WO2017038802A1

WO2017038802A1 - Multi-layer coating

Info

Publication number: WO2017038802A1
Application number: PCT/JP2016/075288
Authority: WO
Inventors: 匡弥星野; 厚志金城
Original assignee: 日本ペイント株式会社
Priority date: 2015-08-31
Filing date: 2016-08-30
Publication date: 2017-03-09
Also published as: JP2017047558A; JP6704228B2

Abstract

To provide a multi-layer coating for covering the surface of a concrete substrate, the multi-layer coating having high transparency and application thereof not imparting a wet coloring onto the surface of the concrete. The transparent multi-layer coating includes: a lower coating layer derived from a lower coating composition, which contains at least one selected from the group consisting of acrylic resins, urethane resins, urea resins, and modified forms of these resins; a middle coating layer derived from a middle coating composition; and an upper coating layer derived from an upper coating composition. The transparent multi-layer coating is formed on the surface of a concrete substrate so that the difference between the L value of the concrete substrate surface before forming of the multi-layer coating and the L value of the concrete substrate surface after forming of the multi-layer coating is ‒2.0 to 4.0.

Description

Multilayer coating

The present invention relates to a multilayer coating film formed on the surface of a concrete substrate.

Conventionally, a technology that suppresses the progress of aging of a concrete structure due to wind and rain or salt damage by forming a coating film on the surface of the concrete structure with a curable (paint) composition, that is, a technology that imparts weather resistance is known. ing. Furthermore, from the viewpoint of the maintenance of concrete structures, it is necessary to detect cracks, bulges and defects on the surface as the concrete deteriorates over time, and the surface of the concrete structure can be visually confirmed. Requested. On the other hand, there is also a demand for ensuring the design properties of concrete structures, and when these are combined, the coating film formed on the surface of the concrete structure has the effect of suppressing the progress of aging of the concrete structure and is transparent. Is desirable.

Therefore, as a concrete reinforcing layer having sufficient reinforcing effect and visibility, a primer layer made of an epoxy resin, a resin layer made of a visible light curable vinyl ester resin, and a concrete reinforcing layer made of a reinforcing net and a reinforcing sheet are concreted. A technique of forming on the surface of a structure is known (for example, see Patent Document 1 described later).

Furthermore, in a concrete surface finishing method including an undercoat with a water-repellent waterproof material, an intermediate coat with an emulsion resin, and a top coat made of a resin waterproof material, the waterproof material accompanying cracks in the concrete surface due to the elasticity of the emulsion resin Is known (for example, see Patent Document 2 described later).

JP 2007-2514 A JP 2002-89006 A

By the way, when forming a transparent coating film on the surface of a concrete structure, a method of forming an undercoat layer (primer layer) with a sealer or the like has been conventionally used for the purpose of suppressing foaming derived from burrows on the surface of a concrete base material. Are known. However, since the phenomenon that the brightness of the part where the primer layer is applied is lower than the part where the primer layer is not applied, that is, the phenomenon that the surface of the substrate becomes wet color occurs, the primer layer in such a state is transparent. Even if the coating layer is formed, there arises a problem that it is difficult to visually confirm cracks and the like generated on the surface of the concrete substrate. Therefore, in a concrete structure coated with a multilayer coating film having a primer layer, in order to make the visual inspection work for maintenance easier, the coating layer is not only transparent, It is necessary that the concrete substrate surface does not become wet color due to the formation.

The invention described in Patent Document 1 has sufficient transparency by setting the total light transmittance of the resin layer to at least 30% or more, and further making the refractive index of the resin layer equal to the glass cloth used as the primer layer and the reinforcing sheet. To ensure. However, since the concrete surface cannot be prevented from becoming wet when the primer layer is applied, the visibility of the concrete surface has not been sufficient.

In the invention described in Patent Document 2, since the resin waterproofing material of the overcoat layer does not penetrate directly into the concrete surface, it depends on the difference in the wet color and the penetration rate of the material due to the penetration of the resin prevention material of the overcoat layer. Color unevenness is prevented. However, it is impossible to prevent the concrete surface from becoming wet when applying the primer layer. In addition, the prevention of the wet color in Patent Document 2 is intended to maintain the design, and the visibility when the visual inspection work for the maintenance of the concrete structure is performed is not sufficiently ensured.

Thus, in the transparent and weather-resistant multilayer coating film covering the surface of the concrete base material, the multilayer coating film in which the concrete surface does not become a wet color when the coating film is formed has been sufficiently studied. There is no current situation.
The present invention has been made in view of the above, and is a multilayer coating film for covering the surface of a concrete base material, which has high transparency and does not turn the concrete surface into a wet color when applied. The purpose is to provide.

The present invention is a transparent multi-layer coating film formed on the surface of a concrete substrate, and includes an undercoat containing at least one selected from the group consisting of acrylic resins, urethane resins, urea resins, and modified products of these resins Before forming the multilayer coating film, comprising: an undercoat layer formed from the coating composition; an intermediate coating layer formed from the intermediate coating composition; and an overcoating layer formed from the top coating composition. A multilayer coating in which the difference between the L value (brightness) in the L * a * b * color system on the concrete substrate surface and the L value on the multilayer coating surface is −2.0 to 4.0 Relates to the membrane.

The film thickness of the multilayer coating film is preferably 300 μm to 1,500 μm.

The top coating composition preferably contains an epoxy resin (a1) having no aromatic ring, a modified aliphatic amine compound (b1), and flat inorganic particles (c1).

The top coating composition preferably further includes a (meth) acrylic resin (d1) having at least one crosslinkable silyl group and a silane coupling agent (e1).

The inorganic particles (c1) are preferably made of at least one of mica and glass flakes, and the average aspect ratio of the inorganic particles (c) is preferably 20 to 1,000.

The intermediate coating composition preferably contains an epoxy resin (a2) having no aromatic ring and a modified aliphatic amine compound (b2).

According to the present invention, it is possible to provide a transparent multilayer coating film that covers the surface of a concrete base material, has weather resistance and high transparency, and does not turn the concrete surface wet by application.

Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<Multilayer coating film>
The multilayer coating film according to this embodiment is a transparent multilayer corrosion-resistant multilayer coating film formed on the surface of a concrete substrate. In this embodiment, the concrete base material that is the object to be coated may be a concrete structure. Concrete structures include bridges, tunnels, elevated roads and buildings. The multilayer coating film is formed by sequentially arranging an undercoat layer, an intermediate coat layer, and an overcoat layer. Specifically, after the base coating composition is applied to the concrete surface and cured, the intermediate coating composition is further applied and cured, and then the top coating composition is applied and cured to form a multilayer coating film. The
In addition, the multilayer coating film according to the present embodiment formed an L value (brightness) in the L * a * b * color system on the surface of the concrete substrate before the multilayer coating film formation, and the multilayer coating film. The difference from the L value on the surface of the subsequent multilayer coating film is −2.0 to 4.0.
Hereinafter, the respective coating compositions used in the respective coating layers of the undercoat layer, the intermediate coat layer, and the top coat layer will be sequentially described.

<Undercoat paint composition>
The undercoat coating composition according to the present embodiment includes at least one of acrylic resin, urethane resin, urea resin, and modified compositions of these resins. Moreover, it is preferable that an epoxy resin is not contained in a primer coating composition. Since the epoxy resin is not included, the base material does not become a wet color even if an undercoat layer is formed.

The acrylic resin contained in the undercoat coating composition in the present embodiment is a copolymer of acrylic monomers or a copolymer of acrylic monomers and other ethylenically unsaturated monomers. Examples of acrylic monomers include acrylic acid or methacrylic acid methyl, ethyl, propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, lauryl, phenyl, benzyl, 2-hydroxyethyl, 2-hydroxy Examples include esterified products such as propyl and 4-hydroxybutyl; ring-opening adducts of caprolactone of acrylic acid or 2-hydroxyethyl methacrylate. Examples of the ethylenically unsaturated monomer copolymerizable with these include styrene, α-methylstyrene, itaconic acid, maleic acid, and vinyl acetate.
The acrylic resin in the present embodiment may be an emulsion polymerized acrylic emulsion resin or an aqueous resin such as an aqueous acrylic resin. Examples of the acrylic emulsion resin include an acrylic emulsion, an acrylic styrene emulsion, and a vinyl acetate emulsion. Examples of the aqueous acrylic resin include a one-component aqueous resin and a two-component curable aqueous acrylic urethane resin composed of an aqueous acrylic polyol and a water-dispersible polyisocyanate.

The urethane resin contained in the undercoat coating composition in the present embodiment is a resin having a urethane bond obtained by reaction of various polyol components such as acrylic polyol, polyester polyol, polyether polyol, polycarbonate polyol and the like with an isocyanate compound. Examples of the isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and mixtures thereof, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, and mixtures thereof. Naphthalene-1,5-diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate and the like.

The urea resin contained in the primer coating composition in this embodiment is a resin having a urea group (—NH · CO · NH—) in the molecule, obtained by a reaction between an amine compound and an isocyanate compound. As the isocyanate compound, the same isocyanate compound as that used for the urethane resin is used. As the amine compound, for example, ether amine and primary amine are used. Examples include 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxy-1-propylamine, ethanolamine, 6-aminohexanol, p-methoxybenzylamine and the like.

The undercoat paint composition containing the above compound may be in any form of an organic solvent-type paint, an aqueous paint containing an emulsion paint, or a solventless form. As the organic solution-type paint or water-based paint, a one-component paint may be used, or a two-component mixed paint comprising a main agent and a curing agent may be used.

In this embodiment, even if an undercoat layer is formed using these undercoat paint compositions, the concrete base material does not become a wet color, and therefore, good visibility of the concrete base material surface can be secured.
Although details are unknown as this reason, it is considered that the primer coating composition described above is different in the permeability to the concrete base material and the refractive index of the formed primer layer from the coating composition containing an epoxy resin.

<Inner coating, top coating composition>
The intermediate coating composition used for forming the intermediate coating layer according to this embodiment preferably includes an epoxy resin (a2) having no aromatic ring and a modified aliphatic amine compound (b2). Moreover, the top coating composition used for forming the top coating layer comprises an epoxy resin (a1) having no aromatic ring, a modified aliphatic amine compound (b1), and flat inorganic particles (c1). It is preferable to include, and it is more preferable to further include a (meth) acrylic resin (d1) having at least one crosslinkable silyl group and a silane coupling agent (e1).

The epoxy resin (a) according to this embodiment does not have an aromatic ring. Since the epoxy resin (a) does not have an aromatic ring, a transparent coating film having high weather resistance can be formed. Examples of the epoxy resin (a) having no aromatic ring include hydrogenated bisphenol type epoxy resin, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol di Examples thereof include glycidyl ether, glycerin diglycidyl ether, and trimethylolpropane triglycidyl ether.
Examples of the hydrogenated bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol B type epoxy resin, bisphenol C type epoxy resin, bisphenol E type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, and bisphenol S type. Examples thereof include hydrogenated bisphenol type diglycidyl ether (for example, hydrogenated bisphenol A type epoxy resin) obtained by adding a hydrogen atom to a bisphenol polyglycidyl ether type epoxy resin such as an epoxy resin. Specific examples of the hydrogenated bisphenol type epoxy resin include Epolite 4000 (Kyoeisha Chemical Co., Ltd.), EPICLON EXA-7015 (DIC Corporation), ST-3000 (Nippon Steel & Sumikin Chemical Co., Ltd.) and the like. .

The epoxy resin (a) having at least two epoxy groups in one molecule has high reactivity with the modified aliphatic amine compound (b) described later, and the cured product can easily form a three-dimensional network. To preferred. Moreover, in order for the hardened | cured material when hardening the coating composition which concerns on this embodiment to be transparent, it is preferable that compatibility with the other component of an epoxy resin (a) is high. For example, a hydrogenated bisphenol A type epoxy resin is preferable because it has high compatibility with other components, and it is easy to obtain a transparent cured product, and the obtained cured coating film is excellent in weather resistance.

The epoxy resin (a1) used for the top coating composition and the epoxy resin (a2) used for the intermediate coating composition may be the same epoxy resin or different epoxy resins.

The content of the epoxy resin (a) in the solid content of the coating composition according to this embodiment is preferably 25 to 70% by mass. When content of the epoxy resin (a) in solid content of a coating composition is less than 25 mass%, it exists in the tendency for the intensity | strength of the coating film formed and the adhesiveness to a concrete structure to fall. When the content of the epoxy resin (a) in the solid content of the coating composition is higher than 70% by mass, the weather resistance of the formed coating film is lowered and tends to be yellowed.

