Method for producing laminate and liquid composition

Abstract

[Problem] To provide: a multilayer body which has a polymer layer that is provided with the physical properties of a tetrafluoroethylene polymer and the physical properties of a maleimide compound; and a liquid composition which contains a tetrafluoroethylene polymer and a maleimide compound. [Solution] A method for producing a multilayer body according to the present invention forms a polymer layer by: applying a liquid composition, which contains a powder of a tetrafluoroethylene polymer having a melting temperature of 260°C or more and a thermosetting compound having a maleimide group and an arylene group, to the surface of a base material layer; heating the liquid composition at a temperature that is not less than 100°C but less than the melting temperature of the tetrafluoroethylene polymer; and further heating the liquid composition at a temperature that is not less than the melting temperature of the tetrafluoroethylene polymer. A liquid composition according to the present invention contains a powder of a specific tetrafluoroethylene polymer and the above-described thermosetting compound.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate and a liquid composition. [Background technology]

[0002] Printed wiring boards used for transmitting high-frequency signals are required to have excellent transmission characteristics. Tetrafluoroethylene-based polymers, which have low relative permittivity and dielectric loss tangent, have attracted attention as insulating layer materials for printed wiring boards with high transmission characteristics. Dispersions containing tetrafluoroethylene-based polymer powder are known as materials for forming insulating layers containing tetrafluoroethylene-based polymers. Patent Document 1 describes a method for producing a polymer-layered copper foil, in which a film made of a liquid composition containing polytetrafluoroethylene powder and a maleimide compound is attached to the surface of copper foil and heated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 051715 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the polymer layer-coated copper foil of Patent Document 1 has the problem that the polymer layer (insulating layer) formed from the film of the liquid composition and the copper foil are easily peeled off, and also has the problem that it is prone to warping, and the reliability of the printed wiring boards obtained by processing it is still insufficient. As a result of extensive research, the present inventors have found that when a liquid composition containing a powder of a tetrafluoroethylene-based polymer having a predetermined melting temperature and a predetermined maleimide compound is used and heated under different predetermined temperature conditions to form a polymer layer, a copper foil (laminate) with a polymer layer that is difficult to peel and warp can be obtained, and a printed wiring board with excellent transmission characteristics can be obtained from the copper foil. The inventors also found that a liquid composition containing a predetermined powder and a predetermined maleimide compound has excellent dispersibility and ease of handling. The object of the present invention is to provide such a laminate and such a liquid composition. [Means for solving the problem]

[0005] The present invention has the following aspects. <1> A method for producing a laminate, comprising: applying a liquid composition containing powder of a tetrafluoroethylene-based polymer having a melting temperature of 260°C or higher and a thermosetting compound having a maleimide group and an arylene group to the surface of a base layer; heating the liquid composition at a temperature of 100°C or higher but lower than the melting temperature of the tetrafluoroethylene-based polymer; and further heating the liquid composition at a temperature equal to or higher than the melting temperature of the tetrafluoroethylene-based polymer to form a polymer layer, thereby obtaining a laminate having the base layer and the polymer layer. <2> The tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or units based on hexafluoropropylene. <1> Manufacturing method. <3> The tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) and having a polar functional group, or a tetrafluoroethylene-based polymer containing 2.0 to 5.0 mol % of units based on perfluoro(alkyl vinyl ether) based on all units and having no polar functional group. <1> or <2> Manufacturing method. <4> The liquid composition further contains an inorganic filler. <1> ~ <3> A manufacturing method of any of the above. <5> The liquid composition further contains an elastomer. <1> ~ <4> A manufacturing method of any of the above. <6> the ratio of the content of the thermosetting compound to the content of the tetrafluoroethylene-based polymer in the liquid composition is 0.2 or less; <1> ~ <5> A manufacturing method of any of the above. <7> the glass transition point of the cured product of the thermosetting compound is equal to or lower than the melting temperature of the tetrafluoroethylene-based polymer; <1> ~ <6> A manufacturing method of any of the above. <8> The substrate layer is a metal foil or a polymer film. <1> ~ <7> A manufacturing method of any of the above. <9> A liquid composition comprising a powder of a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) and a thermosetting compound having a maleimide group and an arylene group, wherein the tetrafluoroethylene-based polymer has a polar functional group or contains 2.0 to 5.0 mol % of units based on perfluoro(alkyl vinyl ether) relative to all units, and does not have a polar functional group. <10> The molecular weight of the thermosetting compound is 300 to 2000. <9> A liquid composition. <11> The tetrafluoroethylene polymer powder has an average particle size of 40 μm or less. <9> or <10> A liquid composition. <12> Furthermore, the above-mentioned composition containing an inorganic filler <9> ~ <11> Any of the liquid compositions. <13> Furthermore, the above-mentioned <9> ~ <12> Any of the liquid compositions. <14> the ratio of the content of the thermosetting compound to the content of the tetrafluoroethylene-based polymer in the liquid composition is 0.2 or less; <9> ~ <13> Any of the liquid compositions. <15> The viscosity of the liquid composition at 25°C is 100 to 5000 mPa·s. <9> ~ <14> Any of the liquid compositions. [Effects of the Invention]

