Fluorine-containing coating composition and coated article

Abstract

To provide a fluorine-containing coating composition having superior resistance against repeated humid heat and cold cycles.SOLUTION: A fluorine-containing copolymer is mixed with an isocyanate curing agent containing a polyoxyalkylene group to provide a fluorine-containing coating composition that forms a coating film having superior resistance against repeated humid heat and cold cycles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing coating composition and a coated article having a coating film formed using the fluorine-containing coating composition. [Background technology]

[0002] Paints containing fluororesin are widely used in fields that require properties such as mechanical strength, weather resistance, waterproofing / moisture resistance, and electrical insulation. In many cases, such paints contain a curing agent in addition to the fluorine-containing copolymer. Patent Document 1 describes that by using a mixed composition of a flexible synthetic resin, a hard solvent-soluble fluororesin, and a curing agent as a coating material, it is possible to obtain coated articles that have excellent processability, such as weather resistance, scratch resistance, and bendability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-112752 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the coating film using the paint of the invention of Patent Document 1 has excellent processability, it has the problem of insufficient resistance to repeated exposure to heat and humidity, which is expected for use in harsh environments. Therefore, an object of the present invention is to provide a fluorine-containing coating composition that provides a coating film that has excellent resistance to repeated wetting, cooling, and heating, and a coated article having a coating film formed using the fluorine-containing coating composition. [Means for solving the problem]

[0005] As a result of intensive investigations to solve the above problems, the present inventors have found that by mixing a fluorine-containing copolymer with an isocyanate-based curing agent containing a polyoxyalkylene group, a fluorine-containing coating composition can be obtained that gives a coating film excellent in resistance to repeated wetting, cooling, and heating, and have arrived at the present invention.

[0006] That is, the present inventors have found that the above problems can be solved by the following configuration. [1] A composition for a fluorine-containing coating material comprising a fluorine-containing copolymer and an isocyanate-based curing agent, The isocyanate-based curing agent is at least one selected from the group consisting of curing agents having an isocyanate group and curing agents having a blocked isocyanate group, The isocyanate-based curing agent has a polyoxyalkylene group. Fluorine-containing paint composition. [2] The polyoxyalkylene group is at least one selected from the group consisting of a polyoxyethylene group and a polyoxypropylene group. The fluorine-containing coating composition according to [1]. [3] The polyoxyalkylene group is a polyoxypropylene group. The fluorine-containing coating composition according to [1] or [2]. [4] The isocyanate-based curing agent is a curing agent having a blocked isocyanate group. The fluorine-containing coating composition according to any one of [1] to [3]. [5] The curing agent having a blocked isocyanate group is a blocked isocyanurate curing agent. The fluorine-containing coating composition according to [4]. [6] The fluorine-containing copolymer is a fluorine-containing copolymer having a crosslinkable group. The fluorine-containing coating composition according to any one of [1] to [5]. [7] The fluorine-containing copolymer is a fluorine-containing copolymer having units based on a fluoroolefin and units based on a monomer having no fluorine atom, The fluorine-containing coating composition according to any one of [1] to [6]. [8] At least a part of the monomers not having a fluorine atom is a monomer having a crosslinkable group. The fluorine-containing coating composition according to [7]. [9] The average number of oxyalkylene groups in the polyoxyalkylene group is 8 or more. The fluorine-containing coating composition according to any one of [1] to [8].

[10] The content of the isocyanate-based curing agent is 3% by mass or more relative to the fluorine-containing coating composition. The fluorine-containing coating composition according to any one of [1] to [9].

[11] A coated article having a coating film formed using the fluorine-containing coating composition according to any one of [1] to

[10] . [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a fluorine-containing coating composition that gives a coating film that has excellent resistance to repeated wetting, cooling, and heating, and also to provide a coated article having a coating film formed using the fluorine-containing coating composition. DETAILED DESCRIPTION OF THE INVENTION

[0008] The terms used in the present invention are explained below. A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. (Meth)acrylate is a general term for acrylate and methacrylate, and (meth)acrylic is a general term for acrylic and methacrylic. The term "unit" refers collectively to an atomic group based on one molecule of the monomer formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a part of the atomic group. The content (mol %) of each unit relative to the total units contained in the polymer can be determined by analyzing the polymer by nuclear magnetic resonance spectroscopy (NMR). The hydroxyl value is a value measured in accordance with the method of JIS K 0070-3 (1992). The number average molecular weight (Mn) is a value measured by gel permeation chromatography using polystyrene as a standard substance. The solid mass of a paint is the mass of the paint after removing the solvent if the paint contains a solvent. Note that components that make up the solid content of the composition other than the solvent are considered solids even if they are in liquid form. The solid mass of a paint is determined as the mass remaining after heating 1g of paint at 130°C for 20 minutes.

