplastic polyester elastomer resin (A), as well as excellent heat aging resistance in the temperature range below the melting point of the thermoplastic polyester elastomer resin (A). Furthermore, if the storage modulus E' is smaller than the above range, it effectively means that there is no hot stiffness at 220°C, and the shape cannot be maintained due to melt softening.

[0099] For the storage modulus E' of the crosslinked molded article to satisfy the above range, for example, the gel fraction (insoluble matter) after heat-treating the crosslinked molded article in N-methyl-2-pyrrolidone (NMP) at 150°C for 3 hours is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more. The gel fraction is an indicator of the amount of crosslinking formed in the resulting crosslinked molded article, and by setting the gel fraction to be above the above range, it becomes possible to maintain its rigidity even in a temperature environment above the melting point where the thermoplastic polyester elastomer resin (A) would normally melt and soften, which is useful.

[0100] For the gel fraction of the crosslinked molded article of the present invention to satisfy the above range, it is necessary to form a crosslinked structure. As described above, examples of means for forming a crosslinked structure in the thermoplastic polyester elastomer resin (A) include thermal crosslinking, silane crosslinking, and electron beam crosslinking. While these means for forming the crosslinked structure are not particularly limited, electron beam crosslinking is preferred from the viewpoint of having an overwhelmingly short time required for the crosslinking reaction and excellent productivity.

[0101] The crosslinked molded article of the present invention preferably has an elongation at break (absolute value) of 80% or more, more preferably 100% or more, and even more preferably 200% or more, after heat treatment at 190°C for 240 hours, as measured in accordance with JIS K6251. Having the elongation at break (absolute value) at 190°C for 240 hours within the above range is preferable because it does not crack or break even when used in the elastic deformation region after heat treatment, and exhibits excellent flexibility and heat resistance.

[0102] Furthermore, the crosslinked molded article of the present invention preferably has an elongation at break (absolute value) of 80% or more, more preferably 100% or more, and even more preferably 200% or more, after heat treatment at 200°C for 240 hours, as measured in accordance with JIS K6251. Having the elongation at break (absolute value) after heat treatment at 200°C for 240 hours within the above range is preferable because it does not crack or break even when used in the elastic deformation region after heat treatment, and exhibits excellent flexibility and heat resistance.

[0103] In order for the elongation at break (absolute value) of the cross-linked molded article of the present invention after heat treatment at 190°C for 240 hours, as measured in accordance with JIS K6251, to satisfy the above range, it is preferable that the mass ratio of hard segments and soft segments of the thermoplastic polyester elastomer resin (A) be hard segment:soft segment = 20:80 to 85:15, more preferably 25:75 to 80:20, even more preferably 30:70 to 75:25, particularly preferably 30:70 to 65:35, and most preferably 30:70 to 60:40. It is also preferable to employ means such as including a carbodiimide compound (C). If the resin composition contains a large amount of the flame retardant (B), it becomes difficult to maintain the elongation at break after heat treatment of the cross-linked molded article. Therefore, by setting the mass ratio of the hard segment component of the thermoplastic polyester elastomer resin (A) to 65% by mass or less, it becomes easier to satisfy the conditions for elongation at break after heat treatment. However, if the mass ratio of the hard segment component is set even lower (for example, to less than 50% by mass), the melting point of the thermoplastic polyester elastomer resin (A) may fall below 190°C. Therefore, in order to maintain the elongation at break after heat treatment at 190°C for 240 hours, a gel fraction of 30% by mass or more is required to exhibit sufficient hot rigidity above the melting point of the thermoplastic polyester elastomer resin (A). When the elongation at break after heat treatment at 190°C satisfies the above range, it becomes easier to obtain a cross-linked molded article with excellent heat aging resistance that does not crack or break even when used in the elastic deformation region after heat treatment. Furthermore, the elongation at break of the cross-linked molded article also depends on the manufacturing method (molding method) of the cross-linked molded article. In injection molding, which has a high shear rate, the shear orientation of the resin in the cross-linked molded article tends to be significant, and the elongation at break tends to be small. For this reason, among the manufacturing methods (molding methods) of the cross-linked molded article, it is preferable to use extrusion molding or blow molding, which have a relatively low shear rate and do not cause resin orientation. Furthermore, the elongation at break after heat treatment of the cross-linked molded article also depends on the thickness of the cross-linked molded article, which is preferably 0.01 mm to 1 mm, more preferably 0.02 mm to 0.5 mm, and even more preferably 0.05 mm to 0.4 mm.If the thickness is smaller than the range, the contribution of thickness variations becomes larger, which is undesirable because it leads to greater variation in elongation at cutting. Also, if the thickness is larger than the range, (especially when the hard segment mass ratio is high) crystallization due to heat treatment is more likely to progress in the internal layers other than the surface layer of the cross-linked molded body (such as the center), which tends to cause a decrease in elongation at cutting.

