JP7179498B2 - Coating method - Google Patents

Description

The present invention relates to a novel film forming method.

Conventionally, in the exterior of buildings and civil engineering structures, coatings are formed with various coating materials on various substrates for the purpose of protecting the substrates, imparting colors, and the like. In some cases, such a film surface is provided with an uneven pattern or a multicolored pattern from the viewpoint of aesthetics. However, such coated surfaces tend to deteriorate under the influence of sunlight, rainfall, etc. when exposed outdoors for a long period of time. Specifically, discoloration, cracks, and the like may be caused. Therefore, it becomes necessary to repaint the coating surface (existing coating surface) on which such deterioration has occurred.

On the other hand, in recent years, there is a movement to repaint the existing coated surface to improve the appearance and extend the life of the base material. For example, Patent Literature 1 describes a method of restoring the original color tone by polishing a deteriorated portion of the surface of a coating layer of a ceramic exterior wall material and then applying a transparent coating agent.

Japanese Unexamined Patent Application Publication No. 2001-227138

By the way, among the existing coating surfaces as described above, for those having an uneven pattern, the way sunlight hits, the way water flows, the degree of retention, etc. partially differ depending on the shape of the unevenness. Become. As a result, deterioration is likely to progress in areas where the load from sunlight or water is large, and there is a risk that discoloration, cracks, and the like may be caused locally. In addition, on the coating surface having a multicolor pattern, if the durability differs depending on the color tone, similar deterioration may occur in the color tone area where the durability is relatively insufficient.

For such an existing coating surface, even if repainting is performed by the method described in the above patent document, the progress of deterioration of the existing coating surface cannot be sufficiently suppressed, and the effect of repainting is obtained. may be difficult to obtain.

The present invention has been made in view of such problems, and while making use of the uneven pattern and multicolor pattern of the existing coating, it suppresses the progress of deterioration such as discoloration and cracking caused by the existing coating, and maintains the aesthetic appearance for a long time. It is an object of the present invention to provide a method of forming a film that can be maintained.

In order to solve such problems, the present inventors have made intensive studies, and as a result, have found a method of forming a coating by applying a specific coating material to an existing coating surface having an uneven pattern and/or a multicolored pattern. and came to complete the present invention.

That is, the present invention has the following features.
1. A coating forming method for forming a new coating by sequentially applying a first coating material and a second coating material to an existing coating surface provided on a base material,
The existing coating surface has an uneven pattern and / or a multicolor pattern,
Each of the first covering material and the second covering material is
Containing a resin component containing 20% by weight or more of a (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms in the resin component,
Forming a film having visible light transmittance and an ultraviolet transmittance of 30% or less,
The first coating material has a pigment volume concentration of 0% or more and less than 3%,
The pigment volume concentration of the second coating material is 3% or more and 50% or less,
The second coating material includes an extender pigment, and the extender pigment is a resin bead.
A film forming method characterized by:
2 . Each of the first covering material and the second covering material is
The (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms includes a (meth)acrylic acid alkyl ester (a1) having an alkyl main chain having 3 or more carbon atoms,
When r is the weight ratio of the component (a1) in the component (A),
1. The r(r ₁ ) of the resin component in the first coating material is larger than the r(r ₂ ) of the resin component in the second coating material. The film forming method according to .
3 . 1. The film thickness of the new film is 30 μm or more. or 2. The film forming method according to .

According to the film forming method of the present invention, it is possible to suppress the progress of deterioration such as discoloration and cracking caused by the existing film while making use of the uneven pattern and multicolor pattern of the existing film, and to maintain the aesthetic appearance for a long time. .

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

The present invention is a coating formation method for forming a new coating by applying a specific coating material to an existing coating surface (existing coating surface having an uneven pattern and/or multicolor pattern) provided on a substrate. be.

Even if such an existing coating surface is repainted with a conventional transparent coating agent, it is difficult to suppress the progress of discoloration, cracks, etc. in areas that are originally prone to deterioration. There is also a risk that fine cracks that have occurred on the surface will progress over time. Such cracks are likely to spread to the coating after repainting, and as a result, the appearance and water impermeability of the new coating are impaired, and it is difficult to obtain sufficient effects in terms of extending the life of the base material.

On the other hand, in the present invention, it is possible to suppress the progress of deterioration such as discoloration and cracking caused by the existing coating surface while making use of the uneven pattern and multicolor pattern of the existing coating surface, and to maintain the aesthetic appearance for a long time. , it is also possible to extend the life of the base material. It is considered that such an effect is exhibited because the new specific coating of the present invention imparts sufficient resistance to sunlight and water.

