Resin composition for foam molding, foam molded body, method for producing foam molded body, foam electrical wire, and method for producing foam electrical wire

Abstract

The purpose of the present disclosure is to provide a resin composition for foam molding, a foam molded body, a method for producing a foam molded body, a foam electrical wire, and a method for producing a foam electrical wire wire, the resin composition being capable of sufficiently miniaturizing bubbles and having a good appearance. The present disclosure is a resin composition for foam molding containing a fluororesin (A) and a tetrapyrrole-based cyclic compound (B).

Description

Resin composition for foam molding, foam molded product, method for manufacturing foam molded product, foam electric wire, and method for manufacturing foam electric wire

[0001] The present disclosure relates to a resin composition for foam molding, a foam molded article, a method for producing a foam molded article, a foam electric wire, and a method for producing a foam electric wire.

[0002] Fluorine resins are widely used in a variety of applications due to their excellent heat resistance and chemical resistance.

[0003] Foam molding is a well-known method for reducing the weight and improving the electrical properties of fluororesins. In foam molding, fine bubbles can be formed by adding a substance that acts as a nucleating agent for foam formation.

[0004] Since fluororesins have a high molding temperature, the foaming nucleating agents that can be used are limited, and boron nitride is generally used (see, for example, Patent Documents 1 to 3).

[0005] Japanese Patent Laid-Open No. 10-045931 Japanese Patent Laid-Open No. 2022-028640 Japanese Patent Laid-Open No. 2005-206745

[0006] However, with boron nitride, there is room for improvement in that the bubbles cannot be made sufficiently fine.

[0007] Furthermore, Patent Document 1 discloses a method of miniaturizing bubbles by blending a salt such as perfluoroalkylsulfonic acid together with boron nitride. However, when a fluorosurfactant such as perfluoroalkylsulfonic acid is blended, the molten resin is plasticized during molding, which can cause sparks and impair the appearance, leaving room for improvement.

[0008] An object of the present disclosure is to provide a foam molding resin composition that can sufficiently reduce the size of bubbles and has a good appearance, a foam molded product, a method for producing a foam molded product, a foam electric wire, and a method for producing a foam electric wire.

[0009] The present disclosure (1) is a resin composition for foam molding containing a fluororesin (A) and a tetrapyrrole-based cyclic compound (B).

[0010] The present disclosure (2) is the resin composition for foam molding according to the present disclosure (1), wherein the fluororesin (A) is a melt-moldable fluororesin.

[0011] The present disclosure (3) relates to the resin composition for foam molding according to the present disclosure (1) or (2), wherein the fluororesin (A) is at least one selected from the group consisting of a tetrafluoroethylene / hexafluoropropylene copolymer and a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer.

[0012] The present disclosure (4) is the resin composition for foam molding according to any one of the present disclosures (1) to (3), wherein the fluororesin (A) is a tetrafluoroethylene / hexafluoropropylene copolymer.

[0013] The present disclosure (5) is the resin composition for foam molding according to any one of the present disclosures (1) to (4), wherein the fluororesin (A) has been fluorinated.

[0014] The present disclosure (6) is the resin composition for foam molding according to any one of the present disclosures (1) to (5), wherein the content of the fluororesin (A) is 80 to 99.99 mass%.

[0015] The present disclosure (7) is the resin composition for foam molding according to any one of the present disclosures (1) to (6), in which the content of the fluororesin (A) is 97% by mass or more and less than 99.85% by mass.

[0016] The present disclosure (8) is the resin composition for foam molding according to any one of the present disclosures (1) to (7), which is substantially free of a fluorine-based low-molecular-weight compound.

[0017] The present disclosure (9) is the resin composition for foam molding according to any one of the present disclosures (1) to (8), wherein the tetrapyrrole cyclic compound (B) has a phthalocyanine skeleton.

[0018] The present disclosure (10) is the resin composition for foam molding according to any one of the present disclosures (1) to (9), wherein the tetrapyrrole cyclic compound (B) is a metal phthalocyanine.

[0019] The present disclosure (11) is the resin composition for foam molding according to any one of the present disclosures (1) to (10), wherein the tetrapyrrole cyclic compound (B) is copper phthalocyanine.

[0020] The present disclosure (12) is the resin composition for foam molding according to any one of the present disclosures (1) to (11), wherein the content of the tetrapyrrole cyclic compound (B) is 0.1 to 20 parts by mass per 100 parts by mass of the fluororesin (A).

[0021] The present disclosure (13) is the resin composition for foam molding according to any one of the present disclosures (1) to (12), wherein the content of the tetrapyrrole cyclic compound (B) is 0.5 to 2.0 parts by mass per 100 parts by mass of the fluororesin (A).

[0022] The present disclosure (14) is a foam-molded article formed using the foam-molding resin composition according to any one of the present disclosures (1) to (13).

[0023] The present disclosure (15) is a method for producing a foam-molded article, comprising a step of foam-molding the resin composition for foam molding according to any one of the present disclosures (1) to (13).

[0024] The present disclosure (16) is a foamed electric wire having a conductor and a foamed insulation layer formed on the conductor using the resin composition for foam molding according to any one of the present disclosures (1) to (13).

[0025] The present disclosure (17) is a method for producing a foamed electric wire, comprising a step of forming a foamed insulating layer on a conductor using the resin composition for foam molding according to any one of the present disclosures (1) to (13).

[0026] According to the present disclosure, it is possible to provide a foam molding resin composition, a foam molded product, a method for producing a foam molded product, a foam electric wire, and a method for producing a foam electric wire, which are capable of sufficiently miniaturizing bubbles and have a good appearance.

[0027] The present disclosure will be specifically described below.

[0028] The resin composition for foam molding of the present disclosure contains a fluororesin (A) and a tetrapyrrole-based cyclic compound (B).

[0029] In the resin composition for foam molding of the present disclosure, the tetrapyrrole cyclic compound (B) functions as a foam nucleating agent, allowing for the formation of finer bubbles than when boron nitride is used. This enables application to applications requiring thin molded articles, such as thin electric wires. Furthermore, compared to when a fluorosurfactant is used, spark generation can be suppressed, reducing appearance defects. This allows for long-term molding, such as electric wire molding. Furthermore, not only is spark generation suppressed, but the surface roughness is also reduced, resulting in improved electrical properties.

