Composition for foam molding, foam molded article, foam wire, method for producing foam molded article, method for producing wire, and in-vehicle

Abstract

The present disclosure provides a foam molded body and a foam electric wire which can be suitably used as an electric wire for an in-vehicle network cable. A composition for foam molding, which is characterized by containing a fluororesin (A) and a compound (B) having a thermal decomposition temperature of 300 DEG C or higher and a solubility parameter (SP value) of 8-15, and which is used in the coating of an electric wire for an in-vehicle network cable.

Description

Technical Field

[0001] The present disclosure relates to a composition for foam molding, a foam molded article, a foam wire, a method for manufacturing a foam molded article, a method for manufacturing a wire, and a vehicle-mounted network cable. Background Art

[0002] Communication networks have been popularized in offices, homes, etc. In recent years, with the adoption of autonomous driving assistance systems, etc., the amount of communication data has increased. Along with this, an increase in communication speed is also required in vehicles, and the introduction of network cables capable of high-speed communication such as Ethernet (registered trademark) is being promoted.

[0003] Patent Document 1 describes a shielded twisted pair cable having: a twisted pair formed by twisting a pair of core wires insulatedly coated around signal conductors and a shielding wire, a conductor foil covering the outer periphery of the twisted pair, and an outer skin insulating layer covering the outer periphery of the conductor foil. The shielded twisted pair cable is characterized in that the twisted pair is formed by twisting at least two or more shielding wires.

[0004] Patent Document 2 discloses a wire for a vehicle-mounted network cable coated with a fluororesin.

[0005] Patent Document 3 discloses a composition for foam molding and a foam wire using a fluororesin.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-287948

[0009] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-158111

[0010] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2022-28640 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] An object of the present disclosure is to provide a foam molded article and a foam wire that can be suitably used as a wire for a vehicle-mounted network cable.

[0013] Means for Solving the Problems

[0014] The present disclosure is a composition for foam molding, characterized by containing a fluororesin (A) and a compound (B) having a thermal decomposition temperature of 300°C or higher and a solubility parameter SP value of 8 to 15, and being used for coating a wire for a vehicle-mounted network cable.

[0015] The above-mentioned compound (B) is preferably a compound containing at least one partial structure selected from the group consisting of an aromatic ring, a phosphate group, and an amide group.

[0016] The above-mentioned compound (B) is preferably a compound containing one or more C6-14 aromatic rings or a salt thereof.

[0017] The above-mentioned compound (B) is preferably at least one compound selected from the group consisting of phosphates and their salts, phosphate complex compounds, and compounds having two or more amide groups.

[0018] The salt of the above-mentioned compound (B) is preferably an alkali metal or an alkaline earth metal.

[0019] The above-mentioned compound (B) is preferably at least one of the compounds represented by the following formulas (1), (2), (3), and (4).

[0020]

[0021]

[0022] (In the formula, R1, R2, R3, R4, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34 , R 41 , R 42 represent a hydrogen atom, an alkyl or cycloalkyl group having 1 to 8 carbon atoms, or an aryl, alkylaryl, or aralkyl group having 6 to 12 carbon atoms, Ar 41 represents an aryl group, R5 and R6 represent a hydrogen atom or a methyl group, n represents an integer of 1 or 2, m represents an integer of 0 to 2, and X represents an m + n-valent metal.)

[0023] In formulas (1), (2), and (3), R1, R2, R 21 , R 22 , R 31 and R 33 are preferably alkyl groups having 1 to 8 carbon atoms.

[0024] In formulas (1), (2), and (3), X is preferably at least one of sodium, potassium, rubidium, calcium, and barium.

[0025] The above-mentioned compound (B) is preferably an aromatic cyclic phosphate salt represented by the above formula (1).

[0026] The above-mentioned compound (B) is preferably sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.

[0027] The above-mentioned fluororesin (A) is preferably a fluororesin capable of melt processing.

[0028] The above-mentioned fluororesin (A) is preferably at least one selected from the group consisting of tetrafluoroethylene / hexafluoropropylene copolymers, tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers, and tetrafluoroethylene / ethylene copolymers.

[0029] The above-mentioned fluororesin (A) is preferably a fluororesin subjected to fluorination treatment.

[0030] The foaming composition of the present disclosure preferably substantially does not contain fluorine-based low-molecular compounds.

[0031] The present disclosure also relates to a foamed molded article, which is characterized in that it is obtained from the above-mentioned foaming composition.

[0032] The above-mentioned foamed molded article preferably substantially does not contain fluorine-based low-molecular compounds.

[0033] The present disclosure is also a foamed wire for in-vehicle network cables, which is characterized by comprising a core wire and a covering material obtained from the above-mentioned foaming composition covering the core wire. The above-mentioned foamed wire preferably substantially does not contain fluorine-based low-molecular compounds.

[0034] The present disclosure is also a foamed wire for in-vehicle network cables, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has air bubbles. It is characterized in that, in a cross-sectional view perpendicular to the length direction, the average bubble diameter of the air bubbles is 20 μm to 40 μm.

[0035] The present disclosure is also a foamed wire for in-vehicle network cables, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has air bubbles. It is characterized in that, in a cross-sectional view parallel to the length direction, the average aspect ratio of the air bubbles is 1.9 or less.

[0036] The present disclosure is also a foamed wire for in-vehicle network cables, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has air bubbles. It is characterized in that, in a cross-sectional view parallel to the length direction, the proportion of air bubbles with an aspect ratio of 3 or more relative to the total amount of air bubbles measured in the cross-sectional view parallel to the length direction is 13% or less.

[0037] The present disclosure also relates to a foamed wire for an in-vehicle network cable, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has bubbles. It is characterized in that, when observed in a cross-section parallel to the longitudinal direction, the standard deviation of the aspect ratio of the bubbles is 1.3 or less.

[0038] The present disclosure also relates to a foamed wire for an in-vehicle network cable, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has bubbles. It is characterized in that the foaming ratio is 20% or more and the surface roughness is less than 5.0 μm.

[0039] The present disclosure also relates to a foamed wire for an in-vehicle network cable, which has a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, and the fluororesin layer or the fluororesin composition layer has bubbles. It is characterized in that the structure of the wire is a foam / skin structure with the foam on the inside and the skin on the outside.

[0040] The present disclosure also relates to a method for manufacturing a foamed molded body, which is characterized by including a step of foaming and molding the above-mentioned foaming composition for molding.

[0041] The present disclosure also relates to a method for manufacturing a wire, which is characterized by including a step of covering a core wire with the above-mentioned foaming composition for molding to obtain a wire.

[0042] The present disclosure also relates to an in-vehicle network cable, which is characterized by including the above-mentioned foamed wire for an in-vehicle network cable.

[0043] Preferably, the above-mentioned in-vehicle network cable includes: a twisted pair cable having a pair of wires twisted together; at least one of the pair of wires is the above-mentioned foamed wire for an in-vehicle network cable.

[0044] For the above-mentioned in-vehicle network cable, preferably, in the twisted pair cable, the deformation rate after twisting of the foamed wire is 20% or less. Detailed Description

[0045] The present disclosure has been completed based on the following finding: By using a specific compound (B) in a foaming resin having a fluorine-based polymer as a matrix resin, good foaming can be obtained, which is particularly suitable for wires for in-vehicle network cables.

[0046] The thermal decomposition temperature of the compound (B) is 300 °C or higher, and the solubility parameter (SP value) is 8 to 15. Most of the existing foaming nucleating agents have relatively low thermal decomposition temperatures and melting points. In the case where the molding temperature of the resin is low, there is no problem even so, but in a molding composition containing a resin having a high melting point, there are the following problems: thermal decomposition or melting occurs during molding, and it cannot effectively function as a foaming nucleating agent. In particular, in the case of using a fluororesin as a high melting point resin, there will be adverse conditions such as coloring, generation of decomposition gases, huge bubble size, poor surface state, and poor electrical properties, and it is difficult to balance the physical properties of the fluororesin and the properties as a foamed molded body.

[0047] The present disclosure has found that by using the compound (B), a composition containing the fluororesin (A) exhibits good foamability, and further, good properties are also exhibited when molding is performed at a high temperature, whereby the above effects can be obtained.

[0048] The present disclosure will be described in detail below.

[0049] The fluororesin (A) is not particularly limited as long as it can be melt-processed, and examples thereof include tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymers, TFE / perfluoro(alkyl vinyl ether) (PAVE) copolymers, TFE / ethylene copolymers [ETFE], chlorotrifluoroethylene (CTFE) / ethylene copolymers [ECTFE], polyvinylidene fluoride [PVdF], polychlorotrifluoroethylene [PCTFE], TFE / vinylidene fluoride (VdF) copolymers [VT], polyvinyl fluoride [PVF], TFE / VdF / CTFE copolymers [VTC], TFE / ethylene / HFP copolymers, TFE / HFP / VdF copolymers, etc.

[0050] As the above PAVE, examples include perfluoro(methyl vinyl ether) [PMVE], perfluoro(ethyl vinyl ether) [PEVE], perfluoro(propyl vinyl ether) [PPVE], etc. Among them, PPVE is preferred. One or more of them can be used.

