Topcoat paint composition and multi-layer coating film

Abstract

To provide a topcoat paint composition that can achieve both weather resistance, opacity, and appropriate flexibility in the formed coating film. [Solution] The topcoat paint composition comprises a main component and a curing agent, wherein the main component comprises at least a resin (A), a resin (B), a pigment, and a solvent, the resin (A) is an acrylic polyol resin having a hydroxyl value of 30 mgKOH / g or more and less than 100 mgKOH / g of resin solids, the resin (B) is an alkoxysilyl group-containing acrylic resin having a hydroxyl value of 0 mgKOH / g or more and less than 30 mgKOH / g of resin solids, and the silicon content in the resin solids is 5% by mass or more and 30% by mass or less in terms of SiO2, the curing agent comprises at least a polyisocyanate, the mass ratio of resin (A) to resin (B), (A):(B) is 80:20 to 20:80, and the pigment content is 5% by mass or more and 50% by mass or less, the topcoat paint composition.

Description

Technical Field

[0001] The present disclosure relates to a topcoat paint composition and a multilayer coating film.

Background Art

[0002] Conventionally, a method of forming a coating film on the outer wall surface of a building to protect it from deterioration has been known. Such a coating film includes a topcoat film formed on the outermost surface and optionally other coating films such as a primer film. High weather resistance may be required for the topcoat film depending on its use.

[0003] As a technique for enhancing the weather resistance of a topcoat film, a technique of incorporating an acrylic resin containing a silyl group in the side chain into the topcoat paint composition used for forming the topcoat film is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an acrylic resin containing a silyl group in the side chain is contained in the topcoat paint composition, the weather resistance of the formed topcoat film can be enhanced. Also, when the amount of pigment contained in the topcoat paint composition is increased, hiding power can be enhanced. However, such a coating film can become hard and brittle due to the polysiloxane structure in the resin skeleton and the pigment. In this case, when displacement occurs in the building body due to cracking or the like, the topcoat film may not be able to follow the displacement and may crack. For example, even when the primer film formed under the topcoat film is a flexible coating film that easily follows the displacement of the body, if the topcoat film is a hard coating film that is difficult to follow the displacement, there is a problem that the topcoat film may crack.

[0006] This disclosure has been made in view of the above, and aims to provide a topcoat paint composition that can achieve both weather resistance, opacity, and flexibility in the formed coating film. [Means for solving the problem]

[0007] (1) The present disclosure relates to a topcoat paint composition used to form a topcoat film on the exterior surface of a building, wherein the topcoat paint composition comprises a main component and a curing agent, wherein the main component comprises at least a resin (A), a resin (B), a pigment, and a solvent, wherein the resin (A) is an acrylic polyol resin having a hydroxyl value of 30 mgKOH / g or more and less than 100 mgKOH / g of resin solids, and the resin (B) has a hydroxyl value of 0 mgKOH / g or more and less than 30 mgKOH / g of resin solids. The present invention relates to an alkoxysilyl group-containing acrylic resin having a silicon content of 5% by mass or more and 30% by mass or less in terms of SiO2, wherein the curing agent contains at least polyisocyanate, and the mass ratio of resin (A) to resin (B), (A):(B), when the total resin solids content of the topcoat paint composition is set to 100, is 80:20 to 20:80, and the pigment content relative to the total solids content of the topcoat paint composition is 5% by mass or more and 50% by mass or less.

[0008] (2) The topcoat paint composition according to (1), wherein the mass ratio of resin (A) to resin (B), (A):(B), when the total resin solids content of the topcoat paint composition is set to 100, is 70:30 to 30:70.

[0009] (3) The topcoat paint composition according to (1) or (2), wherein the solvent comprises an aliphatic hydrocarbon-containing non-aqueous solvent, and the polyisocyanate comprises an aliphatic isocyanate as a constituent unit.

[0010] (4) The topcoat paint composition according to any one of (1) to (3), further comprising a light stabilizer and an ultraviolet absorber.

[0011] (5) A multi-layer coating film formed on the exterior surface of the building by the topcoat coating composition described in any of (1) to (4) and the undercoat coating composition. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide a topcoat paint composition that can achieve both weather resistance and appropriate flexibility in the formed coating film. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure are described below. This disclosure is not limited to the embodiments described below.

[0014] <Topcoat paint composition> The topcoat paint composition according to this embodiment is a two-component paint composition comprising a main component and a hardener. The topcoat paint composition is prepared by mixing the main component and the hardener immediately before applying the topcoat paint composition to the object to be coated.