[0030] Fluorine resin (A) can be any resin containing fluorine, but preferably be melt-moldable fluororesin.As melt-moldable fluororesin, for example, tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) (PAVE) copolymer [PFA], TFE / ethylene copolymer [ETFE], chlorotrifluoroethylene (CTFE) / ethylene copolymer [ECTFE], polyvinylidene fluoride [PVdF], polychlorotrifluoroethylene [PCTFE], TFE / vinylidene fluoride (VdF) copolymer [VT], polyvinyl fluoride [PVF], TFE / VdF / CTFE copolymer [VTC], TFE / ethylene / HFP copolymer, TFE / HFP / VdF copolymer etc. can be used alone or in combination.

[0031] Examples of the PAVE include perfluoro(methyl vinyl ether) [PMVE], perfluoro(ethyl vinyl ether) [PEVE], and perfluoro(propyl vinyl ether) [PPVE]. Of these, PPVE is preferred. These may be used alone or in combination of two or more.

[0032] The fluororesin (A) may have polymerization units based on other monomers in an amount that does not impair the essential properties of each fluororesin. The other monomers can be appropriately selected from, for example, TFE, HFP, ethylene, propylene, perfluoro(alkyl vinyl ether), perfluoroalkylethylene, hydrofluoroolefin, fluoroalkylethylene, perfluoro(alkyl allyl ether), etc. One or more of these can be used. The perfluoroalkyl group constituting the other monomer preferably has 1 to 10 carbon atoms.

[0033] The other monomer may be a monomer having a polar group. Examples of the monomer having a polar group include non-fluorine-containing monomers having a hydroxyl group, such as hydroxyalkyl vinyl ethers, such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; non-fluorine-containing monomers having a carboxyl group, such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, fumaric acid, crotonic acid, maleic acid, citraconic acid, undecylenic acid, and acetylenedicarboxylic acid; itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2, Examples thereof include fluorine-containing monomers having an acid anhydride residue such as 3-dicarboxylic acid anhydride (hereinafter also referred to as "NAH"), succinic anhydride, fumaric anhydride, maleic anhydride, etc.; fluorine-containing monomers having a sulfo group such as vinyl sulfonic acid; fluorine-containing monomers having an epoxy group (glycidyl group) such as glycidyl vinyl ether, glycidyl allyl ether, etc.; fluorine-containing monomers having an amino group such as aminoalkyl vinyl ether, aminoalkyl allyl ether, etc.; fluorine-containing monomers having an amide group such as (meth)acrylamide, methylolacrylamide, etc.; and fluorine-containing monomers having a nitrile group such as acrylonitrile, methacrylonitrile, etc.

[0034] The fluororesin (A) is preferably at least one selected from the group consisting of a TFE / HFP copolymer and a TFE / PAVE copolymer, more preferably a TFE / HFP copolymer, because of its excellent heat resistance. Also, a perfluororesin is preferred because of its superior electrical properties.

[0035] The TFE / HFP copolymer preferably has a TFE / HFP mass ratio of 80 to 97 / 3 to 20, more preferably 84 to 92 / 8 to 16. The TFE / HFP copolymer may be a binary copolymer of TFE and HFP, or may be a ternary copolymer (e.g., a TFE / HFP / PAVE copolymer) composed of a comonomer copolymerizable with TFE and HFP. The TFE / HFP copolymer is also preferably a TFE / HFP / PAVE copolymer containing polymerized units based on PAVE. The TFE / HFP / PAVE copolymer preferably has a TFE / HFP / PAVE mass ratio of 70 to 97 / 3 to 20 / 0.1 to 10, more preferably 81 to 92 / 5 to 16 / 0.3 to 5.

[0036] The TFE / PAVE copolymer preferably has a mass ratio of TFE / PAVE of 90-99 / 1-10, more preferably 92-97 / 3-8.

[0037] The TFE / ethylene copolymer preferably has a TFE / ethylene molar ratio of 20 to 80 / 20 to 80, more preferably 40 to 65 / 35 to 60. The TFE / ethylene copolymer may also contain other monomer components. That is, the TFE / ethylene copolymer may be a binary copolymer composed of TFE and ethylene, or may be a ternary copolymer composed of TFE and a comonomer copolymerizable with ethylene (e.g., a TFE / ethylene / HFP copolymer). The TFE / ethylene copolymer is also preferably a TFE / ethylene / HFP copolymer containing polymerization units based on HFP. The TFE / ethylene / HFP copolymer preferably has a TFE / ethylene / HFP molar ratio of 40 to 65 / 30 to 60 / 0.5 to 20, more preferably 40 to 65 / 30 to 60 / 0.5 to 10.

[0038] In this specification, "melt-moldable" preferably means that the melt flow rate (MFR) is 1 to 100 g / 10 min. The MFR of the fluororesin (A) is more preferably 5 to 70 g / 10 min, even more preferably 10 to 60 g / 10 min. Since this can suppress spark generation and increase the foaming rate, it is even more preferably 15 to 50 g / 10 min, even more preferably 20 to 45 g / 10 min, and particularly preferably 30 to 45 g / 10 min. The above MFR is a value measured in accordance with ASTM D-1238 using a die with a diameter of 2.1 mm and a length of 8 mm at 372°C and a load of 5 kg.

[0039] The fluororesin (A) may contain a fluororesin that is not melt-moldable in addition to a melt-moldable fluororesin. When the fluororesin (A) contains a fluororesin that is not melt-moldable, the content thereof is preferably 0.001 to 3.0 mass% based on the total amount of the fluororesin (A). In this specification, "not melt-moldable" means that the MFR is less than 1 g / 10 min. The MFR is preferably 0.1 g / 10 min or less.

[0040] Examples of fluororesins that cannot be melt-molded include polytetrafluoroethylene (PTFE). Also, FEP, PFA, ETFE, PCTFE, PVDF, and the like, which are exemplified as melt-moldable fluororesins, can also be used. One or more of these can be used. Of these, PTFE is preferred. FEP and the like are considered to be non-melt-moldable fluororesins when their MFR is less than 1 g / 10 min, but are considered to be melt-moldable fluororesins when their MFR is 1 g / 10 min or more.

