Method for producing powder, powder and powder dispersion

Abstract

The present invention provides a powder having excellent dispersion stability in a powder dispersion, a method for producing the same, and a powder dispersion having excellent dispersion stability. The method for producing the powder of the present invention comprises the steps of causing agglomerates of a thermofusible tetrafluoroethylene polymer to flow while heat-treating the aggregates at a temperature below the melting temperature of the tetrafluoroethylene polymer and then pulverizing the aggregates to obtain a powder having an average particle size of greater than 1 μm and less than 10 μm and a specific surface area of ​​1 m 2 / g or more and less than 8m 2 / g, and a powder of the tetrafluoroethylene-based polymer having a unimodal particle size distribution.

Description

Technical Field

[0001] The present invention relates to a tetrafluoroethylene polymer powder having a predetermined particle size distribution and specific surface area, a method for producing the powder, and a powder dispersion containing the powder. Background Art

[0002] Hot-melt tetrafluoroethylene polymers have excellent physical properties (electrical insulation, water and oil repellency, chemical resistance, etc.) and melt processability. Therefore, tetrafluoroethylene polymer powders themselves are used as powder coatings (see Patent Document 1) or as powder dispersions containing the same (see Patent Document 2).

[0003] Patent Document 1 discloses a method of pulverizing a coagulant recovered from a tetrafluoroethylene polymer solution to obtain a polymer having a specific surface area of ​​8 to 25 m 2 / g and a powder with an average particle size of 1 to 100 μm. However, because Patent Document 1 heat-treats the agglomerate in a static state, the degree of heat treatment tends to vary. Consequently, the specific surface area of ​​the powder obtained by subsequent pulverization is difficult to reduce, and the particle size distribution tends to exhibit multimodality.

[0004] On the other hand, Patent Document 2 describes a powder of a tetrafluoroethylene polymer dispersed in a powder dispersion having a specific surface area of ​​15 m 2 Patent Document 2 also states that if the average particle size of the powder exceeds 1 μm, the dispersion stability of the powder in the powder dispersion will decrease.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-169339

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-088861 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] The present inventors have diligently investigated methods for improving the dispersion stability of the aforementioned powder in a powder dispersion. They have discovered that the dispersion stability of the powder in the powder dispersion is improved by adjusting the average particle size within a predetermined range, achieving a monomodal particle size distribution, and reducing the specific surface area.

[0011] An object of the present invention is to provide a powder having excellent dispersion stability in a powder dispersion liquid, a method for producing the same, and a powder dispersion liquid having excellent dispersion stability.

[0012] Technical solutions used to solve technical problems

[0013] The present invention has the following aspects.

[0014] [1] A method for producing a powder, wherein a heat-treated agglomerate of a thermo-fusible tetrafluoroethylene polymer is made to flow while being heat-treated below the melting temperature of the tetrafluoroethylene polymer and then pulverized to obtain a powder having an average particle size of greater than 1 μm and less than 10 μm and a specific surface area of ​​1 m 2 / g or more and less than 8m 2 / g, and a powder of the tetrafluoroethylene-based polymer having a unimodal particle size distribution.

[0015] [2] The production method according to [1], wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer containing units based on perfluoro(alkyl vinyl ether) or units based on hexafluoropropylene.

[0016] [3] The production method according to [1] or [2], wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer having a polar functional group.

[0017] [4] The production method according to any one of [1] to [3], wherein the average particle size of the agglomerates is 100 μm to 5 mm.

[0018] [5] The production method according to any one of [1] to [4], wherein the temperature when the coagulate is heat-treated is higher than the melting temperature of the tetrafluoroethylene polymer minus 100°C.

[0019] [6] The production method according to any one of [1] to [5], wherein the agglomerate is heat-treated while being rolled in a rotary kiln rotating about a central axis.

[0020] [7] The manufacturing method according to [6], wherein the rotary kiln has an inclination angle relative to the horizontal direction of 0.01 to 5°.

[0021] [8] The manufacturing method according to [6] or [7], wherein the rotation speed of the rotary kiln is 1 to 20 rpm.

[0022] [9] The production method according to any one of [6] to [8], wherein the residence time of the agglomerate in the rotary kiln is 1 to 60 minutes.

[0023]

[10] The production method according to any one of [1] to [9], wherein the hardness of the agglomerate before the pulverization is 0.2 N / mm or more.

[0024]

[11] The production method according to any one of [1] to

[10] , wherein the agglomerates are agglomerates of particles of the tetrafluoroethylene-based polymer formed by polymerization of a raw material monomer of the tetrafluoroethylene-based polymer.

[0025]

[12] Powder, which is a powder of a thermoplastic tetrafluoroethylene polymer, wherein the average particle size of the powder is greater than 1 μm and less than 10 μm, and the specific surface area is less than 1 m 2 / g or more and less than 8m 2 / g, with a unimodal particle size distribution.

[0026]

[13] The powder as described in

[12] , wherein the full width at half maximum of the particle size distribution is 0.5 to 3.5 μm.

[0027]

[14] A powder dispersion comprising the powder of

[12] or

[13] and a liquid dispersion medium.

[0028]

[15] The powder dispersion according to

[14] , wherein the viscosity of the powder dispersion is less than 1000 mPa·s.

[0029] Effects of the Invention

[0030] According to the present invention, a tetrafluoroethylene polymer powder having a predetermined average particle size, particle size distribution, and specific surface area can be easily produced, and the powder and a powder dispersion having excellent dispersion stability can also be obtained. DETAILED DESCRIPTION

[0031] The following terms have the meanings described below.

[0032] The "average particle size (D50)" is the volume-based cumulative 50% diameter of the object (powder or agglomerate), as determined by laser diffraction scattering. Specifically, 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 object particles as 100%. The particle size at the point where the cumulative volume reaches 50% is determined on the cumulative curve.

[0033] “D90” is the volume-based cumulative 90% diameter of the object measured in the same manner.

[0034] The “full width at half maximum” is the width of the peak at half the height of the peak height (maximum value) in the particle size distribution curve of the object.

[0035] The "melting temperature (melting point) of a polymer" refers to the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC).

[0036] The “glass transition temperature (Tg) of a polymer” refers to the viscosity of a liquid measured using a Brookfield viscometer at room temperature (25° C.) and a rotation speed of 60 rpm.