In the present invention, the existing coated surface provided on the substrate is to be coated. Examples of such existing coating surfaces include those formed on the surface of base materials such as buildings and civil engineering structures. ) are preferred. Examples of base materials include concrete, mortar, and plate-like base materials. Among these, plate-like substrates include, for example, cement boards, extruded boards, slate boards, PC boards, ALC boards, fiber-reinforced cement boards, metal siding boards, ceramic siding boards, ceramic boards, calcium silicate boards, Examples include plastic boards, hardwood cement boards, PVC extruded siding boards, and plywood. The present invention is particularly useful when the substrate is a plate-like substrate.

When the existing coating surface is composed of a plurality of plate-shaped substrates, the joints between the plate-shaped substrates may be filled with a joint material such as a sealing material or a dry joint material. Examples of the sealing material include silicone sealing material, modified silicone sealing material, polysulfide sealing material, modified polysulfide sealing material, acrylic urethane sealing material, polyurethane sealing material, SBR sealing material, and butyl rubber sealing material. materials.

The existing coating surface has a textured pattern and/or a multicolored pattern. Such existing coatings are formed from one or more coating agents. As the coating agent, various substances such as colored or non-colored, opaque or transparent can be used. and the like containing one or more resins selected from the above. The existing coating surface is a coating of one layer or two or more layers, and may be, for example, a laminate of a colored coating layer, a transparent coating layer, and the like.

Various uneven patterns can be mentioned, for example, a tile pattern, a brick pattern, a stone pattern, a rock pattern, a wood pattern, a geometric pattern, a striped pattern, a lattice pattern, a polka dot pattern, and a sand wall pattern. , citron skin pattern, ripple pattern, etc., as well as graphic patterns designed with animals and plants. Concretely, the shape of the convex portion when the concave-convex pattern is viewed from the front includes, for example, a square, rectangle, circle, ellipse, triangle, rhombus, polygon, irregular shape, and the like. Moreover, the cross-sectional shape of the projections in the uneven pattern includes, for example, trapezoid, square, rectangle, semicircle, wave, step, triangle, chevron, irregular shape, and the like. The recesses in the uneven pattern may be flat and form joints. The height difference between the concave portion and the convex portion may be constant or different at each site, but is preferably 20 mm or less, more preferably about 1 to 15 mm. Such an uneven pattern may be applied to one or both of the base material and the existing coating.

A multicolor pattern is a pattern in which at least two or more colors are mixed in a visible state, for example, a pattern in which two or more color spots are mixed, and spots (one color or two or more colors) are scattered on a background color. patterns, patterns that are painted in two or more colors (e.g., island pattern, linear pattern, tile pattern, brick pattern, stone pattern, rock pattern, wood pattern, geometric pattern, striped pattern pattern, grid pattern, random pattern, etc.). Such a multicolor pattern may be formed by various printing methods (inkjet printing, etc.), or may be formed by a decorative coating agent such as a stone-like finish coating material or multicolored pattern paint. may be

INDUSTRIAL APPLICABILITY The present invention can be preferably applied as a repainting method (refurbishment method) when the existing coated surface as described above has deteriorated over time. The degree of deterioration over time is not particularly limited, but wall surfaces that have been used for approximately 5 years or more (furthermore 8 years or more) are suitable as objects of the present invention. Before the new coating is formed, the surface of the existing coating can be cleaned or partially repaired, if necessary. If the existing coating surface has a joint material such as a sealing material, the existing joint material may be left as it is, but a new joint material can be cast before forming the new coating, or the existing joint It is also possible to apply a treatment such as coating to the surface of the material.

In the present invention, a new coating is formed by applying the first coating material and the second coating material to the existing coating surface as described above. Both the first coating material and the second coating material in the present invention include a (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms (hereinafter also referred to as "(A) component"), a resin It contains a resin component in an amount of 20% by weight or more in the constituent components. Both the first covering material and the second covering material form a film having visible light transmittance and an ultraviolet transmittance of 30% or less. Common matters of such a first covering material and a second covering material (hereinafter, both are collectively referred to simply as "covering material") will be described first.

The coating material in the present invention contains a resin component, and the resin component contains a (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms as a resin component. Such a resin component acts as a binder, and the component (A) can mainly impart resistance to water. In the present invention, both acrylic acid alkyl ester and methacrylic acid alkyl ester are collectively referred to as (meth)acrylic acid alkyl ester.

