Resin composition for foam molding, foam molded article, and method for producing foam molded article

Abstract

To provide a resin composition for foam molding, a foam molded body, and a method for producing a foam molded body, enabling formation of good bubbles without the need for a special fluororesin.SOLUTION: A resin composition for foam molding, comprising a fluororesin (A) and a compound (B) having a crystallite size greater than 100 Å as measured by X-ray diffraction and a volatilization amount of 7.0 mass% or less at 330°C, the compound (B) being dispersed in the fluororesin (A) with an inter-centroid distance of 5 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition for foam molding, a foam molded article, and a method for producing a foam molded article. [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. For example, Patent Document 1 describes that good bubbles are formed by melt-foam molding a specific thermoplastic fluororesin material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-004057 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 leaves room for improvement in that the types of fluororesin that can be used are limited.

[0006] An object of the present disclosure is to provide a resin composition for foam molding that can form good cells even without using a special fluororesin, a foam molded article, and a method for producing a foam molded article. [Means for solving the problem]

[0007] The present disclosure (1) is a resin composition for foam molding, comprising a fluororesin (A) and a compound (B) having a crystallite size of more than 100 Å as measured by X-ray diffraction and a volatilization amount of 7.0 mass% or less at 330°C, wherein the compound (B) is dispersed in the fluororesin (A) at a center-of-gravity distance of 5.0 μm or less.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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 %.

[0013] 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.

[0014] 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.

[0015] The present disclosure (9) is the resin composition for foam molding according to any one of the present disclosures (1) to (8), wherein the compound (B) has a crystallite size of 200 to 1000 Å as measured by X-ray diffraction, and an amount of volatilization at 330°C of 1.0 mass% or less.

[0016] The present disclosure (10) is the resin composition for foam molding according to any one of the present disclosures (1) to (9), wherein the compound (B) is dispersed in the fluororesin (A) at a center-of-gravity distance of 0.5 to 2.0 μm.

[0017] The present disclosure (11) is directed to a method for manufacturing a fluororesin (A) containing the compound (B) at a density of 15,000 particles / mm 2 The resin composition for foam molding according to any one of the present disclosures (1) to (10) is dispersed as described above.

[0018] The present disclosure (12) is the resin composition for foam molding according to any one of the present disclosures (1) to (11), wherein the compound (B) is dispersed in the fluororesin (A) with a particle size of 4.0 μm or less.

[0019] The present disclosure (13) is the resin composition for foam molding according to any one of the present disclosures (1) to (12), wherein the compound (B) has a thermal decomposition temperature of 270° C. or higher.

[0020] The present disclosure (14) is the resin composition for foam molding according to any one of the present disclosures (1) to (13), wherein the compound (B) includes at least one selected from the group consisting of a tetrapyrrole cyclic compound, barium sulfate, silicon dioxide, and aluminum oxide.

[0021] The present disclosure (15) is the resin composition for foam molding according to any one of the present disclosures (1) to (14), wherein the compound (B) contains copper phthalocyanine.

[0022] The present disclosure (16) is the resin composition for foam molding according to any one of the present disclosures (1) to (15), wherein the content of the compound (B) is 0.1 to 20 parts by mass per 100 parts by mass of the fluororesin (A).

[0023] The present disclosure (17) is the resin composition for foam molding according to any one of the present disclosures (1) to (16), wherein the content of the compound (B) is 0.5 to 2.0 parts by mass per 100 parts by mass of the fluororesin (A).

[0024] The present disclosure (18) is a foam-molded article formed using the resin composition for foam molding according to any one of the present disclosures (1) to (17).

[0025] The present disclosure (19) 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 (17).

[0026] The present disclosure (20) is the method for producing a foam molded article according to the present disclosure (19), wherein the foam molding is batch foam molding. [Effects of the Invention]

[0027] According to the present disclosure, it is possible to provide a resin composition for foam molding that can form good cells even without using a special fluororesin, a foam molded article, and a method for producing a foam molded article. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present disclosure will be specifically described below.

[0029] The resin composition for foam molding of the present disclosure contains a fluororesin (A) and a compound (B) having a crystallite size of more than 100 Å as measured by X-ray diffraction and a volatilization amount of 7.0 mass% or less at 330°C, and the compound (B) is dispersed in the fluororesin (A) with a center-of-gravity distance of 5.0 μm or less.

