Method for storing dispersion liquid container, and dispersion liquid container

Abstract

Provided are: a method for storing a dispersion containing body in which a dispersion containing particles of a tetrafluoroethylene polymer and water is contained in a containing container, in which deterioration of the tetrafluoroethylene polymer and coloring of the dispersion are suppressed; and the dispersion containing body. Provided is a method for storing a dispersion liquid container, a dispersion liquid containing body is formed by containing a dispersion liquid containing tetrafluoroethylene polymer particles, a nonionic surfactant, and water in a container such that the liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by formula (1). The product of the volume ratio of the gas phase in the storage container and the gas-liquid interface area of the storage container is maintained in the range of 10,000-60,000, and the temperature is maintained in the range of more than 0 DEG C and 20 DEG C or less. (1) The theoretical liquid density of the dispersion liquid = (density of the dispersoid * volume ratio of the dispersoid) / (density of the dispersoid * volume ratio of the dispersoid + density of the dispersion medium * volume ratio of the dispersion medium).

Description

Technical Field

[0001] The present invention relates to a method for storing a container containing a dispersion of particles of a tetrafluoroethylene-based polymer and a dispersion container. Background Art

[0002] In recent years, in order to cope with the high speed and high frequency of communication devices, tetrafluoroethylene-based polymers having a low dielectric constant and a low dielectric loss tangent have attracted attention as insulating layer materials for printed circuit boards of communication devices. As a material for forming an insulating layer containing the polymer, an aqueous dispersion containing particles of a tetrafluoroethylene-based polymer is known. This aqueous dispersion has the versatility of equipment required for use and high selectivity for substrates to be coated and the like. On the other hand, its liquid physical properties are often insufficient, and improvement of liquid physical properties is being studied. Patent Document 1 proposes a PTFE aqueous dispersion containing an emulsion polymerization liquid and a dispersant of polytetrafluoroethylene (PTFE) fine particles having a specific particle size in a specified amount and having a foam volume ratio less than a specific amount. Prior Art Documents Patent Documents

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-182956 Summary of the Invention Technical Problem to be Solved by the Invention

[0004] On the other hand, there is still a lack of recognition from the viewpoint of long-term storage of aqueous dispersions. In addition to dispersion stability, there are also technical problems such as color change of the dispersion and deterioration of the quality of the molded article obtained from the dispersion after long-term storage due to continuous deterioration of the dispersed substances such as particles of the tetrafluoroethylene-based polymer, making it difficult to stabilize the quality. The present inventors have found that if the liquid density of a dispersion containing particles of a tetrafluoroethylene-based polymer and water is adjusted to a specific range and then contained in a container, and the product of the gas phase volume ratio in the container and the gas-liquid interface area of the container is maintained within a specific range and stored at a specific temperature, deterioration of the tetrafluoroethylene-based polymer and coloring of the dispersion are suppressed. It has also been found that in a molded article such as a polymer layer formed from the dispersion stored by this storage method, physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) brought about by the tetrafluoroethylene-based polymer are excellent, it has less coloring, foaming is suppressed, and the surface appearance is also excellent, thus completing the present invention. An object of the present invention is to provide a method for storing a dispersion container in which a dispersion containing particles of a tetrafluoroethylene-based polymer and water is contained in a container, and the dispersion container, in which deterioration of the tetrafluoroethylene-based polymer and coloring of the dispersion are suppressed. Means for Solving Technical Problems

[0005] The present invention has the following aspects. [1] A method for storing a dispersion liquid container, wherein a dispersion liquid containing particles of a tetrafluoroethylene-based polymer, a nonionic surfactant, and water is stored in a storage container in such a form that the liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by the following formula (1), and the product of the gas-phase volume ratio in the storage container and the gas-liquid interface area of the storage container is maintained in the range of 10,000 or more and 60,000 or less, and the temperature is maintained in the range of greater than 0 °C and 20 °C or less for storage. Theoretical liquid density of the dispersion liquid = (density of the dispersed substance × volume ratio of the dispersed substance) / (density of the dispersed substance × volume ratio of the dispersed substance + density of the dispersion medium × volume ratio of the dispersion medium) …… (1) [2] The storage method as in [1], wherein the tetrafluoroethylene-based polymer is thermally fusible and has an oxygen-containing polar group. [3] The storage method as in [1] or [2], wherein the average particle diameter of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm. [4] The storage method as in any one of [1] to [3], wherein the content of the particles of the tetrafluoroethylene-based polymer in the dispersion liquid is 25% by mass or more. [5] The storage method as in any one of [1] to [4], wherein the powder of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are mixed to prepare the dispersion liquid. [6] The storage method as in any one of [1] to [5], wherein in the dispersion liquid, with respect to the total of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water, the contents of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are 35 to 70% by mass, 1 to 15% by mass, and 15 to 64% by mass, respectively. [7] The storage method as in any one of [1] to [6], wherein the mass ratio of the nonionic surfactant to the content of the particles of the tetrafluoroethylene-based polymer in the dispersion liquid is 0.01 to 0.15. [8] The storage method as in any one of [1] to [7], wherein the nonionic surfactant is a silicone-based surfactant or an acetylene-based surfactant. [9] The storage method as in any one of [1] to [8], wherein the HLB value of the nonionic surfactant calculated by the Griffin formula is 3 to 16.

[10] The storage method according to any one of [1] to [9], wherein the dissolved oxygen amount in the dispersion liquid is in the range of 8 to 12 ppm.

[11] A dispersion liquid container, which is a dispersion liquid container formed by accommodating a dispersion liquid containing particles of a tetrafluoroethylene-based polymer, a nonionic surfactant, and water in an accommodation container. The liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by the following formula (1). The product of the gas-phase volume ratio in the accommodation container and the gas-liquid interface area of the accommodation container is in the range of 10,000 or more and 60,000 or less. Theoretical liquid density of the dispersion liquid = (density of the dispersed substance × volume ratio of the dispersed substance) / (density of the dispersed substance × volume ratio of the dispersed substance + density of the dispersion medium × volume ratio of the dispersion medium) …… (1).

[12] The dispersion liquid container according to

[11] , wherein the tetrafluoroethylene-based polymer is thermally fusible and has an oxygen-containing polar group.

[13] The dispersion liquid container according to

[11] or

[12] , wherein the average particle diameter of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm.

[14] The dispersion liquid container according to any one of

[11] to

[13] , wherein in the dispersion liquid, with respect to the total of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water, the contents of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are 35 to 70% by mass, 1 to 15% by mass, and 15 to 64% by mass in sequence.