[0006] According to the present invention, a laminate having excellent peel strength and electrical properties is obtained, which has a base layer and a polymer layer containing a tetrafluoroethylene-based polymer and a cured product of a predetermined thermosetting compound. Also, a liquid composition having excellent dispersibility and handleability is obtained, which contains a powder of the predetermined tetrafluoroethylene-based polymer and a predetermined maleimide compound. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following terms have the following meanings: "Average particle size (D50)" is the cumulative 50% volume diameter of a powder of interest (powder or filler) determined by laser diffraction / scattering. In other words, the particle size distribution of the object is measured by laser diffraction / scattering, and a cumulative curve is calculated with the total volume of the particle population of the object as 100%. The average particle size (D50) is the particle size at the point on the cumulative curve where the cumulative volume is 50%. "D90" is the volume-based cumulative 90% diameter of the object, measured in the same manner. The "melting temperature (melting point)" is the temperature corresponding to the maximum value of the melting peak of a polymer as measured by differential scanning calorimetry (DSC). The "glass transition temperature (Tg)" is a value measured by analyzing a polymer, a cured product, or an elastomer using dynamic mechanical analysis (DMA). The "viscosity" is a value determined by measuring the liquid composition using a Brookfield viscometer at 25° C. and 30 rpm. The measurement is repeated three times, and the average value of the three measurements is used. The "thixotropy ratio" is a value (η1 / η2) calculated by dividing the viscosity η1 obtained by measuring the liquid composition at a rotation speed of 30 rpm by the viscosity η2 obtained by measuring the liquid composition at a rotation speed of 60 rpm. The "unit" in a polymer may be an atomic group formed directly from a monomer, or may be an atomic group in which a part of the structure is converted by treating the obtained polymer in a predetermined manner. A unit based on monomer A contained in a polymer is also simply referred to as a "monomer A unit."

[0008] The manufacturing method of the present invention (hereinafter also referred to as "this method") is a method for producing a laminate having a base layer and a polymer layer by applying a liquid composition containing powder of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") having a melting temperature of 260°C or higher and a thermosetting compound having a maleimide group and an arylene group (hereinafter also referred to as "maleimide compound") to the surface of a base layer, heating at a temperature of 100°C or higher but lower than the melting temperature of the F polymer (hereinafter also referred to as "initial heating"), and further heating at a temperature equal to or higher than the melting temperature of the F polymer (hereinafter also referred to as "later heating") to form a polymer layer.

[0009] This method makes it possible to obtain a laminate that combines the physical properties (electrical properties, etc.) of the F polymer with the physical properties (adhesion, low linear expansion, etc.) of the maleimide compound to a high degree, and that has excellent peel strength and electrical properties and is resistant to warping. The reason for this is not entirely clear, but is thought to be as follows. When a liquid composition containing a powder of a maleimide compound with high polarity and an F polymer with low polarity is applied to a substrate layer and heated once to form a polymer layer, the F polymer and the cured product of the maleimide compound are localized in the polymer layer. As a result, the linear expansion of the localized F polymer reduces the peel strength of the resulting laminate, making it prone to warping, and the localized cured product of the maleimide compound makes it prone to degraded electrical properties.

[0010] Therefore, in this method, the maleimide compound is partially cured (reacted) by initial heating to reduce its polarity, and then the fine powder of F polymer is melted and sintered by final heating to form a polymer layer. That is, in the final heating, the F polymer and the cured product of the maleimide compound are highly compatible with each other to form a polymer layer. As a result, a polymer layer is formed in which the F polymer and the cured product of the maleimide compound are uniformly distributed. Therefore, this method can produce a laminate having a polymer layer that highly possesses the respective physical properties (electrical properties of the F polymer, adhesion of the cured product of the maleimide compound, low linear expansion, etc.). Furthermore, such a laminate also has excellent flame retardancy because the cured product of the maleimide compound is highly dispersed in the flame-retardant F polymer in the polymer layer. The F powder used in this method preferably consists of an F polymer. The content of the F polymer in the powder is preferably 80% by mass or more, more preferably 100% by mass. Other components that may be included in the F powder include polymers different from the F polymer and inorganic materials.

[0011] The different polymers include aromatic polyesters, polyamideimides, thermoplastic polyimides, polyphenylene ethers, polyphenylene oxides. Examples of inorganic substances include 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). The F powder containing the above components preferably has a core-shell structure with an F polymer as the core and the above components as the shell, or a core-shell structure with an F polymer as the shell and the above components as the core. Such F powder can be obtained, for example, by coalescence (by collision, aggregation, etc.) of an F polymer powder and a powder of the above components.

[0012] The D50 of the F powder is preferably 40 μm or less, more preferably 25 μm or less, and even more preferably 8 μm or less. The D50 of the F powder is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 1 μm or more. In such a case, the dispersibility and handleability of the liquid composition are improved, and the compatibility between the F polymer and the cured product of the maleimide compound in forming the polymer layer is further promoted. The D90 of the F powder is preferably 15 μm or less, more preferably 10 μm or less. In other words, the F powder preferably does not contain coarse particles (F polymer particles with a particle size of 10 μm or more or 15 μm or more). In this case, compatibility between the F polymer and the cured product of the maleimide compound in the formation of the polymer layer is more likely to be promoted. The content of F powder in the liquid composition in this method is preferably 5% by mass or more, more preferably 10% by mass or more. The content of F powder is preferably 50% by mass or less, more preferably 30% by mass or less. In this case, the liquid composition tends to have excellent dispersibility and handleability, and compatibility between the F polymer and the cured product of the maleimide compound in forming the polymer layer is further promoted.

[0013] The F polymer in this method is a polymer containing units based on tetrafluoroethylene (TFE) (TFE units) having a melting temperature of 260°C or higher. F polymers include polytetrafluoroethylene (PTFE), copolymers of TFE and ethylene (ETFE), copolymers of TFE and propylene, copolymers of TFE and perfluoro(alkyl vinyl ether) (PAVE) (PFA), and copolymers of TFE and hexafluoropropylene (HFP) (FEP). The copolymers may further contain units based on other comonomers. In addition to TFE homopolymers, PTFE also includes copolymers of TFE with trace amounts of comonomers (PAVE, HFP, FAE, etc.) (so-called modified PTFE). The modified PTFE preferably contains 99.5 mol % or more, and more preferably 99.9 mol % or more, of TFE units relative to all units.