[0009] <Fluorine-containing paint composition> The fluorine-containing coating composition of the present invention contains a fluorine-containing copolymer and an isocyanate-based curing agent. Coatings formed using the fluorine-containing coating composition of the present invention have excellent resistance to repeated wetting, cooling, and heating. Furthermore, by using the fluorine-containing coating composition of the present invention, coatings that exhibit excellent resistance to repeated wetting, cooling, and heating, even after bending, can be provided without reducing weather resistance, regardless of the environment in which they are placed. Resistance to repeated wetting, cooling, and heating refers to the resistance (adhesion, cracking, blistering) of a coating film to repeated temperature shocks of low and high temperatures. Insufficient resistance to repeated wetting, cooling, and heating, results in poor durability of coatings and coated articles in harsh environments, such as cold regions where temperatures can reach -20°C or subtropical regions where temperatures can reach 50°C. In particular, when applied to PCM steel sheets, which are often used for folded-gable roofs, sufficient resistance to repeated wetting, cooling, and heating is required even after bending. The present invention makes it possible to provide a fluorine-containing coating composition that provides a coating film that exhibits excellent resistance to repeated wetting, cooling, and heating, even after bending, and to provide coated articles having coatings formed using the fluorine-containing coating composition. The reason for this is not entirely clear, but is thought to be as follows. Fluorine-containing paint coatings are known to have good elongation properties at relatively high temperatures of about 20°C to about 50°C, but have issues with elongation properties at low temperatures. The isocyanate-based curing agent of the present invention contains a polyoxyalkylene group, and the presence of this polyoxyalkylene group allows coatings formed using the fluorine-containing paint composition of the present invention to be endowed with elongation properties at relatively low temperatures of about 5°C to about 20°C. As a result, excellent elongation properties can be achieved over a wide temperature range while retaining and complementing the characteristics of conventional paints. In other words, a coating film with excellent resistance to repeated exposure to heat and humidity can be provided.

[0010] (Isocyanate curing agent) The isocyanate curing agent in the present invention is at least one selected from the group consisting of curing agents having an isocyanate group and curing agents having a blocked isocyanate group. The blocked isocyanate group refers to an isocyanate group blocked with a blocking agent. The isocyanate curing agent in the present invention is not particularly limited as long as it is an isocyanate curing agent having a polyoxyalkylene group.

[0011] Examples of the polyoxyalkylene group include a polyoxyethylene group, a polyoxypropylene group, a polyoxybutene group, and a polyoxypentene group. From the viewpoint of improving the resistance to repeated wetting and heating and the elongation of the coating film, a polyoxyethylene group or a polyoxypropylene group is preferred, and a polyoxypropylene group is more preferred.

[0012] The average number of oxyalkylene groups in the polyoxyalkylene groups of the isocyanate-based curing agent in the present invention can be any number, but from the viewpoint of improving the resistance to repeated wetting and cooling and the elongation of the coating film, it is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and particularly preferably 16 or more.

[0013] The isocyanate group or blocked isocyanate group in the present invention is preferably a group in which an isocyanate group contained in a polyisocyanate monomer or a polyisocyanate derivative becomes a bond. The polyisocyanate monomer is preferably an aliphatic polyisocyanate, an alicyclic polyisocyanate, or an aromatic polyisocyanate. From the viewpoint of improving the resistance to repeated wetting and cooling and the elongation of the coating film, the polyisocyanate derivative is preferably a multimer or modified product of the polyisocyanate monomer (such as an adduct, allophanate, biuret, or isocyanurate), and more preferably an isocyanurate modified product. An isocyanurate-based curing agent is a curing agent that contains at least one isocyanurate group.

[0014] Specific examples of aliphatic polyisocyanates include tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, aliphatic diisocyanates such as lysine diisocyanate, lysine triisocyanate, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, and bis(2-isocyanatoethyl) 2-isocyanatoglutarate. Specific examples of the alicyclic polyisocyanate include alicyclic diisocyanates such as isophorone diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, and hydrogenated xylylene diisocyanate. Specific examples of aromatic polyisocyanates include aromatic diisocyanates such as xylylene diisocyanate.

[0015] Among the isocyanate-based curing agents, curing agents having a blocked isocyanate group are preferred from the viewpoints of ease of handling as a one-component type paint and improving the resistance to repeated wetting and cooling and the elongation of the coating film.

[0016] A curing agent having a blocked isocyanate group has at least one isocyanate group blocked by a blocking agent (blocked isocyanate group). A blocked isocyanurate curing agent is an isocyanurate curing agent having at least one blocked isocyanate group, and is one type of curing agent having a blocked isocyanate group. When a curing agent having a blocked isocyanate group is heated, the blocking agent is liberated from the blocked isocyanate group to produce a curing agent having an isocyanate group.

[0017] The curing agent having a blocked isocyanate group preferably has two or more blocked isocyanate groups, more preferably four or more blocked isocyanate groups per molecule, and preferably 30 or less blocked isocyanate groups. When the curing agent having a blocked isocyanate group has the number of blocked isocyanate groups within the above range, the coating film has improved resistance to repeated exposure to heat and humidity and elongation.

[0018] The blocking agent is preferably at least one compound selected from the group consisting of dimethylpyrazole, pyrazole, ε-caprolactam, methyl ethyl ketoxime, and active methylene compounds. Among these, from the viewpoint of improving the resistance to repeated wetting and cooling and the elongation of the coating film, dimethylpyrazole or pyrazole is more preferable, and dimethylpyrazole is even more preferable. Two or more blocking agents may be used in combination. Specific examples of the active methylene compound include dimethyl malonate, diethyl malonate, methyl acetoacetate, and ethyl acetoacetate.