[0041] In the present disclosure, PTFE may be a tetrafluoroethylene (TFE) homopolymer, or a modified polytetrafluoroethylene (modified PTFE) obtained from TFE and a minor comonomer. TFE homopolymer is obtained by polymerizing only tetrafluoroethylene (TFE) as a monomer. The minor comonomer in the modified PTFE is not particularly limited as long as it is a fluorine-containing compound copolymerizable with TFE, and examples thereof include perfluoroolefins such as hexafluoropropene (HFP); perfluorovinyl ethers (PFVEs) such as the above-mentioned various PAVEs; fluorodioxoles; trifluoroethylene; vinylidene fluoride; and the like. In the modified PTFE, the content of the minor monomer units derived from the minor monomers in the total monomer units is usually in the range of 0.001 to 1.0% by mass. In this specification, the "content (% by mass) of minor monomer units in all monomer units" means the mass fraction (% by mass) of the minor monomers from which the minor monomer units are derived in the monomers from which the "total monomer units" are derived, i.e., in the total amount of monomers constituting the fluoropolymer.

[0042] In terms of heat resistance and electrical properties, the standard specific gravity (SSG) of PTFE is preferably 2.15 to 2.30, more preferably 2.25 or less, and even more preferably 2.22 or less. High-molecular-weight PTFE with an SSG of less than 2.15 does not eliminate the effects of the present disclosure, but is difficult to manufacture and is impractical. The SSG is a value measured using the underwater displacement method in accordance with ASTM D4895-89. When the SSG of PTFE is low, the effect of increasing the biaxial elongational viscosity can be exerted with a small amount of addition. When the SSG is high, the above effect can be exerted by increasing the amount of addition.

[0043] PTFE can be prepared by known methods such as emulsion polymerization and suspension polymerization, with emulsion polymerization being preferred. If PTFE aggregates are present in the resin composition for foam molding of the present disclosure, sparkouts may occur frequently during wire coating molding, potentially increasing the reject rate. Therefore, the average primary particle diameter of PTFE is preferably 50 to 800 nm, more preferably 50 to 500 nm. The average primary particle diameter of PTFE was determined by measuring the transmittance of projected light at a wavelength of 500 nm per unit length for a polymer latex diluted with water to a solids content of 0.22% by mass, and then measuring the unidirectional diameter in a transmission electron microscope photograph. Based on this calibration curve of the transmittance and the number-average primary particle diameter of PTFE.

[0044] The fluororesin (A) can be synthesized by polymerizing the monomer components using a conventional polymerization method, such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or gas phase polymerization. A chain transfer agent such as methanol may be used in the polymerization reaction. The fluororesin (A) may also be produced by polymerization and isolation without using a metal ion-containing reagent.

[0045] The fluororesin (A) is not particularly limited, but may be any of the following: -CF ３ , -CF ２ may have a terminal group such as -H, ３It is preferable that the fluororesin has a terminal group. The fluororesin having such a terminal group can be obtained by a fluorination treatment. The fluororesin that has not been fluorinated has no terminal groups such as —COOH, —CH ２ OH, -COF, -CONH ２ The fluororesin (A) may have thermally and electrically unstable terminal groups such as -CF, ... ２ The total number of H terminal groups is 1 x 10 carbon atoms. ６ More preferably, the number of unstable terminal groups is 50 or less per unit area. If the number exceeds 50, molding defects may occur. The number of unstable terminal groups is more preferably 20 or less, and even more preferably 10 or less. In this specification, the number of unstable terminal groups is a value obtained by infrared absorption spectroscopy. The unstable terminal groups and -CF ２ No H terminal groups, all -CF ３ It may also be a terminal group.

[0046] The fluorination treatment can be carried out by contacting a non-fluorination-treated fluororesin with a fluorine-containing compound. The fluorine-containing compound is not particularly limited, but examples thereof include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions. Examples of fluorine radical sources include F ２ Gas, CoF ３ , AgF ２ , U.F. ６ , OF ２ , N ２ F ２ , C.F. ３ OF and halogen fluorides (e.g., IF ５ , ClF ３ These may be used alone or in combination of two or more. ２The fluorine radical source such as a gas may be of 100% concentration, but is preferably mixed with an inert gas and diluted to 5 to 50 mass %, preferably 15 to 30 mass % before use. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint. The conditions for the fluorination treatment are not particularly limited, and the molten fluororesin may be brought into contact with the fluorine-containing compound, but the treatment can usually be carried out at a temperature below the melting point of the fluororesin, preferably 20 to 220°C, more preferably 100 to 200°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 20 hours. The fluorination treatment is carried out by subjecting an unfluorinated fluororesin to fluorine gas (F ２ It is preferable to bring the material into contact with a gas.

[0047] The fluororesin (A) is not particularly limited, but since it provides a foamed molded article with excellent heat resistance and a wide continuous use temperature range, it is desirable that the melting point be 200°C or higher, the molding temperature be 250°C or higher, and the thermal decomposition temperature be 300°C or higher. Furthermore, the melting point is more preferably 250°C or higher, and preferably 320°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 even more preferably 400°C or higher. The upper limits of the melting point, molding temperature, and thermal decomposition temperature are 600°C or lower. In this specification, the melting point is a temperature measured by a differential scanning calorimeter (DSC), the molding temperature is a temperature that is generally recommended and suitable for molding, at which the resin has fluidity and does not undergo resin degradation such as discoloration, and the thermal decomposition temperature is the temperature at which 1% weight loss occurs when heated in air at 10°C / min using TG (thermal weight change measurement). However, this does not include the weight loss due to the evaporation of contained water and water of crystallization observed between 100° C. and 200° C. Having fluidity means that the MFR is 0.0001 or more at the temperature.

[0048] In order to reduce signal loss in the communication cable, the dielectric constant of the fluororesin (A) is preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and most preferably 2.1 or less. The lower limit is 1.0 or more. Similarly, the dielectric loss tangent is preferably 0.01 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and most preferably 0.0005 or less. The lower limit is 0.0001 or more. The dielectric constant and dielectric loss tangent of the fluororesin (A) are measured by a cavity resonator method at a frequency of 6 GHz.

[0049] The content of the fluororesin (A) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 97% by mass or more. The upper limit is preferably 99.99% by mass or less, more preferably 99.85% by mass or less, and even more preferably less than 99.85% by mass.

[0050] The resin composition for foam molding of the present disclosure may contain a resin different from the fluororesin (A). Examples of resins different from the fluororesin (A) include general-purpose resins such as polyethylene resin, polypropylene resin, vinyl chloride resin, and polystyrene resin; and engineering plastics such as nylon, polycarbonate, polyetheretherketone resin, polyphenylene sulfide resin, polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherketone (PEK), and polyetheretherketoneketone (PEEKK), polyethersulfone (PES), liquid crystal polymer (LCP), polysulfone (PSF), amorphous polyarylate (PAR), polyethernitrile (PEN), thermoplastic polyimide (TPI), polyimide (PI), polyetherimide (PEI), and polyamideimide (PAI). These may be used alone or in combination.

