Powder composition, film, and method for producing film

Abstract

Provided are: a powder composition suitable for forming, by melt extrusion, films having excellent dielectric characteristics and having adhesion, processability, and low linear expansion; and a film suitable for use as a material for printed wiring boards.　The powder composition comprises a powder of a tetrafluoroethylene-based polymer including a unit based on a perfluoro(alkyl vinyl ether) or a unit based on hexafluoropropylene, a powder of an inorganic filler having a Mohs hardness of 3-9, and a powder of a thermoplastic aromatic polymer. The film comprises these ingredients and at least has a sea-island structure composed of a sea phase, which includes the aromatic polymer, and an island phase, which includes the tetrafluoroethylene-based polymer.

Description

[Technical field]

[0001] The present invention relates to a powder composition and a film and method of making the same. [Background technology]

[0002] In recent years, in the field of information and communications, there has been a demand for higher density printed circuit boards used therein in view of the trend toward higher signal frequencies and downsizing. As insulating materials for printed circuit boards, films formed by impregnating glass cloth with thermosetting resin, and films formed from aromatic polymers such as polyimide and liquid crystalline aromatic polymers are used. Furthermore, tetrafluoroethylene-based polymers, which have better electrical properties than these aromatic polymers, have attracted attention, and powder compositions in which powders of both types are blended, and molded articles formed from the powder compositions have been proposed (see Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-265729 A [Patent Document 2] JP 2003-171538 A [Patent Document 3] JP 2003-200534 A [Patent Document 4] JP 2019-065061 A Summary of the Invention [Problem to be solved by the invention]

[0004] Tetrafluoroethylene-based polymers have low surface tension, and their powders have extremely low affinity with aromatic polymers. Therefore, molded products formed from a powder composition in which both powders are blended are unlikely to fully possess the physical properties of both polymers, not to mention shape properties such as mechanical strength and processability, due to layer separation, etc. The present inventors have found that when the powder composition is further blended with other fillers, this tendency tends to become more pronounced, and the effects of blending with other fillers are unlikely to be achieved. An object of the present invention is to provide a powder composition suitable for forming a molded product which contains a specified tetrafluoroethylene-based polymer, an aromatic polymer and a filler and which satisfies the physical properties of the three to a high degree, not limited to shape properties such as mechanical strength, and a film which satisfies the physical properties of the three to a high degree, and a method for producing the same. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A powder composition comprising a powder of a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or units based on hexafluoropropylene, a powder of an inorganic filler having a Mohs hardness of 3 to 9, and a powder of a thermoplastic aromatic polymer. [2] The powder composition according to [1], wherein the tetrafluoroethylene-based polymer is a polymer having an oxygen-containing polar group, which includes a unit based on tetrafluoroethylene and a unit based on perfluoro(alkyl vinyl ether). [3] The powder composition of [1] or [2], wherein the inorganic filler is a filler containing silicon oxide. [4] The powder composition according to any one of [1] to [3], wherein the aromatic polymer is polyimide, polyamideimide, polyester, polyesteramide, polyphenylene ether or polyphenylene sulfide. [5] The powder composition according to any one of [1] to [4], wherein the aromatic polymer is a liquid crystal polymer.

[0006] [6] The powder composition according to any one of [1] to [5], wherein the average particle size of the powder of the tetrafluoroethylene-based polymer is larger than the average particle size of the inorganic filler. [7] The powder composition according to any one of [1] to [6], wherein the content of the aromatic polymer is greater than the content of the tetrafluoroethylene-based polymer. [8] The powder composition according to any one of [1] to [7], wherein the ratio of the content of the inorganic filler to the content of the tetrafluoroethylene-based polymer is 0.2 to 0.6. [9] The powder composition according to any one of [1] to [8], wherein the content of the tetrafluoroethylene-based polymer, the content of the inorganic filler, and the content of the aromatic polymer are, in this order, 10 to 40 mass%, 5 to 40 mass%, and 20 to 85 mass%.

[10] A powder composition according to any one of [1] to [9], which is used for melt extrusion molding.

[0007]

[11] A method for producing a film, comprising melt-extrusion molding any one of the powder compositions according to [1] to

[10] to obtain a film.

[12] A film comprising a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or units based on hexafluoropropylene, an inorganic filler having a Mohs hardness of 3 to 9, and a thermoplastic aromatic polymer, the film having at least a sea-island structure composed of a sea phase containing the aromatic polymer and an island phase containing the tetrafluoroethylene-based polymer.

[13] The film of

[12] , wherein the amount of the tetrafluoroethylene-based polymer distributed in a surface region in the thickness direction of the film is higher than the amount of the tetrafluoroethylene-based polymer distributed in a central region in the thickness direction of the film.

[14] The film of

[12] or

[13] , wherein the distribution amount of the inorganic filler in a central region in the thickness direction of the film is higher than the distribution amount of the inorganic filler in a surface region in the thickness direction of the film.

[15] The film of any one of

[12] to

[14] , wherein the thickness of the film is 5 to 1000 μm. Effect of the Invention

[0008] According to the powder composition of the present invention, a molded product such as a film containing a powder of a tetrafluoroethylene-based polymer, a powder of an aromatic polymer, and a powder of a filler, each of which is specified, can be obtained, and which has high physical properties of the three, not limited to shape properties such as mechanical strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The following terms have the following meanings. The "average particle size" is the cumulative 50% volume diameter of a target object determined by laser diffraction / scattering method. The term "melting temperature (melting point)" refers to the temperature corresponding to the maximum value of the melting peak, as determined by analyzing a polymer by differential scanning calorimetry (DSC). The "glass transition point" is a value measured by analyzing a polymer using a dynamic mechanical analysis (DMA) method. The term "approximately spherical inorganic filler" refers to an inorganic filler in which, when observed with a scanning electron microscope (SEM), the proportion of spherical particles with a minor axis to major axis ratio of 0.7 or more accounts for 95% or more.

