Methods for manufacturing sheet materials, methods for manufacturing laminated sheets, and sheet materials

Abstract

The present invention addresses the manufacture of a sheet containing polytetrafluoroethylene (PTFE) particles, inorganic particles, and a specific tetrafluoroethylene-based polymer. Furthermore, the present invention provides a method for manufacturing a laminated sheet comprising a plurality of sheets obtained by the aforementioned manufacturing method, and a method for manufacturing a laminate of the obtained laminated sheet and a substrate. As a solution, the sheet manufacturing method of the present invention involves mixing an agglomerate with particles containing a tetrafluoroethylene-based polymer, and then shaping the resulting mixture; the agglomerate contains PTFE particles and inorganic particles, and the tetrafluoroethylene-based polymer has oxygen-containing polar groups and a melting temperature of 320°C or lower.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a sheet material, and a method for manufacturing a laminated sheet material having a plurality of sheets obtained by the aforementioned manufacturing method. Furthermore, this invention relates to a sheet material. [Previous Technology]

[0002] In the field of information and communication, metal-clad laminates having a metal layer and a resin layer composed of metal foil are used, for example, as printed wiring boards. In recent years, due to the development of high-speed communication technology, there has been a demand for improved performance of metal-clad laminates used in printed wiring boards.

[0003] Polytetrafluoroethylene (PTFE) possesses excellent physical properties such as heat resistance and electrical properties, and therefore is expected to be used as a resin layer in metal-clad laminates of printed wiring boards. At this time, in order to form a resin layer with even better physical properties, a paper has proposed a sheet formed from a co-aggregate of PTFE particles and inorganic particles (see Patent Documents 1 and 2). Previous Art Documents Patent Documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-044288; Patent Document 2: Japanese Patent Application Publication No. 2015-164801 [Summary of the Invention]

[0005] Problems to be Solved by the Invention However, the uniform dispersion of inorganic particles in the above-mentioned sheet is insufficient, and the inorganic particles are prone to falling off the sheet. Therefore, the functionality imparted by the inorganic particles to the obtained sheet is not sufficient. Furthermore, the sheet has low adhesion, making it difficult to directly bond the sheet to a substrate at low temperatures.

[0006] The inventors have discovered that by mixing a condensate containing polytetrafluoroethylene particles and inorganic particles with a specific tetrafluoroethylene-based polymer and then making a sheet from the mixture, the uniform dispersion of inorganic particles in the sheet or the low-temperature adhesion to the substrate can be improved, and the shedding of inorganic particles from the sheet can be suppressed.

[0007] This invention provides a method for manufacturing a sheet containing polytetrafluoroethylene particles, inorganic particles, and a specific tetrafluoroethylene-based polymer. Furthermore, this invention provides a method for manufacturing a laminated sheet of the sheet obtained by the aforementioned method. It also provides a sheet containing inorganic particles with a particle size and specific surface area that are more prone to dust shedding, while effectively suppressing dust shedding.

[0008] The means for solving the problem of the present invention have the following aspects. [1] A method for manufacturing a sheet material, wherein an aggregate is mixed with particles of a tetrafluoroethylene-based polymer, and the resulting mixture is then shaped; the aggregate contains particles of polytetrafluoroethylene and inorganic particles, the tetrafluoroethylene-based polymer having an oxygen-containing polar group and a melting temperature of 320°C or less. [2] The manufacturing method of [1] above, wherein the aggregate is an aggregate obtained by co-aggregation of a mixture, the mixture containing the aforementioned particles of polytetrafluoroethylene, the aforementioned inorganic particles and water. [3] The manufacturing method of [1] or [2] above, wherein when the total mass of the aforementioned particles of polytetrafluoroethylene and the aforementioned inorganic particles is 100% by mass, the content of the aforementioned particles of polytetrafluoroethylene and the aforementioned inorganic particles in the aggregate is as follows: the aforementioned particles of polytetrafluoroethylene are 5% by mass or more and 60% by mass or less, and the aforementioned inorganic particles are 40% by mass or more and 95% by mass or less. [4] The manufacturing method of any one of [1] to [3] above, wherein the aforementioned inorganic particles comprise one selected from the group consisting of metal oxides, silicon oxides and nitrides. [5] The manufacturing method of any one of [1] to [4] above, wherein the average particle size of the aforementioned inorganic particles is 1 to 20 µm and the specific surface area is 1 to 20 m² / g. [6] The manufacturing method of any one of [1] to [5] above, wherein the average particle size of the aforementioned tetrafluoroethylene-containing polymer particles is 0.1 µm or more and 25 µm or less. [7] The manufacturing method of any one of [1] to [6] above, wherein the aforementioned tetrafluoroethylene-containing polymer particles are mixed with the aforementioned aggregate in powder form. [8] The manufacturing method of any one of [1] to [7] above, wherein the aforementioned tetrafluoroethylene-containing polymer particles are dispersed in a dispersion medium and then mixed with the aforementioned aggregate. [9] The manufacturing method of any one of [1] to [8] above, wherein 5 or more and 30 or less of the particles of the aforementioned tetrafluoroethylene-containing polymer are mixed with 100 parts by mass of the aforementioned polytetrafluoroethylene.

[10] The manufacturing method of any one of [1] to [9] above, wherein the aforementioned forming is extrusion forming or rolling forming.

[11] The manufacturing method of any one of [1] to

[10] above, wherein the thickness of the aforementioned sheet is 0.5 mm or more and 5 mm or less.

[12] A method for manufacturing a laminated sheet, wherein two or more sheets are laminated together from the manufacturing method of any one of [1] to

[11] above.

[13] A sheet comprising: polytetrafluoroethylene; a tetrafluoroethylene polymer having an oxygen-containing polar group and a melting temperature of 320°C or less; and inorganic particles having an average particle size of 1 to 20 µm and a specific surface area of ​​1 to 20 m² / g; and, when the total mass of the aforementioned polytetrafluoroethylene and the aforementioned inorganic particles is 100% by mass, the contents of the aforementioned polytetrafluoroethylene and the aforementioned inorganic particles are 5% by mass or more and 60% by mass or less, and 40% by mass or more and 95% by mass or less, respectively.

[14] The sheet as described in

[13] comprises: 5% by mass or more and 30% by mass or less of the aforementioned tetrafluoroethylene polymer relative to 100 parts by mass of the aforementioned polytetrafluoroethylene.