[0051] The fluororesin may have polymerization units based on other monomers in an amount within a range that does not impair the essential properties of each fluororesin. As the above other monomers, for example, they can be appropriately selected from TFE, HFP, ethylene, propylene, perfluoro(alkyl vinyl ether), perfluoroalkyl ethylene, hydrofluoroolefin, fluoroalkyl ethylene, perfluoro(alkyl allyl ether), etc. As the perfluoroalkyl group constituting the above other monomers, a perfluoroalkyl group having 1 to 10 carbon atoms is preferred.

[0052] Due to its excellent heat resistance, the fluororesin is preferably a TFE / HFP copolymer, a TFE / PAVE copolymer, or a TFE / ethylene copolymer, more preferably a TFE / HFP copolymer or a TFE / PAVE copolymer. Two or more of the above fluororesins can also be used in combination. In addition, due to its more excellent electrical properties, a perfluororesin is also preferred.

[0053] In the TFE / HFP copolymer, the mass ratio of TFE / HFP is preferably 80 to 97 / 3 to 20, more preferably 84 to 92 / 8 to 16.

[0054] The TFE / HFP copolymer can be a binary copolymer composed of TFE and HFP. Furthermore, it can also be a terpolymer including a comonomer capable of copolymerizing with TFE and HFP (for example, a TFE / HFP / PAVE copolymer).

[0055] The TFE / HFP copolymer is also preferably a TFE / HFP / PAVE copolymer containing a polymerization unit based on PAVE.

[0056] In the TFE / HFP / PAVE copolymer, the mass ratio of TFE / HFP / PAVE is preferably 70 to 97 / 3 to 20 / 0.1 to 10, more preferably 81 to 92 / 5 to 16 / 0.3 to 5.

[0057] In the TFE / PAVE copolymer, the mass ratio of TFE / PAVE is preferably 90 to 99 / 1 to 10, more preferably 92 to 97 / 3 to 8.

[0058] In the TFE / ethylene copolymer, the molar ratio of TFE / ethylene is preferably 20 to 80 / 20 to 80, more preferably 40 to 65 / 35 to 60. In addition, the TFE / ethylene copolymer can also contain other monomer components.

[0059] That is, the TFE / ethylene copolymer can be a binary copolymer composed of TFE and ethylene. Furthermore, it can also be a terpolymer including a comonomer capable of copolymerizing with TFE and ethylene (for example, a TFE / ethylene / HFP copolymer).

[0060] The TFE / ethylene copolymer is also preferably a TFE / ethylene / HFP copolymer containing a polymerization unit based on HFP. In the TFE / ethylene / HFP copolymer, the molar ratio of TFE / ethylene / HFP is preferably 40 to 65 / 30 to 60 / 0.5 to 20, more preferably 40 to 65 / 30 to 60 / 0.5 to 10.

[0061] The melt flow rate (MFR) of the fluororesin is preferably from 0.1 g / 10 min to 500 g / 10 min. More preferably, it is from 4 g / 10 min to 100 g / 10 min, and further preferably from 10 g / 10 min to 80 g / 10 min. Since the generation of sparks can be suppressed and the foaming ratio becomes larger, it is thus even more preferably from 34 g / 10 min to 50 g / 10 min, and particularly preferably from 35 g / 10 min to 40 g / 10 min.

[0062] The above MFR is a value measured according to ASTM D-1238 using a die with a diameter of 2.1 mm and a length of 8 mm at a load of 5 kg and 372 °C.

[0063] The fluororesin can be synthesized by polymerizing monomer components using common polymerization methods such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, gas-phase polymerization, etc. In the above polymerization reaction, a chain transfer agent such as methanol may sometimes be used. It is also possible to carry out polymerization and separation without using a reagent containing metal ions, thereby manufacturing the fluororesin.

[0064] The fluororesin may have terminal groups such as -CF3, -CF2H, etc. at at least one site in the polymer main chain and the polymer side chain, without particular limitation, but a fluororesin treated with fluorination is preferred. An untreated fluororesin sometimes has terminal groups (hereinafter, such terminal groups are also referred to as "unstable terminal groups") that are unstable to thermal and electrical properties, such as -COOH, -CH2OH, -COF, -CONH2, etc. Such unstable terminal groups can be reduced by the above fluorination treatment. The fluororesin preferably has few or no such unstable terminal groups, and the total number of the above 4 unstable terminal groups and -CF2H terminal groups is more preferably 50 or less per 1×10 6 carbon atoms. If it exceeds 50, there may be molding defects. The above unstable terminal groups are more preferably 20 or less, and further preferably 10 or less. In this specification, the number of the above unstable terminal groups is a value obtained by infrared absorption spectroscopy measurement. It is also possible that there are no such unstable terminal groups and -CF2H terminal groups, and all are -CF3 terminal groups.

[0065] The above fluorination treatment can be carried out by bringing the untreated fluororesin into contact with a fluorine-containing compound.

[0066] There is no particular limitation for the above fluorine-containing compound, and a fluorine radical source that generates fluorine radicals under fluorination treatment conditions can be cited. As the above fluorine radical source, F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and fluorinated halogens (such as IF5, ClF3), etc. can be cited.

[0067] The above-mentioned fluorine radical sources such as F2 gas can be 100% concentrated F2 gas. However, from the perspective of safety, it is preferably diluted by mixing with an inert gas to 5% by mass to 50% by mass, preferably 15% by mass to 30% by mass for use. As the above-mentioned inert gas, nitrogen, helium, argon, etc. can be cited. From the economic aspect, nitrogen is preferred.

[0068] The conditions of the above-mentioned fluorination treatment are not particularly limited. The molten fluororesin can be brought into contact with a fluorine-containing compound. Generally, it can be carried out at a temperature below the melting point of the fluororesin, preferably 20°C to 220°C, more preferably 100°C to 200°C. The above-mentioned fluorination treatment is usually carried out for 1 hour to 30 hours, preferably 5 hours to 20 hours.

[0069] The above-mentioned fluorination treatment preferably makes the unfluorinated fluororesin contact with fluorine gas (F2 gas).

[0070] There is no particular limitation on the fluororesin (A). Since a foamed molded body with excellent heat resistance and a wide continuous use temperature range can be obtained, the melting point is preferably 200°C or higher, the molding temperature is 250°C or higher, and the thermal decomposition temperature is 300°C or higher. Further, the melting point is more preferably 250°C or higher and preferably 300°C or lower. The molding temperature is more preferably 300°C or higher and preferably 450°C or lower. The thermal decomposition temperature is more preferably 350°C or higher and further preferably 400°C or higher. As the upper limit of the melting point, molding temperature, and thermal decomposition temperature, it is 600°C or lower.

[0071] In this specification, the melting point is the temperature measured by a differential scanning calorimeter (DSC). The molding temperature is the temperature suitable for molding usually recommended, at which the resin has fluidity and does not cause resin deterioration such as coloring. The thermal decomposition temperature is the 1% weight loss temperature when heated in air at 10°C / min obtained by TG (measurement of heating weight change). Among them, the weight reduction amount caused by the volatilization of water or crystal water observed at 100°C to 200°C is not included. Having fluidity means that the MFR is 0.0001 or more at this temperature.

[0072] In order to reduce the signal loss of communication wires, the dielectric constant of the above-mentioned fluororesin (A) is preferably 3.0 or lower, further preferably 2.6 or lower, and most preferably 2.1 or lower. As the lower limit, it is 1.0 or higher. Similarly, the tangent of the dielectric loss angle is preferably 0.01 or lower, more preferably 0.001 or lower, and most preferably 0.0004 or lower. As the lower limit, it is 0.0001 or higher. The dielectric constant and the tangent of the dielectric loss angle are measured by the cavity resonator method at a frequency of 6 GHz.

[0073] The content of the above fluororesin (A) is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, further preferably 90 parts by mass or more, still more preferably 95 parts by mass or more, and particularly preferably 98 parts by mass or more, based on 100 parts by mass of the foam molding composition. As the upper limit, it is 99.999 parts by mass or less, more preferably 99.99 parts by mass or less.

[0074] In the present disclosure, the above compound (B) that functions as a foam nucleating agent is a compound having a thermal decomposition temperature of 300°C or higher and a solubility parameter (SP value) of 8 to 15.

[0075] In the present disclosure, in order to obtain a foam molding excellent in heat resistance and having a wide continuous use temperature range, the thermal decomposition temperature of the compound (B) needs to be 300°C or higher. The thermal decomposition temperature is more preferably 350°C or higher, and further preferably 400°C or higher. As the upper limit, it is preferably 600°C or lower.

[0076] The measurement of the thermal decomposition temperature can be carried out in the same manner as the above fluororesin (A).

[0077] In order to effectively exert the effects of the present disclosure, it is preferred that the compound (B) does not melt at the molding temperature. Therefore, the melting point of the compound (B) is preferably 200°C or higher, more preferably 300°C or higher, further preferably 350°C or higher, and most preferably 400°C or higher. The melting point of the compound (B) is the temperature that can be confirmed by the TGA peak during TG measurement. For example, when no peak can be confirmed below 400°C, it is considered to be 400°C or higher.

[0078] It is possible to confirm whether the compound melts at the peak temperature by observation using a heating microscope or an electric furnace.

[0079] In addition, the solubility parameter (SP value) of the above compound (B) is 8 to 15. By making the SP value within the above range, the additive particles can be uniformly dispersed, and uniform and fine foaming can be achieved. Furthermore, the following effects can be obtained: suppressing the generation of large particles due to particle re-aggregation during foam molding, reducing the unevenness on the wire surface caused by the large particles, and making the surface smooth.

