Method for producing surface-modified tetrafluoroethylene polymer, method for producing modified powder, liquid composition, method for producing modified molded product, and modified molded product

Abstract

[Problem] To provide: a method for producing a modified tetrafluoroethylene-based polymer and a powder by modifying a tetrafluoroethylene-based polymer and a powder of the polymer; and a method for producing a modified molded article by highly modifying the surface of a molded article of a tetrafluoroethylene-based polymer. [Solution] A method for producing a modified tetrafluoroethylene-based polymer and a powder, the method comprising subjecting a tetrafluoroethylene-based polymer and a powder of the polymer to a plasma treatment under an atmosphere having a pressure close to the atmospheric pressure to produce a surface-modified tetrafluoroethylene-based polymer; and a method for producing a molded article which has, as at least a portion of the surface thereof, a modified layer formed by introducing a hydrogen atom into a tetrafluoroethylene-based polymer, the method comprising subjecting a surface layer of a molded article having, as at least a portion of the surface layer thereof, a surface layer comprising the tetrafluoroethylene-based polymer to a plasma treatment under an atmosphere containing a reducing gas having a hydrogen atom and having a pressure close to the atmospheric pressure.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a surface-modified tetrafluoroethylene polymer, a method for producing a modified powder, a liquid composition, a method for producing a modified molded product, and a modified molded product. [Background technology]

[0002] Tetrafluoroethylene-based polymers have excellent physical properties such as mold releasability, electrical insulation, water and oil repellency, chemical resistance, weather resistance, and heat resistance, and liquid compositions in which such polymer powders are dispersed are useful as materials that can easily be used to form various molded products (Patent Document 1). However, tetrafluoroethylene polymers have extremely low polarity and poor interaction with other compounds, such as liquid dispersion media, and therefore the dispersibility of the powder is still insufficient. Therefore, in order to improve the dispersibility of the powder and adjust the liquid properties of the liquid composition, adjusters such as surfactants and thickeners are often added to such liquid compositions.

[0003] Furthermore, tetrafluoroethylene-based polymer films have excellent physical properties such as electrical insulation, water and oil repellency, chemical resistance, and heat resistance, and are useful as printed circuit board materials, etc. (Patent Document 2). However, tetrafluoroethylene-based polymer films still lack sufficient adhesiveness. Therefore, modifications to the film surface have been investigated with the aim of improving surface properties such as adhesiveness. Patent Document 3 describes a method in which a polytetrafluoroethylene film is subjected to plasma treatment in an atmosphere containing a rare gas at near atmospheric pressure, thereby introducing peroxide functional groups into the film surface.

[0004] In addition, tetrafluoroethylene-based polymers are low-polarity polymers with excellent insulation resistance and dielectric breakdown properties, and the surfaces of molded articles made from them are difficult to modify. Furthermore, the behavior of tetrafluoroethylene-based polymers when subjected to plasma treatment is not fully known, and the effects are difficult to stabilize and sometimes difficult to sustain.

[0005] Therefore, at present, other methods are combined with the plasma treatment of molded products of tetrafluoroethylene polymers. For example, in Patent Document 3, a polytetrafluoroethylene film is plasma treated to introduce peroxide functional groups onto the surface, then immersed in water to introduce hydroxyl groups onto the surface, and then treated with a silane coupling agent to modify the surface of the film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2016 / 159102 Brochure [Patent Document 2] International Publication No. 2019 / 142790 Brochure [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-049819 Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors have investigated a plasma treatment method for highly modifying the surface of tetrafluoroethylene-based polymer powder. As a result, they found that when the surface of a tetrafluoroethylene-based polymer powder is treated under specified plasma treatment conditions, the surface is modified, and the surface properties such as the wettability of the powder and the dispersibility of a liquid composition prepared from it are improved without impairing the physical properties.

[0008] Furthermore, in the case of plasma treatment of tetrafluoroethylene-based polymer molded articles, the present inventors investigated plasma treatment conditions that can highly modify the surface of tetrafluoroethylene-based polymer molded articles, without requiring the combinations described in Patent Document 3. As a result, they found that when such molded articles are treated under specific plasma treatment conditions, a stable layer is formed. They also found that the formation of such a layer improves the wettability of the molded article and improves surface physical properties such as adhesion, without impairing the physical properties of the tetrafluoroethylene-based polymer of the entire molded article.

[0009] An object of the present invention is to provide a method for highly modifying a tetrafluoroethylene-based polymer to improve its physical properties. The present invention aims to provide a method for highly surface-modifying tetrafluoroethylene polymer powder to improve its surface physical properties, and a liquid composition prepared therefrom that has excellent liquid physical properties such as dispersibility. An object of the present invention is to provide a method for highly surface-modifying a molded article of a tetrafluoroethylene-based polymer to improve its surface properties, and to provide a highly surface-modified molded article of a tetrafluoroethylene-based polymer. [Means for solving the problem]

[0010] The present invention has the following aspects. <1> A method for producing a surface-modified tetrafluoroethylene polymer, comprising subjecting a tetrafluoroethylene polymer to a plasma treatment in an atmosphere near atmospheric pressure to obtain a surface-modified tetrafluoroethylene polymer. <2> A method for producing a modified powder, comprising subjecting a powder of a tetrafluoroethylene-based polymer to plasma treatment in an atmosphere near atmospheric pressure to modify the surface of the powder. <3> The powder is subjected to a plasma treatment in an atmosphere containing a reducing gas having hydrogen atoms at approximately atmospheric pressure, thereby obtaining a powder formed by introducing hydrogen atoms into the tetrafluoroethylene-based polymer. <2> Manufacturing method. <4> The plasma treatment is carried out in an atmosphere shielded from air. <2> or <3> Manufacturing method. <5> Before the plasma treatment, the powder is subjected to a plasma treatment in an atmosphere containing a rare gas. <2> from <4> Manufacturing method. <6> The atmosphere contains at least one gas selected from the group consisting of a reducing gas having hydrogen atoms, a vinyl compound, and a vinylidene compound. <2> from <5> Manufacturing method. <7> The atmosphere further contains a rare gas. <2> from <6> Manufacturing method. <8> The pressure near atmospheric pressure is 0.08 to 0.12 MPa. <2> from <7> Manufacturing method. <9> The powder has an average particle size of 50 μm or less. <2> from <8> Manufacturing method. <10> The tetrafluoroethylene-based polymer has a fluorine content of 70 to 76% by mass. <2> from <9> Manufacturing method. <11> The tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom. <2> from <10> Manufacturing method. <12> the above <2> from <11> A liquid composition comprising a modified powder obtained by any one of the manufacturing methods above and a liquid dispersion medium, in which the modified powder is dispersed. <13> The modified powder has an average particle size of 50 μm or less. <12> A liquid composition. <14> The tetrafluoroethylene-based polymer has a fluorine content of 70 to 76% by mass. <12> or <13> A liquid composition. <15> The tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom. <12> from <14> A liquid composition. <16> A method for producing a molded article having a surface layer containing a tetrafluoroethylene-based polymer at least in part, the surface layer of which is plasma-treated in an atmosphere containing a reducing gas having hydrogen atoms at near atmospheric pressure, the method comprising the steps of: <17> The plasma treatment is carried out in an atmosphere shielded from air. <16> Manufacturing method. <18> Before the plasma treatment, the surface layer is subjected to a plasma treatment in an atmosphere not containing a reducing gas. <16> or <17> Manufacturing method. <19> The reducing gas is hydrogen gas, ammonia gas, or hydrocarbon gas. <16> from <18> Manufacturing method. <20> The atmosphere of the plasma treatment further contains nitrogen gas or a rare gas. <16> from <19> Manufacturing method. <21> The pressure near atmospheric pressure is 0.08 to 0.12 MPa. <16> from <20> Manufacturing method. <22> The molded article having at least a surface layer containing a tetrafluoroethylene-based polymer is a film of a tetrafluoroethylene-based polymer or a laminate having a substrate layer and a layer of a tetrafluoroethylene-based polymer. <16> from <21> Manufacturing method. <23> The fluorine content of the tetrafluoroethylene-based polymer is 70 to 76 mass%. <16> from <22> Manufacturing method. <24> The tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom. <16> from <23> Manufacturing method. <25> A molded article containing a tetrafluoroethylene-based polymer, which has a modified layer on at least a part of its surface formed by introducing hydrogen atoms into the tetrafluoroethylene-based polymer, wherein the modified layer has a maximum height of a peak between 284 eV and 286 eV in a region from the surface to a depth of 1 nm as measured by X-ray photoelectron spectroscopy that is 0.2 times or more the maximum height of a peak between 289 eV and 295 eV in said region, and the fluorine atom content in said region is 55% or less. <26> The fluorine content of the tetrafluoroethylene-based polymer is 70 to 76 mass%. <25> Molded products. <27> The tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom. <25> or <26> Molded product. <28> The thickness of the modified layer is less than 1000 nm. <25> from <27> Molded product. <29> The molded article is a film of a tetrafluoroethylene-based polymer or a laminate having a substrate layer and a layer of a tetrafluoroethylene-based polymer. <25> from <27> Molded products. [Effects of the Invention]

