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

Abstract

To provide a resin composition for foam molding, a foam molded body, a method for producing a foam molded body, a foamed electric wire, and a method for producing a foamed electric wire, enabling formation of sufficiently fine bubbles and exhibiting superior appearance.SOLUTION: A resin composition for foam molding comprising a fluororesin (A) and a tetrapyrrole cyclic compound (B).SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

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

[0003] Foam molding is known as a method for reducing the weight of fluororesin and improving its electrical properties. 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). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-045931 [Patent Document 2] Japanese Patent Publication No. 2022-028640 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-206745 Summary of the Invention [Problem to be solved by the invention]

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

[0007] Patent Document 1 also discloses a method of miniaturizing bubbles by blending a salt such as perfluoroalkylsulfonic acid together with boron nitride. However, there is room for improvement in that blending a fluorine-based surfactant such as perfluoroalkylsulfonic acid plasticizes the molten resin during molding, which can cause sparks and impair the appearance.

[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. [Means for solving the problem]

[0009] The present disclosure (1) is a resin composition for foam molding containing a fluororesin (A) and a tetrapyrrole 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) is 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), wherein 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 resin composition for foam molding 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 insulating 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). [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[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 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, which allows for the formation of finer bubbles than when boron nitride is used, making it possible to apply the composition to applications requiring thin molded articles, such as thin electric wires. Furthermore, compared to when a fluorochemical surfactant is used, spark generation can be suppressed and appearance defects can be reduced, enabling long-term molding, such as wire molding. Furthermore, not only is the generation of sparks suppressed, but the surface roughness is reduced, resulting in good electrical properties.

[0030] The fluororesin (A) may be any resin containing fluorine, but is preferably a melt-processable fluororesin. Examples of melt-processable fluororesins include tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymers (FEP), TFE / perfluoro(alkyl vinyl ether) (PAVE) copolymers (PFA), 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, and TFE / HFP / VdF copolymers. These may 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.

[0032] The fluororesin (A) may contain 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 monomers 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 of the non-fluorine-containing monomer include 3-dicarboxylic acid anhydride (hereinafter also referred to as "NAH"), succinic anhydride, fumaric anhydride, maleic anhydride, and other non-fluorine-containing monomers having an acid anhydride residue; vinyl sulfonic acid, and other non-fluorine-containing monomers having a sulfo group; glycidyl vinyl ether, glycidyl allyl ether, and other non-fluorine-containing monomers having an epoxy group (glycidyl group); aminoalkyl vinyl ether, aminoalkyl allyl ether, and other non-fluorine-containing monomers having an amino group; (meth)acrylamide, methylolacrylamide, and other non-fluorine-containing monomers having an amide group; and acrylonitrile, methacrylonitrile, and other non-fluorine-containing monomers having a nitrile group.

[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, due to its excellent heat resistance, and is also preferably a perfluororesin, due to its superior electrical properties.

[0035] The TFE / HFP copolymer preferably has a TFE / HFP mass ratio of 80-97 / 3-20, more preferably 84-92 / 8-16. The TFE / HFP copolymer may be a binary copolymer made of TFE and HFP, or may be a ternary copolymer made of TFE and a comonomer copolymerizable with HFP (for example, a TFE / HFP / PAVE copolymer). 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 mass ratio of TFE / HFP / PAVE of 70-97 / 3-20 / 0.1-10, and more preferably 81-92 / 5-16 / 0.3-5.

[0036] The TFE / PAVE copolymer preferably has a TFE / PAVE mass ratio 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 consisting of TFE and ethylene, or may be a ternary copolymer consisting of TFE and a comonomer copolymerizable with ethylene (for example, 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 40-65 / 30-60 / 0.5-20, more preferably 40-65 / 30-60 / 0.5-10.

[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, and 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, since this can suppress the generation of sparks and increase the foaming rate. The MFR is a value measured in accordance with ASTM D-1238 using a die having a diameter of 2.1 mm and a length of 8 mm at 372° C. under a load of 5 kg.