[0037] The “thixotropic ratio of the dispersion” refers to a value calculated by dividing the viscosity of the dispersion measured at a rotation speed of 30 rpm by the viscosity of the dispersion measured at a rotation speed of 60 rpm.

[0038] A "unit" in a polymer can be an atomic group formed directly from a monomer, or it can be an atomic group formed by partially transforming the structure of the resulting polymer through treatment using a prescribed method. Units based on monomer A in a polymer are also simply referred to as "monomer A units."

[0039] The method for producing a powder of the present invention (hereinafter also referred to as "this method") is to make agglomerates of a hot-melt tetrafluoroethylene polymer (hereinafter also referred to as "F polymer") flow while heat-treating them at a temperature below the melting temperature of the F polymer and then pulverizing them to obtain a powder having a D50 of greater than 1 μm and less than 10 μm and a specific surface area of ​​1 m 2 / g or more and less than 8m 2 The powder of polymer F obtained by this method has a unimodal particle size distribution.

[0040] According to this method, the F polymer agglomerates are heat-treated in a fluidized state rather than a static state. Therefore, heat is easily and evenly transferred to the agglomerates during heating, and the surface of the agglomerates is highly heat-treated, which tends to soften the interior of the agglomerates. Furthermore, since the agglomerates in this state are subjected to moderate impact (vibration) caused by the flow, it is believed that the agglomerates are dense overall, have a small specific surface area, and have high hardness (especially surface hardness). Since the agglomerates undergoing this heat treatment are pulverized, the D50 of the resulting powder is reduced and irregular particles are less likely to form. In other words, the resulting powder is believed to have a sufficiently low D50, a unimodal particle size distribution, and a small specific surface area.

[0041] Then, by using this powder, a powder dispersion having excellent dispersion stability can be easily obtained.

[0042] The F polymer of the present invention is a hot-melt polymer containing units based on tetrafluoroethylene (TFE) (TFE units).

[0043] The melting temperature of the F polymer is preferably 260 to 320°C, more preferably 285 to 320°C.

[0044] The glass transition temperature of the F polymer is preferably 75 to 125°C, more preferably 80 to 100°C.

[0045] The F polymer is preferably a polymer containing TFE units, perfluoro(alkyl vinyl ether) (PAVE)-based units (PAVE units), or hexafluoropropylene (HFP)-based units (HFP units). In this case, the F polymer forms small spherulites, resulting in high surface smoothness of the aggregates and a reduced specific surface area of ​​the resulting powder. Furthermore, denaturation of the F polymer during heat treatment is more easily suppressed.

[0046] The F polymer may contain both PAVE units and HFP units, or may contain only one of them.

[0047] PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, CF2=CFOCF2CF2CF3 (PPVE) or CF2=CFOCF(CF3)CF2OCF2CF2CF3, more preferably PPVE.

[0048] The polymer F preferably has a polar functional group. In this case, denaturation of the polymer F during heat treatment can be more highly suppressed, and a powder having more excellent dispersion stability can be easily produced.

[0049] The polar functional group may be contained in a unit of the polymer F or in a terminal group of the polymer main chain. The latter embodiment includes a polymer F having a polar functional group as a terminal group derived from a polymerization initiator, chain transfer agent, or the like, or a polymer F having a polar functional group obtained by plasma treatment or electrolytic desorption treatment of the polymer F.

[0050] The polar functional group is preferably a hydroxyl group or a carbonyl group, and is more preferably a carbonyl group from the viewpoint of powder dispersion stability.

[0051] As the hydroxyl group-containing group, a group containing an alcoholic hydroxyl group is preferred, and -CF2CH2OH or -C(CF3)2OH is more preferred.

[0052] The carbonyl-containing group is a group containing a carbonyl group (>C(O)), preferably a carbonyl group, a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH2), an anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) or a carbonate group (-OC(O)O-).

[0053] When the F polymer has a carbonyl group, the number of carbonyl groups in the F polymer is 1×10 6The number of carbonyl groups in the polymer F can be determined based on the composition of the polymer or by the method described in International Publication No. 2020 / 145133.

[0054] The F polymer is preferably a polymer (1) having a polar functional group comprising TFE units, PAVE units, and units based on a monomer having a polar functional group, or a polymer (2) not having a polar functional group comprising TFE units and PAVE units and containing 2.0 to 5.0 mol% of PAVE units relative to all units.

[0055] These F polymers have excellent powder dispersion stability, and not only good handling and blending properties, but also form fine spherulites in a molded article (such as the F layer described later), which tends to improve adhesion.

[0056] The polymer (1) 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 based on a monomer having a polar functional group, based on all units.

[0057] Furthermore, as the monomer having a polar functional group, maleic anhydride, itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (also known as nadic anhydride, hereinafter also referred to as "NAH") is preferred.

[0058] Specific examples of the polymer (1) include the polymers described in International Publication No. 2018 / 16644.

[0059] The polymer (2) is preferably composed of only TFE units and PAVE units, and contains 95.0 to 98.0 mol% of TFE units and 2.0 to 5.0 mol% of PAVE units based on the total units.

[0060] The content of the PAVE unit in the polymer (2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more, based on the total units.

[0061] The polymer (2) does not have a polar functional group, which means that the polymer (2) has no polar functional group. 6 The number of carbon atoms constituting the polymer backbone is less than 500. The number of polar functional groups is preferably 100 or less, more preferably less than 50. The lower limit of the number of polar functional groups is usually 0.

[0062] Polymer (2) can be produced using a polymerization initiator or chain transfer agent that does not generate a polar functional group as a terminal group of the polymer chain, or by fluorinating an F polymer having a polar functional group (an F polymer having a polar functional group derived from a polymerization initiator as a terminal group of the polymer main chain). As a method of fluorination, a method using fluorine gas can be exemplified (see Japanese Patent Laid-Open No. 2019-194314, etc.).

[0063] The F polymer agglomerates are preferably agglomerates of F polymer particles formed by polymerization of the raw material monomers of the F polymer, and more preferably agglomerates of F polymer primary particles formed by polymerization of the raw material monomers of the F polymer. The average particle size of the F polymer particles is preferably less than 1 μm. The average particle size of the F polymer particles is preferably 0.01 μm or greater. The D50 of the powder obtained by heat-treating the agglomerates and then pulverizing them tends to be further reduced. Furthermore, the powder particle size distribution tends to be sharply unimodal.