[15] The sheet as described in

[13] or

[14] , wherein the aforementioned inorganic particles comprise at least one selected from the group consisting of metal oxides, silicon oxides and nitrides.

[0009] Effects of the Invention According to the present invention, a method for manufacturing a sheet is provided, wherein the inorganic particles of the sheet have high uniformity of dispersion, suppress inorganic particle powdering, and exhibit excellent low-temperature adhesion. Furthermore, according to the present invention, the obtained laminated sheet and laminate fully possess the original properties of polytetrafluoroethylene and inorganic particles.

Implementation Method

[0010] The following terms have the following meanings: "Tetrafluoroethylene-based polymers" refers to polymers containing units primarily composed of tetrafluoroethylene (hereinafter also denoted as "TFE units"). "Glass transition point (Tg) of the polymer" refers to the value determined by dynamic viscoelasticity analysis (DMA). "Melting temperature of the polymer" refers to the temperature corresponding to the maximum value of the melting peak of the polymer determined by differential scanning calorimetry (DSC). "D50" is the average particle size, which is the particle size accumulated at 50% of the volume basis obtained by laser diffraction. That is, after determining the particle size distribution by laser diffraction, and calculating the cumulative curve with the total volume of the particle group being 100%, the particle size at the point where the cumulative volume is 50% on the cumulative curve. "D90" is the cumulative volume particle size, which is the particle size accumulated at 90% of the volume basis obtained in the same way as "D50". "A unit based on a monomer" refers to a group of atoms formed by the polymerization of monomers, with the aforementioned monomer as the main component. A unit can be formed directly through a polymerization reaction, or it can be a unit whose structure is transformed by processing the polymer. Hereinafter, a unit based on monomer a will be simply referred to as "monomer a unit".

[0011] The method for manufacturing the sheet of the present invention (hereinafter also referred to as "the method") involves mixing an aggregate with particles (hereinafter also referred to as "F particles") containing a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer"), and then forming the resulting mixture into a sheet; the aggregate contains particles containing polytetrafluoroethylene (hereinafter also referred to as "PTFE") and inorganic particles, the tetrafluoroethylene-based polymer having oxygen-containing polar groups and a melting temperature of 320°C or less.

[0012] PTFE is a polymer with low surface tension and extremely low affinity for other components. Therefore, even when PTFE is mixed with inorganic particles, the dispersibility of the inorganic particles with PTFE remains low. However, we believe that pre-forming PTFE-containing particles and inorganic particles into an aggregate, and then mixing the aggregate with F particles, thereby allowing the F polymer to act as a binder or adhesive component between PTFE and inorganic particles, can improve the uniform dispersion of inorganic particles in the resulting sheet, suppress inorganic particle powdering, and thus exhibit low-temperature adhesion.

[0013] The PTFE in this invention can be a homopolymer of TFE, or a copolymer of TFE with trace amounts of perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"), hexafluoropropylene (hereinafter also referred to as "HFP"), fluoroalkyl vinyl ether, etc., i.e., the so-called modified PTFE. The ratio of TFE units in the PTFE should preferably be 99.5 mol% or more in the total units, and more preferably 99.9 mol% or more.

[0014] PTFE should be PTFE with a number average molecular weight (Mn) of 200,000 or more, calculated according to the following formula (1). Mn=2.1×1010×ΔHc-5.16・・・(1) In formula (1), Mn represents the number average molecular weight of PTFE, and ΔHc represents the heat of crystallization (cal / g) of PTFE determined by differential scanning calorimetry.

[0015] The D50 of PTFE-containing particles should preferably be 0.1µm or higher, and more preferably 0.2µm or higher. The D50 should preferably be 3µm or lower, and more preferably 0.5µm or lower.

[0016] The inorganic particles of the present invention are preferably spherical, scaly, layered, needle-like, or plate-like, more preferably spherical, scaly, or layered, and even more preferably spherical or scaly. Spherical inorganic particles are preferably substantially true spherical. "Substantially true spherical" means that when observing the inorganic particles using a scanning electron microscope (SEM), the ratio of the minor axis to the major axis is 0.7 or more. The proportion of substantially true spherical inorganic particles is preferably 95% or more. The aspect ratio of non-spherical inorganic particles is preferably 2 or more, and preferably 5 or more. The aspect ratio is preferably 10000 or less.

[0017] The inorganic particles may also be hollow. In this case, the sheet obtained by this method (hereinafter also referred to as "this sheet") tends to have excellent electrical properties. The inorganic particles are particles containing at least one inorganic substance, preferably particles containing at least one substance selected from the group consisting of metal oxides, silicon oxides, and nitrides. Specific examples of inorganic substances include: carbon, boron nitride, aluminum nitride, beryllium oxide, silicon dioxide, silash, talc, cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, barium titanate, lead zirconate titanate, lead titanate, zirconium oxide, and titanium oxide. From the viewpoint of reducing the dielectric constant and dielectric tangent of this sheet and improving low linear expansion, the inorganic particles are preferably particles containing silicon dioxide or boron nitride. Silicon dioxide is preferably amorphous silicon dioxide. Boron nitride is preferably hexagonal boron nitride. Furthermore, from the perspective of improving the dielectric constant, inorganic particles should preferably be particles containing titanium dioxide or barium titanate.

[0018] When the inorganic particles contain silicon dioxide, from the viewpoint of electrical properties, hollow silicon dioxide is preferable. When the inorganic particles contain nitrides, from the viewpoint of the electrical properties and low linear expansion of this sheet, boron nitride or aluminum nitride is preferable, with flake-shaped boron nitride or columnar aluminum nitride being more suitable. Flake-shaped boron nitride can also agglomerate to form secondary particles.

[0019] The D50 of the inorganic particles is preferably below 20µm, more preferably below 10µm. The D50 is preferably above 0.01µm, more preferably above 0.1µm, more preferably above 1µm, and especially preferably above 2µm. The specific surface area of ​​the inorganic particles is preferably 1 to 20 m² / g. Inorganic particles with a D50 of 1 to 20µm and a specific surface area of ​​1 to 20 m² / g will form interparticle channels in the sheet, which can easily improve the sheet's physical properties such as thermal conductivity, low linear expansion, and electrical properties. However, on the other hand, their interaction with PTFE-containing particles is low, and they tend to detach from the sheet more easily. However, in this invention, this phenomenon can be highly suppressed by the action of the F polymer.

