Liquid composition

Abstract

To provide a liquid composition which has highly excellent properties of a tetrafluoroethylene-based polymer, such as mechanical properties, heat resistance, and electrical properties (a low coefficient of linear expansion, a low dielectric constant, and a low dielectric loss tangent), and is easy to form a coating layer, which is homogeneous and excellent in adhesion to an elastic base material, and is further excellent in fluorine plasma resistance, on the surface of an elastic base material of a fluoroelastomer having a curved surface structure.SOLUTION: A liquid composition having a surface tension of 50 dyn / cm or less comprises particles of a thermofusible tetrafluoroethylene-based polymer having a carbonyl group-containing group, the composition being used for coating the surface of an elastic base material of a fluoroelastomer having a curved surface structure.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a liquid composition containing particles of a specific tetrafluoroethylene-based polymer. Specifically, the present invention relates to a liquid composition containing particles of a specific tetrafluoroethylene-based polymer, which is used for coating the surface of an elastic base material of a fluoroelastomer having a curved surface structure.

Background Art

[0002] Fluoroelastomers exhibit chemical resistance, solvent resistance, heat resistance, etc., and are used as sealing materials and the like used in environments such as plasma atmospheres and chemical atmospheres in the aerospace field, semiconductor manufacturing equipment field, chemical plant field, etc. In recent years, there has been a tendency to use high-concentration and highly active gases and chemical liquids, etc., and a sealing material made of a conventional fluoroelastomer may require frequent replacement. [[ID=X]] Among fluoroelastomers, perfluoroelastomers are particularly excellent in plasma resistance and chemical resistance, and are thus used as the sealing material, but there is also a problem that they are very expensive. In order to obtain a material excellent in plasma resistance and chemical resistance, a composition of a fluoroethylene-based polymer and other components has been proposed. For example, Patent Document 1 proposes a composition containing a fluoroethylene-based polymer and a polymer of a predetermined silsesquioxane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On one hand, a coating film (coating layer) may be provided on the surface of an elastic base material such as a gasket, a bearing seal, an oil seal, an O-ring, etc. for the purposes of preventing adhesion, preventing blocking, improving wear resistance, etc. However, when attempting to form a coating layer on the surface of the above-described elastic base material using a liquid composition containing a fluoroethylene-based polymer having the above characteristics, since the elastic base material has a curved surface structure, the formed coating layer tends to be non-uniform, unevenness is likely to occur in thickness and surface characteristics, and the adhesion between the obtained coating layer and the elastic base material also tends to decrease.

[0005] The inventors of the present invention have found that a liquid composition containing particles of a specific tetrafluoroethylene-based polymer and having a surface tension within a specific range is excellent in dispersibility, and when used to coat the surface of an elastic base material of a fluoroelastomer having a curved surface structure, the formed coating layer is excellent in characteristics based on the tetrafluoroethylene-based polymer such as mechanical properties, heat resistance, and electrical properties, and also excellent in adhesion to the elastic base material and further excellent in fluorine plasma resistance, and thus have arrived at the present invention. An object of the present invention is to provide such a composition.

Means for Solving the Problems

[0006] The present invention has the following aspects. [1] A liquid composition having a surface tension of 50 dyn / cm or less, containing particles of a heat-meltable tetrafluoroethylene-based polymer having a carbonyl group-containing group, which is used for coating the surface of an elastic base material of a fluoroelastomer having a curved surface structure. [2] The liquid composition according to [1], wherein the average particle diameter of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm. [3] The liquid composition according to [1] or [2], wherein the content of the particles of the tetrafluoroethylene-based polymer is 30% by mass or more. [4] The liquid composition according to any one of [1] to [3], wherein the fluorine content of the tetrafluoroethylene-based polymer is 70% by mass or more and 78% by mass or less. [5] A liquid composition according to any one of [1] to [4], which is an aqueous system. [6] A liquid composition according to any one of [1] to [5], further containing a nonionic surfactant. [7] A liquid composition according to any one of [1] to [6], further containing particles of a non-thermally fusible tetrafluoroethylene-based polymer. [8] A liquid composition according to any one of [1] to [7], further containing particles of a fluoroelastomer. [9] A liquid composition according to any one of [1] to [8], having a viscosity at 25 °C of 100,000 mPa or less.