[0064] Examples of methods for aggregating the F polymer particles include a method of aggregating the F polymer particles by mixing a liquid composition containing the F polymer particles with a coagulant, and a method of aggregating the F polymer particles by shearing and stirring the liquid composition. The liquid composition is preferably a liquid composition containing primary particles of the F polymer and a polymerization medium, formed by polymerizing raw material monomers of the F polymer in a polymerization medium.

[0065] If the coagulates formed by these methods and including the coagulates of the F polymer are recovered by solid-liquid separation and then dried, dried coagulates can be obtained.

[0066] The D50 of the agglomerate is preferably 100 μm to 5 mm, more preferably 1 to 3 mm. In this case, the D50 of the obtained powder can be sufficiently reduced while ensuring the handleability of the agglomerate.

[0067] In the present invention, the agglomerate is heat-treated while being fluidized. Examples of the heat-treatment method include method I using a rotary kiln and method II using a heat-treatment device (hot-air fluidizing device) that generates swirling hot air.

[0068] In the former method I, the condensate is heat-treated by rolling it through a cylindrical rotary kiln rotating about its central axis. In this method I, the condensate rolls while contacting the heated inner surface of the rotary kiln, making it particularly easy to evenly transfer heat to the condensate.

[0069] The temperature during heat treatment is below the melting temperature of polymer F, preferably above the melting temperature of polymer F - 100°C and below the melting temperature of polymer F, and more preferably above 200°C and below 300°C. Heat treatment of the agglomerate at this temperature increases its density and hardness. As a result, the powder obtained by pulverization has a smaller D50 and tends to have a sharper, unimodal particle size distribution.

[0070] The specific hardness of the aggregates before pulverization is preferably 0.2 N / mm or greater, more preferably 0.3 N / mm or greater. The hardness is preferably 0.8 N / mm or less. In this case, the impact force applied to the aggregates during pulverization is increased, thereby facilitating more uniform micronization.

[0071] The rotary kiln is preferably tilted at an angle of 0.01 to 5°, more preferably 0.1 to 3°, relative to the horizontal direction (the ground surface of the rotary kiln). Inclining the rotary kiln at this angle ensures a sufficiently long passage time (residence time) for the condensate within the rotary kiln. As a result, the condensate can be heated more evenly and sufficiently.

[0072] The residence time of the aggregate in the rotary kiln is preferably 1 to 60 minutes, more preferably 5 to 40 minutes. In this case, sufficient heating time for the aggregate can be ensured.

[0073] The rotation speed of the rotary kiln is preferably 1 to 20 rpm, more preferably 3 to 10 rpm. In this case, excessive impact force is less likely to be applied to the aggregate, and undesirable breakage of the aggregate during rolling (flowing) can be prevented.

[0074] The feeding speed of the aggregate into the rotary kiln is preferably such that the filling rate of the aggregate in the rotary kiln reaches 0.1 to 40%, more preferably such that the filling rate reaches 1 to 20%. In this case, the heat treatment of the aggregate can be performed sufficiently and efficiently.

[0075] As the rotary kiln, for example, an apparatus manufactured by Noritake Co., Ltd. or an apparatus manufactured by Sanai Chemical Co., Ltd. can be used.

[0076] In the latter method, method II, hot air is supplied while swirling within a cylindrical processing space, and condensates and a transport gas are supplied into the processing space from a tangential direction of the processing space, thereby heat-treating the condensates with the hot air. This method II prevents transient turbulence caused by the transport gas containing condensates being introduced into the processing space, thereby suppressing the generation of aggregated particles (coarse particles).

[0077] Furthermore, it is preferred that the transport gas containing the condensate be supplied into the processing space from multiple condensate supply ports arranged on the same plane along the circumference of the processing space. The greater the number of condensate supply ports, the less condensate is supplied from each port. Therefore, the temperature of the hot air required for heat treatment of the condensate can be lowered depending on the number of condensate supply ports. Furthermore, the generation of aggregated particles can be suppressed.

[0078] The aggregates can be transported within the processing space while flowing in the swirling flow of hot air. In this case, heat is evenly transferred to the aggregates, making densification and sphericalization easier.

[0079] The heat-treated condensate is cooled by cold air supplied from a cold air supply port provided downstream (vertically lower) of the condensate supply port.

[0080] Similar to the condensate supply port, cold air is supplied from the cold air supply port in a tangential direction to the processing space. Furthermore, cold air is preferably supplied into the processing space from multiple cold air supply ports arranged in the same plane along the circumference of the processing space. This prevents instantaneous turbulence when the cold air is introduced into the processing space, thereby suppressing the generation of aggregated particles (coarse particles).

[0081] The greater the number of cold air supply ports, the higher the cooling efficiency of the heat-treated condensate. This reduces uneven cooling of the condensate and makes it easier to obtain condensate with uniform circularity.

[0082] The placement of the cold air supply port maintains a swirling flow in the processing space, thereby suppressing the adhesion of condensates to the bottom of the heat treatment apparatus partitioned into the processing space.

[0083] The condensate passing through the processing space is sucked by a suction device and discharged (recovered) from a condensate discharge port provided downstream (vertically lower) of the cold air supply port.

[0084] In this heat treatment device, the total flow rate (total supply rate) of compressed air, hot air and cold air supplied to the treatment space is Q IN and the flow rate (total discharge) Q discharged from the treatment space through the suction device OUT The relationship is preferably adjusted to Q IN ≤Q OUT In this case, the pressure in the processing space becomes negative, so the aggregates in the processing space are easily discharged, which can prevent excessive heat from being applied to the aggregates. Therefore, the generation of aggregated particles and the amount of aggregates attached to the heat treatment device can be reduced.

[0085] The hardness of the condensate discharged from the treatment space is likely to be within the above-mentioned range. In addition, the temperature of the hot air (temperature during heat treatment) is also the same as above.

[0086] As the heat treatment apparatus, for example, a flash dryer (manufactured by Seishin Enterprise Co., Ltd.) can be used.

[0087] The heat-treated aggregates are pulverized (destroyed) to obtain powder of polymer F. This pulverization is preferably performed by mechanical pulverization.