[15] The dispersion liquid container according to any one of

[11] to

[14] , wherein the nonionic surfactant is a silicone-based surfactant or an acetylene-based surfactant. Advantages of the Invention

[0006] According to the present invention, a storage method of a dispersion liquid container in which a dispersion liquid containing particles of a tetrafluoroethylene-based polymer and water is accommodated in an accommodation container, and the dispersion liquid container, in which deterioration of the tetrafluoroethylene-based polymer and coloring of the dispersion liquid are suppressed, can be obtained. A molded article such as a coating film having excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) brought by the tetrafluoroethylene-based polymer, less coloring, suppressed foaming, and excellent surface appearance can be formed from the dispersion liquid stored by this storage method. Specifically, a laminate having a polymer layer formed from the dispersion liquid can be formed. Detailed Embodiments

[0007] The following terms have the following meanings. "Average particle size (D50)" is the volume-based cumulative 50% diameter of particles or fillers determined by the laser diffraction / scattering method. That is, the particle size distribution is measured by the laser diffraction / scattering method, and the cumulative curve is obtained with the total volume of the particle group as 100%. The particle size at the point where the cumulative volume reaches 50% on this cumulative curve. The D50 of particles or fillers is obtained by dispersing the powder in water and analyzing it by the laser diffraction / scattering method using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., LA-920 analyzer). "Average particle size (D90)" is the volume-based cumulative 90% diameter of particles obtained in the same manner as D50. The specific surface area of particles or fillers is a value measured by the gas adsorption (constant volume method) BET multi-point method for particles and calculated using NOVA4200e (manufactured by Quantachrome Instruments, USA). "Melting temperature" is the temperature corresponding to the maximum value of the melting peak of a polymer measured by differential scanning calorimetry (DSC). "Glass transition temperature (Tg)" is a value measured by analyzing a polymer by dynamic viscoelasticity measurement (DMA). "Viscosity" refers to the value obtained by measuring the composition with a B-type viscometer at 25°C under the condition of a rotation speed of 30 rpm. The measurement is repeated 3 times, and the average value of the 3 measurement values is taken. "Thixotropy ratio" refers to the value calculated by dividing the viscosity η1 measured at 25°C under the condition of a rotation speed of 30 rpm by the viscosity η2 measured at a rotation speed of 60 rpm. The measurement of each viscosity is repeated 3 times, and the average value of the 3 measurement values is taken. The "HLB (Hydrophilic-Lipophilic Balance) value" of a surfactant is a value defined by the following calculation formula (Griffin formula) by the Griffin method. HLB value = 20 × [sum of chemical formula weights of hydrophilic part] / molecular weight The "unit" in a polymer refers to an atomic group based on the monomer formed by polymerization of the monomer. The unit can be a unit directly formed by a polymerization reaction, or a unit in which a part of the unit is converted into another structure by treating the polymer. Hereinafter, the unit based on monomer a is also simply referred to as "monomer a unit".

[0008] The storage method of the present invention (hereinafter also referred to as "this method") is a method for storing a dispersion liquid container: a dispersion liquid (hereinafter also referred to as "this dispersion liquid") containing particles of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") (hereinafter also referred to as "F particles"), a nonionic surfactant, and water is contained in a storage container in such a form that the liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by the following formula (1), thereby forming a dispersion liquid container (hereinafter also referred to as "this container"), and the product of the gas-phase volume ratio (unit: volume%) in the storage container and the gas-liquid interface area of the storage container (unit: cm 2 ) is maintained in the range of 10,000 or more and 60,000 or less, and the temperature is maintained in the range greater than 0°C and 20°C or less for storage. Theoretical liquid density of the dispersion liquid = (density of the dispersed substance × volume ratio of the dispersed substance) / (density of the dispersed substance × volume ratio of the dispersed substance + density of the dispersion medium × volume ratio of the dispersion medium) …… (1). Here, the "dispersed substance" in the formula refers to components such as F particles in the components of the dispersion liquid described later that are insoluble in the dispersion medium and are dispersed, and the "dispersion medium" refers to a liquid dispersion medium such as water and components dissolved in the liquid dispersion medium.

[0009] According to this method, the deterioration of the F polymer in this dispersion liquid and the coloring of this dispersion liquid can be suppressed for a long time. Moreover, from this dispersion liquid to which this method is applied, shaped articles such as a coating film having excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) brought about by the F polymer, with little coloring, suppressed foaming, and excellent adhesiveness and surface appearance can be formed, specifically, a laminate having a polymer layer formed from this dispersion liquid. In addition, in this specification, the so-called "excellent surface appearance" includes any one of excellent surface smoothness such as "less surface roughness" or excellent appearance such as "no stripes, cracks, or defects on the surface" visually recognized or observed by an analysis device. In this dispersion liquid to which this method is applied, the reason why the deterioration and coloring of the F polymer are suppressed for a long time is not necessarily clear, but it can be considered as follows.

[0010] The nonionic surfactant contained in this dispersion not only adheres to the F particles to improve their dispersion in the liquid, but also forms a film like a Langmuir film at the interface between the gas phase part and the liquid phase part of the dispersion in the container when this dispersion is contained in a container to form a contained body. At this time, if the relationship between the theoretical liquid density and the actual liquid density of this dispersion is within a specified range, this dispersion can also be regarded as being in a state where slightly bubbles enter and are contained therein. Furthermore, if the ratio of the gas-liquid interface area to the gas phase volume of the container of this contained body satisfies a specified relationship, it is considered that the nonionic surfactant makes it easier to achieve the gas-liquid equilibrium in this contained body. By the achievement of this gas-liquid equilibrium, it is considered that the dissolved oxygen amount in this dispersion in the contained body is constant, and the bactericidal action or bleaching action caused by the radicalization or ionization of oxygen is easily enhanced. Even during long-term storage, it is speculated that the hue of this dispersion is stable. On the other hand, since this method is carried out at a low temperature within a specified temperature range during storage, it is considered that the deterioration or degradation of the F polymer caused by oxygen is easily suppressed. As a result, by this method, it is speculated that the deterioration and coloring of the F polymer are suppressed in the long term. This tendency is particularly remarkable when the F polymer in this dispersion is thermally fusible and has an oxygen-containing polar group, when the average particle diameter (D50) of the F particles is 1 μm or more and less than 10 μm, and when the content of the F particles in this dispersion is 25% by mass or more. Especially in the former case, the adhesiveness of the molded article formed from the dispersion after long-term storage is easily improved. Moreover, in this dispersion, if the contents of the F particles, the nonionic surfactant, and water are within specified ranges with respect to the total of the F particles, the nonionic surfactant, and water, and the dissolved oxygen amount of this dispersion is within a specified range, the deterioration and coloring of the F polymer in this dispersion are more easily suppressed even after long-term storage.