[0014] The F polymer is preferably a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) (PAVE units) and units based on hexafluoropropylene (HFP units). In this case, the F polymer may contain both PAVE units and HFP units, or only one of them. Preferred PAVEs are CF2=CFOCF3, CF2=CFOCF2CF3 and CF2=CFOCF2CF2CF3 (PPVE), with PPVE being more preferred. The F polymer may have a polar functional group (oxygen-containing polar group). The polar functional group may be contained in a unit in the F polymer, or may be contained in a terminal group of the polymer main chain. Examples of the latter include an F polymer having a polar functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer having a polar functional group obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment.

[0015] The polar functional group is preferably a hydroxyl group-containing group or a carbonyl group-containing group from the viewpoint of compatibility between the F polymer and the cured product of the maleimide-based compound in forming the polymer layer, and more preferably a carbonyl group-containing group from the viewpoint of dispersibility in the liquid composition. The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl group-containing group is a group containing a carbonyl group (>C(O)), and is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.), or a carbonate group (-OC(O)O-). The number of carbonyl-containing groups in the F polymer is 1 × 10 6The number per unit is preferably 10 to 5000, more preferably 100 to 3000, and further preferably 800 to 1500. The number of carbonyl group-containing groups in the F polymer can be quantified by the composition of the polymer or the method described in WO 2020 / 145133.

[0016] The F polymer is preferably a polymer containing TFE units and PAVE units, with the PAVE units comprising 1.5 to 5.0 mol % of the total units, and having a melting temperature of 280 to 320°C. As the F polymer, polymer (1) containing TFE units and PAVE units and having a polar functional group, and polymer (2) containing TFE units and PAVE units and containing 2.0 to 5.0 mol % of PAVE units based on all units but not having a polar functional group are preferred, with polymer (1) being more preferred. In this case, minute crystals are more likely to be formed in the formation of the polymer, and the compatibility between the F polymer and the cured product of the maleimide-based compound in the formation of the polymer layer is more likely to be promoted.

[0017] Polymer (1) is preferably a polymer containing TFE units, PAVE units, and units derived from a monomer having a polar functional group, and the polymer preferably contains 90 to 99 mol% of TFE units, 0.5 to 9.97 mol% of PAVE units, and 0.01 to 3 mol% of units derived from a monomer having a polar functional group, based on the total units. Moreover, as the monomer having a polar functional group, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (also known as himic acid anhydride; hereinafter also referred to as "NAH") are preferred. Specific examples of polymer (1) include the polymers described in WO 2018 / 16644.

[0018] The polymer (2) is composed only of TFE units and PAVE units, and preferably contains 95.0 to 98.0 mol % of TFE units and 2.0 to 5.0 mol % of PAVE units based on all units. The content of PAVE units in the polymer (2) is preferably 2.1 mol % or more, more preferably 2.2 mol % or more, based on all units. The term "polymer (2) has no polar functional group" means that the number of carbon atoms constituting the polymer main chain is 1 × 10 6 This means that the number of polar functional groups possessed by the polymer per unit area is less than 500. The number of polar functional groups is preferably 100 or less, and more preferably less than 50. The lower limit of the number of polar functional groups is usually 0. Polymer (2) may be produced using a polymerization initiator or chain transfer agent that does not generate a polar functional group as the terminal group of the polymer chain, or may be produced by fluorinating an F polymer having a polar functional group (such as an F polymer having a polar functional group derived from a polymerization initiator at the terminal group of the polymer main chain). Fluorination methods include methods using fluorine gas (see, for example, JP 2019-194314 A).

[0019] The melting temperature of the F polymer is 260° C. or higher, preferably 275 to 325° C., and more preferably 280 to 320° C. In this case, the F polymer and the maleimide compound are uniformly distributed in the polymer layer, and the laminate tends to have excellent electrical properties, peel strength, and low linear expansion. The glass transition point of the F polymer is preferably from 75 to 125°C, more preferably from 80 to 100°C.

[0020] The maleimide compound in this method is a compound having a maleimide group (a monovalent group represented by the following formula (1)) and an arylene group. [ka]

[0021] The maleimide compound preferably contains two or more maleimide groups, more preferably 2 to 10, and even more preferably 2 to 4. The maleimide compound may be in the form of an oligomer or a polymer. In this case, the maleimide group may be present only in the terminal group, only in the side chain, or both in the terminal group and the side chain.

[0022] The arylene group of the maleimide compound is preferably a phenylene group or a naphthylene group, more preferably a phenylene group. The hydrogen atom of the arylene group of the maleimide compound may be substituted with another atom or atomic group. Furthermore, the hydrogen atom of the arylene group may be substituted with a maleimide group. The maleimide compound preferably contains two or more phenylene groups. In this case, the polarity of the maleimide compound and its cured product is further reduced by initial heating, which improves compatibility with the F polymer during later heating and improves the physical properties of the laminate. In addition, the UV absorption of the laminate is improved, improving UV laser processability and facilitating processing of the laminate into a printed wiring board.

[0023] The maleimide compound may be one type or a mixture of two or more types. The maleimide compound is preferably a compound represented by the following formula (2): [ka] [In formula (2), Q is an n-valent organic group having an arylene group, and n is an integer of 2 to 4.]

[0024] The content of the maleimide compound in the liquid composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less. The ratio (mass ratio) of the content of the maleimide compound to the content of the F polymer in the liquid composition is preferably 0.001 or more, more preferably 0.01 or more. This ratio is preferably 0.2 or less, more preferably 0.15 or less. In this case, during the formation of the polymer layer, the cured product of the maleimide compound is surrounded by the molten F polymer, and a polymer layer having a dense sea-island structure with the F polymer as the sea and the cured product as the islands is easily formed. As a result, in the laminate, the physical properties of the F polymer and the physical properties of the thermoset product of the maleimide compound are better balanced, and the physical properties of the laminate, such as electrical properties, peel strength, warpage resistance, and flame retardancy, are easily improved.

