JP2024044512A - Film formation method - Google Patents

Abstract

[Problem] To provide a method for forming a coating that can suppress deterioration of an existing coating while making use of the uneven pattern and color pattern of an existing wall surface and maintain aesthetics for a long period of time. [Solution] The present invention is a method for forming a coating in which a topcoat material is applied to an existing wall surface that has deteriorated over time, the existing wall surface having an uneven pattern on its surface and an existing coating, the topcoat material containing a non-aqueous solvent and a resin component, the resin component containing a polyol compound (A) and a polyisocyanate compound (B), the polyisocyanate compound (B) containing a polyisocyanate compound (b1) having an isocyanate group content of less than 14% by weight and a polyisocyanate compound (b2) having an isocyanate group content of 14% by weight or more, the topcoat material being characterized in that it has visible light transparency and forms a coating with an ultraviolet light transmittance of 30% or less. [Selected Figure] None

Description

The present invention relates to a coating formation method that can be applied to buildings, etc.

Conventionally, on the walls of exterior buildings, coatings have been formed on various base materials using various coating materials for the purpose of protecting the base materials, improving their aesthetic appearance, and the like. From the viewpoint of aesthetics, etc., such wall surfaces are often provided with uneven patterns or colored patterns. However, since such wall surfaces (existing wall surfaces) are exposed outdoors for a long period of time, their deterioration progresses due to the effects of sunlight, rainfall, etc., and their original aesthetic appearance deteriorates over time.

In response to this, in recent years there has been a movement to repaint existing wall surfaces to improve aesthetics and extend the lifespan of the base material. For example, Patent Document 1 describes a method in which a degraded portion on the surface of a painted layer of a ceramic exterior wall material is polished and then a transparent coating agent is applied as a top coat material.

JP 2001-227138 A

However, even if an existing wall surface with an uneven pattern is repainted using the method described in the above-mentioned patent document, adhesion and conformability cannot be obtained, and deterioration of the existing coating cannot be sufficiently suppressed. In some cases, it may be difficult to obtain the effect of repainting.

The present invention was developed in view of these problems, and makes use of the uneven patterns and color patterns of the existing wall surface, while suppressing deterioration of the existing coating through its excellent adhesion and followability, and maintaining its aesthetic appearance over a long period of time. An object of the present invention is to provide a method for forming a film that can perform the following steps.

In order to solve these problems, the inventors of the present invention have conducted intensive studies and have come up with a method of forming a film by applying a specific top coating material to an existing wall surface having an uneven pattern, and has developed the present invention. I ended up completing it.

That is, the present invention has the following features.
1. A coating method for applying a topcoat material to an existing wall surface that has deteriorated over time,
The existing wall surface has an uneven pattern on its surface and is provided with an existing coating,
The topcoat material contains a non-aqueous solvent and a resin component,
The resin component contains a polyol compound (A) and a polyisocyanate compound (B),
The polyisocyanate compound (B) includes a polyisocyanate compound (b1) having an isocyanate group content of less than 14% by weight and a polyisocyanate compound (b2) having an isocyanate group content of 14% by weight or more,
The above-mentioned topcoat material is a coating film having visible light transmittance and an ultraviolet light transmittance of 30% or less, characterized by the coating film forming method.
2. The method for forming a coating film according to 1., wherein the polyisocyanate compound (B) contains 20 to 90% by weight of the polyisocyanate compound (b1).

In the present invention, by using a new coating formed from a specific topcoat material, it is possible to obtain a finish that takes advantage of the uneven pattern and color pattern of the existing wall surface. Further, in the present invention, since the newly installed coating has excellent adhesion and conformability to the existing wall surface, deterioration of the existing coating is sufficiently suppressed, and the aesthetic appearance can be maintained for a long period of time.

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

The present invention can be applied to existing wall surfaces of buildings, civil engineering structures, etc. Such existing wall surfaces are composed of at least a base material and an existing coating. Examples of base materials include concrete, mortar, metal, wood, glass, etc., or various plate-shaped wall materials. Among these, examples of plate-shaped wall materials include inorganic hardened bodies mainly composed of cement, calcium silicate, lime, gypsum, etc. Specific examples of such plate-shaped wall materials include cement boards, extrusion molding boards, slate boards, PC boards, ALC boards, fiber-reinforced cement boards, siding boards, ceramic boards, calcium silicate boards, gypsum boards, hard wood chip cement boards, etc.

In the present invention, the existing wall surface is one having a concave-convex pattern on its surface. Various concave-convex patterns on existing wall surfaces can be used, such as tile patterns, brick patterns, geometric patterns, stripes, lattice patterns, polka dot patterns, sand wall patterns, citron skin patterns, ripple patterns, and other patterns that are designed with animals and plants. Specifically, the shape of the convex parts when the concave-convex pattern is viewed from the front can be, for example, a square, a rectangle, a circle, an oval, a triangle, a diamond, a polygon, or an indefinite shape. In addition, the cross-sectional shape of the convex parts in the concave-convex pattern can be, for example, a trapezoid, a square, a rectangle, a semicircle, a wave shape, a step shape, a triangle, a mountain shape, and other shapes. Concave parts in the concave-convex pattern can be, for example, flat and form joints. The height difference between the concave parts and the convex parts can be constant or different in each area, but is preferably 20 mm or less, and more preferably about 1 to 15 mm. Such a concave-convex pattern may be applied to either one or both of the substrate and the existing coating.

In the present invention, an existing wall surface has an existing coating on the surface of the substrate, and the existing wall surface can have various colors (single color or multi-color patterns). The existing coating is a coating that has already been applied to the substrate by on-site painting or factory painting (line painting), and examples thereof include at least one type of coating selected from organic coatings, inorganic coatings, and organic-inorganic composite coatings. Examples of the existing coating include colored coatings (enamel coatings, printed coatings, etc.), clear coatings, and laminated coatings thereof, and are coatings formed by applying and curing various coating materials to the substrate. Such coating materials may be, for example, any of room temperature drying type, room temperature curing type, bake curing type, ultraviolet (UV) curing type, and electron beam curing type.