The modified aliphatic amine compound (b) in this embodiment reacts with the epoxy resin (a) to form a transparent coating film having high weather resistance. The modified aliphatic amine compound (b) has high reactivity with the epoxy resin (a) and high compatibility with the (meth) acrylic resin (d) described later.
Examples of the modified aliphatic amine compound (b) include aliphatic polyamine epoxy adducts, alicyclic (alicyclic) polyamines, and polyamide amines. Examples of the modified aliphatic amine compound (b) include tomide 225X, Fujicure FXU870, Fujicure 5420F (manufactured by T & K TOKA Co., Ltd.) and Ancamide 500 (produced by Air Products Japan Co., Ltd.).

The modified aliphatic amine compound (b1) used for the top coating composition and the modified aliphatic amine compound (b2) used for the intermediate coating composition may be the same modified aliphatic amine compound or different modified fats. Group amine compounds may be used.

The solid content of the modified aliphatic amine compound (b) in the solid content of the coating composition according to this embodiment is preferably 2 to 26% by mass. When the content of the modified aliphatic amine compound (b) in the solid content of the coating composition is less than 2% by mass, the strength of the formed coating film and the adhesiveness to the concrete structure tend to decrease. When the content of the modified aliphatic amine compound (b) in the solid content of the coating composition is higher than 26% by mass, the weather resistance of the formed coating film tends to decrease and yellowing tends to occur.

The inorganic particles (c1) in the present embodiment are flat. The inorganic particles (c1) are preferably composed of at least one of mica and glass flakes, and the average aspect ratio is preferably 20 to 1,000. By using mica and glass flakes having an average aspect ratio in the above range as the inorganic particles (c1), the oxygen barrier property of the formed coating film can be improved, and the weather resistance of the coating film can be improved. When the average aspect ratio of the inorganic particles (c1) is less than 20, the oxygen barrier property of the formed coating film decreases, and when it exceeds 1,000, handling of the coating composition becomes difficult. Further, the average aspect ratio of the inorganic particles (c1) is more preferably 20 to 200, and further preferably 32 to 150. Moreover, it is preferable that an inorganic particle (c1) is a glass flake from a viewpoint of improving the transparency of a coating film by reducing the concealment rate of the coating film formed.

The average aspect ratio of the inorganic particles (c1) is, for example, 50% average particle size (L) measured by a laser diffraction particle size distribution measuring device (LMS-30; manufactured by Seishin Enterprise Co., Ltd.), and the surface measured by a transmission electron microscope. From the average thickness (a) of the interval, it can be calculated as average aspect ratio = L / a.

The average particle diameter of the inorganic particles (c1) is preferably 10 to 1,000 μm. When the average particle diameter of the inorganic particles (c1) is less than 10 μm, the weather resistance of the formed coating film tends to decrease, and when it exceeds 1,000 μm, the transparency of the formed coating film tends to decrease. is there.
The average particle size of the inorganic particles (c1) can be measured by a laser diffraction particle size distribution measuring device (SALD-3100: manufactured by Shimadzu Corporation).

Examples of mica used as the inorganic particles (c1) include A-21S (average aspect ratio 70, average particle diameter 23 μm), A-41S (average aspect ratio 80, average particle diameter 47 μm), and SYA-21RS (average aspect). Ratio 90, average particle diameter 27 μm) and B-82 (average aspect ratio 100, average particle diameter 180 μm, all of which are manufactured by Yamaguchi Mica Co., Ltd.).
Examples of glass flakes used as the inorganic particles (c1) include RCF-600 (average aspect ratio 120, average thickness 5 μm, ratio of particles 150 to 1,700 μm is 80% or more), RCF -2300 (average aspect ratio 1150, average thickness 2 μm, the proportion of particles 150 to 1,700 μm is 85% or less), RCF-160 (average aspect ratio 32, average thickness 5 μm, particle diameter 45 to 300 μm) (The ratio of which is accounted for 65% or more), (all of which are manufactured by Nippon Sheet Glass Co., Ltd.)

The content of the inorganic particles (c1) in the total solid content of the coating composition according to this embodiment is preferably 6 to 28% by mass. When the content of the inorganic particles (c1) in the total solid content of the coating composition is less than 6% by mass, the weather resistance of the formed coating film is lowered. When the content of the inorganic particles (c1) in the total solid content of the coating composition is higher than 28% by mass, the transparency of the formed coating film is lost. The content of the inorganic particles (c1) is more preferably 8 to 22% by mass, and further preferably 10 to 20% by mass.

The (meth) acrylic resin (d1) having at least one crosslinkable silyl group according to the present embodiment is a so-called acrylic silicon resin.
The (meth) acrylic resin (d1) may be obtained by copolymerizing a crosslinkable silyl group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer, and already exists as a polymer. The acrylic resin to be obtained may be obtained by modifying with a silicate oligomer having a crosslinkable silyl group. As the silicate oligomer having a crosslinkable silyl group, tetraalkoxysilane such as tetramethoxysilane or tetraethoxysilane, tetraphenoxysilane or a hydrolysis condensate thereof is used.

Specific examples of the crosslinkable silyl group-containing ethylenically unsaturated monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, allyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and γ-methacryloxypropyl. Examples include trimethoxysilane, γ-acryloxypropyltributoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

Other ethylenically unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Examples include cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, styrene, vinyltoluene, α-methylstyrene, (meth) acrylonitrile, (meth) acrylamide, vinyl acetate and the like.

The method of modifying the acrylic resin with a silicate oligomer having a crosslinkable silyl group is not particularly limited, and an ordinary radical polymerization method can be exemplified. The organic solvent used at that time can be appropriately selected as long as it dissolves the silicate oligomer and the (meth) acrylic resin. Specific examples thereof include methanol, ethanol, ethylene glycol monomethyl ether, toluene, xylene and the like.

