JP2023024373A - Coating formation method and laminated coating - Google Patents

Abstract

To provide a coating formation method capable of forming a coating excellent in coating film physical properties such as whitening resistance.SOLUTION: In the coating formation method for coating a surface of an inorganic material with an aqueous clear coating material, the aqueous clear coating material contains a resin component (A) and a crosslinking agent (B). The resin component (A) contains an acrylic resin (A1) in which the content of a carboxyl group-containing monomer in a resin-constituting component is 5 wt.% or less. The crosslinking agent (B) is a carbodiimide compound. The carbodiimide compound is contained in an amount of 0.1-10 pts.wt. in terms of solid content based on 100 pts.wt. of the solid content of the resin component (A).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a novel film forming method and a laminated film.

In recent years, environmental concerns such as the reduction of volatile organic compounds (VOC) have been increasing, and in the coating field, there is a shift from solvent-based coating materials using organic solvents to water-based coating materials.

One of the problems with water-based coating materials such as those described above is the improvement of physical properties of coating films such as stain resistance and water resistance. Techniques related to introduction of a cross-linking agent have been proposed to address such problems (for example, Patent Document 1). However, simply introducing a cross-linking agent may not provide whitening resistance. In particular, when the whitening resistance of the clear coating material (topcoat) applied to inorganic materials such as exposed concrete surfaces is insufficient, the texture (design) peculiar to inorganic materials may be impaired. In addition, a phenomenon that the surface of the concrete base material becomes a wet color may occur.

WO2017/006950

The present invention has been made in view of the above-mentioned problems, and by applying a specific water-based clear coating material to inorganic materials, it is possible to prevent wet color and improve the coating film such as whitening resistance. It is an object of the present invention to provide a method for forming a film that can form a film having excellent physical properties.

In order to solve the above-mentioned problems, the inventors of the present invention, as a result of intensive studies, applied a water-based clear coating material containing a specific acrylic resin as a resin component and a carbodiimide compound as a cross-linking agent in a specific weight ratio to an inorganic material. The present invention has been completed by conceiving a method of forming a film and a laminated film thereof.

That is, the present invention has the following features.
1. A film forming method for applying a water-based clear coating material to the surface of an inorganic material,
The water-based clear coating material contains a resin component (A) and a cross-linking agent (B),
The resin component (A) contains an acrylic resin (A1) in which the content of the carboxy group-containing monomer in the resin component is 5% by weight or less,
The cross-linking agent (B) is a carbodiimide compound,
A method for forming a film, wherein the resin component (A) contains 0.1 to 10 parts by weight of a carbodiimide compound in terms of solid content with respect to 100 parts by weight of the solid content of the resin component (A).
2. The resin component (A) includes an acrylic resin (A1) in which the content of the carboxy group-containing monomer in the resin component is 5% by weight or less, and the acrylic resin in which the content of the carboxy group-containing monomer in the resin component is the acrylic resin 1. Characterized by containing more acrylic resin (A2) than (A1). The film forming method according to .
3. 1. The solid content of the resin component (A) contains 55% by weight or more of the acrylic resin (A1) in terms of solid content. or 2. The film forming method according to .
4. Furthermore, 1. characterized by containing an organic amine compound as a basic organic compound (C). or 2. The film forming method according to .
5.1. or 2. A laminated film formed by the method for forming a film according to 1.

According to the film formation method of the present invention, by applying a specific water-based clear coating material to an inorganic material, a laminated film that prevents wet color and has excellent coating physical properties such as whitening resistance can be obtained. can be formed. As a result, the texture (design) peculiar to the inorganic material can be maintained for a long period of time.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated.

In the film forming method of the present invention, by applying a specific water-based clear coating material to an inorganic substrate, wet color is prevented, whitening resistance is improved, and the texture (design property) peculiar to inorganic materials can be retained for a long time.

<Inorganic material>
Inorganic materials constitute the surfaces of buildings, civil engineering structures, and the like. Examples of such base materials include concrete, mortar, siding boards, extruded boards, gypsum boards, perlite boards, bricks and tiles. These substrates may have a coating already formed on the surface thereof. The present invention is particularly preferably applied to concrete surfaces such as concrete wall surfaces. Such a concrete surface is usually made by mixing cement, water, aggregate, and other admixtures in appropriate proportions and mixing them together. It is obtained by The present invention can be applied to either newly installed concrete surfaces or aged concrete surfaces.

