JP2021085013A - Epoxy resin-based coating composition, laminate coated film and method for repairing coated film - Google Patents

Abstract

To provide an epoxy resin-based coating composition that enables formation of a coated film, in which occurrence of coated film defects such as bulging, cracking, lifting (wrinkle) and pimples is suppressed, on a coated film containing a thermoplastic resin.SOLUTION: The epoxy resin-based coating composition is coated onto a coated film containing a thermoplastic resin and satisfies the following (I) or (II). (I) Storage elastic modulus at 20°C of the coated film with a dry film thickness of 150 μm formed from the epoxy resin-based coating composition is 1,200 MPa or more and 6,000 MPa or less, and aliphatic or alicyclic diglycidyl ether (C) is contained. (II) The epoxy resin-based coating composition contains aliphatic or alicyclic diglycidyl ether (C), an amine curing agent (B) and an epoxy compound (A) other than the aliphatic or alicyclic diglycidyl ether (C), and a ratio of a content of the diglycidyl ether (C) to a content of the epoxy compound (A) is 0.4-1.2.SELECTED DRAWING: None

Description

The present invention relates to an epoxy resin-based coating composition, a laminated coating film, and a method for repairing a coating film.

A coating film containing a thermoplastic resin typified by a (meth) acrylic resin is formed as a top coating film on a base material such as a ship or a bridge. However, a coating film containing such a thermoplastic resin, particularly a (meth) acrylic resin coating film, has a problem that coating film deterioration (coating film defect) such as blisters and cracks is likely to occur.

Therefore, when a defect occurs in the coating film containing the thermoplastic resin, it is usually required to repair it. At the time of this repair, if the coating film existing on the substrate (hereinafter, also referred to as "old coating film") can be reapplied as it is without removing the coating film (hereinafter, also referred to as "old coating film"), the old coating film can be removed. Such a repair method is desired because the process and cost required for the above can be significantly reduced.

However, when a new topcoat paint is reapplied to the old coating film containing the thermoplastic resin, coating film defects such as blisters, cracks, lifting (wrinkles), and swelling are likely to occur in the newly formed coating film, and the base material In addition, since it is not possible to impart a desired function, conventionally, a repair method of removing a deteriorated coating film portion and reapplying a new topcoat coating has been performed.
Further, it may be required to form a resin-based coating film different from the resin constituting the old coating film on the old coating film (hereinafter, also referred to as “repainting with a different coating film”). In this case, since coating film defects are particularly likely to occur in the different coating film, conventionally, only a repair method of removing all the old coating film and reapplying the topcoat paint has been performed.

In response to such a problem, Patent Document 1 describes an old coating film capable of forming a coating film that does not cause cracks or the like without completely peeling off the old coating film made of a rubber chloride paint or a vinyl paint. As a method for repairing a film, a method of coating two layers having an elongation rate within a predetermined range on the surface of an old coating film is described.

Japanese Unexamined Patent Publication No. 2009-160538

However, when a conventional paint such as the paint described in Patent Document 1 is formed on a coating film containing a thermoplastic resin, particularly a (meth) acrylic resin coating film, the formed coating film has a blister. It was found that coating film defects such as cracks, lifting (wrinkles), and puss were likely to occur, and the coating film defects could not be sufficiently suppressed.

The present invention has been made in view of the above problems, and a coating film containing a thermoplastic resin in which the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and swelling is suppressed is formed. An object of the present invention is to provide an epoxy resin-based coating composition that can be formed.

The present inventors have diligently studied to solve the above problems. As a result, they have found that the above problems can be solved according to the following configuration example, and have completed the present invention. A configuration example of the present invention is as follows.

[1] An epoxy resin-based coating composition that is coated on a coating film containing a thermoplastic resin, satisfies the following requirement (1), and contains an aliphatic or alicyclic diglycidyl ether (C).
Requirement (1): The storage elastic modulus of a coating film having a dry film thickness of 150 μm formed from the epoxy resin-based coating composition at 20 ° C. is 1,200 MPa or more and 6,000 MPa or less.

[2] The epoxy resin-based coating composition according to [1], which contains an amine curing agent (B) and an epoxy compound (A) other than the aliphatic or alicyclic diglycidyl ether (C).

[3] An aliphatic or alicyclic diglycidyl ether (C), an amine curing agent (B), and the aliphatic or alicyclic diglycidyl ether (B) coated on a coating film containing a thermoplastic resin. It contains an epoxy compound (A) other than C), and the ratio of the content of the aliphatic or alicyclic diglycidyl ether (C) to the content of the epoxy compound (A) is 0.4 to 1.2. An epoxy resin-based coating composition.

[4] The epoxy resin-based coating composition according to any one of [1] to [3], wherein the content of the solvent is 0 to 10% by mass.

[5] The epoxy resin-based coating composition according to any one of [1] to [4], wherein the thermoplastic resin is a (meth) acrylic-based resin.

[6] A coating film containing a thermoplastic resin and
A laminated coating film having a coating film formed from the epoxy resin-based coating composition according to any one of [1] to [5].

[7] A method for repairing a coating film, which comprises a step of forming a coating film from the epoxy resin-based coating composition according to any one of [1] to [5] on a coating film containing a thermoplastic resin.

According to the present invention, the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus was suppressed, and in particular, the occurrence of such coating film defects was suppressed even after a thermal cycle. The coating film can be formed on a coating film containing a thermoplastic resin, particularly on a (meth) acrylic resin coating film. Further, according to the present invention, it is possible to repaint with a different type of coating film different from the resin-based coating film forming the coating film formed on the base material.
That is, according to the present invention, a coating film (different coating film) in which coating film defects are suppressed while significantly reducing steps and costs as compared with the conventional case without removing the coating film formed on the substrate. Including) can be formed. Therefore, according to the present invention, it is possible to repair the coating film formed on the base material while significantly reducing the number of steps and costs as compared with the conventional case.