[0039] The fluororesin (A) may contain a fluororesin that cannot be melt-formed in addition to a melt-formable fluororesin. When the fluororesin (A) contains a fluororesin that cannot be melt-formed, 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, and preferably 0.1 g / 10 min or less.

[0040] Examples of fluororesins that cannot be melt-molded include polytetrafluoroethylene (PTFE). Also usable are FEP, PFA, ETFE, PCTFE, PVDF, and other fluororesins that can be melt-molded. These can be used alone or in combination of two or more. PTFE is particularly preferred. In addition, FEP, etc. is a fluororesin that cannot be melt-molded if its MFR is less than 1g / 10min, and is a fluororesin that can be melt-molded if its MFR is 1g / 10min 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 modified PTFE is not particularly limited as long as it is a fluorine-containing compound that can be copolymerized with TFE, and examples thereof include perfluoroolefins such as hexafluoropropene (HFP), perfluorovinyl ethers (PFVEs) such as the above-mentioned various PAVEs, fluorodioxoles, trifluoroethylene, and vinylidene fluoride. 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 total amount of monomers from which the "total monomer units" are derived, i.e., 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 not practical. The SSG is a value measured by the immersion method in accordance with ASTM D4895-89. When the SSG of PTFE is low, the effect of increasing the biaxial extensional viscosity can be achieved with a small amount of added PTFE.When the SSG is high, the effect can be achieved by increasing the amount of added PTFE.

[0043] PTFE can be prepared by known methods such as emulsion polymerization and suspension polymerization, but emulsion polymerization is preferred as the polymerization method. If PTFE aggregates are present in the resin composition for foam molding of the present disclosure, spark outs may occur frequently during wire coating molding, increasing the reject rate. Therefore, the average primary particle size of PTFE is preferably 50 to 800 nm, and 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 of a polymer latex diluted with water to a solid content of 0.22% by mass, and then based on a calibration curve of the number-average primary particle diameter of PTFE obtained by measuring the unidirectional diameter in a transmission electron microscope photograph in advance and the transmittance.

[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 have terminal groups such as -CF3 or -CF2H at at least one site of the polymer main chain or the polymer side chain, and preferably has -CF3 terminal groups. Fluororesins having such terminal groups can be obtained by fluorination treatment. Fluororesins that have not been fluorinated may have thermally and electrically unstable terminal groups such as -COOH, -CH2OH, -COF, and -CONH2 (hereinafter, such terminal groups may be referred to as "unstable terminal groups"). Such unstable terminal groups can be reduced by the above-mentioned fluorination treatment. It is preferable that the fluororesin (A) contains few or no unstable terminal groups, and the total number of the above four types of unstable terminal groups and -CF2H terminal groups is less than 1 x 10 carbon atoms. 6 More preferably, the number of unstable terminal groups per unit area is 50 or less. If the number exceeds 50, molding defects may occur. The number of unstable terminal groups per unit area 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 -CF2H terminal groups may be absent, and all may be -CF3 terminal groups.

[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 may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions. Examples of the fluorine radical source include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogen fluorides (e.g., IF5, ClF3). These may be used alone or in combination. The fluorine radical source such as F2 gas may be 100% concentrated, 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 fluorine-containing compound may be brought into contact with the molten fluororesin, but the treatment is usually 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 preferably carried out by contacting a non-fluorination-treated fluororesin with fluorine gas (F2 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 desirably has a melting point of 200°C or higher, a molding temperature of 250°C or higher, and a thermal decomposition temperature of 300°C or higher. 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 the temperature measured by a differential scanning calorimeter (DSC), the molding temperature is a temperature generally recommended 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 a resin loses 1% weight when heated in air at 10°C / min using TG (thermal weight change measurement). However, this does not include weight loss due to the evaporation of contained water and water of crystallization between 100°C and 200°C. Having fluidity means that the MFR is 0.0001 or higher at that temperature.