[0104] The tensile strength of the crosslinked molded article of the present invention (in sheet form with a thickness of 0.2 mm) is preferably 20 MPa or more, more preferably 30 MPa or more, and even more preferably 40 MPa or more, from the viewpoint of mechanical properties and heat aging resistance. Here, tensile strength is a value obtained by a tensile test in accordance with JIS K6251:2010, and can be rephrased as an indicator of the mechanical strength of the crosslinked molded article.

[0105] The crosslinked molded article of the present invention is a highly heat-resistant crosslinked molded article that maintains the flexibility and mechanical properties of an elastomer material while simultaneously achieving both hot rigidity in high-temperature environments (e.g., 220°C) and heat aging resistance in high-temperature environments (e.g., 190°C). Preferably, heat aging resistance is achieved at 190°C, and more preferably at 190-200°C.

[0106] The crosslinked molded article of the present invention can be applied to a wide range of applications, such as various components of electrical products, hoses, tubes, and cable coverings. Furthermore, it can be expanded into various molded products obtained by molding methods such as injection molding, extrusion molding, transfer molding, and blow molding.

[0107] Examples are given below to demonstrate the effects of the present invention, but the present invention is not limited in any way by these examples. The characteristic values ​​described in the examples were measured by the following methods.

[0108] [Melting Point] Using a differential scanning calorimetry analyzer "DSC220" manufactured by Seiko Electronics Industries, Ltd., the obtained polyester elastomer (thermoplastic polyester elastomer resin) was used as the measurement sample. 5 mg of this sample was placed in an aluminum pan, sealed by pressing down on the lid, and held at 250°C for 5 minutes to completely melt the sample. After rapid cooling with liquid nitrogen, the temperature was measured from -150°C to 250°C at a heating rate of 20°C / min. From the obtained thermogram curve, the endothermic peak temperature was defined as the melting point (°C).

[0109] [Reduced Viscosity] The obtained polyester elastomer (thermoplastic polyester elastomer resin) was used as the measurement sample. 0.05 g of this was dissolved in 25 mL of a mixed solvent (phenol / tetrachloroethane = 60 / 40 (mass ratio)), and the reduced viscosity (dl / g) was measured at 30°C using an Ostwald viscometer.

[0110] [Acid Value] The acid value (eq / ton) was determined by dissolving 200 mg of the obtained polyester elastomer (thermoplastic polyester elastomer resin), which was thoroughly dried (conditions: vacuum drying at 100°C for 8 hours), in 10 mL of hot benzyl alcohol. After the resulting solution was cooled, 10 mL of chloroform and phenol red were added, and the solution was titrated with a 1 / 25 N potassium alcohol solution (methanol solution of KOH) using a dissolution titration method. The acid value of the resin composition was also determined using the same measurement method.

[0111] [Shore D Hardness] The obtained polyester elastomer (thermoplastic polyester elastomer resin) was used as the measurement sample, and its hardness was measured using a Type D durometer in accordance with JIS K6253:2012. The value was read 15 seconds after the pressure plate was brought into contact with the test piece.

[0112] [Synthesis of Thermoplastic Polyester Elastomer Resin (A)] (Polyester Elastomer (A-1): Polycarbonate Ester Type) 100 parts by mass of aliphatic polycarbonate diol (UH-CARB200, manufactured by Ube Industries, Ltd., number average molecular weight 2000, 1,6-hexanediol type) and 8.9 parts by mass of diphenyl carbonate were charged and reacted at a temperature of 205°C and 130 Pa. After 2 hours, the contents were cooled to obtain aliphatic polycarbonate diol (number average molecular weight 12000). Sixty parts by mass of this aliphatic polycarbonate diol (PCD) and forty parts by mass of polybutylene terephthalate (PBT) having a number average molecular weight of 30,000 were stirred for one hour at 230-245°C and 130 Pa. After confirming that the contents had become transparent, the contents were removed and cooled to produce polyester elastomer (A-1). The melting point of the polyester elastomer (A-1) was 177°C, the reduced viscosity was 0.89 dl / g, the acid value was 38 eq / ton, and the Shore D hardness was 38.