≪Epoxy resin-based paint composition≫
The epoxy resin-based coating composition according to the present invention (hereinafter, also referred to as “the present composition”) is coated on a coating film containing a thermoplastic resin.
(I) A composition that satisfies the following requirement (1) and contains an aliphatic or alicyclic diglycidyl ether (C), or
(II) The composition satisfies the following requirements (2), and preferably satisfies the following requirements (1) and (2).
Requirement (1): The storage elastic coefficient of a coating film having a dry thickness of 150 μm formed from the epoxy resin-based coating composition at 20 ° C. is 1,200 MPa or more and 6,000 MPa or less. Requirement (2): The epoxy resin-based paint. The composition contains an aliphatic or alicyclic diglycidyl ether (C), an amine curing agent (B), and an epoxy compound (A) other than the aliphatic or alicyclic diglycidyl ether (C). Moreover, the ratio of the content of the aliphatic or alicyclic diglycidyl ether (C) to the content of the epoxy compound (A) is 0.4 to 1.2. The present composition that satisfies the present composition is also referred to as "the present composition 1", and the present composition that satisfies the above (II) is also referred to as "the present composition 2".

Hereinafter, the "coating film containing a thermoplastic resin" on which the present composition is coated is also referred to as an "old coating film", and the coating film formed from the present composition is also referred to as a "main coating film".
The "old coating film" in the present invention refers to a coating film that is the object to which the composition is applied and is present on the substrate before the composition is applied. The old coating film includes not only a deteriorated coating film in which the coating film is deteriorated (coating film defect) due to aging or use after the coating film is formed, but also a coating film in which the coating film is not deteriorated. .. In the latter case, for example, a coating film containing a thermoplastic resin may be mistakenly formed, and the present composition may be applied for repair thereof.

According to this composition, a laminated coating film in which the present coating film is laminated on the old coating film can be obtained. In the laminated coating film, the present coating film may be used as a top coat depending on the base material on which the laminated coating film is formed, and one or more other coating films (hereinafter, hereinafter) are further applied on the main coating film. (Also referred to as “top coat”) may be formed.
Hereinafter, when the present coating film is used as a top coat, a laminate of the old coating film and the main coating film is used, and when the top coating film is further formed, the old coating film, the main coating film and the top coating film are used. The laminated body of is also referred to as "this laminated coating film".

The storage elastic modulus of the coating film formed from the present composition 1 at 20 ° C. is 1,200 to 6,000 MPa, and the storage elastic modulus of the coating film formed from the present composition 2 at 20 ° C. is preferably 7, It is 000 MPa or less, more preferably 6,000 MPa or less, and preferably 1,200 MPa or more.
The storage elastic modulus of the coating film formed from the present composition at 20 ° C. is more preferably 5,000 MPa or less, and particularly preferably 4,800 MPa or less. The lower limit of the storage elastic modulus is not particularly limited, but is more preferably 1,500 MPa or more, still more preferably 1800 MPa or more.
When the storage elastic modulus of the present coating film is within the above range, the present laminated coating film in which the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus is suppressed can be easily obtained. Further, even if the old coating film is a deteriorated coating film having blisters, cracks, etc., it is possible to form the present laminated coating film in which the occurrence of blisters, cracks, etc. is suppressed.
If the storage elastic modulus of the present coating film is below the above range, the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus tends to be unable to be suppressed, and the storage elastic modulus of the main coating film is within the above range. If it exceeds, the coating film tends to be hard and brittle.
Specifically, the storage elastic modulus can be measured by the method described in Examples described later.
The storage elastic modulus can be controlled, for example, by adjusting the amount of the epoxy compound (A) in the composition and the aliphatic or alicyclic diglycidyl ether (C).

The present composition may be a one-component type composition, but is preferably a two-component type or higher composition. In particular, in the case of the present composition 2, it is usually a two-component type or more composition containing a main ingredient component containing an epoxy compound (A) and a curing agent component containing an amine curing agent (B). Further, if necessary, a composition of three or more components containing other components other than the main component and the curing agent component may be used.
These main agent components, curing agent components and other components are usually stored, stored, transported, etc. in separate containers, and are mixed and used immediately before use.

<Coating film containing thermoplastic resin>
The coating film containing a thermoplastic resin (old coating film) refers to a coating film containing a thermoplastic resin, which is the same coating film as the top coating film formed on a base material such as a ship or a bridge. Say that. The proportion of the thermoplastic resin contained in the coating film containing the thermoplastic resin is not particularly limited, but is preferably 50% by mass or more.
The old coating film may be a laminate of two or more layers.

The thermoplastic resin in the old coating film is not particularly limited, and examples thereof include conventionally known thermoplastic resins used as a base material for ships, bridges, and the like. Specific examples of the thermoplastic resin include polyester-based resin, (meth) acrylic-based resin, styrene-based resin, vinyl chloride-based resin, vinyl acetate-based resin, chlorinated polyolefin, and synthetic rubber.
The "(meth) acrylic" in the present invention is a concept that includes acrylic, methacrylic, or both acrylic and methacrylic.

Among these, blister, crack, lifting (wrinkle), middle pus, etc. without removing the old coating film (hereinafter also referred to as "acrylic old coating film") formed from the paint containing (meth) acrylic resin. Since it has not been easy in the past to form the present laminated coating film in which the occurrence of coating film defects is suppressed, particularly different types of coating film, the effect of the present invention is more exhibited. In particular, as the surface old coating film to be coated with this composition, an acrylic old coating film is preferable.

The (meth) acrylic resin-based coating composition forming the old acrylic coating film is not particularly limited, and for example, JP-A-2016-1800, JP-A-2018-44162, JP-A-2019-56064, etc. It may be a coating composition prepared based on the above description, or it may be a commercially available product such as an acrylic series manufactured by China Paint Co., Ltd.

The thickness of the old coating film is not particularly limited. When the old coating film is a laminate of two or more layers, the thickness of the old coating film is the sum of the respective layers.

<Epoxy compound (A)>
The epoxy compound (A) is not particularly limited as long as it is a compound having an epoxy group other than the glycidyl ether (C) and the silane coupling agent described later, but for example, a polymer containing two or more epoxy groups in the molecule. Alternatively, an oligomer, a polymer or an oligomer produced by a ring-opening reaction of the epoxy group thereof can be mentioned.
The epoxy compound (A) may be used alone or in combination of two or more.

Examples of the epoxy compound (A) include bisphenol type epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, novolak type epoxy resin, cresol type epoxy resin, alkylphenol type epoxy resin, and dimer acid. Examples thereof include modified epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and epoxidized oil-based epoxy resins.
Among these, bisphenol type epoxy resin and alkylphenol type epoxy resin are preferable, and bisphenol A type epoxy resin is preferable from the viewpoint that the present coating film having excellent adhesion to the old coating film and further having corrosion resistance can be easily obtained. , Bisphenol F type epoxy resin and alkylphenol type epoxy resin are more preferable, and bisphenol A type epoxy resin and bisphenol F type epoxy resin are particularly preferable.