[0010] The powder composition of the present invention (hereinafter also referred to as "the composition") contains a powder of a tetrafluoroethylene-based polymer (hereinafter also referred to as "TFE-based polymer") containing units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units) or units based on hexafluoropropylene (HFP) (HFP units), a powder of an inorganic filler having a Mohs hardness of 3 to 9 (hereinafter, an inorganic filler having this specific hardness will be referred to as "hard inorganic filler"), and a powder of a thermoplastic aromatic polymer (hereinafter also referred to as "TAr polymer"). By subjecting this composition to melt extrusion molding, a molded product such as a film can be obtained that has a good balance between the physical properties of the TFE polymer (electrical properties such as low dielectric tangent), the physical properties of the TAr polymer (processability, optical properties, etc.), and the physical properties of the hard inorganic filler (low linear expansion, etc.). The reason for this is not entirely clear, but is thought to be as follows.

[0011] The TFE-based polymer can be said to be a thermoplastic and crystalline polymer, and has excellent physical stress resistance and heat resistance, and its powder has a certain hardness. Therefore, during melt extrusion molding, the softened TFE-based polymer powder is crushed and atomized by the hard inorganic filler, and is densely dispersed in the molten or softened TAr polymer. In addition, during this dispersion, the TFE-based polymer itself does not change in quality (fibrillation, etc.), so it is thought that the affinity between any of the components is not impaired. It is therefore believed that when this composition is subjected to melt extrusion molding, a molded article containing a dense hard inorganic filler and having an island-in-sea structure composed of a sea phase containing the TAr polymer and fine island phases containing the TFE-based polymer can be easily formed. Therefore, it is believed that the molded article obtained from this composition will be one that has the physical properties of the three components (TFE-based polymer, TAr polymer, and hard inorganic filler) at a high level. Specifically, the molded product (film, etc.) obtained by melt extrusion molding of the present composition has physical properties such as low dielectric constant, low dielectric loss tangent, low linear expansion coefficient, adhesiveness, and moldability. Such molded products can be suitably used as materials or members for printed circuit boards. The molded product obtained from the present composition preferably has a dielectric constant of 2.0 to 4.0 measured at 10 GHz.

[0012] The TFE-based polymer in the present invention is a polymer containing TFE units and PAVE units or HFP units, i.e., a polymer containing TFE units and PAVE units (PFA-based polymer) or a polymer containing TFE units and HFP units (FEP-based polymer), and is more preferably a PFA-based polymer from the viewpoints of being more excellent in physical stress resistance and heat resistance and of forming fine spherulites in the molded product to further enhance adhesion. Preferred PAVEs are CF2=CFOCF3 (PMVE), CF2=CFOCF2CF3 and CF2=CFOCF2CF2CF3 (PPVE). The melting temperature (melting point) of the TFE polymer is preferably from 260 to 320°C, and more preferably from 285 to 320°C. The glass transition point of the TFE polymer is preferably from 75 to 125°C, and more preferably from 80 to 100°C.

[0013] The TFE-based polymer preferably further contains units based on other monomers. Examples of the other monomers include olefins (such as ethylene and propylene), chlorotrifluoroethylene, fluoroolefins (such as hexafluoropropylene and fluoroalkylethylene), and monomers having an oxygen-containing polar group, which will be described later. Specific examples of fluoroalkylethylenes include CH2=CH(CF2)2F, CH2=CH(CF2)4F, CH2=CF(CF2)2H, and CH2=CF(CF2)4H.

[0014] The TFE polymer preferably has an oxygen-containing polar group. The oxygen-containing polar group may be contained in the unit contained in the TFE polymer, or may be contained in the end group of the polymer main chain. The latter TFE polymer may include a TFE polymer having an oxygen-containing polar functional group as an end group derived from a polymerization initiator, a chain transfer agent, etc., and a TFE polymer having an oxygen-containing polar group prepared by plasma treatment, ionizing radiation treatment, or radiation treatment. As the oxygen-containing polar group, a hydroxyl group-containing group, a carbonyl group-containing group, and a phosphono group-containing group are preferred, a hydroxyl group-containing group and a carbonyl group-containing group are more preferred, and a carbonyl group-containing group is particularly preferred. As the hydroxyl-containing group, an alcoholic hydroxyl-containing group is preferred, and -CF2CH2OH, -C(CF3)2OH and 1,2-glycol group (-CH(OH)CH2OH) are more preferred. The carbonyl group-containing group is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH2), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) and a carbonate group (-OC(O)O-), and more preferably an acid anhydride residue. When the TFE-based polymer has a carbonyl group-containing group, the number of carbonyl group-containing groups in the TFE-based polymer is 1×10 6 The number of carbonyl-containing groups per unit is preferably 10 to 5000, more preferably 50 to 2000. The number of carbonyl-containing groups in the TFE-based polymer can be quantified by the composition of the polymer or the method described in WO2020 / 145133.

[0015] The TFE-based polymer having an oxygen-containing polar group particularly preferably has a unit based on a monomer having an oxygen-containing polar group. The monomer is preferably a monomer having a hydroxyl group-containing group or a carbonyl group-containing group, and more preferably a monomer having a carbonyl group-containing group. As the monomer having a carbonyl group-containing group, itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride (also called himic anhydride; hereinafter also referred to as "NAH") and maleic anhydride are preferred, and NAH is more preferred. Specific preferred examples of the TFE-based polymer include polymer (1) containing TFE units, PAVE units, and units based on a monomer having an oxygen-containing polar group, polymer (2) consisting of 95.0 to 98.0 mol % TFE units and 2.0 to 5.0 mol % PAVE units, and polymer containing TFE units and PMVE units. These polymers are particularly excellent in resistance to physical stress, and when a powder composition thereof is subjected to melt extrusion molding, minute spherulites are formed, and molded articles having excellent adhesive properties are easily formed.