Binding materials for such coating materials include, for example, organic binding materials such as acrylic resin, polyurethane resin, epoxy resin, fluorine resin, alkyd resin, and polyester resin, or silicone resin, alkoxysilane, colloidal silica, and silicate. Examples include inorganic binders, organic-inorganic composite binders such as acrylic silicone resins, and the like.

In particular, the present invention provides that the existing coating on the outermost surface is an inorganic coating (a coating containing the above-mentioned inorganic binder), an organic-inorganic composite coating (a coating containing the above-mentioned organic-inorganic composite binder), or a fluororesin coating (a coating containing the above-mentioned fluororesin). It is preferable to use one or more types selected from the following, and furthermore, it can be suitably applied to these clear coatings.

The present invention can be applied as a renovation method when an existing wall surface as described above has deteriorated over time. Although the degree of deterioration over time is not particularly limited, wall surfaces that have been used for approximately 5 years or more (even 8 years or more) can be subject to the present invention.

Preferably, the existing wall surface of the present invention is constructed by arranging a plurality of plate-shaped wall materials that have an uneven pattern on the surface and are provided with an existing coating. The present invention can provide advantageous effects when applied to an existing wall surface composed of such a plurality of plate-shaped wall materials. It is desirable that the uneven pattern be applied at least to the plate-like wall material itself.
A sealing material or a dry joint material may be filled in the joints between the plate-shaped wall materials. In this case, the plurality of plate-shaped wall materials are installed side by side via connecting portions, and the connecting portions are provided between the plate-shaped wall materials. The width of the connecting portion is preferably about 3 to 20 mm (more preferably 5 to 15 mm). This joint is filled with a sealant or dry joint material.

In the present invention, an advantageous effect can be obtained when the existing wall surface is one in which a sealing material is filled in the joints between plate-shaped wall materials. The sealing material may be one that has deteriorated over time like the plate-shaped wall material, or it may be one that is newly placed before the top coat is applied.

As the sealant, a commonly used one can be used, for example, a silicone-based sealant, a modified silicone-based sealant, a polysulfide-based sealant, a modified polysulfide-based sealant, an acrylic urethane-based sealant, a polyurethane-based sealant, an SBR-based sealant, a butyl rubber-based sealant, etc.
The method for filling the sealant is not particularly limited, and for example, a known method using a gun or spatula can be used.

Before filling with the sealant, processing such as filling with a back-up material or applying a primer may be carried out in advance. For example, a foamed polyethylene-based back-up material can be used as the back-up material. For example, a synthetic rubber-based primer, an acrylic-based primer, a urethane-based primer, an epoxy-based primer, a silicone resin-based primer, a silane-based primer, etc. can be used as the primer.

The film forming method of the present invention is to apply (paint) a top coat material to an existing wall surface that has deteriorated over time as described above. The top coating material in the present invention includes a non-aqueous solvent and a resin component, of which the resin component includes a specific compound, the formed film has visible light transmittance, and ultraviolet transmittance, etc. is within a specific range. It is characterized by:

In the present invention, by using such a topcoat material, it is possible to obtain a finish that makes use of the uneven pattern and color pattern on an existing wall surface that has an uneven pattern and is equipped with an existing coating, and further, it is possible to form a new coating that has excellent adhesion and followability to the existing wall surface, sufficiently suppressing the deterioration of the existing coating and contributing to maintaining long-term aesthetics. In the present invention, such a new coating can also be used to extend the life of the existing wall surface. Although the mechanism of action by which such effects are achieved is not limited to the following, it is presumed that the topcoat material in the present invention can form a thin and transparent coating evenly along the unevenness of the existing wall surface, and by the action of the non-aqueous solvent and resin component, etc., it is possible to express excellent adhesion and followability to the existing coating, and that the adhesion and followability are maintained for a long period of time. In the present invention, such a new coating can increase resistance to sunlight and water, suppress deterioration of the existing coating, and maintain long-term aesthetics.

In addition, on existing walls with an uneven pattern and an existing coating, the way sunlight hits them, the way water flows, and the degree of retention will differ depending on the uneven shape, etc. Therefore, with conventional technology, even after the topcoat is applied, deterioration progresses in areas that are heavily exposed to sunlight and water, and there is a risk of localized discoloration, cracking, etc. In contrast, in the present invention, a new coating formed from the specific topcoat material described above is formed over the entire surface of an existing wall with an uneven pattern and exhibits sufficient resistance to sunlight and water, making it possible to suppress deterioration of the existing coating and is thought to have the effect of maintaining long-term aesthetics, etc.

Examples of the non-aqueous solvent in the top coating material include aliphatic hydrocarbon solvents such as n-heptane, n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane. , alicyclic hydrocarbon solvents such as methylcyclohexane and ethylcyclohexane, mixed solvents containing aliphatic hydrocarbons such as mineral spirits, petroleum solvents such as petroleum ether, petroleum naphtha, solvent naphtha, and kerosene, as well as isoparaffinic solvents, Examples include alcohol solvents, ether alcohol solvents, ether solvents, ester solvents, ether ester solvents, ketone solvents, and the like. These can be used alone or in combination of two or more.

The topcoat material in the present invention preferably contains a non-aqueous solvent with an aniline point of 12 to 70°C. It is believed that such a non-aqueous solvent contributes to improving adhesion by slightly swelling or dissolving the existing coating. As a non-aqueous solvent with an aniline point of 12 to 70°C, for example, one or more selected from aliphatic hydrocarbon-containing mixed solvents such as mineral spirits, petroleum solvents such as petroleum ether, petroleum naphtha, solvent naphtha, and kerosene are suitable. In the present invention, a more suitable embodiment contains a non-aqueous solvent with an aniline point of 30 to 65°C as the non-aqueous solvent, and an even more suitable embodiment contains 50 to 100% by weight of a non-aqueous solvent with an aniline point of 30 to 65°C in the non-aqueous solvent. The aniline point is a value measured by the method of JIS K2256. In the present invention, "α to β" is synonymous with "α or more and β or less".