[0020] The surface of the inorganic particles can also be surface-treated with a silane coupling agent. This increases the affinity between the inorganic particles and PTFE and F polymers, making it easier for the inorganic particles to disperse uniformly within the sheet, and preventing them from easily peeling off. Furthermore, the sheet tends to possess excellent electrical properties and low linear expansion. The silane coupling agent is preferably a functionalized silane coupling agent such as 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, or 3-isocyanatepropyltriethoxysilane.

[0021] Specific examples of particles containing silicon dioxide include: the "Admafine" series (manufactured by Admatechs), the "SFP" series (manufactured by Denka), the "E-SPHERES" series (manufactured by Pacific Cement), the "SiliNax" series (manufactured by Nippon Steel Mining Co., Ltd.), the "Eccosphere" series (manufactured by Emerson & Cuming), and the "hydrophobic AEROSIL" series ("RX200", etc.) (manufactured by AEROSIL Corporation of Japan). Specific examples of particles containing zinc oxide include the "FINEX" series (manufactured by Sakai Chemical Industry Co., Ltd.). Specific examples of particles containing titanium oxide include the "TIPAQUE" series (manufactured by Ishihara Sangyo Co., Ltd.) and the "JMT" series (manufactured by Tayca Co., Ltd.). Specific examples of particles containing talc include the "SG" series (manufactured by Nippon Talc). Specific examples of particles containing block talc include the "BST" series (manufactured by Nippon Talc). Specific examples of particles containing boron nitride include the "UHP" series (manufactured by Showa Denko) and the "GP" and "HGP" grades of the "Denka Boron Nitride" series (manufactured by Denka).

[0022] One type of inorganic particle may be used, or two or more types may be used. For example, silicon dioxide particles, boron nitride particles, and titanium dioxide particles may be used together as inorganic particles. In this case, the content of silicon dioxide particles, boron nitride particles, and titanium dioxide particles in the total amount of inorganic particles should preferably be 10 to 60% by mass, 10 to 60% by mass, and 5 to 40% by mass, respectively.

[0023] Aggregates containing PTFE-containing particles and inorganic particles can be obtained, for example, by the following method. First, inorganic particles are added to a PTFE-containing particle dispersion, or the PTFE-containing particles and inorganic particles are pre-mixed and then dispersed in a dispersion medium to obtain a mixture containing PTFE-containing particles, inorganic particles, and a dispersion medium. The dispersion medium used is preferably water. The PTFE-containing particle dispersion can be a commercially available aqueous dispersion of PTFE-containing particles, or it can be a dispersion further diluted with water. The aforementioned mixture may also contain a surfactant. The concentration of solid components in the resulting mixture is, for example, 3 to 50% by mass. Furthermore, when the mixture contains water, the content of PTFE-containing particles is, for example, 0.5 to 20% by mass, and the content of inorganic particles is, for example, 10 to 30% by mass.

[0024] Mixing devices used for mixing can be listed as: Heinz mixers, pressure kneaders, Bambury closed mixers and planetary mixers, etc., which are stirring devices with paddles; ball mills, grinding mills, basket mills, sand mixers, sand mills, Dyno-Mills, DISPERMATs, SC-Mills, spiked mills or stirred mills, etc., which are grinding devices with media; microfluidic homogenizers, nanomizers, ultra-thinners, ultrasonic homogenizers, dissolvers, dispersers, high-speed impeller dispersers, self-rotating and revolution-rotating mixers or thin-film rotary high-speed mixers, etc., which are dispersion devices with other mechanisms.

[0025] The aforementioned mixture may contain only PTFE-containing particles and inorganic particles, or it may contain other fluoropolymers besides PTFE. Examples of other fluoropolymers include: polymers other than the polymer described below, such as ETTE (containing TFE units and ethylene-based units), TFEP (containing TFE units and propylene-based units), PFA (containing TFE units and perfluoro(alkyl vinyl ether) (PAVE)-based units), and FEP (containing TFE units and hexafluoropropylene-based units). Fluoropolymers with good miscibility with PTFE are preferred. When the mixture contains PTFE and other fluoropolymers as fluoropolymer components, the PTFE content should preferably be 5% by weight or more, and more preferably 10% by weight or more, relative to the total fluoropolymer component.

[0026] By removing the dispersion medium from the aforementioned mixture, an aggregate containing PTFE-containing particles and inorganic particles can be obtained. Methods for obtaining the aggregate include, for example, freeze-drying; spray drying; a method of applying shear to a stirred mixture to agglomerate the PTFE-containing particles and inorganic particles and remove the dispersion medium; and a method of agglomerating the PTFE-containing particles and inorganic particles in a mixture and removing the dispersion medium. Among these methods, a co-agglomeration method is particularly suitable, where the PTFE-containing particles and inorganic particles are agglomerated in a mixture containing PTFE-containing particles, inorganic particles, and water. In other words, the aggregate is preferably an aggregate obtained by co-agglomeration from a mixture containing PTFE-containing particles, inorganic particles, and water.

[0027] Co-agglomeration can be achieved by adding a coagulant to the aforementioned mixture. The coagulant can be a solvent such as an alcohol or a material with a large specific surface area, such as activated carbon. Furthermore, when the mixture contains interfacial surfactants, raising the temperature of the mixture can deactivate the surfactants and promote co-agglomeration.

[0028] Co-agglomerates can be obtained by separating the coagulated material from the dispersion medium. The obtained co-agglomerates can also be further dried. The separation method for separating the coagulated material from the dispersion medium can utilize known methods such as filtration. There are no particular limitations on the drying method.

[0029] The content of inorganic particles in the aggregate is appropriately set according to the physical properties required by the sheet material. When the total mass of the aforementioned PTFE-containing particles and the aforementioned inorganic particles is 100% by mass, the content of PTFE-containing particles should be 5% by mass or more and 60% by mass or less, and the content of inorganic particles should be 40% by mass or more and 95% by mass or less. More preferably, the content of PTFE-containing particles should be 20% by mass or more and 50% by mass or less, and the content of inorganic particles should be 60% by mass or more and 80% by mass or less.