[0051] The content of the resin different from the fluororesin (A) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. The lower limit is not particularly limited, and may be 0% by mass.

[0052] The resin composition for foam molding of the present disclosure contains a tetrapyrrole cyclic compound (B) as a foam nucleating agent.

[0053] Tetrapyrrole cyclic compounds (B) are classified into three types based on their skeletons: phthalocyanines, chlorins, and bacteriochlorins. They can also form complexes with metals such as copper, iron, and magnesium.

[0054] As the tetrapyrrole cyclic compound (B), compounds having a phthalocyanine skeleton are preferred, metal phthalocyanines are more preferred, and copper phthalocyanines are even more preferred, in view of their excellent function as a foam nucleating agent.

[0055] It is preferable that the tetrapyrrole cyclic compound (B) does not decompose and is insoluble or not melted in the fluororesin (A) at the molding temperature during foam molding. That is, it is preferable that the tetrapyrrole cyclic compound (B) is solid in the composition when the foam molding resin composition of the present disclosure is foam molded. This allows the compound to fully function as a foam nucleating agent. Whether the tetrapyrrole cyclic compound (B) satisfies this condition can be confirmed by observing, using a polarizing microscope equipped with a hot stage, whether the tetrapyrrole cyclic compound (B) remains solid when heated to a predetermined temperature.

[0056] The crystallite size of the tetrapyrrole cyclic compound (B) measured by X-ray diffraction (XRD) is preferably greater than 100 Å, more preferably greater than 140 Å, and even more preferably greater than 200 Å. This allows for the formation of an ideal crystal lattice with minimal distortion, promoting bubble generation. The upper limit of the crystallite size is preferably 10,000 Å or less, more preferably 5,000 Å or less, and even more preferably 1,000 Å or less. XRD is performed using an X-ray diffractometer (Smart Lab, manufactured by Rigaku Corporation) and measurement and analysis software (Smart Lab Studio II), and powder is measured. CuKα with a wavelength of 1.54 Å is used as the X-ray source, and the diffraction angle (2θ) is 5° to 90°. The crystallite size is calculated using the Scherrer formula from the largest half-width of the obtained diffraction peak. D = K × λ / (β × cos θ) ... Scherrer's formula D: crystallite size (Å) K: Scherrer constant λ: X-ray wavelength (Å) β: half width of diffraction peak (rad) θ: ½ of diffraction angle (rad) Scherrer constant (K) = 0.94, X-ray wavelength (λ) = 1.5418. If the obtained diffraction spectrum does not have a diffraction peak attributable to a crystalline structure, it is considered not to have a crystalline structure.

[0057] The tetrapyrrole cyclic compound (B) preferably has a volatilization amount of 7.0% by mass or less at 330°C, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, and particularly preferably 1.0% by mass or less. This suppresses the generation of eye discharge (deposits) that can cause molding defects, enabling long-term molding, such as wire molding. The lower limit is not particularly limited and may be 0% by mass. The volatilization amount is calculated by measuring the mass loss when a sample is held in an electric furnace at 330°C for 1 hour and dividing the mass loss by the mass before holding x 100.

[0058] In order to form more uniform bubbles, the tetrapyrrole cyclic compound (B) is preferably dispersed in the fluororesin (A) with a center-of-gravity distance of 5.0 μm or less. The upper limit of the center-of-gravity distance is more preferably 3.0 μm or less, and even more preferably 2.0 μm or less, and the lower limit is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 0.5 μm or more.

[0059] In order to form more uniform bubbles, the tetrapyrrole cyclic compound (B) is added to the fluororesin (A) at a density of 15,000 bubbles / mm ２ The lower limit of the density is preferably 30,000 particles / mm ２ More preferably, 120,000 pieces / mm ２ The upper limit is preferably 10,000,000 particles / mm ２ Less than or equal to 5,000,000 particles / mm ２ More preferably, 1,000,000 pieces / mm ２ The following is the result.

[0060] In order to form more uniform bubbles, the tetrapyrrole cyclic compound (B) is preferably dispersed in the fluororesin (A) with a particle size of 4.0 μm or less. The upper limit of the particle size is preferably 3.0 μm or less, and even more preferably 2.0 μm or less, and the lower limit is preferably 0.001 μm or more, more preferably 0.01 μm or more, and even more preferably 0.1 μm or more.

[0061] The dispersion state (center-of-gravity distance, density, particle size) of the tetrapyrrole cyclic compound (B) in the fluororesin (A) is calculated by photographing a cross section of a resin composition containing the fluororesin (A) and the tetrapyrrole cyclic compound (B) with a laser microscope (Keyence Corporation's shape analysis laser microscope (VK-X1000)) at a magnification of 150x and processing the image. The center-of-gravity distance and particle size are average values ​​for 100 particles.

[0062] The melting temperature (melting point) of the tetrapyrrole cyclic compound (B) is preferably 300°C or higher, more preferably 320°C or higher, and even more preferably 350°C or higher. Within this range, the compound is unlikely to melt even at the molding temperature during foam molding, and can fully function as a foam nucleating agent. There is no particular upper limit, but a temperature of 1000°C or lower is preferred.

[0063] The thermal decomposition temperature of the tetrapyrrole cyclic compound (B) is preferably 270°C or higher, more preferably 320°C or higher, and even more preferably 350°C or higher. Within this range, the compound is less likely to decompose even at the molding temperature during foam molding. Therefore, adverse effects due to the decomposition of the tetrapyrrole cyclic compound (B) (e.g., deterioration of electrical properties, bursting of cells, and breakage of the coating during wire molding) can be suppressed. The upper limit is not particularly limited, but 1000°C or lower is preferred.

[0064] The melting temperature (melting point) and thermal decomposition temperature of the tetrapyrrole cyclic compound (B) can be measured by the same method as that for the fluororesin (A) described above.

[0065] In the resin composition for foam molding of the present disclosure, the content of the tetrapyrrole cyclic compound (B) is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, even more preferably 0.5 part by mass or more, and is preferably 20 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 2.0 parts by mass or less, per 100 parts by mass of the fluororesin (A). If the content of the tetrapyrrole cyclic compound (B) is too low, the effect of adding the tetrapyrrole cyclic compound (B) may not be fully obtained, whereas if the content is too high, the production cost may increase.