In addition, in the present invention, the inorganic material may be subjected to a treatment such as washing in advance. For the cleaning treatment, a method of applying various cleaning agents to the inorganic material and then washing with water may be adopted.

In the present invention, the inorganic material may be coated with a permeable anti-absorbent material and/or an undercoat material prior to coating with the water-based clear coating material. Of these, the permeable anti-absorbent material penetrates deeply into inorganic materials (concrete, mortar, etc. base materials) to form a water-repellent layer, blocking the infiltration of water, carbon dioxide gas, etc. from the outside. It prevents deterioration of strength due to neutralization of the material, and when there are steel frames, reinforcing bars, etc. inside the base material, it exhibits the effect of suppressing corrosion of them. In addition, it can exhibit the function of preventing the generation of efflorescence on the surface layer of the base material due to migration of the calcium component inside the base material.

Such a permeable water absorption preventing material is not particularly limited as long as it exhibits the above performance, and known or commercially available materials can be used. For example, a material containing a water repellent as a main component can be used. . Examples of water repellents include wax-based water repellents such as paraffin wax, polyethylene wax, and acrylic/ethylene copolymer wax; silicon-based water repellents such as silicone resins, polydimethylsiloxane, and hydrolyzable silane compounds; fluorine-based water repellents such as fluoroalkyl carboxylates, perfluoroalkyl phosphate esters, and perfluoroalkyltrimethylammonium salts; As the permeable water absorption inhibitor, one containing a silicon-based water repellent is preferable, and one containing a hydrolyzable silane compound is more preferable.

Examples of hydrolyzable silane compounds include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltributoxysilane, Propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, propyltributoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltripropoxysilane, butyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyl Dipropoxysilane, dimethyldibutoxysilane, diethyldimethylsilane, diethyldiethoxysilane, diethyldipropoxysilane, diethyldibutoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, hexyltripropoxysilane, octyltrimethoxysilane, octyltri ethoxysilane, octyltripropoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane and the like. These can be used alone or in combination of multiple types.

The permeable water absorption preventing material is, for example, a coloring agent, a thickening agent, a wetting agent, an antifreezing agent, a preservative, an antifungal agent, an antialgae agent, an antibacterial agent, and a dispersing agent, as long as it does not significantly impair the effects of the present invention. , an antifoaming agent, a resin, an ultraviolet absorber, an antioxidant, a catalyst, and the like. The permeable anti-water absorption material can be produced by uniformly mixing the components described above by a conventional method.

A known coating tool can be used to apply the permeable water absorption preventing material. As the coating tool, for example, known coating tools such as brushes, sprayers, rollers and coaters can be used. The required amount for applying the permeable water absorption preventing material may be appropriately set in consideration of the type and condition of the substrate, but is preferably 30 to 500 g/m ² (more preferably 80 to 400 g/m ² ). The application and drying of the permeable water absorption preventing material are preferably carried out at room temperature (0 to 40° C.). In the present invention, after the permeable water absorption preventing material is dried, the next step of coating can be performed. The interval between steps is preferably 1 hour or more and 10 days or less (more preferably 3 hours or more and 7 days or less).

Further, in the present invention, an undercoat material can be applied to the inorganic base material. The undercoat material can also be applied after coating the permeable water absorption preventing material. As the undercoat material, a coating material containing a synthetic resin emulsion can be preferably used. Examples of such synthetic resin emulsions include acrylic resin emulsions, epoxy-modified acrylic resin emulsions, urethane-modified acrylic resin emulsions, silicon-modified acrylic resin emulsions, fluorine-modified acrylic resin emulsions, and the like, or composite systems thereof. , one or more of these can be used. In the present invention, the synthetic resin emulsion preferably contains a functional group (for example, a carboxyl group) reactive with the carbodiimide compound (B) described below as a constituent component. Thereby, the effect of the present invention can be enhanced.

The synthetic resin emulsion of the undercoat material is preferably a silicone-modified acrylic resin emulsion. A silicon-modified acrylic resin emulsion is obtained by using a reactive silyl group-containing compound as an essential component. By using a silicon-modified acrylic resin emulsion, it is possible to improve adhesion, durability, etc., and to form a coating film with good stain resistance, weather resistance, yellowing resistance, water resistance, chemical resistance, etc. can be done.