[0030] In the resin composition for foam molding of the present disclosure, compound (B) that satisfies the above-mentioned conditions functions as a foam nucleating agent. By ensuring that the crystallite size is greater than 100 Å and the center-of-gravity distance is 5.0 μm or less, the bubble size in the foamed article is reduced, thereby increasing the number of bubbles generated. Furthermore, by ensuring that the volatilization amount at 330°C is 7.0 mass% or less, bubble coalescence can be suppressed.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The TFE / PAVE copolymer preferably has a TFE / PAVE mass ratio of 90-99 / 1-10, more preferably 92-97 / 3-8.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] 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 are measured by a cavity resonator method at a frequency of 6 GHz.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The resin composition for foam molding of the present disclosure contains compound (B) as a foam nucleating agent.

[0054] The crystallite size of compound (B) measured by X-ray diffraction (XRD) should be greater than 100 Å, preferably greater than 140 Å, and more preferably greater than 200 Å. 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.

[0055] The compound (B) may have a volatilization amount of 7.0% by mass or less at 330°C, preferably 5.0% by mass or less, 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.

[0056] The compound (B) may be dispersed in the fluororesin (A) with a distance between centers of gravity of 5.0 μm or less, but the upper limit of the distance between centers of gravity is preferably 3.0 μm or less, 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.

[0057] From the viewpoint of forming more uniform bubbles, the 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 2or less, more preferably 1,000,000 pieces / mm 2 The following is the result.

[0058] From the viewpoint of forming more uniform bubbles, it is preferable that the compound (B) be 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.

[0059] The dispersion state (center-of-gravity distance, density, particle size) of compound (B) in fluororesin (A) is calculated by photographing a cross section of a resin composition containing fluororesin (A) and compound (B) with a laser microscope (Keyence Corporation's shape analysis laser microscope (VK-X1000)) at 150x magnification and processing the image. The center-of-gravity distance and particle size are the average values ​​of 100 particles.

[0060] The compound (B) is not particularly limited as long as it satisfies the above-mentioned conditions, and may include a tetrapyrrole cyclic compound, barium sulfate, silicon dioxide, aluminum oxide, etc. These may be used alone or in combination of two or more. Among these, it is preferable to include at least one selected from the group consisting of a tetrapyrrole cyclic compound, barium sulfate, silicon dioxide, and aluminum oxide, and it is more preferable to include a tetrapyrrole cyclic compound. However, the type of component is not important; what is important is that the above conditions are met, and the same component will not produce the same effect if its crystalline state, dispersion state, and volatilization amount are different. Regarding the crystalline state, it is important that the crystallite size is larger than 100 Å as measured by X-ray diffraction (XRD), regarding the dispersion state, it is important that the component is dispersed in the fluororesin (A) with a distance between centers of gravity of 5.0 μm or less, and regarding the volatilization amount, it is important that the volatilization amount at 330°C is 7.0 mass% or less.

[0061] Tetrapyrrole cyclic compounds 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.

[0062] In view of their excellent function as foam nucleating agents, the tetrapyrrole cyclic compounds are preferably those having a phthalocyanine skeleton, more preferably metal phthalocyanines, and even more preferably copper phthalocyanines.

[0063] It is preferable that the 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 compound (B) is solid in the foam molding resin composition of the present disclosure when the composition is foam molded. This allows the compound (B) to fully function as a foam nucleating agent. Whether compound (B) satisfies this condition can be confirmed by observing, using a polarizing microscope equipped with a hot stage, whether compound (B) remains solid when heated to a predetermined temperature.

[0064] The melting temperature (melting point) of 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 (B) 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.

[0065] The thermal decomposition temperature of 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, compound (B) is less likely to decompose even at the molding temperature during foam molding. Therefore, adverse effects due to the decomposition of compound (B) (e.g., deterioration of electrical properties, bursting of cells, and breakage of coating during wire molding) can be suppressed. The upper limit is not particularly limited, but 1000°C or lower is preferred.

[0066] The melting temperature (melting point) and thermal decomposition temperature of the compound (B) can be measured by the same method as that for the fluororesin (A) described above.

[0067] In the resin composition for foam molding of the present disclosure, the content of 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 fluororesin (A). If the content of compound (B) is too low, the effect of adding compound (B) may not be fully obtained, and if it is too high, the production cost may increase.