[0030] Alternatively, the aforementioned mixture can be made to agglomerate the aforementioned PTFE-containing particles and the aforementioned inorganic particles, and the resulting agglomerate can be separated from the dispersion medium to obtain agglomerate. The obtained agglomerate can then be mixed with the dispersion medium again to form a mixture, and agglomerate it again to form agglomerate.

[0031] In this method, the aforementioned aggregate is mixed with F particles containing F polymer. The melting temperature of the F polymer is below 320°C, preferably above 200°C, and more preferably above 260°C.

[0032] The glass transition point of the F polymer is preferably above 50°C, and more preferably above 75°C. The glass transition degree of the F polymer is preferably below 150°C, and more preferably below 125°C. The fluorine content of the F polymer is preferably above 70% by mass, and more preferably 72 to 76% by mass. The surface tension of the F polymer is preferably 16 to 26 mN / m. In addition, the surface tension of the F polymer can be measured by placing a droplet of the wetting index reagent (manufactured by Wako Pure Chemical Corporation) on a plate made of the F polymer. F polymers with high fluorine content have excellent electrical and physical properties, but the low surface tension makes adhesion easy to decrease. However, because the F polymer contains oxygen-containing polar groups, it can easily function as a binder or adhesive component between PTFE and inorganic particles.

[0033] Polymer F is preferably ETTE, TFEP, PFA, or FEP, more preferably PFA and FEP, and even more preferably PFA. These polymers may also contain units mainly composed of other comonomers. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, and CF2=CFOCF2CF2CF3 (hereinafter also denoted as "PPVE"), and more preferably PPVE.

[0034] The oxygen-containing polar groups in polymer F can be hydroxyl-containing groups or carbonyl-containing groups. From the viewpoint of improving adhesion, the oxygen-containing polar groups are preferably carbonyl-containing groups. The hydroxyl-containing groups are preferably groups containing alcoholic hydroxyl groups, and are more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl-containing groups are preferably carboxyl groups, alkoxycarbonyl groups, amide groups, isocyanate groups, carbamate groups (-OC(O)NH2), acid anhydride residues (-C(O)OC(O)-), amide imine residues (-C(O)NHC(O)-, etc.) and carbonate groups (-OC(O)O-), and are more preferably acid anhydride residues. The number of oxygen-containing polar groups in polymer F, based on the number of carbon atoms in the main chain, is preferably 10 to 5000 per 1×106 carbon atoms in the main chain, and is more preferably 100 to 3000. Furthermore, the number of oxygen-containing polar radicals in polymer F can be quantified by means of the polymer composition or by the methods described in International Publication No. 2020 / 145133.

[0035] The oxygen-containing polar group may be contained in the monomer-dominated unit of the F polymer, or it may be contained in the terminal group of the main chain of the F polymer, preferably the former. Examples of the latter include: F polymers having oxygen-containing polar groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., and F polymers obtained by plasma treatment or ionizing radiation treatment of F polymers. The monomers containing carbonyl groups are preferably itanic anhydride, citric anhydride, and 5-norphene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and NAH is more preferred. The F polymer is preferably a polymer containing carbonyl groups that includes TFE units and PAVE units, and is more preferably a polymer that includes TFE units, PAVE units, and units mainly composed of monomers containing carbonyl groups, and contains these units in the following order relative to the total units: 90 to 99%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%. Specific examples of the F polymer can be found in the polymer described in International Publication No. 2018 / 16644.

[0036] The D50 of F particles should preferably be greater than 0.1µm, more preferably greater than 0.3µm, and even more preferably greater than 1µm. The D50 of F particles should preferably be less than 25µm, more preferably less than 10µm, and even more preferably less than 8µm. The specific surface area of ​​F particles should preferably be 1 to 25 m² / g. One type of F particles may be used, or two or more types may be used.

[0037] The F particles are particles containing F polymers and are preferably composed of F polymers. The F particles may contain resins or inorganic compounds other than F polymers, and may form a core-shell structure with an F polymer as the core and a resin or inorganic compound other than F polymers as the shell, or may form a core-shell structure with an F polymer as the shell and a resin or inorganic compound other than F polymers as the core.

[0038] Examples of resins other than F polymers include aromatic polyesters, polyamide imides, polyimides, and maleimides. Examples of inorganic compounds include inorganic substances that are the same as or may be included in the aforementioned inorganic particles, among which silicon dioxide and boron nitride are preferred.

[0039] In this method, the aforementioned agglomerate and the aforementioned F particles are mixed to obtain a mixture. Methods for mixing the agglomerate and F particles include: mixing the aforementioned agglomerate and the aforementioned F particles; dispersing the F particles in a dispersion medium such as water or an organic solvent to prepare a dispersion, and then mixing the dispersion with the agglomerate; dispersing the agglomerate in a dispersion medium such as water or an organic solvent to prepare a dispersion, and then mixing it with a dispersion of F particles; dispersing the agglomerate in a dispersion medium such as water or an organic solvent to prepare a dispersion, and then mixing the dispersion with the F particles. The mixing can be performed using a mixer similar to those described above.

[0040] From the viewpoint of the uniform dispersion of inorganic particles in the sheet, the following methods are preferable: methods of mixing aggregates and F particles; methods of dispersing F particles in a dispersion medium such as water or an organic solvent to form a dispersion, and then mixing the dispersion with the aggregates. When mixing aggregates and F particles, it is preferable to mix them in the powder state of the aggregates of F particles in a dry state.

[0041] When mixing the dispersion and aggregates of F particles, from the viewpoint of improving the dispersion stability of the dispersion, the dispersion medium should preferably be a compound selected from the group consisting of water, amides, ketones and esters, with water being more suitable. Alternatively, it should also be an alkyl group such as decane or dodecane, which will be used as a forming aid in the later process of forming sheets. Examples of amides include: N-methyl-2-pyrrolidone, N,N-dimethylmethoxymethylenediamine, N,N-dimethylacetylamine, N,N-dimethylpropionic acid, 3-methoxy-N,N-dimethylpropionic acid, 3-butoxy-N,N-dimethylpropionic acid, N,N-diethylmethoxymethylenediamine, trimethylammonium hexamethylphosphate, and 1,3-dimethyl-2-imidazolidinedione.

[0042] Ketones include: acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, cycloheptanone. Esters include: methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, γ-valerolactone.