The undercoat material may contain a water repellent in addition to the synthetic resin emulsion. As a result, the infiltration of water, carbon dioxide gas, or the like from the outside can be blocked, thereby enhancing the effect of preventing the reduction in strength due to the neutralization of the base material. Examples of the water repellent include those mentioned above, and a silicon water repellent is preferably used.

Preferably, the undercoat material forms a clear film. This makes it possible to take advantage of the texture of the inorganic material. Further, in addition to the above components, the undercoat material includes, for example, a coloring agent, a thickening agent, a wetting agent, an antifreezing agent, a film-forming aid, a preservative, an antifungal agent, within a range that does not significantly impair the effects of the present invention. Algicides, antibacterial agents, dispersants, antifoaming agents, resins, ultraviolet absorbers, light stabilizers, antioxidants, catalysts and the like may also be included. Furthermore, as long as the effects of the present invention are not significantly impaired, synthetic resin emulsions other than those described above can also be included as the synthetic resin emulsion. The undercoat material can be produced by uniformly mixing the components described above by a conventional method.

A known coating tool can be used to apply the undercoat material. As the coating tool, known coating tools such as brushes, sprayers, rollers and coaters can be used. The amount required for applying the undercoat material may be appropriately set in consideration of the type and condition of the base material, but is preferably about 30 to 500 g/m ² (more preferably 80 to 200 g/m ² ). be. The application and drying of the undercoat material are preferably carried out at room temperature.

<Aqueous clear coating material>
The aqueous clear coating material of the present invention (hereinafter also simply referred to as "coating material") is characterized by containing a resin component (A) and a cross-linking agent (B).

The resin component (A) (hereinafter also referred to as "(A) component") of the present invention is an acrylic resin (A1) (hereinafter referred to as " (Also referred to as "component (A1)"). By including such a component (A1), it is possible to exhibit excellent effects in terms of whitening resistance and the like.

The (A1) component of the present invention contains a (meth)acrylic acid alkyl ester as a main component of the resin component, and as other monomer components, the content of a carboxy group-containing monomer is 5% by weight or less (more preferably 0 to 4.8% by weight, more preferably 0.05 to 4.5% by weight, particularly preferably 0.1 to 3% by weight). In such a range, good physical properties of the film can be obtained. When the component (A1) has a carboxyl group-containing monomer, the whitening resistance can be further enhanced by cross-linking the component (B), which will be described later. In the present invention, alkyl acrylate and alkyl methacrylate are collectively referred to as alkyl (meth)acrylate. Moreover, a monomer is a general term for compounds having a polymerizable unsaturated double bond. In the present invention, "α to β" has the same meaning as "more than or equal to α and less than or equal to β".

Examples of (meth)acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) Acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, cyclohexyl (meth)acrylate and the like can be mentioned, and one or more of these can be used.

Examples of carboxyl group-containing monomers include
Carboxy group-containing monomers such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, isocrotonic acid, salicylic acid and the like can be mentioned, and one or more of these can be used.

Specific examples of other monomers include, for example,
aromatic monomers such as styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene, phenyl (meth)acrylate, benzyl (meth)acrylate;
Nitrile group-containing monomers such as (meth)acrylonitrile, vinylidene cyanide, α-cyanoethyl (meth)acrylate;
Maleic acid amide, (meth)acrylamide, N-monoalkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, 2-(dimethylamino)ethyl (methacrylate), N-[3-(dimethylamino)propyl] Amide group-containing monomers such as (meth)acrylamide and vinylamide;
Carbonyl group-containing monomers such as acrolein, diacetone (meth)acrylamide, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone;

aminomethyl acrylate, aminoethyl acrylate, aminopropyl (meth)acrylate, amino-n-butyl (meth)acrylate, butylvinylbenzylamine, vinylphenylamine, p-aminostyrene, N-methylaminoethyl (meth)acrylate, N - amino group-containing monomers such as t-butylaminoethyl (meth)acrylate;
glycidyl (meth) acrylate, diglycidyl fumarate, 3,4-epoxycyclohexyl (meth) acrylate, 3,4-epoxyvinylcyclohexane, allyl glycidyl ether, ε-caprolactone-modified glycidyl (meth) acrylate, β-methylglycidyl (meth) ) epoxy group-containing monomers such as acrylates;
hydroxyl group-containing monomers such as hydroxypropyl (meth)acrylate, ethylene glycol mono (meth) acrylate, glycerol mono (meth) acrylate;
vinylidene halide-based monomers such as vinylidene fluoride;
Alkoxysilyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, etc. contained monomers;
ethylene, propylene, isoprene, butadiene, vinyl ether, vinyl ketone; and the like. These can be used singly or in combination of two or more.

