Resin composition for foam molding, interlayer insulator, layered body, and foamed electric wire

Abstract

The purpose of the present disclosure is to provide: a resin composition for foam molding that demonstrates good foaming; an interlayer insulator; a layered body; and a foamed electric wire. The present disclosure provides a resin composition for foam molding that contains a melt-moldable fluororesin and that has a maximum biaxial extensional viscosity of 1×105 to 1×107Pa•s.

Description

Resin composition for foam molding, interlayer insulator, laminate, and foam electric wire

[0001] The present disclosure relates to a resin composition for foam molding, an interlayer insulator, a laminate, and a foam electric wire.

[0002] Cables (electric wires) for high-speed communications operate at high frequencies and have large signal attenuation, so there is a demand for low dielectric constant covering materials.

[0003] As a method for reducing the dielectric constant, it is known to use a foamed fluorine material (see, for example, Patent Documents 1 to 3).

[0004] Japanese Patent Publication No. 2019-112563 Chinese Patent Application Publication No. 116144127 International Publication No. 2006 / 123694

[0005] An object of the present disclosure is to provide a resin composition for foam molding, an interlayer insulator, a laminate, and a foamed electric wire that are in a good foamed state.

[0006] The present disclosure (1) includes a melt-moldable fluororesin, and has a maximum biaxial extensional viscosity of 1×10 ５ ~1 x 10 ７ The foam molding resin composition has a viscosity of Pa·s.

[0007] The present disclosure (2) is the resin composition for foam molding according to the present disclosure (1), wherein the melt flow rate of the fluororesin is 1 to 100 g / 10 min.

[0008] The present disclosure (3) is the resin composition for foam molding according to the present disclosure (1) or (2), further comprising another resin different from the fluororesin.

[0009] The present disclosure (4) is the resin composition for foam molding according to the present disclosure (3), in which the melt flow rate of the other resin is less than 1 g / 10 min.

[0010] The present disclosure (5) is the resin composition for foam molding according to the present disclosure (3) or (4), in which the other resin is polytetrafluoroethylene.

[0011] The present disclosure (6) is the resin composition for foam molding according to any one of the present disclosures (3) to (5), in which the content of the other resin is more than 0.15% by mass and 3% by mass or less.

[0012] The present disclosure (7) is the resin composition for foam molding according to the present disclosure (6), in which the content of the other resin is 0.2 to 1 mass %.

[0013] The present disclosure (8) is the resin composition for foam molding according to any one of the present disclosures (1) to (7), wherein the melting point of the fluororesin is 250° C. or higher.

[0014] The present disclosure (9) is the resin composition for foam molding according to any one of the present disclosures (1) to (8), wherein the fluororesin is a tetrafluoroethylene / hexafluoropropylene copolymer.

[0015] The present disclosure (10) is a method for manufacturing a fluororesin comprising the steps of: ３ The resin composition for foam molding according to any one of (1) to (9) of the present disclosure contains a terminal group.

[0016] The present disclosure (11) is the resin composition for foam molding according to any one of the present disclosures (1) to (10), wherein the content of the fluororesin is 80 to 99.99 mass%.

[0017] The present disclosure (12) is the resin composition for foam molding according to the present disclosure (11), in which the content of the fluororesin is 97% by mass or more and less than 99.85% by mass.

[0018] The present disclosure (13) is the resin composition for foam molding according to any one of the present disclosures (1) to (12), further comprising a foam nucleating agent.

[0019] The present disclosure (14) is the resin composition for foam molding according to the present disclosure (13), wherein the foam nucleating agent is boron nitride and / or sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate.

[0020] The present disclosure (15) is the resin composition for foam molding according to the present disclosure (13) or (14), wherein the content of the foam nucleating agent is 0.1 to 10 mass %.

[0021] The present disclosure (16) is the resin composition for foam molding according to the present disclosure (15), wherein the content of the foam nucleating agent is 0.1 to 3 mass %.

[0022] The present disclosure (17) is the resin composition for foam molding according to any one of the present disclosures (1) to (16), which is substantially free of a fluorine-based low-molecular-weight compound.

[0023] The present disclosure (18) is an interlayer insulator formed using the resin composition for foam molding according to any one of the present disclosures (1) to (17).

[0024] The present disclosure (19) is a laminate having a conductor and a foam layer formed on the conductor using the resin composition for foam molding according to any one of the present disclosures (1) to (17).

[0025] The present disclosure (20) is a foamed electric wire having a conductor and a foamed insulation layer formed on the conductor using the resin composition for foam molding according to any one of the present disclosures (1) to (17).

[0026] According to the present disclosure, it is possible to provide a resin composition for foam molding, an interlayer insulator, a laminate, and a foam electric wire that are in a good foamed state.

[0027] 1 is a circuit diagram of an apparatus used in the improved bubble method. FIG. 2 is a detailed view of a resin installation section.

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

[0029] The foam-molding resin composition of the present disclosure contains a melt-moldable fluororesin and has a maximum biaxial extensional viscosity of 1×10 ５ ~1 x 10 ７ It is Pa·s.