[0113] (Polyester Elastomer (A-2): Polycarbonate Ester Type) 100 parts by mass of aliphatic polycarbonate diol (UH-CARB200, manufactured by Ube Industries, Ltd., number average molecular weight 2000, 1,6-hexanediol type) and 8.9 parts by mass of diphenyl carbonate were charged and reacted at a temperature of 205°C and 130 Pa. After 2 hours, the contents were cooled to obtain aliphatic polycarbonate diol (number average molecular weight 12000). 43 parts by mass of this aliphatic polycarbonate diol (PCD) and 57 parts by mass of polybutylene terephthalate (PBT) having a number average molecular weight of 30000 were stirred for 1 hour at 230-245°C and 130 Pa. After confirming that the contents had become transparent, the contents were removed and cooled to produce polyester elastomer (A-2). The polyester elastomer (A-2) had a melting point of 207°C, a reduced viscosity of 1.21 dl / g, an acid value of 44 eq / ton, and a Shore D hardness of 50.

[0114] (Polyester Elastomer (A-3): Polycarbonate Ester Type) 100 parts by mass of aliphatic polycarbonate diol (UH-CARB200, manufactured by Ube Industries, Ltd., number average molecular weight 2000, 1,6-hexanediol type) and 8.6 parts by mass of diphenyl carbonate were charged and reacted at a temperature of 205°C and 130 Pa. After 2 hours, the contents were cooled to obtain aliphatic polycarbonate diol (number average molecular weight 10000). 30 parts by mass of this aliphatic polycarbonate diol (PCD) and 70 parts by mass of polybutylene terephthalate (PBT) having a number average molecular weight of 30000 were stirred for 1 hour at 230-245°C and 130 Pa. After confirming that the contents had become transparent, the contents were removed and cooled to produce polyester elastomer (A-3). The polyester elastomer (A-3) had a melting point of 212°C, a reduced viscosity of 1.20 dl / g, an acid value of 41 eq / ton, and a Shore D hardness of 60.

[0115] (Polyester elastomer (A-4): Polyether ester type) 100 parts by mass of dimethyl terephthalate (DMT, manufactured by SK Petrochemical), 59 parts by mass of 1,4-butanediol (1,4-BDO, manufactured by Mitsubishi Chemical), 96 parts by mass of polytetramethylene ether glycol (PTMG1500, number average molecular weight 1500, manufactured by Mitsubishi Chemical), 0.16 parts by mass of tetrabutyl titanate (TBT, manufactured by Nacalai Tesque), and 0.41 parts by mass of AO-330 (manufactured by ADEKA) were placed in an autoclave and the temperature was raised from room temperature to 225°C over 150 minutes to carry out a transesterification reaction. Then, the pressure inside the autoclave was gradually reduced and the temperature was further raised over 75 minutes to 245°C and below 0.9 Torr to carry out an initial condensation reaction. Furthermore, the polymerization reaction was carried out at 245°C for 80 minutes under conditions of 0.9 Torr or less to produce a polyester elastomer (A-4) with a hard segment / soft segment mass ratio of 53 / 47 (mass%). The melting point of the polyester elastomer (A-4) was 200°C, the reduced viscosity was 1.99 dl / g, the acid value was 33 eq / ton, and the Shore D hardness was 40.

[0116] (Polyester elastomer (A-5): Polyether ester type) 100 parts by mass of dimethyl terephthalate (DMT, manufactured by SK Petrochemical), 47 parts by mass of 1,4-butanediol (1,4-BDO, manufactured by Mitsubishi Chemical), 285 parts by mass of polytetramethylene ether glycol (PTMG1400, number average molecular weight 1400, manufactured by BASF), 0.30 parts by mass of tetrabutyl titanate (TBT, manufactured by Nacalai Tesque), and 0.76 parts by mass of AO-330 (manufactured by ADEKA) were charged into an autoclave and the temperature was raised from room temperature to 225°C over 150 minutes to carry out a transesterification reaction. Then, the pressure inside the autoclave was gradually reduced and the temperature was further raised over 75 minutes to 245°C and below 0.9 Torr to carry out an initial condensation reaction. Furthermore, the polymerization reaction was carried out at 245°C for 80 minutes under conditions of 0.9 Torr or less to produce a polyester elastomer (A-5) with a hard segment / soft segment mass ratio of 25 / 75 (mass%). The melting point of the polyester elastomer (A-5) was 160°C, the reduced viscosity was 2.50 dl / g, the acid value was 21 eq / ton, and the Shore D hardness was 30.