Specific examples of the epoxy compound (A) include epichlorohydrin-bisphenol A epoxy resin (bisphenol A diglycidyl ether type); epichlorohydrin-bisphenol AD epoxy resin; epichlorohydrin-bisphenol F epoxy resin; epoxy novolac resin; 3, Alicyclic epoxy resin obtained from 4-epoxyphenoxy-3', 4'-epoxyphenylcarboxymethane, etc .; at least one of the hydrogen atoms bonded to the benzene ring in the epichlorohydrin-bisphenol A epoxy resin is replaced with a bromine atom. Brominated epoxy resin obtained; an aliphatic epoxy resin obtained from epichlorohydrin and an aliphatic dihydric alcohol; a polyfunctional epoxy resin obtained from epichlorohydrin and tri (hydroxyphenyl) methane can be mentioned.

Examples of the bisphenol type epoxy resin include bisphenol A type and bisphenol F type epoxy resins, modified bisphenol type epoxy resins such as dimer acid modification and polysulfide modification, and hydrogenated products of these epoxy resins.

Examples of the bisphenol A type epoxy resin include bisphenol A diglycidyl ether, bisphenol A (poly) propylene oxide diglycidyl ether, bisphenol A (poly) ethylene oxide diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and hydrogenated bisphenol A. Examples thereof include condensed polymers such as bisphenol A type diglycidyl ethers such as (poly) propylene oxide diglycidyl ether and hydrogenated bisphenol A (poly) ethylene oxide diglycidyl ether.

The epoxy compound (A) can be used at room temperature (15 to 15 to) because a high-solid type coating composition can be easily prepared, and a present coating film having excellent adhesion to the old coating film can be easily formed. A liquid or semi-solid form at a temperature of 25 ° C., the same applies hereinafter) is preferable, and a liquid form is more preferable, and the viscosity measured at 25 ° C. exceeds 1,000 mPa · s based on JIS K 7233 20, Those of 000 mPa · s or less are particularly preferable.

The epoxy equivalent of the epoxy compound (A) is preferably 150 to 1,000, more preferably 150 to 1,000, from the viewpoints that the present coating film having excellent adhesion to the old coating film and corrosion resistance can be easily obtained. It is 150 to 800, particularly preferably 150 to 700.
The epoxy equivalent is calculated based on JIS K 7236: 2001.

As the epoxy compound (A), a compound obtained by synthesizing by a conventionally known method may be used, or a commercially available product may be used.
As the commercially available products, "E-028" (manufactured by Otake Meishin Kagaku Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 180 to 190, solid content 100%), "jER807" (manufactured by Otake Meishin Kagaku Co., Ltd., epoxy equivalent 180 to 190, solid content 100%), as liquid at room temperature Mitsubishi Chemical Co., Ltd., bisphenol F type epoxy resin, epoxy equivalent 160-175, solid content 100%), "E-028-90X" (Otake Meishin Kagaku Co., Ltd., bisphenol A type epoxy resin xylene solution (828 type epoxy resin solution, epoxy equivalent 200-210, solid content 90%), "HP-820" (manufactured by DIC Co., Ltd., alkylphenol type epoxy resin, epoxy equivalent 150-200, solid content 100%) and the like. As a semi-solid material at room temperature, "jER834" (manufactured by Mitsubishi Chemical Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 230-270, solid content 100%), "E-834-85X" (Akira Otake) Examples thereof include a xylene solution of bisphenol A type epoxy resin manufactured by Shinkagaku Co., Ltd. (834 type epoxy resin solution, epoxy equivalent 270-320, solid content 85%), and "jER1001" (solid at room temperature) Mitsubishi Chemical Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 450-500, solid content 100%), "E-001-75" (Otake Meishin Kagaku Co., Ltd., bisphenol A type epoxy resin xylene solution (1001 type epoxy resin solution), epoxy equivalent 600 to 660, solid content 75%) and the like.

The content of the epoxy compound (A) with respect to 100% by mass of the solid content (components other than the solvent) of the present composition is excellent in adhesion to the old coating film, and the present coating film having corrosion resistance can be easily obtained. From the above points, it is preferably 5 to 40% by mass, more preferably 10 to 30% by mass.
Further, when the present composition is a two-component coating composition composed of a main component and a curing agent component, the epoxy compound (A) is contained in the main component and the epoxy in 100% by mass of the solid content of the main component is contained. The content of the compound (A) is preferably 5 to 80% by mass, more preferably 5 to 50% by mass for the same reason as described above.

<Amine hardener (B)>
The amine curing agent (B) is not particularly limited as long as it is an amine compound other than a tertiary amine (an amine compound having only a tertiary amino group), but is an aliphatic, alicyclic, aromatic or heterocyclic amine. Amine compounds such as hardeners are preferred. These amine compounds are distinguished by the type of carbon to which the amino group is bonded. For example, the aliphatic amine curing agent means a compound having at least one amino group bonded to the aliphatic carbon. ..
The amine curing agent (B) may be used alone or in combination of two or more.

Examples of the aliphatic amine curing agent include alkylene polyamines, polyalkylene polyamines, and alkylaminoalkylamines.

Examples of the alkylene polyamine include _{compounds represented by the formula: "H 2} N-R ^1- NH ₂ " (R ¹ is a divalent hydrocarbon group having 1 to 12 carbon atoms). Specifically, methylenediamine, ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7- Examples thereof include diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane and trimethylhexamethylenediamine.

Examples of the polyalkylene polyamine include the formula: "H ₂ N- (C _m H _2m NH) _n H" (m is an integer of 1 to 10. n is an integer of 2 to 10, preferably 2). (It is an integer of ~ 6), and specifically, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tripropylenetetramine, tetraethylenepentamine, tetrapropylenepentamine, pentaethylenehexamine, Examples thereof include nonaethylenedecamine, bis (hexamethylene) triamine, and triethylene-bis (trimethylene) hexamine.

Examples of other aliphatic amine curing agents include tetra (aminomethyl) methane, tetrakis (2-aminoethylaminomethyl) methane, 1,3-bis (2'-aminoethylamino) propane, and tris (2-amino). Ethyl) amine, bis (cyanoethyl) diethylenetriamine, polyoxyalkylenepolyamine (particularly diethyleneglycolbis (3-aminopropyl) ether), bis (aminomethyl) cyclohexane (1,3-BAC), isophoronediamine, mensendiamine (MDA) ), O-Xylylenediamine, m-Xylylenediamine (MXDA), p-xylylenediamine, bis (aminomethyl) naphthalene, bis (aminoethyl) naphthalene, 1,4-bis (3-aminopropyl) piperazine, Examples thereof include 1- (2'-aminoethyl piperazine) and 1- [2'-(2''-aminoethylamino) ethyl] piperazine.