[0066] The resin composition for foam molding of the present disclosure may contain a foam nucleating agent other than the tetrapyrrole cyclic compound (B). Examples of foam nucleating agents other than the tetrapyrrole cyclic compound (B) include boron nitride, sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate, barium fluorooctanesulfonate, barium bisphenol phosphate diester, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, sodium benzenephosphonate, 2,6-naphthalenedicarboxylic acid, 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol, N,N'-dioctadecylisophthalamide, sodium benzoate, sodium bis(4-nitrophenyl)phosphate, triaminobenzene derivatives, 1,3,5-tris(2,2-dimethylpropionylamino)-benzene, Pigment Red 254, talc, sodium binaphthyl phosphate, barium t-butyl-binaphthyl phosphate, rosin metal salts, and condensed phosphate esters. Other examples include sulfonic acid, sulfonate salts, phosphonic acid, phosphonate salts, zeolite, ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), OBSH (4,4'-oxybisbenzenesulfonylhydrazide), etc. These can be used alone or in combination of two or more.

[0067] The resin composition for foam molding of the present disclosure may further contain a polyatomic anion-containing inorganic salt, such as those disclosed in U.S. Pat. No. 4,764,538, within the scope of not impairing the effects of the present disclosure.

[0068] The resin composition for foam molding of the present disclosure may contain a conventionally known filler as long as the effects of the present disclosure are not impaired.

[0069] Examples of fillers include graphite, carbon fiber, coke, silica, zinc oxide, magnesium oxide, magnesium sulfate, tin oxide, antimony oxide, calcium carbonate, magnesium carbonate, magnesium hydroxide, glass, talc, mica, aluminum nitride, calcium phosphate, sericite, diatomaceous earth, silicon nitride, fine silica, fumed silica, alumina, zirconia, quartz powder, kaolin, bentonite, and titanium oxide. These may be used alone or in combination. The shape of the filler is not particularly limited, and examples include fibrous, needle-like, columnar, whisker-like, flat, layered, scaly, balloon-like, porous, chopped fiber, powder, granular, and bead-like shapes. Note that the filler is different from the boron nitride and the like mentioned in the foam nucleating agent.

[0070] The resin composition for foam molding according to the present disclosure may further contain other components such as additives, for example, fillers such as glass fiber, glass powder, asbestos fiber, cellulose fiber, and carbon fiber, as well as reinforcing agents, stabilizers, lubricants, pigments, flame retardants, and other additives.

[0071] If the resin composition contains a large amount of a fluorine-based low molecular weight compound, the molten resin may be plasticized during molding, resulting in an increase in sparks. Therefore, it is preferable that the resin composition for foam molding of the present disclosure is substantially free of a fluorine-based low molecular weight compound. Note that "substantially free of a fluorine-based low molecular weight compound" means that the content of a fluorine-based low molecular weight compound is 10 ppm by mass or less.

[0072] The fluorine-based low molecular weight compound is not particularly limited, and examples thereof include fluorine-based compounds having a molecular weight of 1000 or less. Specific examples thereof include perfluoroalkyl acids and perfluorosulfonic acids, and more specific examples thereof include C ８ F １７ COOH and its salts, C ７ F １５ COOH and its salts, C ６ F １３ COOH and its salts, C ８ F １７ SO ３ H and its salts, C６ F １３ SO ３ H and its salts, C ４ F ９ SO ３ H and its salts, C ８ F １７ CH ２ CH ２ -SO ３ H and its salts, C ６ F １３ CH ２ CH ２ -SO ３ H and its salts, C ８ F １７ CH ２ CH ２ OH, C ６ F １３ CH ２ CH ２ OH, etc., and more specifically, {F(CF ２ ) ６ CH ２ CH ２ SO ３} ２ Examples include Ba.

[0073] The content of fluorine-based low molecular weight compounds can be analyzed by the following method: A sample is pulverized by freeze-pulverization, the resulting powder is dispersed in methanol, and extracted by applying ultrasonic waves at 60°C for 2 hours. The extract is quantified using a liquid chromatograph-mass spectrometer (LC-MS / MS), and the value is taken as the content.

[0074] The melt flow rate (MFR) of the resin composition for foam molding of the present disclosure is preferably 1 to 100 g / 10 min. More preferably, it is 5 to 70 g / 10 min, and even more preferably, it is 10 to 60 g / 10 min. Because this can suppress the generation of sparks and increase the foaming rate, it is even more preferably 15 to 50 g / 10 min, even more preferably, 20 to 45 g / 10 min, and particularly preferably, 30 to 45 g / 10 min. The above MFR is a value measured in accordance with ASTM D-1238 using a die with a diameter of 2.1 mm and a length of 8 mm, under a load of 5 kg, at 372°C.

[0075] In order to reduce signal loss in communication cables, the dielectric constant of the resin composition for foam molding of the present disclosure is preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and most preferably 2.1 or less. The lower limit is 1.0 or more. Similarly, the dielectric loss tangent is preferably 0.01 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and most preferably 0.0005 or less. The lower limit is 0.0001 or more. The dielectric constant and dielectric loss tangent of the resin composition for foam molding of the present disclosure are measured by a cavity resonator method at a frequency of 6 GHz using the resin composition before foam molding.

[0076] The resin composition for foam molding of the present disclosure can be suitably used as a foamable composition, and in particular, can be suitably used as a wire covering composition for forming a covering layer of an electric wire.

[0077] A method for producing a foam-molded article of the present disclosure includes a step of foam-molding a foam-molding resin composition of the present disclosure. The foam-molded article of the present disclosure is formed using the foam-molding resin composition of the present disclosure.

[0078] The method for foam-molding the resin composition for foam molding of the present disclosure is not particularly limited, and any conventionally known method can be used. For example, a method in which the resin composition for foam molding of the present disclosure is fed into a screw extruder designed for foaming operations and a continuous gas extrusion method is used may be mentioned.

[0079] The gas used in the gas extrusion method may be, for example, chlorodifluoromethane, nitrogen, carbon dioxide, or a mixture of these gases, and may be introduced into the molten resin in the extruder as a pressurized gas, or may be generated by mixing a chemical foaming agent into the molten resin. The introduced gas dissolves in the molten resin in the extruder.

[0080] Gases dissolved in the resin escape from the melt due to the sudden drop in melt pressure as it exits the extrusion die. The extrudate is then cooled and solidified, for example by immersion in water.

[0081] The foam molded article of the present disclosure has a low dielectric constant, exhibits stable capacitance, and is lightweight, and therefore can be used as a covering material (described below) with stable dimensions such as wire diameter and thickness.