The top coating material in the present invention contains a polyol compound (A) and a polyisocyanate compound (B) as resin components. Both of these components can be reacted and cured during film formation to form a polyurethane resin film.

Among these, examples of the polyol compound (A) (hereinafter also referred to as "component (A)") include polyether polyols, polyester polyols, acrylic polyols, fluorine-containing polyols, polyisoprene polyols, carbonate polyols, and the like. , one or more of these can be used.

In the present invention, it is preferable that component (A) contains one or more selected from acrylic polyols and fluorine-containing polyols.

As the acrylic polyol, one containing a (meth)acrylic acid alkyl ester, a hydroxyl group-containing monomer, and other monomers as necessary as constituent components, and polymerized these can be used.

Among these, (meth)acrylic acid alkyl ester is a compound having a (meth)acryloyl group and an alkyl group, and examples of the form of the alkyl group include linear, branched, and cyclic.

Examples of such (meth)acrylic acid alkyl esters include those having an alkyl group with 1 to 2 carbon atoms, such as methyl (meth)acrylate and ethyl (meth)acrylate, or n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, t-pentyl (meth)acrylate, 1-ethylpropyl (meth)acrylate, 2-methylbutyl (meth)acrylate, and p) 3-methylbutyl acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, 2-methylpentyl (meth)acrylate, 4-methylpentyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-lauryl (meth)acrylate, and the like having an alkyl group with 3 or more carbon atoms. These can be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylate esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. These can be used alone or in combination of two or more.

Examples of the other monomers include carboxyl group-containing monomers, amino group-containing monomers, pyridine-based monomers, nitrile group-containing monomers, amide group-containing monomers, epoxy group-containing monomers, carbonyl group-containing monomers, alkoxysilyl group-containing monomers, aromatic monomers, UV-absorbing group-containing monomers, and light-stable group-containing monomers. These can be used alone or in combination of two or more.

Fluorine-containing polyols are polyol compounds having fluorine atoms and hydroxyl groups. The use of fluorine-containing polyols can enhance resistance to sunlight and water, and is suitable for improving effects such as suppressing deterioration such as discoloration and cracking, and maintaining aesthetic appearance. Such fluorine-containing polyols can be obtained, for example, by copolymerizing fluorine-containing monomers such as fluoroolefins and fluoroalkyl group-containing acrylic monomers, hydroxyl group-containing monomers, and other monomers as necessary. Acrylic polyols having fluorine atoms are included in the fluorine-containing polyols.

Among these, examples of fluoroolefins include vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, 1,1,3,3,3-pentafluoropropylene, 2,2,3,3-tetra Fluoropropylene, 1,1,2-trifluoropropylene, 3,3,3-trifluoropropylene, chlorotrifluoroethylene, bromotrifluoroethylene, 1-chloro-1,2-difluoroethylene, 1,1-dichloro- Examples include 2,2-difluoroethylene. Examples of the fluoroalkyl group-containing acrylic monomer include perfluoromethyl (meth)acrylate, perfluoroisononylmethyl (meth)acrylate, and 2-perfluorooctylethyl (meth)acrylate. These can be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer in the fluorine-containing polyol include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, and hydroxypentyl vinyl ether; ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, and triethylene glycol monoallyl ether. and the like (meth)acrylic acid hydroxyalkyl esters as mentioned above. These can be used alone or in combination of two or more.

Examples of other monomers in the fluorine-containing polyol include (meth)acrylic acid alkyl esters, carboxyl group-containing monomers, amino group-containing monomers, pyridine monomers, nitrile group-containing monomers, amide group-containing monomers, epoxy group-containing monomers, carbonyl Examples include group-containing monomers, alkoxysilyl group-containing monomers, aromatic monomers, ultraviolet absorbing group-containing monomers, and photostable group-containing monomers. These can be used alone or in combination of two or more.

The (A) component may further contain a silicone component. For example, a silicone-containing acrylic polyol can be obtained by introducing a silicone component into an acrylic polyol. The (A) component may contain a silicone component, which can improve long-term weather resistance. The silicone component may be in the form of a chain, branched, cyclic, or the like. The content of the silicone component is preferably 0.1 to 20% by weight (more preferably 0.5 to 10% by weight) in terms of _SiO2 in the resin solids. In the above range, it is possible to obtain an improved effect on long-term weather resistance, and to ensure conformability and adhesion to existing wall surfaces.

In the present invention, the _SiO2 equivalent is expressed as the weight of silica ( _SiO2 ) that remains when a compound having an Si-O bond is completely hydrolyzed and then baked at 900°C. In general, alkoxysilanes, silicates, silicones, etc. react with water to undergo a hydrolysis reaction to become silanols, which have the property of undergoing further condensation reactions between silanols or between silanols and alkoxy. When this reaction is carried to the extreme, it becomes silica ( _SiO2 ). These reactions are as follows:
RO(Si(OR) _2O )nR+(n+1) _H2O → _nSiO2 +(2n+2)ROH (R represents an alkyl group, and n is an integer.)
The _SiO2 equivalent in the present invention is the amount of the remaining silica component calculated based on this reaction formula.

The method for introducing silicone into component (A) is not particularly limited and various methods can be used. For example,
(1) A method of copolymerizing a silicone compound having a polymerizable double bond,
(2) A method of reacting a functional group in a resin with a silicone compound having a functional group capable of reacting with the functional group;
(3) A method of reacting a resin copolymerized with a reactive silyl group-containing monomer with a reactive silyl group-containing compound;
(4) A method in which a functional group in a resin is reacted with a coupling agent having a functional group capable of reacting with the functional group, and then a reactive silyl group-containing compound is reacted therewith.

