JP7028595B2 - Room temperature dry acrylic resin paint composition, coating film, base material with coating film, its manufacturing method and laminated coating film - Google Patents

Description

The present invention relates to a room temperature dry acrylic resin-based paint composition, a coating film, a substrate with a coating film, a method for producing the same, a laminated coating film, and a blister inhibitor.

Conventionally, (large steel) structures such as ships, bridges, tanks, plants, marine buoys, and underwater pipelines have been coated with laminated coating films of various specifications for the purpose of imparting various functions such as corrosion resistance. ing. For example, after the epoxy resin-based anticorrosion coating composition is applied as an undercoat, the topcoat coating composition is applied onto the formed anticorrosion coating film for the purpose of enhancing designability and weather resistance.

As the topcoat coating composition, a two-component reaction-curing type topcoat coating composition (eg, acrylic urethane resin-based coating composition, fluorourethane resin-based coating composition) is used. However, such a two-component reaction-curing type topcoat coating composition is complicated in handling because the coating composition itself is expensive and requires mixing of the main agent component and the curing agent component. There is also a problem in workability such as a limitation due to the usage time, and it may not be suitable for painting a large area such as the large structure.

In addition, the topcoat paint composition is a one-component type that can be obtained at low cost, has no time and effort due to mixing of the main agent component and the curing agent component, and is not limited by the pot life after mixing, and is excellent in workability. Topcoat coating compositions, specifically acrylic resin-based coating compositions and alkyd resin-based coating compositions, are also known.

Patent Document 1 describes a non-reaction-curable acrylic paint containing a specific acrylic resin and a plasticizer.
Further, Patent Documents 2 to 4 describe coating compositions that use a blocked polyisocyanate compound as a curing agent and cure under heating.

Japanese Unexamined Patent Publication No. 2016-180051 Japanese Unexamined Patent Publication No. 2012-193320 Japanese Unexamined Patent Publication No. 11-12451 Japanese Unexamined Patent Publication No. 8-302280

When a conventional acrylic resin-based paint is applied, especially when it is applied by airless spray, bubbles generated during painting remain in the coating film, and when the coating film is exposed to a high temperature environment, it expands or expands. There was a problem that the fusion expanded and blisters appeared on the surface of the coating film.
According to the paint described in Patent Document 1, it is possible to form a coating film having excellent blister resistance to some extent, but an environment in which the temperature of the steel sheet of the coating film becomes as high as 50 to 70 ° C. in summer or the like. It was found that when used underneath, especially when the coating film is a thick film, the fluff resistance is insufficient and the coating film tends to be blister-prone.

Substrates such as ships, bridges, and other large structures are difficult to heat because they are large structures, and room temperature dry paints are usually used. When the paints described in Patent Documents 2 to 4 are used as the paints used for such a base material, a predetermined coating film cannot be formed without heating, and the paints are dried at room temperature without heating. In this case, it is considered that the interval adhesion with the undercoat coating film such as the epoxy resin anticorrosion coating film is not good.

After forming the epoxy resin-based undercoat coating film, the topcoat paint is usually applied at predetermined intervals. In particular, when the base material is a ship, the interval (coating interval) from the undercoat coating to the topcoat coating is usually about 1 to 90 days. Therefore, it is required that the topcoat paint does not deteriorate its adhesion to the undercoat coating film (interval adhesion) even if the coating interval is long.

The present invention has been made in view of the above problems, and even when exposed to a high temperature environment, the generation of blisters is suppressed, and the adhesion to the undercoat coating film is excellent, particularly, the interval adhesion is excellent. It is an object of the present invention to provide a room temperature dry type coating composition capable of forming a topcoat coating film.

As a result of diligent studies on a method for solving the above-mentioned problems, it was found that the above-mentioned problems can be solved by a coating composition having a specific composition, and the present invention has been completed.
The configuration example of the present invention is as follows.

[1] A room temperature dry acrylic resin-based paint composition containing a hydroxyl group-containing (meth) acrylic resin (A) and a blocked isocyanate (B).

[2] The coating composition according to [1], wherein the blocked isocyanate (B) is an active methylene-based blocked isocyanate.
[3] The coating composition according to [2], wherein the active methylene-based blocked isocyanate is a blocked isocyanate blocked with malonic acid diesters.
[4] The content of the blocked isocyanate (B) is 1 to 20 parts by mass with respect to 100 parts by mass of the hydroxyl group-containing (meth) acrylic resin (A), according to any one of [1] to [3]. The described paint composition.

[5] The coating composition according to any one of [1] to [4], wherein the hydroxyl group-containing (meth) acrylic resin (A) has a hydroxyl value of 10 to 100 mgKOH / g.

[6] The coating composition according to any one of [1] to [5], which contains the pigment (C).
[7] The coating composition according to [6], wherein the pigment volume concentration (PVC) in the coating composition is 25 to 40%.

[8] A coating film formed by using the coating composition according to any one of [1] to [7].
[9] A base material with a coating film having the base material and the coating film according to [8].
[10] The coated base material according to [9], wherein the base material is a ship, a bridge, or a structure other than these.

[11] The coating composition according to any one of [1] to [7] is used on the surface of the undercoat coating film containing a resin having a group capable of binding to a hydroxyl group of the hydroxyl group-containing (meth) acrylic resin (A). A laminated coating film having a coating film formed in the above.

[12] The substrate comprises a step of applying the coating composition according to any one of [1] to [7] to a base material, and a step of drying the coated coating composition to form a coating film. A method for manufacturing a base material with a coating film.

[13] A blister inhibitor for a coating film obtained by using a room temperature dry type coating composition containing a blocked isocyanate (B).

According to the present invention, even when exposed to a high temperature environment due to solar radiation or the like, it is possible to obtain a coating film in which the generation of blisters is suppressed (excellent in bubble blistering resistance) and excellent in weather resistance. In particular, even if the thickness of the coating film is thick (eg, 150 μm or more), blister can be suppressed in the high temperature environment of the coating film.
Further, according to the present invention, it is possible to provide a coating composition capable of forming a topcoat coating film having excellent adhesion to an undercoat coating film, particularly excellent interval adhesion.
Since the coating composition of the present invention is a room temperature drying type, it can be suitably used for a base material such as a large structure that is difficult to heat when forming a coating film, and such a base material is inexpensive and inexpensive. A coating film can be easily formed. Further, even a coating composition that is dried at room temperature can be a coating composition having excellent storage stability.

≪Room temperature dry acrylic resin paint composition≫
The room temperature dry acrylic resin-based paint composition (hereinafter, also referred to as “acrylic paint”) according to the present invention contains a hydroxyl group-containing (meth) acrylic resin (A) and a blocked isocyanate (B).
Acrylic paints can form a coating film by drying at room temperature. In this way, by forming a coating film by drying at room temperature, the blocked isocyanate (B) can almost function as a curing agent when forming a coating film after coating. However, when the coating film becomes hot in summer or the like, the blocking agent in the coating film dissociates and an isocyanate group is generated, so that the isocyanate group and the hydroxyl group in the (meth) acrylic resin (A) are generated. It is considered that the blister of the coating film can be suppressed even in a high temperature environment.