Examples of the form of the alkyl group in component (A) include linear, branched, and cyclic. Component (A) includes, for example, 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 , 3-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, 2-methylpentyl (meth)acrylate, (meth)acrylic acid 4-methylpentyl, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, (meth) ) n-decyl acrylate, n-undecyl (meth)acrylate, n-lauryl (meth)acrylate and the like. These can be used singly or in combination of two or more. Among these, as the component (A), those having an alkyl group with 4 or more carbon atoms (more preferably 4 or more and 8 or less) are suitable.

The proportion of component (A) in the resin component is 20% by weight or more, preferably 25-99% by weight, more preferably 30-98% by weight. If the component (A) is in the above ratio, it is possible to improve resistance to water, etc., and it is possible to obtain effects such as suppressing deterioration such as discoloration and cracking and maintaining aesthetic appearance. 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".

In the coating material of the present invention, a (meth)acrylic acid alkyl ester (a1) having an alkyl main chain having 3 or more carbon atoms (hereinafter also referred to as "(a1) component") is used as the (A) component in the resin constituents. preferably included. As such component (a1), the alkyl portion is a linear or branched alkyl group (excluding cyclic), and the main chain (longest straight carbon chain) has 3 or more carbon atoms. one can be used. If the resin component contains the component (a1), in addition to the resistance to water, the anti-cracking property can be further improved, and it is more preferable in terms of water impermeability, maintenance of aesthetic appearance, extension of base material life, and the like. .

Component (a1) has an alkyl main chain having 3 or more carbon atoms in the alkyl moiety. The alkyl portion of the component (a1) may have various side chains (eg, alkyl groups with fewer carbon atoms than the alkyl main chain) as long as it has such an alkyl main chain. As the component (a1), among the components (A) described above, those satisfying these conditions can be used. Examples include n-propyl (meth)acrylate, isobutyl (meth)acrylate, and (meth)acrylic acid. 1-ethylpropyl, t-pentyl (meth)acrylate, neopentyl (meth)acrylate, n-butyl (meth)acrylate, 2-methylbutyl (meth)acrylate, isopentyl (meth)acrylate, (meth)acrylic 3-methylbutyl acid, 2-ethylbutyl (meth)acrylate, n-pentyl (meth)acrylate, 2-methylpentyl (meth)acrylate, 4-methylpentyl (meth)acrylate, n-(meth)acrylate Hexyl, 2-ethylhexyl (meth)acrylate, n-heptyl (meth)acrylate, isooctyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, (meth)acrylic acid Examples include n-decyl, n-undecyl (meth)acrylate and n-lauryl (meth)acrylate. These can be used singly or in combination of two or more. Among these, as the component (a1), those having an alkyl main chain with 4 or more carbon atoms (more preferably 4 or more and 8 or less) in the alkyl moiety are suitable.

Examples of (A) components other than (a1) (hereinafter also referred to as "(a2) components") include isopropyl (meth)acrylate, t-butyl (meth)acrylate, and cyclohexyl (meth)acrylate. be done. These can be used singly or in combination of two or more.

The weight ratio of component (a1) in component (A) can be expressed as "r". This "r" is a value calculated by the following formula.
[Formula] r = {weight of component (a1) in resin component}/{weight of component (A) in resin component}

The resin component may contain monomers other than the component (A) (hereinafter also referred to as "component (B)"). Examples of component (B) include methyl (meth)acrylate, ethyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, carboxyl group-containing monomers, amino group-containing monomers, and pyridine-based monomers. , hydroxyl group-containing monomer, nitrile group-containing monomer, amide group-containing monomer, epoxy group-containing monomer, carbonyl group-containing monomer, alkoxysilyl group-containing monomer, fluorine-containing monomer, aromatic monomer, UV-absorbing group-containing monomer, photostable group Containing monomers, etc. are mentioned. These can be used singly or in combination of two or more. The composition ratio of component (B) is preferably 80% by weight or less (more preferably 1 to 75% by weight, more preferably 2 to 70% by weight) in the resin constituents. In addition, in this invention, a monomer is a compound which has a polymerizable unsaturated double bond.