[0117] (Polyester elastomer (A-6): Polyether ester type) 100 parts by mass of dimethyl terephthalate (DMT, manufactured by SK Petrochemical), 61 parts by mass of 1,4-butanediol (1,4-BDO, manufactured by Mitsubishi Chemical), 67 parts by mass of polytetramethylene ether glycol (PTMG1400, number average molecular weight 1400, manufactured by BASF), 0.14 parts by mass of tetrabutyl titanate (TBT, manufactured by Nacalai Tesque), and 0.35 parts by mass of AO-330 (manufactured by ADEKA) were placed in an autoclave and the temperature was raised from room temperature to 225°C over 150 minutes to carry out a transesterification reaction. Then, the pressure inside the autoclave was gradually reduced and the temperature was further raised over 75 minutes to 245°C and below 0.9 Torr to carry out an initial condensation reaction. Furthermore, the polymerization reaction was carried out at 245°C for 80 minutes under conditions of 0.9 Torr or less to produce a polyester elastomer (A-6) with a hard segment / soft segment mass ratio of 62 / 38 (mass%). The melting point of the polyester elastomer (A-6) was 210°C, the reduced viscosity was 1.75 dl / g, the acid value was 50 eq / ton, and the Shore D hardness was 52.

[0118] [Flame retardants (B)] (B-1) PDBS-80 (brominated polystyrene, manufactured by Lanxess Corporation) (B-2) Twinkling Star (antimony trioxide, manufactured by Chugoku Kogyo Co., Ltd.) (B-3) ADEKA Stab FP-2500S (composite flame retardant of melamine pyrophosphate / piperazine pyrophosphate, D50: 10 μm, phosphorus concentration: 19% by mass, manufactured by ADEKA Corporation)

[0119] [Carbodiimide Compounds (C)] (C-1) Carbodilite HMV-15CA (Alicyclic polycarbodiimide, manufactured by Nisshinbo Chemical Co., Ltd.) (C-2) Stabaxol P (Aromatic polycarbodiimide, manufactured by Rhein Chemie Ltd.)

[0120] [Other Additives] (D-1) Nonflex DCD (4,4'-bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Ouchi Shinko Chemical Co., Ltd.) (D-2) Irganox 1010 (hindered phenol antioxidant, manufactured by BASF) (D-3) Irganox 1098 (hindered phenol antioxidant, manufactured by BASF) (D-4) Rasmit LG (dilauryl thiodipropionate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (D-5) Polyamide resin (polyamide 6 / 66 / 12) (relative viscosity 1.3, amine value 490 eq / t) (D-6) TAIC (triallyl isocyanurate, manufactured by Nippon Chemical Corporation)

[0121] [Examples 1-17 and Comparative Examples 1-21] According to the composition and content ratio of the resin compositions described in Tables 1 and 2, 100 parts by mass of thermoplastic polyester elastomer resin (A) was mixed with a flame retardant (B), a carbodiimide compound (C), an antioxidant (D) and a crosslinking aid (E) using a twin-screw extruder, and then dried under reduced pressure at 100°C for 8 hours to obtain the resin compositions. These resin compositions were extruded into sheet-shaped molded bodies with a width of 15 cm and a thickness of 0.2 mm using a single-screw extruder at a cylinder temperature (Tm + 20°C). The obtained sheet-shaped molded bodies were then crosslinked by electron beam irradiation at the irradiation doses described in Tables 3 to 5 to obtain sheet-shaped crosslinked molded bodies for each example and comparative example. The obtained resin compositions and crosslinked molded bodies were evaluated as follows.

[0122] [MFR] The melt flow rate (MFR: g / 10 min) of the resin composition was measured at 230°C and 2160 g in accordance with the test method (Method A) described in JIS K7210. A resin composition with a moisture content of 0.1% by mass or less was used for the measurement.

[0123] [Electron beam irradiation] The obtained sheet-shaped molded body (before crosslinking) was irradiated with an electron beam at an acceleration voltage of 300 kV and an electron beam irradiation dose of 100 kGy to obtain a predetermined absorbed dose, thereby obtaining a crosslinked molded body.