The "normal temperature dry type paint" refers to a paint that can be dried and cured without passing through means such as heating, and specific examples thereof include solvent volatilization and curing type (lacquer type) paints, which are preferably non-drying type paints. Reaction-curing paints can be mentioned.
However, the acrylic paint does not necessarily have to be dried at room temperature to form a coating film, and may be heated as necessary when forming the coating film. The temperature at the time of this heating is lower than the temperature at which the blocking agent is completely deblocked from the blocked isocyanate (B) in order for the effect of the present invention to be exhibited. That is, the coating film at the stage of forming the coating film from the acrylic paint contains blocked isocyanate (B) in which deblocking has not occurred at all or has not occurred completely. More preferably, when forming a coating film from an acrylic paint, it is preferable that the blocked isocyanate (B) has almost no effect on curing. Therefore, the blocked isocyanate (B) used in the acrylic paint is a component completely different from the curing agent / cross-linking agent used in forming the coating film.

According to the acrylic paint, it can be a one-component type paint, preferably a one-component type paint, and such a paint does not require a mixture of a main component and a curing agent component, and is easy to handle. It has excellent workability such as no limitation due to the pot life, and is suitable for painting large areas such as large structures.

<Hydroxy group-containing (meth) acrylic resin (A)>
The hydroxyl group-containing (meth) acrylic resin (A) (hereinafter, also simply referred to as “acrylic resin (A)”) is not particularly limited as long as it is a hydroxyl group-containing (meth) acrylic resin.
It is considered that when such an acrylic resin (A) is used, an undercoat coating film, particularly a coating film having excellent "interval adhesion" can be obtained when the undercoat coating film is an epoxy resin-based anticorrosion coating film. ..
The acrylic resin (A) may be used alone or in combination of two or more.
In addition, "(meth) acrylic ((meth) acryl)" is a general term for acrylic (acryl) and methacryl (methacryl).

The acrylic resin (A) is, for example, a resin obtained by (co) polymerizing a hydroxyl group-containing (meth) acrylic compound, a hydroxyl group-containing (meth) acrylic compound, and other polymerizable unsaturated monomers (polymerization other than the hydroxyl group-containing (meth) acrylic compound). Examples thereof include a resin obtained by copolymerizing (sex-unsaturated monomer), a hydroxyl group-free (meth) acrylic compound and a resin obtained by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer, and examples thereof include a hydroxyl group-containing (meth) acrylic compound and other polymerizable non-polymerizable compounds. A resin obtained by copolymerizing a saturated monomer is preferable.

The acrylic resin (A) can be synthesized by a conventional method. Specifically, the (meth) acrylic compound, the unsaturated monomer and the polymerization initiator are mixed at 80 to 150 ° C. in the presence of a solvent. It can be synthesized by reacting with the above for about 3 to 10 hours.

Examples of the hydroxyl group-containing (meth) acrylic compound include hydroxyl group-containing (meth) acrylic acid esters such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate, and 2-hydroxy. Examples thereof include an additive of ethyl (meth) acrylate with ethylene oxide, propylene oxide, γ-butyrolactone or ε-caprolactone, and a (meth) acrylic acid ester containing a plurality of hydroxyl groups such as glycerol (meth) acrylate. These can be used alone or in combination of two or more.

Examples of the other polymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n- or iso-propyl (meth) acrylate, n-, iso- or tert-butyl (meth) acrylate, and hexyl (. Meta) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) (Meta) acrylic acid alkyl esters such as acrylates, cyclohexyl (meth) acrylates, phenyl (meth) acrylates, benzyl (meth) acrylates, isobornyl (meth) acrylates, glycidyl (meth) acrylates, dicyclopentanyl (meth) acrylates, Alicyclics such as tetrahydrofurfuryl (meth) acrylates and allyl (meth) acrylates, aromatic rings, heterocycles or vinyl group-containing (meth) acrylic acid esters, 2-methoxyethyl (meth) acrylates, 2-ethoxyethyl (meth) Acrylate, 3-methoxybutyl (meth) acrylate, m- or p-methoxyphenyl (meth) acrylate, o-, m- or p-methoxyphenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-dicyclo Alkoxy group-containing (meth) acrylic acid ester such as pentenoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dimethylaminobutyl (meth) acrylate , Dibutylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylamide, tertiary amino group-containing vinyl monomer such as dimethylaminopropyl (meth) acrylamide, (meth) acrylamide, butylaminoethyl (meth) acrylate and the like. Monocyclic basic monomers such as primary or secondary amino group-containing vinyl monomers, (meth) acrylonitrile, (meth) acrylic acid, vinylpyrrolidone, vinylpyridine, styrene, vinyltoluene, α-methylstyrene, Vinyl-based monomers such as vinyl acetate and vinyl propionate, monobasic or dibasic acid monomers such as crotonic acid, maleic acid, fumaric acid, and itaconic acid, monomethyl maleate, monoethyl maleate. , Monoesters of dibasic acid monomers such as monomethyl itaconic acid and monoethyl itaconic acid. These can be used alone or in combination of two or more.

As the acrylic resin (A), an acrylic paint having excellent pigment dispersibility can be obtained, and a topcoat coating having better adhesion to an undercoat coating tends to be obtained. Therefore, 2-hydroxyethyl (meth) is used as a monomer. ) A copolymer using acrylate and methacrylic acid is preferable.

When 2-hydroxyethyl (meth) acrylate is used as the hydroxyl group-containing (meth) acrylic compound, the content of the structural unit derived from 2-hydroxyethyl (meth) acrylate is 100% by mass of the acrylic resin (A). Is preferably 2% by mass or more, preferably 25% by mass or less, and more preferably 20% by mass or less from the viewpoint of corrosion resistance (water resistance, etc.) of the acrylic paint.
In the present invention, the content of the structural unit in the resin can be calculated from the amount of the monomer used in producing the resin.

When methacrylic acid is used as the other polymerizable unsaturated monomer, the content of the structural unit derived from methacrylic acid is preferably 0.5% by mass or more with respect to 100% by mass of the acrylic resin (A), and the upper limit thereof. The value is preferably 10% by mass from the viewpoint of corrosion resistance (water resistance, etc.) of the acrylic paint.

The other polymerizable unsaturated monomer preferably contains styrene because a topcoat coating film having an excellent balance between hardness and interval adhesion tends to be obtained. The content of the structural unit derived from styrene in the acrylic resin (A) is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, based on 100% by mass of the acrylic resin (A).

<Hydroxy group value>
Since the hydroxyl group value (mgKOH / g) of the acrylic resin (A) varies depending on the number of hydroxyl groups (OH groups) contained in the resin, it indicates how many hydroxyl groups are present in the acrylic resin (A). It becomes an index. The method for calculating the hydroxyl value is the method described in Examples described later. The hydroxyl value referred to here corresponds to the hydroxyl value (solid content) in the following examples.