[0019] From the viewpoint of improving the resistance to repeated exposure to heat and humidity and the elongation of the coating film, the isocyanate curing agent in the present invention is preferably an isocyanate curing agent having a polyoxypropylene group, more preferably an isocyanurate curing agent having a polyoxypropylene group, still more preferably an isocyanurate curing agent having a polyoxypropylene group in which the average number of oxypropylene groups in the polyoxypropylene group is 12 or more, and particularly preferably a blocked isocyanurate curing agent having a polyoxypropylene group in which the average number of oxypropylene groups in the polyoxypropylene group is 16 or more.

[0020] The isocyanate curing agent may be used alone or in combination of two or more kinds.

[0021] The content of the isocyanate curing agent in the fluorine-containing coating composition of the present invention can be set as appropriate, but from the viewpoint of improving the wet-cool-heat cycle resistance and elongation of the coating film formed using the fluorine-containing coating composition without reducing its weather resistance, the lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, particularly preferably 13% by mass or more, and most preferably 15% by mass or more, relative to the fluorine-containing coating composition. Also, from the same viewpoint as the lower limit, the upper limit is preferably 30% by mass or less, more preferably 23% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less, relative to the fluorine-containing coating composition.

[0022] (Fluorine-containing copolymer) The fluorine-containing copolymer of the present invention is a copolymer having fluorine atoms. The fluorine-containing copolymer is preferably a copolymer having units based on a fluoroolefin (hereinafter also referred to as "units X1") and units based on a monomer not having fluorine atoms. Furthermore, the fluorine-containing copolymer is preferably a copolymer having units X1 and a crosslinkable group reactive with an isocyanate group.

[0023] Fluoroolefins are olefins in which one or more hydrogen atoms have been substituted with fluorine atoms. In the fluoroolefins, one or more hydrogen atoms that are not substituted with fluorine atoms may be substituted with chlorine atoms. The number of carbon atoms in the fluoroolefins is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4. Specific examples of fluoroolefins include CF2=CF2, CF2=CFCl, CF2=CHF, CH2=CF2, CF2=CFCF3, CF2=CHCF3, CF3CH=CHF, CF3CF=CH2, and compounds of the formula CH2=CX f1 (CF2) n1 Y f1 (In the formula, X f1 and Y f1 are independently a hydrogen atom or a fluorine atom, and n1 is an integer of 2 to 10. As the fluoroolefin, from the viewpoint of improving copolymerizability and resistance to repeated wetting and cooling and heating of the coating film, CF2=CFCl, CF3CH=CHF, and CF3CF=CH2 are preferred, and CF2=CFCl is more preferred. Two or more types of fluoroolefins may be used in combination.

[0024] The content of units X1 is preferably from 20 to 70 mol %, more preferably from 40 to 60 mol %, based on all units contained in the fluorine-containing copolymer, from the viewpoint of weather resistance of the coating film.

[0025] Specific examples of the crosslinkable group include a hydroxy group, a carboxy group, and an amino group. From the viewpoint of excellent reactivity with an isocyanate group, a hydroxy group or a carboxy group is preferred, and a hydroxy group is more preferred. The number of crosslinkable groups may be 1 or more than 2. Two or more types of the crosslinkable groups may be used in combination.

[0026] The fluorine-containing copolymer preferably contains units (hereinafter also referred to as units X2) based on the above-mentioned monomer having a crosslinkable group (hereinafter also referred to as monomer X2), and more preferably, the units based on a monomer not having a fluorine atom contain monomer X2. The monomer X2 has the formula X11 -Y 11 (hereinafter also referred to as monomer X21), a monomer represented by formula X 12 -Y 12 (hereinafter also referred to as monomer X22) or allyl alcohol is preferred. The symbols in the formula have the following meanings. X 11 is CH2=CH-, CH(CH3)=CH- or CH2=C(CH3)-, preferably CH2=CH- or CH(CH3)=CH-. Y 11 is a carboxy group or a monovalent saturated hydrocarbon group having a carboxy group and having 1 to 12 carbon atoms, and is preferably a carboxy group or a carboxyalkyl group having 1 to 10 carbon atoms. X 12 is CH2=CHO- or CH2=CHCH2O-. Y 12 is a monovalent saturated hydrocarbon group having 2 to 12 carbon atoms and having a hydroxy group. The monovalent saturated hydrocarbon group may be linear or branched. Furthermore, the monovalent saturated hydrocarbon group may be composed of a ring structure or may include a ring structure. The monovalent saturated hydrocarbon group is preferably an alkyl group having 2 to 6 carbon atoms or an alkyl group containing a cycloalkylene group having 6 to 8 carbon atoms.

[0027] Specific examples of the monomer X21 include CH2=CHCOOH, CH(CH3)=CHCOOH, CH2=C(CH3)COOH, and the monomers of the formula CH2=CH(CH2) n2 Examples of the compound include compounds represented by COOH (where n2 represents an integer of 1 to 10). Specific examples of the monomer X22 include CH2=CHO-CH2-cycloCH 10 -CH2OH, CH2=CHCH2O-CH2-cycloC6H 10 Examples of such compounds include -CHOH, CH=CHOCHCHOH, CH=CHCHOCHCHOH, CH=CHOCHCHCHCHOH, and CH=CHCHOCHCHCHCHOH. 10"-" represents a cyclohexylene group, and "-cycloCH 10 The binding site of - is usually 1,4-. The monomer X2 may be used alone or in combination of two or more kinds.