[0080] The above SP value is preferably 9 or higher, more preferably 10 or higher. In addition, it is preferably 14 or lower, more preferably 13 or lower, and further preferably 12 or lower.

[0081] The above SP value can be calculated by Fedors' formula (Polym. Eng. Sci., 14[2], 147 (1974)).

[0082] The above-mentioned compound (B) is preferably a compound having a partial structure containing at least one selected from the group consisting of an aromatic ring, a phosphate group, and an amide group. For example, when the above-mentioned compound (B) contains an aromatic ring, it is preferably a compound having one or more C6-14 aromatic rings or a salt thereof.

[0083] When the above-mentioned compound (B) contains an amide group, it is preferably a compound having two or more amide groups. There is no particular limitation on such a compound. For example, a compound represented by the following formula (4) is preferred.

[0084]

[0085] (In the formula, R 41 , R 42 represent a hydrogen atom, an alkyl or cycloalkyl group having 1 to 8 carbon atoms, or an aryl, alkylaryl, or aralkyl group having 6 to 12 carbon atoms, and Ar 41 represents an aryl group.)

[0086] More specifically, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide (trade name: NJSTAR NU-100, Shin Nippon Rika Co., Ltd.) etc. can be mentioned.

[0087] When the above-mentioned compound (B) contains a phosphate group, it is preferably at least one compound selected from the group consisting of phosphates and their salts, and phosphate complex compounds. Representative phosphate compounds that can be used as the above-mentioned compound (B) are phosphates, phosphites, acidic phosphates, acidic phosphites, or salts thereof such as ammonia, amines, melamine, alkali metals, or alkaline earth metals, and their specific structures are not particularly limited.

[0088] As specific examples, there may be mentioned: triphenyl phosphate, trilauryl phosphate, tristearyl phosphate, trioleyl phosphate, xylene diphenyl phosphate, ethyl diphenyl phosphate, isopropyl diphenyl phosphate, n-butyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate, cetyl diphenyl phosphate, stearyl diphenyl phosphate, oleyl diphenyl phosphate, butyl xylenyl phosphate, octyl xylenyl phosphate, lauryl xylenyl phosphate, dibutyl pyrophosphate, monophenyl acid phosphate, diphenyl acid phosphate, monotolyl acid phosphate, xylenyl acid phosphate, monoxylenyl acid phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl(2-acryloyloxyethyl) phosphate, diphenyl(2-methacryloyloxyethyl) phosphate, trinaphthyl phosphate, trinonylphenyl phosphate, tris(2,6-dimethylphenyl) phosphate, tetraphenyl resorcinol diphosphate, tetraphenyl hydroquinone diphosphate, tetraphenyl bisphenol A diphosphate, tetrakis(2,6-dimethylphenyl) resorcinol diphosphate, tetrakis(2,6-dimethylphenyl) bisphenol A diphosphate, tetrakis(2,6-dimethylphenyl) biphenyl diphosphate, tetraphenyl ethylene glycol diphosphate, bis(2,6-dimethylphenyl) pentaerythritol diphosphate, bisxylenyl acid phosphate and other acidic phosphates, or acidic phosphites, dimethyl phosphate·ammonium salt, diethyl phosphate·ammonium salt, ethyl phosphate·ammonium salt, di-n-butyl phosphate·ammonium salt, dibutoxyethyl phosphate·triethanolamine salt, dioctyl phosphate·morpholine salt, mono-n-butyl phosphate·sodium salt, diphenyl phosphate·ammonium salt, diphenyl phosphate·melamine salt, diphenyl phosphate·piperazine salt, phenyl phosphate·ammonium salt, xylenyl phosphate·ethylenediamine salt, tolyl phosphate·sodium salt, bis(xylenyl) phosphate·melamine salt and other acidic phosphates, or salts of acidic phosphites such as ammonia, amine, melamine, alkali metal or alkaline earth metal salts.

[0089] More specifically, there may be mentioned salts of phosphates such as sodium bis(4-tert-butylphenyl) phosphate, sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, sodium salt of (2-hydroxy-2-oxo-4,6,10,12-tetra-tert-butyl-1,3,2-dibenzo[d,g]perhydrodioxaphosphocin, barium salt of bisphenol phosphate diester, sodium salt of binaphthyl phosphate diester, sodium bis(4-nitrophenyl) phosphate, etc. In addition, the ester may be a monoester, a diester, a triester, or an ester of tetraester or higher. They may be used alone or in combination of two or more.

[0090] Among them, aromatic phosphates are preferred, salts of aromatic phosphates are more preferred, and salts of aromatic phosphates having a cyclic structure are further preferred. Salts of cyclic phosphates having a biphenyl structure, a binaphthyl structure or a benzhydryl structure are more preferred. Among them, these benzene rings and naphthalene rings may have an alkyl or cycloalkyl group having 1 to 8 carbon atoms, or an aryl, alkylaryl or aralkyl group having 6 to 12 carbon atoms.

[0091] As the salt of the aromatic phosphate having the above cyclic structure, at least one of the aromatic cyclic phosphate salts represented by the following formulas (1), (2) and (3) is preferred.

[0092]

[0093]

[0094] In the formulas, R1, R2, R3, R4, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34 represent a hydrogen atom, an alkyl or cycloalkyl group having 1 to 8 carbon atoms, or an aryl, alkylaryl or aralkyl group having 6 to 12 carbon atoms, R5 and R6 represent a hydrogen atom or a methyl group, n represents an integer of 1 or 2, m represents an integer of 0 to 2, and X represents a metal having a valence of m + n.

[0095] As the alkyl groups represented by R1, R2, R3, R4, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34 shown, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl, tert-pentyl, hexyl, isohexyl, heptyl, octyl, isooctyl, 2-ethylhexyl, tert-octyl can be mentioned. As the cycloalkyl group, cyclopentyl, cyclohexyl, cycloheptyl and the like can be mentioned. Among them, an alkyl group having 1 to 4 carbon atoms and tert-butyl are preferred.

[0096] As R1, R2, R3, R4, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34Examples of the aryl group shown include a phenyl group, a naphthyl group, a biphenyl group, etc. Examples of the alkylaryl group include a 4-methylphenyl group, a 4-tert-butylphenyl group, a nonylphenyl group, etc. Examples of the arylalkyl group include a benzyl group, a phenethyl group, a cumenyl group, etc.

[0097] Examples of the metal shown as X include alkali metals such as lithium, sodium, potassium, rubidium, etc., alkaline earth metals such as magnesium, calcium, barium, etc., aluminum, zinc, titanium, etc. Among them, at least one of sodium, potassium, rubidium, calcium, and barium is preferred, and sodium or barium is more preferred.

[0098] Among them, the compound (B) is preferably the aromatic cyclic phosphate shown by the above formula (1), and more specifically, sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate shown by the following formula (5) is most preferred.

[0099]

[0100] The phosphate complex compound that can be used as the above-mentioned compound (B) is a complex composed of a metal and an organic compound having a phosphate group, and its specific structure is not particularly limited. Examples of the organic compound constituting the complex compound include bis(4,4’,6,6’-tetra-tert-butyl-2,2’-methylenediphenyl phosphate), 2,2’-methylenebis(4,6-di-tert-butylphenyl) phosphate, 2,2’-methylenebis(4,6-dimethylphenyl) phosphate, 2,2’-methylenebis(4,6-dimethylphenyl) phosphate, 2,2’-methylenebis(4,6-diethylphenyl) phosphate, 2,2’-methylenebis(4-methyl-6-tert-butylphenyl) phosphate, 2,2’-methylenebis(4-ethyl-6-tert-butylphenyl) phosphate, 2,2’-ethylenebis(4,6-di-tert-butylphenyl) phosphate, 2,2’-ethylenebis(4-isopropyl-6-tert-butylphenyl) phosphate, 2,2’-ethylenebis(4-m-butyl-6-tert-butylphenyl) phosphate, 2,2’-butylenebis(4,6-dimethylphenyl) phosphate, 2,2’-butylenebis(4,6-di-tert-butylphenyl) phosphate, 2,2’-tert-octylmethylenebis(4,6-dimethylphenyl) phosphate, 2,2’-tert-octylmethylenebis(4,6-di-tert-butylphenyl) phosphate, bis[2,2’-thiobis(4-ethyl-6-tert-butylphenyl) phosphate], bis[2,2’-thiobis(4,6-di-tert-butylphenyl) phosphate], bis[2,2’-thiobis-(4-tert-octylphenyl) phosphate], bis[2,2’-methylenebis(4,6-di-tert-butylphenyl) phosphate], bis[2,2’-ethylenebis(4,6-di-tert-butylphenyl) phosphate], bis[(4,4’-dimethyl-6,6’-di-tert-butyl-2,2’-biphenyl) phosphate], (4,4’-dimethyl-5,6’-di-tert-butyl-2,2’-biphenyl) phosphate, tris[2,2’-methylenebis(4,6-di-tert-butylphenyl) phosphate], tris[2,2’-ethylenebis(4,6-di-tert-butylphenyl) phosphate], phenyldidodecyl phosphate, phenylethyl hydrogen phosphate, phenylbis(3,5,5-trimethylhexyl) phosphate, ethyldiphenyl phosphate, 2-ethylhexyl bis(tolyl) phosphate, diphenyl hydrogen phosphate, methylenediphenyl phosphate, bis(2-ethylhexyl) p-tolyl phosphate, tricresyl phosphate, bis(2-ethylhexyl) phenyl phosphate, di(nonyl) phenyl phosphate, phenylmethyl hydrogen phosphate, bis(dodecyl) p-tolyl phosphate, p-tolylbis(2,5,5-trimethylhexyl phosphate, 2-ethylhexyl diphenyl phosphate, tris(butoxyethyl) phosphate, trioctyl phosphate, tritolyl phosphate, tolyl diphenyl phosphate, diethyl chlorophosphate, diphenyl chlorophosphate, diethyl bromophosphate, diphenyl bromophosphate, dimethyl chlorophosphate, phenyl chlorophosphate, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, tridecyl phosphate, triphenyl phosphate, isopropyl triphenyl phosphate, isodecyl diphenyl phosphate, methylene diphenyl phosphate, etc.,

[0101] In addition, examples of the metal constituting the phosphate complex compound include aluminum, sodium, lithium, calcium, magnesium, and barium. They can be used alone or in combination of two or more. Among them, aromatic phosphates are preferred, cyclic aromatic phosphates are more preferred, and sodium complex compounds of aromatic cyclic phosphates are most preferred.