Examples of the crosslinkable silyl group possessed by the (meth) acrylic resin (d1) include a functional group represented by the formula (1).
[Chemical 1]
-[Si (R ¹ ) _2-b (Y) _b O] _m -Si (R ² ) _3-a (Y) _a (1)

{In the formula, R ¹ and R ² are all alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, aralkyl groups having 7 to 20 carbon atoms, or (R ′) ₃ SiO— (R 'Is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and three R's may be the same or different), and represents a triorganosiloxy group represented by R ¹ or When two or more R ² are present, they may be the same or different. Y represents a hydroxyl group or a hydrolyzable group, and when two or more Y exist, they may be the same or different. a represents 0, 1, 2, or 3, and b represents 0, 1, or 2. m is an integer from 0 to 19. However, it shall be satisfied that a + mb ≧ 1. }

Examples of the hydrolyzable group include functional groups such as a hydrogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amide group, an aminooxy group, a mercapto group, and an alkenyloxy group. Among these, an alkoxy group, an amide group, and an aminooxy group are preferable, but an alkoxy group is particularly preferable because it is easily hydrolyzed under mild conditions. Among alkoxy groups, the lower the number of carbon atoms, the higher the reactivity. For example, since the reactivity decreases in the order of methoxy group, ethoxy group, and propoxy group, these functional groups can be selected according to the purpose and application.

Hydrolyzable groups and hydroxyl groups can be bonded to one silicon atom in the range of 1 to 3, and (a + Σb) is preferably in the range of 1 to 5. When two or more hydrolyzable groups or hydroxyl groups are bonded to the crosslinkable silyl group, they may be the same or different. The number of silicon atoms forming the crosslinkable silyl group is one or more, but in the case of silicon atoms linked by a siloxane bond or the like, it is preferably 20 or less. In particular, the crosslinkable silyl group represented by the general formula (2) is preferable because it is easily available.
[Chemical 2]
-Si (R ² ) _3-c (Y) _c (2)

(Wherein R ² and Y are the same as above, c is an integer of 1 to 3)

The (meth) acrylic resin (d1) condenses by forming a siloxane bond between silicon of crosslinkable silyl groups. When the coating composition according to the present embodiment further contains the (meth) acrylic resin (d1), a cured coating film having higher weather resistance can be formed.

The content of the (meth) acrylic resin (d1) in the solid content of the coating composition according to this embodiment is preferably 30 to 70% by mass, and more preferably 50 to 60% by mass. When the content of the (meth) acrylic resin (d) in the solid content of the coating composition is less than 30% by mass, the weather resistance of the formed coating film is lowered and tends to be yellowed. When the content of the (meth) acrylic resin (d1) in the solid content of the coating composition is higher than 70% by mass, the amount of the crosslinkable silyl group becomes relatively large, so that the storage stability of the resulting coating composition is increased. There is a tendency for the property to easily decline. Specifically, as the (meth) acrylic resin (d1), TA polymer SA120S, TA polymer SA110S, TA polymer SA100S (above, manufactured by Kaneka Corporation), ARUFON US-66170, ARUFUON US-6170 (above, Toagosei Co., Ltd.) Company-made).

When the coating composition forms a coating film, the silane coupling agent (e1) according to this embodiment comprises a polymer of (meth) acrylic resin (d1), an epoxy resin (a), and a modified aliphatic amine compound. The compatibility with the reactant (b) is increased, and the strength of the formed coating film is further improved.

The silane coupling agent (e1) preferably contains at least one of an amino group-containing silane coupling agent and an epoxy group-containing silane coupling agent. When the amino group-containing silane coupling agent is used, the amino group of the amino group-containing silane coupling agent reacts with the epoxy group of the epoxy resin (a), and the silanol group derived from the amino group-containing silane coupling agent is It reacts with the crosslinkable silyl group of the (meth) acrylic resin (d1). When an epoxy group-containing silane coupling agent is used, the epoxy group of the epoxy group-containing silane coupling agent reacts with the amino group of the modified aliphatic amine compound (b) and is derived from the epoxy group-containing silane coupling agent. The silanol group reacts with the crosslinkable silyl group of the (meth) acrylic resin (d1). By such a reaction, the polymer of the (meth) acrylic resin (d1) and the reaction product of the epoxy resin (a) and the modified aliphatic amine compound (b) are cross-linked, and the strength of the coating film formed is further increased. improves.

Examples of amino group-containing silane coupling agents include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropylmethyldimethoxysilane, and γ-aminopropylmethyl. Diethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2 -Aminoethyl) aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltriisopropoxysilane, γ-ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-benzyl- γ-amino B pills trimethoxysilane, N- vinylbenzyl -γ- aminopropyltriethoxysilane, and the like.
Specific examples of amino group-containing silane coupling agents include KBE-903 (3-aminopropyltriethoxysilane), KBM-602 (N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane) and KBM- 603 (N-2- (aminoethyl) -3-aminopropyltrimethoxysilane) (all of which are manufactured by Shin-Etsu Chemical Co., Ltd.).

Examples of the epoxy group-containing silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β- (3,4-epoxy Cyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and the like.
Specific examples of the epoxy group-containing silane coupling agent include KBM-403 (3-glycidoxypropyltrimethoxysilane), KBE-403 (3-glycidoxypropyltriethoxysilane), KBE-402 (3-glycidyl). Sidoxypropylmethyldimethoxysilane), KBM-303 (2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane), KBM-402 (3-glycidoxypropylmethyldiethoxysilane) (all above, Shin-Etsu Chemical) And the like).

The content of the silane coupling agent (e1) in the solid content of the coating composition according to this embodiment is preferably 0.1 to 20% by mass. When content of the silane coupling agent (e) in solid content of a coating composition is less than 0.1 mass%, it exists in the tendency for the transparency of the coating film formed to fall. When the content of the silane coupling agent (e1) in the solid content of the coating composition exceeds 20% by mass, the curability of the coating composition tends to decrease.

The coating composition according to the present embodiment may contain additives other than the above components as necessary within a range that does not impede its function. Additives include viscosity modifiers, condensation catalysts, UV absorbing compounds, antioxidants, curability modifiers, metal deactivators, ozone degradation inhibitors, phosphorus peroxide decomposers, lubricants, colored particles, Examples include an antifoaming agent, a foaming agent, an antifungal agent, and an antifungal agent.