Specific examples of the alicyclic amine curing agent include cyclohexanediamine, diaminodicyclohexylmethane (particularly 4,4'-methylenebiscyclohexylamine (PACM)), 4,4'-isopropyridenebiscyclohexylamine, and norbornane. Examples thereof include diamine and 2,4-di (4-aminocyclohexylmethyl) aniline.

Examples of the aromatic amine curing agent include bis (aminoalkyl) benzene, bis (aminoalkyl) naphthalene, and aromatic polyamine compounds having two or more primary amino groups bonded to a benzene ring.
More specifically, as this aromatic amine curing agent, phenylenediamine, naphthalenediamine, diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, 4,4'-diaminodiphenyl ether, 4,4'- Diaminobenzophenone, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, diaminodiethylphenylmethane, 2,4'-diaminobiphenyl, 2,3'-dimethyl-4,4 Examples thereof include'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl and the like.

Examples of the heterocyclic amine curing agent include 1,4-diazacycloheptane, 1,11-diazacycloeikosan, and 1,15-diazacyclooctakosan.

Further, as the amine curing agent (B), a modified product of the above-mentioned amine curing agent, for example, a fatty acid modified product such as polyamide amine, an amine adduct with an epoxy compound, a Mannich modified product (eg, phenalkamine, phenalcamide), and Michael addition. Examples include compounds, ketimine, and argimine.

As the amine curing agent (B), an aliphatic or alicyclic amine curing agent, an epoxyadduct of an aliphatic or alicyclic amine, and a Mannig modified product of an aliphatic or alicyclic amine are preferable, and fat. Epoxyadducts of group-based or alicyclic amines and Mannig modifications of aliphatic or alicyclic amines are more preferred, with aliphatic or alicyclic amine epoxyadducts particularly preferred.
Further, as these aliphatic or alicyclic amines, amines having an alicyclic ring, particularly a cyclohexane ring, are preferable.
When these amine curing agents are used as the amine curing agent (B), the present coating film having excellent oil resistance and chemical resistance, excellent adhesion to the old coating film, and excellent corrosion resistance and water resistance can be easily produced. Can be obtained.

The epoxy adduct may be an amine such as, for example, an aliphatic or alicyclic amine curing agent, a fatty acid modified product of an aliphatic or alicyclic amine curing agent, or a Mannig modified product of an aliphatic or alicyclic amine curing agent. It is obtained by reacting one or more compounds with one or more epoxy resins such as bisphenol A type epoxy resin.
The amount of the epoxy resin used with respect to 100 parts by mass of the amine compound is preferably 5 to 800 parts by mass, more preferably 100 to 800 parts by mass, and particularly preferably 300 to 800 parts by mass.

Examples of the epoxy resin include (alkyl) phenols such as bisphenol A diglycidyl ether; bisphenol F diglycidyl ether; styrene oxide; cyclohexene oxide; phenol, cresol, and t-butylphenol, butanol, 2-ethylhexanol, and carbon number. Glysidyl ethers such as alcohols 8 to 14; alkyl glycidyl ethers (eg, Epodil 759 [manufactured by Evonik]) can be mentioned.

The amine curing agent (B) may be obtained by synthesizing it by a conventionally known method, or may be a commercially available product.
Examples of the commercially available product include "PH-836" (manufactured by PTI Japan Co., Ltd.), which is an epoxy adduct of an aliphatic amine, and "AD-71" (Akira Otake), which is a separable epoxy adduct of an aliphatic amine. Shinkagaku Co., Ltd.), "Ancamine 2143" (manufactured by EVONIK), which is an epoxy resin adduct-modified product of alicyclic amine, and "PA, which is a dehydration condensate of aliphatic polyamine and dimer acid). Examples thereof include "-66S" (manufactured by Meishin Otake Chemical Co., Ltd.) and "Cardolite CM-5055" (manufactured by Cardlite Co., Ltd.) which is a phenalkamine (a dehydration condensate of an aliphatic polyamine with formalin and cardanol).

The active hydrogen equivalent of the amine curing agent (B) is preferably 50 or more, more preferably 100 or more, and preferably 1,000 or less, from the viewpoint that the present coating film having excellent corrosion resistance can be easily obtained. , More preferably 500 or less.

The reaction ratio of the amine curing agent (B) calculated by the following formula (1) is preferably 0 from the viewpoint that the present coating film having excellent corrosion resistance, coating film strength and drying property can be easily obtained. It is desirable to use it in an amount such that it is 0.3 or more, more preferably 0.4 or more, preferably 1.0 or less, and more preferably 0.9 or less.

Reaction ratio = {(Amine curing agent (B) compounding amount / Amine curing agent (B) active hydrogen equivalent) + (Amine compound (A) -reactive component compounding amount / Epoxy compound (A) Functional group equivalent of a component that is reactive with respect to)} / {(blending amount of epoxy compound (A) / epoxy equivalent of epoxy compound (A)) + (reactive with amine curing agent (B)) Compounding amount of component / Functional group equivalent of component having reactivity with amine curing agent (B))} ... (1)

Here, examples of the "component having reactivity with the amine curing agent (B)" in the formula (1) include an aliphatic or alicyclic diglycidyl ether (C) and a silane coupling agent described later. As the "component having reactivity with the epoxy compound (A)", for example, a silane coupling agent described later can be mentioned. The "functional group equivalent" of each of the components means the mass (g) per 1 mol functional group obtained by dividing the mass of 1 mol of these components by the number of mols of the functional groups contained therein.
As the silane coupling agent described later, a silane coupling agent having an amino group or an epoxy group can be used as the reactive group. Therefore, depending on the type of the reactive group, the silane coupling agent may be the epoxy compound (A). It is necessary to determine whether it is reactive with respect to or with respect to the amine curing agent (B) and calculate the reaction ratio.

When the present composition is a two-component composition composed of a main component and a curing agent component, the amine curing agent (B) is included in the curing agent component. The viscosity of this curing agent component at 25 ° C. measured with an E-type viscometer is preferably 100,000 mPa · s or less, more preferably 100,000 mPa · s or less, from the viewpoint of obtaining the present composition having excellent handleability and coating workability. Is 50 to 10,000 mPa · s.