[0028] When the fluorine-containing copolymer contains units X2, the crosslinkable groups of the units X2 act as crosslinking points, and the crosslinking reaction between the fluorine-containing copolymers proceeds via the isocyanate-based curing agent to form a crosslinked product.

[0029] In the coating film, the proportion (reaction rate) of crosslinkable groups that have actually undergone a crosslinking reaction and become crosslinking points relative to all crosslinkable groups is preferably 20.0 to 99.9%, more preferably 30.0 to 90.0%, even more preferably 40.0 to 70.0%, and particularly preferably 45.0 to 60.0%, from the viewpoint of improving the wet-cold-heat cycle resistance and elongation of the coating film without reducing the weather resistance of the coating film. Here, the "proportion (reaction rate) of crosslinkable groups that have actually undergone a crosslinking reaction and become crosslinking points relative to the total crosslinkable groups" can be calculated by ((amount of isocyanate groups (-N=C=O) (number of moles) / total amount of crosslinkable groups (number of moles)) x 100 (%)" in the coating film.

[0030] The content of units X2 is preferably from 1 to 40 mol %, more preferably from 5 to 25 mol %, and even more preferably from 5 to 20 mol %, based on all units contained in the fluorine-containing copolymer.

[0031] From the viewpoint of the processability of the coating film, the fluorine-containing copolymer is 13 -Z 13 In particular, it is more preferable that the unit based on a monomer having no fluorine atom has the monomer X3. X 13is CH2=CHC(O)O-, CH2=C(CH3)C(O)O-, CH2=CHOC(O)-, CH2=CHCH2OC(O)-, CH2=CHO- or CH2=CHCHO-, and CH2=CHOC(O)-, CH2=CHCH2OC(O)-, CH2=CHO- or CH2=CHCHO- are preferred in terms of excellent weather resistance of the coating film.

[0032] Z 13 is a monovalent hydrocarbon group having 1 to 24 carbon atoms. The monovalent hydrocarbon group may be linear or branched. The monovalent hydrocarbon group may be composed of a ring structure or may contain a ring structure. The monovalent hydrocarbon group may be a monovalent saturated hydrocarbon group or a monovalent unsaturated hydrocarbon group. The monovalent hydrocarbon group is preferably an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and more preferably an alkyl group having 2 to 12 carbon atoms, a cycloalkyl group having 6 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a tert-butyl group, a hexyl group, a nonyl group, a decyl group, and a dodecyl group. A specific example of the cycloalkyl group is a cyclohexyl group. A specific example of the aralkyl group is a benzyl group. Specific examples of the aryl group include a phenyl group and a naphthyl group.

[0033] The monomer X3 may be used alone or in combination of two or more kinds. Specific examples of the monomer X3 include ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, vinyl acetate, vinyl pivalate, vinyl neononanoate (manufactured by HEXION, trade name "Veova 9"), vinyl neodecanoate (manufactured by HEXION, trade name "Veova 10"), vinyl benzoate tert-butyl (meth)acrylate, and benzyl (meth)acrylate. When the fluorine-containing copolymer contains units X3, the content of units X3 is preferably from 1 to 70 mol %, more preferably from 10 to 50 mol %, based on all units contained in the fluorine-containing copolymer.

[0034] The fluorine-containing copolymer preferably contains 20 to 70 mol %, 1 to 40 mol % and 0 to 70 mol % of units X1, units X2 and units X3 in this order based on all units contained in the fluorine-containing copolymer. From the viewpoint of weather resistance of the coating film, Mn of the fluorine-containing copolymer is preferably from 2,000 to 40,000, more preferably from 5,000 to 30,000, and even more preferably from 7,000 to 20,000. The fluorine-containing copolymer preferably has a hydroxyl value. When the fluorine-containing copolymer is a fluorine-containing copolymer having a hydroxyl value, the hydroxyl value of the fluorine-containing copolymer is preferably from 1 to 200 mgKOH / g, more preferably from 40 to 100 mgKOH / g, and even more preferably from 50 to 60 mgKOH / g, from the viewpoint of adhesion of the coating film.

[0035] The Tg of the fluorine-containing copolymer is preferably from 0 to 120°C, more preferably from 10 to 100°C, and even more preferably from 20 to 80°C. When the Tg of the fluorine-containing copolymer is within the above range, the hardness of the coating film is improved.

[0036] The fluorine-containing copolymer is produced by a known method. For example, the fluorine-containing copolymer is obtained by copolymerizing each monomer in the presence of a solvent and a radical polymerization initiator. Methods for producing the fluorine-containing copolymer include solution polymerization and emulsion polymerization. During or after the production of the fluorine-containing copolymer, a polymerization stabilizer, a polymerization inhibitor, a surfactant, etc. may be used, if necessary.

[0037] As the fluorine-containing copolymer, commercially available products may be used, and specific examples include the "Lumiflon" series (manufactured by AGC), the "Fluon" series (manufactured by AGC), the "Kynar" series (manufactured by Arkema), the "Zeffle" series (manufactured by Daikin Industries, Ltd.), the "Eterflon" series (manufactured by Eterflon), and the "Zendura" series (manufactured by Honeywell). Two or more types of fluorine-containing copolymers may be used in combination.