In the present invention, the other monomer component is preferably an acrylic silicone resin containing an alkoxysilyl group-containing monomer. In such a case, film physical properties such as weather resistance, stain resistance and water resistance can be enhanced.

Examples of the form of the component (A1) include water-soluble resins, water-dispersible resins, and composites thereof. In the present invention, a water-dispersible resin (resin emulsion) is preferred.

Component (A1) can be produced by a single-stage or multi-stage (two-stage, or three-stage or more) emulsion polymerization method or the like from a group of monomers obtained by appropriately mixing the above-mentioned monomers. As the polymerization method, a known method may be adopted, and in addition to ordinary emulsion polymerization, soap-free emulsion polymerization, feed emulsion polymerization, seed emulsion polymerization, and the like can also be adopted. At the time of polymerization, emulsifiers, initiators, dispersants, polymerization inhibitors, polymerization inhibitors, buffers, chain transfer agents and the like can be used.

As the emulsifier, various surfactants that can be used for emulsion polymerization can be used, and these may be reactive type having a polymerizable unsaturated double bond (reactive surfactant). As emulsifiers, anionic surfactants and nonionic surfactants are preferably used alone or in combination.

The glass transition temperature (hereinafter simply referred to as “Tg”) of the component (A1) is preferably set to −5° C. to 80° C. (more preferably 0 to 60° C.). If Tg is within such a range, the effects of the present invention can be stably obtained. In addition, Tg in the present invention is a value obtained by the Fox formula.

The average particle size of the acrylic resin of component (A1) is preferably 300 nm or less (more preferably 20 to 200 nm). If the average particle size is within such a range, the water resistance, weather resistance, chemical resistance, etc. of the coating can be improved. The average particle size referred to here is a value measured by a dynamic light scattering method.

Furthermore, the pH of the emulsion solution of component (A1) is preferably 7.0 or higher (more preferably 7.5 to 12, and still more preferably 8.0 to 11). In such a range, the stability of the covering material can be ensured.

The content of the component (A1) is preferably 55% by weight or more (more preferably 60 to 99.99% by weight, more preferably 60 to 99.99% by weight, more preferably 80 to 99.98% by weight, particularly preferably 90 to 99.95% by weight). The component (A1) is a main binder component in the component (A), and when the component (A1) satisfies the above range, it is advantageous for whitening resistance. In addition, it is possible to sufficiently secure film physical properties such as substrate followability, weather resistance, stain resistance, and water resistance.

In the present invention, it is preferable to include an acrylic resin (A2) (hereinafter also referred to as "(A2) component") having a higher content of carboxyl group-containing monomers than (A1) in the resin component. By including the component (A1) and the component (A2) in combination, it is possible to exhibit a more excellent effect in terms of whitening resistance.

The (A2) component of the present invention contains a (meth)acrylic acid alkyl ester as a main component of the resin component, and has a higher content of carboxy group-containing monomers in the resin component than the (A1) component ( preferably 3 to 80% by weight, more preferably 6 to 70% by weight, still more preferably 10 to 60% by weight). Within such a range, whitening resistance can be improved by a cross-linking reaction with a cross-linking agent (B) described later.

Examples of the form of the component (A2) include water-soluble resins, water-dispersible resins, and composites thereof. In the present invention, a water-dispersible resin (resin emulsion) is preferred. In addition, the (A2) component can be produced by the same method as for the (A1) component. The average particle size of the acrylic resin of component (A2) is preferably 300 nm or less (more preferably 20 to 200 nm). The average particle size referred to here is a value measured by a dynamic light scattering method.