[0016] The polymer (1) is preferably a polymer containing TFE units, PAVE units, and a monomer having a hydroxyl group-containing group or a carbonyl group-containing group, and the polymer (1) is preferably a polymer containing 90 to 98 mol % of TFE units, 1.5 to 9.97 mol % of PAVE units, and 0.01 to 3 mol % of units based on the above monomers, based on all units. Specific examples of polymer (1) include the polymers described in WO 2018 / 16644.

[0017] The polymer (2) is preferably a polymer consisting of only TFE units and PAVE units. The content of PAVE units in the polymer (2) is preferably 2.1 mol % or more, and more preferably 2.2 mol % or more, based on the total monomer units. It is preferable that the polymer (2) does not have an oxygen-containing polar group. In addition, the fact that the polymer (2) does not have an oxygen-containing polar group means that the number of the oxygen-containing polar groups is 1×10 of the carbon atoms constituting the polymer main chain. 6 This means that the number of oxygen-containing polar groups in the polymer per unit is less than 500. The number of oxygen-containing polar groups is preferably 100 or less, and more preferably less than 50. The lower limit of the number of oxygen-containing polar groups is usually 0.

[0018] The polymer (2) may be produced by using a polymerization initiator or a chain transfer agent that does not generate an oxygen-containing polar group as a terminal group of the polymer chain, or by subjecting a TFE-based polymer having an oxygen-containing polar group to a fluorination treatment. An example of a fluorination treatment method is a method using fluorine gas (see JP 2019-194314 A, etc.).

[0019] At least a part of the fine particles constituting the powder of the TFE-based polymer may be fine particles containing components other than the TFE-based polymer, but it is preferable that the fine particles are made of the TFE-based polymer. The components other than the TFE-based polymer include, for example, a thermoplastic polymer. The thermoplastic polymer may be a TAr polymer. Examples of thermoplastic polymers other than the TAr polymer include TFE-based polymers and polymers other than the TAr polymers described below. When the TFE-based polymer powder contains a polymer component other than the TFE-based polymer, the amount of the polymer component other than the TFE-based polymer is preferably 30% by mass or less, more preferably 15% by mass or less, of the total polymer components. When the polymer component other than the TFE-based polymer is a TAr polymer, the content of the TAr polymer is preferably 20% by mass or less, more preferably 10% by mass or less, of the total polymer components.

[0020] At least a part of the fine particles constituting the TFE polymer powder may be TFE polymer fine particles containing an inorganic filler. As the material of the inorganic filler, oxides, nitrides, metal elements, alloys and carbon are preferred, silicon oxide (silica), metal oxides (beryllium oxide, cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide, titanium oxide, etc.), boron nitride and magnesium metasilicate (steatite) are more preferred, silica and boron nitride are even more preferred, and silica is particularly preferred. The inorganic filler may be a hard inorganic filler, in which case it is a part of the total amount of the hard inorganic filler contained in the powder composition of the present invention, and the rest is a powder of the hard inorganic filler. The fine particles containing a TFE-based polymer and an inorganic filler are preferably particles having a TFE-based polymer core and an inorganic filler on the surface of the core. Such particles are obtained, for example, by bonding (collision, aggregation, etc.) particles of a TFE-based polymer and particles of an inorganic filler. When the TFE-based polymer powder is a powder containing fine particles including a TFE-based polymer and an inorganic filler, the TFE-based polymer tends to be uniformly dispersed in the TAr polymer during melt molding. When at least a part of the TFE polymer powder is a powder containing fine particles containing a TFE polymer and an inorganic filler, the amount of the inorganic filler in the powder is preferably 50% by mass or less, more preferably 40% by mass or less, relative to the powder. When at least a part of the inorganic filler is a hard inorganic filler, the amount of the hard inorganic filler is preferably 40% by mass or less, more preferably 30% by mass or less, relative to the powder.

[0021] Furthermore, the fine particles constituting the TFE polymer powder may contain additives such as organic fillers, organic pigments, metal soaps, surfactants, UV absorbers, lubricants, silane coupling agents, etc. When such additives are contained, the amount of such additives in the powder is preferably 10% by mass or less, more preferably 5% by mass or less, based on the powder.

[0022] The average particle size of the TFE polymer powder (i.e., the average particle size of the fine particles constituting the TFE polymer powder) is preferably 0.1 to 200 μm, more preferably 1 to 100 μm. In this case, the pulverization of the TFE polymer powder by the hard inorganic filler proceeds to a high degree in the melt extrusion molding, and a molded product having a denser sea-island structure is easily formed.

[0023] The hard inorganic filler in the present invention is an inorganic filler having a Mohs hardness of 3-9. The Mohs hardness of the hard inorganic filler is preferably at least 5, and more preferably at least 6. In this case, the pulverization of the TFE-based polymer powder by the hard inorganic filler tends to proceed to a high degree in the melt extrusion molding. The hard inorganic filler may contain components other than inorganic components, but is preferably composed of inorganic components. Examples of components other than inorganic components include organic compounds such as organic substances used in surface treatment agents described below, and soft inorganic compounds such as boron nitride. As the hard inorganic filler, inorganic fillers made of aluminum nitride, beryllium oxide (beryllia), silicon oxide (silica), cerium oxide, aluminum oxide (alumina), magnesium oxide (magnesia), zinc oxide or titanium oxide are preferable. The hard inorganic filler may consist of two or more inorganic components.