[0015] (Main ingredient) The main component comprises at least resin (A), resin (B), pigment, and solvent. Resin (A) is an acrylic polyol resin having a hydroxyl value of 30 mgKOH / g or more and less than 100 mgKOH / g of resin solids. Resin (B) is an alkoxysilyl group-containing acrylic resin having a hydroxyl value of 0 mgKOH / g or more and less than 30 mgKOH / g of resin solids, and a silicon content in the resin solids of 5% by mass or more and 30% by mass or less in terms of SiO2. By including both resin (A) and resin (B) in the topcoat paint composition, the resulting topcoat film can achieve both weather resistance and appropriate flexibility.

[0016] Resin (A) is an acrylic polyol resin, which is an acrylic resin having one or more hydroxyl groups in its molecule. Such an acrylic polyol resin is not particularly limited as long as the hydroxyl value of the resin solids is 30 mg KOH / g or more and less than 100 mg KOH / g. By including the above acrylic polyol resin in the topcoat paint composition, the flexibility of the formed topcoat film can be moderately improved. The acrylic polyol resin can react with the polyisocyanate contained in the curing agent to form urethane bonds. If the hydroxyl value of the acrylic polyol resin is less than 30 mg KOH / g, the crosslinking density in the topcoat film is too low, making the topcoat film brittle. Also, the tackiness of the coating surface increases, making it more susceptible to dirt. If the hydroxyl value of the acrylic polyol resin is 100 mg KOH / g or more, the crosslinking density in the topcoat film is too high, making it difficult to follow the displacement of the underlying layer.

[0017] In this specification and in the claims, the hydroxyl values ​​of resin (A) and resin (B) can be measured in accordance with JIS K 0070.

[0018] The above-mentioned acrylic polyol resin can be obtained, for example, by polymerizing or copolymerizing an ethylenically unsaturated monomer having a hydroxyl group in its molecule with other monomers as needed. The polymerization method for obtaining the above-mentioned acrylic polyol resin is not particularly limited, and known methods such as solution polymerization, high-pressure polymerization, and continuous polymerization can be used.

[0019] The monomers used to obtain the above-mentioned acrylic polyol resin are not particularly limited, but include, for example, ethylene-based unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; alkyl ester monomers of ethylene-based unsaturated carboxylic acids such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; alicyclic esters of ethylene-based unsaturated carboxylic acids such as cyclohexyl (meth)acrylate and norbonyl (meth)acrylate; monoester monomers of ethylene-based unsaturated dicarboxylic acids such as ethyl maleate, butyl maleate, ethyl itaconate, and butyl itaconate; and 2-hydroxyethyl (meth)acrylate, acrylic acid Examples include: hydroxyl group-containing ethylene-based unsaturated carboxylic acid ester monomers, which are primary hydroxyl group-containing monomers such as 4-hydroxybutyl (meth)acrylate and the reaction product of 2-hydroxyethyl (meth)acrylate and ε-caprolactone; hydroxyl group-containing ethylene-based unsaturated carboxylic acid ester monomers, which are secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate; unsaturated fatty acid glycidyl ester monomers such as glycidyl acrylate and glycidyl methacrylate; vinyl cyanide monomers such as (meth)acrylonitrile and α-chloroacrylonitrile; saturated aliphatic carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; styrene monomers such as styrene, α-methylstyrene, and vinyltoluene; and the like. The above monomers may be used individually or in combination of two or more. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0020] Resin (A) may contain fluorine, silicon, nitrogen, or any other element in its structure. If resin (A) contains silicon, the silicon content in the resin solids is preferably 0% by mass or more and 15% by mass or less in terms of SiO2.

[0021] The weight-average molecular weight of the acrylic polyol resin (resin (A)) is not particularly limited, but it is preferably between 5,000 and 200,000.

[0022] Resin (B) is an alkoxysilyl group-containing acrylic resin. The alkoxysilyl group-containing acrylic resin can form siloxane bonds between molecules by hydrolysis. When siloxane bonds are formed in the topcoat film, the weather resistance of the topcoat film is improved. In resin (B) in the main agent, although some siloxane bonds may be formed within the molecule, it is preferable that siloxane bonds are mainly formed between molecules during the formation of the topcoat film. The alkoxy group in the alkoxysilyl group is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, a propionyloxy group, a butoxy group, etc. These alkoxy groups can be bonded to 1 to 3 silicon atoms in one alkoxysilyl group.