The intermediate coating composition and the top coating composition according to this embodiment are a two-component mixed coating composition including a main agent containing an epoxy resin (a) and a curing agent containing a modified aliphatic amine compound (b). It is. By being a two-component mixed paint composition, workability at the site where repainting is performed is improved.
In the top coating composition, the silane coupling agent (e1) is appropriately blended into one of the main agent and the curing agent according to the type of functional group of the silane coupling agent. Specifically, when an epoxy-containing silane coupling agent is used as the silane coupling agent (e1), the modified aliphatic amine compound (b) and the silane coupling agent (e1) react in the curing agent. In order to avoid this, the silane coupling agent (e1) is blended in the main agent. On the other hand, when an amino group-containing silane coupling agent is used as the silane coupling agent (e1), in order to prevent the epoxy resin (a) and the silane coupling agent (e1) from reacting in the main agent, A ring agent (e1) is mix | blended with a hardening | curing agent.

As a method for preparing the main agent and the curing agent in the two-component mixed coating composition, a special method is not required, and a method commonly used by those skilled in the art can be used.
For example, as a preparation method of the main agent, the above additives and the like are added to a resin vehicle component, that is, a (meth) acrylic resin (d1) having at least one crosslinkable silyl group and an epoxy resin (a) in advance as a varnish. Of other components, disperse, ball mill, S. G. The method of preparing by disperse | distributing with dispersers, such as a mill and a roll mill, can be mentioned.
Further, for example, as a method for preparing a curing agent, a modified aliphatic amine compound (b), a silane coupling agent (e1), and an organic solvent as necessary are mixed. G. The method of preparing by disperse | distributing with dispersers, such as a mill and a roll mill, can be mentioned.

<Formation of undercoat layer, intermediate coat layer, and overcoat layer>
The undercoat layer, the intermediate coat layer, and the overcoat layer according to the present embodiment each have a mixing process, a coating process, and a curing process. In the case of using a one-component paint in the undercoating step, there is no mixing step.
In the mixing step, the main agent and the curing agent in the above embodiment are mixed to obtain a mixed coating composition (coating composition).

The mixing method of the main agent and the curing agent of the two-component mixed coating composition in the mixing step is not particularly limited. Examples of the mixing method include a method in which the main agent and the curing agent are blended and mixed with a hand mixer or a static mixer.

The mixing ratio of the main agent and the curing agent is preferably 70/30 to 90/10 in terms of the total solid content. By setting it as such a compounding ratio, formation of a coating film advances smoothly.
In addition, you may add 3rd components other than a main ingredient and a hardening | curing agent as needed.

In this embodiment, the total solid concentration of the coating composition is preferably 80 to 100% by mass. When the total solid content concentration of the coating composition is less than 80% by mass, the structural viscosity of the mixed coating composition tends to decrease. When the coating composition contains the (meth) acrylic resin (d1), an organic solvent having no functional group that reacts with the silyl group of the (meth) acrylic resin (d1) is added to the mixed coating composition. It is also possible to adjust to an appropriate viscosity by adding. Specific examples thereof include methanol, ethanol, ethylene glycol monomethyl ether, toluene, xylene and the like.

In the painting process, each coating composition is coated on the surface of the concrete structure using a trowel or a roller so that the total multilayer film thickness (target dry film thickness) after curing is 300 μm to 1,500 μm. . In this embodiment, since it coats by hand painting using a trowel or a roller, it can work simply also in the field where the concrete structure was installed. In this embodiment, it is preferable to use a brush or a roller in the coating process of the undercoat coating composition, and to use a trowel in the coating process of the intermediate coating composition and the top coating composition.

In the painting process, when each coating composition is coated such that the total film thickness after curing is less than 300 μm, the corrosion protection and protective effect of the concrete structure is lowered. On the other hand, when the mixed coating composition is applied so that the film thickness after curing exceeds 1,500 μm, the amount of the coating composition used for forming the coating film increases, so the cost increases. The transparency of the coating film decreases. Furthermore, since paint flow (sag) occurs on the vertical surface, the paint workability is significantly reduced. It is more preferable to apply the coating so that the total film thickness after curing is 700 μm to 1,300 μm.

In the curing process, each coating composition applied to the surface of the concrete structure is cured to form a transparent coating film. Although the curing method of the mixed coating composition in the curing step is not particularly limited, since a concrete structure is usually installed outdoors, a coating film is formed by leaving it under natural conditions.

In this embodiment, the undercoat layer is formed by applying and curing the undercoat paint composition, and then the intermediate coat layer is formed by further applying and curing the intermediate coat composition, and then further the overcoat paint. By applying and curing the composition, an overcoat layer is formed to form a multilayer coating film.

In the present embodiment, the L value on the surface of the concrete base material before the formation of the multilayer coating film, and the L value on the surface of the multilayer coating film after forming the multilayer coating film on the substrate surface A multilayer coating film is formed so that the difference (ΔL) is −2.0 to 4.0. When ΔL is within the above range, it becomes easy to visually detect cracks, blisters, and defects generated on the concrete surface even after the formation of the multilayer coating film. When △ L exceeds 4.0, the degree of whiteness increases and the multi-layer coating film conceals the concrete base material, making it difficult to visually determine the state of cracks, blisters and defects on the surface of the base material. become. Further, if ΔL exceeds −2.0, a phenomenon that the surface of the base material becomes wet color occurs, so that it is difficult to visually confirm the state of cracks, blisters and defects generated on the surface of the base material. . ΔL is more preferably in the range of −0.5 to 2.0.

The multilayer coating film according to this embodiment may be applied to a concrete structure immediately after construction for the purpose of preventive maintenance, or a concrete structure that has already been cracked for the purpose of repair. You may apply to. Moreover, you may apply to what is called a precast concrete product manufactured beforehand at the factory.

The oxygen permeability of a multilayer coating film formed using the coating composition and having a cured film thickness of 1,000 μm is 0.05 mg / (cm 2 · day) or less. When the oxygen permeability of a multilayer coating film having a thickness of 1000 μm after curing exceeds 0.05 mg / (cm 2 · day), the content of the inorganic particles (c1) increases, so the coating film formed is transparent. Sexuality is impaired.
The oxygen permeability can be measured using a Seikaken type film oxygen permeability meter.