[0011] According to the present invention, highly modified tetrafluoroethylene-based polymers can be produced. According to the present invention, a modified powder of a tetrafluoroethylene-based polymer having excellent wettability and dispersibility can be produced without impairing the physical properties of the tetrafluoroethylene-based polymer, and a liquid composition having excellent liquid properties can be easily produced from the modified powder. From such a liquid composition, a molded product (layered molded product, single film, etc.) having the physical properties of the tetrafluoroethylene-based polymer and excellent adhesiveness can be easily produced. According to the present invention, it is possible to produce a molded article of a tetrafluoroethylene-based polymer having, on at least a part of its surface, a stable modified layer formed by efficient introduction of hydrogen atoms into the tetrafluoroethylene-based polymer. Furthermore, it is possible to obtain a molded article of a tetrafluoroethylene-based polymer that has the physical properties of the tetrafluoroethylene-based polymer as a whole and has improved surface physical properties such as adhesiveness. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following terms have the following meanings: A "tetrafluoroethylene-based polymer" is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The "glass transition temperature (Tg) of a polymer" is a value measured by analyzing a polymer using dynamic mechanical analysis (DMA). The "melting temperature (melting point) of a polymer" is the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). "(Meth)acrylate" is a general term for acrylate and methacrylate. "D50" is the average particle size of a powder, and is the cumulative 50% diameter of the powder volume determined by laser diffraction / scattering. In other words, the particle size distribution of the powder is measured by laser diffraction / scattering, and a cumulative curve is calculated with the total volume of the powder group as 100%. D50 is the particle size at the point on the cumulative curve where the cumulative volume is 50%. "D90" is the cumulative volume particle size of the powder, which is the volume-based cumulative 90% diameter of the powder that is determined in the same manner. The term "unit based on a monomer" refers to an atomic group based on the monomer formed by polymerization of the monomer. The unit may be a unit formed directly by the polymerization reaction, or may be a unit in which a part of the unit is converted into a different structure by treating the polymer. Hereinafter, a unit based on monomer a may also be simply referred to as a "monomer a unit."

[0013] The production method of the present invention (hereinafter also referred to as "this method") is a method for producing a modified F polymer, in which a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") is subjected to plasma treatment in an atmosphere near atmospheric pressure to obtain a modified F polymer.

[0014] The first aspect of this method (hereinafter also referred to as Method 1) is a method for producing a modified powder in which the F polymer is a powder (hereinafter also referred to as raw powder), and the raw powder is plasma-treated in an atmosphere near atmospheric pressure to modify the surface of the powder.

[0015] The modified powder preferably has a modified layer formed on the surface by modifying the F polymer, and more preferably the modified layer is a modified layer formed by introducing hydrogen atoms into the F polymer, or a modified layer formed by introducing a polymer of a vinyl compound or vinylidene compound into the F polymer.

[0016] The modified layer formed by introducing hydrogen atoms into the F polymer has a maximum height of a peak (hereinafter also referred to as "Peak H") between 284 eV and 286 eV in the region from the surface to a depth of 1 nm, as measured by X-ray photoelectron spectroscopy (hereinafter also referred to as "ESCA"), which is preferably at least 0.2 times, and more preferably at least 1 time, the maximum height of a peak (hereinafter also referred to as "Peak F") between 289 eV and 295 eV in the same region.

[0017] Surface measurements by ESCA are performed using a Quantera II (ULVAC-PHI). The X-ray source is a monochromated AlKα beam at 100 W. An ion gun and a neutralization gun with a barium oxide emitter are used to prevent charging of the sample surface. The photoelectron detection area is 100 μmφ, the photoelectron detection angle is 45 degrees, and the pass energy is 55 eV. The fluorine atom content can be calculated from the various peak intensities (N1s, O1s, C1s, and F1s orbitals) detected by the measurement. The depth from the surface can be determined based on the sputtering rate of the SiO2 sputtered film using C60 ions.

[0018] Peak H and Peak F are, in that order, a photoelectron peak (C1s) based on the 1s orbital of a carbon atom and a photoelectron peak (F1s) based on the 1s orbital of a fluorine atom. In other words, Peak H can be considered to be a peak derived from a single bond between a carbon atom and a hydrogen atom (C-H bond), and Peak F can be considered to be a peak derived from a single bond between a carbon atom and a fluorine atom (C-F bond). In addition to Peak H and Peak F, the above region may also contain a photoelectron peak (O1s) based on the 1s orbital of oxygen atoms and a photoelectron peak (N1s) based on the 1s orbital of nitrogen atoms (hereinafter also referred to as "other peaks").

[0019] The content ratio of fluorine atoms in the region [atm %] is preferably 55% or less, and more preferably 40% or less. The content of fluorine atoms is a value calculated by the following procedure. In ESCA, the background is subtracted from the range including the C1s photoelectron peak, O1s photoelectron peak, N1s photoelectron peak, and F1s photoelectron peak, and the peak intensity of each element (four elements: carbon atom, oxygen atom, nitrogen atom, and fluorine atom) is calculated. Corrected values ​​of the peak intensities were calculated for each of the four elements by dividing the peak intensity by the relative sensitivity coefficient specific to that element, and the ratio of the peak intensity (corrected value) of fluorine atoms to the total corrected values ​​was defined as the "fluorine atom content ratio."

[0020] The maximum height of the peak H on the surface of the raw powder is preferably less than 0.2 times the maximum height of the peak F, and more preferably 0.1 times or less. Furthermore, the surface of the raw powder preferably contains more than 55% fluorine atoms, and more preferably 60% or more. According to this method 1, a modified powder can be obtained that has improved surface properties (wettability, etc.) and dispersion stability without impairing the overall physical properties (electrical properties, etc.) of the F polymer. The mechanism of action is not entirely clear, but is thought to be as follows.

[0021] Since the plasma treatment in Method 1 is carried out at near atmospheric pressure, in other words, in an atmosphere with high gas density, it is believed that the gas contained in the atmosphere is partially converted into plasma. Furthermore, it is believed that the gas contained in the atmosphere not only becomes plasma itself, but also forms electrically neutral radicals and the like, which become modified components of the polymer. That is, in the plasma treatment in Method 1, the plasma treatment proceeds in such a state, and therefore it is thought that the F polymer is likely to be efficiently modified.

[0022] For example, if a gas contains a reducing gas containing hydrogen atoms, it not only becomes plasma itself, but also converts into electrically neutral hydrogen radicals. As a result, the hydrogen radicals act on the C—F bonds of the F polymer activated by the plasma, modifying the polymer. In particular, the atomic radius of hydrogen atoms and that of fluorine atoms are similar, making this effect even more likely to be enhanced.

[0023] As a result, it is believed that non-fluorine atoms or molecules can be efficiently introduced into the F polymer contained on the surface of the raw powder according to Method 1. In addition, scission of the F polymer on the surface of the raw powder by plasma is suppressed, and its molecular weight is prevented from decreasing, which makes it easier to stabilize the surface state of the modified F polymer. It is believed that due to this mechanism of action, Method 1 can produce a powder that has the physical properties of F polymer and excellent surface properties, and from which a liquid composition with excellent dispersibility can be easily prepared.