[10] A liquid composition according to any one of [1] to [9], wherein the elastic base material having the curved surface structure is a sealing material.

[11] A liquid composition according to any one of [1] to

[10] , wherein the water contact angle of the elastic base material is more than 50°.

[12] A liquid composition according to any one of [1] to

[11] , wherein the critical wetting surface tension of the elastic base material is 40 mN / m or less.

[13] A liquid composition according to any one of [1] to

[12] , wherein the elastic base material is an elastic base material of a perfluoroelastomer.

[14] A liquid composition according to any one of [1] to

[13] , wherein the means of coating is spray spraying or dipping. [Advantages of the Invention]

[0007] According to the present invention, there can be provided a liquid composition that highly exhibits physical properties of a tetrafluoroethylene-based polymer such as mechanical properties, heat resistance, and electrical properties (low linear expansion coefficient, low dielectric constant, low dielectric tangent), is homogeneous and has excellent adhesion to the elastic base material, and further easily forms a coating layer excellent in fluorine plasma resistance on the surface of an elastic base material of a fluoroelastomer having a curved surface structure. [Embodiments for Carrying Out the Invention]

[0008] The following terms have the following meanings. In a polymer, the "unit" means an atomic group based on the monomer formed by the polymerization of the monomer. The unit may 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". The "melting temperature" is the temperature corresponding to the maximum value of the melting peak of the polymer measured by the differential scanning calorimetry (DSC) method. The "glass transition point (Tg)" is a value measured by analyzing the polymer by the dynamic viscoelasticity measurement (DMA) method. The "average particle diameter (D50)" is the volume-based cumulative 50% diameter of the particles determined by the laser diffraction / scattering method. That is, the particle size distribution is measured by the laser diffraction / scattering method, the cumulative curve is obtained with the total volume of the particle population as 100%, and it is the particle diameter at the point where the cumulative volume becomes 50% on the cumulative curve. The D50 of the particles is determined by dispersing the particles in water and analyzing them by the laser diffraction / scattering method using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., LA-920 measuring instrument). The specific surface area of the particles is a value calculated by measuring the particles by the gas adsorption (constant volume method) BET multipoint method, and is determined using NOVA4200e (manufactured by Quantachrome Instruments). The "viscosity" is determined by measuring the composition at 25 °C under the condition of a rotation speed of 30 rpm using a B-type viscometer. The measurement is repeated 3 times, and the average value of the 3 measurement values is taken. The "thixotropy ratio" is a value calculated by dividing the viscosity η1 measured under the condition of a rotation speed of 30 rpm of the composition by the viscosity η2 measured under the condition of 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 "surface tension" of the solvent or liquid composition is a value measured by the Wilhelmy method at 25 °C using a surface tensiometer.

[0009] The present invention relates to a liquid composition (hereinafter also referred to as "this composition") having a surface tension of 50 dyn / cm or less, which contains particles of a heat-meltable tetrafluoroethylene-based polymer having a carbonyl-containing group (hereinafter also referred to as "F polymer") (hereinafter also referred to as "F particles") and is used for coating the surface of an elastic base material of a fluoroelastomer having a curved surface structure (hereinafter also referred to as "this elastic base material"). In other words, this composition is also a coating agent for coating the surface of this elastic base material.

[0010] This composition has excellent dispersibility, highly possesses physical properties of tetrafluoroethylene-based polymers such as mechanical properties, heat resistance, and electrical properties (low linear expansion coefficient, low dielectric constant, low dielectric tangent), is homogeneous and has excellent adhesion to the elastic base material, and can easily form a coating layer with excellent fluorine plasma resistance on the surface of this elastic base material. The reason is not necessarily clear, but it is considered as follows.