The concealment rate of a multilayer coating film formed using the above coating composition and having a film thickness after curing of 300 μm is 45% or less. When the concealment rate of the multilayer coating film having a thickness of 300 μm after curing exceeds 45%, it becomes difficult to observe the surface state of the concrete structure because the transparency of the coating film is impaired. . The concealment rate of the coating film having a thickness of 300 μm after curing is preferably 5 to 45%. When the concealment ratio of the coating film having a thickness of 300 μm after curing is less than 5%, the amount of inorganic particles (c1) is substantially reduced, so that the oxygen permeability of the coating film tends to increase. It is in.

The concealment rate of the coating film can be determined by the following method.
First, the coating composition is applied to a concealment rate test paper (manufactured by Nippon Test Panel Co., Ltd.) used in a general coating test method in accordance with JIS K 5600-4-1 (b). Next, for the test specimens that were left at room temperature for 7 days at 23 ° C., the tristimulus value Y in the white part (Y _W ) and the black part (Y _B ) was obtained using a color difference meter (CR-400, manufactured by Konica Minolta Co., Ltd.). Measure and calculate the concealment rate Y _B / Y _W as a percentage.

In addition, “transparent” of the transparent coating film in the present embodiment is not limited as long as it can recognize the state and the object on the other side from one side through the coating film, and requires that the other side can be clearly recognized. Not what you want. The transparent coating film may be colored or cloudy as long as the state of the object on the other side can be visually recognized through the transparent coating film.

As mentioned above, according to the multilayer coating film in this embodiment, the following effects are produced.
(1) Since the undercoat layer of this embodiment is formed of an undercoat paint composition containing at least one of acrylic resin, urethane resin, urea resin, or modified compositions of these resins, The surface of the concrete does not become wet color due to the formation of the primer layer. The difference between the L value on the surface of the base material and the L value on the surface of the multi-layer coating film after forming the multi-layer coating film on the concrete base material surface is −2.0 to 4.0, preferably Since the multilayer coating film is formed so as to be −0.5 to 2.0, the surface of the concrete base material does not become a wet color, and good visibility is ensured.
(2) The multilayer coating film of the present embodiment is formed to have a film thickness of 300 μm to 1,500 μm, preferably 700 μm to 1,300 μm, so that the protective effect of the concrete base material is maintained and sufficient Transparency is obtained.
(3) The topcoat layer of this embodiment comprises an epoxy resin (a1) having no aromatic ring, a modified aliphatic amine compound (b1), flat inorganic particles (c1), and preferably a crosslinkable silyl The top coat layer has good oxygen barrier properties and transparency because it is formed by a top coat composition further comprising (meth) acrylic resin (d1) having at least one group and silane coupling agent (e1). Have
(4) Since the average aspect ratio of the inorganic particles (c1) used in the topcoat layer of this embodiment is 20 to 1,000, the formed topcoat layer has better oxygen barrier properties and transparency. Have.
(5) The intermediate coating layer of this embodiment is formed because it is formed of an intermediate coating composition containing the epoxy resin (a2) having no aromatic ring and the modified aliphatic amine compound (b2). The intermediate coating layer has good transparency.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[Examples 1 to 31, Comparative Examples 1 to 3]
As the undercoating composition, the resin shown in Table 1 is water-based resin (for example, VONCOAT 40-418EF (manufactured by DIC)), water is used as a diluent, and solvent-based resin is xylene. The solution was diluted by 1: 1 and sufficiently stirred with a desktop disper.
Epolite 4000 (manufactured by Kyoeisha Chemical Co., Ltd.) as the epoxy resin (a2) was used for the solid content (unit: parts by mass) shown in Table 1, respectively. Furthermore, the main component of the intermediate coating composition was obtained by adding xylene to adjust the total solid content concentration to 90% by mass and sufficiently stirring with a desktop disper.
Adjust the solid content concentration to 90 mass% by adding xylene to tomide 225X (manufactured by T & K TOKA Co., Ltd.) as the modified aliphatic amine compound (b2), and sufficiently stir with a desktop disper Thus, a curing agent for the intermediate coating composition was obtained.
Table 1 shows Epolite 4000 (produced by Kyoeisha Chemical Co., Ltd.) as the epoxy resin (a1) and RCF-600 (glass flake, average aspect ratio 120, produced by Nippon Sheet Glass Co., Ltd.) as the inorganic particles (c1). The solid content (unit: part by mass) was blended. Further, xylene was added to adjust the total solid content concentration to 90% by mass, and the mixture was sufficiently stirred with a desktop disper to obtain the main component of the top coating composition.
Adjust the solid content concentration to 90 mass% by adding xylene to tomide 225X (manufactured by T & K TOKA Co., Ltd.) as the modified aliphatic amine compound (b1), and sufficiently stir with a desktop disper Thus, a curing agent for the top coating composition was obtained.
In Examples 9 to 11, the silane coupling agent (e1) was further blended so as to have the solid content (unit: parts by mass) shown in Table 1. Of the silane coupling agent (e1), the amino group-containing silane coupling agent was blended in the curing agent, and the epoxy group-containing silane coupling agent was blended in the main agent.

In the examples and comparative examples, Epolite 4000 (manufactured by Kyoeisha Chemical Co., Ltd.) and ST-3000 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) were used as the epoxy resin (a). Moreover, Epicoat 1001 X75 (made by Japan Epoxy Resin Co., Ltd.) was used as an epoxy resin containing an aromatic part. Moreover, TA polymer SA120S (made by Kaneka Corporation) was used as the (meth) acrylic resin (d1). Further, as the modified aliphatic amine compound (b), Fuji Cure 5420F (manufactured by T & K TOKA Co., Ltd.) was used. Moreover, JER cure W (made by Mitsubishi Chemical Corporation) was used as a modified aromatic amine compound. In addition, as the inorganic particles (c1), glass flake A (RCF-600, average aspect ratio 120, average thickness 5 μm, proportion of particles 150 to 1,700 μm accounted for 80% or more), glass flake B (RCF -2300, average aspect ratio 150, average thickness 2 μm, component ratio of particle diameter 150-1700 μm accounted for 85% or less), glass flake C (RCF-160, average aspect ratio 32, average thickness 5 μm, particles The proportion of components having a diameter of 45 to 300 μm is 65% or more), glass flake D (RCF-015, average aspect ratio 3, average thickness 5 μm, the proportion of components having a particle size of 45 μm or less is 88% or more) (above, All manufactured by Nippon Sheet Glass Co., Ltd.). Further, titanium dioxide (TI-PURE R-706, manufactured by DuPont) was used. Further, as silane coupling agents (e1), KBM-602 (N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane), KBM-603 (N-2- (aminoethyl) -3-aminopropyl) Trimethoxysilane) and KBM-402 (3-glycidoxypropylmethyldiethoxysilane) were used.