Further, the component (A2) is preferably a resin (alkali-soluble or alkali-swellable resin) that dissolves or swells with alkali (neutralization). Thereby, the whitening resistance can be further improved. This mechanism of action is not limited to the following, but in the embodiment containing the (A1) component and the (A2) component having different contents of the carboxy group-containing monomer, the dissolved or swollen (A2) component is the above (A1 ), it is considered that the crosslinked structure of the film becomes partially dense when crosslinked with the crosslinking agent (B), which will be described later. This makes it possible to improve the whitening resistance without impairing the physical properties of the film such as the conformability to the substrate imparted by the component (A1).

The pH of the emulsion solution before neutralization of the component (A2) is preferably less than 7 (more preferably 6 or less, more preferably 1 to 4), and by mixing with the component (A1), dissolution or It swells and the above effect can be obtained. The average particle size of the acrylic resin of the component (A2) is a measured value before being dissolved or swollen by alkali (neutralization).

The content of the component (A2) is 45 wt% or less (more preferably 0.01 to 40 wt%, preferably 0.02 ~20% by weight, more preferably 0.05 to 10% by weight). The above component (A2) is a binder component that acts auxiliary to the above component (A1). When the above range is satisfied, it is advantageous for whitening resistance, and whitening resistance is achieved by crosslinking of the component (B) described later. can be further enhanced.

In the present invention, a carbodiimide compound is included as the cross-linking agent (B), and the carbodiimide compound is added in an amount of 0.1 to 10 parts by weight (preferably 0.1 to 10 parts by weight in terms of solid content) per 100 parts by weight of the solid content of the resin component (A). 2 to 5 parts by weight). In such a case, the cross-linking reaction with the resin component (A) (the (A1) component and the (A2) component) can prevent wet coloration (hereinafter also referred to as “wet color prevention property”). At the same time, it is possible to form a coating excellent in whitening resistance and the like.

Examples of such carbodiimide compounds include carbodiimide group-containing resins, N,N-dicyclohexylcarbodiimide, and N,N-diisopropylcarbodiimide. Examples of the carbodiimide group-containing resin include those described in JP-A-10-60272, JP-A-10-316930, JP-A-11-60667, WO2017/006950, and the like. The form of the carbodiimide compound is preferably water-soluble or water-dispersible, and the water-dispersible form is particularly advantageous in terms of storage stability.

The carbodiimide equivalent of the carbodiimide compound is preferably 100-500 (more preferably 150-400). Within such a range, the effect of the present invention can be sufficiently obtained.

In the present invention, in addition to the above components, it is preferable to include a basic organic compound (C) (hereinafter also referred to as “component (C)”). Component (C) includes, for example, alkylamines [e.g., monomethylamine, dimethylamine, trimethylamine, monoethylamine, triethylamine, monoisopropylamine, diisopropylamine, butylamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, etc.], alcohol Amines (aminoalcohols) [e.g., monoethanolamine, methylethanolamine, ethylethanolamine, mono-n-butylethanolamine, aminoethylpropanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, dimethylethanolamine, 2-aminomethylpropanol, etc.], heterocycle-containing amines [eg, morpholine, methylmorpholine, piperazine, hydroxyethylpiperazine, etc.]. These can be used singly or in combination of two or more. The component (C) may be added as a neutralizing agent during the production of the component (A). In the present invention, alcoholamines (aminoalcohols) are preferred, and 2-aminomethylpropanol, diethanolamine, monoethanolamine and the like are particularly preferred.

The boiling point of the organic amine compound is preferably 80° C. or higher (more preferably 100° C. or higher, more preferably 150° C. or higher). When the above range is satisfied, the rate of volatilization during film formation becomes moderate, so a film with excellent whitening resistance can be formed.

By containing the component (C), a dense coating can be formed. Although this action mechanism is not limited to the following, the cross-linking reaction of the carbodiimide compound (B) tends to speed up as the pH decreases. On the other hand, when a basic organic compound is added, its volatilization rate is moderate, so the cross-linking reaction (curing rate) due to a rapid decrease in pH is suppressed. A cross-linking reaction occurs. As a result, a dense coating can be formed, and whitening resistance can be further improved.

The content of component (C) is 0.01 to 5 parts by weight (0.02 to 3 parts by weight) per 100 parts by weight of the solid content of component (A). In the case of such a range, the above effects can be sufficiently exhibited.