It is considered that the hydroxyl group of the acrylic resin (A) is effective in suppressing the generation of blisters in the coating film by reacting with the blocked isocyanate (B).
However, when the acrylic resin (A) having an excessive amount of hydroxyl groups is contained in the coating film, the water resistance of the coating film may decrease if the reaction with the blocked isocyanate compound (B) has not progressed.
From these viewpoints, the hydroxyl value of the acrylic resin (A) is preferably 10 to 100 mgKOH / g, more preferably 80 mgKOH / g or less, and further 70 mgKOH / g or less from the viewpoint of improving the water resistance of the obtained coating film. Is particularly preferable.

<Weight average molecular weight (Mw)>
The weight average molecular weight (Mw) in terms of standard polystyrene measured by the gel permeation chromatography (GPC) method of the acrylic resin (A) makes it easy to obtain a topcoat film having excellent bubble resistance and interval adhesion at the same time. It is preferably 10,000 to 60,000, more preferably 20,000 to 40,000 from the viewpoint that it can be obtained.
The method for measuring Mw is the method described in Examples described later.

<Glass transition temperature (Tg)>
The glass transition temperature (Tg) of the acrylic resin (A) is preferably 10 to 80 ° C., more preferably 30 to 60 ° C. from the viewpoint that a coating film having excellent hardness and physical characteristics of the coating film can be easily obtained. be.
When Tg is in the above range, it is more preferable in that it is excellent in stain resistance and can easily obtain a coating film in which stickiness, cracks and the like are less likely to occur. If the Tg is below the above range and is too low, the adhesiveness of the coating film tends to increase when the coating film temperature rises, the stain resistance of the coating film decreases, and the coating film becomes sticky when walking on the coating film. I tend to feel a feeling. If Tg is higher than the above range and is too high, cracks tend to occur in the coating film.

The Tg can be measured by DSC (Differential Scanning Calorimetry), but Fox T.I. G. , Bull. Am. Physics Soc. It can also be calculated approximately by the following Fox formula described on pages 1, 3 and 123 (1956).

［式中、Ｘ_nは、アクリル樹脂（Ａ）を製造する際に用いたモノマーｎの、アクリル樹脂（Ａ）を製造する際に用いたモノマー全量に対する質量分率（質量％／１００）であり、Ｔｇ_nは、該モノマーｎのホモポリマーのガラス転移温度（ケルビン）である。］

[In the formula, X _n is a mass fraction (mass% / 100) of the monomer n used in producing the acrylic resin (A) with respect to the total amount of the monomers used in producing the acrylic resin (A). , Tg _n is the glass transition temperature (Kelvin) of the homopolymer of the monomer n. ]

Tg _n is, for example, Polymer Handbook 2nd Edition, J. Mol. The values described in Wiley & Sons, New York (1975) can be referred to. According to this handbook, for example, polystyrene has a Tg of 373K, butylpolymethacrylate has a Tg of 293K, butylpolyacrylate has a Tg of 219K, and 2-hydroxylethyl polymethacrylate has a Tg of 328K. Yes, the Tg of polymethacrylic acid is 458K.

<viscosity>
The acrylic resin (A) has a viscosity (25 ° C., mPa · s) of the resin in a 50 mass% xylene or toluene solution, preferably 300 to 15, from the viewpoint of obtaining an acrylic paint having excellent coatability. 000, more preferably 500 to 12,000.

<Content>
The content of the acrylic resin (A) is preferably 20 to 60% by mass, more preferably 20% by mass, based on 100% by mass of the solid content of the acrylic paint, from the viewpoint that a coating film having desired physical properties can be easily obtained. Is 25 to 50% by mass.
In the present invention, the "solid content of the acrylic paint" is the heating residue of the acrylic paint measured according to the JIS K5601-1-2 standard (heating temperature: 125 ° C., heating time: 60 minutes).

<Blocked isocyanate (B)>
Since the acrylic paint contains the blocked isocyanate (B) together with the specific acrylic resin (A), it is possible to obtain a topcoat coating film having excellent bubble resistance and interval adhesion.
Further, by using the blocked isocyanate (B), the blister of the coating film obtained by using the room temperature dry type paint composition can be suppressed, so that the block isocyanate (B) is the room temperature dry type paint composition. In particular, it can be said to be a blister inhibitor of a coating film obtained by using a room temperature dry type coating composition containing a hydroxyl group-containing resin. The blister inhibitor may contain a component other than the blocked isocyanate (B), if desired.
The blocked isocyanate (B) used for the acrylic paint and the blister inhibitor may be used alone or in combination of two or more.

As the blocked isocyanate (B), an active methylene-based blocked isocyanate is preferable from the viewpoint that a topcoat coating film having remarkably excellent bubble resistance and interval adhesion can be obtained.
Since the blocking agent of the active methylene-based blocked isocyanate dissociates at a relatively low temperature, the blocking agent of the active methylene-based blocked isocyanate gradually dissociates in a high-temperature environment (eg, 50 to 70 ° C.), which is a cause of blistering. It is presumed that the curing reaction with the hydroxyl group of the acrylic resin (A) proceeds, and the generation of blisters in the obtained coating film is suppressed.

When substantially only the active methylene-based blocked isocyanate is used as the blocked isocyanate (B), the blister of the coating film at high temperature can be suppressed more remarkably, and the interval adhesion, particularly the interval period is 30 days. When it exceeds, the adhesiveness is remarkably excellent.
Here, when substantially only the active methylene-based blocked isocyanate is used as the blocked isocyanate (B), the amount of the active methylene-based blocked isocyanate used is 80% by mass with respect to 100% by mass of the blocked isocyanate (B). That is all.

Specifically, the active methylene-based blocked isocyanate can be obtained by reacting the isocyanate group of the polyisocyanate compound with one or more active methylene-based compounds.

The polyisocyanate compound is a compound having two or more free isocyanate groups in one molecule, and is, for example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate, 1,2-xylylene diisocyanate (o-XDI), and the like. 1,3-Xylylene diisocyanate (m-XDI), 1,4-xylylene diisocyanate (p-XDI), tetramethylene diisocyanate, hexamethylene diisocyanate (HMDI), lysine diisocyanate, hydride diphenylmethane diisocyanate, hydride tolylene diisocyanate , Isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate, dimerate diisocyanate and other aliphatic, alicyclic and aromatic polyisocyanate compounds.
Further, examples of the polyisocyanate compound include isocyanurate-type polyisocyanates, bullet-type polyisocyanates, uretdione-type polyisocyanates, urethane-type polyisocyanates, and allophanate-type polyisocyanates using these polyisocyanate compounds.

Examples of polyhydric alcohols used in the urethane-type polyisocyanate include ethylene glycol, propylene glycol, butanediol, hexanediol, trimethylolpropane, glycerin, pentaerythritol, acrylic polyol, polyether polyol, polyester polyol and the like. ..