[0023] The silicon content of the above alkoxysilyl group-containing acrylic resin is 5% by mass or more and 30% by mass or less in terms of SiO2. When the above silicon content is less than 5% by mass, sufficient weather resistance of the formed topcoat film cannot be obtained. When the above silicon content exceeds 30% by mass, the topcoat film becomes too hard and difficult to follow the displacement of the lower layer, and cracks are likely to occur in the topcoat film. The above silicon content can be measured by analyzing the ash obtained by the A method (muffle furnace temperature: 600 ± 25 °C) specified in JIS K 7250-4 with a fluorescent X-ray analyzer.

[0024] Resin (B) may optionally contain a hydroxyl group in the molecule. The hydroxyl value of the resin solid content of resin (B) is 0 mgKOH / g or more and less than 30 mgKOH / g.

[0025] The above resin (B) can be obtained, for example, by copolymerizing an acrylic monomer, an alkoxysilyl group-containing monomer, and other monomers copolymerizable with the above monomers as required. In addition to the above, the above resin (B) can also be obtained by modifying an acrylic resin obtained by polymerizing an acrylic monomer with an alkoxysilyl group-containing monomer.

[0026] Examples of the above acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, isobonyl (meth)acrylate, etc. These may be used individually or in combination of two or more.

[0027] Examples of the above alkoxysilyl group-containing monomers include vinyltrimethoxysilane, vinyltriethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropyltrippropoxysilane, γ-(meth)acryloxypropyltributoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ-(meth)acryloxy Examples include cypropylmethyldiethoxysilane, γ-(meth)acryloxypropylmethyldipropoxysilane, γ-(meth)acryloxypropylmethyldibutoxysilane, γ-(meth)acryloxypropyldimethylmethoxysilane, γ-(meth)acryloxypropyldimethylethoxysilane, γ-(meth)acryloxypropyldimethylpropoxysilane, γ-(meth)acryloxypropyldimethylbutoxysilane, trimethoxysilylstyrene, triethoxysilylstyrene, dimethoxymethylsilylstyrene, diethoxymethylsilylstyrene, etc. These may be used individually or in combination of two or more.

[0028] The above-mentioned other monomers are not particularly limited as long as they are copolymerizable with the above-mentioned acrylic monomers and alkoxysilyl group-containing monomers, but examples include aromatic hydrocarbon vinyl monomers such as styrene, α-methylstyrene, chlorostyrene, 4-hydroxystyrene, and vinyltoluene; vinyl esters and allyl compounds such as vinyl acetate, vinyl propionate, vinyl versatate, and diallyl phthalate; nitrile group-containing vinyl monomers such as (meth)acrylonitrile; epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate; hydroxyl group-containing vinyl monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, hydroxystyrene, and hydroxyl group-containing vinyl-modified hydroxyalkyl vinyl monomers; vinyl methyl ether, propylene, and butadiene. These may be used individually or in combination of two or more.

[0029] The weight-average molecular weight of the alkoxysilyl group-containing acrylic resin (resin (B)) is not particularly limited, but is preferably 5,000 or more and 200,000 or less.

[0030] When the total resin solids content of the topcoat paint composition is set to 100, the mass ratio of resin (A) to resin (B), (A):(B), is 80:20 to 20:80. This allows for both weather resistance and appropriate flexibility in the formed topcoat film. Preferably, the above mass ratio, (A):(B), is 70:30 to 30:70.

[0031] The pigments improve the weather resistance of the formed topcoat film and impart desirable appearances such as a matte finish or metallic color to the topcoat film. While not particularly limited, examples of pigments include titanium dioxide, diatomaceous earth (silicon dioxide), calcium carbonate, kaolin clay, talc, barium sulfate, white carbon, carbon, red iron oxide, yellow ochre, cyanine blue, and lustrous pigments (such as aluminum flakes) obtained by crushing vapor-deposited metal films into metal flakes. These may be used individually or in combination of two or more. The above pigments may be subjected to inorganic or organic surface treatments to improve weather resistance and dispersibility.

[0032] The pigment is contained in the topcoat paint composition in an amount of 5% by mass or more and 50% by mass or less, relative to the total solid content. The total solid content of the topcoat paint composition refers to the sum of the mass of the resin solids and the mass of the pigment. If the pigment content is less than 5% by mass, sufficient opacity cannot be obtained in the formed topcoat film. If the pigment content exceeds 50% by mass, the formed topcoat film becomes too hard, making it difficult to follow the displacement of the underlying layer, and making the topcoat film prone to cracking. Preferably, the pigment content is 20% by mass or more and 50% by mass or less.

