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

Abstract

The purpose of the present disclosure is to provide a resin composition for foam molding, a foam molded body, and a method for producing a foam molded body, the resin composition for foam molding being capable of forming good air bubbles even if not a special fluororesin. The present disclosure is a resin composition for foam molding, which contains a fluororesin (A) and a compound (B) of which the crystallite size in an X-ray diffraction method is greater than 100 Å and the volatilization amount at 330°C is 7.0 mass % or less, the compound (B) being dispersed in the fluororesin (A) at a center-to-center distance of 5 μm or less.

Description

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

[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.

[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 fluororesins and improving their electrical properties. For example, Patent Document 1 describes that good bubbles are formed by melt-foam molding a specific thermoplastic fluororesin material.

[0004] JP 2015-004057 A

[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.

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

[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), in which 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 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 (1) to (10) of the present disclosure 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), in which 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 foam-molding resin composition 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.

[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.

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

[0029] The resin composition for foam molding of the present disclosure comprises 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.

[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 having a crystallite size of more than 100 Å and a center-of-gravity distance of 5.0 μm or less, the bubble size in the foam molded article is reduced, thereby increasing the number of bubbles generated. Furthermore, by having a volatilization amount of 7.0 mass% or less at 330°C, bubble coalescence can be suppressed.

[0031] Fluorine resin (A) can be any resin containing fluorine, but preferably be melt-moldable fluororesin.As melt-moldable fluororesin, for example, tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) (PAVE) copolymer [PFA], TFE / ethylene copolymer [ETFE], chlorotrifluoroethylene (CTFE) / ethylene copolymer [ECTFE], polyvinylidene fluoride [PVdF], polychlorotrifluoroethylene [PCTFE], TFE / vinylidene fluoride (VdF) copolymer [VT], polyvinyl fluoride [PVF], TFE / VdF / CTFE copolymer [VTC], TFE / ethylene / HFP copolymer, TFE / HFP / VdF copolymer etc. can be used alone or in combination.

[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 of two or more.

[0033] The fluororesin (A) may have polymerization units based on other monomers in an amount that does not impair the essential properties of each fluororesin. The other monomers can be appropriately selected from, for example, TFE, HFP, ethylene, propylene, perfluoro(alkyl vinyl ether), perfluoroalkylethylene, hydrofluoroolefin, fluoroalkylethylene, perfluoro(alkyl allyl ether), etc. One or more of these can be used. The perfluoroalkyl group constituting the other monomer preferably has 1 to 10 carbon atoms.

[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 thereof include fluorine-containing monomers having an acid anhydride residue such as 3-dicarboxylic acid anhydride (hereinafter also referred to as "NAH"), succinic anhydride, fumaric anhydride, maleic anhydride, etc.; fluorine-containing monomers having a sulfo group such as vinyl sulfonic acid; fluorine-containing monomers having an epoxy group (glycidyl group) such as glycidyl vinyl ether, glycidyl allyl ether, etc.; fluorine-containing monomers having an amino group such as aminoalkyl vinyl ether, aminoalkyl allyl ether, etc.; fluorine-containing monomers having an amide group such as (meth)acrylamide, methylolacrylamide, etc.; and fluorine-containing monomers having a nitrile group such as acrylonitrile, methacrylonitrile, etc.

[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, because of its excellent heat resistance. Also, a perfluororesin is preferred because of its superior electrical properties.

[0036] The TFE / HFP copolymer preferably has a TFE / HFP mass ratio of 80 to 97 / 3 to 20, more preferably 84 to 92 / 8 to 16. The TFE / HFP copolymer may be a binary copolymer of TFE and HFP, or may be a ternary copolymer (e.g., a TFE / HFP / PAVE copolymer) composed of a comonomer copolymerizable with TFE and HFP. The TFE / HFP copolymer is also preferably a TFE / HFP / PAVE copolymer containing polymerized units based on PAVE. The TFE / HFP / PAVE copolymer preferably has a TFE / HFP / PAVE mass ratio of 70 to 97 / 3 to 20 / 0.1 to 10, more preferably 81 to 92 / 5 to 16 / 0.3 to 5.