[0088] The mechanical pulverization treatment is performed using a device that can exert sufficient shearing force and / or crushing force in order to break up agglomerates and form smaller particles (powder).

[0089] Examples of the apparatus include a hammer mill with a pulverizer, a pin mill, a disc mill, a rotary mill, a jet mill, a fluidized bed air jet mill, a jaw crusher, a gyratory crusher, a cage mill, a disc crusher, a ball mill, a pebble mill, a rod mill, a tube mill, a disc mill, an attritor, and a disc refiner.

[0090] Mechanical pulverization is preferably carried out using a hammer mill, pin mill, disc mill, rotary mill, or jet mill. Using these devices can easily reduce the D50 of the resulting powder, resulting in a sharper, unimodal particle size distribution. Furthermore, the specific surface area of ​​the powder can be more easily reduced.

[0091] The temperature during pulverization is preferably -40°C or lower, more preferably -100°C or lower, and further preferably -160°C or lower. In this case, the low-temperature brittleness of the F polymer is utilized, and the D50 of the powder can be made smaller than in the case of uncooled agglomerates.

[0092] In addition, cooling is preferably performed using solidified carbon dioxide or liquid nitrogen.

[0093] Specific examples of the above apparatus include a jet mill (“reverse jet mill” manufactured by Hosokawa Micron Co., Ltd.) and a planetary ball mill (“planetary ball mill PM100” manufactured by Recce Co., Ltd.).

[0094] The powder of polymer F in the present invention is a powder containing polymer F, preferably a powder consisting of polymer F. Other components that may be contained in the powder of polymer F include aromatic polyester, polyamide-imide, thermoplastic polyimide, and polyphenylene ether.

[0095] The polymer F powder has a D50 of greater than 1 μm and less than 10 μm, preferably greater than 1 μm and less than 8 μm, and more preferably greater than 1 μm and less than 6 μm. In this case, the polymer F powder has high flowability, the handleability of the powder dispersion containing the powder is improved, and the dispersion stability is also excellent.

[0096] The powder has a unimodal particle size distribution with a full width at half maximum of preferably 0.5 to 3.5 μm, more preferably 1 to 2.5 μm. This means that the powder does not contain irregular particles (coarse particles), and when preparing a powder dispersion, powder aggregation originating from irregular particles is unlikely to occur.

[0097] The specific surface area of ​​the powder is 1m 2 / g or more and less than 8m 2 / g, preferably 1 to 5 m 2 / g, more preferably 1 to 3 m 2 In this case, the specific surface area is smaller, and thus the dispersion stability of the powder dispersion is further improved.

[0098] The powder of the present invention (hereinafter also referred to as "the present powder") is a powder of F polymer having a single-peak particle size distribution with D50 greater than 1 μm and less than 10 μm, and a specific surface area of ​​1 m 2 / g or more and less than 8m 2 / g.

[0099] The definition and scope of the present powder, including preferred embodiments, are the same as those in this method. In addition, the definition and scope of the F polymer in the present powder, including preferred embodiments, are the same as those in this method.

[0100] The present powder is preferably a powder produced by this method.

[0101] The powder dispersion of the present invention (hereinafter also referred to as "the present dispersion") comprises the present powder and a liquid dispersion medium. Since the present powder has the above characteristics, the present dispersion has excellent dispersion stability.

[0102] As described above, the present powder contains no irregularly shaped particles, or even if it does, the content of irregularly shaped particles is extremely small. Therefore, when the present powder and a liquid dispersion medium are mixed by stirring or the like to prepare the present dispersion, denaturation of the present powder is highly suppressed, and the present dispersion is less likely to increase in viscosity.

[0103] The degree to which the present dispersion is less likely to increase in viscosity can be evaluated based on the viscosity increase ratio before and after stirring of the present dispersion.

[0104] Specifically, the viscosity increase calculated by the following formula based on the viscosity measured before and after stirring the dispersion at 8000 rpm for 30 minutes is preferably less than 60%, more preferably less than 40%. The lower limit of the viscosity increase of the dispersion is 0%.

[0105] Formula: Viscosity increase rate = {(viscosity after stirring / viscosity before stirring) - 1} × 100

[0106] The liquid dispersion medium is preferably a liquid compound that is inert at 25° C. and functions as a dispersion medium for the present powder. The liquid dispersion medium may be used alone or in combination of two or more.

[0107] The boiling point of the liquid dispersion medium is preferably 125 to 250° C. In this case, when the liquid film of the present dispersion is dried to form a dry film, the powder flows efficiently as the liquid dispersion medium evaporates, and the powder is easily densely packed.

[0108] Specific examples of the liquid dispersion medium include water, N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, cyclopentanone, butyl acetate, methyl isopropyl ketone, cyclopentanone, and cyclohexanone.

[0109] The liquid dispersion medium is preferably an amide, a ketone or an ester, and more preferably N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone or γ-butyrolactone.

[0110] The content of the F polymer in the present dispersion is preferably 5 to 70% by mass, more preferably 10 to 60% by mass.

[0111] The content of the liquid dispersion medium in the present dispersion is preferably 30 to 95% by mass, more preferably 40 to 90% by mass.

[0112] The present dispersion may further contain components other than the F polymer and the liquid dispersion medium.

[0113] The present dispersion preferably further contains a surfactant, in which case the dispersion of the F polymer powder is facilitated and the dispersion stability of the present dispersion is further enhanced.

[0114] In this case, the content of the surfactant in the present dispersion is preferably 1 to 15% by mass.

[0115] The surfactant is preferably a nonionic surfactant.

[0116] The hydrophilic portion of the surfactant preferably has an oxyalkylene group or an alcoholic hydroxyl group.

[0117] The oxyalkylene group may be composed of one type of oxyalkylene group or may be composed of two or more types of oxyalkylene groups. In the latter case, the different types of oxyalkylene groups may be arranged randomly or in blocks.

[0118] The oxyalkylene group is preferably an oxyethylene group or an oxypropylene group, more preferably an oxyethylene group.

[0119] The hydrophobic portion of the surfactant preferably has an acetylene group, a polysiloxane group, a perfluoroalkyl group, or a perfluoroalkenyl group.