[0033] The solvent is not particularly limited as long as it can dissolve and / or disperse the resin (A), resin (B), and pigment. Preferably, the solvent is an aliphatic hydrocarbon-containing non-aqueous solvent. Aliphatic hydrocarbon-containing non-aqueous solvents have lower toxicity and polarity compared to non-aqueous solvents containing aromatic hydrocarbons such as toluene and xylene. Therefore, using an aliphatic hydrocarbon-containing non-aqueous solvent can reduce adverse effects on worker health and the environment during painting. Furthermore, even when the topcoat paint composition is applied to the upper layer of an old paint film for repair purposes, shrinkage and blistering of the old paint film are less likely to occur, thus improving adhesion to the old paint film. Examples of the aliphatic hydrocarbons include n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane. The aliphatic hydrocarbon-containing non-aqueous solvent containing these aliphatic hydrocarbons is a solvent containing one or more of the above aliphatic hydrocarbons, and mineral spirits (turpentine) can also be used.

[0034] The main component may contain other components not listed above, such as additives, as needed. For example, it is preferable to include at least one of a light stabilizer and an ultraviolet absorber. This can further improve the weather resistance of the topcoat film formed. Specific examples of other components that may be included in the main component include, for example, preservatives, fungicides, antibacterial agents, defoaming agents, pigment dispersants, thickeners, leveling agents, rust inhibitors, compatibility aids, fibers, matting agents, ultraviolet absorbers, antioxidants, light stabilizers, adsorbents, catalysts, dehydrating agents, and the like.

[0035] Light stabilizers capture radicals generated within the topcoat film and suppress degradation of the topcoat film due to photo-oxidation. Examples of light stabilizers include hindered amine-based light stabilizers. Hindered amine-based light stabilizers have a 2,2,6,6-tetramethylpiperidine skeleton in their molecule. Specific examples of hindered amine-based light stabilizers include, for example, phenyl-4-piperidinyl carbonate, bis(2,2,6,6-tetramethyl-4-piperidyl) succinate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(N-methyl-2,2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis(2,2,6,6-tetra-methyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidyl) decandioate. Examples include peridyl) esters and reaction products of 1,1-dimethylethyl hydroperoxide and octane, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, etc. These may be used individually or in combination of two or more.

[0036] UV absorbers absorb ultraviolet light that enters the topcoat film, thereby suppressing the deterioration of the topcoat film. Examples of UV absorbers include benzophenone-based UV absorbers, benzolithoazole-based UV absorbers, salicylate-based UV absorbers, and cyanoacrylate-based UV absorbers.

[0037] Benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2' Examples include -dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2-hydroxy-4-(2-methacryloyloxyethoxy)benzophenone, and 2,2'-dihydroxy-4(3-methacryloxy-2-hydroxypropoxy)benzophenone.

[0038] Examples of benzotriazole-based absorbents include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, and 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole.

[0039] Examples of salicylate-based UV absorbers include phenyl salicylate, p-octylphenyl salicylate, 2,4-di-t-butylphenyl-3,5'-di-t-butyl-4'-hydroxylbenzoate, and 4-tert-butylphenyl salicylate.

[0040] Examples of cyanoacrylate-based UV absorbers include ethyl-2-cyano-3,3-diphenyl acrylate, 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, and butyl 2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate.

[0041] The above UV absorbers may be used individually or in combination of two or more types.

[0042] The content of the light stabilizer in the topcoat paint composition is preferably 0.1% by mass or more and 5.0% by mass or less based on the total mass of the topcoat paint composition. The content of the ultraviolet absorber in the topcoat paint composition is preferably 0.1% by mass or more and 5.0% by mass or less based on the total mass of the topcoat paint composition.

[0043] (Hardening agent) The curing agent contains a polyisocyanate. The polyisocyanate is not particularly limited as long as it has an average of two or more isocyanate groups in one molecule. Examples of polyisocyanates include aliphatic isocyanates such as hexamethylene diisocyanate, pentamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate); and aromatic isocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. The polyisocyanate may also be a modified form of the above compounds (e.g., urethanes, carbodiimides, uretdiones, uretonimines, biuret compounds, isocyanurates, etc.). The above polyisocyanates may be used alone or in combination of two or more types.