[0068] The resin composition for foam molding of the present disclosure may contain a foam nucleating agent other than compound (B). The foam nucleating agent other than compound (B) is not particularly limited as long as it does not satisfy the above-mentioned conditions, and examples thereof 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] The method for producing a foam-molded article of the present disclosure includes a step of foam-molding (preferably batch 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.

[0080] Until now, no foam nucleating agent capable of forming fine bubbles has been commonly used in batch foam molding of fluororesin, which requires molding at high temperatures. The resin composition for foam molding of the present disclosure can form fine bubbles even in batch foam molding of fluororesin.

[0081] 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. Examples include a method in which the resin composition for foam molding of the present disclosure is charged into a screw extruder designed for foaming operations and a continuous gas extrusion method is used, or a batch foaming method in which a preformed resin composition for foam molding of the present disclosure is charged into a pressure-resistant container, heated to a predetermined temperature equal to or higher than the melting point, sufficiently impregnated with gas, and then rapidly reduced in pressure by releasing the pressure.

[0082] The gas used in the gas extrusion method and the batch foaming method can be, for example, chlorodifluoromethane, nitrogen, carbon dioxide, or a mixture of these gases. The gas may be introduced as a pressurized gas into the molten resin in the extruder or into a pressure-resistant vessel, or may be generated by mixing a chemical foaming agent into the molten resin or a preformed resin composition for foam molding. The introduced gas dissolves in the molten resin in the extruder and in the resin in the pressure vessel.

[0083] The gas dissolved in the resin escapes from the melt when the pressure of the melt suddenly drops as it exits the extrusion die, or when the pressure in the pressure vessel is released and the pressure is rapidly reduced. The extrudate extruded from the extruder is then cooled and solidified, for example, by immersing it in water. In the batch foaming method, the resin is also cooled and solidified by cooling the pressure vessel.

[0084] The foamed 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, and can also be used as an insulating layer with stable dimensions such as thickness.

[0085] 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.

[0086] 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, mold foam molding, and batch foam molding.

[0087] 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.

[0088] 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 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.

[0089] 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.

[0090] 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]

[0091] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0092] 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 the carbon number (1 × 10) was calculated 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

[0093] (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.

[0094] (SSG) Measurement was performed based on the immersion method in accordance with ASTM D4895-89.

[0095] (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.

[0096] (pyrolysis temperature) The 1% weight loss temperature was measured by TG when heated in air at 10°C / min.

[0097] (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.

[0098] The examples and comparative examples were carried out in the following manner.

[0099] (Production of FEP pellets) Fluorinated FEP pellets were prepared in the same manner as in Example 2 of JP-A 2011-514407. The resulting pellets (TFE / HFP / PPVE copolymer) had a mass ratio of TFE / HFP / PPVE = 87.8 / 11.2 / 1.0, a melting point of 255°C, an MFR of 23 g / 10 min, and a total number of unstable terminal groups and -CFH terminal groups of 1 x 10 carbon atoms. 6 There were three per piece.

[0100] (Preparation of pellets for batch foaming test (Step 1)) Additives were mixed with FEP pellets (MFR: 38g / 10min) to achieve the desired concentration, and the mixture was kneaded in a Labo Plastomill at 300°C for 10 minutes to produce a compound. The recovered compound was cut and extruded at 300°C under a 5kg load using an MFR measuring device, and the extruded strands were cut into 2-3mm pieces to produce pellets. The cross section of the prepared pellets was photographed at 150x magnification using a laser microscope (Keyence Corporation, Shape Analysis Laser Microscope (VK-X1000)), and the distance between the centers of gravity of the nucleating agent particles, particle density, and particle diameter were calculated by image processing. The distance between the centers of gravity and particle diameter were calculated as the average value of 100 particles.

[0101] (Batch foaming test (process 2)) Preheat the container to 270℃ in an electric furnace until the internal volume is approximately 11cm. 3 0.4g of pellets wrapped in aluminum foil were placed in the pressure vessel and returned to the electric furnace. Up to three samples were placed in one test at the same time. The vessel was pressurized to 3MPa with nitrogen gas, held for 60 minutes, and then rapidly depressurized to atmospheric pressure within one second to foam the resin. The resulting foamed molded product maintained its pellet shape. It was not in an unfoamed state (a state in which only cracks had occurred). SEM images of the cross section of the foamed molded article were taken, and the number of bubbles per unit area was calculated by image processing. The bubble number index per unit area was calculated by multiplying this number by the number of bubbles generated when the same treatment was performed on a resin without additives. The average area per unit bubble was calculated, and the average bubble area index was calculated by multiplying this number by the area of ​​bubbles generated when the same treatment was performed on a resin without additives.