[0038] (Other ingredients) The fluorine-containing coating composition may be a composition in which the fluorine-containing copolymer is dissolved or dispersed in a liquid medium, or may be a composition that does not substantially contain a liquid medium (powder coating, etc.). Examples of the liquid medium include solvent-based media and aqueous media. In the fluorine-containing coating composition of the present invention, it is preferable that the fluorine-containing copolymer and the isocyanate-based curing agent are dissolved or dispersed in the liquid medium. Examples of the coating material in the present invention include coating materials in which the fluorine-containing copolymer and the isocyanate-based curing agent are dissolved in a solvent-based medium (solvent-based coating materials, etc.), and coating materials in which the fluorine-containing copolymer and the isocyanate-based curing agent are dispersed in an aqueous medium (water-based coating materials, etc.). The coating material is preferably a solvent-based coating material, as it can form a dense coating film and has excellent weather resistance. The phrase "the fluorine-containing coating composition is substantially free of a liquid medium" means that the content of the liquid medium is 0.1 mass % or less relative to the total mass of the fluorine-containing coating composition. When the medium is an aqueous medium, the aqueous medium may contain an organic solvent in addition to water, such as aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, and alcohol solvents such as methanol and ethanol. When the aqueous medium contains an organic solvent, the content thereof in the fluorine-containing coating composition is preferably 10% by mass or less, and more preferably 3% by mass or less.

[0039] When the medium is a solvent-based medium, examples of the organic solvent constituting the medium include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, alcohol solvents such as methanol and ethanol, hydrocarbon solvents such as mineral spirits and mineral turpentine, and halogenated compounds such as HCFC-225 (dichloropentafluoropropane) and chlorobenzene trifluoride. Among these, aromatic hydrocarbon solvents such as toluene and xylene are preferred, and xylene is more preferred.

[0040] When the fluorine-containing coating composition contains a liquid medium, the content of the liquid medium is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, relative to the fluorine-containing coating composition, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, relative to the fluorine-containing coating composition.

[0041] In addition to the above components, the fluorine-containing coating composition of the present invention may contain various additives as appropriate depending on the required properties, provided that the effects of the present invention are not impaired. Specific examples of such additives include ultraviolet absorbers, light stabilizers, curing catalysts, pigments, luster pigments, leveling agents, antifoaming agents, thickeners, wetting and dispersing agents, degassing agents, heat stabilizers, surface conditioners, adhesion improvers, matting agents, surfactants, antistatic agents, rust inhibitors, antifouling agents, stain-reducing treatment agents, plasticizers, adhesives, etc.

[0042] When the fluorine-containing coating composition of the present invention is used to form a highly transparent clear coating film, it may contain an ultraviolet absorber or light stabilizer as needed to provide an ultraviolet absorbing effect, protect the coated article from ultraviolet rays, and improve weather resistance. Typical ultraviolet absorbers that can be used preferably include benzophenol-, triazine-, or benzotriazole-based ultraviolet absorbers. Preferred light stabilizers that can be used include hindered amine- and phosphorus-based light stabilizers. The required content of the ultraviolet absorber varies depending on the thickness of the resulting cured coating film. Specifically, it is preferable that the ultraviolet absorber be contained at a concentration such that the ultraviolet transmittance of the resulting cured coating film at that thickness is less than 10%. For example, the content of the ultraviolet absorber is preferably 0.1 to 25% by mass, more preferably 0.5 to 20% by mass, even more preferably 1 to 15% by mass, and particularly preferably 2 to 10% by mass, relative to the fluorine-containing coating composition. If the content of the ultraviolet absorber is 0.1% by mass or more, the weather resistance of the coated article will be more excellent. If the content of the ultraviolet absorber is 25% by mass or less, yellowing of the coating film can be further suppressed.

[0043] As the curing catalyst, a tin-based curing accelerator such as dibutyltin laurate, a metal chelate compound such as aluminum chelate, an organic acid-based curing accelerator such as p-toluenesulfonic acid, an inorganic acid-based curing accelerator such as hydrochloric acid, an amino-based curing accelerator, etc. When using a curing agent that dissociates at low temperatures, this curing catalyst is not necessary.

[0044] The fluorine-containing coating composition of the present invention may contain a pigment from the viewpoint of improving the appearance of a coated article obtained by applying a coating material obtained from the fluorine-containing coating composition of the present invention, and from the viewpoint of protecting the substrate from ultraviolet rays and improving weather resistance. For example, inorganic pigments such as titanium oxide, red iron oxide, yellow ochre, calcium carbonate, aluminum silicate, white carbon, black pigment carbon black, metal composite oxide pigments such as Cu-Cr-Mn and Mn-Bi, finely powdered silicic acid, etc., and organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone, isoindolinone, benzimidazolone, dioxazine, etc. Titanium oxide, a white pigment, is particularly preferred because of its high coloring power and ultraviolet absorption ability. The pigment content can be changed as appropriate depending on the pigment used, but is preferably 5 to 400 mass % relative to the fluorine-containing coating composition, more preferably 10 to 300 mass %, even more preferably 20 to 250 mass %, and particularly preferably 24 to 200 mass %.