Examples of the active methylene compound for blocking the isocyanate group of these polyisocyanate compounds include malonic acid diester, acetoacetic ester, and acetylacetone.
Among these blocking agents, the point that the blocking agent dissociates at a relatively low temperature, the crosslink density of the coating film can be easily adjusted within an appropriate range, and a topcoat coating film having excellent bubble resistance and interval adhesion can be obtained. From this point of view, malonic acid diester is preferable.

Examples of the malonic acid diester include dimethyl malonic acid, diethyl malonic acid, diisopropyl malonic acid, di-propyl malonic acid, di n-butyl malonic acid, n-butyl malonic acid, methyl n-butyl malonic acid, and ethyl malonic acid t. -Butyl, methyl t-butyl malonic acid, dibenzyl malonic acid, diphenyl malonic acid, benzylmethyl malonic acid, ethylphenyl malonic acid, t-butylphenyl malonic acid, isopropylidene malonate and the like can be mentioned.

Examples of the acetoacetic acid ester include methyl acetoacetic acid, ethyl acetoacetate, isopropyl acetoacetic acid, n-propyl acetoacetic acid, t-butyl acetoacetic acid, n-butyl acetoacetic acid, benzyl acetoacetic acid, and phenyl acetoacetic acid.

As a blocking agent, even if some of these active methylene compounds are replaced with blocking agents such as alcohols, phenols, acid amides, imidazoles, pyridines, mercaptans, oximes and amines. good. Further, the active methylene-based blocked polyisocyanate compound may be a compound obtained by reacting a polyisocyanate compound with an active methylene-based compound to block it, and then reacting it with an alcohol to modify it by a transesterification reaction.

Examples of the active methylene-based blocked isocyanate include "Duranate MF-K60B" (manufactured by Asahi Kasei Corporation) and "BI 7963" (manufactured by Baxenden Chemicals Ltd.) in which the blocking agent is a malonic acid diester.

The content of the blocked isocyanate (B) is preferably 1 to 1 to 100 parts by mass of the acrylic resin (A) from the viewpoint that an excellent topcoat film can be obtained due to bubble resistance and interval adhesion. It is 20 parts by mass, more preferably 1 to 15 parts by mass, still more preferably 2 to 12 parts by mass, and particularly preferably 3 to 9 parts by mass.

The ratio (NCO / OH ratio) of the number of hydroxyl groups of the acrylic resin (A) to the number of isocyanate groups of the blocked isocyanate (B) is such that a topcoat coating film having better bubble resistance and interval adhesion can be obtained. It is preferably 0.01 to 0.5, more preferably 0.05 to 0.3, and even more preferably 0.1 to 0.25.
When the NCO / OH ratio is in the above range, the crosslink density of the coating film can be adjusted to an appropriate range. When the NCO / OH ratio exceeds the above range, the adhesiveness at intervals, particularly when the interval period exceeds 30 days, may decrease.

<Pigment (C)>
The acrylic paint may contain the pigment (C), if desired, as long as the effects of the present invention are not impaired.
The pigment (C) is not particularly limited, and examples thereof include colored pigments, extender pigments, functional pigments, and the like, which may be appropriately selected and used according to desired physical properties.
The pigment (C) may be used alone or in combination of two or more.

Examples of the coloring pigment include carbon black, titanium oxide, iron oxide, phthalocyanine blue, phthalocyanine green, azo compounds, and condensed polycyclic compounds.
Examples of extender pigments include barium sulfate, calcium carbonate, talc, mica and silica.
Examples of functional pigments include conductive pigments, fluorescent pigments, rust preventive pigments, aluminum pigments, and stainless steel pigments.

<Pigment Volume Concentration (PVC)>
The pigment volume concentration (PVC) in the acrylic paint is preferably 25 to 40%, more preferably 30 from the viewpoint that a coating film having an excellent balance of toughness and gloss can be easily obtained. ~ 40%.
When the PVC is below the above range, the bubble resistance of the coating film tends to decrease, and when the PVC exceeds the above range, the interval adhesion of the topcoat coating film tends to decrease.

The PVC refers to the total volume concentration of the pigment with respect to the volume of the solid content of the acrylic paint. Specifically, PVC can be obtained from the following formula.
PVC [%] = total volume of all pigments in acrylic paint x 100 / volume of solid content of acrylic paint

As described above, the solid content of the acrylic paint means the heating residue obtained according to JIS K 5601-1-2 (heating temperature: 125 ° C., heating time: 60 minutes), and the solvent (resin) in the raw material used. It can also be calculated as the amount excluding the solvent etc. contained in the solution etc.).

The volume of the solid content of the acrylic paint can be calculated from the mass and the true density of the solid content of the acrylic paint. The mass and true density of the solid content may be measured values or values calculated from the raw materials used.
The volume of the pigment can be calculated from the mass and true density of the pigment used. The mass and true density of the pigment may be measured values or values calculated from the raw materials used. For example, it can be calculated by separating the pigment and other components from the solid content of the acrylic paint and measuring the mass and true density of the separated pigment.

<Other ingredients>
If desired, the acrylic paint may contain a plasticizer, a sagging / anti-settling agent, an antifoaming agent, a catalyst, a solvent and the like as other components as long as the effects of the present invention are not impaired.
These other components may be used alone or in combination of two or more.

<Plasticizer>
The plasticizer is not particularly limited, but is chlorinated paraffin, phthalate ester, adipic acid ester, trimellitic acid ester, phosphoric acid ester, citric acid ester, sebacic acid ester, azelaic acid ester, maleic acid ester, benzoic acid ester, etc. Examples thereof include hydroxyl group-free acrylic resin, polyester resin, and epoxy resin.
The plasticizer may be used alone or in combination of two or more.

Commercially available plasticizers include the chlorinated paraffin "Toyoparax 150" (manufactured by Toso Co., Ltd.), the phthalate ester "DOP" (manufactured by CGG Esther Co., Ltd.), and the adipic acid ester "Monosizer". "W-242" (manufactured by DIC Co., Ltd.), "Monosizer W-705-NB" (manufactured by DIC Co., Ltd.), which is a trimellitic acid ester, and "TCP" (manufactured by Daihachi Chemical Industry Co., Ltd.), which is a phosphoric acid ester. ), "BAA-15" (manufactured by Daihachi Chemical Industry Co., Ltd.), which is a polyester resin, and the like. Of these, "Toyoparax 150", "DOP", and "TCP" are preferable. These plasticizers are often used in paint applications and are easily available.

The amount of the plasticizer used is preferably 0.5 to 10% by mass with respect to 100% by mass of the acrylic paint.

<Sauce prevention / sedimentation prevention agent>
The anti-sagging / sedimentation inhibitor is not particularly limited, but organic-based shaking agents such as amide wax-based shaking agents, hydrogenated castor oil-based shaking agents, and polyethylene oxide-based shaking agents; clay minerals such as bentonite, synthetic Examples thereof include inorganic rocking agents such as fine powder silica, and clay minerals such as amidowax-based rocking agents, polyethylene oxide-based rocking agents, synthetic fine powder silica and bentonite are preferable.
As the sagging prevention / sedimentation inhibitor, one type may be used alone, or two or more types may be used.