[0024] The hard inorganic filler is preferably one containing silicon oxide. Hard inorganic fillers containing silicon oxide not only have high hardness, but also tend to enhance the interaction with TFE-based polymers. Therefore, molded articles containing such inorganic fillers are likely to form molded articles having a denser sea-island structure in melt extrusion molding. In addition, the low linear expansion property is particularly likely to be exhibited. The content of silicon oxide in the hard inorganic filler is preferably 50% by mass or more, more preferably 75% by mass or more, and is preferably 100% by mass or less. As the hard inorganic filler, beryllia filler (Mohs hardness: 9), magnesia filler (Mohs hardness: 5.5) and silica filler (Mohs hardness: 7) are preferable, and silica filler is more preferable. The silica filler is preferably a fused silica filler or an amorphous silica filler, since in this case the molded product is more likely to have low thermal expansion properties.

[0025] At least a part of the surface of the hard inorganic filler may be surface-treated. Examples of surface treatment agents used for such surface treatment include polyhydric alcohols (trimethylolethane, pentaerythritol, propylene glycol, etc.), saturated fatty acids (stearic acid, lauric acid, etc.), esters thereof, alkanolamines, amines (trimethylamine, triethylamine, etc.), paraffin wax, silane coupling agents, silicones, polysiloxanes, and oxides of metals such as aluminum, silicon, zirconium, tin, titanium, and antimony, hydroxides of these metals, hydrated oxides of these metals, and phosphates of these metals. As the silane coupling agent, a silane coupling agent having a functional group is preferable, and 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and 3-isocyanatopropyltriethoxysilane are more preferable.

[0026] The average particle size of the hard inorganic filler powder (i.e., the average particle size of the fine particles constituting the hard inorganic filler powder) is preferably 0.01 μm or more, more preferably 0.1 μm or more, and is preferably 10 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. The average particle size of the hard inorganic filler is preferably equal to or smaller than the average particle size of the TFE-based polymer powder. When the average particle size of the hard inorganic filler powder is within this range, pulverization of the TFE polymer powder proceeds to a high degree during melt extrusion molding, making it easier to form a molded product having a denser sea-island structure. Specifically, a combination of a powder of a hard inorganic filler having an average particle size of more than 0.10 μm and 1 μm or less and a powder of a TFE-based polymer having an average particle size of 1 μm or more and 3 μm or less is preferred.

[0027] The shape of the fine particles constituting the hard inorganic filler is preferably almost perfectly spherical. In spherical particles that account for 95% or more of the almost perfectly spherical hard inorganic filler, the ratio of the minor axis to the major axis is preferably 0.8 or more, more preferably 0.9 or more. The ratio is preferably less than 1. The powder of the hard inorganic filler consisting of nearly spherical fine particles is likely to enhance the interaction with each component during melt extrusion molding. Suitable specific examples of hard inorganic filler powders include silica fillers having an average particle size of 1 μm or less (such as the "Admafine" series manufactured by Admatechs Co., Ltd.) and spherical fused silica having an average particle size of more than 0.10 μm and 0.5 μm or less (such as the "SFP" series manufactured by Denka Co., Ltd.).

[0028] As the TAr polymer in the present invention, aromatic polyimide, aromatic polyamideimide, aromatic polyester, aromatic polyesteramide, polyphenylene ether and polyphenylene sulfide are preferred. The TAr polymer is preferably a liquid crystal polymer. The liquid crystal polymer is a TAr polymer that forms an anisotropic molten phase, and is generally called a thermotropic liquid crystal polymer. Specific liquid crystal polymers include aromatic polyesters and aromatic polyester amides that are thermoplastic and liquid crystal, the former being often called thermotropic liquid crystal polyesters, and the latter being often called thermotropic liquid crystal polyester amides. The liquid crystal polymer may further include an imide bond, a carbonate bond, a carbodiimide bond, an isocyanurate bond, or the like.

[0029] As described above, when the present composition is subjected to melt extrusion molding, the TFE-based polymer and the hard inorganic filler are highly dispersed in the TAr polymer to form a molded article. Therefore, the anisotropy of the physical properties in the flow direction (MD) of the molded product, which is likely to occur when the TAr polymer is a liquid crystal polymer, is easily alleviated by the highly dispersed TFE-based polymer and hard inorganic filler. In other words, the molded product (film, etc.) obtained by melt extrusion molding of the present composition in which the TAr polymer is a liquid crystal polymer is likely to have high isotropy. As a result, it is easy to obtain a molded product that has the inherent physical properties of the liquid crystal polymer (mechanical properties such as strength, elasticity, and vibration absorption, and electrical properties such as dielectric properties) while suppressing the decrease in tensile strength and thermal expansion caused by anisotropy. In particular, it is easy to obtain a molded product such as a film that has excellent dimensional stability when immersed in a chemical solution or when heated.

[0030] The anisotropic molten phase of the liquid crystal polymer may be confirmed, for example, by placing a polymer sample on a hot stage, heating it in a nitrogen gas atmosphere, and observing the light transmitted through the polymer sample. The melting temperature (melting point) of the liquid crystal polymer is preferably from 250 to 370°C, and more preferably from 270 to 350°C. Specific examples of TAr polymers, which are liquid crystal polymers, include "LAPEROS" manufactured by Polyplastics, "VECTRA" manufactured by Celanese, "UENO LCP" manufactured by Ueno Pharmaceutical Co., Ltd., "Sumika Super LCP" manufactured by Sumitomo Chemical Co., Ltd., "XYDAR" manufactured by Solvay Specialty Polymers, Inc., "Xydar" manufactured by JX Nippon Oil & Energy Corporation, and "Sciberas" manufactured by Toray Industries, Inc.