[0030] The resin composition for foam molding according to the present disclosure contains a melt-moldable fluororesin and has a maximum biaxial extensional viscosity within the above range, thereby suppressing cell coalescence and achieving a good foam state. Note that a good foam state is a foam state that is advantageous for achieving a low dielectric constant, such as a state in which fine bubbles are uniformly dispersed.

[0031] Melt-moldable fluororesins usually have high melting points and low viscosities, making it difficult to measure their extensional viscosity. Therefore, in this disclosure, the biaxial extensional viscosity is measured (calculated) using the improved bubble method described below.

[0032] The improved bubble method is a new testing method developed at Yamagata University. Gas is blown into molten resin to form bubbles, the cross-sectional area of ​​which is measured with a high-speed camera, and the biaxial extensional viscosity is then calculated using the following formula. ηＢＩ : Biaxial elongational viscosity (Pa・s) r ｂ : bubble radius (m) V ｒ :r ｂ Time derivative of P ｉｎ : Bubble internal pressure (Pa) P ｏ : atmospheric pressure (Pa) Δr: bubble film thickness (m) ρ: melt density (kg / m ３ ) t: time (s)

[0033] An example of an apparatus used in the improved bubble method is shown in Figures 1 and 2. Figure 1 is a circuit diagram of the apparatus used in the improved bubble method, and Figure 2 is a detailed view of the resin installation section. As shown in Figures 1 and 2, the apparatus 10 includes an electric furnace 1 and a resin installation section 2 provided within the electric furnace 1. After the sample (resin) heated in the electric furnace 1 melts, nitrogen gas is blown in, causing the molten resin to be ejected in the form of bubbles from an opening 2a at the bottom of the resin installation section 2. A regulator 3, a ball valve 4, and a pressure sensor 5 are provided on the path from the nitrogen gas inlet to the electric furnace 1.

[0034] The specific operating procedure of the improved bubble method is as follows: (1) The resin composition is molded into a sheet of 1 mm thickness using a heat press at 360°C, and the sheet is then slowly cooled to below the crystallization temperature. (2) The sheet is cut into a Φ25 mm piece to obtain a sample. (3) The electric furnace is preheated to a temperature equal to or higher than the measurement temperature. (4) After confirming that the temperature of the resin installation section in the electric furnace has reached the measurement temperature or higher, the sample is installed in the resin installation section. (5) After the sample has melted, once it has reached the measurement temperature, the sample is expanded into a bubble (balloon-like) shape using nitrogen gas. At this time, the behavior during expansion is observed using a high-speed camera (Keyence VW-600C), and the nitrogen gas pressure (P ｉｎ -P ０ (6) Only the bubble is sampled and weighed. (7) A video of the bubble taken from the side by a high-speed camera is analyzed, and an image is taken from the point where the bubble begins to expose from the resin placement part to one frame before the expanded bubble bursts. The cross-sectional area of ​​the resin exposed from the resin placement part in the image is calculated, and the radius of the circle equivalent to that cross-sectional area is taken as the bubble radius (r ｂ (8) Based on the measurement results, the biaxial extensional viscosity (η ＢＩ) is calculated. In the above calculation formula, r ｂ Time derivative of (V ｒ ) is the bubble radius (r ｂ The bubble film thickness (Δr) is calculated from the sample volume / bubble surface area. The melt density (ρ) is the density of the sample at the measurement temperature. The others are measured values.

[0035] The biaxial extensional viscosity calculated by the modified bubble method usually tends to increase as the bubbles grow. The resin composition for foam molding of the present disclosure has a maximum biaxial extensional viscosity measured by the modified bubble method of 1×10 ５ ~1 x 10 ７ It was found that the foaming state is good when the viscosity is 1.5 Pa s, and the foaming state is good when the viscosity is 1.5 Pa s. ５ or more, more preferably 2 × 10 ５ More preferably, 2.5×10 ５ or more, and even more preferably 3×10 ５ or more, and even more preferably 3.5 × 10 ５ or more, and even more preferably 4×10 ５ or more, and preferably 1×10 ６ or less, more preferably 9.5 × 10 ５ More preferably, 9 × 10 ５ or less, and even more preferably 8.5 × 10 ５ or less, and even more preferably 8 x 10 ５ or less, and even more preferably 7.5 x 10 ５ or less, and even more preferably 7 x 10 ５ or less, and even more preferably 6.5 × 10 ５ or less, and even more preferably 6 x 10 ５ The minimum value of the biaxial extensional viscosity is not particularly limited, and is theoretically 0, but may be 2.

[0036] The biaxial extensional viscosity increases by widening the molecular weight distribution of the resin used.As a method of widening the molecular weight distribution, for example, the method of dimerizing the resin can be mentioned.When dimerizing, molecules with different chain lengths are closely intertwined with each other, more specifically, the dispersion state is good, and the difference in chain length between molecules is large, so that the biaxial extensional viscosity increases.When using a resin with high molecular weight, it is particularly preferable that the dispersion is good, but if the maximum diameter of the resin after dispersion is 10 μm or less, the biaxial extensional viscosity will be sufficiently large.As a method for highly dispersing a resin with high molecular weight in a composition, the co-coagulation method described below is effective.In addition, the biaxial extensional viscosity can also be increased by crosslinking the resin.On the other hand, if there is aggregate in the resin or if there is other components such as filler in the resin, they will break from the interface during elongation, so that the biaxial extensional viscosity will be reduced.