[0120] The surfactant is preferably a glycol surfactant, an acetylene surfactant, a silicone surfactant or a fluorine surfactant, more preferably a silicone surfactant. The nonionic surfactant may be one or more. When two nonionic surfactants are used, the nonionic surfactants are preferably a silicone surfactant and a glycol surfactant.

[0121] The fluorine-based surfactant is 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. An ethereal oxygen atom may be inserted between carbon atoms in the perfluoroalkyl group.

[0122] The weight average molecular weight of the above surfactant is preferably 5,000 to 300,000.

[0123] The fluorine content of the above surfactant is more preferably from 15 to 90 mass %.

[0124] The content of the oxyethylene groups in the above surfactants is preferably 10 to 60% by mass.

[0125] The hydroxyl value of the above surfactant is preferably 10 to 100 mgKOH / g.

[0126] The fluorine-based surfactant is preferably a copolymer of a fluoro(meth)acrylate and a hydrophilic (meth)acrylate.

[0127] Specific examples of fluoro(meth)acrylates include CH2=C(CH3)C(O)OCH2CH2(CF2)4F, CH2=C(CH3)C(O)OCH2CH2(CF2)6F, CH2=C(CH3)C(O)OCH2CH2CH2CH2OCF(CF3)C(=C(CF3)2)(CF(CF3)2), and CH2=C(CH3)C(O)OCH(CH3)OCH2(CF2)6F.

[0128] Specific examples of the hydrophilic (meth)acrylate include CH2=C(CH3)C(O)(OCH2CH2)4OH, CH2=C(CH3)C(O)(OCH2CH2)9OH, CH2=C(CH3)C(O)(OCH2CH2) 23 OH.

[0129] Specific examples of surfactants include "Ftergent" series (manufactured by Neos Co., Ltd.), "Surflon" series (manufactured by AGC Seimi Chemical Co., Ltd.), "MEGA FACE" series (manufactured by DIC Co., Ltd.), "Unidyne" series (manufactured by Daikin Industries, Ltd.), "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-34" 55", "BYK-3456" (manufactured by BYK Chemical Japan Co., Ltd.), "KF-6011", "KF-6043" (Shin-Etsu Chemical Co., Ltd. (Shin-Etsu Chemical Co., Ltd.)), "Tergitol" series (Manufactured by Dow Chemical Co., Ltd. (Dow Chemical Co., Ltd.), "Tergitol" TMN-100X" etc.).

[0130] When the present dispersion contains a nonionic surfactant, the content of the nonionic surfactant in the present dispersion is preferably 1 to 15% by mass.

[0131] The present dispersion may further comprise a polymer different from the polymer F. Examples of the different polymer include aromatic polyesters, polyamideimides, polyimides, polyphenylene ethers, polyphenylene ethers, and maleimides, with thermoplastic aromatic polyimides being preferred.

[0132] The dispersion may further contain an inorganic filler, a thixotropy imparting agent, a defoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a release agent, a surface treatment agent, a viscosity modifier, and a flame retardant.

[0133] The viscosity of the present dispersion is preferably 1000 mPa·s or less, more preferably 50 to 750 mPa·s. Since the present powder has the above characteristics, the viscosity of the present dispersion can be easily reduced.

[0134] The thixotropic ratio of the present dispersion is preferably 1.0 to 3.0, more preferably 1.0 to 2.0.

[0135] When the viscosity and thixotropic ratio of the present dispersion are within the above ranges, the present dispersion in which the present powder is highly dispersed and contained can be easily obtained. Furthermore, the present dispersion has excellent workability such as coating properties and compatibility with other components.

[0136] The present dispersion can be used as a coating material that imparts insulation, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and thermal conductivity.

[0137] Specifically, the present dispersion can be used in printed wiring boards, thermal interface materials, substrates for power modules, coils used in power equipment such as motors, automobile engines, heat exchangers, vials, syringes (syringes), ampoules, medical wires, secondary batteries such as lithium-ion secondary batteries, primary batteries such as lithium batteries, free radical batteries, solar cells, fuel cells, lithium-ion capacitors, hybrid capacitors, capacitors (capacitors), capacitors (condensers) (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical switching elements, electrode adhesives, electrode separators, and electrodes (positive and negative electrodes).

[0138] Furthermore, this dispersion can be used as an adhesive for bonding components. Specifically, this dispersion can be used for bonding ceramic components, bonding metal components, bonding electronic components such as IC chips, resistors, and capacitors to substrates of semiconductor devices or module components, bonding circuit boards to heat sinks, and bonding LED chips to substrates.

[0139] Furthermore, the present dispersion further comprising a conductive filler can also be used in applications requiring conductivity, such as the printed electronics field. Specifically, it can be used in the production of current-carrying elements such as printed circuit boards and sensor electrodes.

[0140] This dispersion is applied to the surface of a substrate layer to form a liquid film, and the liquid dispersion medium is volatilized by heating to obtain a dry film. If the F polymer is further heated to calcine, a laminate having a substrate layer and a polymer layer containing the F polymer (hereinafter also referred to as "F layer") can be obtained.

[0141] As described above, this dispersion is less likely to thicken due to the highly suppressed denaturation of the powder during preparation. Consequently, this dispersion exhibits excellent leveling properties. Furthermore, the powder readily forms densely, resulting in a highly smooth and dense surface of the F layer formed from this dispersion.

[0142] The arithmetic mean roughness (Ra) of the surface of the F layer (the surface opposite to the base layer) is preferably less than 0.6 μm, more preferably less than 0.4 μm. The arithmetic mean roughness (Ra) is usually 0.05 μm or more.

[0143] The former heating temperature is preferably 120 to 200° C. The latter heating temperature is preferably a temperature equal to or higher than the melting point of the F polymer, specifically 300 to 380° C. In this case, the surface smoothness, flexibility, and electrical properties of the F layer tend to be excellent.

[0144] Examples of various heating methods include a method using an oven, a method using a ventilation drying furnace, and a method of irradiating with heat rays such as infrared rays.

[0145] Examples of the substrate constituting the substrate layer include metal substrates (substrates of copper, nickel, aluminum, titanium, alloys of these metals, etc.), resin films (films of polyimide, polyarylate, polysulfone, polyarylsulfone, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, liquid crystalline polyesteramide, etc.), and prepregs (precursors of fiber-reinforced resin substrates).