[0124] [Gel Fraction] Approximately 0.5 g of the obtained cross-linked molded body was wrapped in a 150-mesh wire mesh and immersed in 60 ml of NMP at 150°C for 3 hours. After removal, it was washed with acetone and completely dried at 100°C. Let (X) be the mass of the sample before NMP immersion, and (Y) be the mass of the sample after NMP immersion and complete drying. The gel fraction (mass%) was calculated using the following formula: Gel fraction (mass%) = [(Y) / (X)] × 100

[0125] [Elongation at Break and Tensile Strength] The obtained cross-linked molded body was used as a test specimen, and the elongation at break and tensile strength were measured in accordance with JIS K6251:2010. The test specimens were prepared by extruding the obtained resin composition using a single-screw extruder at a cylinder temperature (Tm + 20°C) to form a sheet-shaped molded body with a width of 15 cm and a thickness of 0.2 mm, then cross-linking by electron beam irradiation, and finally punching out a dumbbell-shaped No. 3 test specimen from the resulting sheet-shaped cross-linked molded body.

[0126] [Heat aging resistance] The dumbbell-shaped test piece No. 3 was left for 240 hours in an air environment at 190°C or 200°C, then removed, and the elongation at break (%) was measured in accordance with JIS K6251:2010 as described above.

[0127] [Storage Modulus] The obtained cross-linked molded body was used as a test specimen, and the dynamic viscoelasticity was measured in tensile mode using a Rheogel-E4000 dynamic viscoelasticity measuring device (manufactured by UBM Co., Ltd.) in accordance with the test standard JIS K7244, under the following conditions to confirm the temperature dependence of the storage modulus E' and evaluate the storage modulus E' (Pa) at 220°C. Measurement temperature range: 23°C to 300°C Heating rate: 4°C / min Measurement frequency: 10 Hz

[0128] [Short-term heat resistance: Hot rigidity at 220°C] The obtained cross-linked molded body was used as a test specimen and placed in a hot air circulating oven set to 220°C for 5 minutes. After removing the test specimen from the oven, its appearance was visually inspected and judged according to the following criteria. In the cases of "○" and "◎" below, it was judged to be at a level that does not pose a practical problem. ×: The test specimen melted after the test and did not maintain its shape from before the test. ○: The test specimen did not melt after the test and maintained its shape from before the test. ◎: The test specimen did not melt after the test and maintained its shape from before the test. Furthermore, no hole was made when a 220°C soldering iron was pressed against the removed test specimen.

[0129] Tables 1 and 2 show the composition of the resin compositions used in the preparation of the crosslinked molded articles in Examples 1 to 17 and Comparative Examples 1 to 21. Tables 3 to 5 show the evaluation results of the obtained resin compositions and crosslinked molded articles.

[0130]

[0131]

[0132]

[0133]

[0134]

[0135] As is clear from the results in Table 3, the crosslinked molded bodies of Examples 1 to 17 that satisfy the conditions of the present invention maintain the elongation at break after heat treatment at 190 ° C. × 240 h and have excellent heat aging resistance. Particularly, in Examples 1 to 16, it was confirmed that even after heat treatment at 200 ° C. × 240 h, the elongation at break was maintained and excellent heat aging resistance was exhibited. Further, the storage elastic modulus at 220 ° C. is 1.0 × 10 ５ Pa or more, which is originally above the melting point of the thermoplastic polyester elastomer resin (A) to be used, and it was confirmed that the shape can be maintained even in an environment of 220 ° C. where the shape of the obtained crosslinked molded body cannot be maintained, and it has excellent hot rigidity.

[0136] Particularly, from the comparison between Example 2 and Example 7, in Example 7 containing the carbodiimide compound (C), the gel fraction is high and the storage elastic modulus is 1.0 × 10 ６ Pa or more and shows a tendency to be one order higher. Also, from the whole of Table 3, in Examples 1 to 6 not containing the carbodiimide compound (C), the storage elastic modulus is less than 1.0 × 10 ６ Pa, whereas in Examples 7 to 17 containing the carbodiimide compound (C), all are 1.0 × 10 ６The storage modulus was above Pa, confirming that crosslinking could proceed favorably. It is speculated that one factor contributing to this favorable crosslinking is the increase in the molecular weight before crosslinking due to the chain extension effect of the polycarbodiimide compound (C). On the other hand, since Examples 1 and 9, which have low molecular weights and high MFR values, showed storage moduli comparable to those of the other examples, it is suggested that the contribution of the chain extension effect is limited, and that the presence of the carbodiimide compound (C) facilitates the formation of crosslinked structures, resulting in the expression of high storage moduli.