[0031] The powder of TAr polymer is a powder consisting of fine particles containing TAr polymer at a ratio of 50% by mass or more, and preferably a powder consisting of fine particles containing TAr polymer at a ratio of 60 to 100% by mass. The fine particles constituting the powder may be fine particles containing components other than TAr polymer. Such components include thermoplastic polymers other than TAr polymer, fibrous inorganic fillers, fibrous organic fillers, non-fibrous inorganic fillers, non-fibrous organic fillers, organic pigments, metal soaps, surfactants, ultraviolet absorbers, lubricants, silane coupling agents, and other additives. The thermoplastic polymer other than TAr polymer may be a TFE-based polymer, and the non-fibrous inorganic filler may be a hard inorganic filler. As components other than the TAr polymer, preferred are fibrous fillers such as glass fibers, carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers), organic synthetic fibers (aromatic polyamide fibers, etc.), metal fibers (stainless steel fibers, aluminum fibers, etc.), inorganic fibers (silicon carbide fibers, potassium titanate fibers, alumina fibers, etc.), and natural mineral fibers (wallasnite, asbestos, etc.).

[0032] When the powder fine particles of the TAr polymer contain a fibrous filler, the content of the fibrous filler in the powder is preferably 40% by mass or less, and more preferably 35% by mass or less. When the powder fine particles of the TAr polymer contain a thermoplastic polymer other than the TAr polymer, the content of the thermoplastic polymer in the powder is preferably 40% by mass or less, more preferably 20% by mass or less, of the total polymer components, except when the thermoplastic polymer is a TFE-based polymer, which is preferably 20% by mass or less, more preferably 10% by mass or less, of the total polymer components. When the powder particulates of the TAr polymer contain additives other than those mentioned above, such as non-fibrous inorganic fillers, the content of such additives in the powder is preferably 30% by mass or less, more preferably 15% by mass or less. However, when the additive is a hard inorganic filler, the amount of the hard inorganic filler relative to the powder is preferably 20% by mass or less, more preferably 10% by mass or less.

[0033] The average particle size of the TAr polymer powder (i.e., the average particle size of the fine particles constituting the TAr polymer powder) is preferably 0.1 to 200 μm, more preferably 1 to 100 μm. In this case, the TFE-based polymer and the hard inorganic filler are dispersed in the TAr polymer during melt extrusion molding, and a molded product having a dense sea-island structure is easily formed.

[0034] The present composition may further contain a powder other than the TFE-based polymer powder, the hard inorganic filler powder, and the TAr polymer powder. Examples of other powders include powders of thermoplastic polymers other than TFE-based polymers and TAr polymers, powders of polymers other than thermoplastic polymers, powders of fillers other than hard inorganic fillers (such as the above-mentioned inorganic fillers and organic fillers), etc. Examples of organic fillers include fibrous organic fillers made of fibers of polymers that do not melt in melt extrusion molding. Specific examples of the thermoplastic polymer include polyolefin-based polymers (polyethylene, polypropylene, polybutylene, acid-modified polyethylene, acid-modified polypropylene, acid-modified polybutylene, etc.), fluorine-based polymers other than TFE-based polymers (polyvinylidene fluoride, polytetrafluoroethylene, etc.), styrene-based polymers (polystyrene, polyacrylonitrile styrene, polyacrylonitrile butadiene styrene, etc.), polycarbonate-based polymers, poly(meth)acrylic-based polymers, polyvinyl chloride, polyarylate-based polymers, and polyurethane-based polymers. Examples of powders of polymers other than thermoplastic polymers include powders of cured thermosetting resins, powders of non-thermoplastic polytetrafluoroethylene, and the like. Examples of the organic filler powder include powders made of aromatic polyamide fibers, polyaramid fibers, polyparaphenylene benzoxazole fibers, polyphenylene sulfide fibers, polyester fibers, acrylic fibers, nylon fibers, polyethylene fibers, and the like. When the present composition contains the other powders, the content of the other powders in the present composition is preferably 30% by mass or less, and more preferably 15% by mass or less.

[0035] It is particularly preferable that the present composition is a composition consisting of three kinds of powders: TFE-based polymer powder, hard inorganic filler powder, and TAr polymer powder. The content ratios of these three powders in the present composition below refer to the ratios in the composition consisting of these three powders. The content of the TFE polymer in the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less. The content of the TAr polymer in the composition is preferably 10% by mass or more, more preferably 20% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less. The content of the TAr polymer in the composition is preferably greater than the content of the TFE-based polymer. In other words, the composition preferably contains the TAr polymer as a main polymer component. In this case, the interaction with the TFE-based polymer is easily enhanced, so that a molded product having a denser sea-island structure is easily formed in melt extrusion molding. In addition, the low linear expansion property is particularly easily exhibited.

[0036] The content of the hard inorganic filler in the present composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less. In the present composition, the ratio of the content of the hard inorganic filler to the content of the TFE polymer is preferably 0.2 to 1.0, more preferably 0.2 to 0.6. In this case, the powder of the TFE polymer is highly pulverized in the melt extrusion molding, and a molded product in which the hard inorganic filler is highly dispersed is easily obtained. In addition, the molded product is likely to have the physical properties of the three components to a high degree. In the present composition, the respective contents of the TFE-based polymer, the TAr polymer, and the hard inorganic filler are preferably 10 to 40% by mass, 5 to 40% by mass, and 20 to 85% by mass, respectively.