[0082] The total volume of bubbles in the foamed molded article of the present disclosure can be adjusted appropriately depending on the application, for example, by adjusting the amount of gas introduced into the extruder or by selecting the type of gas to be dissolved.

[0083] The foamed molded article of the present disclosure is obtained as a molded article shaped according to the intended use during extrusion from the extruder. The molding method is not particularly limited as long as it is hot melt molding, and examples thereof include extrusion foam molding, injection foam molding, and mold foam molding.

[0084] The shape of the foam molded article of the present disclosure is not particularly limited and can be various shapes, such as a covering material for foamed electric wires, a filament-like shape for wires, a sheet-like shape, a film-like shape, a rod-like shape, or a pipe-like shape. The foam molded article can be used, for example, as an electrical insulating material, a heat insulating material, a sound insulating material, a lightweight structural material such as a floating material, or a shock-absorbing material such as a cushion. The foam molded article is particularly suitable for use as a covering material for foamed electric wires. The resulting foam molded article contains a molten and solidified product of the foam molding resin composition of the present disclosure and bubbles, and the bubbles are preferably uniformly distributed throughout the molten and solidified product. The bubble size is not particularly limited, but is preferably 60 μm or less, and more preferably 30 μm or less. The bubble size is preferably 0.1 μm or more. The foam ratio of the foam molded article is not particularly limited, but is preferably 20% or more. The upper limit of the foam ratio is not particularly limited, but is, for example, 80%.

[0085] The cells in the foamed molded article of the present disclosure may be open cells or closed cells, but closed cells are preferred. Closed cells have the advantages of strong resilience against external pressure, excellent rigidity, shock absorption, and processability, and also preventing moisture and other substances from penetrating into the interior. Closed cells can be formed by the above-mentioned hot melt molding or by any conventionally known method.

[0086] The foamed molded article of the present disclosure is in a foamed state that is advantageous for reducing the dielectric constant, and therefore can be used as an insulating layer for electric wires, semiconductor package substrates, transformers, circuit boards, motors, reactors, transistors, printed circuit boards, semiconductor devices, and electronic components, and can be particularly suitably used as an insulating layer (coating layer) for electric wires.

[0087] The method for producing a foamed electric wire of the present disclosure includes a step of forming a foamed insulating layer (covering layer) on a conductor using the foam-molding resin composition of the present disclosure. The foamed electric wire of the present disclosure has a conductor and a foamed insulating layer (covering layer) formed on the conductor using the foam-molding resin composition of the present disclosure.

[0088] The method for forming a foamed insulating layer (coating layer) on a conductor using the foam-molding resin composition of the present disclosure is not particularly limited, and examples include a method in which a gas soluble in a molten fluororesin (molten resin) is used, the foam-molding composition of the present disclosure is introduced into a screw extruder designed for foaming operations, and a continuous gas injection method is used. The gas can be the same as that used in the method for producing a foam-molded article.

[0089] The foamed electric wire of the present disclosure has a foamed insulation layer in a foamed state that is advantageous for achieving a low dielectric constant, and therefore can suppress signal attenuation compared to conventional electric wires.

[0090] Examples of materials that can be used for the conductor (core wire) include metal conductor materials such as copper and aluminum, and carbon. The conductor may be made of a single material, or the surface may be plated with silver, tin, or the like. The conductor preferably has a diameter of 0.02 to 3 mm. The conductor diameter is more preferably 0.04 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. The conductor diameter is more preferably 2 mm or less. The conductor may be a solid wire or a stranded wire made by twisting together multiple conductors. The shape of the conductor is not particularly limited, and examples include a flat shape and rectangular wire.

[0091] Specific examples of the conductor (core wire) include AWG (American Wire Gauge)-46 (solid copper wire with a diameter of 40 micrometers), AWG-42 (solid copper wire with a diameter of 64 micrometers), AWG-36 (solid copper wire with a diameter of 127 micrometers, a wire with a total diameter of 153 micrometers formed by twisting seven copper wires with a diameter of 51 micrometers), AWG-30 (solid copper wire with a diameter of 254 micrometers, a wire with a total diameter of 306 micrometers formed by twisting seven copper wires with a diameter of 102 micrometers), AWG-27 ​​(solid copper wire with a diameter of 361 micrometers), AWG-26 (solid copper wire with a diameter of 404 micrometers), AWG-24 (solid copper wire with a diameter of 510 micrometers), and AWG-22 (solid copper wire with a diameter of 635 micrometers).

[0092] The thickness of the foamed insulation layer (coating layer) is preferably 0.01 to 3.0 mm, and also preferably 2.0 mm or less.

[0093] The surface roughness of the foamed insulation layer (coating layer) is preferably 9.0 μm or less, more preferably 8.0 μm or less, and even more preferably 7.0 μm or less. There is no particular lower limit, but it is usually 1.0 μm or more. The surface roughness is a value obtained by measuring the surface of the foamed electric wire using a laser microscope (VK-X1000) manufactured by Keyence Corporation, correcting the obtained image data by specifying the area of ​​the electric wire using quadratic curve correction for surface shape correction, and then calculating the surface roughness in a 500 × 2000 μm area.

[0094] The number of sparks on the foam insulation layer (coating layer) was 200 / 10 ４ m or less is preferable, and 80 pieces / 10 ４ m or less is more preferable, and 30 / 10 ４ The lower limit is not particularly limited, and is preferably 0 / 10 ４ The number of sparks is a value obtained by measuring at a voltage of 1500 V using a Beta LaserMike Sparktester HFS1220.

[0095] The foamed electric wire of the present disclosure can be used as cables for connecting computers and their peripheral devices, cables for communicating high-capacity video and audio at high speed, cables for connecting servers in a data center, for example, LAN cables, USB cables, Lightning cables, Thunderbolt cables, CATV cables, HDMI (registered trademark) cables, QSFP cables, aerospace cables, underground power transmission cables, submarine power cables, high-voltage cables, superconducting cables, wrapped electric wires, automotive wires, wire harnesses and electrical components, electric wires for robots and factory automation (FA), electric wires for office automation equipment, electric wires for information equipment (optical fiber cables, audio cables, etc.), internal wiring for communication base stations, high-current internal wiring (inverters, power conditioners, storage battery systems, etc.), internal wiring for electronic devices, wiring for small electronic devices and mobile devices, wiring for moving parts, internal wiring for electrical equipment, internal wiring for measuring instruments, power cables (for construction, wind power / solar power generation, etc.), control / instrumentation wiring cables, motor cables, etc.