[0011] When forming a coating layer on the surface of a base material by a coating method, if the base material has a curved surface structure, the formed coating layer is likely to be non-uniform, and unevenness is likely to occur in thickness and surface properties. In particular, when a liquid composition containing particles of a tetrafluoroethylene-based polymer is coated on the surface and dried to obtain a coating layer, and then melt-fired to form a coating layer containing a tetrafluoroethylene-based polymer, such a tendency is likely to become prominent, and the adhesion between the obtained coating layer and the base material is also likely to decrease. Further, if the base material having a curved surface structure is composed of a hydrophobic polymer such as a fluoroelastomer, such a tendency is likely to become more prominent. In the present invention, since the surface tension of the present composition is 50 dyn / cm or less, even when the substrate is a fluoroelastomer, the affinity with its surface is improved, the contact surface increases, and the dispersibility of F particles in the present composition is also improved. Therefore, it is presumed that it becomes easier to uniformly coat the surface of the elastic substrate of the fluoroelastomer having a curved surface structure. Further, in the coating layer formed on the surface of the present elastic substrate by the present composition, since the F particles are likely to be packed uniformly and densely, it is presumed that unevenness is less likely to occur in the thickness and surface characteristics of the coating layer formed through melting and firing. As a result, physical properties based on the F polymer such as mechanical properties, heat resistance, and electrical properties can be imparted to the present elastic substrate, and it is considered that the fluorine plasma resistance is also excellent.

[0012] The F polymer in the present invention is a polymer containing a unit based on tetrafluoroethylene (hereinafter also referred to as "TFE") (hereinafter also referred to as "TFE unit"). The F polymer is thermally meltable. Here, a thermally meltable polymer means a polymer in which there exists a temperature at which the melt flow rate is 1 to 1000 g / 10 min under the condition of a load of 49 N. The melting temperature of the F polymer is preferably 200°C or higher, more preferably 260°C or higher. The melting temperature of the F polymer is preferably 325°C or lower, more preferably 320°C or lower. The melting temperature of the F polymer is preferably 200 to 320°C. In this case, the coating layer formed on the surface of the present elastic substrate is likely to be excellent in heat resistance.

[0013] The glass transition point of the F polymer is preferably 50°C or higher, more preferably 75°C or higher. The glass transition point 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 more and 78% by mass or less, more preferably 72% by mass or more and 76% by mass or less. The surface tension of the F polymer is preferably 16 to 26 dyn / cm. The surface tension of the F polymer can be measured by placing a droplet of the wetting tension test mixture (manufactured by Wako Pure Chemical Industries, Ltd.) defined in JIS K 6768 on a flat plate made of the F polymer.

[0014] The F polymer is preferably 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)-based units (PAVE units) (PFA), or a polymer containing TFE units and hexafluoropropylene (hereinafter also referred to as "HFP")-based units (HFP units) (FEP), more preferably PFA and FEP, and even more preferably PFA. These polymers may further contain units based on other comonomers. PAVE is preferably CF2=CFOCF3 (hereinafter also referred to as "PMVE"), CF2=CFOCF2CF3 (hereinafter also referred to as "PEVE"), or CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and more preferably PPVE.

[0015] The F polymer has a carbonyl group-containing group. In this case, the coating layer formed on the surface of the elastic base material is likely to have excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric tangent). Examples of the carbonyl group-containing group include a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH2), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.), a formyl group, a halogenoformyl group, a urethane group (-NHC(O)O-), a carbamoyl group (-C(O)-NH2), a ureido group (-NH-C(O)-NH2), an oxamoyl group (-NH-C(O)-C(O)-NH2), and a carbonate group (-OC(O)O-). An acid anhydride residue is more preferable. The number of carbonyl group-containing groups in the F polymer is preferably 10 to 5000, more preferably 100 to 3000, per 1 × 10 6 carbon atoms constituting the polymer main chain. The number of carbonyl group-containing groups in the F polymer can be quantified by the composition of the polymer or the method described in International Publication No. 2020 / 145133. Incidentally, the F polymer may have an oxygen-containing polar group other than the carbonyl group-containing group, for example, a hydroxyl group-containing group. The hydroxyl group-containing group preferably contains an alcoholic hydroxyl group, and -CF2CH2OH and -C(CF3)2OH are more preferable.

[0016] The carbonyl group-containing group may be contained in the unit based on the monomer in the F polymer, or may be contained in the terminal group of the main chain of the F polymer, and the former is preferable. Examples of the latter aspect include an F polymer having a carbonyl group-containing group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer obtained by subjecting the F polymer to plasma treatment or ionization radiation treatment.