Subsequently, using each coating composition described in Examples 1 to 31 and Comparative Examples 1 to 3 in Table 1 (test coating liquid in which the main agent and curing agent were mixed), a multilayer coating film was formed by the following method. Created.
The mixed coating compositions (test coating liquids) obtained in Examples 1 to 31 and Comparative Examples 1 to 3 were applied to a mortar plate (ISO compliant, manufactured by Nippon Test Panel Co., Ltd.) having a length of 70 mm, a width of 70 mm, and a thickness of 20 mm. The undercoat layer was painted with a brush, and the intermediate coat layer and the top coat layer were coated with a trowel so that the multilayer film thickness would be the target dry film thickness. Moreover, the coating interval of each layer was applied as 1 day.
As shown in Table 1, the film thickness of the multilayer coating film after curing obtained by the mixed coating compositions of Examples 1 to 5, 12 to 14, 17 to 31 and Comparative Examples 1 to 3 was 1000 μm. .
As shown in Table 1, the film thicknesses of the multilayer coating films obtained by the mixed coating compositions of Examples 6 to 11, 15 and 16 were 350 μm, 1450 μm, 650 μm, 750 μm, 1250 μm, 1350 μm, 250 μm. 1600 μm.
The following evaluation was performed using the coating composition obtained by the above method or the formed multilayer coating film. The results are shown in Table 1.

<Wetting color evaluation (ΔL, visual inspection)>
After the test body on which the multilayer coating film was formed was cured at room temperature for 7 days at room temperature and for 7 days at room temperature at 5 ° C., the wet color of each test body was measured in the L * a * b * color system. Evaluation was based on the difference in lightness (ΔL value).
Specifically, the L value (Y0) of the substrate surface (non-painted part) before coating film formation and the L value (Y1) on the substrate surface (multilayer coating film surface) after coating film formation are measured. ΔL was calculated by calculating the difference between the L value before coating film formation and the L value after coating film formation (ΔL = Y1−Y0). A color difference meter (manufactured by Konica Minolta, CR-400) was used for lightness (L value) measurement.
When ΔL is in the range of -2.0 to 4.0, the concrete substrate surface did not become wet color, and good visibility was ensured.

<Concealment rate during painting (transparency of coating film)>
Obtained in Examples 1 to 29 and Comparative Examples 1 to 3 on concealment rate test paper (manufactured by Nippon Test Panel Co., Ltd.) used in a general coating test method in accordance with JIS K 5600-4-1 (b). The obtained mixed coating composition (test coating liquid) was applied with a roller and a trowel. In addition, the quantity of the mixed coating composition to apply | coat was made into the quantity from which the dry film thickness (film thickness after hardening) of a multilayer coating film becomes a film thickness shown in Table 1, respectively.
Subsequently, about the test body which formed the multilayer coating film by leaving at room temperature for 7 days at 23 degreeC, using a color difference meter (the Konica Minolta company make, CR-400), a white part (YW) and a black part ( The tristimulus value Y in YB) was measured, and the concealment rate YB / YW was calculated as a percentage. The result of the concealment rate was evaluated as the transparency of the coating film. The results are shown in Table 1.
The smaller the value of YB / YW, the higher the transparency of the coating film. YB / YW is preferably 55 or less, and more preferably 45 or less. On the other hand, the coating film with YB / YW exceeding 55 has poor transparency, and it is difficult to visually observe the change in the state of the surface of the concrete structure (such as the occurrence of cracks).

<Oxygen permeability>
A release paper is laid on a Teflon (registered trademark) board, and the mixed coating compositions obtained in Examples 1 to 29 and Comparative Examples 1 to 3 have a dry film thickness (film thickness after curing) of the multilayer coating film, respectively. The coating film was coated so as to have a film thickness shown in Table 1, and after drying, the release paper was peeled off to obtain a free coating film. The free coating film was cured at a temperature of 23 ° C. and a relative humidity of 50% for 28 days after coating. The measurement of oxygen permeability was performed by the following procedure using a Seikaken type film oxygen permeability meter. The calculated oxygen permeability is shown in Table 1.
1. A platinum electrode (cathode) was adhered to the surface side of the free coating film.
2. An electrode containing 5 mL of 0.5 N calcium chloride solution in an electrode cell was placed in a beaker filled with distilled water.
3. The electrode was placed in a beaker filled with distilled water.
4). Nitrogen gas was blown into distilled water at a flow rate of 200 mL / min, oxygen gas was completely expelled to stabilize the recorder current, and then the zero point of the recorder was adjusted.
5). Oxygen gas was blown into distilled water at a flow rate of 200 mL / min, and the current value when the oxygen permeation amount became constant was read to calculate the oxygen permeability (unit: mg / (cm 2 · day)).

<Crack visibility (crack visual evaluation)>
A 40 mm × 120 mm × 10 mm mortar plate with U groove (ISO compliant, manufactured by Nippon Test Panel Co., Ltd.) was cut in half along the U-shape. Next, the halved plates were butted on a steel or stainless steel plate, and the entire circumference of the side surface was wound with an adhesive tape and fixed to prepare a test specimen. For these specimens, the mixed coating compositions obtained in Examples 1 to 31 and Comparative Examples 1 to 3 have the dry film thickness (film thickness after curing) of the multilayer coating film as shown in Table 1. I painted like this. After the coating film was dried, the sample surface was visually evaluated according to the following criteria. In order to visually confirm the surface substrate of the concrete frame after painting, the following evaluation needs to be 2 or more. In order to perform visual inspection easily, it is preferably 3, and more preferably 4. When it is 1, it becomes difficult to visually observe changes in the state of the surface of the concrete structure (such as the occurrence of cracks). Therefore, 2 or more was considered acceptable. The results are shown in Table 1.
(Evaluation criteria)
4: The substrate and cracks can be easily seen as in the case of no painting.
3: Although not completely transparent, the substrate and cracks are easily visible.
2: Concealment by the coating film occurs to some extent, but the substrate and cracks can be visually observed.
1: It is very difficult to visually check the substrate and cracks due to concealment of the coating film and wet color after primer coating.