[0102] In the above compound (B), as a compound having a melting point of 300 °C or higher, specifically, sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, etc. can be cited.

[0103] The content of the above compound (B) relative to the above fluororesin (A) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. Further preferably 5 parts by mass or less, still more preferably 2 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0104] The content of the above compound (B) relative to the above fluororesin (A) is preferably 0.001 parts by mass or more. More preferably 0.01 parts by mass or more.

[0105] If the content of the compound (B) is too small, it is difficult to obtain fine bubbles in the resulting coating material. If the content of the compound (B) is too large, there is a possibility of generating a large amount of sparks.

[0106] The foaming molding composition of the present disclosure may further contain boron nitride within a range that does not impair the effects of the present disclosure.

[0107] The average particle diameter of boron nitride is preferably 8.0 μm or more. In the past, the average particle diameter of boron nitride has tended to decrease, and the use of boron nitride having a larger average particle diameter has not been specifically studied.

[0108] By containing boron nitride having an average particle diameter within the above specific range, the foaming molding composition of the present disclosure can form a foamed electric wire having a coating material with a smaller average bubble diameter and a larger foaming ratio.

[0109] The average particle size of boron nitride is more preferably 9.0 μm or more, further preferably 10.0 μm or more, still more preferably 10.5 μm or more, particularly preferably 11.0 μm or more, particularly still more preferably 12.0 μm or more, and most preferably 13.0 μm or more.

[0110] In addition, if the average particle size of boron nitride is too large, the average bubble diameter may become large or a large amount of sparks may be generated. The average particle size of boron nitride is preferably 25 μm or less, more preferably 20 μm or less.

[0111] By making the average particle size of boron nitride within the above range, a coating material having fine and uniform bubbles can be formed.

[0112] The average particle size of boron nitride is a value obtained using a laser diffraction / scattering particle size distribution analyzer. In the case of using the wet method, as the medium, it can be appropriately selected, for example, methanol can be used.

[0113] Boron nitride preferably has a particle size distribution represented by (D84 - D16) / D50 of 1.2 or less.

[0114] D84, D50, and D16 represent the particle diameters (μm) at the points where the cumulative curve reaches 84%, 50%, and 16% when the total volume of the boron nitride powder group is set to 100% to obtain the cumulative curve. It should be noted that the cumulative of the particle size distribution is carried out from the small particle size side. The total volume of the above powder group is obtained by preparing a sample in which the boron nitride powder is dispersed in a medium such as methanol and using a laser diffraction / scattering particle size distribution analyzer (for example, Microtrac MT3300 manufactured by Nikkiso Co., Ltd.).

[0115] By making the particle size distribution of boron nitride within the above range, a coating material having fine and uniform bubbles can be formed, and the generation of sparks can be further suppressed.

[0116] The above particle size distribution is more preferably 1.1 or less, further preferably 1.0 or less. The lower limit of the particle size distribution is not particularly limited, and for example, it can be 0.1.

[0117] The cumulative curve of the above particle size distribution (volume particle size distribution) is a cumulative curve obtained using a laser diffraction / scattering particle size distribution analyzer (for example, Microtrac MT3300 manufactured by Nikkiso Co., Ltd.). In the case of using the wet method, as the medium, it can be appropriately selected, for example, methanol can be used.

[0118] Boron nitride is preferably pulverized boron nitride. When boron nitride is pulverized boron nitride, the generation of sparks can be further suppressed.

[0119] The above-mentioned pulverization can be carried out by using methods and conditions that can make the average particle size and particle size distribution of boron nitride within the above ranges. For example, appropriately select the type and conditions of the pulverizer to carry out. As the above-mentioned pulverizer, for example, a jet pulverizer, a hammer mill, a ball mill, a pin-bar pulverizer, etc. can be used.

[0120] The average particle size or particle size distribution of boron nitride can be adjusted to the above ranges by classification.

[0121] In the composition of the present disclosure, although there is no particular limitation, the content of boron nitride is preferably, for example, 0.1% by mass to 10% by mass, more preferably 0.1% by mass to 2.0% by mass, further preferably 0.1% by mass to 1.5% by mass, and still more preferably 0.1% by mass to 1.0% by mass. If the content of boron nitride is too small, it may be difficult to obtain fine bubbles in the coating material of the obtained foamed wire. If the content of boron nitride is too large, the manufacturing cost may increase.

[0122] The foaming composition of the present disclosure may further contain an inorganic salt containing a polyatomic anion within the range that does not impair the effects of the present disclosure.

[0123] As the above-mentioned inorganic salt containing a polyatomic anion, the inorganic salt containing a polyatomic anion disclosed in U.S. Patent No. 4,764,538 can be cited.

[0124] The foaming composition of the present disclosure may further contain sulfonic acid, phosphonic acid or their salts, zeolite, etc. within the range that does not impair the effects of the present disclosure. In addition, organic foaming nucleating agents such as ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), OBSH (4,4'-oxybisbenzenesulfonylhydrazide) can be used in combination.

[0125] In addition to the fluororesin (A) and the compound (B), the foaming composition of the present disclosure may contain conventionally known filler materials within the range that does not impair the effects of the present disclosure.

[0126] As the above-mentioned filler materials, for example, graphite, carbon fiber, coke, silica, zinc oxide, magnesium oxide, magnesium sulfate, tin oxide, antimony oxide, calcium carbonate, magnesium carbonate, magnesium hydroxide, glass, talc, mica, mica, aluminum nitride, calcium phosphate, sericite, diatomaceous earth, silicon nitride, fine silica, fumed silica, alumina, zirconia, quartz powder, kaolin, bentonite, titanium oxide, etc. can be cited. As the shape of the above-mentioned filler materials, there is no particular limitation, and fibrous, needle-like, columnar, whisker-like, plate-like, layered, scaly, hollow spherical, porous, short fiber-like, powdery, granular, bead-like, etc. can be cited. It should be noted that the above-mentioned filler materials are materials different from boron nitride.

[0127] The composition for foam molding of the present disclosure may further contain a thermoplastic resin other than the above fluororesin. Examples of the thermoplastic resin other than the above fluororesin include general-purpose resins such as polyethylene resin, polypropylene resin, vinyl chloride resin, and polystyrene resin; engineering plastics such as nylon, polycarbonate, polyetheretherketone resin, polyphenylene sulfide resin, polyaryl ether ketone (PAEK), polyether ketone ketone (PEKK), polyether ketone (PEK), polyetheretherketone ketone (PEEKK), polyethersulfone (PES), liquid crystal polymer (LCP), polysulfone (PSF), amorphous polyarylate (PAR), polyether nitrile (PEN), thermoplastic polyimide (TPI), polyimide (PI), polyetherimide (PEI), polyamideimide (PAI), etc.

[0128] The composition for foam molding of the present disclosure may further contain other components such as additives. Examples of other components include filler materials such as glass fiber, glass powder, asbestos fiber, cellulose fiber, and carbon fiber, reinforcing agents, stabilizers, lubricants, pigments, flame retardants, and other additives.

[0129] The composition for foam molding of the present disclosure can also be obtained, for example, by a manufacturing method (hereinafter referred to as "the manufacturing method of the composition") including the following mixing step, in which the fluororesin (A), the compound (B), and boron nitride, filler, additive, etc. added as needed are mixed to obtain a mixture.

[0130] As the above mixing method, for example, an existing well-known method or the like can be used, and a mixing method in which the above compound (B) is not easily agglomerated is preferred.

[0131] As the above mixing method, methods such as using a Henschel mixer, a belt mixer, a V-type blender, a ball mill, etc. can also be cited. In addition, for example, a method of mixing by melt-kneading can also be cited.

[0132] The manufacturing method of the composition for foam molding of the present disclosure may include a kneading step of kneading the mixture obtained by the above mixing step. Through the above kneading, pellets can be obtained. The above kneading can be carried out, for example, by using an existing well-known melt-kneading machine such as a single-screw extruder or a twin-screw extruder.