[0037] Hereinafter, the melt-moldable fluororesin used in the foam-molding resin composition of the present disclosure will be referred to as fluororesin (A). The fluororesin (A) is not particularly limited as long as it is melt-moldable, and examples thereof 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 of two or more.

[0038] 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.

[0039] 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.

[0040] The fluororesin (A) is preferably at least one selected from the group consisting of a TFE / HFP copolymer, a TFE / PAVE copolymer, and a TFE / ethylene copolymer, and more preferably a TFE / HFP copolymer, because of its excellent heat resistance. Also, a perfluororesin is preferred because of its superior electrical properties.

[0041] 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.

[0042] The TFE / PAVE copolymer preferably has a mass ratio of TFE / PAVE of 90-99 / 1-10, more preferably 92-97 / 3-8.

[0043] 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.

[0044] 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.

[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,３ It 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 %, for ease of handling. 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 exposing 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 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, since this allows for the production of foamed molded articles with excellent heat resistance and a wide continuous use temperature range. Furthermore, the melting point is more preferably 250°C or higher, and preferably 300°C or lower. The molding temperature is more preferably 300°C or higher, and preferably 450°C or lower. The thermal decomposition temperature is more preferably 350°C or higher, and 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 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 1% weight loss occurs when heated in air at 10°C / min as measured by 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 2.6 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 0.001 or less, and most preferably 0.0004 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 foam-molding resin composition of the present disclosure preferably contains another resin different from the fluororesin (A). The other resin different from the fluororesin (A) is not particularly limited and may be a fluororesin that cannot be melt-molded or a resin other than a fluororesin. However, a fluororesin that cannot be melt-molded is preferred because it increases the biaxial extensional viscosity and results in a better foamed state. Hereinafter, the fluororesin that cannot be melt-molded used in the foam-molding resin composition of the present disclosure will be referred to as fluororesin (B). 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.

[0052] The fluororesin (B) is not particularly limited as long as it is a fluororesin that cannot be melt-molded, and examples thereof include polytetrafluoroethylene (PTFE). Also, FEP, PFA, ETFE, PCTFE, PVDF, etc., exemplified as fluororesin (A), can be used. One or more of these can be used. Among these, PTFE is preferred. Note that, among the FEPs exemplified as fluororesin (A), if the MFR is less than 1 g / 10 min, they are fluororesin (B), and if the MFR is 1 g / 10 min or more, they are fluororesin (A). Therefore, for example, FEP corresponding to fluororesin (A) and FEP corresponding to fluororesin (B) may be used in combination.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Examples of resins that can be used as the resin other than the fluororesin (A) other than the fluororesin (B) 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), polyetheretherketoneketone (PEEKK), etc.), 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.

[0057] The content of the other resin different from the fluororesin (A) is preferably more than 0.15% by mass, more preferably 0.16% by mass or more. It is even more preferably 0.17% by mass or more, even more preferably 0.2% by mass or more, even more preferably 0.25% by mass or more, and even more preferably 0.4% by mass or more. The upper limit is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. If the content of the other resin is too low, the effect of increasing the biaxial elongational viscosity may not be sufficiently obtained, and if the content is too high, poor dispersion may result in breakage of the coating during the formation of the electric wire coating.

[0058] Preferably, fluororesin (A) and other resin are mixed by co-coagulation.Mixing by co-coagulation can be carried out by, for example, mixing the aqueous dispersion that contains fluororesin (A) and the aqueous dispersion that contains other resin, and then coagulating.In this specification, mixing the aqueous dispersions of polymers and then coagulating is referred to as " co-coagulation ".

[0059] Co-coagulation can be carried out by conventional method as appropriate.The polymer solid content concentration in each polymer aqueous dispersion is not particularly limited, and can be appropriately set according to the type and amount of each polymer used, but is preferably 1 to 70 mass%, more preferably 3 to 50 mass%.The aqueous medium constituting each polymer aqueous dispersion can be any one that contains water, but can also contain water-soluble organic solvent such as water-soluble alcohol, or can not contain said water-soluble organic solvent.In addition, in order to improve dispersibility, each polymer aqueous dispersion preferably contains conventionally known surfactant etc., within the range that does not impair the moldability of the resin obtained.

[0060] The polymer aqueous dispersions can be mixed using, for example, a high-speed stirrer. The mixed solution obtained by mixing two types of polymer aqueous dispersions is preferably adjusted so that the total polymer solids concentration is 5 to 40 mass %.

[0061] The coagulation method in coagulation is not particularly limited, and for example, can be listed as the salt coagulation that uses nitric acid, hydrochloric acid etc. as coagulant.In addition, can also be listed as the method that does not use coagulant, and mechanically coagulates by stirring etc.