[0025] The maleimide compound preferably has a glass transition point of a cured product that is equal to or lower than the melting temperature of the F polymer. Specifically, the glass transition point of the cured product of the maleimide compound is preferably 100 to 250° C. In this case, the F polymer and the maleimide compound are uniformly distributed in the polymer layer, and the laminate tends to have excellent electrical properties, peel strength, and low linear expansion. The molecular weight of the maleimide compound is preferably from 300 to 2000, more preferably from 500 to 1500. In this case, the F polymer and the cured product of the maleimide compound are uniformly distributed in the polymer layer, and the laminate tends to have excellent electrical properties, peel strength, and low linear expansion.

[0026] The liquid composition used in this method preferably contains a liquid dispersion medium. The liquid dispersion medium is a liquid compound that is inactive at 25°C and functions as a dispersion medium for the F powder and the maleimide-based compound. The liquid dispersion medium may be one type or a mixture of two or more types. In the case of a mixture, different liquid compounds are preferably compatible with each other. The boiling point of the liquid dispersion medium is preferably 125 to 250° C. In this case, when the liquid dispersion medium is removed from the liquid composition by initial heating, the F powder tends to flow and pack densely. As the liquid dispersion medium, from the viewpoint of adjusting the liquid properties (viscosity, thixotropy ratio, etc.) of the liquid composition and the solubility of the maleimide-based compound, an organic solvent (organic compound) is preferred, and from the viewpoint of the dispersion stability of the liquid composition, one or more liquid compounds selected from the group consisting of amides, ketones, and esters are preferred, and N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, and cyclopentanone are more preferred. The content of the liquid dispersion medium in the liquid composition is preferably 30% by mass or more, more preferably 50% by mass or more, and is preferably 90% by mass or less.

[0027] The liquid composition used in this method preferably further contains an inorganic filler, from the viewpoint of further improving the low linear expansion of the laminate. As the inorganic filler, nitride fillers and inorganic oxide fillers are preferred, with boron nitride fillers, beryllia fillers (beryllium oxide fillers), silicate fillers (silica fillers, wollastonite fillers, talc fillers), and metal oxide (cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.) fillers being more preferred, and silica fillers being even more preferred. The silica content in the inorganic filler is preferably 50% by mass or more, more preferably 75% by mass, and is preferably 100% by mass or less.

[0028] The inorganic filler is preferably at least partially 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.), their esters, alkanolamines, amines (trimethylamine, triethylamine, etc.), paraffin wax, silane coupling agents, silicones, and polysiloxanes. Preferred silane coupling agents are 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-isocyanatopropyltriethoxysilane.

[0029] The average particle size of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less, and is preferably 0.1 μm or more, more preferably 1 μm or more. The shape of the inorganic filler may be any of granular, needle-like (fibrous), and plate-like. Specific shapes of the inorganic filler include spherical, scale-like, layer-like, leaf-like, apricot-like, columnar, cockscomb-like, equiaxial, leaf-like, micaceous, block-like, flat, wedge-like, rosette-like, net-like, and prismatic shapes. Specific examples of inorganic fillers include silica fillers (such as the "Adma Fine" series manufactured by Admatechs Co., Ltd.), zinc oxide surface-treated with esters such as propylene glycol dicaprate (such as the "FINEX" series manufactured by Sakai Chemical Industry Co., Ltd.), spherical fused silica (such as the "SFP" series manufactured by Denka Co., Ltd.), coated with polyhydric alcohol and inorganic substances (such as the "Tipaque" series manufactured by Ishihara Sangyo Kaisha, Ltd.), rutile-type titanium dioxide surface-treated with alkylsilane (such as the "JMT" series manufactured by Teika Co., Ltd.), hollow Examples of fillers include silica fillers (such as the "E-SPHERES" series manufactured by Taiheiyo Cement Corporation, the "Silinax" series manufactured by Nittetsu Mining Co., Ltd., and the "Ecocospher" series manufactured by Emerson & Cumming Co., Ltd.), talc fillers (such as the "SG" series manufactured by Nippon Talc Co., Ltd.), steatite fillers (such as the "BST" series manufactured by Nippon Talc Co., Ltd.), and boron nitride fillers (such as the "UHP" series manufactured by Showa Denko KK and the "Denka Boron Nitride" series ("GP" and "HGP" grades) manufactured by Denka Co., Ltd.).

[0030] The content of the inorganic filler in the liquid composition is preferably 1% by mass or more, more preferably 3% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. The ratio (mass ratio) of the content of the inorganic filler to the content of the F polymer in the liquid composition is preferably 0.01 or more, more preferably 0.1 or more, and is preferably 1 or less, more preferably 0.8 or less.

[0031] In order to further improve the bendability of the laminate, the liquid composition used in this method preferably further contains an elastomer. As the elastomer, thermoplastic elastomers are preferred, and butylene-based elastomers, diene-based elastomers (isoprene-based elastomers, butadiene-based elastomers, etc.), styrene-based elastomers, acrylic elastomers, silicone-based elastomers, and fluorine-based elastomers are more preferred.

[0032] Examples of styrene-based elastomers include styrene-butadiene copolymers, hydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprene copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated styrene-butadiene-styrene block copolymers, and hydrogenated styrene-isoprene-styrene block copolymers. To improve adhesion to the F polymer, the elastomer is preferably modified to have functional groups, such as epoxy groups, carbonyl-containing groups, hydroxyl groups, isocyanate groups, and amino groups. The glass transition temperature of the elastomer is preferably 10° C. or lower, more preferably 5° C. or lower, in which case the bendability of the laminate is more likely to be improved. The elastomer may be soluble or insoluble in the liquid dispersion medium, and is preferably soluble in a solvent.