[0133] The manufacturing method of the above composition for foam molding may include a step of fluorinating the fluororesin. As the fluorination treatment, the above method can be used. The fluorination treatment can be carried out, for example, by bringing the pellets obtained by the above kneading into contact with the above fluorine-containing compound.

[0134] The thermoplastic resin other than the fluororesin, boron nitride, the inorganic salt containing a polyatomic anion, the filler, and other additives, which have been described as components that can be contained in the foaming composition of the present disclosure, can be appropriately added in each step of the manufacturing method of the above-mentioned foaming composition according to their properties and the like. In addition, a fluororesin and boron nitride can be further added.

[0135] The foaming composition of the present disclosure can be suitably used as a foaming composition. In addition, the above-mentioned foaming composition can be suitably used as a wire coating composition for forming a coating material for a wire.

[0136] The foaming composition of the present disclosure exhibits good foamability without using a fluorine-based surfactant. As the existing fluorine-based surfactant, a general fluorine-based low-molecular compound. If a large amount of such a fluorine-based low-molecular compound is contained, the resin in the molten state during molding is plasticized, and there is a problem of an increase in sparks. Since the foaming composition of the present disclosure substantially does not contain such a fluorine-based low-molecular compound, the above problem is not generated, and a foam-molded article having an excellent surface state can be obtained.

[0137] The above-mentioned fluorine-based low-molecular compound is not particularly limited, and examples thereof include perfluoroalkyl acids, perfluorosulfonic acids, etc. Specifically, C8F 17 COOH and its salts, C7F 15 COOH and its salts, C6F 13 COOH and its salts, C8F 17 SO3H and its salts, C6F 13 SO3H and its salts, C4F9SO3H and its salts, C8F 17 CH2CH2-SO3H and its salts, C6F 13 CH2CH2-SO3H and its salts, C8F 17 CH2CH2OH, C6F 13 CH2CH2OH, etc. More specifically, {F(CF2)6CH2CH2SO3}2Ba can be cited.

[0138] The content of the above-mentioned fluorine-based low-molecular compound can be analyzed by the following method.

[0139] The pellets of the foaming composition are pulverized by cryogenic pulverization, the produced powder is dispersed in methanol, and ultrasonic waves are applied at 60 °C for 2 hours for extraction. The extract is quantified using a liquid chromatography mass spectrometer (LC-MS / MS), and the obtained value is taken as the content.

[0140] The manufacturing method of the foam-molded article of the present disclosure includes a step of foam-molding the above-mentioned foaming composition.

[0141] As a method for foam-molding the above-described foam-molding composition, there is no particular limitation, and for example, a conventionally well-known method can be used. For example, the following methods can be cited: using a gas in the molten fluororesin (molten resin), introducing the foam-molding composition of the present disclosure into a screw extruder designed for foam operation, and using a continuous gas injection method; etc.

[0142] As the above gas, for example, gases such as chlorodifluoromethane, nitrogen, carbon dioxide, or a mixture of the above gases can be used. They can be introduced as a pressurized gas into the molten resin in the extruder, or gas can be generated by mixing a chemical foaming agent in the molten resin. The above gas is dissolved in the molten resin in the extruder.

[0143] Regarding the gas dissolved in the above molten resin, the gas dissolved in the molten resin escapes from the melt due to the sudden decrease in the pressure of the melt when it is extruded from the extrusion die. The extrudate extruded from the extruder is then cooled and solidified by, for example, introducing it into water or the like.

[0144] The above foam-molded article is obtained by foam-molding the above-described foam-molding composition. Therefore, it has a low dielectric constant, exhibits a stable capacitance and is lightweight, and can obtain a shape with stable dimensions such as wire diameter and thickness as a coating material described later.

[0145] The total volume of the bubbles in the foam-molded article can be appropriately adjusted according to the use, for example, by adjusting the amount of gas inserted into the above extruder, or by selecting the type of gas dissolved.

[0146] The above foam-molded article is obtained in the form of a molded article molded according to the use when extruded from the above extruder. As the above molding method, as long as it is heat-melting molding, there is no particular limitation, and for example, extrusion foam molding, injection foam molding, mold foam molding, etc. can be cited.

[0147] As the shape of the above foam-molded article, there is no particular limitation, and it can be made into various shapes such as a coating material for a foam wire, a fibrous shape such as a wire, a sheet shape, a film shape, a rod shape, a tubular shape, etc. The above foam-molded article can be used, for example, as a lightweight structural material such as an electrical insulating material, a heat insulating material, a sound insulating material, a floating material, or a cushioning material such as a cushion. In addition, the above foam-molded article can be particularly suitably used as a coating material for a foam wire.

[0148] The obtained foam-molded article is preferably a foam-molded article containing a molten solidified body of the foam-molding composition of the present disclosure and bubbles, and the bubbles are uniformly distributed in the molten solidified body. The average bubble diameter of the above bubbles is not limited, and for example, it is preferably 60 μm or less. In addition, the average bubble diameter is preferably 0.1 μm or more.

[0149] The foaming ratio of the above-mentioned foamed molded body is not particularly limited, and is preferably 20% or more. The upper limit of the foaming ratio is not particularly limited, and is, for example, 80%.

[0150] One of the characteristics of the foamed molded body of the present disclosure is that the surface is smoother than that of the conventional foamed molded body containing a fluororesin. Since the surface is smooth, it can be suitably used for a twin cable or the like.

[0151] In the present disclosure, the surface of the foamed molded body can be evaluated by sweeping it with a hand and observing the degree of snagging (protrusion) transmitted to the hand at this time. In addition, as described later, after performing quadratic surface correction for plane shape correction and specifying the range of the wire on the obtained image data and performing correction, the surface roughness of 500×2000 μm is calculated, and thus numerical evaluation is performed. The above surface roughness is preferably less than 10.0 μm, more preferably less than 7.0 μm. Further preferably less than 5.0 μm. The lower limit of the surface roughness can be 0.001 μm or more. The lower limit of the surface roughness can be 0.001 μm or more. In a twin cable or the like, from the aspect of being able to control the surface roughness to a more preferable value, a two-layer structure of foam (inner side) / skin (outer side) is a preferable structure.

[0152] The method for manufacturing a wire of the present disclosure includes a step of coating the above-mentioned foaming molding composition on a core wire to obtain a wire. By using the above-mentioned foaming molding composition, a foamed wire having a coating material with fine and uniform bubbles can be formed. The above step of obtaining a wire is preferably a step of foaming and molding the above-mentioned foaming molding composition.

[0153] The wire obtained by the above-mentioned method for manufacturing a wire is composed of a coating material and a core wire, and the coating material is formed from the above-mentioned foaming molding composition. A wire obtained by coating the above-mentioned foaming molding composition on a core wire is also one of the present disclosures.

[0154] Since the above-mentioned coating material is obtained by coating the above-mentioned foaming molding composition on a core wire, it has fine and uniform bubbles. In addition, it has a low dielectric constant, exhibits a stable capacitance and is lightweight, and a shape with stable dimensions such as wire diameter and thickness can be obtained.

[0155] In addition, the above-mentioned coating material has a smooth surface like the above-mentioned foamed molded body and exhibits the same physical properties.

[0156] In addition to coating the above-mentioned foaming molding composition on a core wire, the above-mentioned wire can be manufactured by the same method as in the past. For example, it can be manufactured by extrusion foaming molding. Preferred extrusion molding conditions can be appropriately selected according to the composition of the composition used and the size of the core wire.

[0157] As a method for coating the above-described foaming composition onto a core wire, for example, the following methods can be cited: using a gas soluble in a molten fluororesin (molten resin), introducing the foaming composition of the present disclosure into a screw extruder designed for foaming operations, and using a continuous gas injection method; etc. As the above gas, the same gas as that used in the method for manufacturing the foamed molded body can be used.

[0158] The obtained coating material is preferably a coating material containing a molten cured body of the foaming composition of the present disclosure and air bubbles, and the air bubbles are uniformly distributed in the molten cured body.

[0159] The average bubble diameter of the above air bubbles is not limited. In the cross-sectional view in the direction perpendicular to the longitudinal direction, for example, it is preferably 200 μm or less, more preferably 100 μm or less, further preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, and especially preferably 20 μm or less. In addition, the average bubble diameter is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more. However, in order to reduce the foaming diameter, a large amount of additives need to be added, and when excessive, sparks are likely to occur. Therefore, the average bubble diameter of the wire for in-vehicle network is preferably 20 to 40 μm, and particularly preferably 25 to 35 μm.

[0160] The structure of such a coating material is obtained by the combination of the fluororesin (A) and the specific compound (B) in the foaming composition of the present disclosure.

[0161] The above average bubble diameter is a value obtained by the following method: obtaining an image of the cross-section of the coating material using a scanning electron microscope (SEM), calculating the diameter of each bubble through image processing, and averaging them.

[0162] The foaming ratio of the above coating material is preferably 20% or more. More preferably 25% or more, further preferably 30% or more. Particularly preferably 40% or more. The upper limit is not particularly limited, for example, it is 90%. The upper limit of the foaming ratio can be 80%, or it can be 60%. In the wire for in-vehicle network, considering breakage during twisting, it is preferably 40% or more and 60% or less.