<Weather resistance test (color difference)>
Mixed coating compositions (test coating solutions) obtained in Examples 1-31 and Comparative Examples 1-3 on a test plate (70 mm × 70 mm × 20 mm mortar, water: cement: sand = 0.6: 1: 2) ) Was painted with a trowel. In addition, the quantity of the mixed coating composition to apply | coat was made into the quantity used as the target dry film thickness (film thickness after hardening) described in Table 1. Subsequently, using a Super UV tester (I Super Tester SUV-W151, manufactured by Iwasaki Electric Co., Ltd.) on the coating film on the surface of the test plate, a wavelength of 295 to 450 nm, an illuminance of 100 mW / cm, and a black panel temperature of 63 ± 3 ° C. Ultraviolet rays were irradiated at a distance of 240 nm from the light source. A cycle of 4 hours of UV irradiation, 4 hours of dew condensation (ion-exchange water showering) and 0.1 hour of rest was repeated until the total UV irradiation time reached 100 hours. The degree of yellowing of the coating after irradiation with ultraviolet rays for 100 hours was confirmed.
The degree of yellowing is measured by the reflection method according to JIS K 7105 (fiscal 2004) and the b value measured by the reflection method according to JIS K 5600 4-1 B method. The difference (color difference Δb) between the b value and the b value after reflection was determined. The results are shown in Table 1. If Δb was less than 25, the result was acceptable. Among these, less than 20 is preferable and less than 10 is more preferable.

From the comparison between Examples 1 to 31 and Comparative Examples 1 and 2, the multilayer coating films of Examples 1 to 31 in which acrylic resin, urethane resin, or urea resin was used for the primer layer, The ΔL value after formation of the multilayer coating film is within the range of -2.0 to 4.0, compared with the multilayer coating films of Comparative Examples 1 and 2 that are not used for the coating layer, that is, the substrate has a wet color. It was confirmed that it was preferable in order not to become.
Further, from the comparison between Examples 1 to 31 and Comparative Examples 1 to 3, the multilayer coating film of Examples 1 to 31 was formed more than the multilayer coating film of Comparative Examples 1 to 3. It was found that the visibility of the subsequent substrate was good. From this result, acrylic resin, urethane resin, or urea resin is included in the undercoat coating composition, and the ΔL value after formation of the multilayer coating film is within the range of −2.0 to 4.0, It was confirmed that the visibility of the base material after the multilayer coating film was formed was improved.

From comparison between Example 1 and Example 28, it was found that the coating composition of Example 1 had higher weather resistance than the coating composition of Example 28. From this result, it was confirmed that the weather resistance of the formed coating film was improved by including an epoxy resin having no aromatic ring as the epoxy resin in the top coating composition.

From comparison between Example 1 and Example 29, it was found that the coating composition of Example 1 had higher weather resistance than the coating composition of Example 29. From this result, it was confirmed that the weather resistance of the coating film to be formed is improved by containing the modified aliphatic amine compound as an amine compound in the top coating composition.

From a comparison between Example 1 and Example 23, it was found that the coating composition of Example 1 had a higher oxygen barrier property of the coating film formed than the coating composition of Example 23. From these results, it was confirmed that the oxygen barrier property of the formed coating film was improved by containing inorganic particles having a specific aspect ratio (20 to 1,000) in the top coating composition.

From a comparison between Example 1 and Example 30, it was found that the coating composition of Example 1 had higher weather resistance of the coating film formed than the coating composition of Example 30. From this result, it was confirmed that the weather resistance of the coating film formed was improved by including an epoxy resin having no aromatic ring as the epoxy resin in the intermediate coating composition.

From comparison between Example 1 and Example 31, it was found that the coating composition of Example 1 had higher weather resistance than the coating composition of Example 31. From this result, it was confirmed that the weather resistance of the coating film to be formed is improved by containing the modified aliphatic amine compound as an amine compound in the intermediate coating composition.

Furthermore, from the comparison between Example 6 and Example 15 in which the coating films having different film thicknesses were formed, the coating film having a film thickness of 350 μm formed using the coating composition of Example 6 was the coating material of Example 15. It was found that the oxygen barrier property was higher than that of a coating film having a thickness of 250 μm formed using the composition.
On the other hand, from a comparison between Example 7 and Example 16 in which coatings having different thicknesses were formed, a coating having a thickness of 1,450 μm formed using the coating composition of Example 7 was It was found that the concealment rate was lower than that of the coating film having a film thickness of 1,600 μm formed using the coating composition.
From these results, when the coating composition according to the present embodiment is applied to the surface of a concrete structure, by setting the film thickness after curing to 300 μm to 1,500 μm, high transparency and oxygen barrier properties are achieved. It was confirmed that the provided coating film can be formed.

Claims

A transparent multilayer coating film formed on the surface of a concrete substrate,
An undercoat layer formed of an undercoat paint composition containing at least one selected from the group consisting of acrylic resins, urethane resins, urea resins and modified products of these resins;
An intermediate coating layer formed by the intermediate coating composition;
A topcoat layer formed by a topcoat composition,
A multilayer coating film in which a difference between an L value on the surface of the concrete base material before forming the multilayer coating film and an L value on the surface of the multilayer coating film is -2.0 to 4.0.
2. The multilayer coating film according to claim 1, wherein the multilayer coating film has a thickness of 300 μm to 1,500 μm.
The said top coat composition contains the epoxy resin (a1) which does not have an aromatic ring, a modified | denatured aliphatic amine compound (b1), and a flat inorganic particle (c1). Multi-layer coating.
The multilayer coating film according to claim 3, wherein the top coating composition further comprises a (meth) acrylic resin (d1) having at least one crosslinkable silyl group and a silane coupling agent (e1).
The inorganic particles (c1) are made of at least one of mica and glass flakes,
The multilayer coating film according to claim 3 or 4, wherein the inorganic particles (c1) have an average aspect ratio of 20 to 1,000.
The multilayer coating film according to any one of claims 1 to 5, wherein the intermediate coating composition contains an epoxy resin (a2) having no aromatic ring and a modified aliphatic amine compound (b2).