[0024] The fluorine content of the F polymer is preferably 70 to 76% by mass. An F polymer with such a high fluorine content has excellent physical properties (electrical properties, etc.) of an F polymer, but has particularly low polarity, resulting in poor surface properties (wettability, etc.) of the raw powder. According to this method, even with such raw powder, a modified powder with improved surface properties can be obtained without impairing the overall physical properties of the F polymer.

[0025] The melting temperature of the F polymer is preferably 180°C or higher, preferably 200 to 325°C, and more preferably 280 to 320°C. The glass transition point of the F polymer is preferably 30 to 150°C, and more preferably 75 to 125°C. The F polymer is preferably polytetrafluoroethylene (PTFE), a polymer (PFA) containing TFE units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units), or a copolymer (FEP) containing units based on TFE and hexafluoropropylene, with PFA or FEP being particularly preferred. These polymers may further contain units based on other comonomers.

[0026] As the PAVE, CF2=CFOCF3, CF2=CFOCF2CF3 or CF2=CFOCF2CF2CF3 (PPVE) is preferred, with PPVE being more preferred. The F polymer preferably has an atomic group containing an oxygen atom. According to this method, a modified molded product having improved surface properties can be easily obtained without impairing the physical properties of the F polymer based on such an atomic group.

[0027] The atomic group may be contained in a monomer unit in the F polymer or in a terminal group of the main chain of the polymer. The latter embodiment includes an F polymer having the atomic group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc. The atomic group containing an oxygen atom is preferably a hydroxyl group-containing group or a carbonyl group-containing group, and particularly preferably a carbonyl group-containing group.

[0028] The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH or -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-), with an acid anhydride residue being particularly preferred.

[0029] When the F polymer has a carbonyl group-containing group, the number of carbonyl group-containing groups in the F polymer is 1×10 6 Preferably, the number per unit is 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 method described in WO 2020 / 145133.

[0030] Suitable embodiments of the F polymer include polymer (1) containing TFE units and PAVE units and having an atomic group containing an oxygen atom, or polymer (2) containing TFE units and PAVE units, containing 2.0 to 5.0 mol% PAVE units based on the total monomer units, and having no atomic group containing an oxygen atom. These polymers form microspherulites in the molded product, making the formation of a modified layer by Method 1 more likely to proceed.

[0031] Polymer (1) is preferably a polymer containing TFE units, PAVE units, and monomer units having a hydroxyl group-containing group or a carbonyl group-containing group, and preferably contains 90 to 99 mol% TFE units, 0.5 to 9.97 mol% PAVE units, and 0.01 to 3 mol% units based on the above monomers, based on all units. The monomer is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (also known as himic acid anhydride; hereinafter also referred to as "NAH"). Specific examples of polymer (1) include the polymers described in WO 2018 / 16644.

[0032] The polymer (2) is composed of only 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 the total monomer 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 the total monomer units. The polymer (2) does not have an atomic group containing an oxygen atom when the number of carbon atoms constituting the polymer main chain is 1×10 6 This means that the number of atomic groups containing oxygen atoms in the polymer is less than 500 per unit. The number of atomic groups containing oxygen atoms is preferably 100 or less, and more preferably less than 50. The lower limit of the number of atomic groups containing oxygen atoms is usually 0.

[0033] Polymer (2) may be produced using a polymerization initiator or chain transfer agent that does not generate an atomic group containing an oxygen atom as the terminal group of the polymer chain, or may be produced by fluorinating an F polymer having an atomic group containing an oxygen atom. Fluorination methods include methods using fluorine gas (see, for example, JP 2019-194314 A).

[0034] The raw powder is preferably made of F polymer, and the content of F polymer in the raw powder is preferably 80% by mass or more, and more preferably 100% by mass. Other components that may be contained in the raw powder include heat-resistant resins such as aromatic polyester, polyamideimide, thermoplastic polyimide, polyphenylene ether, and polyphenylene oxide. The D50 of the raw powder is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 8 μm or less. The D50 of the raw powder is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 1 μm or more. The D90 of the raw powder is preferably less than 100 μm, and more preferably 90 μm or less. If the D50 and D90 of the raw powder are within these ranges, the surface area is increased, making it easier to modify the raw powder.

[0035] The plasma treatment in Method 1 is carried out in an atmosphere near atmospheric pressure. Near atmospheric pressure means a pressure of 0.1±0.02 MPa. From the viewpoints of controlling the generation of plasma in the atmosphere and enhancing the action of hydrogen reducing species, the pressure is preferably 0.08 to 0.12 MPa, and from the viewpoints of blocking outside air and suppressing the inclusion of components that inhibit the plasma treatment, the pressure is more preferably atmospheric pressure (0.101325 MPa) or higher but 0.12 MPa or lower.

[0036] The plasma treatment in Method 1 is preferably carried out in an atmosphere containing a gas containing one of a reducing gas having hydrogen atoms, a vinyl compound, and a vinylidene compound. The reducing gas having hydrogen atoms is preferably hydrogen gas, ammonia gas, or a hydrocarbon gas, more preferably hydrogen gas, ammonia gas, methane gas, or ethylene gas. From the viewpoint of its ability to function as a hydrogen reducing species in the above-mentioned mechanism of action, hydrogen gas or ammonia gas is even more preferred, and hydrogen gas is most preferred. Two or more reducing gases may be used in combination.

[0037] Vinyl compounds are compounds with the formula CH2=CHR 1 A compound represented by the formula (wherein R 1 represents a monovalent organic group. Specific examples thereof include acrylic acid, acrylate, acrylamide, α-olefin (propylene, 1-butene, etc.), vinyl ether, vinyl ester, allyl ether, vinyl chloride, and styrene. The vinyl compound is preferably acrylic acid or acrylate. Two or more vinyl compounds may be used in combination. A vinylidene compound is a compound represented by the formula CH2=CHR 2 R 3 A compound represented by the formula (wherein R 2 and R 3 each independently represents a monovalent organic group. Specific examples thereof include methacrylic acid, methacrylate, methacrylamide, and vinylidene chloride. The vinyl compound is preferably methacrylic acid or methacrylate. Two or more vinylidene compounds may be used in combination.

[0038] The atmosphere in the plasma treatment may consist of only one of the above gases, or may further contain other gases, and from the viewpoint of controlling the generation of plasma, it is preferable that the atmosphere contains a reducing gas and further other gases. The other gases are preferably water vapor, nitrogen gas, or a rare gas, and from the viewpoint of the above, a rare gas is more preferable, helium gas, argon gas, or neon gas is further preferable, and argon gas is most preferable.

[0039] The concentration of the reducing gas having hydrogen atoms or the gas containing one of a vinyl compound and a vinylidene compound in the atmosphere during plasma treatment is preferably more than 99% by volume, more preferably 99.5% by volume or more, and even more preferably 99.9% by volume or more. The upper limit of the concentration of the gas is 100% by volume. When the atmosphere contains the gas and a rare gas, the total concentration of the gas and the rare gas may be within this range. When the gas concentration in the atmosphere is within this range, the above-mentioned mechanism of action is likely to be enhanced. Such an atmosphere can be created by using a high-purity gas or by a method of shielding air from the atmosphere in the plasma treatment described below.

[0040] The gas composition of the atmosphere preferably contains 0.1% by volume or more of a reducing gas, more preferably more than 1% by volume. The gas composition of the atmosphere preferably contains 100% by volume or less of a reducing gas, more preferably less than 50% by volume. Specific examples of suitable gas compositions of the atmosphere include a gas composition containing a rare gas and hydrogen gas, in that order, at 75 to 99.5% by volume and 0.5 to 25% by volume, and a gas composition containing a rare gas and ammonia gas, in that order, at 75 to 99% by volume and 1 to 25% by volume. Furthermore, it is preferable that these gas compositions do not contain oxygen gas.

[0041] The plasma treatment in Method 1 is preferably carried out in a gas atmosphere containing a reducing gas having hydrogen atoms, or in a gas atmosphere containing the vinyl compound or vinylidene compound. In the former case, a modified powder is obtained in which hydrogen atoms are introduced onto the surface of the modified powder, and in the latter case, a modified powder is obtained in which polyvinyl compound chains or polyvinylidene compound chains are introduced onto the surface of the modified powder. Examples of vinyl or vinylidene compounds include acrylic acid, methacrylic acid, methyl acrylate, and methyl methacrylate, with acrylic acid being preferred, as this facilitates the introduction of dense (meth)acrylic and (meth)acrylate chains onto the surface of the raw powder.