[0043] The content of the aforementioned dispersion medium in the dispersion of F particles should preferably be 40% by mass or more, and more preferably 60% by mass or more. The content of the liquid dispersion medium should preferably be 90% by mass or less, and more preferably 80% by mass or less. The content of F particles in the dispersion of F particles should preferably be 10% by mass or more, and more preferably 20% by mass or more. The content of F particles should preferably be 60% by mass or less, and more preferably 40% by mass or less.

[0044] When the dispersion medium of the F particle dispersion is water, the pH of the F particle dispersion should preferably be between 5 and 10, more preferably between 8 and 10. To adjust the pH of the dispersion, a pH adjuster or a pH buffer may also be included. Examples of pH adjusters include amines, ammonia, and citric acid. Examples of pH buffers include: trimethylolamine methane, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate, and ammonium acetate.

[0045] The dispersion of F particles may also contain a nonionic surfactant. The nonionic surfactant is preferably an ethylene glycol-based surfactant, an acetylene-based surfactant, a polysiloxane-based surfactant, or a fluorine-based surfactant, with a preference for polysiloxane-based surfactants. One or more nonionic surfactants may be used. When using two nonionic surfactants, a polysiloxane-based surfactant and an ethylene glycol-based surfactant are preferred.

[0046] Specific examples of nonionic surfactants include: "Ftergent" series (manufactured by NEOS), "Surflon" series (manufactured by AGC SEIMI CHEMICAL), "MEGAFACE" series (manufactured by DIC), "UNIDYNE" series (manufactured by Daikin Industries), "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", "BYK-3456" (manufactured by BYK Japan), "KF-6011", "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.), and "Tergitol" series (manufactured by Dow Chemical Company, "Tergitol TMN-100X", etc.). When the dispersion contains a nonionic surfactant, the content of the nonionic surfactant in the dispersion should preferably be 1 to 15% by mass.

[0047] From the viewpoint of suppressing powder shedding of the sheet, when the PTFE contained in the agglomerate is 100 parts by mass, the F polymer should preferably be 5 parts by mass or more and 30 parts by mass or less, more preferably 10 parts by mass or more and 30 parts by mass or less, and even more preferably 15 parts by mass or more and 25 parts by mass or less.

[0048] The aforementioned mixture may also contain the aforementioned PTFE and resins different from polymer F (hereinafter referred to as "dissimilar resins") or inorganic particles different from the inorganic particles contained in the aggregates (hereinafter referred to as "dissimilar inorganic particles"). Dissimilar resins may be thermosetting or thermoplastic, preferably thermoplastic. Examples of dissimilar resins include: liquid crystal aromatic polyesters, polyester resins such as polyarylate resins, amide resins, amide resins, epoxy resins, maleimide resins, carbamate resins, polyphenylene ether resins, polyoxyphenylene oxide resins, polyphenylene sulfide resins, polyolefin resins, polycarbonate resins, and polyacetal resins.

[0049] Among these, aromatic polymers are preferred, and more preferably, aromatic amide polymers selected from the group consisting of aromatic polyimides, aromatic polyamides, aromatic polyamides and precursors of aromatic polyamides. In this case, the polymer layer readily exhibits excellent adhesion, low linear expansion, or UV processability. Specific examples of aromatic amide polymers include: the "UPIA-AT" series (manufactured by Ube Industries, Inc.), the "Neopulim" series (manufactured by MITSUBISHI GAS CHEMICAL), the "SPIXAREA" series (manufactured by SOMAR), the "Q-PILON" series (manufactured by PI Technology Research Institute), the "WINGO" series (manufactured by Wingo Technology), the "Tohmide" series (manufactured by T&K TOKA), the "KPI-MX" series (manufactured by Kawamura Industries, Inc.), "HPC-1000," and "HPC-2100D" (both manufactured by SHOWA DENKO MATERIALS). When the mixture contains dissimilar resins, the content of the dissimilar resins in the mixture should preferably be 0.1% to 40% by mass, more preferably 1% to 10% by mass.

[0050] Different inorganic particles may be the same as those used to obtain the aforementioned aggregates. When the aforementioned mixture contains inorganic particles, the content of inorganic particles in the mixture is preferably 1 to 50% by mass, more preferably 3 to 30% by mass.

[0051] The aforementioned mixture may also contain particles of PTFE that are different from those contained in the aggregate. In addition to the aforementioned components, the aforementioned mixture may also contain, as needed, additives such as plasticizers, weather resistant agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents, mold release agents, surface treatment agents, flame retardants, and various fillers.

[0052] In this method, a sheet is formed from the aforementioned mixture. Forming methods include casting the mixture. By casting, PTFE easily fibrils, resulting in a sheet material where inorganic particles are less likely to peel off. Furthermore, a sheet material with excellent electrical properties and toughness is easily obtained. Casting methods include pressing, extrusion, or calendering. Calendering refers to a method in which the mixture is rolled between multiple rollers.

[0053] The aforementioned mixture containing the dispersion medium can also be molded after the dispersion medium is removed. Alternatively, an agglomerate can be obtained from the aforementioned mixture containing the dispersion medium by further agglomerating the F particles into an agglomerate containing PTFE-containing particles and inorganic particles, and this agglomerate can be used for molding. The method for obtaining the agglomerate can be the same as the aforementioned method for obtaining the agglomerate containing PTFE-containing particles and inorganic particles.

[0054] Alternatively, the aforementioned mixture can be mixed with the molding aid before molding to form a paste mixture and then cast. Mixing with the molding aid should be carried out under conditions that strongly suppress PTFE fibrillation. Specifically, to avoid applying shear force to the PTFE, the rotation speed should be reduced and the mixing time shortened, and mixing should be performed without kneading. If PTFE fibrillation occurs during the material mixing stage, the PTFE fibers formed during casting will be cut, potentially damaging the PTFE mesh structure and making it difficult to maintain the sheet shape. Therefore, suppressing PTFE fibrillation through mixing facilitates the processing of the sheet material into a matrix for subsequent PTFE steps. Molding aids, for example, can be alkyl groups such as dodecane or decane. The molding aid can be added in a manner that is 20 to 55% by mass relative to the total mass.