Combinations of functional groups in (2) and (4) above include hydroxyl group and isocyanate group, hydroxyl group and carboxylic acid anhydride group, amino group and isocyanate group, carboxyl group and epoxy group, amino group and epoxy group, and alkoxysilyl group. There are many examples.

The reactive silyl group in (3) and (4) above is one in which an alkoxyl group, a phenoxy group, a mercapto group, an amino group, a halogen, etc. are bonded to a silicon atom. As the reactive silyl group-containing compound, compounds having two or more reactive silyl groups in one molecule are used, such as tetrafunctional alkoxysilanes such as tetraethoxysilane, tetramethoxysilane, and tetrabutoxysilane; Methoxysilane, Methyltriethoxysilane, Methyltributoxysilane, Ethyltrimethoxysilane, Ethyltriethoxysilane, Ethyltributoxysilane, Propyltrimethoxysilane, Propyltriethoxysilane, Butyltrimethoxysilane, Butyltriethoxysilane, Phenyltrimethoxysilane Trifunctional alkoxysilanes such as methoxysilane, phenyltriethoxysilane, phenyltributoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, dipropyldimethoxysilane, dipropyl Difunctional alkoxysilanes such as diethoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldibutoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane; tetrachlorosilane, methyltrimethoxysilane; Chlorosilanes such as chlorosilane, ethyltrichlorosilane, propyltrichlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, dimethyldichlorosilane, diethyldichlorosilane, diphenyldichlorosilane, methylphenyldichlorosilane; tetraacetoxysilane, methyltriacetoxysilane, phenyltrichlorosilane Examples include acetoxysilanes such as acetoxysilane, dimethyldiacetoxysilane, and diphenyldiacetoxysilane, and one or more of these can be used. Moreover, a compound having one reactive silyl group in one molecule can also be used in combination.

The reactive silyl group-containing monomer in (3) above is a compound containing a reactive silyl group and a polymerizable double bond, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-butoxysilane, vinyltris (β-methoxyethoxy)silane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether, γ-(meth)acryloyloxypropyltrimethoxysilane, γ -(meth)acryloyloxypropyltriethoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, vinylmethyldimethoxysilane, methyldimethoxysilylethyl vinyl ether, methyldimethoxysilylpropyl vinyl ether, etc., and one or two of these More than one species can be used.

The coupling agent in (4) above is, for example, a compound having at least one alkoxysilyl group and other substituents in one molecule. Specific examples of the coupling agent include β-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N-( β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, isocyanate functional Examples include silane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and γ-methacryloxypropyltriethoxysilane, and one or more of these can be used.

The component (A) in the resin component of the present invention may be, for example, an embodiment containing only acrylic polyol, an embodiment containing only fluoropolyol, or an embodiment containing acrylic polyol and fluorine-containing polyol. Among these, an embodiment containing acrylic polyol and fluorine-containing polyol can further increase resistance to sunlight and water, and can ensure sufficient adhesion for a long period of time, which is preferable in terms of improving the effects of the present invention.

In the case of an embodiment containing an acrylic polyol and a fluorine-containing polyol as the component (A), the acrylic polyol is preferably contained in the component (A) in an amount of 30 to 99% by weight (more preferably 50 to 95% by weight) in terms of solid content. , more preferably 60 to 90% by weight, particularly preferably 65 to 85% by weight). In addition, in terms of solid content, the fluorine-containing polyol in component (A) is preferably 1 to 70% by weight (more preferably 5 to 50% by weight, even more preferably 10 to 40% by weight, particularly preferably 15 to 35% by weight). (% by weight) is desirable.

The hydroxyl value of component (A) is preferably 10 to 200 KOHmg/g (more preferably 15 to 100 KOHmg/g). The hydroxyl value is a value expressed as the number of milligrams of potassium hydroxide equivalent to the moles of hydroxyl groups contained in 1 g of resin solids.

At least one component of component (A) is preferably a resin having a weight average molecular weight of 3,000 to 150,000 (more preferably 5,000 to 120,000, still more preferably 8,000 to 95,000). In the present invention, when the component (A) having such a weight average molecular weight is contained, the top coat material can be easily applied evenly along the unevenness of the existing wall surface, which reduces deterioration of the existing coating and maintains the aesthetic appearance over a long period of time. It is suitable for Note that the weight average molecular weight is a value obtained by measurement using gel permeation chromatography.

It is desirable that at least one of component (A) is a non-aqueous dispersion type resin. The non-aqueous dispersion type resin is one that is dispersed as resin particles in the above-mentioned non-aqueous solvent, and has both a resin part that can be dissolved in the non-aqueous solvent and a resin part that is not soluble in the non-aqueous solvent. When a non-aqueous dispersion type resin is included as a polyol compound, the top coating material can be easily applied evenly along the unevenness of the existing wall surface, which is preferable in terms of suppressing deterioration of the existing coating and maintaining the aesthetic appearance over a long period of time.

In the present invention, it is desirable that at least the acrylic polyol is a non-aqueous dispersion type resin. When the acrylic polyol is a non-aqueous dispersion type resin, it is desirable that its weight average molecular weight is 10,000 to 150,000 (more preferably 40,000 to 120,000, still more preferably 55,000 to 95,000). When such conditions are satisfied, the above effects can be further enhanced.

Component (A) preferably has a glass transition point of -40 to 60°C (more preferably -20 to 55°C). When the glass transition point is above the above lower limit, it is suitable for suppressing contamination and maintaining aesthetic appearance, and when the glass transition point is below the above upper limit, it is suitable for preventing cracking of the film, conformability, maintaining aesthetic appearance, etc. It is suitable in this respect. Note that the glass transition temperature is a value determined by the Fox calculation formula.