[0146] Examples of the method for applying the dispersion include spraying, roll coating, spin coating, gravure coating, micro gravure coating, gravure offset coating, knife coating, touch coating, rod coating, die coating, Meyer wire coating, and slot die coating.

[0147] The thickness of the F layer is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm. This dispersion has excellent handleability, and therefore has excellent physical properties such as surface smoothness, and can easily form an F layer of any thickness.

[0148] This dispersion can be applied to only one surface of the substrate layer or to both surfaces. In the former case, a laminate comprising a substrate layer and an F layer on one surface of the substrate layer can be obtained, while in the latter case, a laminate comprising a substrate layer and an F layer on both surfaces of the substrate layer can be obtained. The latter laminate is less likely to warp, thus providing excellent workability during processing.

[0149] Specific examples of the laminate include a metal-clad laminate comprising a metal foil and an F layer on at least one surface of the metal foil, and a multilayer film comprising a polyimide film and F layers on both surfaces of the polyimide film.

[0150] These laminates are excellent in various physical properties such as electrical properties, heat resistance such as reflow resistance, chemical resistance, and surface smoothness, and are therefore suitable as printed circuit board materials, etc. Specifically, the laminates can be used to manufacture flexible printed circuit boards or rigid printed circuit boards.

[0151] In addition, as the metal foil, a metal foil with a carrier comprising two or more layers of metal foil may also be used. As the metal foil with a carrier, a copper foil with a carrier composed of a carrier copper foil (thickness: 10 to 35 μm) and an ultra-thin copper foil (thickness: 2 to 5 μm) laminated on the carrier copper foil via a peeling layer may be exemplified. If a copper foil with a carrier is used, a fine pattern can be formed by the MSAP (modified semi-additive) method. As the peeling layer, a metal layer containing nickel or chromium and a multilayer metal layer laminated with the metal layer are preferred.

[0152] As a specific example of the metal foil with a carrier, the trade name "FUTF-5DAF-2" manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. (Fukuda Metal Foil Powder Industry Co., Ltd.) can be mentioned.

[0153] The ten-point average roughness of the substrate surface is 0.01 to 0.05 μm. Since this powder easily packs densely, it can form a laminate with excellent peel strength even on a substrate with a smooth surface.

[0154] In order to further improve the low linear expansion and adhesiveness of the outermost surface of the laminate (the surface of the polymer layer on the side opposite to the substrate layer), the outermost surface may be surface treated.

[0155] The surface treatment method may, for example, be annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment or silane coupling agent treatment.

[0156] The annealing treatment conditions are preferably a temperature of 120 to 180°C, a pressure of 0.005 to 0.015 MPa, and a time of 30 to 120 minutes.

[0157] Gases used for plasma treatment include oxygen, nitrogen, rare gases (such as argon), hydrogen, ammonia, and vinyl acetate. These gases may be used alone or in combination of two or more.

[0158] Another substrate may be laminated on the outermost surface of the laminate.

[0159] Examples of other substrates include heat-resistant resin films, prepregs that are precursors of fiber-reinforced resin sheets, laminates having heat-resistant resin film layers, and laminates having prepreg layers.

[0160] Prepreg is a sheet-like substrate obtained by impregnating a base material (such as short hemp and woven fabric) of reinforcing fibers (such as glass fibers and carbon fibers) with a thermosetting resin or a thermoplastic resin.

[0161] The heat-resistant resin film is a film containing one or more heat-resistant resins. Examples of the heat-resistant resin include polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, and liquid crystalline polyesteramide. Polyimide (particularly aromatic polyimide) is preferred.

[0162] As a lamination method, a method of thermocompression bonding the laminate and another substrate may be mentioned.

[0163] When the other substrate is a prepreg, the conditions for thermocompression bonding are preferably a temperature of 120 to 400° C., a vacuum atmosphere with a pressure of 20 kPa or less, and a compression pressure of 0.2 to 10 MPa.

[0164] Because the laminate comprises a polymer layer with excellent electrical properties, it is suitable for use as a printed circuit board material. Specifically, the laminate in this method can be used as a flexible metal-clad laminate or a rigid metal-clad laminate for the manufacture of printed circuit boards. It is particularly suitable as a flexible metal-clad laminate for the manufacture of flexible printed circuit boards.

[0165] A printed circuit board can be produced by etching the metal foil of the present laminate (metal foil with a polymer layer) in which the base layer is a metal foil to form a transmission circuit. Specifically, a printed circuit board can be produced by etching the metal foil to form a predetermined transmission circuit, or by electroplating the metal foil to form a predetermined transmission circuit using a semi-additive plating method (SAP method, MSAP method, etc.).

[0166] A printed circuit board made of a metal foil with a polymer layer comprises a transmission circuit formed of metal foil and a polymer layer in this order. Specific examples of the printed circuit board structure include: transmission circuit / polymer layer / prepreg layer; or transmission circuit / polymer layer / prepreg layer / polymer layer / transmission circuit.

[0167] In the manufacture of printed circuit boards, an interlayer insulating film, a solder resist, or a cover film can be formed on a transmission circuit. These interlayer insulating films, solder resist, and cover films can also be formed from this dispersion.

[0168] As mentioned above, the method for producing the powder, the powder, and the powder dispersion of the present invention have been described. However, the present invention is not limited to the configurations of the above-described embodiments.

[0169] For example, the powder and powder dispersion of the present invention may each be added with any other arbitrary configuration to the configuration of the above-described embodiment, or may be replaced with any arbitrary configuration that exhibits the same function.

[0170] Furthermore, in the method for producing the powder of the present invention, any other steps may be added to the configuration of the above-described embodiment, or may be replaced with any steps that produce the same effect.

[0171] Example

[0172] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following description.

[0173] 1. Preparation of Agglutinate

[0174] [Preparation of Agglutinate 1]

[0175] First, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (boiling point: 56°C, manufactured by AGC Corporation, "AE-3000"), methanol, and PPVE were added to a vacuum-evacuated stainless steel polymerization tank (internal volume: 1.3 L). TFE gas was added while stirring the interior of the polymerization tank, and the temperature inside the polymerization tank was maintained at 50°C.

[0176] Then, a 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether solution (initiator solution) containing 0.05 mass % of bis(perfluorobutyryl) peroxide was injected into the polymerization tank to initiate polymerization. TFE gas was injected to maintain the internal pressure of the polymerization tank at a constant 1.0 MPa, and polymerization was continued.