[0033] Specific examples of elastomers include liquid rubbers such as polybutadiene, polystyrene, and butadiene-acrylonitrile copolymer (NBR); reactive liquid rubbers such as butadiene-acrylonitrile copolymer (CTBN) with carboxyl groups at both ends and butadiene-acrylonitrile copolymer (ATBN) with amino groups at both ends; silicone rubbers such as polydimethylsiloxane having amino groups or epoxy groups at both ends or in the side chain; and particulate rubbers such as crosslinked NBR particles, crosslinked silicone particles, and acrylic core-shell particles. The content of the elastomer in the liquid composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less. The ratio (mass ratio) of the elastomer content to the F polymer content in the liquid composition is preferably 0.001 or more, more preferably 0.01 or more, and is preferably 0.2 or less, more preferably 0.15 or less.

[0034] The liquid composition used in this method may further contain a component that accelerates the curing of the maleimide compound (such as a radical polymerization initiator, an imidazole curing agent, a cationic curing agent, or another copolymerizable crosslinking monomer). In this case, the partial curing (reaction) of the maleimide compound during the initial heating step is controlled, making it easier to form a polymer layer in which the F polymer and the cured product of the maleimide compound are compatible with each other during the later heating step.

[0035] Such components include imidazoles (2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, etc.), secondary or tertiary amines (triethylamine, triethylenediamine, 2-(dimethylaminomethyl)phenol, tris(dimethylaminomethyl)phenol, benzyldimethylamine, etc.), amidines (1,8-diaza-bicyclo(5,4,0)-7-undecene, etc.), phosphines (triphenylphosphine, etc.), and the like. dibutyltin dimaleate, zinc naphthenate, cobalt naphthenate, tin oleate, etc.), metal chlorides (lithium chloride, zinc chloride, aluminum chloride, tin chloride, etc.), organic peroxides (tert-butyl peroxide, dicumyl peroxide, etc.), azo compounds (azobisisobutyronitrile, azobisdimethylvaleronitrile, etc.), mineral acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), alkali metal carbonates (sodium carbonate, etc.).

[0036] The liquid composition in this method may further contain a surfactant from the viewpoint of improving dispersibility and handling properties. The surfactant is preferably nonionic. The hydrophilic portion of the surfactant preferably has an oxyalkylene group or an alcoholic hydroxyl group. The oxyalkylene group may be composed of one type or two or more types, and in the latter case, the different types of oxyalkylene groups may be arranged randomly or in blocks. The oxyalkylene group is preferably an oxyethylene group.

[0037] The hydrophobic portion of the surfactant preferably has an acetylene group, a polysiloxane group, a perfluoroalkyl group, or a perfluoroalkenyl group, i.e., the surfactant is preferably an acetylene-based surfactant, a silicone-based surfactant, or a fluorine-based surfactant. Among these, the surfactant is more preferably a fluorine-based surfactant, and even more preferably a fluorine-based surfactant having a hydroxyl group (particularly an alcoholic hydroxyl group) or an oxyalkylene group and a perfluoroalkyl group or a perfluoroalkenyl group. Specific examples of such surfactants include the "Ftergent" series (manufactured by Neos Corporation), the "Surflon" series (manufactured by AGC Seimi Chemical Co., Ltd.), the "Megafac" series (manufactured by DIC Corporation), and the "Unidyne" series (manufactured by Daikin Industries, Ltd.). The content of the surfactant in the liquid composition is preferably 1 to 15% by mass, which tends to enhance the affinity between the components.

[0038] The viscosity of the liquid composition in this method at 25°C is preferably 50 mPa·s or more, more preferably 100 mPa·s or more, and preferably 5000 mPa·s or less, more preferably 1000 mPa·s or less. The thixotropy ratio of the liquid composition in this method is preferably 1.0 to 2.0. The pH of the liquid composition in this method is preferably 7 or less from the viewpoint of controlling the curing (reaction) of the maleimide compound.

[0039] The liquid composition in this method may further contain another resin, which may be a thermosetting resin or a thermoplastic resin. Examples of other resins include epoxy resins, maleimide resins, urethane resins, polyimides, polyamic acids, polyamideimides, polyphenylene ethers, polyphenylene oxides, liquid crystal polyesters, and fluoropolymers other than F polymers. In addition to the above-mentioned components, the liquid composition may contain additives such as a thixotropy-imparting agent, an antifoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a brightening agent, a colorant, a conductive agent, a release agent, a surface treatment agent, a viscosity adjuster, and a flame retardant.

[0040] The substrate layer in this method is preferably a metal substrate (metal foil of copper, nickel, aluminum, titanium, alloys thereof, etc.), a polymer film (film of polyimide, polyarylate, polysulfone, polyarylsulfone, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, liquid crystalline polyesteramide, etc.), or a prepreg (precursor of a fiber-reinforced resin substrate), more preferably a metal foil or a polymer film. The liquid composition is preferably applied to the surface of the substrate layer by coating, using methods such as spraying, roll coating, spin coating, gravure coating, microgravure coating, gravure offset coating, knife coating, kiss coating, bar coating, die coating, fountain-meyer bar coating, and slot die coating.

[0041] The initial heating temperature in this method is 100°C or higher and lower than the melting temperature of the F polymer. The initial heating temperature is preferably 150 to 250°C, more preferably 180 to 220°C. In this case, it is easier to control the partial curing (reaction) of the maleimide compound during the initial heating. The partial curing (reaction) of the maleimide compound may be a reaction involving a ring-opening reaction of the maleimide group (condensation reaction, addition reaction, etc.). The heating time for the initial heating is preferably 1 to 10 minutes. The temperature of the latter heating in this method is equal to or higher than the melting temperature of the F polymer. The temperature of the latter heating is preferably 300 to 400° C., more preferably 320 to 380° C. In this case, the F polymer powder is more highly melted, and the F polymer powder and the cured product of the maleimide compound are more compatible with each other, making it easier to form a polymer layer. The heating time for the latter heating step is preferably 1 to 10 minutes.