[0096] The foamed electric wire of the present disclosure may 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 coated on the outer layer, or even a three-layer structure (skin-foam-skin) in which a non-foamed layer is coated on a skin-foam outer layer. The non-foamed layer is not particularly limited, and may be a resin layer made of a resin such as a TFE / HFP copolymer, a TFE / PAVE copolymer, a TFE / ethylene copolymer, a vinylidene fluoride polymer, a polyolefin resin such as polyethylene (PE), or polyvinyl chloride (PVC).

[0097] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0098] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0099] The various properties in this specification were measured by the following methods. (Measurement of the number of unstable terminal groups) The pellets were rolled using a hydraulic press to prepare a film with a thickness of about 0.3 mm, and the film was analyzed using an FT-IR Spectrometer 1760X (manufactured by Perkin-Elmer). A difference spectrum was obtained from a standard sample (a sample that had been sufficiently fluorinated so that no substantial difference was observed in the spectrum), and the absorbance of each peak was read and calculated based on the number of carbon atoms (1 × 10) according to the following formula: ６ The number of unstable terminal groups per carbon atom was calculated. ６ Number of unstable terminal groups per unit = (I × K) / t (I: absorbance, K: correction coefficient, t: film thickness (unit: mm)) The correction coefficient (K) for each unstable terminal group is as follows: -COF (1884 cm －１ )...405 -COOH (1813cm －１ , 1775 cm －１ )...455 -COOCH ３ (1795 cm －１ )...355 -CONH ２ (3438 cm －１ )...480 -CH ２ OH (3648 cm －１ )...2325

[0100] (-CF ２ Measurement of the number of H-terminal groups) A nuclear magnetic resonance spectrometer AC300 (manufactured by Bruker-Biospin) was used, and the measurement temperature was set at the melting point of the fluororesin (A) + 20°C. １９ F-NMR measurement was carried out, and -CF ２ It was calculated from the integral value of the peak due to the presence of H groups and the integral values ​​of other peaks.

[0101] (SSG) Measured based on the immersion method in accordance with ASTM D4895-89.

[0102] (Melting Point) The melting point was determined as the temperature corresponding to the peak measured at a temperature rise rate of 10° C. / min using a DSC (RDC220 manufactured by Seiko Denshi Co., Ltd.).

[0103] (Thermal Decomposition Temperature) The temperature at which a sample loses 1% of its weight when heated in air at 10° C. / min was measured by TG.

[0104] (MFR) The MFR was measured in accordance with ASTM D-1238 using a KAYENESS Melt Indexer Series 4000 (manufactured by Yasuda Seiki Co., Ltd.) with a die having a diameter of 2.1 mm and a length of 8 mm at 372° C. and a load of 5 kg.

[0105] The examples and comparative examples were carried out in the following manner.

[0106] (Preparation of FEP pellets) Fluorinated FEP pellets were prepared in the same manner as in Example 1 of JP 2017-128119 A. The obtained pellets (TFE / HFP / PPVE copolymer) had a mass ratio of TFE / HFP / PPVE = 87.9 / 11.1 / 1.0, a melting point of 261°C, an MFR of 38 g / 10 min, and an unstable terminal group and -CF ２ Total number of carbon atoms and H terminal groups: 1 x 10 ６ There were 0 per piece.

[0107] (Preparation of premix pellets for electric wire molding (step 1)) FEP pellets (MFR: 38 g / 10 min) and additives were kneaded in a twin-screw extruder with the cylinder and die sections set to the temperatures shown in Table 1 to prepare masterbatch pellets. The additive concentration in the masterbatch pellets was about 2 to 5 times the additive concentration in the premix pellets. The obtained masterbatch pellets and FEP pellets were mixed in a mixer to prepare premix pellets with the desired additive concentration.

[0108]

[0109] (Evaluation of Foamed Electric Wire Molding (Step 2)) The foam molding extruder used was composed of an extruder and system manufactured by Hijiri Seisakusho Co., Ltd., a gas injection nozzle manufactured by Micodia, and a crosshead manufactured by Unitec. Table 2 shows the configuration and conditions of the extruder, and Table 3 shows the extruder temperature. Nitrogen gas was introduced as a foaming agent into the melt-kneading section of this foam molding extruder, and the premix pellets (composition) prepared above were supplied and extrusion foam molded. A 0.30 mm diameter core wire was covered with a foam molded product so that the outer diameter was 0.80 mm and the capacitance was 86 pf / m, thereby obtaining a foamed electric wire. The outer diameter of the electric wire was measured using a LASER MICRO DIAMETER LDM-303H-XY (manufactured by Takikawa Engineering Co., Ltd.). The capacitance was measured using a CAPAC300 19C (manufactured by Zumbach).

[0110]

[0111]

[0112] (Bubble Size) An SEM image of the cross section of the foamed electric wire was taken, and the circle equivalent diameter of each bubble was calculated by image processing. The average of 100 bubbles was taken as the bubble size.

[0113] (Expansion ratio) It was calculated by (specific gravity of fluororesin - specific gravity of foamed molded product) / specific gravity of fluororesin) x 100.

[0114] (Smoke) The upper part of the resin discharge port of the die of the extruder was visually observed to confirm the presence or absence of volatile components.

[0115] (Eye discharge) The presence or absence of deposits at the resin discharge port of the die of the extruder was confirmed by visual inspection.

[0116] (Surface condition) The degree of snagging (protrusions) felt when checking the surface of the foamed electric wire was evaluated according to the following criteria: Very good: No snagging Good: Little snagging Fair: Some snagging Poor: Much snagging

[0117] (Surface roughness) The surface of the foamed electric wire was measured using a laser microscope (VK-X1000) manufactured by Keyence Corporation, and the obtained image data was corrected by specifying the area of ​​the electric wire using quadratic curve correction for surface shape correction, and then the surface roughness in an area of ​​500 × 2000 μm was calculated.

[0118] (Number of sparks) 10 ４ The number of sparks per meter was measured using a Beta LaserMike Sparktester HFS1220 at a voltage of 1500V.

[0119] (Content of Fluorine-Based Low-Molecular-Weight Compounds) The sample was pulverized by freeze-pulverization, and the resulting powder was dispersed in methanol and extracted by applying ultrasonic waves for 2 hours at 60° C. The extract was quantified using a liquid chromatograph-mass spectrometer (LC-MS / MS), and the content was determined as the value.