[0062] After co-coagulation, it is preferable to separate the resin by suction filtration, and repeat washing with water and suction filtration until the pH becomes neutral.Then, it is preferable to dry the recovered resin (wet powder).It is preferable to dry it at a temperature of 100 to 240 ° C for 2 to 48 hours.At this time, it is possible to take measures to accelerate drying, such as reducing the pressure or letting dry gas flow.

[0063] The resin composition for foam molding of the present disclosure may further contain a foam nucleating agent, which improves the foam state. Examples of foam nucleating agents 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-dioctadecylisophthalic acid amide, 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, sulfonates, phosphonic acid, phosphonates, zeolites, ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), and OBSH (4,4'-oxybisbenzenesulfonylhydrazide). Among these, boron nitride and sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate are preferred. These may be used alone or in combination.

[0064] The average particle size of boron nitride is more preferably 9.0 μm or more, even more preferably 10.0 μm or more, even more preferably 10.5 μm or more, particularly preferably 11.0 μm or more, particularly more preferably 12.0 μm or more, and most preferably 13.0 μm or more. Furthermore, if the average particle size of boron nitride is too large, the average bubble size may become large and frequent sparks may occur. The average particle size of boron nitride is preferably 25 μm or less, more preferably 20 μm or less. By having the average particle size of boron nitride within the above range, a coating material having fine, uniform bubbles can be formed. The average particle size of boron nitride is a value determined using a laser diffraction / scattering particle size distribution analyzer. When using a wet method, the medium may be appropriately selected, for example, methanol or the like may be used.

[0065] The particle size distribution of boron nitride, expressed as (D84-D16) / D50, is preferably 1.2 or less. When the total volume of the boron nitride powder mass is taken as 100%, D84, D50, and D16 represent the particle size (μm) at the 84%, 50%, and 16% points of the cumulative curve. The particle size distribution is accumulated from the smallest particle size side. The total volume of the powder mass is measured by preparing a sample in which boron nitride powder is dispersed in a medium such as methanol and analyzing it using a laser diffraction / scattering particle size distribution analyzer (e.g., the Microtrac MT3300 manufactured by Nikkiso Co., Ltd.). Having a particle size distribution of boron nitride within the above range enables the formation of a coating material with fine, uniform bubbles and further suppresses the generation of sparks. The particle size distribution is more preferably 1.1 or less, and even more preferably 1.0 or less. The lower limit of the particle size distribution is not particularly limited, but may be, for example, 0.1. The cumulative curve of the particle size distribution (volume particle size distribution) is obtained using a laser diffraction / scattering particle size distribution analyzer (e.g., Microtrac MT3300 manufactured by Nikkiso Co., Ltd.). When a wet method is used, the medium may be appropriately selected, and for example, methanol or the like may be used.

[0066] The boron nitride is preferably pulverized. When the boron nitride is pulverized, the generation of sparks can be further suppressed. The pulverization can be carried out by a method and under conditions that allow the average particle size and particle size distribution of the boron nitride to fall within the above ranges. For example, the type and conditions of the pulverizer can be appropriately selected. As the pulverizer, for example, a jet mill, a hammer mill, a ball mill, a pin mill, etc. can be used.

[0067] The boron nitride may be classified to adjust the average particle size or particle size distribution within the above range.

[0068] The average particle size of 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate is more preferably 20.0 μm or less, even more preferably 10.0 μm or less, even more preferably 5.0 μm or less, and most preferably 2.0 μm or less. Furthermore, if the average particle size of 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate is too small, the effect as a foam nucleating agent may be reduced. The average particle size of 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate is preferably 0.001 μm or more, more preferably 0.01 μm or more. By having the average particle size of 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate within the above range, a coating material having fine, uniform bubbles can be formed. The average particle size of 2,2'-methylenebis(4,6-di-t-butylphenyl)sodium phosphate can be measured in the same manner as the average particle size of boron nitride.

[0069] In the resin composition for foam molding of the present disclosure, the content of the foam nucleating agent is not particularly limited, but is, for example, preferably 0.1 to 10 mass%, more preferably 0.1 to 3 mass%, even more preferably 0.1 to 1.5 mass%, and still more preferably 0.1 to 1.0 mass%. If the content of the foam nucleating agent is too low, the effect of adding the foam nucleating agent may not be fully obtained, and if it is too high, the production costs may increase.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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 or less.

[0075] The fluorine-based low molecular weight compound is not particularly limited, and examples thereof include perfluoroalkyl acids and perfluorosulfonic acids. 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, C ６ 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.

[0076] The content of fluorine-based low-molecular-weight compounds can be analyzed by the following method: Pellets of the resin composition for foam molding are pulverized by freeze-pulverization, and 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 chromatography mass spectrometer (LC-MS / MS), and the value is taken as the content.

[0077] 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.

[0078] The resin composition for foam molding of the present disclosure can be obtained, for example, by a production method including a mixing step of mixing the fluororesin (A) with other resins and the like that are added as needed to obtain a mixture.