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

[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. Since this can suppress spark generation and increase the foaming rate, it is even more preferably 15 to 50 g / 10 min, even more preferably 20 to 45 g / 10 min, and particularly preferably 30 to 45 g / 10 min. The above MFR is a value measured in accordance with ASTM D-1238 using a die with a diameter of 2.1 mm and a length of 8 mm at 372°C and a load of 5 kg.

[0040] The fluororesin (A) may contain a fluororesin that is not melt-moldable in addition to a melt-moldable fluororesin. When the fluororesin (A) contains a fluororesin that is not melt-moldable, the content thereof is preferably 0.001 to 3.0 mass% based on the total amount of the fluororesin (A). In this specification, "not melt-moldable" means that the MFR is less than 1 g / 10 min. The MFR is preferably 0.1 g / 10 min or less.

[0041] Examples of fluororesins that cannot be melt-molded include polytetrafluoroethylene (PTFE). Also, FEP, PFA, ETFE, PCTFE, PVDF, and the like, which are exemplified as melt-moldable fluororesins, can also be used. One or more of these can be used. Of these, PTFE is preferred. FEP and the like are considered to be non-melt-moldable fluororesins when their MFR is less than 1 g / 10 min, but are considered to be melt-moldable fluororesins when their MFR is 1 g / 10 min or more.

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

[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 impractical. The SSG is a value measured using the underwater displacement method in accordance with ASTM D4895-89. When the SSG of PTFE is low, the effect of increasing the biaxial elongational viscosity can be exerted with a small amount of addition. When the SSG is high, the above effect can be exerted by increasing the amount of addition.

[0044] PTFE can be prepared by known methods such as emulsion polymerization and suspension polymerization, with emulsion polymerization being preferred. If PTFE aggregates are present in the resin composition for foam molding of the present disclosure, sparkouts may occur frequently during wire coating molding, potentially increasing the reject rate. Therefore, the average primary particle diameter of PTFE is preferably 50 to 800 nm, more preferably 50 to 500 nm. The average primary particle diameter of PTFE was determined by measuring the transmittance of projected light at a wavelength of 500 nm per unit length for a polymer latex diluted with water to a solids content of 0.22% by mass, and then measuring the unidirectional diameter in a transmission electron microscope photograph. Based on this calibration curve of the transmittance and the number-average primary particle diameter of PTFE.

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

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

[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 is desirable that the melting point be 200°C or higher, the molding temperature be 250°C or higher, and the thermal decomposition temperature be 300°C or higher. Furthermore, the melting point is more preferably 250°C or higher, and preferably 320°C or lower. The molding temperature is more preferably 300°C or higher, and preferably 450°C or lower. The thermal decomposition temperature is more preferably 350°C or higher, and even more preferably 400°C or higher. The upper limits of the melting point, molding temperature, and thermal decomposition temperature are 600°C or lower. In this specification, the melting point is a temperature measured by a differential scanning calorimeter (DSC), the molding temperature is a temperature that is generally recommended and suitable for molding, at which the resin has fluidity and does not undergo resin degradation such as discoloration, and the thermal decomposition temperature is the temperature at which 1% weight loss occurs when heated in air at 10°C / min using TG (thermal weight change measurement). However, this does not include the weight loss due to the evaporation of contained water and water of crystallization observed between 100° C. and 200° C. Having fluidity means that the MFR is 0.0001 or more at the temperature.

[0049] In order to reduce signal loss in the communication cable, the dielectric constant of the fluororesin (A) is preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and most preferably 2.1 or less. The lower limit is 1.0 or more. Similarly, the dielectric loss tangent is preferably 0.01 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and most preferably 0.0005 or less. The lower limit is 0.0001 or more. The dielectric constant and dielectric loss tangent 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 different from the fluororesin (A). Examples of resins different from the fluororesin (A) include general-purpose resins such as polyethylene resin, polypropylene resin, vinyl chloride resin, and polystyrene resin; and engineering plastics such as nylon, polycarbonate, polyetheretherketone resin, polyphenylene sulfide resin, polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherketone (PEK), and polyetheretherketoneketone (PEEKK), polyethersulfone (PES), liquid crystal polymer (LCP), polysulfone (PSF), amorphous polyarylate (PAR), polyethernitrile (PEN), thermoplastic polyimide (TPI), polyimide (PI), polyetherimide (PEI), and polyamideimide (PAI). These may be used alone or in combination.