[0045] The fluorine-containing coating composition may further contain a silane coupling agent. When the fluorine-containing coating composition contains a silane coupling agent, the coating film formed using the fluorine-containing coating composition contains a hydrolysate of the silane coupling agent or a hydrolysis condensate thereof. This improves the adhesion between the formed coating film and the chemical conversion coating.

[0046] The hydrolyzate of a silane coupling agent refers to a compound obtained by hydrolyzing the hydrolyzable group in the silane coupling agent.The hydrolyzate may be a compound in which all of the hydrolyzable groups are hydrolyzed (complete hydrolyzate), or a compound in which only a portion of the hydrolyzable groups are hydrolyzed (partial hydrolyzate).In other words, the hydrolyzate may be a complete hydrolyzate, a partial hydrolyzate, or a mixture thereof. Furthermore, the hydrolysis condensate refers to a compound obtained by condensing the hydrolyzate. The hydrolysis condensate may be one in which all hydrolyzable groups are hydrolyzed and all of the hydrolyzates are condensed (complete hydrolysis condensate), or one in which some of the hydrolyzable groups are hydrolyzed and some of the hydrolyzates are condensed (partial hydrolysis condensate). In other words, the hydrolysis condensate may be a complete hydrolysis condensate, a partial hydrolysis condensate, or a mixture thereof. The hydrolysis condensate may also be a hydrolysis condensate obtained by condensing hydrolyzates of two or more compounds of the silane coupling agent. The coating film may contain both a hydrolysate of a silane coupling agent and a hydrolysis condensate thereof, or may contain only one of them.

[0047] Specific examples of the silane coupling agent include a silane coupling agent having an epoxy group, a silane coupling agent having a mercapto group, a silane coupling agent having an imidazole group, and a silane coupling agent having a methacryl group.

[0048] Specific examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. Specific examples of the silane coupling agent having a mercapto group include γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane. Specific examples of silane coupling agents having an imidazole group include imidazole silane. Specific examples of silane coupling agents having a methacryl group include γ-(methacryloyloxypropyl)trimethoxysilane and γ-(methacryloyloxypropylmethyl)dimethoxysilane. Among these, a silane coupling agent having an epoxy group, a silane coupling agent having a mercapto group, or a silane coupling agent having an imidazole group is preferred, a silane coupling agent having an epoxy group is more preferred, and among these, 3-glycidoxypropyltrimethoxysilane is even more preferred.

[0049] When the fluorine-containing coating composition contains a silane coupling agent, the content of the silane coupling agent relative to the fluorine-containing coating composition is preferably 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, and even more preferably 1 to 3 mass %, from the viewpoints of achieving better adhesion between the coating film and the chemical conversion coating and improving weather resistance and resistance to repeated wetting and cooling.

[0050] The contents of the various additives mentioned above are preferably 0.01 to 5 mass% for light stabilizers, 0.01 to 1 mass% for surface conditioners, 0.1 to 5 mass% for wetting and dispersing agents, 0.01 to 3 mass% for antifoaming agents, 0.01 to 10 mass% for thickeners, 0.01 to 5 mass% for adhesion improvers, and 0.01 to 10 mass% for matting agents, relative to the fluorine-containing coating composition.

[0051] The fluorine-containing coating composition of the present invention can be produced, for example, by mixing a fluorine-containing copolymer, an isocyanate-based curing agent, and optional components. When a liquid medium is contained as an optional component, the liquid medium may be the polymerization solvent used in producing the fluorine-containing copolymer.

[0052] <Painted items> The fluorine-containing coating composition of the present invention can be applied to an article to be coated to form a coating film, thereby producing a coated article. The fluorine-containing coating composition of the present invention may be applied as a primer layer on the surface of the article to form a primer coating film, or may be applied as a topcoat layer on any primer layer on the surface of the article to form a topcoat coating film. The fluorine-containing coating composition of the present invention may also be used as a clear coating composition to form a clear coating film, or as an enamel coating composition to form an enamel coating film.

[0053] The thickness of a coating film formed using the fluorine-containing coating composition of the present invention is preferably 0.5 to 200 μm, more preferably 1 to 100 μm, even more preferably 2 to 80 μm, and particularly preferably 5 to 40 μm.

[0054] The substrate to be coated with the fluorine-containing coating composition of the present invention is preferably a metal substrate. Examples of materials for the metal substrate include metals such as aluminum, iron, copper, zinc, magnesium, cobalt, nickel, tin, and titanium, and alloys containing any of these metals (e.g., aluminum alloys, stainless steel, carbon steel, special steel, and brass). Among these, aluminum, aluminum alloys, stainless steel, carbon steel, and special steel, which are often used in fields requiring resistance to repeated exposure to heat and humidity, are preferred, and aluminum and aluminum alloys are more preferred. Specific examples of the shape of the metal substrate include a flat plate, a column, a sphere, and a rod. The coated article refers to all articles coated with a paint using the fluorine-containing paint composition of the present invention, and also includes laminates in which a plurality of coating films are laminated.