[0011] The F polymer as a constituent of this dispersion is a polymer containing units based on tetrafluoroethylene (hereinafter also referred to as "TFE") (hereinafter also referred to as "TFE units"). The F polymer can be thermally fusible or non-thermally fusible. Here, a thermally fusible polymer means a polymer having a temperature at which the melt flow rate is 1 to 1000 g / 10 minutes under a load of 49 N. The melting temperature of the thermally fusible F polymer is preferably 180 °C or higher, more preferably 200 °C or higher. The melting temperature of the F polymer is preferably 325 °C or lower, more preferably 320 °C or lower. At this time, the heat resistance of molded articles such as coatings (polymer layers) formed from the dispersion to which this method is applied is easily excellent.

[0012] The glass transition temperature of the F polymer is preferably 50 °C or higher, more preferably 75 °C or higher. The glass transition temperature of the F polymer is preferably 150 °C or lower, more preferably 125 °C or lower. The fluorine content of the F polymer is preferably 70% by mass or higher, more preferably 72 - 76% by mass. The surface tension of the F polymer is preferably 16 - 26 mN / m. Among them, the surface tension of the F polymer can be measured by placing a droplet of the wiping tension test mixture (manufactured by Wako Pure Chemical Industries, Ltd.) specified in JIS K 6768 on a flat plate made of the F polymer.

[0013] The F polymer is preferably polytetrafluoroethylene (PTFE), a polymer containing TFE units and ethylene-based units (ETFE), a polymer containing TFE units and propylene-based units, a polymer containing TFE units and perfluoro(alkyl vinyl ether) (PAVE) units (PAVE units) (PFA), a polymer containing TFE units and hexafluoropropylene units (FEP), more preferably PFA and FEP, and further preferably PFA. These polymers may also contain units based on other comonomers. Examples of PTFE include low molecular weight PTFE and modified PTFE. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, and CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), more preferably PPVE.

[0014] The F polymer preferably has an oxygen-containing polar group, more preferably has a hydroxyl group-containing group or a carbonyl group-containing group, and further preferably has a carbonyl group-containing group. In this case, the dispersion liquid to which this method is applied easily has excellent dispersion stability and operability. Moreover, molded articles such as a coating film (polymer layer) formed from this dispersion liquid are excellent in physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) and their surface appearance. The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl group-containing group is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a urethane group (-OC(O)NH2), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.), and a carbonate group (-OC(O)O-), more preferably an acid anhydride residue. When the F polymer has an oxygen-containing polar group, the number of oxygen-containing polar groups in the F polymer is relative to each 1×10 6The number of carbon atoms in the main chain is preferably from 10 to 5000, more preferably from 100 to 3000. Among them, the number of oxygen-containing polar groups in the F polymer can be quantified according to the composition of the polymer or the method described in International Publication No. 2020 / 145133.

[0015] The oxygen-containing polar groups can be included in the monomer-based units in the F polymer or in the end groups of the main chain of the F polymer, and the former is preferred. As the latter method, examples include F polymers having oxygen-containing polar groups as end groups derived from polymerization initiators, chain transfer agents, etc., and F polymers obtained by subjecting F polymers to plasma treatment or ionization radiation treatment.

[0016] The F polymer is preferably a polymer having a carbonyl group-containing polymer containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on monomers having a carbonyl group and containing 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol% of these units in this order relative to all units. As a specific example of this F polymer, the polymers described in International Publication No. 2018 / 16644 can be cited. The monomers having a carbonyl group are preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0017] In the present invention, the D50 of the F particles is preferably 1 μm or more and less than 10 μm. The F particles can be solid particles or non-hollow particles. The F particles can also be secondary particles formed from nm-sized fine particles. The D50 of the F particles is preferably 1.0 μm or more, more preferably 1.5 μm or more. The D50 of the F particles is preferably 6 μm or less, more preferably 5 μm or less. In addition, the D90 of the F particles is preferably 8 μm or less, more preferably 6 μm or less. When the D90 of the F particles is below the above range, the number of coarse particles is likely to decrease, and the above-described mechanism of action is more likely to appear.

[0018] The specific surface area of the F particles is preferably 1 to 25 m 2 / g, more preferably 6 to 15 m 2 / g. In this case, the dispersion stability and operability of the dispersion are likely to be excellent, and molded articles such as coatings (polymer layers) formed from the dispersion are likely to be excellent in physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) and their surface appearance.

[0019] The F particles are particles containing an F polymer and are preferably composed of an F polymer. The F particles are more preferably particles of a thermally fusible F polymer having an oxygen-containing polar group and a melting temperature of 200 to 325 °C. In this case, the above-mentioned mechanism of action is more likely to appear, and the aggregation of the F particles is also easily suppressed. The F particles may also contain a resin or an inorganic compound other than the F polymer, and may form a core-shell structure having an F polymer as the core and a resin or an inorganic compound other than the F polymer as the shell, or a core-shell structure having an F polymer as the shell and a resin or an inorganic compound other than the F polymer as the core. Here, examples of the resin other than the F polymer include aromatic polyesters, polyamideimides, polyimides, and maleimides, and examples of the inorganic compound include silica and boron nitride.

[0020] One type of F particles can be used, or two or more types can be used. In addition, the F particles can be used in combination with particles of a non-thermally fusible tetrafluoroethylene-based polymer. As the F particles, particles of a thermally fusible F polymer having a melting temperature of 200 to 325 °C are preferred, and particles of a thermally fusible F polymer having an oxygen-containing polar group and a melting temperature of 200 to 325 °C are more preferred. As the particles of the non-thermally fusible tetrafluoroethylene-based polymer, particles of non-thermally fusible PTFE are preferred. In this case, the aggregation inhibitory effect of the particles of the thermally fusible F polymer and the fibrillation maintaining effect of the non-thermally fusible tetrafluoroethylene-based polymer are balanced, and the dispersibility of the present dispersion using this method is easily improved. In addition, in a formed article such as a coating film (polymer layer) formed therefrom, the electrical properties of the non-thermally fusible tetrafluoroethylene-based polymer are easily exhibited at a high level.

[0021] The content of the F particles in the present dispersion is preferably 25% by mass or more, more preferably 35% by mass or more. The content of the F particles is preferably 75% by mass or less, more preferably 70% by mass or less.