[0055] The casting of the mixture can be performed using one forming method or by combining two or more forming methods. Furthermore, the casting process can be repeated multiple times using one forming method. For example, the master sheet obtained after extruding the mixture can be further calendered and cast, or the master sheet obtained after calendering the mixture can be further calendered and cast. In this case, a sheet of any thickness with excellent toughness and uniformity can be easily obtained. Multiple calendering rollers can be used, preferably in combination of four. The arrangement of the four rollers can be I-type, S-type, reverse L-type, Z-type, or oblique Z-type.

[0056] The casting of the mixture can be carried out simultaneously with heating at a temperature below the melting temperature of PTFE, or it can be carried out without heating. When a molding aid is used during the forming of this sheet, heating can also be performed after casting to remove the molding aid. This sheet can be obtained in the above manner. The thickness of this sheet is, for example, 0.5 to 5 mm. This sheet can also be heated and fired at a temperature above or below the melting temperature of PTFE.

[0057] Furthermore, as mentioned above, inorganic particles with a D50 of 1 to 20 µm and a specific surface area of ​​1 to 20 m² / g can form interparticle channels in the sheet, which can easily improve sheet properties such as thermal conductivity, low linear expansion, and electrical properties. However, on the other hand, their interaction with PTFE-containing particles is low, and they tend to detach from the sheet more easily. However, by allowing the aforementioned F polymer to coexist with the aforementioned inorganic particles, even for particles that are more prone to dusting, dusting can be suppressed to a greater extent.

[0058] Therefore, the present invention further provides a sheet material (hereinafter also referred to as "other sheets material") comprising PTFE, F polymer, and inorganic particles, wherein the average particle size of the inorganic particles is 1 to 20 µm and the specific surface area is 1 to 20 m² / g; and, when the total mass of the aforementioned PTFE and the aforementioned inorganic particles is 100% by mass, the contents of the aforementioned PTFE and the aforementioned inorganic particles are 5% by mass or more and 60% by mass or less, and 40% by mass or more and 95% by mass or less, respectively. PTFE and F polymer are as described above, and their ideal morphology is also the same as described above. In other sheets material, when the total mass of the aforementioned PTFE and the aforementioned inorganic particles is 100% by mass, the content of PTFE is preferably 20% by mass or more and 50% by mass or less. Furthermore, in other sheets material, when the total mass of the aforementioned PTFE and the aforementioned inorganic particles is 100% by mass, the content of inorganic particles is preferably 60% by mass or more and 80% by mass or less.

[0059] Other components of this sheet material shall preferably contain 5 parts by mass and 30 parts by mass of the aforementioned F polymer relative to 100 parts by mass of the aforementioned PTFE, more preferably 10 parts by mass and 30 parts by mass, and even more preferably 15 parts by mass and 25 parts by mass. Furthermore, the inorganic particles, as described above, shall preferably include at least one selected from the group consisting of metal oxides, silicon oxides, and nitrides.

[0060] Other sheets may be manufactured by the aforementioned method. In the manufacture of other sheets, the ideal form is the same as that of the aforementioned method.

[0061] Laminated sheets can be obtained by stacking two or more sheets of the above-mentioned sheet material or other sheet materials. Laminated sheets can be obtained by stacking two or more sheets of the sheet material and rolling them. The number of layers in a laminated sheet is, for example, about 2 to 10 layers. From the point of view of the strength between the layers, it is advisable to stack and roll the sheet material one by one.

[0062] This sheet or other sheets can also be folded and laminated. By folding and rolling this sheet or other sheets, the sheet strength can be increased, and the inorganic particles can be firmly fixed into the PTFE matrix. As a result, laminated sheets with a high ratio of inorganic particles and high flexibility can be produced. Multiple sheets of the aforementioned laminated sheets can also be stacked to further produce laminated sheets with a high number of layers.

[0063] When manufacturing laminated sheets, it is advisable to change the rolling direction. For example, when rolling a second sheet onto a first sheet and then laminating a third sheet, it is advisable to change the rolling direction by 90 degrees from the rolling direction of the second sheet. By changing the direction while rolling, the PTFE network will extend longitudinally and laterally, thereby increasing the strength of the sheet and firmly fixing the inorganic particles into the PTFE matrix. The resulting laminated sheet can also be press-formed. By press-forming, the porosity in the laminated sheet can be reduced.

[0064] If the aforementioned laminated sheet is hot-pressed with a substrate, a laminate having a substrate layer and a polymer layer containing PTFE, inorganic particles and F polymer can be obtained.

[0065] Examples of substrates include: metal substrates such as metal foils of copper, nickel, aluminum, titanium, and their alloys; heat-resistant resin films of heat-resistant resin films such as polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyaryl ether ketone, polyamide-imide, liquid crystal polyester, and tetrafluoroethylene polymers; prepreg substrates of precursors for fiber-reinforced resin substrates; ceramic substrates such as silicon carbide, aluminum nitride, or silicon nitride; and glass substrates. The shape of the substrate can be planar, curved, or uneven. Furthermore, the shape of the substrate can also be any of foil, plate, film, or fibrous. The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 µm.

[0066] The surface of the substrate may be surface-treated with a silane coupling agent or by plasma treatment. The silane coupling agent is preferably a functionalized silane coupling agent such as 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, or 3-isocyanatepropyltriethoxysilane.

[0067] Hot pressing methods include: applying clamping pressure to the substrate and the sheet using a pair of opposing heating plates; passing the substrate and the sheet between a pair of opposing rollers; and applying pressure to the substrate and the sheet using rollers on heating plates. The hot pressing temperature should preferably be above 200°C, more preferably above the melting temperature of PTFE, and even more preferably above 350°C. The hot pressing temperature should preferably be below 400°C. PTFE should preferably be fired by heating during hot pressing.

[0068] Hot pressing can also be performed under reduced pressure. In this case, from the viewpoint of suppressing the deterioration caused by oxidation of the substrate and the sheet, it is advisable to perform the hot pressing under a vacuum of 20 kPa or less. Hot pressing is preferably performed under vacuum. During hot pressing, from the viewpoint of suppressing the sheet from adhering to the heating plate or rollers, it is advisable to place a release film between the surface of the sheet and the heating plate or rollers, or to surface treat the surface of the heating plate or rollers with a release agent.

[0069] The thickness of the release film should be 50 to 150 µm. Examples of release films include polyimide films, such as APICAL NPI (manufactured by Kaneka Co.), KAPTON EN (DU PONT-TORAY CO.,LTD.), and UPILEX S (Ube Industries Co., Ltd.).