In the present invention, an aspect in which the component (B) contains an ultraviolet-absorbing group-containing monomer and/or a photostable group-containing monomer is preferable in terms of improving the effect of the present invention. The UV-absorbing group-containing monomer is a compound having a UV-absorbing group and a polymerizable unsaturated double bond. triazine-based UV-absorbing groups, salicylate-based UV-absorbing groups, and the like. The photostable group-containing monomer is a compound having a photostable group and a polymerizable unsaturated double bond, and the photostable group includes, for example, a piperidyl group.

Such a resin component can be produced, for example, by polymerizing a group of monomers including component (A) (preferably component (a1)) and optionally component (B). Examples of the form of the resin component include water-soluble resins, water-dispersible resins, solvent-soluble resins, solvent-free resins, non-aqueous-dispersible resins, and composites thereof. Among them, the water-dispersible resin can be produced by a one-step or multi-step (two-step, or three-step or more) emulsion polymerization method or the like. These may have cross-linking reactivity, and may be either one-pack type, two-pack type, or the like.

The coating material in the present invention forms a coating having visible light transparency. As a result, it is possible to form a coating having transparency, and to obtain a finish that takes advantage of the color tone (multicolor pattern, etc.) of the existing coating surface. This visible light transmittance may be such that the existing film surface can be visually recognized.

The degree of visible light transmission can be indicated by visible light transmittance. Visible light transmittance is preferably 10% or more, more preferably 10 to 100%, still more preferably 15 to 90%. 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.

The coating material in the present invention forms a film having an ultraviolet transmittance of 30% or less, preferably 20% or less, more preferably 0 to 15%. In the present invention, when the ultraviolet transmittance is within the above range, the resistance to sunlight can be enhanced, and effects such as suppressing deterioration such as discoloration and cracking and maintaining aesthetic appearance can be obtained. The ultraviolet transmittance is a value obtained by measuring the transmittance of light with a wavelength of 350 nm for a film with a thickness of 30 μm using a spectrophotometer (transmittance is 100% when there is no film (air)). .

As means for obtaining such an ultraviolet transmittance, for example,
(1) Use a coating material containing a resin component having an ultraviolet absorbing group.
(2) Use a covering material containing an ultraviolet absorber.
(3) Use a covering material containing ultraviolet shielding powder.
etc. These means may be employed singly or in combination.

In the above (1), for example, a resin component containing an ultraviolet absorbing group-containing monomer may be used as the component (B). The ratio of the UV-absorbing group-containing monomer in the resin component is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight.

Examples of the ultraviolet absorber (excluding compounds having a polymerizable unsaturated double bond) in (2) above include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and salicylate-based ultraviolet absorbers. cyanoacrylate UV absorbers, benzoate UV absorbers, malonic acid ester UV absorbers, oxalic acid anilide UV absorbers, and the like. Among these, benzophenone-based UV absorbers include, for example, 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- methoxy-2'-carboxybenzophenone, 2-hydroxy-4-stearyloxybenzophenone and the like. Examples of benzotriazole-based UV 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-benzotriazole-2 -yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, methyl 3-(3-(2H-benzotriazol-2-yl) -5-t-butyl-4-hydroxyphenyl)propionate and polyethylene glycol reaction products. Examples of triazine-based UV 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)-glycidate ester reaction product, 2,4-bis" 2-Hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, etc. These can be used singly or in combination of two or more. is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the resin component.

As the ultraviolet shielding powder in (3) above, those having the ability to absorb and/or reflect ultraviolet rays can be used, and examples thereof include alumina, zirconium oxide, titanium oxide, magnesium oxide, zinc oxide, boron nitride, and oxychloride. Bismuth, zinc phosphate and the like can be mentioned. These can be used singly or in combination of two or more. The average particle size of the ultraviolet shielding powder is preferably 1 to 200 nm. In (3) above, it is desirable to set the mixing ratio of the ultraviolet shielding powder within a range in which visible light transmittance can be ensured.

In addition to the components described above, the coating material of the present invention may optionally contain known additives such as aggregates, color grains, dyes, thickeners, wetting agents, and so on, as long as they do not significantly impair the effects of the present invention. Antifreezing agents, filming aids, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, antifoaming agents, light stabilizers, antioxidants, adhesion promoters, antifouling agents, hydrophilization agents, water repellents, cross-linking agents, curing accelerators, catalysts, and the like.

In the present invention, a new coating is formed by applying (coating) such coating materials (the first coating material and the second coating material) to the existing coating surface. That is, the first coating material and the second coating material are sequentially applied to the existing coating surface to form a new coating. In the present invention, it is desirable to apply the first coating material, dry the coating, and then apply the second coating material. As the first covering material and the second covering material, those satisfying the above conditions can be used. Such new coatings are transparent and have visible light transmission properties.