<Alicyclic or alicyclic diglycidyl ether (C)>
The aliphatic or alicyclic diglycidyl ether (C) is not particularly limited, and conventionally known compounds can be used.
Since the present composition is characterized by using diglycidyl ether, the above-mentioned effect is exhibited. On the other hand, when only monoglycidyl ether is used without using diglycidyl ether, the obtained composition easily dissolves the old coating film, so that coating film defects such as lifting are likely to occur, and only triglycidyl ether is used. In this case, it was found that the viscosity of the obtained composition tends to be high, so that the composition tends to be difficult to paint.
Further, since the structure of the diglycidyl ether portion is important for the diglycidyl ether (C), any of the aliphatic type and the alicyclic type can solve the above problem. In the aromatic system, the viscosity of the obtained composition tends to be high, and the hardness of the obtained coating film tends to be high.
The diglycidyl ether (C) may be used alone or in combination of two or more.

The viscosity of the diglycidyl ether (C) is preferably 1,000 mPa · s or less, more preferably 500 mPa · s or less, still more preferably 500 mPa · s or less, from the viewpoint that the present composition having excellent coating workability can be easily obtained. Is 100 mPa · s or less.
Hereinafter, the viscosity of diglycidyl ether (C) refers to the viscosity measured at 25 ° C. based on JIS K 7233.

Specific examples of the aliphatic diglycidyl ether (C) include 1,4-butanediol diglycidyl ether (viscosity: 13 mPa · s) and 1,6-hexanediol diglycidyl ether (Gly-O-). _{(CH 2) 6 -O-Gly} , Gly: glycidyl group) (viscosity: 17 mPa · s), neopentyl glycol diglycidyl ether _{(Gly-O-CH 2 -C} (CH 3) 2 -CH 2 -O-Gly , Gly: same as above) (viscosity: 14 mPa · s), propylene glycol diglycidyl ether (viscosity: 25 mPa · s), tripropylene glycol diglycidyl ether (viscosity: 30 mPa · s), polypropylene glycol diglycidyl ether (viscosity: 75 mPa · s) s), polyglycol diglycidyl ether (viscosity: 35 mPa · s), glycerin diglycidyl ether (viscosity: 150 mPa · s).

Specific examples of the alicyclic diglycidyl ether (C) include cyclohexanedimethanol diglycidyl ether (viscosity: 60 mPa · s).

As the diglycidyl ether (C), the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus was suppressed, and in particular, the occurrence of such coating film defects even after a cold heat cycle. The aliphatic diglycidyl ether is preferable from the viewpoint that the present laminated coating film in which the amount of water is suppressed can be easily formed.
The epoxy equivalent of the diglycidyl ether (C) is preferably 100 to 300, more preferably 120 to 220.

With respect to the content of the diglycidyl ether (C) with respect to 100% by mass of the solid content of the present composition, the present coating film having the storage elastic modulus in the above range can be easily obtained, and the occurrence of the coating film defects is suppressed. From the viewpoint that the laminated coating film can be easily formed, the content is preferably 1 to 30% by mass, more preferably 5 to 20% by mass.

The ratio (C / A) of the content of the diglycidyl ether (C) to the content of the epoxy compound (A) in the composition 1 is preferably 0.1 to 1.5, more preferably 0. .2 to 1.5, more preferably 0.4 to 1.2, and particularly preferably 0.5 to 1.0. The ratio (C / A) of the content in the composition 2 is 0.4 to 1.2, preferably 0.5 to 1.0.
When the content ratio (C / A) is in the above range, the present coating film having the storage elastic modulus in the above range can be easily obtained, and the main laminated coating film in which the occurrence of the coating film defects is suppressed is suppressed. Can be easily formed.

<Additives>
The present composition may contain, if necessary, a silane coupling agent, a pigment, an anti-sagging agent (precipitation inhibitor), an antifoaming agent, a curing accelerator such as a tertiary amine, a plasticizer, a leveling agent, an inorganic dehydrating agent, and ultraviolet rays. Additives such as stabilizers, ultraviolet absorbers, antiaging agents, dispersants, antifouling agents, and solvents may be contained within a range that does not impair the object of the present invention.
Examples of these additives include those conventionally known.
Each of the additives may be used alone or in combination of two or more.

[Silane coupling agent]
By using the silane coupling agent, not only the adhesion of the obtained main coating film to the old coating film can be further improved, but also the corrosion resistance such as salt water resistance of the obtained main coating film can be improved. Can be done.

The silane coupling agent is not particularly limited, and conventionally known compounds can be used, but they have at least two functional groups in the same molecule to improve the adhesion to the old coating film and the viscosity of the present composition. is preferably a compound capable of contributing to the reduction or the like, for example, the formula: _{"X-SiMe n} Y _3-n" [n is 0 or 1, X is the reaction reactive groups capable of organic (e.g. an amino group , Vinyl group, epoxy group, mercapto group, halogen group, a group in which a part of the hydrocarbon group is substituted with these groups, or a part of the group in which a part of the hydrocarbon group is substituted with an ether bond or the like is these. Me represents a methyl group and Y represents a hydrolyzable group (eg, an alkoxy group such as a methoxy group or an ethoxy group). ] Is more preferable.

The silane coupling agent is preferably a compound having an epoxy group or an amino group as a reactive group, and specifically, "KBM-403" (γ-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.). ), "Sila Ace S-510" (manufactured by JNC Co., Ltd.), "KBM-603" (3- (2-aminoethylamino) propyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) and the like.

When the present composition contains a silane coupling agent, the silane coupling agent with respect to 100% by mass of the solid content of the present composition can be easily obtained because the present coating film having better adhesion to the old coating film can be easily obtained. The content of is preferably 0.2 to 3% by mass, more preferably 0.5 to 2% by mass.

[Pigment]
The composition preferably contains a pigment.
The pigment is not particularly limited, and conventionally known pigments can be used, and specific examples thereof include extender pigments, coloring pigments, and rust preventive pigments.

The extender pigment is not particularly limited, but for example, zinc oxide, silica, talc, mica, clay, bentonite, potassium feldspar, wollastonite, glass flakes, calcium carbonate, kaolin, alumina white, white carbon, aluminum hydroxide, and the like. Examples include magnesium carbonate and barium sulfate (eg, barite powder). Among these, talc, silica, mica, clay, calcium carbonate, kaolin, barium sulfate, and potassium feldspar are preferable.