[0017] The F polymer contains a TFE unit and a PAVE unit in this order in an amount of more than 97.5 mol% and less than 99.5 mol%, and 0.5 mol% or more and less than 2.5 mol%, and has a carbonyl group-containing group per 1×10 6 A polymer having 100 or more per carbon atom constituting the polymer main chain is preferable. It contains a TFE unit, a PAVE unit, and a unit based on a monomer having a carbonyl group-containing group, and in terms of all units, these units are in this order, more than 97.5 mol% and less than 99.5 mol%, 0.5 mol% or more and less than 2.2 mol%, and 0.01 to 0.3 mol%. A more preferable polymer is one containing such amounts. Specific examples of such F polymers include the polymers described in International Publication No. 2018 / 16644. The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH. By using such an F polymer, spherulites having a relatively small radius are likely to be formed, so the surface property of the coating layer formed on the surface of the base elastic material is likely to be high.

[0018] The F particles contained in the present composition are particles containing an F polymer, and preferably consist of the F polymer. The D50 of the F particles is preferably 1 μm or more and less than 10 μm. The F particles may be solid particles or non-hollow particles. The F particles may be secondary particles formed from fine particles on the order of nm. 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. Also, the D90 of the F particles is preferably 8 μm or less, more preferably 6 μm or less. When the D50 and D90 of the F particles are within the above ranges, the composition is likely to be excellent in dispersion stability and handleability. One type of F particle may be used, or two or more types may be used.

[0019] The specific surface area of the F particles is preferably 1 to 25 m 2 / g, more preferably 6 to 15 m 2 / g. When the specific surface area of the F particles is within the above range, the surface of the F particles is likely to be wetted, the aggregates of the F particles are likely to be crushed, and the composition is likely to be excellent in dispersion stability and handleability. In addition, the coating layer formed on the surface of the elastic base material is likely to be excellent in adhesion to the base material in addition to physical properties based on the F polymer such as mechanical properties, heat resistance, and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric tangent).

[0020] The content of the F particles in the composition is preferably 25% by mass or more, more preferably 30% by mass or more. The content of the F particles is preferably 55% by mass or less, more preferably 50% by mass or less.

[0021] The composition is preferably an aqueous liquid composition using water as a liquid dispersion medium. The water content in the composition is preferably 25% by mass or more, more preferably 40% by mass or more. The water content is preferably less than 70% by mass, more preferably 65% by mass or less. Also, the water content in the composition is preferably 60 to 180% by mass with respect to the content of the F particles.

[0022] The composition may further contain a water-soluble solvent in addition to water as a liquid dispersion medium, as long as the effects of the present invention are not impaired. The water-soluble solvent is a compound that is liquid at 25 °C under atmospheric pressure, and a compound having a boiling point of 50 to 240 °C is preferred. Examples include amides such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-diethylformamide, hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolidinone; ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, cycloheptanone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, γ-valerolactone; and monoalcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, 1-methoxy-2-propanol, 2-propoxy-ethanol, 1-propoxy-2-propanol, 2-ethoxyethanol. One type of water-soluble solvent may be used, or two or more types may be used. The surface tension of the water-soluble solvent is preferably 20 to 30 dyn / cm. When the composition further contains a water-soluble solvent, the amount is preferably 0.1 to 5% by mass based on the total amount of the composition. Also, the content of the water-soluble solvent in the composition is preferably 1 to 10% by mass based on the content of the F particles.

[0023] The composition may further contain particles of a non-thermally fusible tetrafluoroethylene-based polymer. As the particles of the non-thermally fusible tetrafluoroethylene-based polymer, particles of polytetrafluoroethylene (PTFE) are preferred. In this case, when forming the coating layer from the composition, PTFE is moderately fibrillated, making it easy to form a high-strength coating layer with excellent physical properties based on PTFE, and its slidability is likely to be improved. The D50 of the PTFE particles is preferably 0.1 to 1 μm. When the composition further contains particles of a non-thermally fusible tetrafluoroethylene-based polymer, the amount is preferably 10 to 50% by mass based on the total amount of the composition. Also, the content of the particles of the non-thermally fusible tetrafluoroethylene-based polymer relative to the content of the F particles in the composition is preferably less than 1 as a mass ratio.