[0120] (Dielectric Constant, Dielectric Loss Tangent) Premix pellets (resin composition before foam molding) having a desired additive concentration were measured by a cavity resonator method at a frequency of 6 GHz.

[0121] (State of Tetrapyrrole Cyclic Compound (B) at Molding Temperature) When the temperature was raised to a predetermined temperature, it was observed using a polarizing microscope equipped with a hot stage whether the tetrapyrrole cyclic compound (B) remained solid.

[0122] Example 1 In step 1, pellets were prepared by adding 1 part by mass of copper phthalocyanine (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: no peak detected below 350°C, thermal decomposition temperature: 388°C) to 100 parts by mass of FEP pellets. In step 2, foamed electric wire molding was carried out at an extrusion speed (screw rotation speed) of 15 rpm, a nitrogen gas flow rate of 16 cc / min, and a take-up speed of 100 m / min, to obtain a foamed electric wire with an outer diameter of 0.80 mm and a capacitance of 86 pF / m. No smoke or eye discharge was observed during molding, and the number of sparks was 5 / 10. ４The results were very good, at 4.5 μm. Analysis of the obtained foamed electric wire revealed a good expansion rate of 43%, a good bubble size of 21 μm, an extremely good surface feel, and a very good surface roughness of 6.8 μm. Furthermore, at the molding temperature during foam molding, the copper phthalocyanine did not decompose and was insoluble or molten in FEP. Furthermore, no fluorine-based low-molecular-weight compounds were detected in the pellets used or in the coating layer of the foamed electric wire produced. Fluorine-based low-molecular-weight compounds were also not detected in the comparative examples described below. Furthermore, the formation of closed bubbles was confirmed from SEM images taken when the bubble size was calculated. Closed bubbles were also formed in the following comparative examples 1, 3, and 4.

[0123] Comparative Example 1 A foamed electric wire was produced in the same manner as in Example 1, except that boron nitride (MGP manufactured by Denka Co., Ltd.) was used as an additive. No smoke or eye discharge was observed during molding, but the condition of the electric wire surface was poor, and the number of sparks was 300 or more per 10 ４ Analysis of the obtained foamed electric wire revealed that the bubble size was large at 36 μm and the surface roughness was also very poor at 12.4 μm.

[0124] Comparative Example 2 An attempt was made to produce a foamed electric wire in the same manner as in Example 1, except that Irgaclear XT386 (a polypropylene transparent nucleating agent manufactured by BASF) was used as the additive. However, smoke and eye discharge frequently occurred, and the desired foamed electric wire could not be obtained.

[0125] Comparative Example 3 A foamed electric wire was produced in the same manner as in Example 1, except that 0.5 parts by mass of potassium titanate (Tismo D manufactured by Otsuka Chemical Co., Ltd.) was used as an additive. No smoke or eye discharge was observed during molding, but the condition of the electric wire surface was somewhat poor, and the number of sparks was 100 or more per 10 ４ Analysis of the obtained foamed electric wire revealed that the bubble size was 27 μm, which was good, but the surface roughness was 10.1 μm, which was poor.

[0126] Comparative Example 4 A foamed electric wire was produced in the same manner as in Example 1, except that no additive was used. No smoke or eye discharge was observed during molding, and the number of sparks was 0 / 10. ４However, analysis of the foamed electric wire showed that the size of the bubbles was as large as 103 μm.

[0127] Comparative Example 5 A foamed electric wire was produced in the same manner as in Example 1, except that 0.01 parts by mass of sodium fluorobutanesulfonate (a fluorine-based surfactant) and 0.4 parts by mass of boron nitride were used as additives. No smoke or eye discharge was observed during molding, but the condition of the electric wire surface was poor, and the number of sparks was 100 or more per 10 ４ Analysis of the obtained foamed electric wire revealed that the bubble size was 30 μm, which was good, but the surface roughness was 12.3 μm, which was very poor.

[0128]

Claims

1. A resin composition for foam molding, comprising a fluororesin (A) and a tetrapyrrole-based cyclic compound (B).

2. The foam-molding resin composition according to claim 1, wherein the fluororesin (A) is a melt-moldable fluororesin.

3. A resin composition for foam molding according to claim 1 or 2, wherein the fluororesin (A) is at least one selected from the group consisting of tetrafluoroethylene / hexafluoropropylene copolymers and tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers.

4. The resin composition for foam molding according to any one of claims 1 to 3, wherein the fluororesin (A) is a tetrafluoroethylene / hexafluoropropylene copolymer.

5. The resin composition for foam molding according to any one of claims 1 to 4, wherein the fluororesin (A) has been fluorinated.

6. The resin composition for foam molding according to any one of claims 1 to 5, wherein the content of the fluororesin (A) is 80 to 99.99 mass %.

7. The resin composition for foam molding according to any one of claims 1 to 6, wherein the content of the fluororesin (A) is 97% by mass or more and less than 99.85% by mass.

8. The resin composition for foam molding according to any one of claims 1 to 7, which is substantially free of fluorine-containing low molecular weight compounds.

9. The resin composition for foam molding according to any one of claims 1 to 8, wherein the tetrapyrrole cyclic compound (B) has a phthalocyanine skeleton.

10. The resin composition for foam molding according to any one of claims 1 to 9, wherein the tetrapyrrole cyclic compound (B) is a metal phthalocyanine.

11. The resin composition for foam molding according to any one of claims 1 to 10, wherein the tetrapyrrole cyclic compound (B) is copper phthalocyanine.

12. The resin composition for foam molding according to any one of claims 1 to 11, wherein the content of the tetrapyrrole cyclic compound (B) is 0.1 to 20 parts by mass per 100 parts by mass of the fluororesin (A).

13. The resin composition for foam molding according to any one of claims 1 to 12, wherein the content of the tetrapyrrole cyclic compound (B) is 0.5 to 2.0 parts by mass per 100 parts by mass of the fluororesin (A).

14. A foamed molded article formed using the foam-molding resin composition according to any one of claims 1 to 13.

15. A method for producing a foamed molded article, comprising a step of foam-molding the resin composition for foam molding according to any one of claims 1 to 13.

16. A foamed electric wire having a conductor and a foamed insulating layer formed on the conductor using the foam molding resin composition according to any one of claims 1 to 13.

17. A method for producing a foamed electric wire, comprising the step of forming a foamed insulating layer on a conductor using the foam-molding resin composition according to any one of claims 1 to 13.

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