Examples of commercially available products of such anti-sagging / sedimentation preventive agents include "Disparon A630-20X" (manufactured by Kusumoto Kasei Co., Ltd.), which is an amidowax-based compound.

The amount of the anti-sagging / sedimentation inhibitor used is preferably 0.01 to 10% by mass with respect to 100% by mass of the acrylic paint.

<Defoamer>
The defoaming agent is not particularly limited, and examples thereof include acrylic, vinyl ether, silicone, butadiene, olefin, and fluorine compounds.
The defoaming agent may be used alone or in combination of two or more.

Examples of commercially available products of such an antifoaming agent include "Disparon OX-720" (manufactured by Kusumoto Kasei Co., Ltd.), which is an acrylic compound.

The amount of the defoaming agent used is preferably 0.01 to 5% by mass with respect to 100% by mass of the acrylic paint.

<catalyst>
The catalyst is not particularly limited, and examples thereof include Lewis acid, an amine compound, and an onium salt.
The catalyst may be used alone or in combination of two or more.

Lewis acids include organotin compounds such as diacetyltin diacetate, dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, diacetyltin dioctate, tin octylate and dibutyltin dioctate; zinc octylate, zinc stearate, oxalic acid. Organic zinc compounds such as zinc acid, zinc naphthenate, and zinc 2-ethylhexanate; organic zirconium compounds such as zirconium tetraacetylacetonate can be mentioned.

Examples of the amine compound include triethylenediamine, triethylamine, N, N, N', N'-tetramethylpropylenediamine, N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine, N-methylmorpholine, 1 , 2-dimethylimidazole, 1,5-diazabicyclo (4,3,0) nonen-5, 1,8-diazabicyclo (5,4,0) -undesen-7 (hereinafter also referred to as "DBU"), etc. Can be mentioned.

Examples of the onium salt include DBU phenol salt, DBU octylate, DBU carbonate, tetrabutylammonium chloride, tetrabutylammonium bromide and the like.

As the catalyst, Lewis acids are preferable, and organotin compounds are more preferable, because they have high catalytic activity and the like.

<solvent>
The solvent is not particularly limited, but toluene, xylene, "Swazole 1000" (manufactured by Maruzen Petrochemical Co., Ltd.), "T-SOL 100", "T-SOL 150" (manufactured by JXTG Energy Co., Ltd.), "LAWS". (Manufactured by Shell Chemicals Japan), aromatic hydrocarbon solvents, alcohol solvents such as ethylene glycol monobutyl ether, isopropyl alcohol, n-butanol, ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, n- Aliphatic hydrocarbon solvents such as hexane, n-octane, 2,2,2-trimethylpentane, isooctane, n-nonan, cyclohexane, and methylcyclohexane, ketone solvents such as methylisobutylketone, methylethylketone, and methylisobutylketone, minerals. Spirit and the like can be mentioned.
The solvent may be used alone or in combination of two or more.

<< Coating film, substrate with coating film and manufacturing method of these >>
The coating film according to the present invention (hereinafter, also referred to as “the present coating film”) is formed by using the acrylic paint, and the base material with a coating film according to the present invention has a base material and the present coating film.
When this coating film is exposed to a high temperature at which blisters are likely to occur, the isocyanate group of the blocked isocyanate (B) and the hydroxyl group of the acrylic resin (A) can form a crosslinked structure in the coating film. It is considered that the toughness is superior to that of the conventional acrylic resin-containing coating film, the expansion of the coating film and the fusion expansion of bubbles are suppressed, and as a result, the bubble resistance is excellent.

This coating film can be produced by applying an acrylic paint and drying it, and preferably, a step of applying the acrylic paint to the base material and drying the painted acrylic paint to form a coating film. It can be manufactured by a method including a step. According to the latter, a substrate with a coating film can be produced.

The method for applying the acrylic paint is not particularly limited, and conventionally known methods can be adopted, for example, roll coater, flow coater, airless spray, air spray, brush coating, iron coating, roller coating, dipping, pulling, and sink coating. , Arrangement, etc. can be done according to the usual method.
When a large structure is used as the base material, spray painting such as airless spray or air spray is preferable from the viewpoint of ease of painting when painting a large area. In such spray painting, air bubbles are likely to be generated during painting, and the air bubbles are likely to cause blisters. However, in the present invention, since the acrylic paint is used, even when spray painting is performed, the coating film is coated. Blisters can be significantly suppressed.
At the time of painting, the acrylic paint may be diluted with various solvents as needed.

Since the acrylic paint can form a coating film by drying at room temperature, it is preferable to dry the acrylic paint at room temperature when forming the coating film. In the present invention, the term "normal temperature" means not heating, and is usually about 0 to 30 ° C.
Examples of the method of drying the acrylic paint at room temperature include a method of leaving it in the atmosphere for about 1 to 14 days. Further, when the acrylic paint is dried, the humidity may be adjusted if necessary.
The acrylic paint may be heated if necessary when forming the coating film. The temperature at the time of this heating is lower than the temperature at which the blocking agent is completely deblocked from the blocked isocyanate (B). Specifically, it may be heated at about 5 to 60 ° C. in order to shorten the drying time.

The dry film thickness of the present coating film is not particularly limited, but is usually 20 to 350 μm, preferably 30 to 150 μm.
Further, depending on the coating location, coating method, etc., the dry film thickness may be 150 μm or more, and in some cases, 200 μm or more. Even so, unlike the case where the conventional paint is used, the blister of the coating film can be remarkably suppressed even in a high temperature environment.
When forming a coating film having such a film thickness, the coating film having the desired thickness may be formed by one coating, or the desired coating film may be formed by two coatings (more than necessary). A coating film having a thickness may be formed.

The base material is not particularly limited, and examples thereof include steel, aluminum, and FRP (fiber reinforced plastic). The base material is preferably a (large) structure, particularly from the viewpoint of further exerting the effects of the present invention, and specifically, a ship, a bridge, or a structure other than these (eg, a structure other than these). Tanks, plants, offshore buoys, underwater pipelines) and the like. In particular, when painting on the outer surface of the hull (ship) of passenger ships, cargo ships, tankers, etc. (especially parts such as the outer side, water line, deck, superstructure, etc. of the ship), bubble resistance and blister resistance Interval adhesion with the undercoat coating is required.

The base material may be a base material that has been surface-treated if necessary, and specifically, the surface of the base material such as rust, oil, moisture, and dust that has already been generated / adhered to the surface of the base material to be painted is attached. The base material may be a base material from which the kimono has been cleaned and removed, or may be a base material on which an undercoat coating film is previously formed by using an undercoat paint such as a sealer or a primer depending on the material of the base material. If necessary, the surface treatment may be performed before applying the undercoat paint.
That is, the base material also includes a base material on which an undercoat coating film is formed by using an undercoat paint such as a surface-treated base material, a sealer, and a primer.