[0163] The above foaming ratio is a value obtained as ((specific gravity of fluororesin - specific gravity of foamed body) / specific gravity of fluororesin) × 100. The above foaming ratio can be appropriately adjusted according to the use, for example, by adjusting the insertion amount of gas in the above extruder, or by selecting the type of dissolved gas.

[0164] The number of sparks per 3500 m of the above coating material is preferably less than 5. More preferably less than 3, and further preferably 1 or less.

[0165] The above-mentioned number of sparks is the value measured using a Beta LaserMike spark tester HFS1220 at a voltage of 1500V.

[0166] As the material of the core wire, metal conductor materials such as copper and aluminum, carbon, etc. can be used. In addition, it can be a single material, or the surface can be coated with silver or tin, etc.

[0167] The diameter of the core wire is preferably 0.02 mm to 3 mm. The diameter of the core wire is more preferably 0.04 mm or more, further preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. The diameter of the core wire is more preferably 2 mm or less. In addition, the above-mentioned core wire can be a single wire or a stranded wire formed by twisting multiple core wires.

[0168] The shape of the core wire is not particularly limited, and examples include a flat shape, a flat wire, etc.

[0169] For the above-mentioned wire, the thickness of the above-mentioned coating material is preferably 0.01 mm to 3.0 mm. The thickness of the coating material is also preferably 2.0 mm or less.

[0170] As specific examples of the core wire, for example, AWG (American Wire Gauge)-46 (solid copper wire with a diameter of 40 microns), AWG-42 (solid copper wire with a diameter of 64 microns), AWG-36 (a wire formed by stranding 7 solid copper wires with a diameter of 127 microns and 7 copper wires with a diameter of 51 microns, with a total size of a wire with a diameter of 153 microns), AWG-30 (a wire formed by stranding 7 solid copper wires with a diameter of 254 microns and 7 copper wires with a diameter of 102 microns, with a total size of a wire with a diameter of 306 microns), AWG-27 (solid copper wire with a diameter of 361 microns), AWG-26 (solid copper wire with a diameter of 404 microns), AWG-24 (solid copper wire with a diameter of 510 microns), AWG-22 (solid copper wire with a diameter of 635 microns), etc. can be used.

[0171] The above-mentioned foamed wire is composed of a core wire and a covering material covering the core wire. The above-mentioned foamed wire can be suitably used as cables for connecting a computer and its peripheral devices, cables for high-speed communication and high-capacity images or sounds, cables for connecting servers in a data center, such as LAN cables, USB cables, Lightning cables, Thunderbolt cables, CATV cables, HDMI (registered trademark) cables, QSFP cables, aerospace wires, underground power transmission cables, submarine power cables, high-voltage cables, superconducting cables, packaging wires, automotive wires, wire harnesses and electrical equipment, robot and FA wires, OA equipment wires, information equipment wires (optical fiber cables, audio cables, etc.), internal wiring for communication base stations, large-current internal wiring (inverters, power conditioners, battery systems, etc.), internal wiring for electronic equipment, internal wiring for small electronic devices and mobile devices, wiring for movable parts, internal wiring for electrical equipment, internal wiring for measuring equipment, power cables (for construction, wind / solar power generation, etc.), control and measurement wiring cables, motor cables, etc.

[0172] The above-mentioned wire can have a two-layer structure (skin-foam) in which a non-foamed layer is inserted between the core wire and the covering material, a two-layer structure (foam-skin) in which a non-foamed layer is covered on the outer layer, or a three-layer structure (skin-foam-skin) in which a non-foamed layer is further covered on the outer layer of the skin-foam. In order to reduce the surface roughness, a foam-skin or skin-foam-skin structure is preferred. Since the equipment can be simplified, a foam skin is preferred. The total thickness of the skin layer is preferably 200 μm or less, more preferably 100 μm or less, particularly preferably 70 μm or less, and most preferably 40 μm or less. In addition, it is preferably 1 μm or more.

[0173] The non-foamed layer of the above-mentioned wire is not particularly limited and can be a resin layer composed of a TFE / HFP copolymer, a TFE / PAVE copolymer, a TFE / ethylene copolymer, a vinylidene fluoride-based polymer, a polyolefin resin such as polyethylene [PE], a resin such as polyvinyl chloride [PVC], etc.

[0174] The foaming composition for the present disclosure substantially does not contain fluorine-based low-molecular compounds. Therefore, the above-mentioned foamed molded body and wire also substantially do not contain fluorine-based low-molecular compounds.

[0175] The content of the fluorine-based low-molecular compounds in the above-mentioned foamed molded body and wire can also be analyzed in the same manner as in the case of the above-mentioned foaming composition.

[0176] The present disclosure also relates to the foamed wires listed below.

[0177] (1) A foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that, when observed in a cross-section parallel to the length direction, the average aspect ratio of the bubbles is 1.9 or less.

[0178] (2) A foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that, when observed in a cross-section parallel to the length direction, the proportion of bubbles having an aspect ratio of 3 or more is 13% or less relative to the total amount of bubbles measured in the cross-section parallel to the length direction.

[0179] (3) A foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that, when observed in a cross-section parallel to the length direction, the standard deviation of the aspect ratio of the bubbles is 1.3 or less.

[0180] (4) A foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that the foaming ratio is 20% or more and the surface roughness is less than 5.0 μm.

[0181] (5) A foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that, when observed in a cross-section perpendicular to the length direction, the average bubble diameter of the bubbles is 20 μm to 40 μm.

[0182] (6) A foamed wire for an in-vehicle network cable having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, wherein the fluororesin layer or the fluororesin composition layer has bubbles, and the foamed wire is characterized in that the structure of the wire is a foam (inner) / skin (outer) structure.

[0183] The bubbles contained in the fluororesin layer or the fluororesin composition layer satisfy these physical properties, indicating that they have fine and uniform bubbles, and it can be said that they have a low dielectric constant and exhibit a stable capacitance.

[0184] These fluororesin layers and fluororesin composition layers can be formed, for example, from the foaming composition disclosed in the present application.

[0185] The average aspect ratio of the above-mentioned bubbles is 1.9 or less. The above average aspect ratio can be measured as follows: An image of a cross-section parallel to the length direction of the coating material is obtained using a scanning electron microscope (SEM), and the ratio of the major axis to the minor axis (major axis / minor axis) is calculated from the major axis and minor axis of each bubble obtained through image processing, and the aspect ratio thus obtained is averaged, thereby enabling measurement. The average aspect ratio is preferably 1.8 or less, more preferably 1.6 or less. Additionally, it is preferably 1.0 or more.

[0186] The proportion of bubbles with an aspect ratio of 3 or more among the total number of bubbles measured in the observation of a cross-section parallel to the length direction is 13% or less. The above proportion is calculated as follows: An image of a cross-section parallel to the length direction of the coating material is obtained using a scanning electron microscope (SEM), and the ratio of the major axis to the minor axis (major axis / minor axis) is calculated from the major axis and minor axis of each bubble obtained through image processing, and the proportion of bubbles with an aspect ratio of 3 or more thus obtained is calculated.

[0187] The proportion of bubbles with an aspect ratio of 3 or more is preferably 6% or less, more preferably 3% or less. Additionally, it is preferably 0.01% or more.

[0188] The standard deviation of the aspect ratio of the above-mentioned bubbles is 1.3 or less. The above standard deviation is calculated as follows: An image of a cross-section parallel to the length direction of the coating material is obtained using a scanning electron microscope (SEM), and the ratio of the major axis to the minor axis (major axis / minor axis) is calculated from the major axis and minor axis of each bubble obtained through image processing, and the standard deviation of the aspect ratio thus obtained is calculated. The standard deviation of the aspect ratio is preferably 1.1 or less, more preferably 0.8 or less, and further preferably 0.6 or less. Additionally, it is preferably 0.01 or more.

[0189] The above foaming ratio is preferably 20% or more. The above foaming ratio is a value obtained by calculating ((specific gravity of fluororesin - specific gravity of fluororesin layer or fluororesin composition layer) / specific gravity of fluororesin) × 100.

[0190] The above foaming ratio is more preferably 25% or more, even more preferably 30% or more. Further preferably, it is 40% or more.

[0191] The above surface roughness is less than 5.0 μm. The above surface roughness is a value calculated as follows: The surface of the wire is measured using a Keyence laser microscope, and after specifying the range of the wire in the obtained image data and performing correction by quadratic surface correction for surface shape correction, the surface roughness of 500 × 200 μm is calculated.

[0192] The above surface roughness is most preferably 3.0 μm or less.

[0193] In the observation of a cross-section perpendicular to the length direction, the average bubble diameter of the above-mentioned bubbles is 20 to 40 μm, preferably 25 to 35 μm. The above-mentioned average bubble diameter is a value obtained as follows: An image of the cross-section of the coating material is obtained using a scanning electron microscope (SEM), and the diameter of each bubble is calculated by image processing and averaged.

[0194] In the observation of a cross-section perpendicular to the length direction, the average bubble diameter of the bubbles in the above-mentioned foamed wire is preferably 50 μm or less. The above-mentioned average bubble diameter is more preferably 40 μm or less, and further preferably 35 μm or less. In addition, it is preferably 0.1 μm or more, more preferably 20 μm or more, and further preferably 25 μm or more.

[0195] Furthermore, the bubbles with an average bubble diameter of 50 μm or less are preferably 90% or more, and further preferably 95% or more.