[0048] 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 other than the fluororesin (A). Examples of resins other than 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 of two or more.

[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. There is no particular lower limit, and it 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 skeleton: 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 foam molding resin composition of the present disclosure when the composition 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 tetrapyrrole cyclic compound (B) preferably has a crystallite size of greater than 100 Å, more preferably greater than 140 Å, and even more preferably greater than 200 Å, as measured by X-ray diffraction (XRD). This allows for the formation of an ideal crystal lattice with minimal distortion, promoting bubble formation. 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. For XRD, an X-ray diffractometer, Smart Lab, manufactured by Rigaku Corporation, is used, and powder measurements are performed using measurement and analysis software, Smart Lab Studio II. CuKα with a wavelength of 1.54 Å is used as the X-ray source, and the diffraction angle (2θ) is set to 5° to 90°. The crystallite size is calculated using the Scherrer formula from the maximum half-width of the obtained diffraction peak. D=K×λ / (β×cosθ) Scherrer's formula D: Crystallite size (Å) K: Scherrer constant λ: X-ray wavelength (Å) β: Half-width of diffraction peak (rad) θ: 1 / 2 of the diffraction angle (rad) The Scherrer constant (K) is 0.94, and the X-ray wavelength (λ) is 1.5418. If the obtained diffraction spectrum does not contain diffraction peaks attributable to a crystalline structure, it is determined that the material does not 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, and enables long-term molding, such as wire molding. The lower limit is not particularly limited, and may be 0% by mass. The amount of volatilization is calculated by measuring the mass loss when the sample is held at 330°C for 1 hour in an electric furnace, and then dividing the mass before holding by 100.

[0058] To form more uniform bubbles, the tetrapyrrole cyclic compound (B) is preferably dispersed in the fluororesin (A) with a center-to-center distance of 5.0 μm or less. The upper limit of the center-to-center 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 or less, 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 more 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-to-center 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 150x magnification and processing the image. The center-to-center distance and particle size are the average values ​​of 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 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. This can prevent 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). The upper limit is not particularly limited, but is preferably 1000°C or lower.

[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 at least 0.1 part by mass, more preferably at least 0.3 part by mass, even more preferably at least 0.5 part by mass, and is preferably at most 20 parts by mass, more preferably at most 5.0 parts by mass, even more preferably at most 2.0 parts by mass, 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, while if it 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 may 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, as long as the effects of the present disclosure are not impaired. Polyatomic anion-containing inorganic salts include those disclosed in US Pat. No. 4,764,538.

[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 of two or more. 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. The phrase "substantially free of fluorine-based low molecular weight compounds" means that the content of fluorine-based low molecular weight compounds is 10 mass ppm 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 include perfluoroalkyl acids and perfluorosulfonic acids, and more specific examples include C8F 17 COOH and its salts, C7F 15 COOH and its salts, CF 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, CF 13 CH2CH2OH, and more specifically, {F(CF2)6CH2CH2SO3}2Ba.

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

[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 5 to 70 g / 10 min, even more preferably 10 to 60 g / 10 min, and 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, since this can suppress the generation of sparks and increase the foaming rate. The MFR is a value measured in accordance with ASTM D-1238 using a die having a diameter of 2.1 mm and a length of 8 mm, under a load of 5 kg and at 372°C.