The coloring pigment is not particularly limited, and examples thereof include inorganic pigments such as carbon black, titanium dioxide, petals, iron oxide, iron hydroxide, and ultramarine blue, and organic pigments such as phthalocyanine blue and phthalocyanine green.

The rust preventive pigment is not particularly limited, but for example, zinc powder, zinc alloy powder, zinc phosphate compound, calcium phosphate compound, aluminum phosphate compound, magnesium phosphate compound, zinc phosphite compound, sub Calcium phosphate compound, aluminum phosphite compound, strontium phosphite compound, aluminum tripolyphosphate compound, zinc tripolyphosphate compound, zinc molybdenate compound, aluminum molybdenate compound, cyanamide zinc compound, borate Examples include compounds, nitro compounds and composite oxides.

When the present composition contains a pigment, the present coating film having the storage elastic modulus in the above range can be easily obtained, and the present laminated coating film in which the occurrence of the coating film defects is suppressed can be easily formed. The content of the pigment with respect to 100% by mass of the solid content of the present composition is preferably 10 to 60% by mass, more preferably 20 to 60% by mass, from the viewpoint of being able to do so.
For the same reason, the pigment volume concentration (PVC) in the present composition is preferably 10 to 50%, more preferably 10 to 40%.

The PVC refers to the total volume concentration of all the pigments in the composition, and can be specifically obtained from the following formula (2).
PVC [%] = total volume of all pigments in the composition x 100 / volume of solids in the composition ... (2)

The volume of the solid content in the present composition can be calculated from the mass and the true density of the solid content of the present composition. 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. The measured value can be calculated, for example, by separating the pigment and other components from the solid content of the present composition and measuring the mass and true density of the separated pigment.

[Anti-sauce agent (anti-sedimentation agent)]
The present composition may contain a sagging preventive agent (sedimentation inhibitor) from the viewpoint that the present composition having excellent sagging resistance can be obtained.
Examples of the anti-dripping agent include organic clay waxes such as stearate salts of Al, Ca and Zn, lecithin salts and alkyl sulfonates, polyethylene waxes, amido waxes, hydrogenated castor oil waxes and polyethylene oxide waxes. Be done.

When the present composition contains a sagging preventive agent, the content of the sagging preventive agent with respect to 100% by mass of the solid content of the present composition is preferable from the viewpoint that the present composition having excellent sagging resistance can be obtained. It is 0.1 to 2% by mass, more preferably 0.5 to 1.5% by mass.

[Defoamer]
The present composition preferably contains an antifoaming agent from the viewpoints of suppressing the generation of air bubbles and improving the appearance of the obtained laminated coating film.
As the defoaming agent, for example, various conventionally known defoaming agents such as polymer-based, acrylic-based, silicone-based, mineral oil-based, and olefin-based defoaming agents can be used. Among them, polymer-based and olefin-based defoaming agents can be used. Foaming agents are preferred.

Examples of such antifoaming agents include "BYK-1788", "BYK-1790", and "BYK-1794" manufactured by Big Chemie Japan Co., Ltd .; "AFCONA-2290" manufactured by AFCONA ADDITIVE, and manufactured by ExconMobile Chemical Company. Examples of products such as "SpectraSyn 40", "SpectraSin Elite150", and "SpectraSin Elite65".

When the present composition contains an antifoaming agent, the content of the antifoaming agent with respect to 100% by mass of the solid content of the present composition is preferably 0.01 to 4% by mass, more preferably 0.05 to 2% by mass. Is.

[solvent]
The solvent is not particularly limited, and can be appropriately selected and used depending on the coating method and coating workability of the present composition, but the present composition preferably contains no solvent as much as possible.

Examples of the solvent include xylene, toluene, MIBK (methyl isobutyl ketone), 1-methoxy-2-propanol, MEK (methyl ethyl ketone), butyl acetate, n-butanol, IBA (isobutyl alcohol), IPA (isopropyl alcohol), and minerals. Examples include spirit and benzyl alcohol.

The content of the solvent with respect to 100% by mass of the present composition is preferably 0 to 10% by mass, more preferably from the viewpoint that the present laminated coating film in which the occurrence of the coating film defects is suppressed can be easily formed. Is 0 to 5% by mass, particularly preferably 0 to 3% by mass.

When the content of the solvent is within the above range, it is possible to suppress the adverse effect of the solvent on the painting environment and the painting operator, and the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus. It is possible to easily obtain the present laminated coating film in which the amount is further suppressed. In particular, when the surface old coating film on which the composition is coated is an acrylic old coating film, the acrylic resin is usually inferior in solvent resistance, so a general solvent-based paint is applied on such an acrylic old coating film. Then, it was found that the main laminated coating film formed by melting the old coating film was liable to have coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus. On the other hand, when the content of the solvent is within the above range, the occurrence of coating film defects such as blisters, cracks, lifting (wrinkles) and middle pus is further suppressed even when coating on the old acrylic coating film. The present laminated coating film can be easily obtained.

≪Laminated coating film≫
The laminated coating film according to the present invention has the old coating film and the main coating film, and is usually a laminate in which the base material, the old coating film, and the present coating film are laminated in this order, and is necessary. As a result, the topcoat film is further provided on the opposite side of the main coating film from the old coating film.
Further, the laminated coating film is a conventionally known primary rust preventive paint (shop primer) between the base material and the old coating film, if necessary, from the viewpoint of corrosion resistance, weldability, shearing property, etc. of the base material. Etc., and other films coated with a primer or the like and dried (cured) may be provided.
The old coating film, the main coating film, the top coating film and other films that can be contained in these laminated coating films may each have one layer or two or more layers.

The laminated coating film includes a method including a step of forming a coating film from the present composition on the old coating film, specifically, a step of coating the present composition on the old coating film and drying (curing) the composition. It is preferably produced by the method. It can be said that this method for producing a laminated coating film is a method for repairing a coating film, specifically, a method for repairing an old coating film.
According to the present invention, since the present coating film in which the occurrence of coating film defects is suppressed can be formed on the old coating film without removing the old coating film, the process, cost, etc. can be significantly reduced. Therefore, the present coating film may be formed without removing the old coating film. If the thickness of the old coating film is excessively thick, a part of the old coating film may be removed.

The base material is not particularly limited, but a base material made of steel, non-ferrous metal (zinc, aluminum, etc.), stainless steel, etc. is preferable, and a ship, land structure, bridge, or other structure made of these, particularly a ship, is used. More preferred.