[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. The lower limit is not particularly limited, and 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 generation. The upper limit of the crystallite size is preferably 10,000 Å or less, more preferably 5,000 Å or less, and even more preferably 1,000 Å or less. XRD is performed using an X-ray diffractometer (Smart Lab, manufactured by Rigaku Corporation) and measurement and analysis software (Smart Lab Studio II), and powder is measured. CuKα with a wavelength of 1.54 Å is used as the X-ray source, and the diffraction angle (2θ) is 5° to 90°. The crystallite size is calculated using the Scherrer formula from the largest half-width of the obtained diffraction peak. D = K × λ / (β × cos θ) ... Scherrer's formula D: crystallite size (Å) K: Scherrer constant λ: X-ray wavelength (Å) β: half width of diffraction peak (rad) θ: ½ of diffraction angle (rad) Scherrer constant (K) = 0.94, X-ray wavelength (λ) = 1.5418. If the obtained diffraction spectrum does not have a diffraction peak attributable to a crystalline structure, it is considered not to have a crystalline structure.

[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, enabling long-term molding, such as wire molding. The lower limit is not particularly limited, and may be 0% by mass. The volatilization amount is calculated by measuring the mass loss when a sample is held at 330°C for 1 hour in an electric furnace, and dividing the mass loss by the mass before holding x 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 ２ More preferably, 1,000,000 pieces / mm ２ The following is the result.

[0058] From the viewpoint of forming more uniform bubbles, the 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.

[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 a magnification of 150x and processing the image. The center-of-gravity distance and particle size are average values ​​for 100 particles.

[0060] The compound (B) is not particularly limited as long as it satisfies the above-mentioned conditions, but may include tetrapyrrole cyclic compounds, 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 tetrapyrrole cyclic compounds, 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-mentioned conditions are met. The same components will not achieve the same effect if their crystalline state, dispersion state, and volatilization amount differ. Regarding the crystalline state, it is important that the crystallite size measured by X-ray diffraction (XRD) is greater than 100 Å. Regarding the dispersion state, it is important that the components are dispersed in the fluororesin (A) with a center-of-gravity distance of 5.0 μm or less. It is also important that the volatilization amount at 330°C is 7.0% by 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 compound (B) does not decompose and is insoluble or not melted in fluororesin (A) at the molding temperature during foam molding. That is, compound (B) is preferably in a solid state in the foam molding resin composition of the present disclosure when the composition is foam molded. This allows 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 a temperature of 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, while if the content 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 the 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, 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate, barium fluorooctanesulfonate, bisphenol phosphate diester barium salt, 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, bis(4-nitrophenyl)sodium phosphate, triaminobenzene derivatives, 1,3,5-tris(2,2-dimethylpropionylamino)-benzene, Pigment Red 254, talc, sodium binaphthyl phosphate, barium t-butyl-binaphthyl phosphate, rosin metal salts, and condensed phosphate esters. Other examples include sulfonic acid, sulfonate salts, phosphonic acid, phosphonate salts, zeolite, ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), OBSH (4,4'-oxybisbenzenesulfonylhydrazide), etc. These can be used alone or in combination of two or more.

[0069] The resin composition for foam molding of the present disclosure may further contain a polyatomic anion-containing inorganic salt, such as those disclosed in U.S. Pat. No. 4,764,538, within the scope of not impairing the effects of the present disclosure.

[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. 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. Note that "substantially free of a fluorine-based low molecular weight compound" means that the content of a fluorine-based low molecular weight compound is 10 ppm by mass or less.

[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 thereof include perfluoroalkyl acids and perfluorosulfonic acids, and more specific examples thereof include C ８ F １７ COOH and its salts, C ７ F １５ COOH and its salts, C ６ F １３ COOH and its salts, C ８ F １７ SO ３ H and its salts, C６ F １３ SO ３ H and its salts, C ４ F ９ SO ３ H and its salts, C ８ F １７ CH ２ CH ２ -SO ３ H and its salts, C ６ F １３ CH ２ CH ２ -SO ３ H and its salts, C ８ F １７ CH ２ CH ２ OH, C ６ F １３ CH ２ CH ２ OH, etc., and more specifically, {F(CF ２ ) ６ CH ２ CH ２ SO ３} ２ Examples include Ba.