[0075] 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] The method for producing a foam-molded article of the present disclosure includes a step of foam-molding the resin composition for foam molding 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 foam electric wires, a filament-like shape for wires, a sheet-like shape, a film-like shape, a rod-like shape, a pipe-like shape, etc. The foam molded article can be used as, for example, an electrical insulating material, a heat insulating material, a sound insulating material, a lightweight structural material such as a floating material, a shock absorbing material such as a cushion, etc. Furthermore, the foam molded article can be particularly suitably used as a covering material for foam electric wires. The resulting foam-molded article contains a molten solidified product of the foam-molding resin composition of the present disclosure and bubbles, and the bubbles are preferably uniformly distributed throughout the molten solidified product. The bubble size is not limited, but is preferably 60 μm or less, more preferably 30 μm or less. The bubble size is preferably 0.1 μm or more. The foaming rate of the foamed molded article is preferably 20% or more, although not particularly limited thereto, and the upper limit of the foaming rate 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, which have the advantages of strong resilience against external pressure, excellent rigidity, shock absorption, and processability, and also of preventing moisture and other contaminants from penetrating the interior. The closed cells can be formed by the above-mentioned hot melt molding method as well as by a 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 is particularly suitable for use 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] The conductor (core wire) may be made of a metal conductive material such as copper or aluminum, or carbon, etc. The conductor may be made of a single material, or may have its surface 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 thereof include a flat shape and rectangular wire.

[0091] Specific examples of conductors (core wires) 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 made of seven copper wires with a diameter of 51 micrometers twisted together for a total diameter of 153 micrometers), AWG-30 (solid copper wire with a diameter of 254 micrometers, a wire made of seven copper wires with a diameter of 102 micrometers twisted together for a total diameter of 306 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 was measured using a Keyence laser microscope (VK-X1000), and the image data obtained was corrected by specifying the area of ​​the wire using quadratic curve correction, a surface shape correction tool. The surface roughness was then calculated over a 500 x 2000 μm area.

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

[0095] The foamed electric wire of the present disclosure can be used as cables connecting computers and their peripheral devices, cables for transmitting high-capacity video and audio at high speeds, cables for connecting servers in data centers, 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 equipment, electric wires for information equipment (optical fiber cables, audio cables, etc.), internal wiring for communication base stations, internal wiring for high-current devices (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 and 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 covered on the outer layer, or even a three-layer structure (skin-foam-skin) in which a non-foamed layer is covered on the outer layer of skin-foam. 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. [Example]

[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 produce 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 fluorinated sufficiently to the point where no substantial difference was observed in the spectrum), and the absorbance of each peak was read and calculated based on the carbon number (1 × 10) according to the following formula: 6 The number of unstable terminal groups per unit was calculated. Carbon number 1 x 10 6 Number of unstable terminal groups per unit = (I × K) / t (I: absorbance, K: correction factor, t: film thickness (unit: mm)) The correction coefficient (K) for each unstable terminal group is as follows: -COF(1884cm -1 )···405 -COOH(1813cm -1 , 1775cm -1 )···455 -COOCH3(1795cm -1 )···355 -CONH2(3438cm -1 )···480 -CH2OH(3648cm -1 )···2325

[0100] (Measurement of the number of -CF2H 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 fluororesin (A) + 20°C. 19 F-NMR measurement was performed, and the integral value of the peak due to the presence of -CF2H groups and the integral values ​​of other peaks were calculated.

[0101] (SSG) Measurement was performed 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 using a DSC (RDC220 manufactured by Seiko Denshi Co., Ltd.) at a temperature rise rate of 10°C / min.

[0103] (pyrolysis temperature) The 1% weight loss temperature was measured by TG when heated in air at 10°C / min.

[0104] (MFR) The values ​​were 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] (Production of FEP pellets) Fluorinated FEP pellets were prepared in the same manner as in Example 1 of JP 2017-128119 A. The resulting 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 a total number of unstable terminal groups and -CFH terminal groups of 1 x 10 carbon atoms. 6 There were 0 per piece.

[0107] (Production of premix pellets for wire molding (Process 1)) Masterbatch pellets were prepared by kneading FEP pellets (MFR: 38 g / 10 min) and additives in a twin-screw extruder with the cylinder and die temperatures set to those shown in Table 1. 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] [Table 1]

[0109] (Foamed wire molding evaluation (process 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 Co., Ltd., and a crosshead manufactured by Unitec Co., Ltd. The configuration and conditions of the extruder are shown in Table 2, and the extruder temperature is shown in Table 3. 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 fed and extrusion-foam-molded. A core wire with a diameter of 0.30 mm was covered with a foam-molded product to give an outer diameter of 0.80 mm and a capacitance of 86 pf / m, yielding a foam-molded 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 electrostatic capacitance was measured using a CAPAC300 19C (manufactured by Zumbach).