Further, as the base material, the surface of the base material is treated as necessary in order to remove rust, oil and fat, moisture, dust, slime, salt and the like, and to improve the adhesion of the obtained coating film. For example, a blast treatment (ISO8501-1 Sa2 1/2), a friction method, a treatment for removing oil and dust by degreasing) and the like may be used.

The method for applying the present composition onto the old coating film is not particularly limited, and conventionally known methods can be used without limitation, but they are excellent in workability, productivity, etc., and can be applied to a large-area substrate. Spray coating is preferable because it can be easily coated and the effects of the present invention can be more exerted.

The conditions for spray coating may be appropriately adjusted according to the thickness of the main coating film to be formed. However, during airless spraying, for example, the primary (air) pressure: about 0.4 to 0.8 MPa, the secondary (paint). ) Pressure: The coating conditions may be set to about 10 to 26 MPa and the gun moving speed to about 50 to 120 cm / sec.

The film thickness of the present coating film may be appropriately selected depending on the desired application, but is preferably 50 to 1,000 μm, more preferably 100 to 500 μm.

When forming the main coating film having such a film thickness, the main coating film having a desired thickness may be formed by one coating (one coating), or twice (more if necessary). By painting, the present coating film having a desired thickness may be formed.

The method for drying (curing) the composition is not particularly limited, and the composition may be dried (cured) by heating at about 5 to 60 ° C. in order to shorten the drying (curing) time. Usually, the composition is dried (cured) by leaving it at room temperature and in the air for about 1 to 14 days.

The topcoat paint for forming the topcoat coating film is not particularly limited, and is appropriately selected from conventionally known topcoat paints according to the base material and the use of the base material, and a conventionally known method according to the paint is used. A coating film may be formed.
This coating film not only has excellent adhesion to the old coating film, but also has excellent adhesion to the topcoat coating film formed on the old coating film. , Lifting (wrinkles) and coating film defects such as middle pus can be suppressed.
Therefore, the selectivity of the type of the topcoat coating film formed on the main coating film is not limited, and it is possible to easily recoat with a different resin-based coating film different from the resin constituting the old coating film.

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

[Examples 1 to 5 and Comparative Examples 1 to 3]
Each of the raw materials listed in the column of the main agent in Table 1 was added to the container in the amount (parts by mass) shown in Table 1, stirred with a high-speed disperser, and uniformly dispersed to prepare the main agent component.
Immediately before coating in the test below, the obtained main ingredient and the raw materials listed in the column of curing agent in Table 1 are mixed at the mixing ratio (mass ratio) shown in Table 1 to form an epoxy resin-based coating composition. Was prepared.
In Comparative Example 2, each of the raw materials listed in the column of the curing agent in Table 1 was added to the container in advance in the amount (parts by mass) shown in Table 1, and the mixture was stirred with a high-speed disperser to uniformly disperse. After that, it was mixed with the main ingredient.
Details of each component shown in Table 1 are as shown in Table 2.

<Storage modulus>
The epoxy resin-based coating composition obtained in the above Examples and Comparative Examples was coated on the release paper so that the obtained coating film had a dry film thickness of 150 μm, and dried at room temperature for 3 days. After that, a rectangular coating film having a long side of 40 mm and a short side of 8 mm was prepared from the release paper, and the coating film was used and DMA Q800 (manufactured by TA Instruments Japan Co., Ltd.) was used. The storage elastic modulus at 20 ° C. was measured. The measurement conditions were a vibration amplitude of 15.0 μm, a static load of 0.1000 N, a force track of 125.0%, and a minimum vibration load of 0.0100 N. The results are shown in Table 3.

<Blur resistance test>
On a blasted steel sheet of 150 mm x 70 mm x 1.6 mm (thickness), Vanno 500 (manufactured by China Paint Co., Ltd.), which is an epoxy resin anticorrosive paint, is applied so that the dry film thickness of the obtained coating film is 180 μm. A steel sheet with an anticorrosion coating film was prepared by drying at room temperature for 1 day.

On the anticorrosion coating film of the produced steel sheet with anticorrosion coating film, Acrylic 700 topcoat J (manufactured by China Paint Co., Ltd.), which is an acrylic resin-based topcoat paint, is applied so that the dry film thickness of the obtained coating film is 160 μm. A steel sheet with a topcoat coating film 1 was prepared by drying at room temperature for 1 day.

On the topcoat coating film 1 of the obtained steel sheet with the topcoat coating film 1, Acry 700 topcoat J is applied so that the dry film thickness of the obtained coating film is 160 μm, and dried at room temperature for one day to perform the topcoat coating. A steel sheet with a film 2 is prepared, and further, Acrylic 700 topcoat J is applied onto the topcoat coating film 2 so that the dry film thickness of the obtained coating film is 160 μm, and the topcoat is dried at room temperature for one day. A steel plate with coating film 3 was produced. By exposing the obtained steel sheet with the topcoat coating film 3 outdoors for 6 months, blisters were generated in the topcoat coating film 3.

The epoxy resin-based coating composition obtained in the above Examples and Comparative Examples is applied onto the topcoat coating film 3 of the steel sheet with the topcoat coating film 3 after outdoor exposure so that the dry film thickness of the obtained coating film is 150 μm. And dried at room temperature for 3 days to prepare a steel sheet with an epoxy topcoat coating.
The prepared steel sheet with an epoxy topcoat coating film was heated to 60 ° C., and after performing the following cooling and heating cycles (12 hours) for 120 cycles (60 days in total), the steel sheet was kept in a normal temperature environment and cooled to normal temperature.
Cold cycle: Hold at 60 ° C for 2 hours → Cool to 32 ° C over 1 hour → Cool to 5 ° C over 1 hour → Cool to -20 ° C over 1 hour → Hold at -20 ° C for 2 hours → Over 1 hour Heat to 0 ° C → Heat to 20 ° C over 1 hour → Hold at 20 ° C for 1 hour → Heat to 40 ° C over 1 hour → Heat to 60 ° C over 1 hour

The appearance of the obtained steel sheet with an epoxy topcoat coating film after the cooling and heating cycle was visually confirmed, and the case where there was no blister on the coating film surface was evaluated as ◯, and the case where blister occurred on the coating film surface was evaluated as x. The results are shown in Table 3.