≪Laminated coating film≫
The laminated coating film according to the present invention has the present coating film on the surface of the undercoat coating film containing a resin having a group capable of binding to the hydroxyl group of the hydroxyl group-containing (meth) acrylic resin (A). That is, the main coating film in this laminated coating film is a top coating film.

Since the laminated coating film has the main coating film, the coating film is exposed to a high temperature environment due to sunlight or the like, and blister due to air bubbles is likely to occur, and the coating film is suitably used as a coating film for a base material which may cause a problem of interval adhesion. can do. That is, the laminated coating film is usually provided on a base material and is suitably used as a base material with a laminated coating film containing the laminated coating film and the base material.

<Undercoat paint>
The undercoat paint is not particularly limited.
Examples of the group that can be bonded to the hydroxyl group include a halogeno group, an epoxy group, an alkoxy group, a carboxy group, and an isocyanate group.
As the undercoat paint, a paint preferably used for a base material of a ship or the like is preferable, and an anticorrosion paint is more preferable, and examples thereof include an epoxy resin-based paint such as an epoxy-based zinc rich primer and an epoxy-based rust-proof primer. The epoxy resin-based paint usually contains an epoxy-based resin and an amine-based curing agent, and may also contain a silane coupling agent, an extender pigment, a sagging inhibitor, and the like, if necessary.

When an epoxy resin-based paint is used as the undercoat paint, an undercoat coating film having a uniform film thickness and excellent corrosion resistance can be obtained, and the amount of acrylic paint to be applied to the surface of the undercoat coating film can be reduced. ..

Examples of the epoxy resin include bisphenol type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, phenol novolac type epoxy resin, cresol type epoxy resin, dimer acid modified epoxy resin, aliphatic epoxy resin, and oil ring. Examples thereof include group epoxy resins and epoxidized oil-based epoxy resins. Among these, bisphenol type epoxy resins such as bisphenol A type and F type are preferable because they are excellent in adhesion to the substrate and anticorrosion property of the obtained anticorrosion coating film.
The epoxy resin may be used alone or in combination of two or more.

As the epoxy resin, those on the market can be used. For example, examples of the bisphenol type epoxy resin include "jER828", "jER834", "jER1001", "jER1004", "jER807", "jER4004P", and "jER4007P" (all manufactured by Mitsubishi Chemical Corporation).

From the viewpoint of improving the corrosion resistance of the undercoat coating film, the epoxy-based resin is usually contained in an undercoat paint containing a solvent or the like in an amount of 10 to 60% by mass, preferably 20 to 50% by mass, and is a solid undercoat paint. It is desirable that the content is usually 10 to 70% by mass, preferably 10 to 60% by mass with respect to 100% by mass per minute.

As the amine-based curing agent contained in the undercoat coating material, for example, Mannig-modified amines formed by the Mannig condensation reaction between phenols, formarin and an amine compound, and / or aliphatic polyamines can be used. The first and second aminos, which are mainly produced by the condensation of dimer acid and polyamine and are reactive in the molecule, are easy to handle and the pot life of the undercoat is in a suitable range. It is preferable to use a polyamide amine having a group.

As such an amine-based curing agent, those on the market can be used. For example, "Luckamide TD-966" (manufactured by DIC Corporation) and "Sunmide 307D-60" (manufactured by Air Products Japan Co., Ltd.) can be mentioned.

The amine-based curing agent has an amino group of 0.35 to 0.9 equivalent, preferably 0.4 to 0.8 equivalent, with respect to 1 equivalent of the epoxy group in the epoxy-based resin. You can use it.
Further, the amine-based curing agent can be used in a ratio of, for example, 10 to 300 parts by mass, preferably 20 to 200 parts by mass with respect to 100 parts by mass of the epoxy resin.

The laminated coating film can be produced by forming an undercoat coating film using an undercoat coating material and forming a topcoat coating film using an acrylic paint on the undercoat coating material, but the base material is preferably used. In the process of applying the undercoat paint and curing the applied undercoat paint to form the undercoat paint, and applying the acrylic paint on the undercoat paint and drying the painted acrylic paint to apply the topcoat. It can be produced by a method including a step of forming a film.

If necessary, the surface of the base material may be surface-treated before applying the undercoat paint. When a zinc-based primer (zinc-based primary rust preventive primer) is used as the primer, the primer is usually applied after the surface of the base material (preferably steel material) is shot-blasted to remove scale. ..

When applying the undercoat paint, the undercoat paint may be diluted with various solvents as needed.
Examples of the method for applying the undercoat paint include the same method as the method for applying the acrylic paint, and the preferred method is also the same.
The undercoat paint is applied (painted) in an amount of, for example, 200 to 450 g / m ² so that the dry film thickness is about 100 to 200 μm / time.

The method for curing the coated undercoat paint is not particularly limited, and may be cured by heating at about 5 to 60 ° C. in order to shorten the curing time, but usually 1 to 14 at room temperature and in the atmosphere. It may be cured by leaving it for about a day.

The dry film thickness of the undercoat film is not particularly limited, but is usually 50 μm to 500 μm, preferably 100 μm to 350 μm.
When forming a coating film having such a film thickness, the coating film having the desired thickness may be formed by one coating, or the desired coating film may be formed by two coatings (more than necessary). A coating film having a thickness may be formed.

The acrylic paint is usually applied after a certain period (interval) after forming the undercoat coating film, although it depends on the desired application and the situation at the painting site.
The interval is usually about 1 to 90 days. As the acrylic paint, it is fully conceivable that there will be 90 days from the formation of the undercoat film (in some cases, an interval of about 180 days is required), so that the acrylic paint can be used. As a property, it is required to have excellent adhesion to the undercoat coating film after such an interval. Since the acrylic paint has excellent interval adhesion, it can be suitably used for painting at intervals of about 1 to 90 days from the formation of the undercoat coating film.

Examples of the method for forming the topcoat coating film on the undercoat coating film by using the acrylic paint include the same method as the method for forming the main coating film.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

The weight average molecular weight (Mw) and hydroxyl value (mgKOH / g) of the acrylic resins obtained in Production Examples 1 to 3 were measured by the test methods described below, and the solid content ratio (mass%) in the acrylic resin solution was measured. Was calculated. The results are shown in Table 1. In addition, "specific density (overall)" in Table 1 shows the specific gravity of the whole acrylic resin solution obtained in Production Examples 1 to 3, and "specific gravity (solid content)" was obtained in Production Examples 1 to 3. The specific gravity of the solid content in the resin solution is shown. Hereinafter, the same description has the same meaning.
The specific gravity was measured according to JIS K0061 (method for measuring density and specific gravity of chemical products).

<Weight average molecular weight (Mw) of acrylic resin>
The weight average molecular weight (Mw) of the acrylic resin was measured using GPC under the following conditions. The measurement conditions are as follows.
<GPC conditions>
Equipment: "HLC-8220GPC" (manufactured by Tosoh Corporation)
Column: "TSKgel SuperH2000" and "TSKgel SuperH4000" are connected (both manufactured by Tosoh Corporation, 6 mm (inner diameter) x 15 cm (length))
Eluent: Tetrahydrofuran (THF)
Flow velocity: 0.500 ml / min
Detector: RI
Column constant temperature bath temperature: 40 ° C
Standard substance: Polystyrene Sample preparation method: A small amount of calcium chloride was added to an acrylic resin solution to dehydrate, and then the filter obtained by filtering with a membrane filter was used as a GPC measurement sample.