The coating material of the present invention can be produced by uniformly mixing the above components by a known method, but if necessary, other components that are commonly used in coating materials can also be mixed. Examples of such components include coloring pigments, extender pigments, fibers, film-forming aids, thickeners, leveling agents, coupling agents, plasticizers, antifreeze agents, pH adjusters, preservatives, and antifungal agents. , anti-algae agents, antibacterial agents, dispersants, antifoaming agents, ultraviolet absorbers, light stabilizers, antioxidants, water, and the like.

The coating material of the present invention is a water-based clear coating material that forms a transparent coating, that is, a coating that transmits visible light. As a result, it is possible to form a laminated film having transparency, and to obtain a finish that takes advantage of the design of the base. The transparency may be such that the color and pattern of the base can be visually recognized, and the coating may be either colorless and transparent, or colored and transparent. (including split gloss etc.). A colored transparent film can be formed from a coating material containing, for example, a coloring pigment, a dye, or the like. A matte coating can be formed by a coating material containing, for example, an extender, a matting agent, or the like.

The degree of visible light transmission can be indicated by visible light transmittance. Visible light transmittance is preferably 30% or more, more preferably 35 to 100%, still more preferably 40 to 95%. The visible light transmittance is a value obtained by measuring the transmittance of light with a wavelength of 580 nm for a film with a thickness of 30 μm using a spectrophotometer (transmittance is 100% when there is no film (air)). be.

In order to obtain such visible light transmittance, for example, the coloring pigment ratio in the covering material should be set low. The coloring pigment ratio in the coating material is preferably 10% by weight or less, more preferably 5% by weight or less, and still more preferably 0 to 3% by weight. Embodiments in which the coating material does not contain a coloring pigment are also suitable.

In applying the water-based clear coating material of the present invention, a known coating tool can be used. Examples of coating tools that can be used include sprays, rollers, and brushes. The coating amount of the aqueous clear coating material is preferably 0.05-0.8 kg/m ² (more preferably 0.08-0.5 kg/m ² ). The number of times the water-based clear coating material is recoated is preferably 1 to 3 times. At the time of coating, the water-based clear coating material can be diluted as needed. Drying after application of the water-based clear coating material may be carried out at room temperature (preferably 0 to 50°C, more preferably 5 to 45°C), and heating can be performed if necessary.

<Laminate coating>
The laminated coating of the present invention is formed by coating the above inorganic material with a permeable water absorption inhibitor and undercoat material, if necessary, and then coating with the above aqueous clear coating material. In the present invention, by coating the inorganic material with the water-based clear coating material, whitening resistance and the like are enhanced, and the texture (design) of the inorganic material can be maintained for a long period of time. Furthermore, in the present invention, the texture (design property) of the inorganic material can be maintained for a long period of time, and the occurrence of wet color can be effectively prevented.

Examples are shown below to further clarify the features of the present invention.

・Manufacturing of water-based clear coating materials
Based on the formulation shown in Table 1, each raw material was mixed by a conventional method to produce a water-based clear coating material.
In addition, each component used the following.

(A) Resin component Resin 1: Acrylic resin emulsion (cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, emulsion polymer of acrylic acid, content of carboxy group-containing monomer: 0.5% by weight, average particle size: 120 nm , solid content: 50% by weight, medium: water, pH = 8.5)
・Resin 2: Acrylic resin emulsion (emulsion polymer of cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid, γ-methacryloyloxypropyltrimethoxysilane, content of carboxy group-containing monomer: 0.5% by weight, average Particle diameter: 120 nm, solid content: 50% by weight, medium: water, pH = 8.5)
Resin 3: Acrylic resin emulsion (emulsion polymer of cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid, γ-methacryloyloxypropyltrimethoxysilane, content of carboxy group-containing monomer: 0.1% by weight, average Particle diameter: 120 nm, solid content: 50% by weight, medium: water, pH = 8.5)
・ Resin 4: Acrylic resin emulsion (emulsion polymer of cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid, γ-methacryloyloxypropyltrimethoxysilane, content of carboxy group-containing monomer: 1.5% by weight, average Particle diameter: 120 nm, solid content: 50% by weight, medium: water, pH = 8.5)
・ Resin 5: Acrylic resin emulsion (emulsion polymer of cyclohexyl methacrylate, 2-ethylhexyl acrylate and methyl methacrylate, content of carboxy group-containing monomer: 0% by weight, average particle size: 120 nm, solid content: 50% by weight, medium: water, pH=8.5)
・ Resin 6: Acrylic resin emulsion (cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, emulsion polymer of acrylic acid, content of carboxy group-containing monomer: 6% by weight, average particle size: 120 nm, solid content: 50% by weight , medium: water, pH = 8.5)
Resin 7: Alkali-swellable acrylic resin emulsion (emulsion polymer of ethyl acrylate, ethyl methacrylate, methacrylic acid, content of carboxy group-containing monomer: 30% by weight, average particle size: 80 nm, solid content: 30% by weight, medium : water, pH = 3.0)