[0037] The composition is preferably produced by dry blending the components, which can be produced using a mixer such as a tumbler, a Henschel mixer, a hopper, a Banbury mixer, a roll, or a Brabender mixer. The composition is preferably used in melt extrusion and is preferably formed into a film by melt extrusion. The melt extrusion molding is preferably carried out by a method using a T-die, and more preferably by a method in which the composition is fed from a hopper, melt-kneaded in an extruder (single screw or twin screw), and extruded from a T-die installed at the tip of the extruder to form a film.

[0038] The film obtained by melt extrusion is preferably further stretched to obtain a more isotropic film. The stretching process is a process in which the film is softened at a temperature below its melting point and stretched in one direction (uniaxial: MD) or two directions (biaxial: MD and TD). The stretching treatment is preferably a biaxial stretching treatment from the viewpoint of obtaining an isotropic film. The stretching method includes an inflation method and a flat method. As the flat method, either a simultaneous biaxial stretching method or a sequential biaxial stretching method can be used.

[0039] In the production of a film by melt extrusion, the resulting film may be further subjected to lamination, stretching, cooling and peeling treatments. The lamination treatment is a treatment in which a release film is laminated on either or both sides of the obtained film to form a laminate. Examples of the lamination method include a thermocompression method and a surface treatment method, in which a thermocompression roll, a heat press device, or a laminator is used. For example, when a thermocompression roller is used, the obtained film and the release film are overlapped and passed through the thermocompression roller to perform thermocompression bonding. When a hot press is used, the obtained film and the release film are placed on the bottom plate of the hot press, thermocompressed, and then cooled.

[0040] Alternatively, a pair of thermocompression rolls may be used, and the present composition in a molten state extruded from a T-die is supplied to the gap between two release films, and a laminate may be formed in the gap between the thermocompression rolls. In forming this laminate, if a co-extrusion method using a multi-layer die is used, a multi-layer body can be formed having a film formed from the present composition and a release film as separate layers. Examples of materials for the release film include polyethylene, polypropylene, polyether ether ketone, polyether sulfone, polyimide, polyetherimide, polyarylate, polycarbonate, polystyrene, polyvinyl chloride, polyester, polyamide, polyamideimide, thermoplastic polyimide, polyphenylene sulfide, polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of polytetrafluoroethylene and ethylene, polyvinyl fluoride, polyvinylidene fluoride, and polytrifluorochloroethylene. The thickness of the release film is preferably from 10 to 200 μm, more preferably from 20 to 100 μm.

[0041] The stretching treatment is a treatment in which the laminate obtained in the lamination treatment is stretched to obtain a stretched product while softening the release film layer of the laminate. This stretching treatment may be carried out continuously. The cooling treatment is a treatment for cooling the stretched product obtained in the stretching treatment. The cooling may be performed naturally or using a cooling roll or the like. The peeling treatment is a treatment in which the release film is peeled off from the cooled stretched product. The peeling treatment can be performed by the 90° peeling method or the 180° peeling method. Through such a series of treatments, a film having a further suppressed thermal expansion coefficient can be obtained from the present composition.

[0042] In forming the film, inflation molding may be used. In inflation molding, the molten mixture of the composition extruded from an annular die (round die, circular die) is stretched in two directions (MD and TD), which tends to improve the isotropy of the film. In inflation molding, the molten mixture is mechanically stretched in two directions by taking off and expanding, which tends to mold a film in which the polymer molecules are oriented in two directions. In this case, a film having a similar structure to the above-mentioned laminate may be formed by inflation molding. That is, the composition and another thermoplastic polymer are melt-extruded through an annular die and then formed into a laminate by inflation molding.

[0043] Examples of laminates that can be formed in this case include a two-layer laminate (Type 1) consisting of one film layer formed from the present composition and one release film layer, a three-layer laminate (Type 2) in which a film layer formed from the present composition is sandwiched between two release film layers, and a three-layer laminate (Type 3) in which one release film layer is sandwiched between two film layers formed from the present composition, with Type 1 laminates and Type 3 laminates being preferred. In these laminates, the thickness of the film layer formed from the present composition is preferably 3 to 150 μm, and the thickness of the release film layer is preferably not less than the thickness of the above film layer and not more than twice the thickness. By carrying out such a series of treatments, a film having a further suppressed thermal expansion coefficient can be obtained from the present composition.

[0044] The film of the present invention (hereinafter also referred to as "the film") contains a TFE-based polymer, an inorganic filler having a Mohs hardness of 3 to 9, and a TAr polymer, and has a sea-island structure composed of a sea phase containing the TAr polymer and an island phase containing the TFE-based polymer. The definitions of the TFE-based polymer, the hard inorganic filler, and the TAr polymer in the present film, including the preferred ranges thereof, are the same as those in the present composition. In the present film, the TFE-based polymer, the hard inorganic filler, and the TAr polymer may be present in a uniformly distributed state or in a non-uniformly distributed state.

[0045] The amount of TFE-based polymer distributed in the surface region of the present film in the thickness direction is preferably higher than the amount of TFE-based polymer distributed in the center region of the film in the thickness direction, in which case the physical properties attributable to the TFE-based polymer in the present film (particularly dielectric properties such as low dielectric constant and adhesive properties) tend to be significantly exhibited. The amount of the hard inorganic filler distributed in the central region of the present film in the thickness direction is preferably higher than the amount of the hard inorganic filler distributed in the surface region of the present film in the thickness direction, in which case the physical properties (especially low linear expansion property, etc.) attributable to the hard inorganic filler in the present film are more likely to be significantly exhibited.