[0079] As the above-mentioned mixing method, for example, conventionally known methods can be used, but the mixing method that can increase biaxial extensional viscosity is preferred.Above-mentioned mixing method can also include the method that uses Henschel mixer, ribbon mixer, V blender, ball mill etc.In addition, for example, the method that uses melt-kneading to mix.When fluororesin (A) is used together with other resin, because it can increase biaxial extensional viscosity, above-mentioned co-coagulation is preferred.

[0080] The production method may include a kneading step of kneading the mixture obtained in the mixing step. Pellets can be obtained by the kneading. The kneading can be performed, for example, by a method using a conventional melt kneader such as a single-screw extruder or a twin-screw extruder.

[0081] The above-mentioned production method may include a step of fluorinating the fluororesin. The fluorination treatment can be performed by the above-mentioned method. The fluorination treatment may be performed, for example, by contacting the pellets obtained by the above-mentioned kneading with the above-mentioned fluorine-containing compound.

[0082] 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.

[0083] The method for foam-molding the foam-molding resin composition is not particularly limited, and for example, a conventionally known method can be used, such as a method in which the foam-molding resin composition of the present disclosure is fed into a screw extruder designed for foaming operations and a continuous gas extrusion method is used.

[0084] The gas used in the gas extrusion method may be, for example, chlorodifluoromethane, nitrogen, carbon dioxide, or a mixture of these gases, and may be introduced into the molten resin in the extruder as a pressurized gas, or may be generated by mixing a chemical foaming agent into the molten resin. The introduced gas dissolves in the molten resin in the extruder.

[0085] Gases dissolved in the resin escape from the melt due to the sudden drop in melt pressure as it exits the extrusion die. The extrudate is then cooled and solidified, for example by immersion in water.

[0086] The foam-molded article obtained by foam-molding the resin composition for foam molding of the present disclosure has a low dielectric constant, exhibits stable capacitance, is lightweight, and can be used as a coating material (described below) with stable dimensions such as wire diameter and thickness. The total volume of bubbles in the foam-molded article 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.

[0087] The foaming state of the foamed molded product can be determined by, for example, the cell density x MFR of the composition. ２ ((pcs / mm ２ )・(g / 10 minutes) ２ The foam density can be determined by multiplying the MFR of the composition by the foam density. ２ The larger the value, the more uniformly dispersed fine bubbles there are, and the better the foaming state. ２The value is preferably 5550 or more, more preferably 5650 or more, even more preferably 5750 or more, and particularly preferably 5850 or more. There is no particular upper limit, but it is preferably 8000 or less, more preferably 7800 or less, even more preferably 7600 or less, still more preferably 7400 or less, still more preferably 7200 or less, and particularly preferably 7000 or less.

[0088] The foamed molded article is obtained as a molded article shaped according to the intended use during extrusion from the extruder. The molding method is not particularly limited as long as it is hot melt molding, and examples thereof include extrusion foam molding, injection foam molding, and mold foam molding.

[0089] The shape of the foam molded article is not particularly limited and can be various shapes, such as a covering material for foamed electric wires, a filament-like wire material, a sheet-like shape, a film-like shape, a rod-like shape, or a pipe-like shape. The foam molded article can be used, for example, as an electrical insulating material, a heat insulating material, a sound insulating material, a lightweight structural material such as a floating material, or a shock-absorbing material such as a cushion. The foam molded article is particularly suitable for use as a covering material for foamed electric wires. The resulting foam molded article contains a molten and solidified product of the foam molding resin composition of the present disclosure and bubbles, and the bubbles are preferably uniformly distributed throughout the molten and solidified product. The average bubble diameter of the bubbles is not particularly limited, but is preferably, for example, 60 μm or less. The average bubble diameter is preferably 0.1 μm or more. The foam ratio of the foam molded article is not particularly limited, but is preferably 20% or more. The upper limit of the foam ratio is not particularly limited, but is, for example, 80%.

[0090] The interlayer insulator of the present disclosure is formed using the resin composition for foam molding. Since the interlayer insulator of the present disclosure is in a foamed state that is advantageous for achieving a low dielectric constant, it can be used, for example, as an insulating layer for electric wires, an insulating layer for semiconductor package substrates, an insulating layer for transformers, an insulating layer for circuit boards, an insulating layer for motors, an insulating layer for reactors, an insulating layer for transistors, an insulating layer for printed circuit boards, an insulating layer for semiconductor devices, an insulating layer for electronic components, etc., and is particularly suitable for use as an insulating layer (coating layer) for electric wires.