[0044] It is preferable that the polyisocyanate contains aliphatic isocyanate as a constituent unit. This can suppress yellowing of the formed coating film. Furthermore, when an aliphatic hydrocarbon-containing non-aqueous solvent is used as the solvent, the solubility of the polyisocyanate in the solvent can be improved.

[0045] The curing agent may contain solvents and other components in addition to those listed above. Examples of solvents and other components that may be included in the main component are those exemplified above. It is preferable to use an aliphatic hydrocarbon-containing non-aqueous solvent as the solvent. It is also preferable to include a catalyst that promotes the hydrolysis of the alkoxysilyl groups of resin (B). Organometallic compounds are used as curing catalysts. Among these, tin-based compounds are preferred from the viewpoint of curability of the coating film. Specific examples of the above tin compounds include dioctyl tin bis(2-ethylhexyl malate), a condensate of dioctyl tin oxide or dibutyl tin oxide and silicate, dibutyl tin dioctoate, dibutyl tin dilaurate, dibutyl tin distearate, dibutyl tin diacetylacetonate, dibutyl tin bis(ethyl malate), dibutyl tin bis(butyl malate), dibutyl tin bis(2-ethylhexyl malate), and dibutyl tin bis(oleyl malate). Examples include stanus octoate, tin stearate, di-n-butyltin stearate oxide, dibutyltin bisisononyl-3-mercaptopropionate, dioctyltin bisisononyl-3-mercaptopropionate, octylbutyltin bisisononyl-3-mercaptopropionate, dibutyltin bisisooctylthioglucolate, dioctyltin bisisooctylthioglucolate, and octylbutyltin bisisooctylthioglucolate.

[0046] The method for preparing the main component and hardener is not particularly limited, and they can be prepared by mixing the above components using a device such as a disper or ball mill. The topcoat paint composition is prepared by mixing the main component and hardener. The mixing of the main component and hardener is performed immediately before application of the topcoat paint composition. The mixing ratio of the main component and hardener can be appropriately adjusted depending on the amount of reactive groups (such as hydroxyl groups) and isocyanate groups contained in the main component and hardener, respectively.

[0047] <Multi-layer coating> The multilayer coating includes a topcoat coating formed by the topcoat paint composition according to the above embodiment, and a primer coating formed by the primer paint composition. That is, a multilayer coating including the primer coating and the topcoat coating formed on top thereof is formed on the exterior surface (surface) of the building that is to be coated.

[0048] The primer composition is not particularly limited, and examples include a primer composition comprising an aqueous acrylic emulsion or aqueous epoxy emulsion and a crosslinking agent. The aqueous acrylic emulsion may contain functional groups for crosslinking with the crosslinking agent. Examples of such functional groups include carboxyl groups and carbonyl groups. Therefore, aqueous acrylic emulsions can be obtained by copolymerizing a monomer having a carboxyl group or a monomer having a carbonyl group with another monomer in the presence of a dispersant.

[0049] Examples of monomers having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, and maleic acid. Examples of monomers having a carbonyl group include acrylamide, methacrylamide, and vinyl oxo compounds such as methyl ketone and ethyl ketone. The crosslinking agent can be appropriately selected according to the functional group of the aqueous acrylic emulsion, and examples include hydrazide compounds, carbodiimide compounds, and aziridine compounds.

[0050] Examples of epoxy resins used in aqueous epoxy emulsions include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyglycol type epoxy resin, bisphenol F type epoxy resin, epoxidized oil, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and the like.

[0051] In addition to the above, the primer paint composition may optionally contain water or an organic solvent (dispersion medium), and other components that may be included in the topcoat paint composition. The method for preparing the primer paint composition is not particularly limited, and it can be prepared by mixing each component in the same manner as the method for preparing the main component and hardener of the topcoat paint composition.

[0052] The film thickness of the undercoat varies depending on the type of undercoat and is not particularly limited. For example, in the case of a sealer, the film thickness can be several μm; in the case of a primer, the film thickness can be 30 to 100 μm; and in the case of a filler, the film thickness can be 500 to 5000 μm. These undercoats may be used individually or in combination with other different undercoats. The film thickness of the topcoat is not particularly limited, but for example, it is 30 to 100 μm.