[0055] The substrate to be coated with the fluorine-containing coating composition of the present invention may be prepared by applying the fluorine-containing coating composition of the present invention to a chemical conversion coating formed on the surface of a metal substrate to form a coating layer, and then heat-curing the coating layer at 160 to 250° C. When the fluorine-containing coating composition of the present invention is applied to a metal substrate, it is preferably applied to the surface of the chemical conversion coating as described above.

[0056] When the coating material of the present invention is a water-based coating material or a solvent-based coating material, examples of the coating method include spray coating, squeegee coating, flow coating, bar coating, spin coating, dip coating, screen printing, gravure printing, die coating, inkjet coating, curtain coating, and methods using a brush or spatula. When the coating material of the present invention is a powder coating material, examples of the coating method include electrostatic coating, electrostatic spraying, electrostatic dipping, atomization, fluidized bed dipping, spraying, spraying, thermal spraying, and plasma thermal spraying.

[0057] The fluorine-containing coating composition of the present invention can be used for the exterior of vehicles, building materials, etc. The resulting coating film has excellent resistance to repeated wetting, cooling, and heating, making the fluorine-containing coating composition of the present invention particularly suitable for application to PCM steel sheets, and can maintain sufficient resistance to repeated wetting, cooling, and heating, weather resistance, and durability even when applied to PCM steel sheets such as those used in folded-height roofs, which are exposed to severe environments. [Example]

[0058] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples. The amount of each component in the tables below is based on mass. Furthermore, n1 and n2 in the structural formula represent the average number of oxyalkylene groups in the polyoxyalkylene group.

[0059] [Fluorine-based paint manufacturing] Fluorine-containing coating compositions 1 to 19 were obtained by mixing the components listed in Table 1. Details of the components listed in the table are as follows. F1: Lumiflon LF-200 (fluororesin composition manufactured by AGC, solid content 60% by mass, Mn 20,000, hydroxyl value 52 mgKOH / g) F2: Lumiflon LF-600X (fluororesin composition manufactured by AGC, solid content 50% by mass, Mn 20,000, hydroxyl value 57 mgKOH / g) Curing agent 1: A blocked isocyanurate curing agent 1 containing a polyoxypropylene group, represented by the following structural formula (where n1 represents 12, and * represents a bonding position).

[0060] [ka]

[0061] Curing agent 2: A blocked isocyanurate curing agent 2 containing a polyoxypropylene group, represented by the following structural formula (where n2 represents 16, and * represents a bonding position).

[0062] [ka]

[0063] Hardener 3: Duranate TPA-B80X (Asahi Kasei Corporation product) Hardener 4: Sumidur BL3175 (product of Sumika Cobest Lourentan Co., Ltd.) Hardener 5: Desmodur PL350 (product of Sumika Cobest Lourentan) UVA1: TINUVIN-1130 (benzotriazole-based UV absorber, BASF product) UVA2: TINUVIN-479 (hydroxyphenyltriazine ultraviolet absorber, BASF product) UVA3: TINUVIN-384-2 (benzotriazole-based UV absorber, BASF product) Light stabilizer: TINUVIN-123 (hindered amine light stabilizer, BASF product) Defoamer: Disparlon #1933 (Kusumoto Chemicals Co., Ltd. product) Curing catalyst: 100 times diluted xylene solution of dibutyltin dilaurate Leveling agent: BYK-342 (product of BYK Japan) Silane coupling agent: XIAMETER(R) OFS-6040 SILANE (a product of Dow Corning Toray) Wetting and dispersing agent: DISPERBYK-163 (product of BYK Japan) Pigment: Tipaque PFC105 (titanium dioxide) (Ishihara Sangyo Co., Ltd. product)

[0064] [Preparation of test specimens] - Clear coating test piece - Each fluorine-containing clear coating composition listed in Table 1 was applied to a chromate-treated aluminum substrate (140 × 240 mm, thickness 0.5 mm) using a bar coater, and then heated at 190°C for 60 seconds to obtain a clear coating film (primer layer) with a dry thickness of 20 μm. Next, a clear coating of Bonflon #7046 (product of AGC Coatec Co., Ltd.) was applied to the clear coating film as a topcoat layer using a bar coater. After that, the film was heated at 230°C for 60 seconds to obtain a topcoat layer with a dry film thickness of 20 μm. Finally, a clear coating test piece was obtained in which the total dry film thickness of the primer layer and topcoat layer was 40 μm. - Enamel coating test piece - A paint containing polyester resin and epoxy resin was applied to a chromate-treated aluminum substrate (140 × 240 mm, thickness 0.5 mm) using a bar coater, and then heated at 230°C for 60 seconds to obtain a primer plate with a dry undercoat layer of 5 μm thick. Next, each fluorine-containing enamel paint composition listed in Table 2 was applied to the primer layer of the primer plate using a bar coater. The plate was then heated at 230°C for 60 seconds to obtain an enamel coating film (topcoat layer) with a dry film thickness of 25 µm. Finally, an enamel coating test piece was obtained in which the combined dry film thickness of the primer layer and topcoat layer was 30 µm.

[0065] (Fluorine-containing clear coating composition)

[0066] [Table 1]

[0067] (Fluorine-containing enamel paint composition)

[0068] [Table 2]

[0069] [Test piece evaluation] The test specimens were cured for one week after preparation and then subjected to the following bending test, cyclic wet / cold heat resistance test, accelerated weather resistance test, and stretching test. The stretching test of the enamel-coated test specimens was performed using a separate film, as described below. The results are shown in Tables 1 and 2.