[0102] (crystallite size) The powder was measured using an X-ray diffractometer (Smart Lab, manufactured by Rigaku Corporation) and measurement and analysis software (Smart Lab Studio II). CuKα with a wavelength of 1.54 Å was used as the X-ray source, and the diffraction angle (2θ) was set to 5° to 90°. The crystallite size was calculated from the maximum half-width of the obtained diffraction peak using the Scherrer formula. 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) was 0.94 and the X-ray wavelength (λ) was 1.5418. If the obtained diffraction spectrum did not have a diffraction peak attributable to the crystalline structure, it was determined that the sample did not have a crystalline structure, and the crystallite size was determined to have no peak.

[0103] (Volatility test) The mass loss when the sample (additive) was held in an electric furnace at 330°C for 1 hour was measured, and the amount of volatilization was calculated by dividing the mass before holding by 100.

[0104] (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.

[0105] (Dielectric constant, dielectric loss tangent) Pellets for a batch foaming test (resin composition before foaming) having a target additive concentration were measured by a cavity resonator method at a frequency of 6 GHz.

[0106] (State of 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 compound (B) remained solid or not.

[0107] 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, crystallite size: 103 Å, amount of volatilization in volatility test: 0.4% by mass) to 100 parts by mass of FEP pellets, and in step 2, a foamed molded product was obtained. The distance between the centers of gravity of the additive particles dispersed in the pellets prepared in step 1 was 1.6 μm. The bubble count index per unit area in the batch foaming test in step 2 was a good 21. Furthermore, no fluorine-based low molecular weight compounds were detected in the pellets used or in the foamed molded articles produced.No fluorine-based low molecular weight compounds were detected in the following examples and comparative examples either. Furthermore, at the molding temperature during foam molding, the copper phthalocyanine did not decompose and was insoluble and not melted in FEP. Furthermore, SEM images of the cross sections of the foamed molded articles confirmed the formation of closed cells. Closed cells were also formed in the following examples and comparative examples.

[0108] Example 2 A foamed molded article was obtained in the same manner as in Example 1, except that Shirasu balloons (SSW-40 manufactured by Zanwards Corporation, main components: silicon dioxide and aluminum oxide, melting point: no peak detected below 350°C, thermal decomposition temperature: 600°C or higher, crystallite size: 672 Å, amount of volatilization in volatility test: 0.0%) were used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 2.9 μm. The bubble number index per unit area in the batch foaming test in step 2 was a good 13. Furthermore, at the molding temperature during foam molding, the Shirasu balloon did not decompose, was insoluble in FEP, and did not melt.

[0109] Example 3 A foamed molded article was obtained in the same manner as in Example 1, except that precipitated barium sulfate (P-30 manufactured by Takehara Chemical Industry Co., Ltd., melting point: no peak detected below 350°C, thermal decomposition temperature: 600°C or higher, crystallite size: 309 Å, volatilization amount in volatility test: 0.0%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 2.8 μm. The bubble number index per unit area in the batch foaming test in step 2 was a good 13. Furthermore, at the molding temperature during foam molding, the precipitated barium sulfate did not decompose and was insoluble and not melted in FEP.

[0110] Example 4 A foamed molded article was obtained in the same manner as in Example 1, except that pearlite powder (W-6 manufactured by Takehara Chemical Industry Co., Ltd., main component: barium sulfate, melting point: no peak detected below 350°C, thermal decomposition temperature: 600°C or higher, crystallite size: 153 Å, amount of volatilization in volatility test: 0.0%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 2.9 μm. The bubble number index per unit area in the batch foaming test in step 2 was a good 12. Furthermore, at the molding temperature during foam molding, the pearlite powder did not decompose and was insoluble in and did not melt in the FEP.

[0111] Comparative Example 1 A foamed molded article was obtained in the same manner as in Example 1, except that boron nitride (MGP manufactured by Denka Co., Ltd., crystallite size: 158 Å, volatilization amount in volatility test: 0.0%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 5.9 μm. The bubble number index per unit area in the batch foaming test in step 2 was a small 7.3.