[0042] In this case, the concentration (by volume) of the vinyl compound or vinylidene compound in the gas atmosphere is preferably 1200 to 1400 ppm. In this case, the gas atmosphere preferably further contains other gases from the viewpoint of controlling the generation of plasma. The preferred embodiments of the other gases are the same as those of the other gases in the atmosphere containing a reducing gas having hydrogen atoms, as described above. When the vinyl compound or vinylidene compound is in a liquid or solid state, it may be heated to be used in a gaseous state, or may be bubbled to generate a gas.

[0043] In order to prevent the inclusion of components that inhibit the plasma treatment, the plasma treatment in Method 1 is preferably carried out in an atmosphere shielded from air (particularly oxygen gas), and more preferably in an atmosphere completely shielded from air. Methods for blocking air include a method of making the atmospheric pressure during plasma processing equal to or higher than atmospheric pressure, and a method of suppressing air intrusion by providing an obstacle wall in the plasma processing apparatus.

[0044] The plasma treatment method in Method 1 includes a method in which the raw powder is placed in a plasma chamber in which a raw material gas such as a reducing gas is sealed to create atmospheric conditions, and a method in which the raw powder is placed between opposing electrodes, and plasma discharge is created while a raw material gas is supplied to create atmospheric conditions. The voltage during plasma discharge is preferably 5 to 20 kV. The frequency of the power supply during plasma discharge is preferably 50 Hz to 100 MHz. The discharge power density relative to the electrode area during plasma discharge is preferably 1 to 400 W·min / cm. 2 When plasma discharge is performed under the above discharge conditions, the modified molded product tends to have excellent adhesiveness. The discharge time during plasma discharge is preferably 0.1 seconds to 300 minutes for the target raw powder.

[0045] The temperature during plasma discharge is preferably 0 to 300°C, more preferably 10 to 50°C. If plasma discharge is performed under such conditions, hydrogen atoms, or polyvinyl compound chains or polyvinylidene compound chains are more likely to be introduced into the F polymer present on the surface of the raw powder containing the F polymer on its surface, making it easier to obtain a modified powder with highly improved surface properties such as wettability without impairing the physical properties of the F polymer as a whole. In particular, if the temperature during plasma discharge is within the above range, a more selective and dense modified layer is likely to be formed.

[0046] In Method 1, before the raw powder is plasma-treated, the surface of the raw powder is preferably plasma-treated in an atmosphere containing a rare gas. Such pretreatment results in a more highly modified powder. The atmosphere preferably does not contain a reducing gas.

[0047] The modified powder obtained by Method 1 has improved surface properties such as wettability, and is highly dispersible in liquid dispersion media. The sedimentation rate of the modified powder is preferably 60% or less, more preferably 50% or less, and even more preferably 40% or less. The sedimentation rate is the value calculated using the following formula when the modified powder is dispersed in the target liquid dispersion medium, and 1.3 μL of the dispersion containing 5% by mass of the modified powder is measured into a 1.5 μL microtube (model number: 1-7521-01, manufactured by AS ONE Corporation) and centrifuged at 13,000 rpm in a centrifuge for 5 minutes. If no sedimentation occurs, the sedimentation rate is considered to be 0%. Sedimentation rate [%] = (height of sedimented component / height of total dispersion) x 100

[0048] The liquid dispersion medium may be water or a non-aqueous dispersion medium, and the non-aqueous dispersion medium is preferably one or more liquid compounds selected from the group consisting of amides, ketones, and esters, and more preferably N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, or cyclopentanone.

[0049] It is preferable to prepare a liquid composition containing the modified powder obtained by Method 1 and a liquid composition, in which the modified powder is dispersed (hereinafter also referred to as "the composition").

[0050] The content of the modified powder in this composition is preferably 1 to 60% by mass, more preferably 10 to 50% by mass. The content of the liquid dispersion medium is preferably 40 to 99% by mass, more preferably 50 to 90% by mass. This composition may further contain an inorganic filler or another resin (polymer) different from the F polymer. Because the modified powder has excellent wettability and dispersibility, this composition is likely to have excellent dispersion stability even in such cases. In particular, even if the other resin contains PTFE, it is easy to prepare a liquid composition with high dispersibility. This liquid composition is preferably prepared by mixing the modified powder with an aqueous dispersion containing PTFE powder.

[0051] The viscosity of the composition is more preferably 50 to 1000 mPa·s, and more preferably 75 to 500 mPa·s. In this case, the composition has excellent coatability. The thixotropy ratio of the composition is preferably 1.0 to 2.2. In this case, the composition has excellent coatability and homogeneity. The thixotropy ratio is calculated by dividing the viscosity of the composition measured at a rotation speed of 30 rpm by the viscosity of the composition measured at a rotation speed of 60 rpm.

[0052] This composition has excellent dispersion stability and can form molded articles that have excellent crack resistance and strong adhesion to substrates without impairing the physical properties of the F polymer. A laminate having a substrate layer and an F layer can be produced by applying this composition to the surface of a substrate and heating it to form a polymer layer containing the F polymer (hereinafter also referred to as "F layer (1)").

[0053] In producing the laminate, it is sufficient that the F layer (1) is formed on at least one surface of the substrate, and the F layer (1) may be formed on only one surface of the substrate, or on both surfaces of the substrate. The surface of the substrate may be surface-treated with a silane coupling agent or the like. When applying the composition, coating 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 can be used.

[0054] The F layer (1) is preferably formed by removing the dispersion medium by heating and then baking the polymer by heating. It is particularly preferable to form the F layer (1) by heating the substrate to a temperature at which the dispersion medium volatilizes (100 to 300°C) and then further heating the substrate to a temperature range at which the polymer bakes (300 to 400°C). That is, the F layer (1) preferably contains a baked product of PTFE and PFA. The thickness of the F layer (1) is preferably 0.1 μm or more, more preferably 1 μm or more. The upper limit of the thickness is 100 μm. Within this thickness range, an F layer with excellent crack resistance can be easily formed. The peel strength between the F layer (1) and the substrate layer is preferably 3 N / cm or more, more preferably 10 N / cm or more, and even more preferably 15 N / cm or more. The above peel strength is preferably 100 N / cm or less. By using this composition, such a laminate can be easily formed without impairing the physical properties of the PTFE in the F layer.

[0055] Examples of the substrate material include copper, aluminum, iron, glass, resin, silicon, and ceramics. The substrate may have a flat, curved, or textured shape, and may be in the form of a foil, plate, film, or fiber. Specific examples of the laminate include a metal-clad laminate having a metal foil and an F layer (1) on at least one surface of the metal foil, and a multilayer film having a polyimide film and an F layer (1) on both surfaces of the polyimide film. These laminates have excellent physical properties such as electrical properties, and are suitable as printed circuit board materials. Specifically, such laminates can be used to manufacture flexible printed circuit boards and rigid printed circuit boards.

[0056] By impregnating a woven fabric with this composition and drying it by heating, an impregnated woven fabric is obtained in which the F polymer has been impregnated into the woven fabric. The impregnated woven fabric can also be said to be a coated woven fabric in which the woven fabric is coated with an F layer (1). The woven fabric is preferably a glass fiber woven fabric, a carbon fiber woven fabric, an aramid fiber woven fabric, or a metal fiber woven fabric, and more preferably a glass fiber woven fabric or a carbon fiber woven fabric. The woven fabric may be treated with a silane coupling agent to enhance adhesion to the F layer (1). The total content of the F polymer in this woven fabric is preferably 30 to 80 mass%. Methods for impregnating the woven fabric with this composition include immersing the woven fabric in the composition and applying the composition to the woven fabric.

[0057] When drying the woven fabric, the polymer may be calcined. For example, the woven fabric may be passed through a forced-air drying oven in an atmosphere of 300 to 400°C. The drying of the woven fabric and the calcination of the polymer may be carried out in one step. The impregnated woven fabric has excellent properties, such as high adhesion (adhesion) between the F layer (1) and the woven fabric, high surface smoothness, and little distortion. By thermocompression bonding such a woven fabric and a metal foil, a metal-clad laminate with high peel strength and resistance to warping can be obtained, which is suitable for use as a printed circuit board material.