<Measurement of solid content>
The heating residue (synonymous with "solid content") after the acrylic resin solution was dried in a hot air dryer at 125 ° C. for 60 minutes was measured, and the solid content ratio in the acrylic resin solution was calculated from the following formula.
Percentage of solids in acrylic resin solution (mass%) = (mass of the remaining heat / mass of resin solution before heating) x 100 (%)

<Measurement of hydroxyl value>
The hydroxyl value was measured as follows according to JIS K0070.
Accurately weigh 2 g of the sample (acrylic resin solution) in a round-bottom flask, add exactly 5 ml of an acetylation reagent (a solution of 25 g of acetic anhydride dissolved in pyridine to a volume of 100 ml), and take a glycerin bath at 95-100 ° C. It was heated in it for 1 hour. Then, the flask was taken out from the glycerin bath, allowed to cool, and then 1 ml of water was added and shaken. The flask was heated again in a glycerin bath for 10 minutes, allowed to cool, and then 5 ml of ethanol was added. A phenolphthalein-ethanol solution was added thereto, and the mixture was titrated with a 0.5 M (N / 2) potassium hydroxide-ethanol solution. The end point of the titration was when the purple color did not disappear for 30 seconds. In parallel with this test, a blank test, which is the same test except that no sample was used, was performed.

The hydroxyl value A (mgKOH / g) of the acrylic resin solution was calculated by the following formula.
A = [{(BC) x f x 28.05} / S] + D
[S: Sample usage (g), B: N / 2 potassium hydroxide-ethanol solution used in the blank test (ml), C: N / 2 potassium hydroxide-ethanol solution used in the main test ( ml), f: Factor of N / 2 potassium hydroxide-ethanol solution, D: Acid value (mgKOH / g)]

The acid value was measured as follows.
Accurately weigh 1 to 5 g of acrylic resin solution in a conical beaker, add 30 to 50 ml of a mixed solution of toluene / ethanol = 7/3 (volume ratio) to dissolve the resin solution, and add 2 phenolphthalein-ethanol solution as an indicator. Drops were added and titrated with N / 10 potassium hydroxide-ethanol solution. The acid value of the acrylic resin solution was calculated by the following formula, with the time when the redness of the liquid did not disappear for 30 seconds as the end point of the titration.
Acid value of acrylic resin solution = (B × f × 5.61) / S
(B: Amount of N / 10 potassium hydroxide-ethanol solution used (ml), f: Factor of N / 10 potassium hydroxide-ethanol solution, S: Mass of resin solution (g))

From the calculated hydroxyl value and the solid content ratio, the hydroxyl value in terms of solid content was calculated.
Hydroxy group value (solid content) = A × solid content ratio in acrylic resin solution (mass%) / 100

The values of "calc. Tg" shown in Table 1 below are values approximately calculated by the Fox formula.

[Production Example 1] <Synthesis of acrylic resin solution (A1)>
57.20 parts by mass of xylene (Xy) and 24.55 parts by mass of n-butanol (BuOH) were charged into the reactor as solvents to obtain a mixed solution. After raising the temperature of the mixed solution to 115 ° C. (reaction temperature) under a nitrogen stream, the mixed solution of the monomer components (styrene: 52.00 parts by mass, n-butyl methacrylate (BMA): 17.00 parts by mass, n-Butyl acrylate (BA): 16.20 parts by mass, 2-hydroxyethyl methacrylate (2-HEMA): 13.00 parts by mass, and methacrylic acid (MAA): 1.80 parts by mass) 100 parts by mass. A mixed solution with 1.00 parts by mass of an initiator (t-butylperoxy-2-ethylhexanoate) was added dropwise over 3 hours while maintaining the temperature at 115 ° C. After the dropping, heat is kept at the same temperature (115 ° C.) for 1 hour, and 0.4 parts by mass of t-butylperoxy-2-ethylhexanoate is added and kept warm for 2 hours to prepare an acrylic resin solution (A1). did.

[Production Examples 2 to 3] <Synthesis of acrylic resin solutions (A2) to (A3)>
Acrylic resin solutions (A2) to (A3) were prepared in the same manner as in the synthesis of the resin solution (A1) except that the mixed solution of the monomer components used was changed to the composition shown in Table 1. At that time, the amounts of the solvent and the initiator were appropriately adjusted for production.

[Example 1 (acrylic resin-based paint composition (E1))]
39.50 parts by mass of the acrylic resin solution (A1) of Production Example 1 was added to the container. Next, 1.00 parts by mass of "Toyoparax 150" was added as a plasticizer, and 0.20 parts by mass of "GPS-55" and 29.90 parts by mass of "precipitated barium sulfate 100" were further added as a pigment (C). , 1.00 part by mass of "Mitsubishi Carbon Black MA-100" and 3.50 part by mass of "Neolite SP-100" were added. Then, 9.00 parts by mass of "Swazole 1000", 8.78 parts by mass of xylene, and 3.20 parts by mass of n-butanol were added as solvents.

Then, glass beads GB605M (manufactured by Potters Barotini Co., Ltd.) were added, and these compounding components were mixed using a paint shaker (manufactured by Asada Iron Works Co., Ltd.). Next, the glass beads were removed, and as blocked isocyanate (B), 0.72 parts by mass of "Duranate MF-K60B", and as other additives, "Disparon A630-20X" 2.50 parts by mass, "Disparon OX-720". Add 0.50 part by mass and 0.20 part by mass of "1% toluene solution of Neostan U-100" and mix with a disper "HOMODISPER MODEL 2.5" (manufactured by Primix Co., Ltd.) to make an acrylic resin. A system coating composition (E1) was produced. A list of raw materials is shown in Table 3.

[Examples 2 to 10 and Comparative Example 1]
Acrylic resin-based paint compositions (E2) to (E10) and (C1) were prepared in the same manner as in Example 1 except that the types and blending amounts of each component were changed as shown in Table 2. The blending amount (parts by mass) of the resin solution (A) in Table 2 indicates the value of the resin solution.

The solid content (heating residue) of the coating composition was measured according to JIS K5601-1-2 (heating temperature: 125 ° C., heating time: 60 minutes).