[0070] This laminated sheet can be heat-pressed to only one surface of the substrate, or it can be heat-pressed to both sides of the substrate. In the former case, a laminate having a substrate layer and a polymer layer located on one surface of the substrate layer can be obtained; in the latter case, a laminate having a substrate layer and polymer layers located on both surfaces of the substrate layer can be obtained. Ideal examples of the laminate include: a metal-clad laminate having a metal foil and a polymer layer located on at least one surface of the metal foil, and a multilayer film having a polyimide film and polymer layers located on both surfaces of the polyimide film. The peel strength between the polymer layer and the substrate layer is preferably 10 to 100 N / cm. The substrate layer can also be further removed from the laminate to obtain a sheet containing PTFE, inorganic particles, and F polymer.

[0071] This sheet, this laminated sheet, and laminates having this laminated sheet can be effectively used as antenna parts, printed circuit boards, aircraft parts, automotive parts, sporting goods, food industry products, heat dissipation parts, coatings, cosmetics, etc. Specifically, it can be effectively used as: wire sheathing material for aircraft wires, enameled wire sheathing material for motors used in electric vehicles, electrical insulating tape, oil drilling insulating tape, oil delivery hoses, hydrogen tanks, materials for printed circuit boards, separation membranes such as microporous filter membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, and gas separation membranes, electrode adhesives for lithium batteries and fuel cells, copy rolls, housings for furniture, automotive dashboards, and home appliances, sliding components, tension cables, wear-resistant pads, wear-resistant strips, lamps, test sockets, and wafer guides. (guide) Wear parts of centrifugal pumps, chemical pumps and water pumps, tools such as shovels, files, cones and saws, boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, molds, toilets, container coverings, power devices, transistors, thyristors, rectifiers, transformers, power MOSFETs, CPUs, heat sinks, metal heat sinks, windmills or wind power generation equipment or aircraft blades, computer or monitor housings, electronic device materials, automotive interior and exterior parts, processing machines or vacuum ovens that undergo heat treatment in low oxygen conditions, sealing materials for plasma treatment equipment, heat dissipation parts in sputtering or various dry etching equipment, electromagnetic wave shielding components. Sliding components include: load bearings, yaw bearings, sliding shafts, valves, bearings, bushings, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, conveyor belts, food conveyor belts, etc.

[0072] The manufacturing methods of the sheet material and laminated sheets, as well as other sheets, have been described above. However, the present invention is not limited to the configuration of the above embodiments. For example, the manufacturing methods of the sheet material and laminated sheets may include any additional steps in the configuration of the above embodiments, or may be replaced with any step that can produce the same effect. Other sheets may include any additional configuration in the configuration of the above embodiments, or may be replaced with any configuration that can perform the same function.

[0073] Examples Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. 1. Preparation of each component [particles] PTFE particles: PTFE particles (D50: 0.3µm) F particles 1: F polymer 1 (melting temperature: 300°C) particles (D50: 1.7µm), which contain TFE units, NAH units and PPVE units in sequence at 97.9 mol%, 0.1 mol%, and 2.0 mol%, and have 1000 carbonyl groups per 1×106 main chain carbons F particles 2: F polymer 2 (melting temperature: 300°C) particles (D50: 2.1µm) without oxygen-containing polar groups, which contain TFE units and PPVE units in sequence at 97.5 mol% and 2.5 mol%.

[0074] [Dispersion] Dispersion 1: An aqueous dispersion containing 60% by mass of PTFE particles. [Inorganic Particles] Inorganic Particle 1: Flake-like boron nitride particles (D50: 7.0µm, specific surface area: 2m² / g) Inorganic Particle 2: Spherical silicon dioxide particles (D50: 2.0µm, specific surface area: 5m² / g)

[0075] 2. Manufacturing of sheets, laminated sheets and laminates (Example 1) Dispersion 1 is diluted 20 times with water, and inorganic particles 1 are added to the resulting diluted dispersion in such a way that the mass ratio of inorganic particles 1 to PTFE particles is 80:20. A mixture containing PTFE particles 1 and inorganic particles 1 is thus obtained. Isopropanol is added to the mixture to cause the PTFE particles and inorganic particles 1 to co-aggregate in the mixture. The resulting agglomerates are filtered to separate them from the liquid components and dried at 150°C for 24 hours to obtain an agglomerate containing PTFE particles and inorganic particles 1.

[0076] The aggregate, 10 parts by mass of F particles 1 relative to 100 parts by mass of PTFE particles, and Isopar M (manufactured by Exxon Mobil Corporation) molding aid were mixed in such a way that the total mass ratio of PTFE particles, inorganic particles 1 and F particles 1 to the mass ratio of molding aid was 5:2, and the mixture was mixed for 10 minutes using a rotary mill under conditions that would not induce PTFE fiberization.

[0077] The obtained mixture is pre-formed and pelletized. The pellets are extruded using an extruder to obtain a master sheet with a width of 45 mm and a thickness of 2 mm. The master sheet is rolled in the MD direction (long side direction) using a pair of rolling rolls to obtain a sheet 1 with a thickness of 1 mm. After aligning the MD and TD directions of the two sheets 1, they are laminated using a roll-to-roll process and rolled in the TD direction to obtain a laminated sheet 1 with a thickness of 0.25 mm. In addition, no powder is shed during sheet production. The contents of PTFE, inorganic particles 1, and F polymer 1 in each sheet are 20% by mass, 78% by mass, and 2% by mass, respectively. When the total mass of PTFE and inorganic particles 1 is 100% by mass, the sheet contains 25% by mass of PTFE, 75% by mass of inorganic particles 1, and 10 parts by mass of F polymer 1 relative to 100 parts by mass of PTFE.

[0078] The laminated sheet 1 is overlapped with an unroughened copper foil (the average roughness of the surface at ten points is less than 0.05µm and the thickness is 18µm), and then hot-pressed at 380°C to bond them together, thereby obtaining a laminate 1 having a polymer layer composed of the laminated sheet and a copper foil.