The polyisocyanate compound (B) (hereinafter also referred to as "component (B)") has two or more isocyanate groups in one molecule and reacts with the component (A) to form a film. Component (B) is preferably one that can be cured by reaction with a polyol compound at room temperature. Note that the normal temperature here preferably indicates -10°C or more and 50°C or less (more preferably 5°C or more and 45°C or less).

Examples of component (B) include at least one diisocyanate selected from aliphatic and alicyclic diisocyanates, an alcohol component, and, if necessary, a polyol component, which are derivatized by alphanization, biuretization, dimerization (uretidione formation), trimerization (isocyanurate formation), adductization, carbodiimide formation, or the like, and mixtures thereof. These can be used alone or in combination of two or more.

Aliphatic diisocyanates are compounds that have saturated aliphatic groups in their molecules, such as 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (also known as hexamethylene diisocyanate (HDI)), 1,6-diisocyanato-2,2,4-trimethylhexane, and methyl 2,6-diisocyanatohexanoate (lysine diisocyanate). On the other hand, alicyclic diisocyanates are compounds that have cyclic aliphatic groups in their molecules, such as 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane. Of these, aliphatic diisocyanates (especially HDI) are the most preferred because they have excellent weather resistance and flexibility.

Examples of alcohol components include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, 2-pentanol, isoamyl alcohol, 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, trimethylcyclohexanol, etc. These can be used alone or in combination of two or more.

Examples of polyol components include polyether polyols, polyester polyols, polyolefin polyols, etc. In the present invention, polyether polyols such as polypropylene triol, polypropylene glycol, and polytetramethylene glycol are particularly suitable. These can be used alone or in combination of two or more.

In the present invention, as component (B), a polyisocyanate compound (b1) (hereinafter referred to as "(b1) component ) and a polyisocyanate compound (b2) (hereinafter referred to as " (b2) component").
In the present invention, the isocyanate group content is defined as the content (wt%) of isocyanate groups contained in the solid content of the polyisocyanate compound, and after neutralizing the isocyanate groups with an excess of amine, This value is determined by back titration.

In the present invention, by using the component (b1) and the component (b2) in combination, excellent effects can be exhibited in terms of adhesion to existing walls, followability, etc. This makes it possible to sufficiently exhibit resistance to water from the initial stage of film formation, and to continue to exhibit its effects over a long period of time. In addition, the combination of the above (b1) component and the above (b2) component has excellent followability to the existing wall surface, and is especially advantageous when the existing wall surface has a sealant. It can suppress blistering, cracking, peeling, etc. of the coating in the vicinity of the connecting portion, and contribute to maintaining the finish quality over a long period of time. Furthermore, excellent stain resistance can be exhibited.

In this case, component (B) preferably contains 20 to 90% by weight (more preferably 30 to 80% by weight, still more preferably 45 to 75% by weight) of the component (b1) in terms of solid content. is desirable. In addition, the component (B) preferably contains 10 to 80% by weight (more preferably 20 to 70% by weight, still more preferably 25 to 55% by weight) of the component (b2) in terms of solid content. desirable. The weight ratio [(b1)/(b2)] of the component (b1) and the component (b2) is preferably 0.5 or more (more preferably 0.6 to 8, even more preferably 0.7 to 8). 5, particularly preferably 1 to 3). In the case of such a range, the above effects can be further enhanced.

The mixing ratio of the polyisocyanate compound (B) may be set taking into consideration the equivalent ratio of the isocyanate groups of the polyisocyanate compound (B) to the hydroxyl groups of the polyol compound (A), i.e., the NCO/OH ratio. The NCO/OH ratio is preferably 0.8 to 2.0 (more preferably 1.0 to 1.8, and even more preferably 1.1 to 1.6). With such a ratio, the effects of the present invention can be further enhanced.

In the top coating material of the present invention, the solid content of the resin component (total of the above (A) component and the above (B) component) is preferably 25 to 75% by weight (more preferably 35 to 70% by weight) in the top coating material. It is. Due to the solid content of the resin component in the topcoat material (the weight ratio of the resin component in the topcoat material when based on the weight of the topcoat material at the time of painting), it is possible to follow the unevenness of the existing wall surface. It becomes easier to apply the topcoat material evenly, and while making use of the uneven pattern, it is possible to enhance the effect of forming a new coating that has excellent performance in suppressing deterioration of the existing coating and maintaining aesthetic appearance over a long period of time. Note that the solid content of the resin component is a value measured by the method of JIS K5601-1-2, the heating temperature is 105° C., and the heating time is 60 minutes.

In addition to the above components, the topcoat material of the present invention preferably contains a silicate compound (C) (hereinafter also referred to as "component (C)"). By including component (C), adhesion to existing wall surfaces and weather resistance can be further improved. Furthermore, since the formed coating can be made hydrophilic, it is also advantageous in terms of stain resistance.

As such component (C), tetraalkoxysilanes, condensates of tetraalkoxysilanes, and modified products thereof can be used. Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-t-butoxysilane, tetraphenoxysilane, monoethoxytrimethoxysilane, monobutoxytrimethoxysilane, monopentoxytrimethoxysilane, monohetoxytrimethoxysilane, dimethoxydiethoxysilane, and dimethoxydibutoxysilane. These can be used alone or in combination of two or more.

In the present invention, it is preferable to use a tetraalkoxysilane condensate (c1) (hereinafter referred to as "component (c1)") containing an alkoxyl group having 1 to 2 carbon atoms and an alkoxyl group having 3 to 12 carbon atoms. In particular, it is preferable that component (c1) is one in which 5% by weight to 50% by weight of the alkoxyl groups in the entire compound are alkoxyl groups having 3 to 12 carbon atoms.