[0042] Examples of heating methods for the initial heating and the later heating include a method using an oven, a method using a ventilation drying furnace, and a method using heat rays such as infrared rays. In this method, the thickness of the polymer layer is preferably 0.1 to 150 μm. Specifically, if the substrate layer is a metal foil, the thickness of the polymer layer is preferably 1 to 30 μm. If the substrate layer is a polymer film, the thickness of the polymer layer is preferably 5 to 50 μm.

[0043] In this method, the liquid composition may be applied to only one surface of the substrate layer, or may be applied to both surfaces of the substrate layer. In the former case, a laminate having a substrate layer and a polymer layer formed on one surface of the substrate layer is obtained, while in the latter case, a laminate having a substrate layer and polymer layers formed on both surfaces of the substrate layer is obtained. The latter laminate is less prone to warping and therefore has excellent processability. Specific examples of such laminates include a metal-clad laminate having a metal foil and a polymer layer formed on at least one surface of the metal foil, and a multilayer film having a polyimide film and polymer layers formed on both surfaces of the polyimide film. These laminates have excellent physical properties such as electrical properties and are suitable as materials for printed circuit boards, etc. Specifically, such laminates can be used to produce flexible printed circuit boards and rigid printed circuit boards.

[0044] The liquid composition of the present invention (hereinafter also referred to as "the composition") is a liquid composition containing a powder of a tetrafluoroethylene polymer containing TFE units and PAVE units and a maleimide compound. The tetrafluoroethylene-based polymer in this composition is either a polymer containing TFE units and PAVE units and having a polar functional group, or a polymer containing TFE units and PAVE units and not having a polar functional group, with 2.0 to 5.0 mol % of the PAVE-based units relative to the total units (hereinafter collectively referred to as "PFA-based polymer"). The composition is a dispersion in which a PFA-based polymer powder is dispersed and a maleimide-based compound is highly dispersed or dissolved. The present composition has excellent dispersibility and handling properties, and although the reason for this is not entirely clear, it is thought to be as follows.

[0045] Maleimide compounds can be considered not only to be polar compounds but also to be compounds having a hydrophilic portion (maleimide group) and a hydrophobic portion (arylene group), and are thought to have the effect of thickening a liquid composition and the effect of reducing the surface tension of the liquid composition (surface-active effect). When a liquid composition containing such a compound contains a powder of a PFA-based polymer of a specific structure (a PFA-based polymer that has polar functional groups or a high content of PAVE units and has a high degree of freedom in the polymer chain without polar functional groups), which is a tetrafluoroethylene-based polymer that generally has low polarity and surface tension, it is thought that the above-mentioned effects of the maleimide-based compound (thickening effect and surfactant effect) are more likely to be expressed synergistically and in a balanced manner. As a result, it is believed that powder settling and foaming are suppressed and the thickening of the composition is contained, resulting in a liquid composition (the present composition) with excellent dispersibility and handleability. Furthermore, since the PFA-based polymer forms microspherulites during the formation of a molded product (such as the polymer layer in the present method) and is highly compatible with the cured product of the maleimide-based compound, the use of the present composition makes it easier to obtain a molded product that possesses the high physical properties of the PFA-based polymer and the maleimide-based compound.

[0046] The form of the PFA polymer powder in the present composition is the same as the form of the powder in the present method described above, and the preferred forms thereof are also the same. The PFA polymer in the present composition is the polymer (1) or polymer (2) in the present method described above, and the preferred range is also the same. The polar functional group in the polymer (1) is preferably a hydroxyl group-containing group or a carbonyl group-containing group, more preferably a carbonyl group-containing group, from the viewpoint of more easily exhibiting the above-mentioned effects. The maleimide compound in the composition is similar to the maleimide compound in the method described above, and the preferred embodiments thereof are also similar.

[0047] If the maleimide compound has two or more maleimide groups and two or more arylene groups, the above-mentioned effects are more easily exhibited. The ratio (mass ratio) of the content of the maleimide compound to the content of the PFA polymer in the composition is preferably 0.001 or more, more preferably 0.01 or more. This ratio is preferably 0.2 or less, more preferably 0.15 or less. When the maleimide compound is contained in such a ratio, not only is the above-mentioned effect more easily exhibited, but also a dense sea-island structure in which the PFA polymer forms the sea and the cured maleimide compound forms the islands is more easily formed in a molded article formed therefrom, making it easier to obtain a molded article that exhibits high physical properties of both.

[0048] The composition preferably comprises a liquid dispersion medium, the embodiments of which are the same as those of the liquid dispersion medium in the present method, including preferred embodiments. The composition preferably further comprises an inorganic filler, the embodiments of which are the same as those of the inorganic filler in the present method, including preferred embodiments. The composition preferably further comprises an elastomer, the elastomer aspects of which are similar to those of the elastomer in the present method, including preferred aspects.

[0049] The present composition may further contain a component that further accelerates the curing reaction of the maleimide compound, a surfactant, other resins, and other additives (such as a thixotropic agent, an antifoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a brightener, a colorant, a conductive agent, a mold release agent, a surface treatment agent, a viscosity modifier, and a flame retardant). The embodiments of these components, including preferred embodiments thereof, are the same as those in the present method. The total content of the components that form the molded product in the composition (including, in addition to the PFA-based polymer and maleimide-based compound, inorganic fillers, elastomers, other resins (polymers), or other additive components, if any) is preferably 30% by mass or more, more preferably 50% by mass or more. The total content is preferably 80% by mass or less. Even if the content of the components that form the molded product is high, the composition has excellent dispersibility and handleability due to the above-mentioned effects.

[0050] The viscosity of the composition at 25°C is preferably 50 mPa·s or more, more preferably 100 mPa·s or more, and is preferably 5000 mPa·s or less, more preferably 1000 mPa·s or less. The thixotropy ratio of the present composition at 25°C is preferably 1.0 to 2.0. The present composition is preferably acidic from the viewpoint of the curing (reaction) properties of the maleimide compound.