[0091] The laminate of the present disclosure includes a conductor and a foam layer formed on the conductor using the foam molding resin composition. Because the laminate of the present disclosure includes a foam layer in a foamed state advantageous for achieving a low dielectric constant, it can be used, for example, in printed wiring boards, power module substrates, coils used in power devices such as motors, secondary batteries such as lithium-ion batteries, primary batteries such as lithium batteries, radical batteries, solar cells, fuel cells, lithium-ion capacitors, hybrid capacitors, electric double-layer capacitors, capacitors (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical switching elements, electrode separators, etc. The laminate of the present disclosure can also be used in antenna components, printed circuit boards, aircraft components, automotive components, heat dissipation components, etc. Specifically, the material can be used as a wire coating material (aircraft wires, rectangular wires, FFC (Flexible Flat Cable), etc.), an enameled wire coating material used in motors of electric vehicles and the like, a power generation coating material, an electrical insulating tape, an insulating tape for oil drilling, a material for printed circuit boards, a tape substrate film for semiconductor manufacturing processes (dicing tape, pickup tape, etc.), a release film for semiconductor molding, a liquid crystal antenna, a transmission path, a base film for COF (chip on film), an electrostatic chuck for semiconductor manufacturing processes, an electrostatic chuck for display manufacturing processes, a heat dissipation substrate for mounting power devices, a heat dissipation member for wireless communication devices, a transistor, a thyristor, a rectifier, a transformer, a power MOS FET, a CPU, a heat dissipation fin, a metal heat sink, an electronic device material, a sealing material for plasma processing equipment, etc., a heat dissipation part in a processing unit of a sputtering or various dry etching equipment, etc., and an electromagnetic wave shield. The laminate of the present disclosure can also be used as an electronic substrate material such as a flexible printed wiring board or a rigid printed wiring board, a protective film, or a heat dissipation substrate (particularly a heat dissipation substrate for automobiles). The laminate of the present disclosure can be particularly suitably used as an electric wire.

[0092] The foamed electric wire of the present disclosure has a conductor and a foamed insulation layer (coating layer) formed on the conductor using the foam molding resin composition. The foamed electric wire of the present disclosure has a foamed insulation layer in a foamed state that is advantageous for achieving a low dielectric constant, and therefore can suppress signal attenuation compared to conventional electric wires.

[0093] Examples of materials that can be used for the conductor (core wire) include metal conductor materials such as copper and aluminum, and carbon. The conductor may be made of a single material, or the surface may be plated with silver, tin, or the like. The conductor preferably has a diameter of 0.02 to 3 mm. The conductor diameter is more preferably 0.04 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. The conductor diameter is more preferably 2 mm or less. The conductor may be a solid wire or a stranded wire made by twisting together multiple conductors. The shape of the conductor is not particularly limited, and examples include a flat shape and rectangular wire.

[0094] Specific examples of the conductor (core wire) include AWG (American Wire Gauge)-46 (solid copper wire with a diameter of 40 micrometers), AWG-42 (solid copper wire with a diameter of 64 micrometers), AWG-36 (solid copper wire with a diameter of 127 micrometers, a wire with a total diameter of 153 micrometers formed by twisting seven copper wires with a diameter of 51 micrometers), AWG-30 (solid copper wire with a diameter of 254 micrometers, a wire with a total diameter of 306 micrometers formed by twisting seven copper wires with a diameter of 102 micrometers), AWG-27 ​​(solid copper wire with a diameter of 361 micrometers), AWG-26 (solid copper wire with a diameter of 404 micrometers), AWG-24 (solid copper wire with a diameter of 510 micrometers), and AWG-22 (solid copper wire with a diameter of 635 micrometers).

[0095] The thickness of the foamed insulation layer (coating layer) is preferably 0.01 to 3.0 mm, and also preferably 2.0 mm or less.

[0096] The foamed electric wire of the present disclosure can be used as cables for connecting computers and their peripheral devices, cables for communicating high-capacity video and audio at high speed, cables for connecting servers in a data center, for example, LAN cables, USB cables, Lightning cables, Thunderbolt cables, CATV cables, HDMI (registered trademark) cables, QSFP cables, aerospace cables, underground power transmission cables, submarine power cables, high-voltage cables, superconducting cables, wrapped electric wires, automotive wires, wire harnesses and electrical components, electric wires for robots and factory automation (FA), electric wires for office automation equipment, electric wires for information equipment (optical fiber cables, audio cables, etc.), internal wiring for communication base stations, high-current internal wiring (inverters, power conditioners, storage battery systems, etc.), internal wiring for electronic devices, wiring for small electronic devices and mobile devices, wiring for moving parts, internal wiring for electrical equipment, internal wiring for measuring instruments, power cables (for construction, wind power / solar power generation, etc.), control / instrumentation wiring cables, motor cables, etc.

[0097] The foamed electric wire of the present disclosure may have a two-layer structure (skin-foam) in which a non-foamed layer is inserted between the core wire and the covering material, a two-layer structure (foam-skin) in which a non-foamed layer is coated on the outer layer, or even a three-layer structure (skin-foam-skin) in which a non-foamed layer is coated on a skin-foam outer layer. The non-foamed layer is not particularly limited, and may be a resin layer made of a resin such as a TFE / HFP copolymer, a TFE / PAVE copolymer, a TFE / ethylene copolymer, a vinylidene fluoride polymer, a polyolefin resin such as polyethylene (PE), or polyvinyl chloride (PVC).

[0098] 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.

[0099] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0100] 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

[0101] (-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.

[0102] (Content of Fluorine-Based Low-Molecular-Weight Compounds) The content was measured by the method described above.

[0103] (SSG) Measured based on the immersion method in accordance with ASTM D4895-89.

[0104] (Melting Point) The melting point was determined as the temperature corresponding to the peak when measured at a temperature rise rate of 10° C. / min using RDC220 (manufactured by Seiko Denshi Co., Ltd.).