[0075] The content of fluorine-based low molecular weight compounds can be analyzed by the following method: A sample is pulverized by freeze-pulverization, the resulting powder is dispersed in methanol, and extracted by applying ultrasonic waves at 60°C for 2 hours. The extract is quantified using a liquid chromatograph-mass spectrometer (LC-MS / MS), and the value is taken as the content.

[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, it is 5 to 70 g / 10 min, and even more preferably, it is 10 to 60 g / 10 min. Because this can suppress the generation of sparks and increase the foaming rate, it is even more preferably 15 to 50 g / 10 min, even more preferably, 20 to 45 g / 10 min, and particularly preferably, 30 to 45 g / 10 min. The above MFR is a value measured in accordance with ASTM D-1238 using a die with a diameter of 2.1 mm and a length of 8 mm, under a load of 5 kg, at 372°C.

[0077] In order to reduce signal loss in communication cables, the dielectric constant of the resin composition for foam molding of the present disclosure is preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and most preferably 2.1 or less. The lower limit is 1.0 or more. Similarly, the dielectric loss tangent is preferably 0.01 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and most preferably 0.0005 or less. The lower limit is 0.0001 or more. The dielectric constant and dielectric loss tangent of the resin composition for foam molding of the present disclosure are measured by a cavity resonator method at a frequency of 6 GHz using the resin composition before foam molding.

[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) a foam-molded resin composition of the present disclosure. The foam-molded article of the present disclosure is formed using the foam-molding resin composition of the present disclosure.

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

[0088] The cells in the foamed molded article of the present disclosure may be open cells or closed cells, but closed cells are preferred. Closed cells have the advantages of strong resilience against external pressure, excellent rigidity, impact absorption, and processability, and also preventing moisture and other substances from penetrating into the interior. Closed cells can be formed by the above-mentioned hot melt molding or by any conventionally known method.

[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 can be particularly suitably used 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.

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

[0093] (-CF ２ Measurement of the number of H-terminal groups) A nuclear magnetic resonance spectrometer AC300 (manufactured by Bruker-Biospin) was used, and the measurement temperature was set at the melting point of the fluororesin (A) + 20°C. １９ F-NMR measurement was carried out to find that -CF ２ It was calculated from the integral value of the peak due to the presence of H groups and the integral values ​​of other peaks.

[0094] (SSG) Measured 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 at a temperature rise rate of 10° C. / min using a DSC (RDC220 manufactured by Seiko Denshi Co., Ltd.).

[0096] (Thermal Decomposition Temperature) The temperature at which a sample loses 1% of its weight when heated in air at 10° C. / min was measured by TG.

[0097] (MFR) The MFR was measured in accordance with ASTM D-1238 using a KAYENESS Melt Indexer Series 4000 (manufactured by Yasuda Seiki Co., Ltd.) with a die having a diameter of 2.1 mm and a length of 8 mm at 372° C. and a load of 5 kg.

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

[0099] (Preparation of FEP pellets) Fluorinated FEP pellets were prepared in the same manner as in Example 2 of JP-A 2011-514407. The obtained 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 an unstable terminal group and -CF ２ Total number of carbon atoms and H terminal groups: 1 x 10 ６ There were three per piece.

[0100] (Preparation of pellets for batch foaming test (step 1)) Additives were blended into FEP pellets (MFR: 38 g / 10 min) to achieve the desired concentration, and the mixture was kneaded in a Labo Plastomill at 300°C for 10 minutes to prepare a compound. The recovered compound was cut and extruded using an MFR measuring device at 300°C under a load of 5 kg, and the extruded strands were cut into 2-3 mm pieces to prepare pellets. The cross-sections of the prepared pellets were 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 taken as the average values ​​of 100 particles.