Examples of the alkoxyl group having 3 or more and 12 or less carbon atoms include direct groups such as n-propoxy group, n-butoxy group, n-pentyloxy group, n-hexyloxy group, n-octyloxy group, and n-dodecyloxy group. Chain alkoxy group, isopropoxy group, isobutoxy group, t-butoxy group, sec-butoxy group, isopentyloxy group, neopentyloxy group, isohexyloxy group, 3-methylpentyloxy group, 1-methylhexyloxy group, Branched alkoxyl groups such as 1-ethylpentyloxy group, 2,3-dimethylbutoxy group, 1,5-dimethylhexyloxy group, 2-ethylhexyloxy group, 1-methylheptyloxy group, t-octyloxy group, etc. It will be done.

Such component (c1) can be produced by a known method. Examples of the method for producing component (c1) include a method in which a tetraalkoxysilane condensate having an alkoxyl group having 1 to 2 carbon atoms is modified with an alcohol having 3 to 12 carbon atoms.

The mixing ratio of component (C) is preferably 0.1 to 50 parts by weight (more preferably 0.5 to 30 parts by weight) per 100 parts by weight of the resin solid content of component (A). If component (C) is in this range, excellent adhesion improvement effects, stain resistance effects, etc. can be obtained.

In addition, the mixing ratio of the component (B) and the component (C) is such that the component (C) is preferably 5 to 80 parts by weight (more preferably 10 parts by weight) per 100 parts by weight of the solid content of the component (B). ~60 parts by weight). When component (C) is in this range, excellent adhesion improvement effects, stain resistance effects, etc. can be obtained.

The topcoat material in the present invention forms a coating that is transparent to visible light. This allows the formation of a transparent coating, making it possible to obtain a finish that makes use of the color of the existing coating surface (monochrome, multicolored pattern, etc.). This visible light transparency is sufficient as long as the existing coating surface can be visually recognized, and the coating may be either colorless and transparent or colored and transparent, and may be either glossy or matte (including 70% gloss, 50% gloss, 30% gloss, etc.). A colored and transparent coating can be formed, for example, by a topcoat material that contains a color pigment, a dye, etc. A matte coating can be formed, for example, by a topcoat material that contains an extender pigment, a matte agent, etc.

The degree of visible light transparency can be indicated by the visible light transmittance. The visible light transmittance is preferably 30% or more (more preferably 35-100%, and even more preferably 40-95%). The visible light transmittance is the value measured using a spectrophotometer to measure the transmittance of light with a wavelength of 580 nm for a coating with a thickness of 30 μm (transmittance without a coating (air) is considered to be 100%).

In order to obtain such visible light transmittance, for example, the proportion of colored pigment in the top coating material may be set low. The proportion of colored pigment in the top coat material is preferably 10% by weight or less (more preferably 5% by weight or less, even more preferably 0 to 3% by weight). An embodiment in which the top coat material does not contain a colored pigment is also suitable.

The topcoat material in the present invention forms a coating with an ultraviolet transmittance of 30% or less (preferably 20% or less, more preferably 0 to 15%). In the present invention, by having an ultraviolet transmittance within the above range, it is possible to increase resistance to sunlight, suppress deterioration such as discoloration and cracking, and maintain aesthetic appearance. The ultraviolet transmittance is the value measured using a spectrophotometer to measure the transmittance of light with a wavelength of 350 nm for a coating with a thickness of 30 μm (transmittance is 100% when there is no coating (air)).

As a means for obtaining such ultraviolet transmittance, for example,
(i) Use a topcoat material containing a resin component having ultraviolet absorbing groups.
(b) Use a topcoat material containing an ultraviolet absorber.
(c) Use a topcoat material containing ultraviolet-blocking powder.
These means may be employed alone or in combination.

In the above (a), for example, a compound containing an ultraviolet absorbing group-containing monomer in the resin constituent may be used as the resin component. In this case, the ratio of the ultraviolet absorbing group-containing monomer in the compound is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight.

Examples of the ultraviolet absorbers in (b) above (excluding compounds having polymerizable unsaturated double bonds) include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, triazine ultraviolet absorbers, and salicylate ultraviolet absorbers. UV absorbers, cyanoacrylate-based UV absorbers, benzoate-based UV absorbers, malonic acid ester-based UV absorbers, oxalic acid anilide-based UV absorbers, and the like. Among these, examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and 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'-dihydroxy-4,4'dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4- Examples include methoxy-2'-carboxybenzophenone and 2-hydroxy-4-stearyloxybenzophenone. Examples of benzotriazole ultraviolet absorbers include 2-(2-hydroxy-5-t-butylphenyl)-2H-benzotriazole, 3-(2H-benzotriazol-2-yl)-5-(1,1 -dimethylethyl)-4-hydroxyalkyl ester, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazol-2-yl) -yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, methyl 3-(3-(2H-benzotriazol-2-yl) Examples include reaction products of -5-t-butyl-4-hydroxyphenyl)propionate and polyethylene glycol. Examples of triazine-based ultraviolet absorbers include 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl derivatives, 2-(2 ,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester reaction product, 2,4-bis' Examples include 2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3-5-triazine.These can be used alone or in combination of two or more.Ultraviolet absorber The mixing ratio is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the solid content of the resin component.

As the ultraviolet shielding powder in (c) above, those having the ability to absorb and/or reflect ultraviolet rays can be used, such as alumina, zirconium oxide, barium sulfate, precipitated barium sulfate, calcium carbonate, magnesium carbonate, Aluminum hydroxide, magnesium hydroxide, titanium oxide, magnesium oxide, zinc oxide, boron nitride, bismuth oxychloride, zinc phosphate, mica, agarite, talc, diatomaceous earth, white clay, kaolin, clay, china clay, barite powder, silica sand, Examples include silica powder, white carbon, metal powder, and organic resin powder. These can be used alone or in combination of two or more. The average particle diameter of the ultraviolet shielding powder is preferably 1 to 200 nm. In the above (c), it is desirable to set the mixing ratio of the ultraviolet shielding powder within a range that can ensure visible light transmittance.