[0022] Examples of the nonionic surfactant as a constituent of the present dispersion include glycol-based surfactants, acetylene-based surfactants, fluorine-based surfactants, or silicone-based surfactants. Among them, silicone-based surfactants or alkynediol-based surfactants are preferred. As the silicone-based surfactant, polyoxyalkylene-modified dimethylsiloxane having a polyoxyalkylene structure as a hydrophilic part and a polydimethylsiloxane structure as a hydrophobic part is more preferred. Polyoxyalkylene-modified dimethylsiloxane may have a polydimethylsiloxane unit in the main chain (-(CH3)2SiO 2 / 2-), it may also have polydimethylsiloxane units in the side chain, or may have polydimethylsiloxane units in both the main chain and the side chain. The polyoxyalkylene-modified polydimethylsiloxane preferably has units of dimethylsiloxane in the main chain and is a polyoxyalkylene-modified polydimethylsiloxane having oxyalkylene groups in the side chain, or a polyoxyalkylene-modified polydimethylsiloxane having units of dimethylsiloxane in the main chain and oxyalkylene groups at the ends of the main chain. In addition, the oxyalkylene groups contained in the polyoxyalkylene-modified dimethylsiloxane may be composed of only one kind of oxyalkylene group, or may be composed of two or more kinds of oxyalkylene groups. In the latter case, different kinds of oxyalkylene groups may be randomly linked or block-linked. Examples of such silicone-based surfactants include "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", "BYK-3456" (manufactured by BYK-Chemie Japan Co., Ltd.), "KF-6011", "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0023] Alkynediol-based surfactants are surfactants having a carbon-carbon triple bond in the molecule, and examples include: alkynediol (having an alkyne bond and two hydroxyl groups in the same molecule) surfactants, and surfactants obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to alkynediols. Examples of such alkynediol-based surfactants include: "SURFYNOL (registered trademark)" series, "OLFINE (registered trademark)" series (both manufactured by Nissin Chemical Industry Co., Ltd.); "ACETYLENOL (registered trademark)" series (manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0024] The HLB value calculated by the Griffin formula for the nonionic surfactant is preferably 1 to 18, preferably 3 or more, more preferably 6 or more, and further preferably 10 or more. The HLB value is preferably 16 or less, more preferably 15 or less. The HLB value of the nonionic surfactant is preferably 3 to 16, more preferably 8 to 15, and further preferably 10 to 15. When the HLB value of the nonionic surfactant is within the above range, the above-mentioned action mechanism in this dispersion is more likely to appear, and even after long-term storage, the coloring of this dispersion is easily suppressed. Moreover, the molded articles such as coatings obtained from this dispersion using this method have less coloring, suppressed foaming, and excellent adhesiveness and surface appearance. Furthermore, the uniform fluidity of this dispersion after long-term storage is easily maintained, and the recoverability from the storage container is easily improved. One kind of nonionic surfactant can be used, or two or more kinds can be used.

[0025] In this method, the mass ratio of the nonionic surfactant in this dispersion liquid to the content of F particles is preferably in the range of 0.01 to 0.15, more preferably in the range of 0.03 to 0.1. When the mass ratio of the nonionic surfactant to the content of F particles is within the above range, the above action mechanism is more likely to appear.

[0026] The water constituting this dispersion liquid functions as a dispersion medium. As the dispersion medium, other dispersion media other than water may be contained in a small amount within the range where the effects of this method are exerted. It is preferable to mix this other dispersion medium with water, and it is preferably at least one selected from amides, ketones, and esters. Examples of the amide include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N,N-diethylformamide, hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolidinone, and the like. Examples of the ketone include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, and cycloheptanone. Examples of the ester include methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, and γ-valerolactone. They can be used alone as one kind, or two or more kinds can be used in combination.

[0027] In this method, in this dispersion liquid, with respect to the total of F particles, nonionic surfactant, and water, the contents of F particles, nonionic surfactant, and water are 35 to 70% by mass, 1 to 15% by mass, and 15 to 64% by mass, respectively. When the contents of each constituent component are within the above range, the above action mechanism is more likely to appear, and even after long-term storage, the coloring of this dispersion liquid is easily suppressed.

[0028] In this method, this dispersion liquid may further contain an inorganic filler. In this case, shaped articles such as a coating film formed from this dispersion liquid are likely to be excellent in electrical properties and low linear expansibility. The shape of the inorganic filler can be any one of spherical, needle-like (fibrous), and plate-like, and specifically can be spherical, scaly, layered, leaf-like, almond-like, columnar, cockscomb-like, equiaxial, leaf-shaped, mica-like, massive, flat plate-like, wedge-shaped, rosette-shaped, mesh-like, and prismatic. As inorganic fillers, examples include: silicon compounds such as quartz powder, silica, wollastonite, talc, silicon nitride, silicon carbide, mica, etc.; nitrogen compounds such as boron nitride, aluminum nitride, etc.; metal oxides such as alumina, zinc oxide, titanium oxide, cerium oxide, beryllium oxide, magnesium oxide, nickel oxide, vanadium oxide, copper oxide, iron oxide, silver oxide, etc.; carbon fibers; carbon allotropes such as graphite, graphene, carbon nanotubes, etc.; metals such as silver and copper. One type of inorganic filler can be used, or two or more types can be used in combination. The D50 of the inorganic filler is preferably 0.1 to 50 μm. The surface of the inorganic filler can be surface-treated with a silane coupling agent. When this dispersion liquid contains an inorganic filler, the content of the inorganic filler in this dispersion liquid is preferably 1 to 25% by mass.

[0029] In this method, this dispersion liquid may further contain an aromatic polymer. In this case, it is preferable from the viewpoint of enabling better dispersion stability of the F particles. The aromatic polymer can be contained in the form of non-hollow particles, or can be dissolved or dispersed in a liquid dispersion medium such as water constituting this dispersion liquid and other dispersion media contained as required (hereinafter, water, other dispersion media, etc. are collectively referred to as "liquid dispersion media"). Examples of the aromatic polymer include polyester resins such as liquid crystalline aromatic polyesters, polyimide resins, polyamideimide resins, epoxy resins, maleimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. Among them, at least one aromatic imide polymer selected from aromatic polyimides, aromatic polyamic acids, aromatic polyamideimides, and precursors of aromatic polyamideimides is more preferable. The aromatic polymer is preferably contained in the form of a varnish dissolved in the liquid dispersion medium.