[0051] This composition can form a layer that has the adhesiveness derived from the cured product of the maleimide compound and the high gas barrier properties derived from the F polymer. Therefore, this composition is also useful as a heat sealant for packaging films (pillow packaging films, etc.). This composition is particularly useful as a heat sealant for packaging materials for products (food, chemicals, etc.) that are susceptible to quality deterioration due to water vapor or oxygen. Specifically, this composition is useful as a heat sealant for packaging materials for foods such as confectionery, food cups, food trays, etc., packaging materials for pharmaceutical and agrochemical products, packaging materials for chemical products, and packaging materials for precision electronic components such as semiconductors. In this case, this composition may contain an adhesive and an antistatic agent.

[0052] When using the present composition as a heat-sealing agent, the present composition may be applied to the base material of a packaging material. For example, two sheets of packaging material may be prepared, the composition may be applied to the seal area of at least one of the sheets, the two sheets may be placed on top of each other, and the two sheets may be heat-sealed by heating using a heat sealer. The substrate may be made of pulp, metal, plastic, or glass. The substrate preferably has a substrate layer and a gas barrier layer. The barrier layer may contain a water-soluble polymer (such as polyvinyl alcohol) and a crosslinking agent. The substrate layer may be formed solely from the above-mentioned substrate material, or may be formed from a plurality of the above-mentioned substrate materials. Specific examples of the former include paper, metal foil, and plastic film. Specific examples of the latter include laminated paper of paper and plastic, a laminate of plastic film and aluminum foil, and a laminate of different plastic films. The substrate layer may further have a vapor-deposited layer of an inorganic oxide such as aluminum, silica, or alumina. [Example]

[0053] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the following materials were used: [powder] Powder 1: Powder (D50: 2.1 μm) consisting of polymer 1 (melting temperature: 300°C) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units, in that order, and having polar functional groups. Powder 2: Powder (D50: 1.8 μm) consisting of polymer 2 (melting temperature 305° C.) containing 98.7 mol% TFE units and 1.3 mol% PPVE units, in that order, and having no polar functional groups. Polymer 1 has a carbonyl group-containing group with a main chain carbon number of 1 × 10 6 Each piece has 1000 pieces.

[0054] [Maleimide compounds] Maleimide 1: A compound having a maleimide group and a phenylene group Maleimide 1 is a mixture of compounds having 2 to 4 maleimide groups and multiple phenylene groups, and has a number average molecular weight of 800 and a glass transition point of 280°C when cured. [Liquid dispersion medium] NMP: N-methyl-2-pyrrolidone

[0055] [Surfactants] Surfactant 1: CH2=C(CH3)C(O)OCH2CH2(CF2)6F and CH2=C(CH3)C(O)(OCH2CH2) 23 Copolymer with OH [Inorganic filler] Filler 1: Silica filler (D50: 5.2 μm) [Elastomer] Elastomer 1: Amine-modified styrene-based elastomer (SEBS, manufactured by Asahi Kasei Corporation, "Tuftec MP10")

[0056] (Example 1) Example of production of liquid composition (Example 1-1) Surfactant 1 was added to a solution containing maleimide 1 and NMP, and then elastomer 1 and filler 1 were added in this order, followed by stirring to prepare a mixed solution. Separately, surfactant 1 and powder 1 were added to NMP and stirred to prepare a dispersion. The mixture and dispersion were mixed and stirred to obtain Liquid Composition 1 (viscosity: 500 mPa s) containing Powder 1 (30 parts by mass), Maleimide 1 (3 parts by mass), Elastomer 1 (3 parts by mass), Filler 1 (15 parts by mass), Surfactant 1 (4 parts by mass), and NMP (45 parts by mass). Liquid Composition 1 was a dispersion in which Powder 1 was dispersed. (Example 1-2 to Example 1-5) Liquid compositions 2 to 5 were obtained in the same manner as in Example 1-1, except that the types and amounts of each component were changed as shown in Table 1 below.

[0057] [Table 1]

[0058] The results of evaluation of the obtained liquid compositions with respect to dispersion stability, handling properties, viscosity and thixotropy ratio are summarized in Table 2 below. The dispersion stability and handling properties were evaluated according to the following methods.

[0059] [Dispersion stability] After the liquid composition was stored at 25°C, its dispersibility was visually confirmed and the dispersion stability was evaluated according to the following criteria. [Evaluation criteria] ○: No sediment is visible. △: Sediment is visible, but can be easily redispersed. ×: Sediment was visible and redispersion was difficult.

[0060] [Handling] The foaming state during mixing of the mixed liquid and the dispersion liquid in preparing the liquid composition was visually confirmed and evaluated according to the following criteria. [Evaluation criteria] ○: Foaming disappears within 3 hours after preparation. ×: Foaming does not disappear even after 3 hours have passed since preparation.

[0061] [Table 2]

[0062] (Example 2) Example of laminate manufacturing (Example 2-1) Example of manufacturing laminate 1 Liquid composition 1 was applied to the surface of a long copper foil (thickness: 18 μm) using a bar coater to form a wet film. Next, the metal foil on which this wet film had been formed was heated in a nitrogen oven at an initial heating temperature of 200°C for 5 minutes. Thereafter, it was heated in a nitrogen oven at a final heating temperature of 380°C for 3 minutes. This produced laminate 1 having metal foil and, on its surface, polymer layer 1 (thickness: 5 μm) containing F polymer 1, a cured product of maleimide 1, filler 1, and elastomer 1.

[0063] (Example 2-2) Example of manufacturing laminate 2 A laminate 2 was obtained from liquid composition 2 in the same manner as in Example 2-1, except that the type of liquid composition used was changed to liquid composition 2. (Example 2-3) Example of manufacturing laminate 5 Laminate 5 was obtained in the same manner as in Example 2-1, except that the initial heating temperature was 100°C. (Example 2-4) Example of manufacturing laminate 6 Laminate 6 was obtained in the same manner as in Example 2-1, except that the initial heating was omitted.