In addition to the above-mentioned components, the topcoat material of the present invention may contain known additives, such as aggregates, color particles, color pigments, extender pigments, dyes, matting agents, thickeners, wetting agents, dehydrating agents, leveling agents, plasticizers, fibers, antifreeze agents, film-forming agents, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, defoamers, light stabilizers, antioxidants, adhesion agents, anti-staining agents, hydrophilizing agents, water repellents, crosslinking agents, hardening accelerators, catalysts, solvents, etc., as necessary, within the range that does not significantly impair the effects of the present invention.

The topcoat material of the present invention can be manufactured by uniformly mixing the above-mentioned non-aqueous solvent, resin component, and, if necessary, the above-mentioned various components by a conventional method. The form of the topcoat material can be, for example, a one-component type, a two-component type, or a multi-component type having more than one component. A suitable example of the form of the topcoat material is, for example, a two-component type consisting of a base agent containing at least a polyol compound and a curing agent containing at least a polyisocyanate compound. When a silicate compound is included, it is preferable to mix it with the curing agent.

The top coating material in the present invention preferably forms a film having an elongation rate of 20% or more (more preferably 40% or more, still more preferably 50% or more, particularly preferably 60% or more). In the present invention, when the elongation rate is within the above range, resistance to water can be improved, and effects such as suppressing deterioration such as discoloration and cracking and maintaining aesthetic appearance can be further enhanced. The upper limit of the elongation rate is preferably 300% or less, more preferably 200% or less. When the upper limit of the elongation rate is within such a range, it is suitable in terms of stain resistance and the like.

In addition, the elongation rate in this invention is a value measured by the "standard elongation test" method of JIS A6909 "7.26 Elongation Test" (elongation rate at 23°C). However, the test piece used has a dry film thickness of 80 μm.

In the present invention, a new coating is formed by applying (painting) such a top coat material. The top coat material can be applied directly to the existing wall surface, but various pre-treatments can also be applied if necessary. Pretreatment includes, for example, removing existing coatings that have significantly deteriorated, removing contaminants by high-pressure water washing, repairing with putty, filler, etc., restoring surface shape, and the like. When applying a new sealant to an existing wall, it is desirable to apply a topcoat approximately 2 to 10 days after applying the sealant.

As the top coating material, one or more types of top coating materials that satisfy the above-mentioned conditions can be used. In the present invention, such top coat materials can also be applied over and over again. For example, one type of top coating material may be applied multiple times, or two or more types of top coating materials may be applied over each other. When recoating, appropriate intervals may be provided to allow the film to dry.

In applying the top coat material, known painting equipment can be used. As the painting tool, for example, a spray, a roller, a brush, etc. can be used. The top coat material can be diluted as necessary and then used for painting.

The coating amount when applying the top coat material is preferably 100 to 600 g/m ² , more preferably 150 to 500 g/m ² . By setting the lower limit of the coating amount of the topcoat material to the above value, the new coating will be sufficiently resistant to sunlight and water, suppressing deterioration such as discoloration and cracking caused by the existing coating surface, and maintaining a long-term aesthetic appearance. It is suitable in terms of maintaining sex and the like. By setting the upper limit of the coating amount of the top coat material to the above value, it is possible to obtain a finish that takes advantage of the uneven pattern etc. of the existing coating surface. In addition, when the top coat material is applied over and over again, it is desirable that the total amount of application is within the above range. The number of times the top coat material is applied is preferably 1 to 3 times.

The viscosity of the topcoat material during application is preferably 0.1 to 10 Pa·s, more preferably 0.2 to 5 Pa·s. By having the viscosity of the topcoat material within this range, the effects of the present invention can be stably obtained. Note that the viscosity referred to here is the value determined by measuring the viscosity at 20 rpm (the guideline value at the fourth revolution) using a BH type viscometer, and the measurement temperature is 23°C.

After the topcoat is applied, drying can be done at room temperature (preferably between -10°C and 50°C, more preferably between 5°C and 45°C), or it can be heated if necessary.

The film thickness of the new coating formed by such a top coat material (in the case of multiple coatings, the total film thickness after multiple coatings) is preferably 30 μm or more, more preferably 50 μm or more, still more preferably 60 μm or more, and particularly preferably is greater than 65 μm, most preferably greater than 70 μm. The upper limit of the thickness of the newly installed coating is not particularly limited, but is preferably 300 μm or less, more preferably 250 μm or less, and still more preferably 200 μm or less. In addition, the film thickness in this invention is a dry film thickness, and when 1 type or 2 or more types of top coating materials are overcoated, it is the total dry film thickness after overcoating.

The following examples will clarify the features of the present invention.

The raw materials used are shown below.
(A) Polyol Compound (A-1) Non-aqueous dispersion type acrylic polyol, hydroxyl value: 40 KOHmg/g, weight average molecular weight: 70,000, solid content: 50% by weight, medium: mineral spirits (aniline point: 42°C)
(A-2) Non-aqueous dispersion type silicone-containing acrylic polyol, hydroxyl value: 55 KOHmg/g, weight average molecular weight: 70,000, solid content: 50% by weight, medium: mineral spirits (aniline point 42°C)
(A-3) Fluorine-containing polyol solution, hydroxyl value: 33 KOH mg/g, solid content: 60% by weight, medium: mineral spirits (aniline point: 42° C.)
(B) Isocyanate compound (B-1) 1,6-diisocyanatohexane derivative, isocyanate group content: 12% by weight, solid content: 100% by weight
(B-2) 1,6-diisocyanatohexane derivative, isocyanate group content: 21% by weight, solid content: 100% by weight
(B-3) 1,6-diisocyanatohexane derivative, isocyanate group content: 17% by weight, solid content: 100% by weight
(B-4) 1,6-diisocyanatohexane derivative, isocyanate group content: 14.8% by weight, solid content: 100% by weight
In addition, (B-1) is the (b1) component, and (B-2) to (B-4) are the (b2) component.
(C) Silicate compound (C-1) i-butyl alcohol modified tetramethoxysilane compound (average condensation degree 4, ester exchange rate 30%, residual silica rate 40%)
Nonaqueous solvent A: Solvent naphtha (aniline point 13°C)
Non-aqueous solvent B: Mineral spirits (aniline point 42°C)
Additive A: UV absorbers, light stabilizers Additive B: Antifoamers, thickeners, etc.