[0105] (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.

[0106] (Biaxial extensional viscosity) The biaxial extensional viscosity was measured by the method described above, and the maximum value is shown in Table 1. The preheating temperature of the electric furnace was 350°C, the resin melting time was 3 minutes, and the measurement temperature was 330°C.

[0107] The examples and comparative examples were carried out in the following manner.

[0108] (FEP) The raw material was a dispersion (aqueous dispersion) obtained by emulsion polymerization using ammonium persulfate as a polymerization initiator. The composition of the fluororesin (FEP) after separation was tetrafluoroethylene [TFE] units, hexafluoropropylene [HFP] units, perfluoro(propyl vinyl ether) [CF ２ =CFOC ３ F ７ (PPVE)] units and had a melting point of 260°C.

[0109] (PTFE) The raw material was an aqueous PTFE dispersion prepared by the method of Example 1 of International Publication No. 2019 / 168183. The composition of the fluororesin (PTFE) after separation was a TFE homopolymer, with an SSG of 2.173, a melting point of 344°C, and an MFR of 0 g / 10 min.

[0110] Comparative Example 1, Examples 1 to 4 An aqueous dispersion (resin content 20% by mass) that is the raw material for FEP was diluted three times, and an aqueous dispersion (resin content 20% by mass) that is the raw material for PTFE was mixed in a ratio that matched the target concentration. The resulting dispersion was stirred using a high-speed mixer (T.K. Robomix (stirring part: Homodisper), manufactured by Tokushu Kika Kogyo Co., Ltd.), 3000 rpm, and then a small amount of nitric acid was added dropwise to form a slurry. Next, the resin was separated by suction filtration, and water washing and suction filtration were repeated until the pH became neutral. The recovered resin was dried at a temperature of 150°C for 6 hours. The dried resin was then simmered at 200°C for 6 hours with fluorine gas (F) diluted to 20% with nitrogen. ２ The resulting resin was fluorinated under the conditions of ２Since there is no H end group, -CF ３ It was confirmed that the resin contained terminal groups. Furthermore, no fluorine-based low molecular weight compounds were detected in the obtained resin. In Example 1, the batch foamability evaluation described below was calculated by multiplying the cell density by the MFR of the composition. ２ In Example 2, the foam density × MFR of the composition ２ In Example 4, the foam density x MFR of the composition ２ In Comparative Example 1, the foam density was 5903, and a good foam with fine bubbles uniformly dispersed was obtained. ２ At 5478, a poor foam was obtained with many bubbles coalescing and large bubbles present.

[0111] Comparative Examples 2 to 7 Materials (FEP pellets and PTFE powder) were placed in a Labo Plastomill (3S150 R60 manufactured by Toyo Seiki Seisakusho) heated to 350°C, and kneaded for 10 minutes at 350°C and 60 rpm. The kneaded resin was then heated at 200°C for 6 hours in a fluorine gas (F) diluted to 20% with nitrogen gas. ２ The resulting resin was fluorinated by contacting it with the unstable terminal group and —CF ２ Since there is no H end group, -CF ３ It was confirmed that the resin contained terminal groups. In addition, no fluorine-based low molecular weight compounds were detected in the obtained resin. The batch foamability evaluation described below was performed by multiplying the cell density of Comparative Example 2 by the MFR of the composition. ２ 5283, cell density of Comparative Example 3 × MFR of composition ２ 5150, cell density of Comparative Example 4 × MFR of composition ２ 5210, cell density of Comparative Example 5 × MFR of composition ２ The results were 5512, and all of the foams were poor in quality, with many bubbles coalescing and large bubbles present.

[0112] The resins (compositions) of the examples and comparative examples were evaluated by the following methods.

[0113] (Batch Foaming Evaluation) Using a Laboplastomill, the compositions of the Examples and Comparative Examples and a foam nucleating agent (boron nitride) were kneaded for 10 minutes at 300°C and 60 rpm. The content of the foam nucleating agent in the kneaded mixture was 1% by mass. Using a melt indexer, the kneaded mixture was formed into a strand at 300°C and cut into pellets. The pellets were placed in capsules made of aluminum foil, and the capsules were placed in a high-pressure vessel preheated to 280°C. The high-pressure vessel was pressurized with gas (nitrogen) and allowed to stand for 60 minutes while maintaining 280°C and 3 MPa, after which the pressure was rapidly reduced (within 1 second) and the capsules were removed. After confirming that the resin had solidified, the resin was removed from the capsule. The resin was cut with a razor, and the cross section was observed with an SEM. The number of bubbles per unit area was determined using an image processing device (Mac-View, manufactured by Mountec) to determine the bubble density (bubbles / mm ２ When the biaxial extensional viscosity is high, the coalescence of bubbles is suppressed, the number of uniformly dispersed fine bubbles increases, and the bubble density is improved. ２ ((pcs / mm ２ )・(g / 10 minutes) ２ The foaming state was evaluated from the value of MFR. The larger the value, the more uniformly dispersed fine bubbles there are, and the better the foaming state. Generally, foaming ability varies depending on MFR, and the lower the MFR, the more likely it is to produce fine bubbles. ２ By applying this, the influence of MFR can be eliminated.