[0058] Alternatively, a woven fabric impregnated with the present composition may be placed on the surface of a substrate, heated, and dried to form an impregnated woven fabric layer containing the F polymer and the woven fabric, thereby producing a laminate in which the substrate and the impregnated woven fabric layer are laminated in this order. The form is not particularly limited, and by applying a woven fabric impregnated with the present dispersion to part or all of the inner wall surface of a component such as a tank, pipe, or container, and then heating the component while rotating, an impregnated woven fabric layer can be formed on part or all of the inner wall surface of the component. This production method is also useful as a method for lining the inner wall surface of components such as tanks, pipes, and containers.

[0059] As explained by the mechanism of action described above, the present composition has excellent dispersion stability and can be efficiently impregnated into porous or fibrous materials. Examples of such porous or fibrous materials include materials other than the woven fabrics described above, specifically, plate-like, columnar, or fibrous materials. These materials may be pretreated with a curable resin, a silane coupling agent, or the like, and may further be filled with an inorganic filler or the like. These materials may also be twisted together to form threads, cables, or wires. When twisting, an intervening layer made of another polymer, such as polyethylene, may be disposed. An example of producing a molded article by impregnating such a material with the present composition is impregnating a fibrous material carrying a curable resin or its cured product with the present composition.

[0060] Examples of fibrous materials include high-strength, low-elongation fibers such as carbon fiber, aramid fiber, and silicon carbide fiber. Preferred curable resins include thermosetting resins such as epoxy resin, unsaturated polyester resin, and polyurethane resin. A specific example of such an embodiment is a composite cable formed by impregnating a cable made of twisted carbon fibers carrying a thermosetting resin with the present composition and then heating the cable to bake the F polymer. Such composite cables are useful as cables for large structures, ground anchors, oil drilling, cranes, cableways, elevators, agriculture, forestry, and fisheries, and for slings.

[0061] The second embodiment of the manufacturing method of the present invention (hereinafter also referred to as "Method 2") is a method for manufacturing a modified molded product having a modified layer formed on at least a part of its surface by introducing hydrogen atoms into the F polymer, by subjecting the surface layer of a molded product (hereinafter also referred to as the original molded product) having at least a part of its surface layer containing an F polymer to plasma treatment in an atmosphere at near atmospheric pressure containing a reducing gas having hydrogen atoms.

[0062] In Method 2, the maximum height of Peak H of the modified layer is preferably 0.2 times or more, more preferably 1 time or more, the maximum height of Peak F. Peaks H and F are the same as above.

[0063] The content ratio of fluorine atoms in the region [atm %] is preferably 55% or less, and more preferably 40% or less. The content of fluorine atoms and the procedure are the same as above.

[0064] The maximum height of the peak H on the surface of the original molded article is preferably less than 0.2 times the maximum height of the peak F, and more preferably 0.1 times or less. The surface of the original molded article preferably has a fluorine atom content of more than 55%, more preferably 60% or more.

[0065] According to this method 2, a modified molded article containing an F polymer can be obtained, which has a modified layer on at least a part of its surface that has excellent surface properties (wettability, etc.) without impairing the overall physical properties (electrical properties, etc.) of the F polymer. The mechanism of action is not entirely clear, but is thought to be as follows. Since the plasma treatment in Method 2 is carried out at near atmospheric pressure, in other words, in an atmosphere with high gas density, it is believed that the gas contained in the atmosphere is partially converted into plasma. Furthermore, it is believed that the reducing gas containing hydrogen atoms contained in the atmosphere not only becomes plasma itself but also becomes electrically neutral hydrogen radicals.

[0066] In other words, it is believed that the plasma treatment in Method 2 is in a state where plasma and hydrogen radicals exist. Because the plasma treatment proceeds in this state, it is believed that the hydrogen radicals act on the C—F bonds of the F polymer activated by the plasma, forming a modified layer. In particular, the atomic radius of the hydrogen atom and the atomic radius of the fluorine atom are similar, making this action more likely to be enhanced, and it is believed that the modified layer was formed efficiently.

[0067] As a result, it is believed that Method 2 forms a modified layer in which hydrogen atoms are efficiently introduced into the F polymer contained in the surface of the molded article. In addition, the action of hydrogen radicals suppresses the cleavage of the F polymer by plasma, preventing its molecular weight from decreasing, which is thought to result in the formation of a highly stable modified layer. Due to this mechanism of action, according to Method 2, a modified layer is formed on the surface of a molded article containing an F polymer in the surface layer by introducing hydrogen atoms into the F polymer, and a modified molded article is obtained that is an F polymer molded article that has the physical properties and surface properties of the F polymer as a whole.

[0068] The thickness of the modified layer in the modified molded product is preferably less than 1000 nm, more preferably 500 nm or less, and particularly preferably 100 nm or less. The thickness of the modified layer is preferably 1 nm or more. Note that the thickness of the modified layer refers to the length perpendicular to the plane when the modified layer has a planar extension, and refers to the shortest length when the modified layer does not have a planar extension.

[0069] The definition and scope of the F polymer in Method 2 are as described above.

[0070] The original molded product in Method 2 is a molded product containing an F polymer in its surface layer. The surface layer of a molded product is a region extending from the surface of the molded product to a depth of at least approximately 1000 nm in the thickness direction of the molded product, and the molded product to which Method 2 is applied is a molded product containing an F polymer in its surface layer. As mentioned above, the thickness of a molded product refers to the length perpendicular to the plane if the molded product has a planar extent, and refers to the shortest length if the molded product does not have a planar extent. The original molded article may contain the F polymer throughout, or may contain the F polymer only in the surface layer. In the latter case, the F polymer may be contained in the entire surface layer, or may be contained in a part of the surface layer. The surface shape of the original molded product may be smooth or uneven.

[0071] The original molded article is preferably a molded article having a surface layer containing an F polymer, and is preferably a sheet-like molded article having a surface layer portion containing an F polymer. The thickness of the layer containing the F polymer in the surface layer is preferably 1 μm or more, more preferably 5 μm or more, and particularly preferably 10 μm or more. The thickness of the layer containing the F polymer is preferably 1 mm or less. If the original molded product has a layer portion containing the F polymer in the surface layer of such a thickness, this method makes it easy to obtain a modified molded product that has the physical properties and surface properties of the F polymer in the entire molded product.

[0072] The original molded product is preferably an F polymer film or a laminate having a substrate layer and a layer containing an F polymer (hereinafter also referred to as "F layer (2)") and having an F layer (2) on the surface. In an F polymer film or a laminate having an F layer (2) on both sides, this method may be applied to both sides or only one side. The F polymer film preferably contains the F polymer as a main component, and preferably contains more than 50 mass % and 100 mass % or less of the F polymer.

[0073] Other components that can be contained in the F polymer film include heat-resistant resins such as epoxy resins, maleimide resins, urethane resins, polyimide resins, polyamide-imide resins, polyphenylene ether resins, polyphenylene oxide resins, and liquid crystal polyester resins; inorganic fillers such as nitride fillers, silica fillers, mica fillers, clay fillers, and talc fillers; carbon fillers such as carbon fibers; and elastomers.

[0074] The substrate layer in the laminate is preferably a resin substrate layer or a metal substrate layer. The metal substrate layer may be in the form of a metal foil, and examples of the material thereof include copper, nickel, aluminum, titanium, and alloys thereof. Examples of the resin substrate include a resin film, and examples of the material thereof include polyimide, polyarylate, polysulfone, polyarylsulfone, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, and liquid crystalline polyesteramide. Examples of the resin substrate also include a prepreg, which is a precursor of a fiber-reinforced resin substrate.

[0075] Suitable embodiments of the laminate include a metal-clad laminate having a metal foil and an F layer (2) formed on at least one surface thereof, and a multilayer film having a resin film and an F layer (2) formed on at least one surface thereof. The metal foil in the metal clad laminate is preferably copper foil. Such metal clad laminates are particularly useful as printed circuit board materials. The resin film in the multilayer film is preferably polyimide film. Such multilayer films are useful as wire coating materials and printed circuit board materials.