[0101] (Batch foaming test (step 2)) The internal volume was approximately 11 cm after being fully preheated in a 270°C electric furnace. ３0.4 g of pellets wrapped in aluminum foil were placed in a pressure vessel and returned to the electric furnace. Up to three samples were placed simultaneously in one test. The vessel was pressurized to 3 MPa with nitrogen gas, held for 60 minutes, and then rapidly depressurized to atmospheric pressure within 1 second to foam the resin. The resulting foamed molded article maintained its pellet shape. It was also not in an unfoamed state (a state in which only cracks occurred). SEM images of the cross section of the foamed molded article were taken and processed to calculate the number of bubbles per unit area. The ratio of this ratio to the number of bubbles generated when a resin without additives was subjected to the same treatment was used as the bubble number index per unit area. The average area per unit bubble was calculated, and the ratio of this ratio to the area of ​​bubbles generated when a resin without additives was subjected to the same treatment was used as the average bubble area index.

[0102] (Crystallite Size) X-ray diffractometer: Smart Lab manufactured by Rigaku Corporation, and measurement and analysis software: Smart Lab Studio II, were used to measure the powder. CuKα with a wavelength of 1.54 Å was used as the X-ray source, and the diffraction angle (2θ) was 5° to 90°. The crystallite size was calculated using the Scherrer formula from the largest half-width of the obtained diffraction peak. D = K × λ / (β × cos θ) ... Scherrer 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) Scherrer constant (K) = 0.94, X-ray wavelength (λ) = 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) A sample (additive) was kept at 330° C. for 1 hour in an electric furnace, and the mass loss was measured. The volatilization amount was calculated by (mass loss / mass before keeping×100).

[0104] (Content of Fluorine-Based Low-Molecular-Weight Compounds) The sample was pulverized by freeze-pulverization, and the resulting powder was dispersed in methanol and extracted by applying ultrasonic waves for 2 hours at 60° C. The extract was quantified using a liquid chromatograph-mass spectrometer (LC-MS / MS), and the content was determined as the value.

[0105] (Dielectric Constant, Dielectric Loss Tangent) Pellets for 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, 1 part by weight 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, volatilization amount in volatility test: 0.4% by weight) was added to 100 parts by weight of FEP pellets to prepare pellets, and in step 2, a foamed molded article 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 batch foaming test in step 2 showed a good bubble count index of 21 per unit area. Furthermore, no fluorine-based low-molecular-weight compounds were detected in the pellets used or the foamed molded article produced. Fluorine-based low-molecular-weight compounds were also not detected in the subsequent examples and comparative examples. Furthermore, at the foaming temperature, the copper phthalocyanine did not decompose and was neither insoluble nor melted in FEP. Furthermore, SEM images of the cross-section of the foamed molded article confirmed the formation of closed cells. Closed cells were also formed in the subsequent 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%) 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 count 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 Balloons did not decompose and were insoluble in and did not melt in FEP.

[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, 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 2.9 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 and not melted in 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 peaks were 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 number 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 peaks were 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 number index per unit area in the batch foaming test in step 2 was a small 0.2.

[0117] Comparative Example 7 A foamed molded article was obtained in the same manner as in Example 1, except that no additive was used. 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]

Claims

1. 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% by mass or less at 330°C, wherein the compound (B) is dispersed in the fluororesin (A) with a center-of-gravity distance of 5.0 μm or less.

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

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

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

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

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

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

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

9. The resin composition for foam molding according to any one of claims 1 to 8, wherein the compound (B) has a crystallite size of 200 to 1,000 Å as measured by X-ray diffraction and a volatilization amount at 330°C of 1.0 mass % or less.

10. The resin composition for foam molding according to any one of claims 1 to 9, 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 any one of claims 1 to 10, wherein the above is dispersed.

12. The resin composition for foam molding according to any one of claims 1 to 11, wherein the compound (B) is dispersed in the fluororesin (A) with particles having a diameter of 4.0 μm or less.

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

14. A resin composition for foam molding according to any one of claims 1 to 13, wherein the compound (B) comprises at least one selected from the group consisting of tetrapyrrole cyclic compounds, barium sulfate, silicon dioxide, and aluminum oxide.

15. The resin composition for foam molding according to any one of claims 1 to 14, wherein the compound (B) contains copper phthalocyanine.

16. The resin composition for foam molding according to any one of claims 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).

17. The resin composition for foam molding according to any one of claims 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).

18. A foamed molded article formed using the foam-molding resin composition according to any one of claims 1 to 17.

19. A method for producing a foamed molded article, comprising a step of foam-molding the resin composition for foam molding according to any one of claims 1 to 17.

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

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