In the present invention, the first coating material used has a pigment volume concentration lower than that of the second coating material. That is, the first coating material has a relatively low pigment volume concentration, and the second coating material has a relatively high pigment volume concentration. In the present invention, by using the first coating material and the second coating material of such an aspect, the progress of deterioration such as cracks caused by the existing coating surface can be sufficiently suppressed, and the appearance can be maintained. Effects such as life extension can be enhanced. In addition, a calm finished appearance with reduced luster can be obtained, and the beauty of the finished appearance can be maintained for a long period of time. The pigment volume concentration in the present invention is the volume percentage of the pigment contained in the dry film, and is a value obtained by calculation from the blending amounts of the resin component and the pigment that constitute the coating material.

A coating material satisfying such a pigment volume concentration condition can be obtained by adjusting the pigment concentration in the coating material. Examples of pigments mixed with the coating material include coloring pigments and extender pigments. The UV shielding powders described above can also be used as pigments.

Examples of coloring pigments include titanium oxide, zinc oxide, carbon black, ferric oxide (red iron oxide), molybdate orange, yellow iron oxide, ultramarine blue, cobalt green, iron-chromium composite oxide, manganese-bismuth composite oxide, and manganese. Inorganic coloring pigments such as yttrium composite oxides and manganese iron cobalt composite oxides, azo-based, naphthol-based, pyrazolone-based, anthraquinone-based, perylene-based, quinacridone-based, disazo-based, isoindolinone-based, benzimidazole-based, and phthalocyanine-based pigments , quinophthalone-based organic coloring pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, metallic pigments and other functional pigments. These can be used singly or in combination of two or more.

Extender pigments include, for example, calcium carbonate, kaolin, clay, china clay, china clay, talc, mica, silica, aluminum hydroxide, magnesium hydroxide, glass beads, resin beads, cold water stone, feldspar, silica stone, silica sand, and the like. Pulverized materials, glass pulverized materials, resin pulverized materials and the like can be mentioned. These can be used singly or in combination of two or more. Of these, resin beads are suitable as extender pigments, and examples of resin beads include urethane resin beads, acrylic beads, polyethylene beads, polypropylene beads, polymethyl methacrylate beads, polystyrene beads, polyacrylonitrile beads, and nylon beads. , styrene acrylic beads, silicon beads, fluorine beads, cellulose beads, vinyl chloride beads, EVA (ethylene vinyl acetate copolymer) resin beads, and the like. A solid product is preferable as the resin beads.

The average particle size of the extender is preferably 0.5-30 μm, more preferably 1-20 μm. The refractive index of the extender is preferably 1.3-1.7, more preferably 1.35-1.65. The use of such extender pigments is preferable in terms of ensuring the transparency of the film and improving the aesthetic appearance of the finished appearance. The average particle size is a value measured by a light scattering method, and the refractive index is a value measured using an Abbe refractometer.

The pigment volume concentration of the first coating material is 0% or more and less than 3%, preferably 0 to 2%, more preferably 0 to 1%. The first coating material may contain a coloring pigment and/or an extender pigment such that the pigment volume concentration is within the above range. As for the first coating material, an aspect in which no pigment is included (that is, the pigment volume concentration is 0%) is also suitable. By setting the upper limit of the pigment volume concentration of the first coating material to the above value, it is possible to obtain sufficient effects such as suppression of cracking while ensuring transparency.

The pigment volume concentration of the second coating material is 3-50%, preferably 5-40%, more preferably 8-30%. The second coating material may contain a coloring pigment and/or an extender pigment such that the pigment volume concentration is within the above range. In the present invention, it is particularly desirable that the second coating material contains at least an extender. The pigment volume concentration of the color pigment in the second coating material is preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%. The pigment volume concentration of the extender pigment in the second coating material is preferably 3 to 50%, more preferably 5 to 40%, still more preferably 8 to 30%. In the second coating material, the coloring pigment and the extender pigment are each within the range of the above-mentioned volume concentration of the pigment, so that a calm finished appearance can be easily obtained while ensuring transparency, and furthermore, it is sufficient to suppress cracks. effect can be obtained.