[0024] The composition may further contain particles of a fluoroelastomer. In this case, the adhesion between the coating layer formed from the composition and the elastic base material layer is likely to be improved, and the physical properties based on the fluoroelastomer are likely to be exhibited. The D50 of the fluoroelastomer particles is preferably 0.1 to 1 μm. The fluoroelastomer is a polymer containing units based on fluoroolefins, and is preferably a polymer containing units based on at least one fluoroolefin selected from the group consisting of tetrafluoroethylene (TFE), hexafluoropropylene, vinylidene fluoride (hereinafter also referred to as "VdF"), vinyl fluoride, and chlorotrifluoroethylene. Also, the fluoroelastomer is an elastic polymer without a melting point, having a storage elastic modulus of 80 or more at 100 °C and 50 cpm as measured according to ASTM D6204. One type of fluoroelastomer particles may be used, or two or more types may be used in combination.

[0025] When the composition further contains fluororubber particles, the amount thereof is preferably 10 to 50% by mass based on the total amount of the composition. Further, the content of the fluororubber particles with respect to the content of the F particles in the composition is preferably less than 1 as a mass ratio.

[0026] From the viewpoint of improving the dispersion stability of the F particles and easily controlling the surface tension of the composition within the range defined in the present invention, the composition preferably further contains a nonionic surfactant. Examples of the nonionic surfactant include glycol-based surfactants, acetylene-based surfactants, silicone-based surfactants, and fluorine-based surfactants. Among them, a nonionic surfactant having a hydroxyl group in the hydrophilic moiety is preferable, and an organopolysiloxane having a hydroxyl group or a polyoxyalkylene group is more preferable. When the composition contains the above-mentioned nonionic surfactant, the surface tension of the composition can be easily adjusted, the above-mentioned action mechanism is more likely to be exhibited, and the dispersion stability and handleability of the F particles are excellent. In addition, the rheological properties of the composition are improved, and the handleability such as film-forming property is easily improved. As the organopolysiloxane, a polyoxyalkylene-modified dimethylsiloxane having a polyoxyalkylene structure as the hydrophilic moiety and a polydimethylsiloxane structure as the hydrophobic moiety is more preferable. The polyoxyalkylene-modified dimethylsiloxane may have polydimethylsiloxane units (-(CH3)2SiO 2 / 2 -) in the main chain, may have polydimethylsiloxane units in the side chain, or may have polydimethylsiloxane units in both the main chain and the side chain.

[0027] Specific examples of nonionic surfactants include the "Phargent" series (manufactured by Neos), the "Surflon" series (manufactured by AGC Seimi Chemical Co., Ltd.), the "MegaFac" series (manufactured by DIC Corporation), the "Unidine" series (manufactured by Daikin Industries, Ltd.), "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", "BYK-3456" (manufactured by BYK-Chemie Japan), "KF-6011", "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.), the "Tergitol" series (manufactured by The Dow Chemical Company, such as "Tergitol TMN-100X", etc.). One nonionic surfactant may be used, or two or more nonionic surfactants may be used. When the composition contains a nonionic surfactant, the content of the nonionic surfactant in the composition is preferably 1 to 15% by mass. With a content within such a range, it becomes easy to adjust the surface tension of the composition to the range defined in the present invention.

[0028] The composition may further contain one or more water-soluble polymers such as vinyl alcohol-based polymers, acrylic-based polymers, and polyvinylpyrrolidone from the viewpoint of controlling its rheological properties, as long as the effects of the present invention are not impaired. In the present specification, the "water-soluble polymer" means a polymer having a solubility in water of 20 g / L or more.

[0029] The composition may contain, as long as the effects of the present invention are not impaired, other resins different from F polymers, non-thermally fusible tetrafluoroethylene-based polymers, and fluoroelastomers. Such other resins may be contained in the composition as non-hollow particles, or may be dissolved or dispersed in a liquid dispersion medium such as water constituting the composition. Examples of other resins include polyester resins such as liquid crystalline aromatic polyesters, polyimide resins, polyamideimide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. When the composition further contains other resins, the content of the other resins relative to the F particles is preferably 1 to 25% by mass.

[0030] The composition may further contain additives such as inorganic particles, thixotropic agents, viscosity modifiers, defoamers, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, brighteners, colorants, conductive agents, mold release agents, flame retardants, etc., as long as the effects of the present invention are not impaired.