[0177] The initiator solution was intermittently injected into the polymerization tank so that the TFE gas consumption rate was 0.5 g / min. Simultaneously, 1 mL of a 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether solution containing 1% by mass of NAH was injected into the polymerization tank for every 5 g of TFE gas consumed.

[0178] 290 minutes after the start of the polymerization, the polymerization tank was cooled to complete the polymerization. Thereafter, the residual monomer gas in the polymerization tank was purged to atmospheric pressure to obtain a polymerization crude liquid 1.

[0179] Crude polymer solution 1 contained 13% by mass of polymer 1 (melting temperature: 300°C) having polar functional groups. Polymer 1 contained 98.0 mol% of TFE units, 1.9 mol% of PPVE units, and 0.1 mol% of NAH units, respectively. Furthermore, primary particles of polymer 1 (D50: 0.5 μm) were dispersed in 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether within crude polymer solution 1.

[0180] Water was added to the polymer crude solution 1, and the mixture was stirred to aggregate the particles. The aggregates were then recovered by solid-liquid separation and dried at 150°C for 15 hours to obtain aggregates 1 (D50: 1.5 mm) of primary particles of polymer 1.

[0181] [Preparation of Agglutination Material 2]

[0182] A polymerization crude liquid 2 was obtained in the same manner as in the polymerization crude liquid 1 except that the use of NAH was omitted.

[0183] The crude polymerization solution 2 contained 13% by mass of a polymer 2 (melting temperature: 305°C) without polar functional groups. This polymer 2 contained 98.7 mol% of TFE units and 1.3 mol% of PPVE units, respectively. Furthermore, in the crude polymerization solution 2, primary particles of polymer 2 (D50: 0.4 μm) were dispersed in 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0184] Agglomerate 2 (D50: 2.4 μm) was recovered from the polymerization crude solution 2 in the same manner as for the agglomerate 1.

[0185] 2. Powder production

[0186] [Example 1]

[0187] First, the aggregate 1 was fed into the rotary kiln of a rotary kiln (manufactured by Sanai Chemical Industry Co., Ltd.) and passed through it for heat treatment. The rotary kiln was heated to a temperature of 250°C for the aggregate 1. The rotary kiln was rotated at 7 rpm, and the residence time (heating time) of the aggregate in the rotary kiln was set to 30 minutes. The aggregate was fed at a rate that achieved a 10% fill rate within the rotary kiln, and the rotary kiln was tilted at an angle of 0.2° relative to the horizontal. The hardness of the aggregate after passing through the rotary kiln was 0.41 N / mm.

[0188] Next, the obtained agglomerate was pulverized with a reverse jet mill (manufactured by Hosokawa Micron Co., Ltd.) at a pulverization pressure of 0.65 MPa and a push to obtain Powder 1.

[0189] The D50 of the obtained powder 1 is 2 μm and the specific surface area is 3 m 2 / g. In addition, the particle size distribution of powder 1 was unimodal, and the full width at half maximum was 2.1 μm.

[0190] [Example 2]

[0191] Powder 2 was obtained in the same manner as in Example 1 except that agglomerate 2 was used.

[0192] The D50 of the obtained powder 2 is 4 μm and the specific surface area is 5 m 2 / g. In addition, the particle size distribution of Powder 2 was unimodal, and the full width at half maximum was 2.5 μm.

[0193] [Example 3]

[0194] Powder 3 was obtained in the same manner as in Example 1 except that the rotary kiln was heated so that the heating temperature of the aggregate 1 reached 200°C.

[0195] The D50 of the obtained powder 3 is 2 μm and the specific surface area is 6 m 2 / g. In addition, the particle size distribution of Powder 3 was unimodal, and the half-peak width was 2.8 μm.

[0196] [Example 4 (Comparative Example)]

[0197] Powder 4 was obtained in the same manner as in Example 1 except that the rotary kiln was not heated.

[0198] The D50 of the obtained powder 4 is 2 μm and the specific surface area is 12 m 2 In addition, the particle size distribution of powder 4 is broad.

[0199] [Example 5 (Comparative Example)]

[0200] Powder 5 was obtained in the same manner as in Example 1 except that the rotary kiln was driven so that the heating temperature of the aggregate 1 reached 330° C. and the retention time was 1 minute.

[0201] The D50 of the obtained powder 5 is 5 μm and the specific surface area is 6 m 2 / g. In addition, the particle size distribution of powder 5 is bimodal.

[0202] [Example 6 (Comparative Example)]

[0203] Powder 6 was obtained in the same manner as in Example 1 except that the agglomerate 1 was heated in an oven to a temperature of 250°C.

[0204] The D50 of the obtained powder 6 is 24 μm and the specific surface area is 6 m 2 / g. In addition, the particle size distribution of powder 6 is bimodal.

[0205] 3. Preparation of Powder Dispersion

[0206] 55 parts by mass of each of powders 1 to 6, 2 parts by mass of a surfactant ("Fergent 250" manufactured by Neos Corporation), and 43 parts by mass of N-methyl-2-pyrrolidone (NMP) were placed in a ball mill, and then ceramic balls were added and mixed for 1 hour to prepare powder dispersions 1 to 6.

[0207] 4. Measurement and Evaluation

[0208] 4-1. Measurement of hardness of aggregates

[0209] Using a strograph (manufactured by Toyo Seiki Co., Ltd.), the maximum load when the agglomerate was compressed at 0.5 mm / min was defined as the hardness of the agglomerate.

[0210] 4-2. Determination of specific surface area of ​​powder

[0211] The specific surface area of ​​each of the powders 1 to 6 was measured by the gas adsorption (constant volume method) BET multipoint method. The measuring apparatus used was NOVA4200e (manufactured by Quantachrome Instruments).

[0212] As a pretreatment, each powder 1-6 was vacuum degassed at 200°C for 30 minutes. Then, nitrogen gas was introduced while maintaining the temperature constant with liquid nitrogen to generate an adsorption isotherm. The specific surface area of ​​each powder 1-6 was determined at the relative pressure point where good linearity was achieved.

[0213] 4-3. Determination of D50 of Powder

[0214] The particle size distribution of each of the powders 1 to 6 was measured using a laser interferometer ("LA-960V2" manufactured by HORIBA, Ltd.), and D50 was determined.