[0046] The thickness of the present film is preferably from 5 to 1000 μm, and more preferably from 10 to 200 μm. The present film is preferably produced by melt extrusion of the present composition, which makes it easy to produce films of any of the above-mentioned various configurations without impairing mechanical strength and processability such as foldability. The present film is preferably produced by a T-die coating method, specifically, the present composition is preferably extruded in a molten state from a T-die and brought into contact with a chill roll to form a film. The present composition is preferably heated and held in a non-contact heating section before coming into contact with the chill roll. The composition cooled by the cooling roll is preferably formed into a film while being transported by a transport roller, and then wound up by a take-up roll into a long film.

[0047] The present film is preferably made into a metal clad laminate by forming a metal layer on its surface. Examples of metals include various metals such as copper, nickel, aluminum, silver, gold, and tin, and alloys thereof (such as stainless steel). Examples of such metal clad laminates include single-sided metal clad laminates having a metal layer and the present film in this order, and double-sided metal clad laminates having a metal layer, the present film layer, and a metal layer in this order. These metal clad laminates may further have other layers (prepreg layers, glass member layers, ceramic member layers, other resin film layers). Methods for forming a metal layer on the surface of the present film include a method of adhering a metal foil to the surface of the present film by lamination or thermocompression bonding, a method of forming a metal layer on the surface of the present film by sputtering or vapor deposition, a method of forming a metal layer on the surface of the present film by plating (including electroless plating and electrolytic plating after electroless plating), and a method of forming a metal layer on the surface of the present film by printing (screen printing, inkjet, ion plating) using a metal conductive ink. As the metal foil, a copper foil such as a rolled copper foil or an electrolytic copper foil is preferable.

[0048] In order to further improve adhesion to a metal layer, the surface of the present film may be subjected to a surface treatment such as a plasma treatment, a corona treatment, a flame treatment, or an itro treatment. Such metal clad laminates can be used as materials or members for printed circuit boards, high heat dissipation boards, antenna boards, and the like. For example, a printed circuit board can be obtained by forming a pattern circuit by etching the metal layer of such a metal clad laminate. In this case, after forming the pattern circuit, an interlayer insulating film may be formed on the pattern circuit, and a further pattern circuit may be formed on the interlayer insulating film. Also, a solder resist may be laminated on the pattern circuit, or a coverlay film may be laminated. A coverlay film is typically composed of a base film and an adhesive layer formed on the surface thereof, and the surface on the adhesive layer side is attached to a printed circuit board. This film may be used as the base film of the coverlay film. Also, an interlayer insulating film (adhesive layer) using this film may be formed on the pattern circuit, and a polyimide film may be laminated as the coverlay film. EXAMPLES

[0049] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. The raw materials used are shown below. 1. Preparation of each ingredient PFA-based powder 1: PFA-based powder containing 98.0 mol% TFE units, 0.1 mol% NAH units, and 1.9 mol% PPVE units, in that order, and a carbonyl-containing group with a main chain carbon number of 1 × 10 6 Powder (average particle size: 2.0 μm) made of PFA-based polymer (melting temperature: 300°C) with 1000 particles per particle PFA-based powder 2: A carbonyl-containing group consisting of TFE units and PPVE units, with a main chain carbon number of 1 x 10 6 Powder (average particle size: 2.4 μm) made of PFA-based polymer (melting temperature: 305°C) with 40 particles per particle Aromatic powder 1: Powder of liquid crystal polymer, an aromatic polymer, containing 30% by mass of glass fiber (melting temperature: 320°C; Ueno Pharmaceutical Co., Ltd., "UENO LCP 6030G") Inorganic filler 1: Silica filler with a Mohs hardness of 7 and a nearly spherical shape (average particle size: 0.5 μm; Admatechs Co., Ltd., "Admafine SO-C2") Inorganic filler 2: Silica filler having a Mohs hardness of 7 and a nearly spherical shape (average particle size: 5 μm) Inorganic filler 3: Mohs hardness 1, talc filler (average particle size: 0.7 μm)

[0050] The dimensional stability of the film was evaluated in accordance with JIS C 6481:1996. A square sample having two sides along the machine direction and two sides along the width direction and measuring 30 cm on each side was cut out from an end in the width direction of the obtained film. Lines 25 cm long were drawn on each diagonal of the surface of this sample (the 45° direction, which is at an angle of 45° with respect to the flow direction, and the 135° direction perpendicular to this 45° direction), and punch holes were formed with their centers at both ends of each line. The sample was immersed in an aqueous solution of iron chloride, and the distance between the centers of the two punched holes was measured before and after immersion to determine the rate of expansion and contraction of the film in the diagonal direction during etching. The sample was subjected to a heat treatment by heating at 150°C for 30 minutes and then cooling to 25°C. The distance between the centers of the two punched holes before and after the heat treatment was measured to determine the diagonal expansion and contraction rate of the film during the heat treatment.

[0051] 2. Examples of Powder Composition and Film Production [Example 1] PFA-based powder 1 (20 parts by mass), aromatic powder 1 (100 parts by mass), and hard inorganic filler 1 (15 parts by mass) were dry-blended to prepare powder composition 1. Powder composition 1 was charged into a twin-screw extruder (manufactured by Technobel Co., Ltd., "KZW15TW-45MG") and melt-kneaded (screw rotation speed: 200 rpm, set resin temperature: 370°C), and discharged from a T-die installed at the tip of the extruder at 2.0 kg / hr to form a flat film 1 (thickness: 100 μm). Film 1 showed high adhesion to copper foil and had excellent dielectric properties with a dielectric constant of 2.9. In addition, the diagonal expansion rate of film 1 during etching and the diagonal expansion rate (absolute value) of film 1 during heat treatment were both less than 0.1%, and film 1 had excellent dimensional stability. [Examples 2-4] Films 2 to 4 were obtained in the same manner as Film 1, except that the types and amounts of the powders and inorganic fillers were changed as shown in Table 1 below.