[0137] Furthermore, when a resin composition containing a large amount of flame retardant is crosslinked, the elongation at cleavage of the resulting crosslinked molded article tends to decrease, and if heat aging treatment is applied, the elongation decreases even further. In fact, in Example 10, although the elongation at cleavage is at a level that is not problematic for practical use, a decrease is observed compared to Example 1, which does not contain a flame retardant. In contrast, in Examples 9 and 11-17, in which the mass ratio of soft segments in the thermoplastic polyester elastomer resin (A) satisfies 35-70% by mass, although they contain a large amount of flame retardant, similar to Example 10, it was confirmed that the elongation at cleavage after heat treatment at 190°C for 240 hours exhibited superior properties.

[0138] On the other hand, it was confirmed that the crosslinked molded articles of Comparative Examples 1 to 10, which did not satisfy the conditions of the present invention, showed inferior results compared to the examples in terms of elongation at break (heat aging resistance) after heat treatment at 190°C for 240 hours, and / or hot stiffness at 220°C. Specifically, Comparative Examples 1 to 11, 13, 15 and 16, which were not irradiated with electron beams, and Comparative Examples 12 and 14, which were irradiated with electron beams but with insufficient irradiation (100 kGy), had a storage modulus of 1.0 × 10⁻⁶ at 220°C. ４It was confirmed that the Pa was less than 220°C, and that the hot stiffness (including maintaining its shape) at 220°C could not be satisfied. Furthermore, comparative examples 16 to 21, in which the soft segments of the thermoplastic polyester elastomer resin (A) are formed from aliphatic polyether, tended to exhibit a higher gel fraction compared to the examples, and depending on the electron beam irradiation dose, some had good storage modulus and hot stiffness at 220°C. However, mechanical properties such as elongation at break (heat aging resistance) after heat treatment at 190°C for 240 hours were significantly reduced, and it was confirmed that the elongation at break after heat treatment at 200°C for 240 hours also decreased.

[0139] According to the present invention, it is possible to provide a highly heat-resistant crosslinked molded article that maintains the flexibility and mechanical properties of an elastomer material while simultaneously achieving both hot rigidity in high-temperature environments of up to 220°C and heat aging resistance in high-temperature environments of around 190°C. Furthermore, the crosslinked molded article of the present invention can be applied to a wide range of applications, such as various components of electrical products, and covering materials for hoses, tubes, and cables. In addition, it can be applied to various molded products obtained by injection molding, extrusion molding, transfer molding, blow molding, etc.

Claims

1. A crosslinked molded article characterized by being obtained by crosslinking a resin composition comprising a thermoplastic polyester elastomer resin (A) in which a hard segment formed from a polyester comprising an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol is bonded to a soft segment formed from an aliphatic polycarbonate.

2. The elongation at break (absolute value) measured in accordance with JIS K6251 is 200% or more, and the storage modulus E' at 220°C obtained by dynamic viscoelasticity measurement in accordance with JIS K7244 is 1.0 × 10⁻⁶. ５ The crosslinked molded article according to claim 1, characterized in that the pressure is Pa or higher.

3. The crosslinked molded article according to claim 1, characterized in that the gel fraction is 30% by mass or more.

4. The cross-linked molded article according to claim 1, characterized in that the elongation at break (absolute value) after heat treatment at 190°C for 240 hours, measured in accordance with JIS K6251, is 80% or more.

5. The crosslinked molded article according to claim 1, characterized in that the thermoplastic polyester elastomer resin (A) contains 30 to 75% by mass of the hard segment and 25 to 70% by mass of the soft segment.

6. The crosslinked molded article according to claim 1, characterized in that the resin composition contains a flame retardant (B).

7. The crosslinked molded article according to claim 1, characterized in that the resin composition contains a carbodiimide compound (C).

8. The crosslinked molded article according to claim 1, wherein the resin composition further contains a flame retardant (B) and a carbodiimide compound (C), and the thermoplastic polyester elastomer resin (A) contains 30 to 65% by mass of the hard segment and 35 to 70% by mass of the soft segment.

9. A method for manufacturing a crosslinked molded article according to any one of claims 1 to 8, characterized in that it includes a step by extrusion molding.

10. The method for producing a crosslinked molded article according to claim 9, further comprising the step of irradiating with an electron beam.

11. A coating material characterized by being obtained by a crosslinked molded article according to claims 1 to 8.

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