[0110] [Table 2]

[0111] [Table 3]

[0112] (bubble size) SEM images of the cross section of the foamed electric wire were 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] (Foaming rate) The density was calculated as follows: (specific gravity of fluororesin - specific gravity of foam 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 check for 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 snag (protrusion) felt when the surface of the foamed electric wire was checked by touch was evaluated according to the following criteria. Very good: No snagging Good: Little snagging Slightly poor: There is some catching Defective: Many snags

[0117] (Surface roughness) The surface of the foamed electric wire was measured using a Keyence laser microscope (VK-X1000). The image data obtained was corrected by specifying the area of ​​the electric wire using quadratic curve correction, and the surface roughness of an area of ​​500 × 2000 μm was then 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] (Fluorine-based low molecular weight compound content) The sample was crushed by freeze-pulverization, the resulting powder was dispersed in methanol, and extracted by 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 recorded as the value.

[0120] (Dielectric constant, dielectric loss tangent) Premix pellets (resin composition before foam molding) with the desired additive concentration were measured by the 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 as a solid.

[0122] Example 1 In step 1, pellets were produced 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, and 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. 4Analysis of the obtained foamed electric wire revealed that the foaming rate was 43%, the bubble size was 21 μm, and the surface condition was also very good to the touch, with a surface roughness of 6.8 μm, which was also very good. Furthermore, at the molding temperature during foam molding, the copper phthalocyanine did not decompose and was insoluble and not melted 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.No fluorine-based low molecular weight compounds were detected in the comparative examples described below either. Furthermore, the SEM images taken when calculating the bubble size confirmed that closed bubbles were formed. 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 the additive. No smoke or eye discharge was observed during molding, but the wire surface condition was poor and there were more than 300 sparks 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 using the same method as in Example 1, except that Irgaclear XT386 (a transparent nucleating agent for polypropylene 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 the additive. No smoke or eye discharge was observed during molding, but the wire surface condition was somewhat poor and there were more than 100 sparks per 10 4Analysis of the obtained foamed electric wire revealed that the bubble size was good at 27 μm, but the surface roughness was poor at 10.1 μm.

[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. 4 However, analysis of the foamed electric wires revealed that the size of the bubbles was very large, at 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 wire surface condition was poor and there were more than 100 sparks per 10 4 Analysis of the obtained foamed electric wire revealed that the bubble size was good at 30 μm, but the surface roughness was very poor at 12.3 μm.

[0128] [Table 4]

Claims

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

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

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

5. 3. The resin composition for foam molding according to claim 1, wherein the fluororesin (A) has been fluorinated.

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

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

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

9. 3. The resin composition for foam molding according to claim 1, wherein the tetrapyrrole cyclic compound (B) has a phthalocyanine skeleton.

10. 3. The resin composition for foam molding according to claim 1, wherein the tetrapyrrole cyclic compound (B) is a metal phthalocyanine.

11. 3. The resin composition for foam molding according to claim 1, wherein the tetrapyrrole cyclic compound (B) is copper phthalocyanine.

12. 3. The resin composition for foam molding according to claim 1, 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. 3. The resin composition for foam molding according to claim 1, 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 foam-molded article formed using the foam-molding resin composition according to claim 1 or 2.

15. A method for producing a foam-molded article, comprising a step of foam-molding the resin composition for foam molding according to claim 1 or 2.

16. A foamed electric wire comprising a conductor and a foamed insulating layer formed on the conductor using the foam molding resin composition according to claim 1 or 2.

17. 3. 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 claim 1.

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