[0031] The composition can be obtained by mixing F particles, water, and, if necessary, the particles of the non-thermally meltable tetrafluoroethylene-based polymer, fluoroelastomer particles, water-soluble solvent, nonionic surfactant, other resins, additives, etc. described above. The composition may be obtained by mixing the F particles and water all at once, or by mixing them in multiple divided portions. Also, there is no particular limitation on the mixing order when further mixing the particles of the non-thermally meltable tetrafluoroethylene-based polymer, fluoroelastomer particles, water-soluble solvent, nonionic surfactant, other resins, additives, etc. as necessary. They may be mixed with the F particles in advance, added to the water in advance and then mixed with the F particles, or mixed during the mixing of the F particles and water.

[0032] The surface tension of the composition is 50 dyn / cm or less, and more preferably 40 dyn / cm or less. The surface tension of the composition is preferably 20 dyn / cm or more. When the surface tension of the composition is within the above range, the above-described mechanism of action is exhibited, and in the coating layer formed from the composition, the physical properties based on the F polymer are likely to be highly exhibited, and the fluorine plasma resistance is also likely to be excellent.

[0033] The viscosity of the composition at 25°C is preferably 10 mPa·s or more, and more preferably 100 mPa·s or more. The viscosity of the composition at 25°C is preferably 100000 mPa or less, preferably 10000 mPa·s or less, and more preferably 3000 mPa·s or less. In this case, the composition has excellent coatability and is likely to form a uniform coating layer. Also, the composition within such a viscosity range is likely to highly exhibit the physical properties of the F polymer in the coating layer formed therefrom. The thixotropy ratio of this composition is preferably 1.0 to 3.0. In this case, this composition is excellent in coatability and homogeneity, and is likely to form a denser coating layer.

[0034] This composition is preferably aqueous as described above. From the viewpoint of improving long-term storage stability, the pH of the aqueous composition is more preferably 8 to 10. The pH of such a composition can be adjusted with a pH adjuster (amine, ammonia, citric acid, etc.) or a pH buffer (tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium hydrogen carbonate, ammonium carbonate, ammonium acetate, etc.).

[0035] The thickness of the coating layer obtained from this composition is preferably 1 μm or more and 200 μm or less.

[0036] By coating this composition on the surface of the elastic substrate to form a coating layer containing F particles and then performing melting and firing, a laminate having a substrate layer composed of the elastic substrate and a coating layer formed by this composition can be obtained. The coating layer is preferably formed by coating this composition on the surface of the elastic substrate and heating to remove the liquid dispersion medium. Examples of the means for coating this composition include spray spraying, roll coater, flow coater, die coater, spin coating, droplet ejection, dipping (immersion), etc. Among them, the means for coating this composition on the elastic substrate is preferably spray spraying or dipping from the viewpoints of production efficiency and easy formation of a uniform coating film. The heating for removing the liquid dispersion medium is preferably carried out at 100 to 200 °C for 0.1 to 30 minutes. In this heating, the coating layer is formed by the packing of F particles. When heating, air may be blown to promote the removal of the liquid dispersion medium by air drying.

[0037] It is preferable to further heat the present elastic base material having a coating layer in a temperature range equal to or higher than the melting temperature of the F polymer, for example, 340 to 400 °C, to melt and sinter the F particles to form a coating layer containing a melt-sintered body of the F polymer. The heating time is preferably 0.1 to 30 minutes. Examples of the heating device for removing the liquid dispersion medium and melting and sintering the F particles include an oven and a ventilation drying furnace. The heat source in the device may be a contact heat source (such as hot air or a hot plate) or a non-contact heat source (such as infrared rays). The heating may be performed under normal pressure or under reduced pressure. The atmosphere during heating may be any of an air atmosphere and an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere.

[0038] The coating and heating steps of the present composition may be performed once or may be repeated two or more times. For example, the present composition may be coated on the surface of the present elastic base material and heated to form a coating layer, and further, the present composition may be coated on the surface of the coating layer and heated to form a second coating layer. Also, at the stage of forming a coating layer in which the present composition is coated on the surface of the present elastic base material and heated to remove the liquid dispersion medium, the present composition may be further coated on the surface of this coating layer and heated to form a coating layer.