[0112] Comparative Example 2 A foamed molded article was obtained in the same manner as in Example 1, except that sodium benzoate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., crystallite size: 131 Å, volatilization amount in volatility test: 0.0%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 6.2 μm. The bubble number index per unit area in the batch foaming test was a small 5.4.

[0113] Comparative Example 3 A foamed molded article was obtained in the same manner as in Example 1, except that Pigment Red 254 (manufactured by Tokyo Chemical Industry Co., Ltd., crystallite size: 89 Å, volatilization amount in volatility test: 0.4%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 2.2 μm. The bubble number index per unit area in the batch foaming test in step 2 was a small 3.1.

[0114] Comparative Example 4 A foamed molded article was obtained in the same manner as in Example 1, except that talc (PAOG-2 manufactured by Tokyo Chemical Industry Co., Ltd., crystallite size: 37 Å, volatilization amount in volatility test: 0.0%) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 5.1 μm. The bubble number index per unit area in the batch foaming test in step 2 was a small 4.6.

[0115] Comparative Example 5 A foamed molded article was obtained in the same manner as in Example 1, except that a rosin metal salt (Plafit H510H manufactured by Arakawa Chemical Industries, Ltd., no peak was observed by XRD, and the amount of volatilization in the volatility test was 10.6% by mass) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 4.2 μm. The bubble count index per unit area in the batch foaming test in step 2 was a small 0.4.

[0116] Comparative Example 6 A foamed molded article was obtained in the same manner as in Example 1, except that a condensed phosphate ester (SR-3000 manufactured by Daihachi Chemical Industry Co., Ltd., no peak was observed by XRD, and the amount of volatilization in the volatility test was 8.1% by mass) was used as the additive. The distance between the centers of gravity of the additive particles dispersed in the pellets produced in step 1 was 4.1 μm. The bubble count index per unit area in the batch foaming test in step 2 was a small 0.2.

[0117] Comparative Example 7 Except for not using any additives, a foamed molded article was obtained in the same manner as in Example 1. In a batch foaming test using this foamed molded article, the bubble number index per unit area was set to 1.0 and the average bubble area index was set to 1.00.

[0118] [Table 1]

Claims

1. The present invention relates to a composition comprising a fluororesin (A) and a compound (B) having a crystallite size of more than 100 Å as measured by an X-ray diffraction method and a volatilization amount of 7.0% by mass or less at 330°C, The resin composition for foam molding comprises the fluororesin (A) and the compound (B) dispersed therein with a distance between centers of gravity of 0.01 to 5.0 μm.

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 compound (B) has a crystallite size of 200 to 1000 Å as determined by X-ray diffraction and a volatilization amount at 330° C. of 1.0 mass % or less.

10. 3. The resin composition for foam molding according to claim 1, wherein the compound (B) is dispersed in the fluororesin (A) with a distance between centers of gravity of 0.5 to 2.0 μm.

11. The compound (B) is contained in the fluororesin (A) at a density of 15,000 particles / mm ２ The resin composition for foam molding according to claim 1 or 2, which is dispersed as described above.

12. 3. The resin composition for foam molding according to claim 1, wherein the compound (B) is dispersed in the fluororesin (A) with particles having a diameter of 0.001 to 4.0 μm.

13. 3. The resin composition for foam molding according to claim 1, wherein the compound (B) has a thermal decomposition temperature of 270° C. or higher.

14. 3. The resin composition for foam molding according to claim 1, wherein the compound (B) comprises at least one selected from the group consisting of a tetrapyrrole-based cyclic compound, barium sulfate, silicon dioxide, and aluminum oxide.

15. 3. The resin composition for foam molding according to claim 1, wherein the compound (B) comprises copper phthalocyanine.

16. 3. The resin composition for foam molding according to claim 1, wherein the content of the compound (B) is 0.1 to 20 parts by mass per 100 parts by mass of the fluororesin (A).

17. 3. The resin composition for foam molding according to claim 1, wherein the content of the compound (B) is 0.5 to 2.0 parts by mass per 100 parts by mass of the fluororesin (A).

18. A foam-molded article formed using the foam-molding resin composition according to claim 1 or 2.

19. 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.

20. The method for producing a foamed molded article according to claim 19, wherein the foaming is batch foaming.

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