[0079] (Example 2) Except that F particles 1 were not added in Example 1, the laminated sheet 2 and the laminate 2 were obtained in the same manner. In addition, it was confirmed that during the fabrication of the laminated sheet 2, powder shedding caused streaks on the sheet and contamination of the device. Furthermore, the peel strength between the copper foil in each laminate and the laminated sheet was measured. The results showed that the peel strength of laminate 1 was greater than 10 N / cm, and the peel strength of laminate 2 was less than 10 N / cm.

[0080] (Example 3) Dispersion 1 was diluted 20 times with water, and inorganic particles 2 were added to the resulting diluted dispersion in such a way that the mass ratio of inorganic particles 2 to PTFE particles was 60:40. This yielded a mixture containing PTFE particles and inorganic particles 2. Isopropanol was added to the mixture to cause the PTFE particles and inorganic particles 2 to co-aggregate. The resulting agglomerates were filtered to separate them from the liquid components and dried at 150°C for 24 hours to obtain agglomerates containing PTFE particles and inorganic particles 2.

[0081] The aggregate, 8 parts by mass of F particles 1 relative to 100 parts by mass of PTFE particles, and Isopar M (manufactured by Exxon Mobil Corporation) of molding aid are mixed in such a way that the total mass ratio of PTFE particles, inorganic particles 2 and F particles 2 to the mass ratio of molding aid is 5:2, and the mixture is mixed for 10 minutes using a rotary mill under conditions that do not induce PTFE fiberization.

[0082] The obtained mixture is pre-formed and pelletized. The pellets are extruded using an extruder to obtain a master sheet with a width of 45 mm and a thickness of 2 mm. The master sheet is rolled in the MD direction (long side direction) using a pair of rolling rolls to obtain a sheet 3 with a thickness of 1 mm. After aligning the MD and TD directions of the two sheets 3, they are laminated using a roll-to-roll process and rolled in the TD direction to obtain a laminated sheet 3 with a thickness of 0.25 mm. In addition, no powder is shed during sheet production. The contents of PTFE, inorganic particles 2, and F polymer 1 in each sheet are 39% by mass, 59% by mass, and 2% by mass, respectively. When the total mass of PTFE and inorganic particles 2 is 100% by mass, each sheet contains 40% by mass of PTFE, 60% by mass of inorganic particles 2, and 5 parts by mass of F polymer 1 relative to 100 parts by mass of PTFE. The laminated sheet 3 series is an adhesive sheet with low relative permittivity and dielectric tangent, low linear expansion, and excellent surface smoothness that suppresses powder shedding during use.

[0083] (Example 4) In addition to changing F polymer 1 to F polymer 2, the master sheet 4 and the laminated sheet 4 were attempted to be formed in the same manner as in Example 3. However, the sheet was powdered during the sheet making process, which not only failed to form a sheet with excellent surface smoothness, but also caused powder to fall off during use.

[0084] As can be clearly seen from the above results, the inorganic particles in the sheets and laminated sheets obtained by this method are uniformly dispersed, and the shedding of inorganic particles is suppressed, and the low-temperature adhesion is excellent. Furthermore, the sheets, laminated sheets and laminates obtained by this method fully possess the original characteristics of polytetrafluoroethylene and inorganic particles.

Claims

1. A method for manufacturing a sheet, comprising mixing an aggregate with particles of a tetrafluoroethylene-based polymer, and then molding the resulting mixture; the aggregate contains particles containing polytetrafluoroethylene and inorganic particles, the tetrafluoroethylene-based polymer having an oxygen-containing polar group and a melting temperature of 320°C or less; when the total mass of the aforementioned polytetrafluoroethylene-based particles and the aforementioned inorganic particles is 100% by mass, the content of the aforementioned polytetrafluoroethylene-based particles and the aforementioned inorganic particles in the aforementioned aggregate is as follows: the aforementioned polytetrafluoroethylene-based particles are 5% by mass or more and 60% by mass or less, and the aforementioned inorganic particles are 40% by mass or more and 95% by mass or less; the manufacturing method involves mixing 5% by mass or more and 30% by mass or less of the aforementioned tetrafluoroethylene-based polymer particles with 100 parts by mass of the aforementioned polytetrafluoroethylene.

2. The manufacturing method of claim 1, wherein the aforementioned aggregate is an aggregate obtained by co-aggregation of a mixture containing the aforementioned polytetrafluoroethylene particles, the aforementioned inorganic particles, and water.

3. The manufacturing method of claim 1, wherein the aforementioned inorganic particles comprise at least one selected from the group consisting of metal oxides, silicon oxides and nitrides.

4. The manufacturing method of claim 1, wherein the average particle size of the aforementioned inorganic particles is 1 to 20 µm and the specific surface area is 1 to 20 m² / g.

5. The manufacturing method of claim 1, wherein the average particle size of the aforementioned tetrafluoroethylene-containing polymer particles is 0.1µm or more and 25µm or less.

6. The manufacturing method of claim 1, wherein the aforementioned particles containing tetrafluoroethylene polymer are mixed with the aforementioned aggregate in powder form.

7. The manufacturing method of claim 1, wherein the aforementioned particles containing tetrafluoroethylene polymer are dispersed in a dispersion medium and then mixed with the aforementioned aggregate.

8. The manufacturing method of claim 1, wherein the aforementioned forming is extrusion forming or rolling forming.

9. The manufacturing method of claim 1, wherein the thickness of the aforementioned sheet is 0.5 mm or more and 5 mm or less.

10. A method for manufacturing a laminated sheet, comprising laminating two or more sheets of a sheet obtained by any one of claims 1 to 9.

11. A sheet comprising: polytetrafluoroethylene (PTFE); a tetrafluoroethylene-based polymer having an oxygen-containing polar group and a melting temperature of 320°C or less; and inorganic particles having an average particle size of 1 to 20 µm and a specific surface area of ​​1 to 20 m² / g; wherein, when the total mass of the aforementioned PTFE and the aforementioned inorganic particles is 100% by mass, the contents of the aforementioned PTFE and the aforementioned inorganic particles are 5% by mass or more and 60% by mass or less, and 40% by mass or more and 95% by mass or less, respectively; the sheet comprises: 5% by mass or more and 30% by mass or less of the aforementioned tetrafluoroethylene-based polymer relative to 100 parts by mass of the aforementioned PTFE.

12. The sheet of claim 11, wherein the aforementioned inorganic particles comprise at least one selected from the group consisting of metal oxides, silicon oxides and nitrides.