[0215] A particle size distribution with one maximum is defined as unimodal, and a particle size distribution with two maxima is defined as bimodal.

[0216] Furthermore, bimodality in particle size distribution, which is observed when powders contain irregularly shaped particles, does not usually exist in practice.

[0217] 4-4. Evaluation of Aggregation of Powder Dispersion

[0218] Each powder dispersion 1 to 6 was passed through a 50 μm mesh. The solid content captured by the mesh was then dried and its mass was measured. The capture rate was calculated from the mass of the powder in the original powder dispersion using the following formula, and the cohesion was evaluated according to the following criteria.

[0219] Formula: Capture rate = mass of solid components captured by the metal mesh / mass of powder contained in the original powder dispersion

[0220] [Evaluation criteria]

[0221] ○: Capture rate is less than 5%

[0222] △: Capture rate is 5% or more and less than 10%

[0223] ×: Capture rate is above 10%

[0224] 4-5. Viscosity measurement of powder dispersion

[0225] The viscosity of each of the powder dispersions 1 to 6 was measured using a Brookfield viscometer (manufactured by Eiko Seiki Co., Ltd., “DV2T”) with an RV-2 rotor rotating at 60 rpm.

[0226] 4-6. Evaluation of viscosity-increasing properties of powder dispersions

[0227] Each powder dispersion 1 to 6 was stirred at 8000 rpm for 30 minutes using a homomixer, and the viscosity was measured in the same manner as in "4-5." The viscosity increase ratio of the dispersion before and after stirring was calculated according to the following formula and evaluated according to the following criteria.

[0228] Formula: Viscosity increase rate = {(viscosity after stirring / viscosity before stirring)-1}×100

[0229] [Evaluation criteria]

[0230] ○: Thickening rate less than 40%

[0231] △: Thickening rate is 40% or more and less than 60%

[0232] ×: Thickening rate is above 60%

[0233] 4-7. Evaluation of Surface Smoothness of Laminated Body

[0234] Powder dispersion 1 was applied to the surface of a stainless steel plate using an applicator to form a wet film. The stainless steel plate with the wet film was then passed through a drying oven at 100°C for 5 minutes to dry it and obtain a dry film. The dry film was then heated in a nitrogen oven at 350°C for 5 minutes. This yielded a laminate 1 comprising a stainless steel plate and, on its surface, a polymer layer containing a melt-sintered product of powder 1 as a formed product.

[0235] Laminates 2 to 6 were obtained in the same manner as for the laminate 1 except that the powder dispersion 1 was changed to the powder dispersions 2 to 6.

[0236] For each of laminates 1 to 6, the arithmetic mean surface roughness (Ra) of the polymer layer was determined using a surface roughness meter (Surfcom NEX100, manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B0601:2013 (ISO 4287:1997, Amd. 1:2009). The reference length Ir (critical value λc) used for the roughness curve when determining Ra was set to 0.8 mm.

[0237] [Evaluation criteria]

[0238] ○: Ra less than 0.4μm

[0239] △: Ra is 0.4 μm or more and less than 0.6 μm

[0240] ×: Ra is 0.6 μm or more

[0241] These results are also shown in Table 1 below.

[0242] [Table 1]

[0243]

[0244] Industrial Application Possibilities

[0245] The powder and powder dispersion of the present invention can be used to produce formed articles such as films, impregnations (prepregs, etc.), laminates (metal laminates such as copper-clad laminates, etc.), and can be used to produce formed articles for applications requiring releasability, electrical properties, water and oil repellency, chemical resistance, weather resistance, heat resistance, lubricity, and wear resistance. The molded articles formed from the dispersion of the present invention can be used as antenna components, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, coatings, cosmetics, and the like. Specifically, they can be used as wire coating materials, electrical insulating tapes, oil drilling insulating tapes, printed circuit board materials, separators, battery materials (electrode binder materials for lithium secondary batteries, fuel cells, etc.), copy rollers, covers for furniture, automobile dashboards, home appliances, etc., sliding members (load bearings, sliding shafts, valves, bearings, gears, cams, conveyor belts, food conveyor belts, etc.), tools (shovels, files, awls, saws, etc.), boilers, hoppers, pipes, ovens, barbecue molds, chutes, molds, toilets, and container coverings.

Claims

1. A method for producing a powder, comprising: causing a hot melt tetrafluoroethylene polymer aggregate to flow while heat treating it at a temperature greater than -100°C from the melting temperature of the tetrafluoroethylene polymer and below the melting temperature of the tetrafluoroethylene polymer, and then pulverizing it to obtain a powder having an average particle size greater than 1 μm and less than 10 μm and a specific surface area of ​​1 m 2 / g or more and less than 8m 2 / g, a powder of the tetrafluoroethylene polymer having a sharp single-peak particle size distribution with a full width at half maximum of 0.5 to 3.5 μm, The tetrafluoroethylene polymer is a tetrafluoroethylene polymer containing a perfluoro(alkyl vinyl ether)-based unit or a hexafluoropropylene-based unit and having a carbonyl group. The number of carbonyl groups in the tetrafluoroethylene polymer is 1×10 carbon atoms per 1×10 carbon atoms in the main chain. 6 The number of pieces is 10 to 5000.

2. The manufacturing method according to claim 1, wherein The average particle size of the agglomerates is 100 μm to 5 mm.

3. The manufacturing method according to claim 1 or 2, wherein: The agglomerate is heat-treated while being tumbled in a rotary kiln that rotates about a central axis.

4. The manufacturing method according to claim 3, wherein: The rotary kiln has an inclination angle relative to the horizontal direction of 0.01 to 5 degrees.

5. The manufacturing method according to claim 3, wherein: The rotating speed of the rotary kiln is 1 to 20 rpm.

6. The manufacturing method according to claim 3, wherein: The residence time of the agglomerate in the rotary kiln is 1 to 60 minutes.

7. The manufacturing method according to claim 1 or 2, wherein: The hardness of the agglomerate before the pulverization is 0.2 N / mm or more.

8. The manufacturing method according to claim 1 or 2, wherein: The aggregates are aggregates of particles of the tetrafluoroethylene-based polymer formed by polymerization of a raw material monomer of the tetrafluoroethylene-based polymer.

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