[0030] Specific examples of the aromatic imide polymer include the "UBE" series (manufactured by UBE Industries, Ltd.), the "Neopulim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company, Inc.), the "SPIXAREA (registered trademark)" series (manufactured by Somal Co., Ltd.), the "Q-pilon (registered trademark)" series (manufactured by PI Technology Research Institute), the "WINGO" series (manufactured by WINGO Technology Co., Ltd.), the "Tohmide (registered trademark)" series (manufactured by T&K TOKA Co., Ltd.), the "KPI-MX" series (manufactured by Kawamura Sangyo Co., Ltd.), "HPC-1000", and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.). When the dispersion liquid further contains an aromatic polymer, the content of the aromatic polymer relative to the F particles is preferably 1 to 25% by mass.

[0031] The dispersion liquid may further contain various additives such as a thixotropy imparting agent, a viscosity modifier, an antifoaming agent, a plasticizer, a weather resistance agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a brightening agent, a colorant, a conductive agent, a mold release agent, a flame retardant, etc.

[0032] In this method, the dissolved oxygen amount of the dispersion liquid is preferably in the range of 8 to 12 ppm. When the dissolved oxygen amount is within the above range, it is easy to make the dissolved oxygen amount of the dispersion liquid in the present container constant through the gas-liquid equilibrium in the above action mechanism, and the effects of the present invention are more easily exerted.

[0033] In this method, the viscosity of the dispersion liquid is preferably 10 mPa·s or more, more preferably 100 mPa·s or more. The viscosity of the dispersion liquid is preferably 10000 mPa·s or less, more preferably 3000 mPa·s or less. In this case, the coating property of the dispersion liquid is excellent, and it is easy to form shaped articles such as a coating film (polymer layer) with an arbitrary thickness. Moreover, the physical properties of the F polymer in the shaped article formed from the dispersion liquid within the viscosity range of this range are easily highly manifested. The thixotropy ratio of the dispersion liquid is preferably 1.0 to 2.5. In this case, the coating property and homogeneity of the dispersion liquid are excellent, and it is easy to generate a denser shaped article.

[0034] In this method, from the viewpoint of improving the long-term storage stability, the pH value of the dispersion liquid is more preferably 8 to 10. The pH value of the dispersion liquid can be adjusted by a pH regulator (amine, ammonia, citric acid, etc.) or a pH buffer (tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate, ammonium acetate, etc.).

[0035] The dispersion liquid can be obtained by mixing F particles, a nonionic surfactant, water, and the above other dispersion media, inorganic fillers, aromatic polymers, additives, etc. used as required. The dispersion can be obtained by mixing F particles, a nonionic surfactant, and water together, or can be mixed separately in sequence, or a masterbatch of these substances can be prepared in advance and mixed with the remaining components. The order of mixing is not particularly limited. In addition, the mixing method can be a one-time mixing or a multi-time mixing. For example, from the viewpoint of easily improving the dispersion stability of F particles, it is preferable to pre-disperse F particles in a part of water, then add a nonionic surfactant and mix, and add the obtained mixture to the remaining water to obtain the dispersion liquid. The nonionic surfactant can be added directly or in the form of an aqueous solution. Additionally, when further mixing the above-mentioned other dispersion media, inorganic fillers, aromatic polymers, additives, etc. as needed, they can be mixed together when the F particles are mixed with water, or the components can be added and mixed sequentially, or they can be mixed when adding the above mixture of F particles, water, and nonionic surfactant to water.

[0036] Furthermore, this dispersion liquid of the present method is preferably prepared by mixing the powder of the F polymer, a nonionic surfactant, and water. Here, the powder of the F polymer can be an aggregate of F particles, an aggregate of F particles themselves, or an aggregate formed by the aggregation of a part of the F particles. The powder of the F polymer is preferably obtained by subjecting TFE and other monomers to radical polymerization in a polymerization medium to produce the F polymer, recovering the granular F polymer by removing the polymerization medium, performing mechanical pulverization treatment with a jet mill or the like, and then performing classification as needed. Additionally, as the powder of the F polymer, powders formed from thermally fusible fluorine-containing copolymers obtained by radical polymerization in a polymerization medium, i.e., commercially available PFA powders (such as Fluon PFA P-62X, Fluon PFA P-63, etc., all manufactured by AGC Inc.) or ETFE powders, can also be used.

[0037] Examples of the mixing device used to obtain this dispersion liquid include: stirring devices equipped with blades such as Henschel mixers, pressure kneaders, Banbury mixers, and planetary mixers; pulverization devices using media such as ball mills, crushers, basket mills, sand mills, sand rollers, DYNO mills, DISPERMAT dispersers, SC mills, Spike mills, and stirring mills; and dispersion devices equipped with other mechanisms such as microfluidizers, nanonizers, Ultimaizer dispersers, ultrasonic homogenizers, dissolvers, dispersers, high-speed impeller dispersers, thin-film swirling high-speed mixers, self-rotating and revolving mixers, and V-type mixers.

[0038] In this method, the dispersion liquid is accommodated in an accommodation container in such a form that the liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% relative to the theoretical liquid density of the dispersion liquid calculated by the following formula (1) to form a dispersion liquid accommodation body. The theoretical liquid density of the dispersion liquid = (the density of the dispersed substance × the volume ratio of the dispersed substance) / (the density of the dispersed substance × the volume ratio of the dispersed substance + the density of the dispersion medium × the volume ratio of the dispersion medium) …… (1) As a means of adjusting the liquid density of this dispersion liquid to be within the above range relative to the theoretical liquid density, examples include agitation treatment using a homodisper, defoaming treatment using a vacuum degasser, and foam adjustment treatment using an antifoaming agent. In addition, the liquid density of this dispersion liquid can be measured using a Gerussac type specific gravity bottle according to the means described in the examples below.

[0039] In addition, the product of the gas phase volume ratio (unit: volume %) in the storage container in the dispersion liquid storage body and the gas-liquid interface area (unit: cm 2 ) of the storage container is 10,000 or more. In addition, the above product is 60,000 or less, preferably 40,000 or less, and more preferably 20,000 or less. Furthermore, the temperature of the dispersion liquid storage body is maintained within a range greater than 0°C and 20°C or less for storage. When the liquid density of this dispersion liquid is within the above range and the numerical range of the above product is within the above range, the above mechanism of action is likely to be clearly manifested.

[0040] As the storage container, metal containers such as drums, lift tanks, and 18-liter tanks (one-bucket tanks) that are usually used as containers for the storage and transfer of chemicals can be used. In addition, from the perspective of performing higher-level storage management, as the storage container, a container with a non-metallic material on the inner side of the container in contact with this dispersion liquid can also be used. This container can be a container composed of a single layer of a resin such as polyolefin, ceramics, or glass with excellent water resistance and chemical resistance, or a laminated container with them as the innermost layer.