[0196] The maximum bubble diameter is preferably 150 μm or less, and more preferably 100 μm or less.

[0197] In addition, the number of bubbles present in the cross-section is preferably 1500 bubbles / mm 2 per unit area or less, more preferably 1000 bubbles / mm 2 per unit area or less, and further preferably 800 bubbles / mm 2 per unit area or less.

[0198] In the above-mentioned foamed wire, the coating thickness of the fluororesin layer or the fluororesin composition layer is preferably 0.4 mm or less, more preferably 0.3 mm or less, and further preferably 0.25 mm or less. The above-mentioned coating thickness is a value obtained as (wire coating outer diameter - core wire diameter) / 2.

[0199] In the above-mentioned foamed wire, the core wire diameter is preferably 0.5 mm or less, more preferably 0.4 mm or less, and still more preferably 0.3 mm or less.

[0200] There is no particular limitation on the manufacturing method of the above-mentioned foamed wire, and it is preferably manufactured by a manufacturing method of a foamed wire using the above-mentioned foaming composition of the present disclosure. That is, if the foaming composition of the present disclosure is used, a foamed wire having the above-mentioned properties can be obtained, and various excellent properties can be obtained therefrom.

[0201] The manufacturing method of the above-mentioned foamed wire of the present disclosure can be carried out through the above-mentioned process.

[0202] The foaming composition of the present disclosure is used for coating an electric wire for an in-vehicle network cable.

[0203] The electric wire for an in-vehicle network cable can be applied to vehicles from large commercial vehicles to private cars.

[0204] Preferably, the in-vehicle network cable of the present disclosure includes a twisted pair cable, the twisted pair cable includes a pair of wires twisted together, and at least one of the pair of wires is the foamed wire for the in-vehicle network cable of the present disclosure. In addition, from the viewpoint of maintaining electrical properties, it is preferable that the twist of the wires after twisting has little breakage, and the deformation rate is preferably 20% or less.

[0205] The in-vehicle network cable of the present disclosure includes the foamed wire for the in-vehicle network cable of the present disclosure described above. The present disclosure also provides the use of the in-vehicle network cable in an in-vehicle network.

[0206] Examples of the in-vehicle network cable of the present disclosure include coaxial cables, twisted pair cables, twin parallel cables (two parallel wires), quad parallel cables, octa parallel cables, etc.

[0207] As the above coaxial cable, for example, a cable can be cited in which an outer conductor layer (such as a metal mesh, etc.) made of metal is formed around the foamed wire for the in-vehicle network cable of the present disclosure, and a resin layer (sheath layer) is formed around the outer conductor layer. The above resin layer (sheath layer) is not particularly limited, and may be a layer made of a fluorine-containing copolymer having a TFE unit such as a TFE / HFP copolymer, a TFE / PAVE copolymer, polyvinyl chloride [PVC], polyethylene, or the like. The above outer conductor layer and resin layer (sheath layer) can be coated by a conventionally known method.

[0208] The in-vehicle network cable of the present disclosure preferably includes a twisted pair cable having a pair of wires twisted together, and at least one of the pair of wires is the foamed wire for the in-vehicle network cable of the present disclosure described above. By using a twisted pair cable, it is not easily affected by noise, and it is particularly suitable as an in-vehicle network cable that is likely to generate a large amount of noise.

[0209] The in-vehicle network cable of the present disclosure may include one pair of twisted pair cables, or may include two or more pairs of twisted pair cables. The number of twisted pair cables is preferably 1 to 4, more preferably 1 or 2, and further preferably 1.

[0210] The in-vehicle network cable of the present disclosure preferably includes a sleeve surrounding the periphery of the above twisted pair cable. Examples of the material of the above sleeve include fluorine-containing copolymers having a TFE unit such as TFE / HFP copolymers, TFE / PAVE copolymers, polyvinyl chloride [PVC], polyethylene, etc., but are not limited thereto. The thickness of the above sleeve is not particularly limited and can be appropriately set according to the purpose.

[0211] In the in-vehicle network cable of the present disclosure, an outer conductor layer made of metal (such as a metal mesh, aluminum foil, etc.) can be provided around the above-mentioned twisted pair cable. The above-mentioned outer conductor layer functions as a shield to further improve stability. However, from the aspects of light weight and bendability, no shielding is preferred.

[0212] The in-vehicle network cable of the present disclosure is preferably an in-vehicle Ethernet cable. Specifically, it is more preferably a network cable of 100BASE-T1 or 1000BASE-T1.

[0213] The present disclosure also provides an in-vehicle network system including an in-vehicle computer and the in-vehicle network cable of the present disclosure connected to the in-vehicle computer.

[0214] The in-vehicle network system of the present disclosure only needs to include at least one in-vehicle computer, and may also include two or more in-vehicle computers. The above-mentioned in-vehicle computer can be directly connected or indirectly connected to the in-vehicle network cable of the present disclosure. For example, the in-vehicle network cable of the present disclosure and the above-mentioned in-vehicle computer can be connected through a hub, a router, etc.

[0215] The above-mentioned in-vehicle computer is not limited as long as it is a computer mounted on a vehicle. For example, an in-vehicle electronic control unit (in-vehicle ECU), an in-vehicle telematics control unit (in-vehicle TCU), etc. can be cited.

[0216] The in-vehicle network system of the present disclosure may include a first in-vehicle computer, a second in-vehicle computer, and the in-vehicle network cable of the present disclosure connecting the first in-vehicle computer and the second in-vehicle computer.

[0217] Examples

[0218] Hereinafter, the present disclosure will be specifically described based on examples. In the following examples, unless otherwise specified, "parts" and "%" respectively represent "parts by mass" and "% by mass".

[0219] Production of Pellet A in Production Example 1

[0220] Pellet A was obtained by the same method as described in Example 1 of Japanese Patent Application Laid-Open No. 2017-128119. The composition of the obtained pellet is a TFE / HFP / PPVE copolymer, TFE / HFP / PPVE = 87.8 / 11.2 / 1.0 (mass ratio), melting point: 255 °C, melt flow rate (MFR): 37 g / 10 minutes, and the total number of unstable end groups and -CF2H end groups per 1 × 10 6 carbon atoms is 0.

[0221] Production of Pellet B in Production Example 3

[0222] The pellets obtained by the same method as described in Synthesis Example 1 of WO2005-052015 were fluorinated to obtain Pellet B. The composition of the obtained pellets was a TFE / PPVE copolymer, TFE / PPVE = 94.9 / 5.1 (mass ratio), melting point: 255 °C, melt flow rate (MFR): 63 g / 10 min, and the total number of unstable end groups and -CF2H end groups was 0 per 1 × 10 6 carbon atoms.

[0223] Examples 1 to 5 and Comparative Examples 1 to 3

[0224] An additive was added to the above-obtained pellets, and a foamed wire was formed from a foaming composition adjusted to a specified addition amount by melt-kneading using an extruder set at the extrusion temperature shown in Table 1. A 22 AWG copper wire (OD: 0.64 mm) was used as the core wire, and the extrusion temperature, nitrogen introduction flow rate (pressure), extrusion speed, and draw speed were adjusted so that the outer diameter after coating was 1.4 mm, the wall thickness was 0.38 mm, the skin was 25 μm, and the capacitance was 40 pF / ft (corresponding to a foaming ratio of 48%). The wire extrusion conditions are shown in Table 2.

[0225] This was continuously carried out for 1 hour, and spark out was observed for 3500 m with stable molding. Furthermore, for the obtained foamed wire, the foaming ratio, average aspect ratio, average cell diameter, and surface roughness were measured by the following methods. In addition, the breakage of the wire during doubling was evaluated.

[0226] Each property of the obtained wire was evaluated, and the results are shown in Tables 3 and 4.

[0227] [Table 1]

[0228]

[0229] [Table 2]

[0230]

[0231] It should be noted that the additives in Tables 3 and 4 are as follows.

[0232] NA11 (crystallization nucleating agent ADKSTAB NA-11 manufactured by ADEKA Corporation): sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate

[0233] C4SBa salt: (C4F9SO3)2Ba

[0234] GEL ALL MD (manufactured by Shin Nippon Rika Co., Ltd.): bis(4-methylbenzylidene) sorbitol

[0235] Regarding the various characteristics in this specification, the following methods are used for measurement.

[0236] (Measurement of the number of unstable end groups)

[0237] The pellets are rolled using a hydraulic press to produce a film with a thickness of about 0.3 mm, and this film is analyzed using an FT-IR Spectrometer 1760X (manufactured by Perkin-Elmer).

[0238] The differential spectrum with a standard sample (a sample that has been fully fluorinated until no substantial difference is found in the spectrum) is obtained, the absorbance of each peak is read, and the number of unstable end groups per 1×10 6 carbon atoms is calculated according to the following formula.

[0239] The number of unstable end groups per 1×10 6 carbon atoms = (I×K) / t

[0240] (I: absorbance, K: correction coefficient, t: film thickness (unit: mm))

[0241] The correction coefficient (K) for each unstable end group is as described below.