[0053] <Method for forming a multi-layer coating (repair method)> The method for forming a multi-layer coating according to this embodiment is a method for forming the multi-layer coating on the exterior surface (surface) of a building to be coated. The building may be one in which a coating has already been formed on the surface of the exterior wall, and the method for forming the multi-layer coating may be performed as a method for renovating the building. Alternatively, the building may be a newly constructed building in which no coating has been formed on the exterior surface. The material of the exterior wall of the building on which the multi-layer coating is formed is not particularly limited and may be concrete, mortar, slate board, PC board, ALC board, siding board, wood, stone, plastic, metal, etc.

[0054] The method of applying the paint composition in the steps of forming the topcoat and the undercoat is not particularly limited, and a general method can be used. For example, a painting method using painting tools such as rollers, air sprayers, airless sprayers, and brushes can be used. After application, the paint film hardens and is formed after a certain period of time has elapsed. The steps of forming the topcoat and the undercoat may each be repeated multiple times. The paint compositions used in these steps may be of the same type or different types.

[0055] If the building to be coated is one that already has a coating, a step of cleaning the surface of the building and a step of removing the old coating by scraping or other means may be provided prior to the formation of the multi-layer coating, but these steps are not required. In this case, the topcoat paint composition may be applied to the old coating already formed on the surface of the building to form the topcoat coating.

[0056] In the above method for forming a multilayer coating, the formation of other layers, such as coatings other than those mentioned above, on the object to be coated is not excluded. Other layers other than those mentioned above may be arbitrarily formed on the object to be coated. [Examples]

[0057] The contents of this disclosure will be described in more detail below based on the following examples. The contents of this disclosure are not limited to the following examples.

[0058] [Preparation of topcoat paint composition] (Example 1) The topcoat paint composition according to Example 1 was prepared using the formulation shown in Table 1 below. Unless otherwise specified, the numerical values ​​indicating the amount of each component in the following tables refer to parts by mass. In the following tables, "resin A solid content mass ratio" and "resin B solid content mass ratio" refer to the mass ratios of resin A (resin A-1 to resin A-5) and resin B (resin B-1 to resin B-6), respectively, when the total resin solid content of the topcoat paint composition is set to 100. Similarly, "pigment content" refers to the pigment content (mass %) relative to the total solid content of the topcoat paint composition.

[0059] (Other examples and comparative examples) The topcoat paint compositions for each example and comparative example were prepared in the same manner as in Example 1, except that the formulation of the topcoat paint composition was as shown in Tables 1 to 3 below.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] Details of the abbreviations and symbols listed in Tables 1-3 are shown below.

[0064] Resin A-1: ​​Acrylic polyol resin, hydroxyl value of solids: 45 mg KOH / g, silicon content (SiO2 equivalent): 10% by mass, resin solids: 50% by mass Resin A-2: Acrylic polyol resin, hydroxyl value of solids: 30 mg KOH / g, silicon content (SiO2 equivalent): 0% by mass, resin solids: 50% by mass Resin A-3: Acrylic polyol resin, hydroxyl value of solids: 120 mg KOH / g, silicon content (SiO2 equivalent): 0% by mass, resin solids: 50% by mass Resin A-4: Acrylic polyol resin, hydroxyl value of solids: 100 mg KOH / g, silicon content (SiO2 equivalent): 0% by mass, resin solids: 50% by mass Resin A-5: Acrylic polyol resin, hydroxyl value of solids: 25 mg KOH / g, silicon content (SiO2 equivalent): 0% by mass, resin solids: 50% by mass Resin B-1: Acrylic resin containing alkoxysilyl groups, hydroxyl value of solids: 25 mg KOH / g, silicon content (SiO2 equivalent): 5% by mass, resin solids: 50% by mass Resin B-2: Acrylic resin containing alkoxysilyl groups, solid content hydroxyl value: 0 mg KOH / g, silicon content (SiO2 equivalent): 10% by mass, resin solids: 50% by mass Resin B-3: Acrylic resin containing alkoxysilyl groups, hydroxyl value of solids: 0 mg KOH / g, silicon content (SiO2 equivalent): 30% by mass, resin solids: 50% by mass Resin B-4: Acrylic resin containing alkoxysilyl groups, hydroxyl value of solids: 0 mg KOH / g, silicon content (SiO2 equivalent): 3% by mass, resin solids: 50% by mass Resin B-5: Acrylic resin containing alkoxysilyl groups, hydroxyl value of solids: 0 mg KOH / g, silicon content (SiO2 equivalent): 5% by mass, resin solids: 50% by mass Resin B-6: Acrylic resin containing alkoxysilyl groups, hydroxyl value of solids: 0 mg KOH / g, silicon content (SiO2 equivalent): 50% by mass, resin solids: 50% by mass

[0065] The solids content hydroxyl value of each resin listed above was determined using a method in accordance with JIS K 0070. The silicon content (SiO2 equivalent) was measured using Method A (muffle furnace temperature: 600±25℃) as specified in JIS K 7250-4.