[0039] The water contact angle of the present elastic base material is preferably more than 50°, more preferably 80° or more. The water contact angle of the present elastic base material is preferably 120° or less. The critical wetting surface tension of the present elastic base material is preferably 40 mN / m or less, more preferably 30 mN / m or less. The critical wetting surface tension of the present elastic base material is preferably 20 mN / m. When the present elastic base material has a water contact angle and a critical wetting surface tension within the above ranges, when the present composition is used to coat the surface of the present elastic base material, the affinity between the surface of the present elastic base material and the present composition is improved, the contact surface increases, the above-described action mechanism is likely to be exhibited, and unevenness is less likely to occur in the thickness and surface characteristics of the formed coating layer.

[0040] This elastic base material is composed of a fluoroelastomer. Examples of the fluoroelastomer include the same fluoroelastomer as the particles of the fluoroelastomer that may be contained in this composition. Among them, a perfluoroelastomer as the elastic base material is more preferable. Note that the perfluoroelastomer means an elastomer having a fluorine content of 76 to 78% by mass. Examples of the fluoroelastomer include fluoroelastomer (FKM) which is a polymer containing the above-mentioned HFP unit and VdF unit, and fluoroelastomer (FFKM) which is a polymer containing TFE unit and PMVE unit or PEVE unit. In addition, these polymers may contain units based on fluoromonomers having crosslinkable groups, and the fluoroelastomer may be a crosslinked polymer.

[0041] This elastic base material is preferably a sealing material. Examples of the sealing material include bearing seals, oil seals, lip seals, O-rings, gaskets, and packings. Among them, an O-ring is preferable. In other words, this composition is used to form a coating layer on the surface of this elastic base material which is a sealing material such as a rubber-coated metal gasket, a bearing seal, an oil seal, an O-ring, etc. When the elastic base material whose surface is coated by this composition is an O-ring, such a coated elastic base material can also be regarded as an annular laminate having a base material layer made of the elastic base material as the inner layer (inner core) and a coating layer containing F-polymer at least on the outer periphery. In addition, this composition can also be used as a coating material and a lining material for the surface of square rings, metal seals, rubber-coated metal gaskets, etc., diaphragms, tubes, hoses, various rubber rolls, belts, etc. used in semiconductor manufacturing equipment.

[0042] The elastic substrate whose surface is coated with the present composition highly has physical properties based on the F polymer, is excellent in mechanical properties and heat resistance, has a low coefficient of linear expansion, dielectric constant and dielectric loss tangent, and is particularly excellent in fluorine plasma resistance (fluorine radical resistance), so it can be suitably used as a sealing material for semiconductor manufacturing equipment. The semiconductor manufacturing equipment is not limited to the semiconductor manufacturing equipment for semiconductor manufacturing where high-density plasma irradiation is performed, but includes all manufacturing equipment used in the semiconductor field that requires a high degree of cleanliness, such as equipment for manufacturing liquid crystal panels and plasma panels. For example, etching equipment such as dry etching, plasma etching, reactive ion etching, reactive ion beam etching, sputter etching, ion beam etching, wet etching, ashing; cleaning equipment such as dry etching cleaning, UV / O3 cleaning, ion beam cleaning, laser beam cleaning, plasma cleaning, gas etching cleaning, extraction cleaning, Soxhlet extraction cleaning, high-temperature high-pressure extraction cleaning, microwave extraction cleaning, supercritical extraction cleaning equipment; exposure equipment such as steppers, coater developers; polishing equipment such as CMP (Chemical Mechanical Polishing); film forming equipment such as CVD, sputtering; diffusion and ion implantation equipment such as oxidation diffusion, ion implantation.

[0043] As described above, the present composition and the usage mode of the present composition have been described, but the present invention is not limited to the configuration of the above-described embodiments. For example, the present composition may additionally have any other configuration in the configuration of the above-described embodiment, or may be replaced with any configuration that produces the same effect. The usage mode of the present composition may additionally have any other mode in the configuration of the above-described embodiment, or may be replaced with any mode that produces the same effect.

Examples

[0044] 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] Particle F1: A tetrafluoroethylene-based polymer (melting point: 300 °C) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in this order, and having 1000 carbonyl group-containing groups per 1 × 10 6 carbon atoms. The particles have a D50 of 2.0 μm and a specific surface area of 7 m 2 / g) [Surfactant] Surfactant 1: A nonionic silicone surfactant having a polysiloxane chain in the main chain and a polyethylene oxide group in the side chain [O-ring] O-ring 1: An O-ring (outer diameter 32 mm, inner diameter 25 mm, thickness 3.5 mm) formed from a composition prepared by blending carbon black (Thermax N-990; trade name, manufactured by Cancarb), calcium hydroxide, and magnesium oxide into a perfluoroelastomer which is a polymer containing TFE units and PMVE units (FFKM).