In the present invention, materials having different resin components can be used as the first covering material and the second covering material. In this case, it is desirable that r of the resin component in the first coating material (hereinafter also referred to as “r ₁ ”) is larger than r of the resin component in the second coating material (hereinafter also referred to as “r ₂ ”). That is, it is desirable to satisfy r ₁ −r ₂ >0. By using the first coating material and the second coating material containing the resin component in such an aspect, it is possible to sufficiently suppress the progress of deterioration such as discoloration and cracking caused by the existing coating surface. Adhesion to and the like are also improved. Furthermore, it is also possible to enhance effects such as maintenance of aesthetic appearance and extension of the life of the base material. Note that r ₁ and r ₂ are values calculated by Equations 1 and 2 below, respectively.
[Formula 1] r ₁ = {weight of component (a1) in the resin component in the first coating material}/{weight of component (A) in the resin component in the first coating material}
[Formula 2] r ₂ = {weight of component (a1) in the resin component in the second coating}/{weight of component (A) in the resin component in the second coating}

r ₁ represented by the above formula is preferably 0.1 to 1.0, more preferably 0.2 to 0.9, still more preferably 0.3 to 0.85, particularly preferably 0.4 to 0.4. 8, and r ₂ is preferably 0.05 to 0.8, more preferably 0.1 to 0.6, still more preferably 0.15 to 0.55, particularly preferably 0.2 to 0.5 is. The difference between r ₁ and r ₂ (r ₁ −r ₂ ) is preferably 0.01 or more, more preferably 0.05 to 0.5, even more preferably 0.08 to 0.4, and particularly preferably 0. .1 to 0.3. In such a case, it is possible to sufficiently obtain the above effects.

The film thickness of the new coating formed by laminating the first coating material and the second coating material is preferably 30 μm or more, more preferably 50 μm or more, still more preferably 60 μm or more, particularly preferably more than 65 μm, most preferably more than 65 μm. is 70 μm or more. By keeping the lower limit of the film thickness within the above range, the new film is sufficiently resistant to sunlight and water, suppresses deterioration such as discoloration and cracks caused by the existing film surface, and maintains aesthetic appearance over the long term. It is preferable in terms of Although the upper limit of the film thickness of the new coating is not particularly limited, it is preferably 300 μm or less, more preferably 250 μm or less, and still more preferably 200 μm or less. If the upper limit of the film thickness is within the above range, it is possible to obtain a finish that takes advantage of the uneven pattern of the existing film surface. In addition, the film thickness in this invention is a dry film thickness.

The film thickness ratio of the coating of the first coating material and the coating of the second coating material {(film thickness of first coating material):(film thickness of second coating material)} is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, still more preferably 65:35 to 35:65. With such an aspect, sufficient effects can be obtained in terms of suppression of discoloration, cracks, etc. caused by the existing coating surface, improvement of adhesion to the existing coating surface, maintenance of aesthetic appearance over a long period of time, and the like. .

Each of the first coating material and the second coating material can be applied multiple times. It is also possible to coat two or more types of coating materials corresponding to the first coating material, or to coat two or more types of coating materials corresponding to the second coating material. For example, two or more types with different color tones, such as a colorless transparent type and a colored transparent type, can be overcoated. When recoating, the coating can be dried at appropriate intervals. In such a case, it is desirable that the film thickness after recoating satisfies the above conditions.

A known coating tool can be used to apply each coating material. Examples of coating tools that can be used include sprays, rollers, and brushes. It is desirable to set the amount of each coating material to be applied, the number of coatings, and the like so that the final film thickness is within the above range. The coating amounts of the first coating material and the second coating material are each preferably 0.05-0.4 kg/m ² , more preferably 0.08-0.3 kg/m ² . The number of coats of each coating is preferably 1-3. At the time of coating, each coating material can be diluted as needed. Drying after application of each 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.

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

The following materials were prepared as coating materials.

Coating material 1: Water-dispersible resin 1 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 20: 52: 23: 2: 2 : A mixture of the emulsion polymer of 1), 72% by weight of component (A) in the resin constituents, r=0.72}, a thickener, a coalescing agent, an antifoaming agent, and water. Visible light transmittance 61%, UV transmittance 5%. Pigment volume concentration 0%.

Coating material 2: Water-dispersible resin 2 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 25: 30: 40: 2: 2 : A mixture of the emulsion polymer of 1), 55% by weight of component (A) in the resin constituents, r=0.55}, a thickener, a coalescing agent, an antifoaming agent, and water. Visible light transmittance 62%, UV transmittance 4%. Pigment volume concentration 0%.