(Top coating material 1)
- Production of main ingredient (A-1) 80 parts by weight of component, 12 parts by weight of non-aqueous solvent A, 3 parts by weight of additive A, and 5 parts by weight of additive B were mixed and stirred to produce main ingredient 1.
- Production of curing agent 6 parts by weight of component (B-1), 4 parts by weight of component (B-2), and 10 parts by weight of non-aqueous solvent B were mixed and stirred to produce curing agent 1.
- Preparation of top coat material Top coat material 1 was obtained by mixing base material 1 (100 parts by weight) and curing agent 1 (20 parts by weight) ([NCO]/[OH] = 1.3) and stirring.

(Topcoat materials 2 to 17)
The base material and hardener were prepared according to the formulations in Tables 1 and 2, and then mixed to obtain the topcoat material.

(Examples 1 to 12, Comparative Examples 1 to 5)
The following evaluations were carried out for each topcoat material. The results are shown in Tables 3 and 4.

Test I
The entire surface of a ceramic siding boat (having an inorganic clear coating as the outermost coating layer) was spray-painted with a topcoat material at a coating amount of 110 g/ ^m2 , dried for 6 hours, immersed in water for 1 hour, and the surface condition of the coating when pulled out was visually evaluated. The painting and curing processes were all performed under standard conditions (air temperature 23°C, relative humidity 50%). The evaluation was performed in three stages (excellent; A>B>C; poor), with "A" being the one where no abnormality was observed and "C" being the one where abnormalities such as gloss reduction and whitening were observed.

Test II
(Test specimen preparation)
As an existing wall surface, a gray ceramic siding boat deteriorated by outdoor exposure (having tile-like convex and concave portions (joints) on the surface, an irregular uneven pattern on the convex portions, and an inorganic clear coating as the outermost coating film) was prepared. A topcoat material was spray-painted on the entire surface of this existing wall surface at a coating amount of 110 g/ ^m2 , dried for 3 hours, spray-painted again at a coating amount of 110 g/ ^m2 , and dried and cured for 14 days to prepare a test specimen. All painting and curing processes were carried out under standard conditions (temperature 23°C, relative humidity 50%).

(Test II-1)
After 7 days of immersion in water for the test specimens produced by the above method, crosscuts were made in the coating at each part of the uneven pattern using a cutter knife, and a tape was attached to the crosscuts and peeled off to evaluate adhesion. Evaluation was performed on a four-grade scale (Excellent; AA>A>B>C; Poor), with "AA" indicating no peeling and "C" indicating a large amount of peeling.

(Test II-2)
The carbon dispersion (15%) was sprayed onto the test specimen prepared by the above method, dried (23°C, 1 day), and then washed with water. The remaining carbon on the surface of the test specimen was visually observed and rated on a three-level scale (A>B>C; poor), with "A" indicating slight remaining carbon and "C" indicating significant remaining carbon.

(Test II-3)
The test specimen prepared by the above method was exposed to an accelerated weathering tester (Metal Weather; manufactured by Daipra Wintes Co., Ltd.) for 1500 hours, and then the appearance of the specimen surface changed (glossy, color, lifting, peeling, etc.). The state of cracks) was observed. The evaluation is done by comparing the change in appearance with the test specimen before exposure, and grading it into four stages: "AA: No change,""C: Decreased gloss, discoloration, lifting, peeling, or cracking.">B>C; poor).

Test III (Joint followability)
The existing wall surfaces consisted of two pieces of gray ceramic siding boards (same as above) that had deteriorated due to exposure to the outdoors, and the joints between the boards (width 10 mm) were filled with a modified silicone-based sealant (resin component: alkoxysilyl group-containing polyether polymer, plasticizer content: less than 1% by weight) to serve as the substrate to be painted.
The entire surface of the substrate was spray-painted with a coating amount of 110 g/ ^m2 , dried for 3 hours, spray-painted again with a coating amount of 110 g/ ^m2 , and dried and cured for 14 days to prepare a test specimen. All painting and curing processes were performed under standard conditions (temperature 23 ° C, relative humidity 50%).

The specimens created using the above method were subjected to a total of 10 cycles of hot and cold cycling testing, with one cycle consisting of 18 hours of water immersion, 3 hours of rest at -20°C, and 3 hours of rest at 50°C. After that, the appearance of the coating at each part (connecting parts, plate parts) was checked and the occurrence of defects (blistering, peeling, cracks, etc.) was evaluated. The evaluation was done on a four-level scale (excellent: AA>A>B>C: poor), with "AA" indicating no defects and "C" indicating obvious defects.

Claims (2)

A coating method for applying a topcoat material to an existing wall surface that has deteriorated over time,
The existing wall surface has an uneven pattern on its surface and is provided with an existing coating,
The topcoat material contains a non-aqueous solvent and a resin component,
The resin component contains a polyol compound (A) and a polyisocyanate compound (B),
The polyisocyanate compound (B) includes a polyisocyanate compound (b1) having an isocyanate group content of less than 14% by weight and a polyisocyanate compound (b2) having an isocyanate group content of 14% by weight or more,
The above-mentioned topcoat material is a coating film having visible light transmittance and an ultraviolet light transmittance of 30% or less, characterized by the coating film forming method. The film forming method according to claim 1, wherein the polyisocyanate compound (B) contains 20 to 90% by weight of the polyisocyanate compound (b1).