(B) Crosslinking Agent/Crosslinking Agent 1: Carbodiimide resin aqueous dispersion (solid content: 40% by weight, carbodiimide equivalent: 310)
· Cross-linking agent 2: carbodiimide resin aqueous dispersion (solid content: 40% by weight, carbodiimide equivalent: 230)
· Crosslinking agent 3: carbodiimide resin aqueous solution (solid content: 40% by weight, carbodiimide equivalent: 335)
· Crosslinking agent 4: carbodiimide resin aqueous dispersion (solid content: 40% by weight, carbodiimide equivalent: 450)
(C) basic organic compound/basic organic compound 1: 2-aminomethylpropanol (boiling point: 165°C)
・ Basic organic compound 2: 25% ammonia water (boiling point: 100 ° C.)
(others)
・Matting agent: acrylic bead powder (average particle size: 10 μm)
・Additives (urethane associative thickeners, defoaming agents, UV absorbers, etc.)
・Media: Water, hydrophilic solvent

(Examples 1 to 16, Comparative Examples 1 to 3)
A base material (slate plate: 45 x 30 cm) is spray-coated with a water-based clear coating material using a spray gun at a coating amount of 0.3 kg/m ² , dried and cured at 23°C for 24 hours. I] was formed. The following whitening resistance evaluation was performed on the produced test specimen [I]. Results are shown in Table 2.

<Evaluation 1>
Specimen [I] was immersed in water (23° C.) for 7 days, and the presence or absence of whitening immediately after pulling out was confirmed. As the evaluation criteria (whitening resistance), a four-grade evaluation (excellent: A>B>C>D: inferior) was performed, with "A" indicating no whitening and "D" indicating whitening of the whole. .
In addition, the wet color of each test piece was visually confirmed. As the evaluation criteria (wet color prevention property), a four-level evaluation (excellent: A > B > C > where "A" is not observed when wet color is observed and "D" is when wet color is observed throughout) D: Poor).

<Evaluation 2>
The specimen [I] was immersed in water (23° C.) for 7 days, pulled out, dried for 24 hours (23° C.), and checked for whitening and wet color. The evaluation criteria are the same as those for whitening resistance evaluation 1.

In Examples 1 to 16, sufficient whitening resistance and wet color resistance could be obtained. In particular, in Examples 7 to 13, both evaluations 1 and 2 were "A" evaluations.

Next, for Examples 1 to 16, film physical property evaluation (stain resistance evaluation) was performed. Results are shown in Table 2.
<Stain resistance evaluation 1>
A contaminant (15% by weight carbon aqueous solution) is spotted on the film surface of the test sample [I], dried for 24 hours (23 ° C.), washed with water for 10 minutes on the surface, and then washed for 6 hours (23 ° C.). After drying, the staining condition was evaluated. As the evaluation criteria (evaluation of stain resistance), "AA" indicates that there is no surface contamination and maintains excellent aesthetics, and "AA" indicates that there is almost no surface contamination and maintains excellent aesthetics. A five-level evaluation (excellent: AA>A>B>C>D: inferior) was given with "A" and "D" when surface contamination was observed.

<Stain resistance evaluation 2>
The specimen after the above evaluation 2 was used as the specimen [II], and the stain resistance was evaluated. The evaluation method and evaluation criteria are the same as those of the contamination resistance evaluation 1.

<Stain resistance evaluation 3>
Specimen [III] was formed in the same manner as Specimen [I] except that an aqueous clear coating material stored at 50° C. for 30 days was used, and stain resistance evaluation was performed. The evaluation method and evaluation criteria are the same as those of the contamination resistance evaluation 1.