[0242] -COF (1884 cm -1 ) ··· 405

[0243] -COOH (1813 cm -1 , 1775 cm -1 ) ··· 455

[0244] -COOCH3 (1795 cm -1 ) ··· 355

[0245] -CONH2 (3438 cm -1 ) ··· 480

[0246] -CH2OH (3648 cm -1 ) ··· 2325

[0247] (Measurement of the number of -CF2H end groups)

[0248] Using a nuclear magnetic resonance apparatus AC300 (manufactured by Bruker-Biospin), the measurement temperature is set to (the melting point of the fluororesin + 20) °C and the 19 F-NMR measurement is performed, and it is obtained from the integral value of the peak due to the presence of the -CF2H group and the integral values of other peaks.

[0249] (Melting point)

[0250] Regarding the melting point of the fluororesin, the temperature corresponding to the peak measured at a heating rate of 10 °C / minute using RDC220 (manufactured by SEIKO Instruments Inc.) is defined as the melting point.

[0251] (MFR)

[0252] Regarding the MFR of the fluororesin, the value measured at 372 °C under a load of 5 kg using a die with a diameter of 2.1 mm and a length of 8 mm with a KAYENESS melt flow index measuring instrument 4000 series (manufactured by Yasuda Seiki Co., Ltd.) in accordance with ASTM D-1238.

[0253] (Outer diameter)

[0254] The outer diameter of the wire is measured using LASER MICRO DIAMETER LDM-303H-XY (manufactured by Takikawa Engineering Co., Ltd.).

[0255] (Capacitance)

[0256] The capacitance is measured using CAPAC300 19C (manufactured by Zumbach).

[0257] (Number of sparks)

[0258] Using a Beta LaserMike spark tester HFS1220, the number of sparks per 3500 m is measured at a voltage of 1500 V.

[0259] (Foaming ratio)

[0260] It is calculated as ((specific gravity of fluororesin - specific gravity of foam) / specific gravity of fluororesin) × 100.

[0261] (Average bubble diameter)

[0262] An SEM image of the wire cross-section perpendicular to the length direction is taken, and the diameter of each bubble is calculated through image processing and averaged to obtain the average bubble diameter.

[0263] (Surface roughness)

[0264] The surface of the wire is measured using a Keyence laser microscope. After specifying the wire range and performing correction on the obtained image data through quadratic surface correction for surface shape correction, the surface roughness of 500 × 2000 μm is calculated.

[0265] (Average aspect ratio of bubbles)

[0266] An image of a cross-section parallel to the longitudinal direction of the coating material is obtained using a scanning electron microscope (SEM), and the ratio of the major axis to the minor axis (major axis / minor axis) is calculated from the major axis and minor axis of each bubble obtained by image processing, and the aspect ratio thus obtained is averaged to perform the measurement.

[0267] (Breakage of the wire during doubling)

[0268] Two wires are twisted using a wire twisting machine under the following twisting conditions. The ratio of the deformation with respect to the initial wire diameter is defined as the deformation rate, and a case where the deformation rate is 20% or less is regarded as no breakage.

[0269] Linear velocity: 19 m / minute

[0270] Twisting: 3,000 twists / minute

[0271] Twisting length: 8.5 mm

[0272] Deformation rate: (Deformation of wire diameter / Initial wire diameter) × 100 (%)

[0273] [Table 3]

[0274]

[0275] [Table 4]

[0276] The foamed wire obtained in the examples did not exhibit breakage during doubling and is particularly suitable for use as a wire for in-vehicle network cables.

[0277] Industrial Applicability

[0278] The composition for foam molding of the present disclosure is particularly suitable as a material for forming a coating material of a foamed wire.

Claims

1. A composition for foam molding, characterized in that, It contains a fluororesin (A) and a compound (B) with a thermal decomposition temperature of 300 °C or higher and a solubility parameter SP value of 8 to 15, and is used for coating an electric wire for an in-vehicle network cable.

2. The composition for foam molding according to claim 1, wherein Compound (B) is a compound containing at least one partial structure selected from the group consisting of an aromatic ring, a phosphate group, and an amide group.

3. The composition for foam molding according to claim 2, wherein Compound (B) is a compound containing one or more C6-14 aromatic rings or a salt thereof.

4. The composition for foam molding according to claim 2, wherein Compound (B) is at least one compound selected from the group consisting of a phosphate ester and its salt, a phosphate ester complex compound, and a compound having two or more amide groups.

5. The composition for foam molding according to claim 3 or 4, wherein, The salt of compound (B) is an alkali metal or an alkaline earth metal.

6. The composition for foam molding according to any one of claims 2 to 5, wherein, Compound (B) is at least one of the compounds represented by the following formulas (1), (2), (3), and (4). [Chemical formula 1] [Chemical formula 2] [Chemical formula 3] [Chemical formula 4] wherein, R1, R2, R3, R4, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34 , R 41 , R 42 represent a hydrogen atom, an alkyl or cycloalkyl group having 1 to 8 carbon atoms, or an aryl, alkylaryl or aralkyl group having 6 to 12 carbon atoms, Ar 41 represents an aryl group, R5 and R6 represent a hydrogen atom or a methyl group, n represents an integer of 1 or 2, m represents an integer of 0 to 2, and X represents a metal having a valence of m + n.

7. The composition for foam molding according to claim 6, wherein R1, R2, R in Formula (1), Formula (2), and Formula (3) 21 , R 22 , R 31 and R 33 are alkyl groups having 1 to 8 carbon atoms.

8. The composition for foam molding according to claim 6, wherein, In formulas (1), (2), and (3), X is at least one of sodium, potassium, rubidium, calcium, and barium.

9. The composition for foam molding according to claim 6, wherein, Compound (B) is an aromatic cyclic phosphate salt represented by the above formula (1).

10. The composition for foam molding according to claim 9, wherein, Compound (B) is sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.

11. The foaming composition according to any one of claims 1 to 10, wherein Fluororesin (A) is a fluororesin capable of melt processing.

12. The composition for foam molding according to any one of claims 1 to 11, wherein, Fluororesin (A) is at least one selected from the group consisting of a tetrafluoroethylene / hexafluoropropylene copolymer, a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, and a tetrafluoroethylene / ethylene copolymer.

13. The composition for foam molding according to any one of claims 1 to 12, wherein, Fluororesin (A) is a fluororesin treated by fluorination.

14. The composition for foam molding according to any one of claims 1 to 13, wherein, Substantially does not contain fluorine-based low molecular weight compounds.

15. A foamed molded body, characterized in that, Obtained from the foaming composition according to any one of claims 1 to 14.

16. The foamed molded body according to claim 15, wherein, Substantially does not contain fluorine-based low molecular weight compounds.

17. A foamed wire for an in-vehicle network cable, characterized in that, It has a core wire and a coating material obtained from the foaming composition according to any one of claims 1 to 14, which coats the core wire.

18. The foamed electric wire for in-vehicle network cable according to claim 17, wherein, Substantially does not contain fluorine-based low molecular weight compounds.

19. A foamed electric wire for an in-vehicle network cable, the foamed electric wire having a core wire and a fluororesin layer or a fluororesin composition layer coated on the core wire, the fluororesin layer or the fluororesin composition layer having bubbles, characterized in that In a cross-sectional view perpendicular to the length direction, the average bubble diameter of the bubbles is 20 μm to 40 μm.

20. A foamed electric wire for an in-vehicle network cable, the foamed electric wire having a core wire and a fluororesin layer or a fluororesin composition layer coated on the core wire, the fluororesin layer or the fluororesin composition layer having bubbles, characterized in that In a cross-sectional view parallel to the length direction, the average aspect ratio of the bubbles is 1.9 or less.

21. A foamed electric wire for an in-vehicle network cable, the foamed electric wire having a core wire and a fluororesin layer or a fluororesin composition layer coated on the core wire, the fluororesin layer or the fluororesin composition layer having bubbles, characterized in that In a cross-sectional view parallel to the length direction, the proportion of bubbles with an aspect ratio of 3 or more relative to the total amount of bubbles measured in the cross-sectional view parallel to the length direction is 13% or less.

22. A foamed wire for an in-vehicle network cable, the foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, the fluororesin layer or the fluororesin composition layer having air bubbles, characterized in that in a cross-sectional view parallel to the longitudinal direction, the standard deviation of the aspect ratio of the air bubbles is 1.3 or less.

23. A foamed wire for an in-vehicle network cable, the foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, the fluororesin layer or the fluororesin composition layer having air bubbles, characterized in that the foaming ratio is 20% or more and the surface roughness is less than 5.0 μm.

24. A foamed wire for an in-vehicle network cable, the foamed wire having a core wire and a fluororesin layer or a fluororesin composition layer covering the core wire, the fluororesin layer or the fluororesin composition layer having air bubbles, characterized in that the structure of the wire is a foam as the inner side / an epidermis as the outer side structure.

25. A method for manufacturing a foamed molded body, characterized in that, It includes a step of foaming the foaming composition according to any one of claims 1 to 14.

26. A manufacturing method of an electric wire, characterized in that, It includes a step of covering the core wire with the foaming composition according to any one of claims 1 to 14 to obtain a wire.

27. A vehicle-mounted network cable, characterized in that, It contains the foamed wire for an in-vehicle network cable according to any one of claims 17 to 24.

28. The in-vehicle network cable according to claim 27, comprising: a twisted pair cable having a pair of wires twisted together; at least one of the pair of wires being the foamed wire for an in-vehicle network cable according to any one of claims 17 to 24.

29. The in-vehicle network cable according to claim 28, wherein, In the twisted pair cable, the deformation rate after twisting of the foamed wire is 20% or less.

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