[0052] 3. Evaluation 3-1. Evaluation of dimensional thermal stability The dimensional change rate of each film was measured as follows and evaluated according to the following criteria. The dimensional stability of the film was evaluated in accordance with JIS C 6481:1996. A square sample measuring 30 cm on each side was cut out from each film. A line segment 25 cm long was drawn on the surface of this sample, and punch holes were formed with their centers at both ends of the line segment. The sample was subjected to a heat treatment in which it was heated at 150°C for 30 minutes and then cooled to 25°C. The distance between the centers of the two punched holes was measured before and after the heat treatment, and the absolute value of the expansion and contraction rate of the film during the heat treatment was regarded as the dimensional thermal change rate. [Evaluation Criteria] ○: Dimensional thermal change rate is less than 1.5% △: Dimensional thermal change rate is 1.5 to 2% ×: Dimensional thermal change rate exceeds 2%

[0053] 3-2. Evaluation of adhesion The adhesion of each film was measured as follows and evaluated according to the following criteria. Each film and a pure copper foil were placed facing each other and hot pressed (temperature: 340°C, pressure: 15 kN / m) to obtain a laminate having a film layer and a copper foil layer. A rectangular test piece having a length of 100 mm and a width of 10 mm was cut out from this laminate. The copper foil layer was peeled from the film layer to a position 50 mm from one end in the longitudinal direction of the test piece. During the peeling, the test piece was peeled at 90 degrees at a pulling speed of 50 mm / min using a tensile tester (manufactured by Orientec Co., Ltd.) with the position 50 mm from one end in the longitudinal direction of the test piece as the center, and the average load was measured from a measurement distance of 10 mm to 30 mm, which was taken as the peel strength (N / cm). [Evaluation Criteria] ◯: Peel strength is 10 N / cm or more. △: The peel strength is 5 N / cm or more and less than 10 N / cm. ×: The peel strength is less than 5 N / cm.

[0054] [Table 1]

[0055] Each film was frozen in liquid nitrogen and then cut, and the cut surface was observed with a scanning electron microscope (Hitachi High-Technologies Corporation, FE-SEM). As a result, films 1 to 4 had a sea-island structure composed of a sea phase containing liquid crystal polymer 1 and an island phase containing PFA-based polymer 1 or 2. Furthermore, for films 1 to 3, the distribution amount of the PFA-based polymer in the surface region in the film thickness direction was higher than the distribution amount of the PFA-based polymer in the central region in the film thickness direction. [Industrial Applicability]

[0056] The powder composition of the present invention and the film of the present invention are useful as materials or components for printed circuit boards used in electronic devices that require high-frequency characteristics, particularly reduced transmission loss in the millimeter wave band (radar, network routers, backplanes, wireless infrastructure, automotive sensors, engine management sensors, etc.). The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2019-204147, filed on November 11, 2019, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims

1. The powder comprises a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or units based on hexafluoropropylene, a powder of an inorganic filler which is silica or boron nitride, and a powder of a thermoplastic aromatic polymer; the aromatic polymer is an aromatic polyimide, an aromatic polyamideimide, an aromatic polyester, an aromatic polyesteramide, a polyphenylene ether or a polyphenylene sulfide; the average particle size of the tetrafluoroethylene-based polymer powder is larger than the average particle size of the inorganic filler, the content of the aromatic polymer is greater than the content of the tetrafluoroethylene-based polymer, The powder composition, wherein the content of the tetrafluoroethylene-based polymer, the content of the inorganic filler, and the content of the aromatic polymer are 10 to 40 mass%, 5 to 40 mass%, and 20 to 85 mass%, respectively.

2. 2. The powder composition of claim 1, wherein the tetrafluoroethylene-based polymer is a polymer having oxygen-containing polar groups that include units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether).

3. The powder composition according to claim 1 or 2, wherein the aromatic polymer is a liquid crystal polymer.

4. 4. The powder composition according to claim 1, wherein a ratio of the content of the inorganic filler to the content of the tetrafluoroethylene-based polymer is 0.2 to 0.

6.

5. The powder composition according to any one of claims 1 to 4, which is used for melt extrusion molding.

6. A method for producing a film, comprising melt extruding the powder composition according to any one of claims 1 to 5 to obtain a film.

7. The present invention relates to a method for producing a thermoplastic aromatic polymer comprising: a tetrafluoroethylene-based polymer containing a unit based on perfluoro(alkyl vinyl ether) or a unit based on hexafluoropropylene; an inorganic filler which is silica or boron nitride; and a thermoplastic aromatic polymer, the method comprising at least a sea-island structure constituted of a sea phase containing the aromatic polymer and an island phase containing the tetrafluoroethylene-based polymer; the aromatic polymer is an aromatic polyimide, an aromatic polyamideimide, an aromatic polyester, an aromatic polyesteramide, a polyphenylene ether or a polyphenylene sulfide; the content of the aromatic polymer is greater than the content of the tetrafluoroethylene-based polymer, The film has a content of the tetrafluoroethylene-based polymer, a content of the inorganic filler, and a content of the aromatic polymer, in this order, of 10 to 40 mass %, 5 to 40 mass %, and 20 to 85 mass %.

8. The film according to claim 7 , wherein the distribution amount of the tetrafluoroethylene-based polymer in a surface region in the thickness direction of the film is higher than the distribution amount of the tetrafluoroethylene-based polymer in a central region in the thickness direction of the film.

9. The film according to claim 7 or 8, wherein a distribution amount of the inorganic filler in a central region in the thickness direction of the film is higher than a distribution amount of the inorganic filler in a surface region in the thickness direction of the film.

10. The film according to any one of claims 7 to 9, wherein the thickness of the film is from 5 to 1000 µm.

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