[0114] (Dispersibility Evaluation) Thin pieces of the compositions of the Examples and Comparative Examples were placed on a hot stage and observed with a polarizing microscope (Olympus BX51) under crossed Nicols to evaluate the dispersibility of PTFE. Observation was performed by heating the sample to 300°C, which is above the melting point of FEP but below the melting point of PTFE, then heating it to 360°C, which is above the melting point of PTFE, and then cooling it to 300°C, which is below the melting point of PTFE. In crossed Nicols observation, interference colors appear due to the crystalline components, allowing the crystals to be observed. Since FEP melts at 300°C but PTFE does not, the dispersion state can be confirmed by observing the PTFE crystals. Furthermore, when the temperature is raised to 360°C, which is above the melting point of PTFE, the PTFE disappears, and when the temperature is lowered to 300°C, the PTFE crystals reappear. Foaming nucleating agents such as boron nitride do not melt or disappear even at 360°C, so they can be distinguished from PTFE. PTFE crystals were observed at 300°C, and a maximum diameter of 10 μm or less was rated as ◯, while a maximum diameter of more than 10 μm was rated as ×. When the PTFE dispersibility was rated as ◯, the biaxial elongational viscosity was high, the coalescence of bubbles during foaming was suppressed, and many uniformly dispersed fine bubbles were produced, resulting in a good foaming state.

[0115]

[0116] Although the biaxial extensional viscosity was not measured for Comparative Examples 2 and 5, it is estimated that the viscosity was similar to that of Comparative Example 3 based on the PTFE concentration, mixing method, and the results of the batch foaming evaluation.

[0117] In addition, when the amount (concentration) of PTFE increases, it tends to aggregate and dispersibility deteriorates.Because the PTFE that is added by coprecipitating is good dispersibility even at 1% by mass (Example 4), it is estimated that the dispersibility evaluation of Example 1, 3 that is less than this concentration is good (○).In terms of batch foaming evaluation, it is estimated that Example 3 is equally good as Example 1, 2 from the viewpoint of PTFE concentration, mixing method and biaxial elongation viscosity.

[0118] In addition, in the batch foaming evaluation, boron nitride was used as a foaming nucleating agent, but it is presumed that similar results would be obtained if sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate was used.

[0119] 1: Electric furnace 2: Resin installation section 2a: Opening 3: Regulator 4: Ball valve 5: Pressure sensor 10: Device

Claims

1. Contains melt-moldable fluororesin and has a maximum biaxial elongation viscosity of 1 x 10 ５ ~1 x 10 ７ A resin composition for foam molding having a viscosity of Pa·s.

2. The resin composition for foam molding according to claim 1, wherein the melt flow rate of said fluororesin is 1 to 100 g / 10 min.

3. The resin composition for foam molding according to claim 1 or 2, further comprising a resin other than said fluororesin.

4. The resin composition for foam molding according to claim 3, wherein the melt flow rate of said other resin is less than 1 g / 10 min.

5. The resin composition for foam molding according to claim 3 or 4, wherein said other resin is polytetrafluoroethylene.

6. A resin composition for foam molding according to any one of claims 3 to 5, wherein the content of the other resin is more than 0.15% by mass and not more than 3% by mass.

7. The resin composition for foam molding according to claim 6, wherein the content of said other resin is 0.2 to 1% by mass.

8. The resin composition for foam molding according to any one of claims 1 to 7, wherein the melting point of the fluororesin is 250°C or higher.

9. The resin composition for foam molding according to any one of claims 1 to 8, wherein the fluororesin is a tetrafluoroethylene / hexafluoropropylene copolymer.

10. The fluororesin is -CF ３ The resin composition for foam molding according to any one of claims 1 to 9, which contains a terminal group.

11. The resin composition for foam molding according to any one of claims 1 to 10, wherein the content of the fluororesin is 80 to 99.99 mass %.

12. The resin composition for foam molding according to claim 11, wherein the content of the fluororesin is 97% by mass or more and less than 99.85% by mass.

13. The resin composition for foam molding according to any one of claims 1 to 12, further comprising a foam nucleating agent.

14. The resin composition for foam molding according to claim 13, wherein the foam nucleating agent is boron nitride and / or sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate.

15. The resin composition for foam molding according to claim 13 or 14, wherein the content of the foam nucleating agent is 0.1 to 10% by mass.

16. The resin composition for foam molding according to claim 15, wherein the content of the foam nucleating agent is 0.1 to 3% by mass.

17. The resin composition for foam molding according to any one of claims 1 to 16, which is substantially free of fluorine-containing low molecular weight compounds.

18. An interlayer insulator formed using the resin composition for foam molding according to any one of claims 1 to 17.

19. A laminate comprising a conductor and a foam layer formed on the conductor using the foam-molding resin composition according to any one of claims 1 to 17.

20. A foamed electric wire having a conductor and a foamed insulating layer formed on the conductor using the foam molding resin composition according to any one of claims 1 to 17.

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