[0066] Pigment 1: Titanium Oxide Pigment 2: Extender pigment (silica) Solvent: Mineral spirits

[0067] Light stabilizer: TINUVIN 292 (manufactured by BASF Japan, hindered amine-based light stabilizer) UV absorber: TINUVIN384-2 (manufactured by BASF Japan, benzotriazole-based UV absorber) Additives: Dispersants, thickeners, defoamers, fungicides, antibacterial agents, and dehydrating agents were used as appropriate. Polyisocyanate: Duranate TSA-100 (manufactured by Asahi Kasei Corporation)

[0068] [Coating film elasticity test] (Preparation of test boards) A slate board (15 cm long, 7 cm wide) was coated with a first primer paint (Nippon Paint Co., Ltd., product name: Nippe Water-Based Cation Sealer Transparent) using a medium-pile roller to obtain the first primer film. Next, a second water-based primer paint (product name: DAN Filler Epoxy, Nippon Paint Co., Ltd., Waterproof Multi-Layer Coating Material RE) was applied to the first primer film using a textured roller (standard grit), cured at room temperature for one day, and then the same primer paint was applied again, cured at room temperature for one day to obtain the second primer film. Finally, the topcoat paint composition according to each example and comparative example was applied twice with a medium-pile roller (pile length 13 mm), and cured at room temperature for seven days to form a multi-layer coating. The first and second coats of the topcoat paint composition were applied with a 4-hour interval between them. The sides and back of the slate board on which the above multi-layer coating was formed were sealed with a solvent-based two-component paint to create a test panel.

[0069] (Evaluation method) The test plates for each of the above-described examples and comparative examples were immersed in tap water at 20±2°C for 2 hours, and then immediately cooled in a constant temperature chamber at -20±2°C for 2 hours. This 4-hour cycle was repeated 100 times and 200 times, after which the test plates were left to stand in the test chamber for 2 hours. Finally, the presence or absence of cracks in the coating was visually checked. The results were evaluated according to the following evaluation criteria. The results are shown in Tables 1-3. A score of 3 or higher was considered a pass.

[0070] (Evaluation Criteria) No cracks were observed at 5:200 cycles. 4: No cracks were observed after 100 cycles, but fine cracks were observed after 200 cycles. 3: No cracks were observed after 100 cycles, but visible cracks were observed after 200 cycles. Microscopic cracks are observed at 2:100 cycles. Visible cracks were observed at 1:100 cycles.

[0071] [Weather resistance test] (Preparation of test boards) An SPCC-SB board (150 x 70 x 0.8 mm) was coated with a primer (Hypon Fine Primer II Gray, manufactured by Nippon Paint Co., Ltd.) using a medium-pile roller, and cured at room temperature for one day to form a primer film. Next, the topcoat paint composition according to each example and comparative example was applied twice with a medium-pile roller, and cured at room temperature for seven days to form a multi-layer paint film. The first and second coats of the topcoat paint composition were applied with a four-hour interval between them. The sides and back of the SPCC-SB boards on which the above multi-layer paint films were formed were sealed with a solvent-based two-component paint to create test boards.

[0072] (Evaluation method) The test plates for each of the above-described examples and comparative examples were subjected to the xenon lamp method 1 specified in JIS K 5600 7-7 (irradiance of 60 W / m² between 300 nm and 400 nm). 2 , or at 340 nm, the irradiance is 0.51 W / (m 2 An accelerated weathering test was conducted using cycle A (continuous operation, wetting time 18 minutes, drying period 102 minutes, relative humidity during drying period: 40-60%). The gloss of the test boards before and after the test was measured using a gloss meter (Konica Minolta, GM256A), and the gloss retention rate (gloss after the test (%), with the gloss before the test set to 100%) was calculated. The calculation results were evaluated according to the following evaluation criteria. The results are shown in Tables 1-3. A score of 3 or higher was considered a pass.