[0076] The plasma treatment in Method 2 is carried out in an atmosphere containing a reducing gas having hydrogen atoms. The reducing gas having hydrogen atoms is preferably hydrogen gas, ammonia gas, or a hydrocarbon gas, more preferably hydrogen gas, ammonia gas, methane gas, or ethylene gas, and from the viewpoint of its ability to act as a hydrogen reducing species in the above-mentioned mechanism of action, hydrogen gas or ammonia gas is even more preferable, and hydrogen gas is most preferable. One type of reducing gas may be used alone, or two or more types may be used in combination.

[0077] The atmosphere in the plasma treatment may consist of only a reducing gas or may further contain other gases, and from the viewpoint of controlling the generation of plasma, it is preferable that the atmosphere contains a reducing gas and other gases. The other gases are preferably water vapor, nitrogen gas, or a rare gas, and from the viewpoint of controlling the generation of plasma, more preferably a rare gas, further preferably helium gas, argon gas, or neon gas, and most preferably argon gas.

[0078] The concentration of the reducing gas in the atmosphere during plasma treatment (when the atmosphere contains the gas and a rare gas, the total concentration of the gas and the rare gas) is preferably more than 99% by volume, more preferably 99.5% by volume or more, and even more preferably 99.9% by volume or more. The upper limit of the gas concentration is 100% by volume. When the gas concentration in the atmosphere is within this range, the above-mentioned mechanism of action is likely to be enhanced. Such an atmosphere can be formed by using a high-purity gas or by a method of shielding air from the atmosphere during plasma treatment, which will be described later.

[0079] The gas composition of the atmosphere preferably contains 0.1% by volume or more of a reducing gas, more preferably more than 1% by volume. The gas composition of the atmosphere preferably contains 100% by volume or less of a reducing gas, more preferably less than 50% by volume. Specific examples of suitable gas compositions of the atmosphere include a gas composition containing a rare gas and hydrogen gas, in that order, at 75 to 99.5% by volume and 0.5 to 25% by volume, and a gas composition containing a rare gas and ammonia gas, in that order, at 75 to 99% by volume and 1 to 25% by volume. Furthermore, it is preferable that these gas compositions do not contain oxygen gas.

[0080] The plasma treatment in Method 2 is carried out in an atmosphere near atmospheric pressure. Near atmospheric pressure means a pressure of 0.1±0.02 MPa. From the viewpoints of controlling the generation of plasma in the atmosphere and enhancing the action of hydrogen reducing species, the pressure is preferably 0.08 to 0.12 MPa, and from the viewpoints of blocking outside air and suppressing the inclusion of components that inhibit the plasma treatment, the pressure is more preferably equal to or higher than atmospheric pressure (0.101325 MPa) and equal to or lower than 0.12 MPa.

[0081] In order to prevent the inclusion of components that inhibit the plasma treatment, the plasma treatment in Method 2 is preferably carried out in an atmosphere shielded from air, particularly oxygen gas, and more preferably in an atmosphere completely shielded from air. Methods for blocking air include a method of making the atmospheric pressure during plasma processing equal to or higher than atmospheric pressure, and a method of suppressing air intrusion by providing an obstacle wall in the plasma processing apparatus.

[0082] The plasma treatment method in Method 2 includes a method in which the original molded product is placed in a plasma chamber in which a raw material gas such as a reducing gas is sealed to create atmospheric conditions, and a method in which the original molded product is placed between opposing electrodes, and a plasma discharge is created while a raw material gas is supplied to create atmospheric conditions. The voltage during plasma discharge is preferably 5 to 20 kV. The frequency of the power supply during plasma discharge is preferably 50 Hz to 100 MHz. The discharge power density relative to the electrode area during plasma discharge is preferably 1 to 400 W·min / cm. 2 When plasma discharge is carried out under the above discharge conditions, the modified molded product tends to have excellent adhesiveness. The discharge time during plasma discharge is preferably 0.1 seconds to 300 minutes for the target original molded article.

[0083] The temperature during plasma discharge is preferably 0 to 300°C, more preferably 10 to 50°C. If plasma discharge is performed under such conditions, hydrogen atoms are more easily introduced into the F polymer present on the surface of a molded article containing an F polymer in its surface layer, making it easier to obtain a modified molded article with highly improved surface properties such as wettability without impairing the physical properties of the F polymer as a whole. In particular, if the temperature during plasma discharge is within the above range, a more selective and dense modified layer is likely to be formed.

[0084] In Method 2, before the plasma treatment of the base molded article, the surface of the base molded article may be plasma-treated in advance in an atmosphere that does not contain a reducing gas. If the surface of the base molded article is appropriately roughened by such treatment, the contact area between the surface of the molded article and the plasma in the plasma treatment of this method will be increased, making it easier to form a modified layer with a higher degree of hydrogen atom introduction. Such an atmosphere preferably contains a rare gas.

[0085] When the original molded product is the laminate described above and is to be further laminated with another substrate, the adhesive strength with the other substrate can be increased by applying method 2 to the F layer (2) of the original molded product to form a modified layer before lamination. For example, a liquid composition containing an F polymer powder is applied to a long substrate and heated to form an F layer (2) to prepare an original molded product, and method 2 is applied to the F layer (2) and further laminated with another long substrate by a roll-to-roll process, thereby easily obtaining a long composite substrate.

[0086] Furthermore, when the original molded product is a roll-shaped long laminate, the original molded product can be unwound from the roll, passed between opposing electrodes, and plasma discharged while supplying a raw material gas to achieve atmospheric conditions, thereby obtaining a modified molded product having a modified layer formed thereon. The obtained modified molded product may be sent directly to a lamination step with another substrate, or may be wound into a roll and then unwound again and sent to a lamination step with another substrate. From the viewpoint of process simplification, it is preferable to incorporate a discharge device for discharging the plasma into the lamination device so that the original molded product can be plasma-treated before the lamination step.

[0087] The modified molded article of the present invention (hereinafter also referred to as "the molded article") has a modified layer formed by introducing hydrogen atoms into an F polymer on at least a part of its surface, the modified layer being a layer in which the maximum height of the H peak is 0.2 times or more the maximum height of the F peak, and the content of fluorine atoms in the modified layer is 55% or less. The molded article is preferably produced by Method 2.

[0088] The embodiment of the F polymer in this molded product, including preferred embodiments, is the same as that in Method 1. The embodiment of the modified layer in this molded product and the state or shape of the surface of this molded product, including preferred embodiments, are the same as those in Method 2. Preferred embodiments of this molded product include a film having a modified layer on at least one surface of an F polymer film, a metal clad laminate having a metal foil and an F layer (2) formed on at least one surface thereof and having a modified layer on the surface of the F layer (2), and a multilayer film having a resin film and an F layer (2) formed on at least one surface thereof and having a modified layer on the surface of the F layer. When an F layer is formed on both sides of a metal clad laminate or when an F layer (2) is formed on both sides of a multilayer film, the modified layer may be present on both surfaces. In these embodiments, the F polymer film, metal foil, resin film and F layer (2) are the same as those of the present invention, including preferred embodiments. 1 This is the same as the embodiment in

[0089] This molded product has the physical properties of the F polymer throughout the entire molded product, as well as the surface properties resulting from its high polarity, and is particularly useful as a wire coating material and a printed circuit board material. For example, the dielectric constant of the F polymer film or F layer (2) having a modified layer is preferably 2.0 to 3.5, more preferably 2.0 to 3.0. The dielectric constant is measured using a split post dielectric resonator (SPDR) at a frequency of 10 GHz under an environment of 23°C ± 2°C and a relative humidity of 50 ± 5%. When the molded product is a multilayer film, the dielectric constant of the molded product is preferably 2.0 to 3.5, more preferably 2.0 to 3.0. The water contact angle of the outermost surface (modified layer) of the molded product is preferably 100° or less, more preferably 90° or less. The water contact angle of the outermost surface (modified layer) of the molded product is preferably 10° or more, more preferably 30° or more. The water contact angle is measured by the sessile drop method described in JIS R 3257:1999.

[0090] The surface of the molded article having the modified layer can be further laminated with another substrate. In this case, the peel strength at the interface between the molded article and the other substrate to be laminated is preferably 8 N / cm or more, more preferably 10 N / cm or more.