[Evaluation methods]
<Bubble resistance test (Fukure resistance summer outdoor exposure test)>
Epoxy as an undercoat paint using an air spray coating machine (W-77, manufactured by Anest Iwata Co., Ltd.) on a sandblasted steel plate (150 mm x 70 mm x 2.3 mm, Sa2.5 or higher) at an ambient temperature of 23 ° C. The resin-based anticorrosion paint "Banno 500 Gray" (manufactured by China Paint Co., Ltd.) was coated with a wet film thickness of about 200 μm (dry film thickness of about 120 μm). After drying the anticorrosion paint for one day in an environment with a temperature of 23 ° C and a humidity of 55%, it was obtained in the above-mentioned Examples and Comparative Examples on an epoxy resin-based anticorrosion coating using an airless spray coating machine (X Force, manufactured by Graco). Each of the acrylic resin-based paint compositions obtained was coated with a wet film thickness of about 400 μm (dry film thickness of about 160 μm). Next, after drying the acrylic resin-based paint composition for one day in an environment of a temperature of 23 ° C. and a humidity of 55%, the same acrylic resin-based paint composition is further applied on the acrylic resin-based coating film using an airless spray coating machine (X Force). The object was coated with a wet film thickness of about 400 μm (dry film thickness of about 160 μm) and dried in an environment of a temperature of 23 ° C. and a humidity of 55% for 7 days to prepare a coated steel plate for testing.

The obtained test-coated steel sheet was placed horizontally with respect to the ground so as to be exposed to the most sunlight, and exposed outdoors for two months in the summer. Under such exposure conditions, the temperature of the steel sheet is usually as high as about 50 ° C. or higher.
The surface of the painted steel sheet after outdoor exposure for 2 months was visually confirmed, and the degree of blistering was evaluated on a scale of 6 points. In this evaluation, the coating film-forming surface of the sandblasted steel sheet was viewed in a plan view, and the evaluation was made according to ASTM D714-87 and based on the judgment criteria in Table 4 below. When the evaluation value was 4 or more, the coating film had good (pass) air bubble resistance. The results are shown in Table 5.

<Interval adhesion test>
Epoxy resin anticorrosion paint "Banno 500 Gray" (manufactured by China Paint Co., Ltd.) as an undercoat paint using an air spray coating machine (W-77) on a sandblasted steel plate similar to the above under an ambient temperature of 23 ° C. Was coated with a wet film thickness of about 200 μm (dry film thickness of about 120 μm). After drying the anticorrosion paint for one day in an environment with a temperature of 23 ° C and a humidity of 55%, the obtained coated plate with an undercoat coating was installed on an outdoor exposure table (on the premises of Otake Research Institute, China Paint Co., Ltd.). It was exposed outdoors for 3, 7, 15, 30, 60 or 90 days. Here, when the coating plate with the undercoat coating film obtained on the outdoor exposure table was installed, the undercoat coating film was fixed so as to face the south side at an angle of 45 ° with respect to the horizontal (ground). Hereinafter, outdoor exposure means that it was carried out under these conditions.

After lightly washing the coated plate exposed outdoors for each day with water and drying it, a wet film thickness of about 200 μm was applied to each of the acrylic resin-based paint compositions obtained in the above-mentioned Examples and Comparative Examples on the undercoat coating film using an applicator. By coating with (dry film thickness of about 80 μm) and drying in an environment of temperature 23 ° C. and humidity 55% for 7 days, coated steel sheets for interval adhesion test having different outdoor exposure days (intervals) were prepared.

The obtained coated steel sheet for interval adhesion test was exposed outdoors for 90 days. After the exposure, it was washed with water and dried in an environment of a temperature of 23 ° C. and a humidity of 55% for 1 day, and then a grid tape peeling test (2 mm × 2 mm, 25 squares) was performed.

In the grid tape peeling test, a cutter guide is used on the surface of the coated steel plate for interval adhesion test that has been exposed outdoors for 90 days, and the depth reaches the steel plate that is the base material, 6 vertical × 6 horizontal. I made a cut and made a 25-square grid. The cut spacing was 2 mm. Next, cellophane tape (registered trademark) was strongly pressure-bonded to the grid portion of the coating film, and the end of the cellophane tape was peeled off at a stretch at an angle of 90 ° with respect to the coating film surface. Then, the residual area ratio (%), which is the area of the coating film remaining on the steel sheet in the 25 squares, was calculated, and the interval adhesion was evaluated by the value of the residual area ratio (%). When the residual area ratio (%) was 50% or more, the coating film had good interval adhesion (pass). The remaining area ratio (%) is preferably 80% or more. The results are shown in Table 5.

The coating films obtained from the acrylic resin-based paint compositions obtained in Examples 1 to 10 had sufficient interval adhesion and bubble resistance. In particular, the coating film obtained from the acrylic resin-based coating composition having a blocked isocyanate (B) content of 1 to 15 parts by mass with respect to 100 parts by mass of the hydroxyl group-containing (meth) acrylic resin (A) adheres more at intervals. It was excellent in properties (Examples 1 to 9).
Further, the coating film obtained from the acrylic resin-based coating compositions obtained in Examples 1 to 7, 9 and 10 is a coating film even after the coating film and warm water at 50 ° C. are brought into contact with each other for 3 hours. No whitening was observed at all or almost, and the water resistance was excellent.

The bubble-resistant blister resistance of the coating film obtained by using the acrylic resin-based coating composition containing no blocked isocyanate (B) was remarkably low (Comparative Example 1).

From these results, it was found that a coating film having sufficient bubble resistance and interval adhesion can be obtained for the first time when the room temperature dry acrylic resin-based coating composition contains the blocked isocyanate (B).
Therefore, it can be said that the blocked isocyanate (B) has a function as a blister inhibitor of the coating film obtained by using the room temperature dry type coating composition.

Although the present invention has been described above with reference to Examples and the like, the present invention is not limited to the above examples, and for example, the present invention is not deviated from the gist of the present invention described in the claims. Design changes are acceptable.

Claims (10)

Contains hydroxyl group-containing (meth) acrylic resin (A) and blocked isocyanate (B) ,
The blocked isocyanate (B) is an active methylene-based blocked isocyanate.
The content of the blocked isocyanate (B) is 1 to 15 parts by mass with respect to 100 parts by mass of the hydroxyl group-containing (meth) acrylic resin (A).
Room temperature dry acrylic resin paint composition. The coating composition according to claim 1 , wherein the active methylene-based blocked isocyanate is a blocked isocyanate blocked with malonic acid diesters. The coating composition according to any one of claims 1 to 2 , wherein the hydroxyl group-containing (meth) acrylic resin (A) has a hydroxyl value of 10 to 100 mgKOH / g. The coating composition according to any one of claims 1 to 3 , which contains a pigment (C). The coating composition according to claim 4 , wherein the pigment volume concentration (PVC) in the coating composition is 25 to 40%. A coating film formed by using the coating composition according to any one of claims 1 to 5 . A base material with a coating film having the base material and the coating film according to claim 6 . The coated base material according to claim 7 , wherein the base material is a ship, a bridge, or a structure other than these. A hydroxyl group-containing (meth) acrylic resin (A) is formed on the surface of an undercoat coating film containing a resin having a group capable of binding to a hydroxyl group by using the coating composition according to any one of claims 1 to 5 . A laminated coating film having a coating film. With a coating film, which comprises a step of applying the coating composition according to any one of claims 1 to 5 to a substrate, and a step of drying the coated coating composition to form a coating film. Method of manufacturing a base material.