Coating material 3: water-dispersible resin 2 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 25: 30: 40: 2: 2 : 1) emulsion polymer, 55% by weight of component (A) in resin constituents, r = 0.55}, thickener, film-forming aid, antifoaming agent, extender pigment (polymethyl methacrylate beads), and a mixture of water. 25% visible light transmittance, 4% UV transmittance. Pigment volume concentration 18%.

Coating material 4: water-dispersible resin 3 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 32: 18: 45: 2: 2 : A mixture of the emulsion polymer of 1), 50% by weight of component (A) in the resin constituents, r=0.36}, a thickener, a coalescing agent, an antifoaming agent, and water. Visible light transmittance 62%, UV transmittance 5%. Pigment volume concentration 0%.

Coating material 5: water-dispersible resin 3 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 32: 18: 45: 2: 2 : 1) emulsion polymer, 50% by weight of component (A) in resin constituents, r = 0.36}, thickener, film-forming aid, antifoaming agent, extender pigment (polymethyl methacrylate beads), and a mixture of water. 25% visible light transmittance, 5% UV transmittance. Pigment volume concentration 18%.

Coating material 6: water-dispersible resin 4 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 46: 4: 45: 2: 2 : 1) emulsion polymer, 50% by weight of component (A) in resin constituents, r = 0.08}, thickener, film-forming aid, antifoaming agent, extender pigment (polymethyl methacrylate beads), and a mixture of water. 25% visible light transmittance, 6% UV transmittance. Pigment volume concentration 18%.

Coating material 7: water-dispersible resin 5 {cyclohexyl methacrylate/2-ethylhexyl acrylate/methyl methacrylate/photostable group-containing monomer/acrylic acid (weight ratio 25:30:42:2:1) emulsion polymer, resin (A) component 55% by weight in the constituent components, r = 0.55}, a thickener, a film-forming aid, an antifoaming agent, water, and a triazine-based ultraviolet absorber (0.3 per 100 parts by weight of the resin component parts by weight). 60% visible light transmittance, 25% UV transmittance. Pigment volume concentration 0%.

Coating material 8: water-dispersible resin 6 {cyclohexyl methacrylate/2-ethylhexyl acrylate/methyl methacrylate/photostable group-containing monomer/acrylic acid (weight ratio 32:18:47:2:1) emulsion polymer, resin (A) component 50% by weight in the constituent components, r = 0.36}, thickener, film-forming aid, antifoaming agent, extender pigment (polymethyl methacrylate beads), water, and triazine-based ultraviolet absorber ( 0.3 parts by weight per 100 parts by weight of the resin component). 27% visible light transmittance, 24% UV transmittance. Pigment volume concentration 18%.

Coating material 9: water-dispersible resin 2 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 25: 30: 40: 2: 2 : A mixture of the emulsion polymer of 1), 55% by weight of component (A) in the resin constituents, r=0.55}, a thickener, a coalescing agent, an antifoaming agent, a color pigment, and water. 22% visible light transmittance, 4% UV transmittance. Pigment volume concentration 0.4%.

Coating material 10: water-dispersible resin 7 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 10: 8: 77: 2: 2 : A mixture of the emulsion polymer of 1), 18% by weight of component (A) in the resin constituents, r=0.44}, a thickener, a coalescing agent, an antifoaming agent, and water. Visible light transmittance 60%, UV transmittance 5%. Pigment volume concentration 0%.

Coating material 11: Water-dispersible resin 7 {cyclohexyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, UV-absorbing group-containing monomer, photostable group-containing monomer, acrylic acid (weight ratio 10: 8: 77: 2: 2 : 1) emulsion polymer, 18% by weight of component (A) in resin constituents, r = 0.44}, thickener, film-forming aid, antifoaming agent, extender pigment (polymethyl methacrylate beads), and a mixture of water. 25% visible light transmittance, 5% UV transmittance. Pigment volume concentration 18%.

Coating material 12: water-dispersible resin 8 {emulsion polymer of cyclohexyl methacrylate/2-ethylhexyl acrylate/methyl methacrylate/acrylic acid (weight ratio 10:8:81:1); %, r=0.44}, a mixture of thickener, coalescing agent, defoamer, and water. 59% visible light transmittance, 55% UV transmittance. Pigment volume concentration 0%.

In calculating the pigment volume concentration, the specific gravity of each water-dispersible resin was set to 1.0. The specific gravity of polymethyl methacrylate beads was set to 1.2.