[0041] The dielectric constant of the molded article formed from this dispersion liquid to which this method is applied is preferably greater than 1.0 and 2.4 or less. In addition, the tangent of the dielectric loss angle of the molded article is preferably greater than 0.0010 and 0.0022 or less. The thermal conductivity of the molded article is preferably 1 W / m·K or more.

[0042] If this dispersion liquid to which this method is applied is, for example, subjected to a molding method such as extrusion into a sheet, a molded article such as a sheet containing an F polymer can be formed. The sheet obtained by extrusion can be further subjected to pressure molding, calendering, etc. for casting. The sheet is preferably further heated to remove the liquid dispersion medium and the F polymer is fired.

[0043] The thickness of the sheet formed from this dispersion liquid to which this method is applied is preferably 1 to 1000 μm. The preferred ranges of the dielectric constant, tangent of the dielectric loss angle, and thermal conductivity of the sheet are the same as those of the dielectric constant, tangent of the dielectric loss angle, and thermal conductivity of the above-mentioned molded article, respectively. In addition, the thermal conductivity of the sheet refers to the thermal conductivity in the in-plane direction of the sheet. The linear expansion coefficient of the sheet is preferably 10 to 100 ppm / °C.

[0044] Laminating the sheet on a substrate can form a laminate. Examples of the manufacturing method of the laminate include a method of extrusion molding the present dispersion liquid applied with this method on the substrate, a method of thermocompression bonding the sheet and the substrate, etc. Examples of the substrate include: metal substrates such as metal foils of copper, nickel, aluminum, titanium, and their alloys; films of heat-resistant resins such as polyimide, polyamide, polyether amide, polyphenylene sulfide, polyallyl ether ketone, polyamideimide, liquid crystalline polyester, and tetrafluoroethylene-based polymers; prepreg substrates (precursors of fiber-reinforced resin substrates), ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride; and glass substrates.

[0045] Examples of the shape of the substrate include planar, curved, and uneven shapes. In addition, the shape of the substrate can be any one of foil-like, plate-like, film-like, and fiber-like. The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm. The surface of the substrate can be surface-treated with a silane coupling agent. The peel strength between the sheet and the substrate is preferably 10 to 100 N / cm or more.

[0046] In addition, if the present dispersion liquid applied with this method is disposed on the surface of the substrate and heated to form a polymer layer containing the F polymer (hereinafter also referred to as the "F layer"), a laminate having a substrate layer composed of the substrate and the F layer in sequence can be obtained. The F layer is preferably formed by disposing the present dispersion liquid applied with this method on the surface of the substrate, heating to remove the liquid dispersion medium, and further heating to burn the F polymer. If the substrate is separated from the laminate, a sheet containing the F polymer can be obtained. Examples of the substrate include the same substrates as those that can be laminated with the above sheet, and their preferred manners are also the same.

[0047] Examples of the method of disposing the present dispersion liquid applied with this method include a coating method, a droplet ejection method, and an impregnation method. The roll coating method, the knife coating method, the bar coating method, the die coating method, or the spray method is preferred. The heating for removing the liquid dispersion medium is preferably carried out at 100 to 200 °C for 0.1 to 30 minutes. The heating for burning the F polymer is preferably carried out at a temperature above the burning temperature of the F polymer, more preferably at 360 to 400 °C for 0.1 to 30 minutes. Examples of the heating device in each heating step include an oven and a ventilation drying furnace. The heat source in the device can be a contact heat source (hot air, hot plate, etc.) or a non-contact heat source (infrared rays, etc.). In addition, each heating step can be carried out under normal pressure or under reduced pressure. In addition, the atmosphere in each heating step can be any one of an air atmosphere, an inert gas (helium, neon, argon, nitrogen, etc.) atmosphere.

[0048] The F layer is formed through the steps of disposing and heating the present dispersion liquid to which this method has been applied. These steps can be carried out one by one or repeated more than twice. For example, the present dispersion liquid to which this method has been applied can be disposed on the surface of a substrate and heated to form the F layer, and further, the present dispersion liquid to which this method has been applied can be disposed on the surface of the said F layer and heated to form a second F layer. In addition, the present dispersion liquid to which this method has been applied can be disposed on the surface of a substrate, and in the stage of heating to remove the liquid dispersion medium, the present dispersion liquid to which this method has been applied can be further disposed on its surface and heated to form the F layer. The present dispersion liquid to which this method has been applied can be disposed only on one surface of the substrate or on both surfaces of the substrate. In the former case, a laminate having a substrate layer and an F layer on one surface of the substrate layer is obtained, and in the latter case, a laminate having a substrate layer and F layers on both surfaces of the substrate layer is obtained.

[0049] As a preferred specific example of the laminate, there can be cited: a metal-clad laminate having a metal foil and an F layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and F layers on both surfaces of the polyimide film. The preferred ranges of the dielectric constant, dielectric loss tangent, thermal conductivity, coefficient of linear expansion, and peel strength between the F layer and the substrate layer of the F layer are the same as the preferred ranges of the dielectric constant, dielectric loss tangent, thermal conductivity, coefficient of linear expansion, and peel strength between the sheet and the substrate of the sheet formed from the present dispersion liquid described above.

[0050] The present dispersion liquid to which this method has been applied can be used as a material for imparting insulation, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and thermal conductivity. The present dispersion liquid to which this method has been applied can specifically be used for printed wiring boards, thermal interface materials, substrates for power modules, coils used in power equipment such as motors, in-vehicle engines, heat exchangers, tubes, syringes, ampoules, medical wires, secondary batteries such as lithium-ion secondary batteries, primary batteries such as lithium batteries, radical batteries, solar cells, fuel cells, lithium-ion capacitors, hybrid capacitors, capacitors (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical switch elements, electrode adhesives, electrode separators, and electrodes (positive electrodes and negative electrodes). In addition, the dispersion liquid to which this method is applied can also be used as an adhesive for bonding components. Specifically, this dispersion liquid can be used for: bonding of ceramic components, bonding of metal components, bonding of electronic components such as IC chips, resistors, and capacitors on the substrates of semiconductor elements or module components, bonding of circuit boards and heat sinks, and bonding of LED chips on substrates.