In Examples 1 to 15, sufficient stain resistance could be obtained, and the physical properties of the coating could be maintained even after being immersed in water. Further, in Examples 1 to 12 and 14, the film physical properties could be sufficiently maintained even after storage of the aqueous coating material.

(Examples 17-18)
A base material (slate plate: 45 x 30 cm) was spray-coated with an aqueous emulsion-type permeable water-absorbing inhibitor containing hexyltriethoxysilane as a main component at a coating amount of 0.2 kg/m ² . dried for an hour. Then, the water-based clear coating material was spray-coated with a spray gun at a coating amount of 0.3 kg/m ² , dried and cured at 23°C for 24 hours to form a test specimen. The same evaluations 1 to 3 as in Example 1 were performed on the obtained specimens. Results are shown in Table 2.

(Examples 19-20)
A base material (slate plate: 45×30 cm) was spray-coated with a silicone-modified acrylic resin emulsion-based undercoat material at a coating amount of 0.1 kg/m ² and dried at 23° C. for 24 hours. Then, the water-based clear coating material was spray-coated with a spray gun at a coating amount of 0.3 kg/m ² , dried and cured at 23°C for 24 hours to form a test specimen. The same evaluations 1 to 3 as in Example 1 were performed on the obtained specimens. Results are shown in Table 2.

Also in Examples 17 to 20, excellent whitening resistance, wet color resistance and stain resistance could be obtained.

<Evaluation 4>
(Examples 1 to 16)
<Preparation of test sample [IV]>
Two slate plates (45 x 30 cm) are placed side by side, and the connecting part (width 20 mm) between the plates is filled with a modified silicone sealant (resin component: alkoxysilyl group-containing polyether polymer). material.
A water-based clear coating material was spray-coated on the entire surface of the base material with a spray gun at a coating amount of 0.1 kg/m ² and dried for 3 days (5 ° C., humidity 30%). ].
<Follow-up evaluation>
With respect to the prepared test specimen [IV], the appearance of the film was confirmed, and the state of occurrence of defects (swelling, peeling, cracking, etc.) was evaluated. The evaluation was made into a four-grade evaluation (excellent: A>B>C>D: poor), with "A" indicating that no problem occurred and "D" indicating that a problem clearly occurred. Results are shown in Table 2.

(Examples 17-18)
On a slate plate (45 x 30 cm), a water-based emulsion-type permeable water-absorbing inhibitor containing hexyltriethoxysilane as a main component was spray-coated at a coating amount of 0.2 kg/ ^m2 , and dried at 23°C for 24 hours. A test sample [IV] was prepared in the same manner as above, and the same evaluation 4 as in Example 1 was carried out, except that the same material was used. Results are shown in Table 2.

(Examples 19-20)
A slate plate (45 x 30 cm) was spray coated with a silicon-modified acrylic resin emulsion-based undercoat material at a coating amount of 0.1 kg/m ² , and dried at 23°C for 24 hours. A test sample [IV] was prepared as described above, and the same evaluation 4 as in Example 1 was performed. Results are shown in Table 2.

Claims (5)

A film forming method for applying a water-based clear coating material to the surface of an inorganic material,
The water-based clear coating material contains a resin component (A) and a cross-linking agent (B),
The resin component (A) contains an acrylic resin (A1) in which the content of the carboxy group-containing monomer in the resin component is 5% by weight or less,
The cross-linking agent (B) is a carbodiimide compound,
A method for forming a film, wherein the resin component (A) contains 0.1 to 10 parts by weight of a carbodiimide compound in terms of solid content with respect to 100 parts by weight of the solid content of the resin component (A). The resin component (A) includes an acrylic resin (A1) in which the content of the carboxy group-containing monomer in the resin component is 5% by weight or less, and the acrylic resin in which the content of the carboxy group-containing monomer in the resin component is the acrylic resin 2. The method of forming a film according to claim 1, wherein the acrylic resin (A2) is more than (A1). 3. The method of forming a film according to claim 1, wherein the solid content of the resin component (A) contains 55% by weight or more of the acrylic resin (A1) in terms of solid content. 3. The method of forming a film according to claim 1, further comprising an organic amine compound as the basic organic compound (C). A laminated film formed by the film forming method according to claim 1 or 2.