[0091] The method of laminating and adhering the molded product to other substrates includes a method using heat pressing. The heat pressing temperature is preferably below the melting point of the F polymer, more preferably below 300°C, and even more preferably below 240°C. The heat pressing temperature is preferably above 120°C, and even more preferably above 160°C. Since the molded product has a modified layer on its surface with excellent physical properties such as wettability, it can be laminated and adhered to other substrates at lower temperatures. Other substrates include prepreg, glass substrate, and ceramic substrate in addition to the above-mentioned metal substrate and resin substrate.

[0092] Examples of the structure of a laminate of the present molded product and another substrate include metal substrate / the present molded product having modified layers on both sides / another substrate layer / the present molded product having modified layers on both sides / metal substrate, metal substrate layer / another substrate layer / the present molded product having modified layers on both sides / another substrate layer / metal substrate layer, etc. Each layer may further contain glass cloth or a filler. Such laminates are useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry supplies, paints, cosmetics, and the like, and specifically as electric wire coating materials (aircraft electric wires, etc.), electrical insulating tape, insulating tape for oil drilling, materials for printed circuit boards, separation membranes (microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode binders (for lithium secondary batteries, for fuel cells, etc.), copy rolls, covers for furniture, automobile dashboards, home appliances, etc., sliding members (load bearings, sliding shafts, valves, bearings, gears, cams, belt conveyors, food transport belts, etc.), tools (shovels, files, saws, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, dies, toilets, and container coating materials.

[0093] Although the present method, methods 1 and 2, and the present molded product have been described above, the present invention is not limited to the configurations of the above-described embodiments. For example, in the configurations of the above embodiments, Method 1, Method 2, and Method 3 may have any other optional step added thereto, or may be replaced with any other optional step that produces a similar effect.Furthermore, in the configurations of the above embodiments, the present molded product may have any other optional component added thereto, or may be replaced with any other component that exhibits a similar function. [Example]

[0094] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Example 1] Example of production of modified powder and liquid composition The following raw materials were used: F Powder 1: Polymer 1 (melting point: 300°C, fluorine content: 71% by mass) containing 97.9 mol% TFE units, 2.0 mol% PPVE units, and 0.1 mol% NAH units (average particle size: 2.6 μm). F Powder 1 corresponds to Resin Powder (A) described in paragraph 0154 of WO 2018 / 016644. F Powder 2: Powder (average particle size: 4.3 μm) consisting of polymer 2 (melting point: 300°C, fluorine content: 71 mass%) containing 98.7 mol% of TFE units and 1.3 mol% of PPVE units. Polymer 1 has a carbonyl group-containing group with a main chain carbon number of 1 × 10 6 Polymer 2 has 1000 carbonyl group-containing groups per unit area, and the number of carbon atoms in the main chain is 1 × 10 6 There are 40 per piece.

[0095] [Example 1-1] Production example of modified powder 1 and liquid composition 1 F Powder 1 was uniformly placed in a plasma chamber equipped with a mechanism capable of generating plasma by dielectric barrier discharge, sandwiching a dielectric between a pair of opposing electrodes, and a stage for holding the powder. A mixed gas containing 95% by volume of Ar gas and 5% by volume of hydrogen gas was flowed into the chamber, and the chamber was shielded from the outside air. The total concentration of Ar gas and hydrogen gas in the chamber during plasma treatment was maintained at 99.9% by volume or more, the pressure in the chamber was maintained at 0.1 MPa, and the temperature in the chamber was maintained at 25°C. Plasma discharge was generated in the chamber at a treatment frequency of 13 kHz and an applied voltage of 9 kV, and F Powder 1 was plasma-treated for 1 minute to obtain Modified Powder 1. 67 parts by mass of distilled water was added to 33 parts by mass of modified powder 1, and the mixture was stirred for 60 minutes to obtain liquid composition 1, which contained modified powder 1 and water but did not contain surfactant, and in which modified powder 1 was dispersed.

[0096] [Example 1-2] Evaluation example A mixture of 1 part by mass of a nonionic fluorine-based surfactant (Ftergent 250, manufactured by Neos Corporation) and 66 parts by mass of distilled water was added to 33 parts by mass of F Powder 1, and the mixture was stirred for 60 minutes to obtain Liquid Composition C1 in which Powder 1 was dispersed. This Liquid Composition C1 corresponds to the dispersion liquid (C-1) described in paragraph 0156 of WO 2018 / 016644. Liquid Composition 1 and Liquid Composition C1 were evaluated for "dispersibility" as described in the examples of WO 2018 / 016644, and the two liquid compositions showed equivalent dispersibility.

[0097] [Examples 1-3] Production examples of modified powder 2 and liquid composition 2 Modified Powder 2 was obtained, and Liquid Composition 2 was obtained, in the same manner as in Example 1-1, except that F Powder 1 was changed to F Powder 2. [Examples 1-4] Production examples of modified powder 3 and liquid composition 3 Modified powder 3 and liquid composition 3 were obtained in the same manner as in Example 1-1, except that F powder 1 was changed to F powder 2, the outside air was not particularly shielded during plasma discharge, and plasma discharge was performed with the total concentration of Ar gas and hydrogen gas in the chamber during plasma treatment set to less than 99.9% and oxygen gas set to more than 1% by volume.

[0098] [Example 1-5] Evaluation example A liquid composition C2 was prepared in the same manner as in Example 1-2, except that F Powder 1 was changed to F Powder 2. The adhesiveness of the molded articles of each of Liquid Compositions 2, 3 and C2 was evaluated according to the following procedure. Each liquid composition was applied to copper foil by die coating, passed through a drying oven at 120°C for 5 minutes to form a dry film on the copper foil surface, and then passed through a far-infrared oven at 380°C for 10 minutes to bake the polymer, preparing a laminate in which a polymer layer (10 μm thick) was formed on the surface of the copper foil. A rectangular test piece 100 mm long and 10 mm wide was cut from this laminate, and the copper foil was peeled from the polymer layer to a position 50 mm from one end of the test piece in the longitudinal direction. During peeling, the test piece was centered at a position 50 mm from one end in the longitudinal direction, and peeled at an angle of 90 degrees at a pulling rate of 50 mm / min using a tensile tester (manufactured by Orientec Co., Ltd.). The average load was measured from a measurement distance of 10 mm to 30 mm, and the peel strength (N / cm) of the laminate was evaluated. The peel strength of the laminate formed from Liquid Composition 2 was 8 N / cm, the peel strength of the laminate formed from Liquid Composition 3 was 4 N / cm, and the peel strength of the laminate formed from Liquid Composition C2 was less than 3 N / cm.

[0099] [Example 2] Modified film manufacturing example The following raw materials were used: Film 1: Film of F polymer 1 (thickness: 25 μm). Film 2: A film (thickness: 25 μm) of polymer 3 (melting point: 305° C., fluorine content: 71% by mass) containing 98.2 mol % of TFE units and 1.8 mol % of PPVE units. In each of Film 1 and Film 2, the peak H of the film measured by ESCA (a peak between 284 eV and 286 eV in a region from the surface of the film to a depth of 10 nm) was weak, and the maximum height of Peak H was sufficiently smaller than 0.2 times the maximum height of Peak F (a peak between 289 eV and 295 eV in a region from the surface of the film to a depth of 10 nm), and the fluorine atom content was 60%.

[0100] Surface measurements by ESCA were performed using a Quantera II (ULVAC-PHI). Monochromated AlKα X-rays were used at 100 W. An ion gun and a neutralization gun with a barium oxide emitter were used to prevent charging of the sample surface. The photoelectron detection area was 100 μmφ, the photoelectron detection angle was 45°, and the pass energy was 55 eV. The fluorine atom content was calculated from the various peak intensities (N1s, O1s, C1s, and F1s orbitals) detected by the measurements. The depth from the surface was determined based on the sputtering rate of the SiO2 film, which was sputtered using C60 ions.