[0051] The formed articles such as sheets formed from the dispersion liquid to which this method is applied, and laminates can be used as antenna components, printed circuit boards, aircraft components, automotive components, sports equipment, food industry supplies, heat dissipation components, etc. Specifically, it can be used as: wire coating materials (such as aircraft wires), enameled wire coating materials used in motors of electric vehicles, etc., electrical insulating tapes, insulating tapes for oil exploration, oil pipelines, hydrogen tanks, materials for printed circuit boards, separation membranes (precision filtration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode adhesives (for lithium secondary batteries, fuel cells, etc.), copying rollers, furniture, covers for automotive instrument panels, home appliance products, etc., sliding components (load bearings, sliding shafts, sliding shafts, valves, bearings, bushings, seals, thrust washers, wear-resistant rings, pistons, sliding switches, gears, cams, belt conveyors, belts for food transportation), tension ropes, wear-resistant pads, wear-resistant strips, tubular lamps, test sockets, wafer guides, wear components of centrifugal pumps, chemical and water supply pumps, tools (shovels, files, chisels, saws), boilers, hoppers, pipelines, ovens, baking molds, chutes, racket strings, plastic molds, toilets, container coating materials, mounting heat dissipation substrates for power devices, heat dissipation components for wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat sinks, metal heat dissipation plates, blades of windmills or wind power generation equipment or aircraft, frames of computers or monitors, electronic device materials, interior and exterior automotive trims, sealing materials for processing machines or vacuum furnaces that perform heat treatment under low oxygen, plasma processing devices, etc., heat dissipation components inside the processing units of sputtering or various dry etching devices, electromagnetic wave shields.

[0052] The formed articles such as sheets and laminates formed from the dispersion liquid to which this method is applied can be used as: electronic substrate materials such as flexible printed circuit boards and rigid printed circuit boards, protective films or heat dissipation substrates, especially heat dissipation substrates for automobiles.

[0053] In addition, the dispersion liquid to which this method is applied can also be used as a coating agent for covering feedthroughs that penetrate the battery or capacitor housings made of light metals such as aluminum, magnesium, titanium, silicon carbide, and their alloys with F polymers. As such feedthroughs, examples include feedthroughs in which the housing has an opening and a conductor that penetrates through a glass material for sealing the opening. The glass material may be a glass-ceramic material, and specifically, materials described in Japanese Patent Application Laid-Open No. 2018-502417 can be exemplified. As the conductor, materials suitable for electrode materials of batteries or capacitors can be exemplified. For example, for the cathode of a battery, copper and copper alloys can be exemplified. The conductor can be composed of different materials on the inner and outer sides of the outer shell.

[0054] The present invention also provides a dispersion liquid container in which the present dispersion liquid is contained in a containing container, wherein the liquid density of the present dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the present dispersion liquid calculated by the above formula (1), and the product of the gas phase volume ratio in the containing container and the gas-liquid interface area of the above containing container is in the range of 10,000 or more and 60,000 or less. By storing the dispersion liquid container in the range of higher than 0°C and 20°C or lower, the deterioration of the F polymer in the present dispersion liquid is less, and the coloring of the present dispersion liquid is suppressed for a long time. Regarding the F polymer, F particles, nonionic surfactant, the content ratio of F particles and nonionic surfactant to water, inorganic fillers, aromatic polymers, various additives that may be contained as components of the present dispersion liquid in the dispersion liquid container, and the containing container, they are the same as those described in the description of the present method.

[0055] The present method and the dispersion liquid container have been described above, but the present invention is not limited to the configurations of the above embodiments. For example, in the configurations of the above embodiments, other arbitrary configurations can be added to the present method and the dispersion liquid container, or they can be replaced with arbitrary configurations that exhibit the same functions. Examples

[0056] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. 1. Preparation of each component [F polymer particles] F particle 1: Particles (D50: 2.0 μm, density: 2.13 g / cm 6 ) of a tetrafluoroethylene-based polymer having 1000 carbon atoms per main chain and containing a carbonyl group (melting temperature: 300°C) composed of 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in sequence 3 ) F particle 2: Particles (D50: 2.0 μm, density: 2.13 g / cm 3 ) composed of a tetrafluoroethylene-based polymer having no oxygen-containing polar group (melting temperature: 300°C) composed of 97.5 mol% and 2.5 mol% of TFE units and PPVE units in sequence [Surfactant] Agent 1: A non-ionic silicone surfactant having a polysiloxane chain in the main chain and a polyoxyethylene group in the side chain (HLB value = 13) Agent 2: A non-ionic alkynediol surfactant (HLB value = 8, manufactured by Nissin Chemical Industry Co., Ltd., product name: SURFYNOL 440) Agent 3: A non-ionic alkynediol surfactant (HLB value = 4, manufactured by Nissin Chemical Industry Co., Ltd., product name: SURFYNOL 104A)

[0057] 2. Manufacturing examples of the dispersion <Dispersion 1> 95 parts by mass of F particles 1, 5 parts by mass of surfactant 1, and 100 parts by mass of water were put into a container and stirred with a homogenizing disperser at 1000 rpm to obtain Dispersion 1. <Dispersion 2> 95 parts by mass of F particles 2, 5 parts by mass of surfactant 1, and 100 parts by mass of water were put into a container and stirred with a homogenizing disperser at 1000 rpm to obtain Dispersion 2. <Dispersion 3> 95 parts by mass of F particles 1, 5 parts by mass of surfactant 2, and 100 parts by mass of water were put into a container and stirred with a homogenizing disperser at 1000 rpm to obtain Dispersion 3.

[0058] 3. Storage method of the dispersion container The following 2 types were used as storage containers. Container A: A commercially available bucket with an internal volume of 20 L and an inner diameter of 30 cm Container B: A commercially available bucket with an internal volume of 20 L and an inner diameter of 60 cm [Example 1] While stirring Dispersion 1 in a homogenizing disperser at 100 rpm, it was left standing for defoaming, and the stirring was stopped when the liquid density reached 1.336 g / cm 3 . The theoretical liquid density of the dispersion is 1.338 g / cm 3 , and the liquid density / theoretical liquid density is 99.8%. Among them, the liquid density was obtained by measuring the mass (W0) of the dry and cleaned Gerussac-type pycnometer (internal volume 50 mL, manufactured by Shibata Scientific Technology Ltd.) using a Gerussac-type pycnometer, and then filling the pycnometer with Dispersion 1 and measuring its mass (W1) according to the following formula. Liquid density (g / cm 3 ) = (W1 - W0) / 50 The obtained dispersion liquid 1 was injected into a container until the gas-phase volume ratio inside the container reached 20% by volume and then sealed, and it was stored in a refrigerator at 5°C. Here, the gas-liquid interface area inside container A was equal to the bottom area of container A, and the product of the gas-phase volume ratio inside container A and the gas-liquid interface area of the storage container was 14130.

[0059] [Example 2] to [Example 7] Except that the type of dispersion liquid for storage, the adjusted liquid density during storage, the type of storage container, and the storage temperature were changed to those shown in Table 1, each dispersion liquid was stored in the same manner as in Example 1.