[0073] (Evaluation Criteria) 5: Gloss retention rate of over 90% after 5,000 hours 4: Gloss retention rate of 80% or more but less than 90% after 5,000 hours 3: Gloss retention rate of 70% or more but less than 80% after 5,000 hours 2: Gloss retention rate of 60% or more but less than 70% after 5,000 hours Gloss retention rate is less than 60% after 1:5000 hours.

[0074] [Weathering resistance test (high irradiance)] The test board preparation conditions were the same as above, but a weather resistance test was conducted under more stringent conditions. Specifically, the evaluation method followed Method 1 of the xenon lamp method specified in JIS K 5600 7-7, with an irradiance of 180W set between 300nm and 400nm for the xenon lamp, and an accelerated weather resistance test was performed using cycle A (continuous operation, wetting time 18 minutes, drying period 102 minutes, relative humidity during drying period: 40-60%). The gloss retention rate was calculated in the same manner as above, and the calculation results were evaluated according to the following evaluation criteria. The results are shown in Tables 1-3. A score of 3 or higher was considered a pass.

[0075] (Evaluation Criteria) 5: Gloss retention rate of over 90% after 3000 hours 4: Gloss retention rate of 80% or more but less than 90% after 3000 hours 3: Gloss retention rate of 70% or more but less than 80% after 3,000 hours 2: Gloss retention rate of 60% or more but less than 70% after 3,000 hours Gloss retention rate is less than 60% after 1:3000h

[0076] [Concealment Test] (Preparation of test boards) A slate board (15 cm long, 7 cm wide) was coated with a first primer paint (product name: Nippon Paint Water-Based Cation Sealer White, manufactured by Nippon Paint Co., Ltd.) using a medium-pile roller to obtain the first primer film. Subsequently, a second water-based primer paint (product name: Perfect Surf, manufactured by Nippon Paint Co., Ltd.) was applied to the first primer film using a medium-pile roller to obtain the second primer film.

[0077] (Evaluation method) The first and second primer films, which were laminated as described above, were coated once or twice with the topcoat paint compositions according to each example and comparative example using a medium-pile roller (pile length 13 mm). Each painted film was visually evaluated according to the following evaluation criteria. The results are shown in Tables 1 to 3. A score of 3 or higher was considered acceptable.

[0078] (Evaluation Criteria) 5: One top coat will completely cover the undercoat. 4: With one coat of topcoat, the topcoat is partially visible, but with two coats, the undercoat is completely hidden. 3: With one coat of topcoat, the topcoat is translucent overall, but with two coats of topcoat, the undercoat is completely hidden. 2: After two coats of topcoat paint, some areas become transparent. 1: After two coats of topcoat, the topcoat is translucent overall.

[0079] The results shown in Tables 1-3 confirm that the topcoat films in each example are able to achieve a balance of weather resistance, opacity, and appropriate flexibility compared to the topcoat films in the comparative examples.

Claims

1. A topcoat paint composition used to form a topcoat film on the exterior surface of a building, The aforementioned topcoat paint composition comprises a main component and a hardening agent. The main component comprises at least resin (A), resin (B), pigment, and solvent. The resin (A) is an acrylic polyol resin having a hydroxyl value of 30 mg KOH / g or more and less than 100 mg KOH / g of resin solids. The resin (B) has a hydroxyl value of 0 mg KOH / g or more and less than 30 mg KOH / g of resin solids, and the silicon content in the resin solids is SiO ２ An acrylic resin containing alkoxysilyl groups in an amount of 5% to 30% by mass, calculated as follows: The curing agent comprises at least a polyisocyanate, When the total resin solids content of the topcoat paint composition is set to 100, the mass ratio of resin (A) to resin (B), (A):(B), is 80:20 to 20:

80. A topcoat paint composition wherein the content of the pigment relative to the total solid content of the topcoat paint composition is 5% by mass or more and 50% by mass or less.

2. The topcoat paint composition according to claim 1, wherein the mass ratio of resin (A) to resin (B), (A):(B), when the total resin solids content of the topcoat paint composition is set to 100, is 70:30 to 30:

70.

3. The solvent comprises an aliphatic hydrocarbon-containing non-aqueous solvent, The topcoat paint composition according to claim 1 or 2, wherein the polyisocyanate comprises an aliphatic isocyanate as a constituent unit.

4. The topcoat paint composition according to claim 1 or 2, further comprising a light stabilizer and an ultraviolet absorber.

5. A multi-layer coating film formed on the exterior surface of the building by the topcoat coating composition and the undercoat coating composition described in claim 1.

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