[0070] -Bending test- Based on the flex resistance (cylindrical mandrel method) test of JIS K5600-5-1, the coated test plate and cylindrical mandrel testing machine were left in a test room adjusted to 5°C for 18 hours, and the test was carried out at 5°C. Each test specimen was bent (4T) using a mandrel with a diameter of 2 mm, and the presence or absence of cracks in the coating film at the bent portion was visually inspected with a magnifying glass. Cases where no cracks were found in the coating film were rated as ◯, and cases where cracks were found were rated as ×. - Wet, cold and hot cycle resistance test - Based on JIS K5600-7-4 Cycle 1, a humidity and humidity test was conducted using a temperature and humidity test chamber (Nagano Science, Model: LH44-15P) with one cycle consisting of 18 hours of high-temperature humidity (50±3°C, 95% RH), 3 hours of low-temperature humidity (-20±2°C), and 3 hours of standard conditions (23±2°C, 50±5% RH). After the bending test, each test piece was subjected to 10 cycles, and then visually inspected with a magnifying glass for the presence or absence of cracks in the coating film at the bent section. A rating of ◯ was given to cases where no cracks were found in the coating film, and a rating of × was given to cases where cracks were found. If no cracks were found in the coating film after this test, it can be said that the coating film has high humidity and heat cycle resistance and is excellent. -Accelerated weather resistance test- An accelerated weather resistance test (irradiation conditions (1 cycle): illuminance 100mW, temperature 50°C, humidity 40%, 6 hours, condensation 2 hours) was carried out using a Super UV accelerated testing machine (Iwasaki Electric Co., Ltd.; Eye Super UV Tester SUV-W161) for 140 cycles. The initial 60-degree specular gloss value before the test was set at 100%, and the retention of the 60-degree specular gloss value of the coating film after the test (gloss retention (%)) was determined and evaluated according to the following criteria. The 60-degree specular gloss value was measured using a variable-angle gloss meter (product name "UGV-6P", incident / reflecting angle 60 degrees, manufactured by Suga Test Instruments Co., Ltd.). The higher the gloss retention, the longer the appearance of the coating film will last, i.e., the higher the weather resistance and the better the design properties. Over 70%... Between 50% and 70%...△ Less than 50%...× - Extension test - Each fluorine-containing resin enamel paint listed in Table 2 was applied to a rectangular aluminum plate (10 mm × 20 mm × 25 μm) using a bar coater and then heated at 230°C for 60 seconds to produce an enamel coating film with a dry film thickness of 25 μm. The enamel coating film was peeled off from the aluminum plate to produce a film. The elongation of the film was evaluated using a Tensilon universal testing machine (A&D, RTC-1250A) at 5°C. The tensile tester's chuck grip distance or the test piece's gauge line distance was set to 10 mm, and the film was pulled at a rate of 10 mm / min, and the elongation (mm) until the coating film broke on the test piece was measured. The higher the elongation value, the higher and more excellent the elongation. If the coating film was too soft to measure, it was recorded as "-."

[0071] As shown in Tables 1 and 2, it was confirmed that the coating films of Examples 1 to 10 had better resistance to repeated wet and cold heat cycles than the coating films of Comparative Examples 11 to 19. It was also confirmed that differences in weather resistance and elongation were observed depending on the amount of curing agent.

Claims

1. A fluorine-containing coating composition comprising a fluorine-containing copolymer and an isocyanate-based curing agent, The isocyanate-based curing agent is at least one selected from the group consisting of a curing agent having an isocyanate group and a curing agent having a blocked isocyanate group, The isocyanate-based curing agent has a polyoxyalkylene group. Fluorine-containing paint composition.

2. The polyoxyalkylene group is at least one selected from the group consisting of a polyoxyethylene group and a polyoxypropylene group. The fluorine-containing coating composition according to claim 1.

3. the polyoxyalkylene group is a polyoxypropylene group; The fluorine-containing coating composition according to claim 1.

4. The isocyanate-based curing agent is a curing agent having a blocked isocyanate group. The fluorine-containing coating composition according to claim 1.

5. the curing agent having a blocked isocyanate group is a blocked isocyanurate curing agent; The fluorine-containing coating composition according to claim 4.

6. The fluorine-containing copolymer is a fluorine-containing copolymer having a crosslinkable group. The fluorine-containing coating composition according to any one of claims 1 to 5.

7. The fluorine-containing copolymer is a fluorine-containing copolymer having units based on a fluoroolefin and units based on a monomer having no fluorine atom, The fluorine-containing coating composition according to any one of claims 1 to 5.

8. At least a part of the monomers having no fluorine atoms is a monomer having a crosslinkable group. The fluorine-containing coating composition according to claim 7.

9. the average number of oxyalkylene groups in the polyoxyalkylene group is 8 or more; The fluorine-containing coating composition according to any one of claims 1 to 5.

10. The content of the isocyanate-based curing agent is 3% by mass or more relative to the fluorine-containing coating composition. The fluorine-containing coating composition according to any one of claims 1 to 5.

11. A coated article having a coating film formed using the fluorine-containing coating composition according to any one of claims 1 to 5.

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