(Example 1)
As an existing coating surface, a ceramic siding boat that has deteriorated due to outdoor exposure (having a tile-like uneven pattern on the surface, black acrylic resin coating on the concave parts, brown acrylic resin coating on the convex parts, acrylic on the whole) (having a silicon-based resin transparent film) was prepared. Coating material 1 as the first coating material was spray-coated on the entire surface of the existing coating so that the dry film thickness (indicated as "film thickness" in Table 1; hereinafter the same) was 38 μm, and dried for 3 hours. , Coating material 3 as a second coating material was spray-coated so as to have a dry film thickness of 38 μm, and dried and cured for 7 days to prepare a specimen. All the coating and curing steps were carried out under standard conditions (temperature 23°C, relative humidity 50%).

[Test I]
Adhesion of the specimens obtained by the above method was evaluated by a cross-cut tape method according to JIS K5600-5-6. The evaluation criteria are "A: defect area less than 10%", "B: defect area 10% or more and less than 30%", "C: defect area 30% or more and less than 50%", "D: defect part area is 50% or more". Table 1 shows the test results.

[Test II]
For the test specimen obtained by the above method, an accelerated weathering tester, iSuper UV Tester (manufactured by Iwasaki Electric Co., Ltd.), is used, and 6 hours of light irradiation and 2 hours of condensation (8 hours in total) are used as one cycle, and up to 60 cycles. An accelerated test was performed. At this time, changes in appearance (crack state) of the specimen surface were observed at the end of 20 cycles, 40 cycles, and 60 cycles, and the color difference before and after acceleration was measured. The change in appearance was evaluated in four grades (excellent; A>B>C>D; inferior) of "A: no change" and "D: progress of cracking". The color difference was evaluated as "A: color difference less than 1", "B: color difference 1 or more and less than 3", "C: color difference 3 or more and less than 10", and "D: color difference 10 or more". Table 1 shows the test results.

(Example 2)
Except for using the covering material 2 as the first covering material and the covering material 5 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Example 3)
Except for using the covering material 4 as the first covering material and the covering material 5 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Example 4)
Except for using the covering material 4 as the first covering material and the covering material 3 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Example 5)
Except for using the covering material 4 as the first covering material and the covering material 6 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Example 6)
Except for using the covering material 7 as the first covering material and the covering material 8 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Example 7)
A specimen was prepared in the same manner as in Example 1, except that the dry film thickness of each of the first coating material and the third coating material was 12 μm, and the same test was performed. Table 1 shows the test results.

(Example 8)
Except for using the covering material 9 as the first covering material and the covering material 5 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Comparative example 1)
Except for using the covering material 10 as the first covering material and the covering material 11 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Comparative example 2)
Except for using the covering material 11 as the first covering material and the covering material 10 as the second covering material, a specimen was prepared in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

(Comparative Example 3)
Except for using the covering material 12 as the first covering material and the second covering material, a specimen was produced in the same manner as in Example 1, and the same test was performed. Table 1 shows the test results.

[Test III]
The specimens of Examples 1 to 8 were exposed to the outdoors for 6 months, and the change in appearance due to dirt on the surface of the specimen was observed. A>B>C>D; inferior). Table 1 shows the test results.

Claims (3)

A coating forming method for forming a new coating by sequentially applying a first coating material and a second coating material to an existing coating surface provided on a base material,
The existing coating surface has an uneven pattern and / or a multicolor pattern,
Each of the first covering material and the second covering material is
Containing a resin component containing 20% by weight or more of a (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms in the resin component,
Forming a film having visible light transmittance and an ultraviolet transmittance of 30% or less,
The first coating material has a pigment volume concentration of 0% or more and less than 3%,
The pigment volume concentration of the second coating material is 3% or more and 50% or less,
The second coating material includes an extender pigment, and the extender pigment is a resin bead.
A film forming method characterized by: Each of the first covering material and the second covering material is
The (meth)acrylic acid alkyl ester (A) having an alkyl group having 3 or more carbon atoms includes a (meth)acrylic acid alkyl ester (a1) having an alkyl main chain having 3 or more carbon atoms,
When r is the weight ratio of the component (a1) in the component (A),
2. The film forming method according to claim ₁ , wherein r(r1) of the resin component in the first coating material is greater than r(r2) of the resin component in the _second coating material. 3. The method of forming a coating according to claim 1, wherein the new coating has a thickness of 30 [mu]m or more.