[0064] The evaluation results of the dielectric loss tangent, peel strength, coefficient of linear expansion, and bendability of each laminate, as well as the evaluation results of the transmission properties of the printed wiring boards obtained by processing each laminate, are shown in Table 3. Each evaluation was carried out according to the following methods.

[0065] [Dissipation Factor] The copper foil of the laminate was removed by etching with an aqueous solution of ferric chloride to produce a single polymer layer, which was then measured by the SPDR (split post dielectric resonance) method at a measurement frequency of 10 GHz. [Evaluation criteria] Good: The dielectric loss tangent is less than 0.0012. △: The dielectric loss tangent is 0.0012 or more and 0.0024 or less. ×: The dielectric loss tangent is more than 0.0024.

[0066] [Peel strength] A rectangular test piece (100 mm long, 10 mm wide) was cut out from the laminate. The test piece was fixed at a position 50 mm from one end in the longitudinal direction, and the copper foil and polymer layer were peeled off from one end in the longitudinal direction at a 90° angle to the test piece at a pulling rate of 50 mm / min. The maximum load at this time was measured as the peel strength (N / cm). [Evaluation criteria] ◯: Peel strength was 8 N / cm or more. △: Peel strength was 4 N / cm or more and less than 8 N / cm. ×: The peel strength was less than 4 N / cm.

[0067] [Linear expansion coefficient] The copper foil of the laminate was removed by etching with an aqueous solution of ferric chloride to produce a single polymer layer, and a square test piece measuring 180 mm square was cut out from the resultant laminate. The linear expansion coefficient of the test piece was measured in the temperature range of 25°C to 260°C according to the measurement method specified in JIS C 6471:1995. [Evaluation criteria] ○: Less than 30 ppm / ℃. △: More than 30 ppm / ℃ and 50 ppm / ℃ or less. ×: More than 50 ppm / °C.

[0068] [Bendability] The copper foil of the laminate was removed by etching with a ferric chloride solution to produce a single polymer layer, and a 5 mm square test piece was cut out. The test piece was then bent 180° with a curvature radius of 300 μm, and a load of 50 mN was applied from above for 1 minute, after which the bend was reversed. The appearance of the test piece was evaluated according to the following criteria. [Evaluation criteria] ○: No abnormal appearance was observed at the fold. △: Whitening was observed at the fold. ×: Broken at the crease.

[0069] The transmission characteristics of the printed circuit board obtained by processing the resulting laminate were measured and evaluated according to the following method. [Transmission characteristics] A printed wiring board was made by forming a transmission line on the copper foil of the laminate. A microstrip line was used to form the transmission line. A 28 GHz signal on the printed wiring board was processed using a vector network analyzer (Keysight Technologies, "E8361A"), and the S21 parameter, which represents transmission loss, was measured using a Universal Test Fixture as a probe. The characteristic impedance of the line was set to 50 Ω, and the length of the transmission line on the printed wiring board was set to 50 mm, and the transmission loss was measured. The transmission loss was measured using the "S21-parameter," a circuit network parameter used to express the characteristics of high-frequency electronic circuits and components. The closer this value is to 0, the smaller the transmission loss. [Evaluation criteria] ○: -0.7 or more and 0 or less. △: Less than -0.7 and greater than or equal to -1.0. ×: Less than −1.0.

[0070] [Table 3]

[0071] The copper foil of the laminate was removed by etching with a ferric chloride solution to create a single polymer layer, and the polymer layer was evaluated to see if it met the UL94-V0 flame retardancy standard. As a result, the polymer layers of Laminates 1 and 2 met the standard, but the polymer layers of Laminates 5 and 6 did not. [Industrial Applicability]

[0072] According to the present invention, a molded article having the physical properties derived from a tetrafluoroethylene-based polymer and the physical properties derived from a maleimide-based compound can be obtained. The molded article obtained by the present invention is useful as an antenna part, a printed circuit board, an aircraft part, an automobile part, a sporting goods, a food industry article, a paint, a cosmetic, etc., and specifically as an electric wire coating material (such as an electric wire for an aircraft), an electrical insulating tape, an insulating tape for oil drilling, a material for a printed circuit board, a separation membrane (such as a microfiltration membrane, an ultrafiltration membrane, a reverse osmosis membrane, an ion exchange membrane, a dialysis membrane, a gas separation membrane), an electrode binder (for a lithium secondary battery, for a fuel cell, etc.), a copy roll, a cover for furniture, an automobile dashboard, an electric appliance, etc., a sliding part (such as a load bearing, a sliding shaft, a valve, a bearing, a gear, a cam, a belt conveyor, a food transport belt, etc.), a tool (such as a shovel, a file, an awl, a saw), a boiler, a hopper, a pipe, an oven, a baking mold, a chute, a die, a toilet, and a container coating material.

Claims

1. A liquid composition comprising a powder of a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) and having a melting temperature of 280 to 320°C, and a thermosetting compound having a maleimide group and an arylene group, the cured product of which has a glass transition temperature equal to or lower than the melting temperature of the tetrafluoroethylene-based polymer, wherein the tetrafluoroethylene-based polymer has a carbonyl group-containing group.

2. The liquid composition according to claim 1, wherein the molecular weight of the thermosetting compound is 300 to 2,000.

3. 3. The liquid composition according to claim 1, wherein the tetrafluoroethylene-based polymer powder has an average particle size of 40 μm or less.

4. The liquid composition according to any one of claims 1 to 3, further comprising an inorganic filler.

5. The liquid composition according to any one of claims 1 to 4, further comprising an elastomer.

6. The liquid composition according to any one of claims 1 to 5, wherein the ratio of the content of the thermosetting compound to the content of the tetrafluoroethylene-based polymer in the liquid composition is 0.2 or less.

7. The liquid composition according to any one of claims 1 to 6, wherein the viscosity of the liquid composition at 25°C is 100 to 5000 mPa·s.

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