[0045] 2. Production Examples of Liquid Compositions [Example 1] Into a pot, Particle F1, Surfactant 1, and water were charged, and zirconia balls were added. Then, the pot was rolled at 150 rpm for 1 hour to obtain Liquid Composition 1 containing 20% by mass of Particle F1 (surface tension: 50 dyn / cm or less). [Example 2] Liquid Composition 2 containing 20% by mass of Particle F1 (surface tension: more than 50 dyn / cm) was obtained in the same manner as in Example 1 except that the amount of Surfactant 1 used was changed.

[0046] 3. Production Examples and Evaluations of Circular Laminates 3-1. Production of Circular Laminates O-ring 1 was immersed 5 times (dipped) in Liquid Composition 1 obtained in Example 1 and dried at 120 °C for 5 minutes to form a dry film containing Particle F1 on the surface of each O-ring. Furthermore, each O-ring having this dry film was passed through a far-infrared furnace at 350 °C for 5 minutes to melt and sinter Particle F1, and Circular Laminate 1 having a coating layer containing the melt-sintered product of Particle F1 on the surface of each O-ring was obtained. In addition, the same operations were performed except that the liquid composition 2 obtained in Example 2 was used instead of the liquid composition 1, and the annular laminate 2 was obtained.

[0047] 3-2. Fluorine plasma resistance (fluorine radical resistance) at high temperature Each annular laminate was subjected to a fluorine radical exposure test in which a remote plasma source was used as a plasma source and exposed to fluorine radicals generated by remote plasma of NF3 at 200 °C for 3 hours. The appearance of each annular laminate after the test was visually observed to evaluate the fluorine radical resistance at 200 °C. As a result, no melting of the surface was confirmed in the annular laminate 1, and the fluorine radical resistance was superior to that of the annular laminate 2.

[0048] 3-3. Sealing property As a result of measuring the leakage amount of helium gas when helium gas was supplied to the piping for compressed gas to which each annular laminate was fastened to the flange portion, the gas leakage amount from the flange portion to which the annular laminate 1 was fastened was 1% or less of that of the annular laminate 2.

Industrial applicability

[0049] The elastic base material of the fluoroelastomer having a curved surface structure and having a coating layer formed from this composition is imparted with physical properties based on a tetrafluoroethylene-based polymer such as mechanical properties, heat resistance, and electrical properties, and is particularly excellent in fluorine plasma resistance. Therefore, it can be suitably used as a sealing material for semiconductor manufacturing equipment.

Claims

1. A liquid composition having a surface tension of 50 dyn / cm or less, containing particles of a thermoplastic tetrafluoroethylene-based polymer having a carbonyl group-containing group, which is used for coating the surface of an elastic substrate of a fluoroelastomer having a curved surface structure.

2. The liquid composition 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.

3. The liquid composition according to Claim 1, wherein the content of the particles of the tetrafluoroethylene-based polymer is 30% by mass or more.

4. The liquid composition according to Claim 1, wherein the fluorine content of the tetrafluoroethylene-based polymer is 70% by mass or more and 78% by mass or less.

5. The liquid composition according to Claim 1, which is aqueous.

6. The liquid composition according to Claim 1, further containing a nonionic surfactant.

7. The liquid composition according to Claim 1, further containing particles of a non-thermoplastic tetrafluoroethylene-based polymer.

8. The liquid composition according to Claim 1, further containing particles of a fluoroelastomer.

9. The liquid composition according to Claim 1, having a viscosity at 25°C of 100,000 mPa or less.

10. The liquid composition according to Claim 1, wherein the elastic substrate having the curved surface structure is a sealing material.

11. The liquid composition according to Claim 1, wherein the water contact angle of the elastic substrate is more than 50°.

12. The liquid composition according to Claim 1, wherein the critical wetting surface tension of the elastic substrate is 40 mN / m or less.

13. The liquid composition according to Claim 1, wherein the elastic substrate is an elastic substrate of a perfluoroelastomer.

14. The liquid composition according to Claim 1, wherein the coating means is spray coating or dipping.