[0101] [Example 2-1] Example of manufacturing modified film 1 Film 1 was placed in a plasma chamber equipped with a mechanism capable of generating plasma by dielectric barrier discharge, with a pair of opposing electrodes sandwiching a dielectric. A mixed gas containing 95% by volume of Ar gas and 5% by volume of hydrogen gas was flowed into the chamber, and the chamber was shielded from the outside air. The pressure inside the chamber was maintained at 0.1 MPa and the temperature inside the chamber was maintained at 25°C. Plasma discharge was generated inside the chamber at a treatment frequency of 13 kHz and an applied voltage of 9 kV, and Film 1 was plasma-treated for 2 minutes.

[0102] On the surface of the obtained film (Modified Film 1), the maximum height of Peak H was 2.5 times that of Peak F, and the fluorine atom content in this region was 30%. Furthermore, when the surface of Modified Film 1 was etched 100 nm in the thickness direction and the surface was measured again by ESCA, the profile was equivalent to that of Film 1, confirming that Modified Film 1 was a film having a modified layer formed by introducing hydrogen atoms into Polymer 1 on the surface.

[0103] [Example 2-2] Manufacturing example of modified film 2 Film 1 was plasma treated in the same manner as in Example 1, except that the gas sealed in the chamber was changed to a mixed gas containing 94 vol % of Ar gas, 5 vol % of ammonia gas, and 1 vol % of water vapor. On the surface of the obtained film (modified film 2), the maximum height of peak H was 0.2 times the maximum height of peak F, confirming that modified film 2 was a film having a modified layer formed on its surface by the introduction of hydrogen atoms into polymer 1.

[0104] [Example 2-3] Manufacturing example of modified film 3 Film 2 was plasma treated in the same manner as in Example 1, except that Film 1 was replaced with Film 2. On the surface of the obtained film (modified film 3), the maximum height of peak H was three times the maximum height of peak F, and the fluorine atom content in the region was 25%, confirming that modified film 3 was a film having a modified layer formed on the surface by the introduction of hydrogen atoms into polymer 2.

[0105] [Example 2-4] Production example of modified film 4 (comparative example) Film 1 was subjected to plasma treatment in the same manner as in Example 1, except that only Ar gas was filled into the chamber. The surface condition of the obtained film (modified film 4) measured by ESCA was almost the same as that of film 1.

[0106] [Example 2-5] Production example of modified film 5 (comparative example) Film 1 was plasma treated in the same manner as in Example 1, except under vacuum conditions. The surface condition of the obtained film (modified film 5) measured by ESCA was almost the same as that of film 1.

[0107] [Example 2-6] Evaluation example of modified film The modified film 1 and pure copper foil were placed opposite each other and heat-pressed (temperature: 340 ° C, pressure: 15 kN / m) to obtain an adhesive laminate of the modified film 1 and copper foil. A rectangular test piece measuring 100 mm in length and 10 mm in width was cut out from this adhesive laminate and left at 25 ° C for 3 months. Next, the copper foil layer was peeled from the modified film 1 layer to a position 50 mm from one end of the longitudinal direction of the test piece. During peeling, the test piece was centered at a position 50 mm from one end of the longitudinal direction, and the test piece was peeled at a 90-degree angle at a pulling rate of 50 mm / min using a tensile tester (manufactured by Orientec Co., Ltd.). The average load was measured from a measurement distance of 10 mm to 30 mm, and this was taken as the peel strength (N / cm). For each film, adhesive laminates were similarly prepared and their peel strengths were evaluated. The results are summarized in Table 1.

[0108] [Table 1] [Industrial Applicability]

[0109] As is clear from the above results, the modified powder produced by this method is less likely to settle, and even without the addition of a surfactant, its dispersibility in water is equivalent to that when a surfactant is added. Furthermore, it is clear that the molded product formed from the liquid composition containing the modified powder produced by this method has higher adhesion to the substrate and exhibits higher adhesiveness than the molded product formed from the liquid composition containing the original powder. From the above, it is clear that the modified powder produced by this method has a highly surface-modified property, and that the composition containing this modified powder becomes a liquid composition with excellent liquid physical properties such as dispersibility, even without the addition of a surfactant, and can form molded products with high adhesion to substrates. The liquid composition containing the modified powder produced by this method is a liquid composition with excellent liquid properties such as dispersibility, and can be efficiently impregnated into porous or fibrous materials.

[0110] Furthermore, as is clear from the above results, when modified films 1 to 3, which are modified molded products produced by this method, are bonded to copper foil, the peel strength is higher than that between the original molded products, films 1 or 2, and copper foil, indicating that the adhesion strength has been improved. Furthermore, the peel strength between modified films 1 to 3 produced by this method and copper foil is higher than the peel strength between modified films 4 and 5, which were produced without this method, and copper foil. From the above, it can be seen that the modified molded products produced by this method have a highly surface-modified finish. Therefore, laminates of the modified molded products produced by this method with other substrates are thought to be useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, paints, cosmetics, etc.

Claims

1. A method for producing a modified tetrafluoroethylene-based polymer, comprising subjecting a tetrafluoroethylene-based polymer having a melting temperature of 200 to 325°C and containing units based on perfluoro(alkyl vinyl ether) or hexafluoropropylene to plasma treatment in an atmosphere shielded from air, the atmosphere containing either hydrogen gas or ammonia gas at near atmospheric pressure and a rare gas, wherein the concentration of the gas is 99.9% by volume or more.

2. A method for producing a modified powder, comprising: subjecting a powder of a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or hexafluoropropylene, and having a melting temperature of 200 to 325°C, to plasma treatment in an atmosphere shielded from air, the atmosphere containing either hydrogen gas or ammonia gas at near atmospheric pressure and a rare gas, wherein the concentration of the gas is 99.9% by volume or more, to modify the surface of the powder.

3. 3. The manufacturing method according to claim 2, wherein the powder is subjected to plasma treatment in an atmosphere shielded from air, the atmosphere containing a gas containing either hydrogen gas or ammonia gas and a rare gas at near atmospheric pressure, the gas having a concentration of 99.9% by volume or more, to obtain a powder formed by introducing hydrogen atoms into the tetrafluoroethylene-based polymer.

4. The method according to claim 2 or 3, wherein the powder is previously subjected to a plasma treatment in an atmosphere containing a rare gas before the plasma treatment.

5. The method according to any one of claims 2 to 4, wherein the tetrafluoroethylene-based polymer has a fluorine content of 70 to 76 mass%.

6. The method according to claim 2 , wherein the tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom.

7. A liquid composition comprising a modified powder obtained by the manufacturing method according to any one of claims 2 to 6 and a liquid dispersion medium, in which the modified powder is dispersed.

8. A method for producing a modified molded article having, on at least a portion of its surface, a modified layer having a thickness of 1 nm to 100 nm formed by introducing hydrogen atoms into the tetrafluoroethylene-based polymer, the modified layer being formed by plasma treatment of at least a portion of the surface of the molded article, the modified layer comprising a tetrafluoroethylene-based polymer having a melting temperature of 200 to 325°C and containing units based on perfluoro(alkyl vinyl ether) or hexafluoropropylene, in an atmosphere shielded from air and containing a gas containing either hydrogen gas or ammonia gas at near atmospheric pressure and a rare gas, the gas concentration being 99.9% by volume or more.

9. The manufacturing method according to claim 8 , wherein, before the plasma treatment, the surface layer is previously subjected to a plasma treatment in an atmosphere not containing a reducing gas.

10. The method according to claim 9 , wherein the reducing gas is hydrogen gas, ammonia gas, or hydrocarbon gas.

11. The method according to claim 8 , wherein the tetrafluoroethylene-based polymer has an atomic group containing an oxygen atom.

12. A modified molded article comprising a tetrafluoroethylene-based polymer, the polymer having a melting temperature of 200 to 325°C and containing units based on perfluoro(alkyl vinyl ether) or hexafluoropropylene, has a modified layer on at least a part of its surface, the modified layer having a thickness of 1 nm to 100 nm, formed by the introduction of hydrogen atoms through the action of hydrogen radicals on C-F bonds, the modified layer having a maximum height of a peak between 284 eV and 286 eV in a region from the surface to a depth of 1 nm, as measured by X-ray photoelectron spectroscopy, being 0.2 times or more the maximum height of a peak between 289 eV and 295 eV in said region, and the fluorine atom content in said region being 55% or less.

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