[0060] 3. Evaluation of the dispersion liquid 3-1. Average dissolved oxygen content The average dissolved oxygen content of each dispersion liquid stored in each example was measured in ppm using an optical dissolved oxygen meter "DOP-01" (manufactured by Automatic system Research.Co.,Ltd). The measurement was carried out every 24 hours, and the average value during the 6-month storage period was calculated.

[0061] 3-2. Hue of the molded product (coating film) After 6 months of storage, each dispersion liquid was coated on the surface of polyimide using a rod coater to form a liquid film with the above-obtained dispersion liquid 1. Then, the polyimide film with the formed liquid film was passed through a drying oven at 120°C for minutes and heated to dry it to obtain a dried film. Then, in a nitrogen oven, the dried film was heated at 350°C for 5 minutes to form a laminate having a polymer layer (thickness 25 μm) containing F particles on the surface of the polyimide film. The polymer layer was separated from the obtained laminate, and the yellowness index (YI) was measured using a colorimeter SM-T (manufactured by Suga Test Instruments Co., Ltd.), and the evaluation was carried out according to the following criteria. <Evaluation criteria> ○: YI < 0.3 ×: 0.3 ≤ YI

[0062] 3-3. Surface appearance of the molded product (coating film) Each dispersion liquid after 6 months of storage was sprayed on a first-grade cold-rolled steel sheet (thickness 1 mm) specified in JIS K5600-1-4:2004, hot air dried at 120°C, and then fired at 350°C for 30 minutes to obtain a coating film. The obtained coating film was visually checked for foaming. <Evaluation criteria> ○: The coating film has no foaming ×: The coating film has foaming The above results are summarized in Table 1. From the evaluation results of Example 1 and Example 2, it can be confirmed that by the storage method of the present invention, a coating film with excellent surface appearance can be obtained in which not only the hue change (coloring) of the dispersion liquid is suppressed, but also foaming is suppressed.

[0063] Table 1

[0064] [Example 8] Dispersion liquid containers 2 and 3 were respectively prepared by changing agent 1 in dispersion liquid 1 of the dispersion liquid container (dispersion liquid container 1) of Example 1 to agent 2 and agent 3, and the dispersion liquid containers 1 to 3 were stored for 4 months. A quantitative liquid delivery pump was installed in each of the dispersion liquid containers after long-term storage, and a liquid transfer test of transferring the liquid to other containers was carried out. As a result, the dispersion liquid container 1 was able to perform the most uniform quantitative liquid transfer, the dispersion liquid container 2 tended to have liquid blockage in the liquid transfer pipeline, and the dispersion liquid container 3 tended to have an unstable composition of the dispersion liquid at the initial stage of liquid transfer. Industrial applicability

[0065] According to this method, even after long-term storage of an aqueous dispersion liquid containing an F polymer, the deterioration of the F polymer and the coloring of the dispersion liquid are suppressed. A molded article such as a coating film in which the physical properties of the F polymer are highly exhibited, having less coloring, excellent adhesiveness and surface appearance, can be formed from the dispersion liquid to which this method is applied. Specifically, it is a laminate having a polymer layer formed from the dispersion liquid.

[0066] In addition, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2022-200242 filed on December 15, 2022 are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims

1. A method for storing a dispersion liquid container, wherein, A dispersion liquid containing particles of a tetrafluoroethylene-based polymer, a nonionic surfactant, and water is accommodated in a storage container in such a form that the liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by the following formula (1), and the product of the gas-phase volume ratio in the storage container and the gas-liquid interface area of the storage container is maintained in the range of 10,000 or more and 60,000 or less, and the temperature is maintained in the range greater than 0 °C and 20 °C or less for storage. The theoretical liquid density of the dispersion liquid = (density of the dispersed substance × volume ratio of the dispersed substance) / (density of the dispersed substance × volume ratio of the dispersed substance + density of the dispersion medium × volume ratio of the dispersion medium) …… (1).

2. The storage method according to claim 1, wherein The tetrafluoroethylene-based polymer is thermally fusible and has an oxygen-containing polar group.

3. The storage method according to claim 1, wherein, The average particle diameter of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm.

4. The storage method according to claim 1, wherein, The content of the particles of the tetrafluoroethylene-based polymer in the dispersion liquid is 25% by mass or more.

5. The storage method according to claim 1, wherein The powder of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are mixed to prepare the dispersion liquid.

6. The storage method according to claim 1, wherein, In the dispersion liquid, with respect to the total of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water, the contents of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are 35 to 70% by mass, 1 to 15% by mass, and 15 to 64% by mass, respectively.

7. The storage method according to claim 1, wherein, The mass ratio of the nonionic surfactant in the dispersion liquid with respect to the particles of the tetrafluoroethylene-based polymer is 0.01 to 0.

15.

8. The storage method according to claim 1, wherein, The nonionic surfactant is a silicone-based surfactant or an acetylene-based surfactant.

9. The storage method according to claim 1, wherein, The HLB value of the nonionic surfactant calculated by the Griffin formula is 3 to 16.

10. The storage method according to claim 1, wherein, The dissolved oxygen amount of the dispersion liquid is in the range of 8 to 12 ppm.

11. A dispersion liquid storage body, which is a dispersion liquid storage body formed by accommodating a dispersion liquid containing particles of a tetrafluoroethylene-based polymer, a nonionic surfactant, and water in a storage container. The liquid density of the dispersion liquid is in the range of 95.0% or more and less than 99.9% with respect to the theoretical liquid density of the dispersion liquid calculated by the following formula (1), and the product of the gas-phase volume ratio in the storage container and the gas-liquid interface area of the storage container is in the range of 10,000 or more and 60,000 or less. The theoretical liquid density of the dispersion liquid = (density of the dispersed substance × volume ratio of the dispersed substance) / (density of the dispersed substance × volume ratio of the dispersed substance + density of the dispersion medium × volume ratio of the dispersion medium) …… (1).

12. The dispersion liquid container according to claim 11, wherein, The tetrafluoroethylene-based polymer is thermally fusible and has an oxygen-containing polar group.

13. The dispersion liquid container according to claim 11, wherein, The average particle diameter of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm.

14. The dispersion liquid container according to claim 11, wherein, In the dispersion liquid, with respect to the total of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water, the contents of the particles of the tetrafluoroethylene-based polymer, the nonionic surfactant, and the water are 35 to 70% by mass, 1 to 15% by mass, and 15 to 64% by mass, respectively.

15. The dispersion liquid container according to claim 11, wherein, The nonionic surfactant is a silicone-based surfactant or an acetylene-based surfactant.

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