<Crack resistance test>
Acrylic 700 topcoat ST (manufactured by China Paint Co., Ltd.), which is an acrylic resin-based topcoat, is applied to a steel sheet with an anticorrosion coating film produced in the same manner as in the blister resistance test, and the dry film thickness of the obtained coating film is 160 μm. A steel sheet with a topcoat coating film 1 was prepared by coating the sheet so that it would grow and drying at room temperature for 3 days.

Next, the following accelerated deterioration test was performed on the steel sheet with the topcoat coating film 1.
Using a UV lamp (manufactured by Toshiba Lighting & Technology Corporation, product number: FL40S.BLB), the topcoat coating film 1 is irradiated with ultraviolet rays for 2 days so ^{that the ultraviolet intensity becomes 3.2 mW / cm 2, and then JIS.} Brine was sprayed for 2 days according to K5600-7-1. Then, the steel sheet with the topcoat coating film 1 was heated to 60 ° C., and after performing the following cooling and heating cycles (12 hours) for 6 cycles (3 days in total), the steel sheet was kept in a normal temperature environment and cooled to normal temperature.
Cold cycle: Hold at 60 ° C for 2 hours → Cool to 32 ° C over 1 hour → Cool to 5 ° C over 1 hour → Cool to -20 ° C over 1 hour → Hold at -20 ° C for 2 hours → Over 1 hour Heat to 0 ° C → Heat to 20 ° C over 1 hour → Hold at 20 ° C for 1 hour → Heat to 40 ° C over 1 hour → Heat to 60 ° C over 1 hour

After the accelerated deterioration test, the topcoat coating film 1 of the steel sheet with the topcoat coating film 1 is coated with ACLI700 topcoat ST so that the dry film thickness of the obtained coating film is 160 μm, and dried at room temperature for 3 days. A steel sheet with a topcoat coating film 2 was prepared, and an accelerated deterioration test similar to the above was performed. Further, on the topcoat coating film 2 of the steel sheet with the topcoat coating film 2 after the accelerated deterioration test, Acry 700 topcoat ST is applied so that the dry film thickness of the obtained coating film is 160 μm, and dried at room temperature for 3 days. Then, a steel sheet with the topcoat coating film 3 was prepared, and the same accelerated deterioration test as described above was performed.

For example, on the outer surface of a ship such as a ferry (parts such as a deck and a superstructure portion), an acrylic resin-based topcoat coating film is formed on a base material on which an epoxy resin-based anticorrosion coating film is formed. Then, usually, the acrylic resin-based topcoat coating film is further coated on the formed acrylic resin-based topcoat coating film about once a year.
The steel sheet with the topcoat coating film 1 after the accelerated deterioration test corresponds to the ship one year after the new shipbuilding, and the steel sheet with the topcoat coating film 3 after the accelerated deterioration test corresponds to the ship three years after the new shipbuilding. Corresponds to.

Acrylic 800 topcoat (manufactured by China Paint Co., Ltd.), which is an acrylic resin-based topcoat, is applied onto the topcoat 3 of the steel sheet with the topcoat 3 after the accelerated deterioration test, and the dry film thickness of the obtained coating is 40 μm. A steel sheet with a topcoat coating film 4 was prepared by performing an accelerated deterioration test similar to the above for 3 cycles (21 days in total) after the coating was carried out at room temperature for 3 days.

The epoxy resin-based coating composition obtained in the above Examples and Comparative Examples was coated on the prepared topcoat coating film of the steel sheet with the topcoat coating film 4 so that the dry film thickness of the obtained coating film was 150 μm. A steel sheet with an epoxy topcoat coating was prepared by drying at room temperature for 1 day.

Acry 800 topcoat is applied onto the epoxy topcoat of the obtained steel sheet with an epoxy topcoat coating film so that the dry film thickness of the obtained coating film is 40 μm, and dried at room temperature for 3 days to obtain a topcoat coating film. A steel plate with 5 was produced.

After performing the accelerated deterioration test for 8 cycles (56 days in total) using the produced steel sheet with topcoat coating film 5, the appearance of the steel sheet with topcoat coating film 5 was visually confirmed, and there were no cracks on the coating film surface. The case was evaluated as ◯, and the case where cracks were generated on the coating film surface was evaluated as x. The results are shown in Table 3.

<Lifting resistance test>
On the anticorrosion coating film of the steel sheet with anticorrosion coating film produced in the same manner as the blister resistance test, Acry 700 topcoat ST was applied so that the dry film thickness of the obtained coating film was 160 μm, and dried at room temperature for 1 day. A steel plate with a topcoat coating film 1 was produced by allowing the coating film to be formed.

Acrylic 700 topcoat JMS (manufactured by China Paint Co., Ltd.), which is an acrylic resin-based topcoat, is applied onto the topcoat 1 of the obtained steel sheet with topcoat 1, and the dry film thickness of the obtained coating is 40 μm. A steel sheet with a top coat film 2 was prepared by coating the sheet and drying it at 60 ° C. for 1 day.

The epoxy resin-based coating composition obtained in the Examples and Comparative Examples was coated on the topcoat coating film 2 of the steel sheet with the topcoat coating film 2 so that the dry film thickness of the obtained coating film was 150 μm. A steel sheet with an epoxy topcoat coating was prepared by drying at room temperature for 1 day.

Acry 700 topcoat ST is applied onto the epoxy topcoat of the obtained steel sheet with an epoxy topcoat coating film so that the dry film thickness of the obtained coating film is 40 μm, and the coating film is dried at room temperature for one day to provide a topcoat coating. A steel plate with a film 3 was produced.

The appearance of the obtained steel sheet with the topcoat coating film 3 was visually confirmed, and the case where there was no lifting (wrinkles) on the coating film surface was evaluated as ◯, and the case where lifting occurred on the coating film surface was evaluated as x. The results are shown in Table 3.

<Different topcoat test>
The epoxy resin-based coating composition obtained in the above Examples and Comparative Examples was applied to a steel sheet with a topcoat coating film 3 produced in the same manner as in the crack resistance test so that the dry film thickness of the obtained coating film was 150 μm. And dried at room temperature for 1 day to prepare a steel sheet with an epoxy topcoat coating.

The produced steel sheet with an epoxy topcoat coating film is coated with Unimarin (manufactured by China Paint Co., Ltd.), which is a urethane resin-based topcoat paint, so that the dry film thickness of the obtained coating film is 40 μm, and dried at room temperature for 3 days. As a result, a steel plate with a topcoat coating film 4 was produced.

The prepared steel sheet with the topcoat coating film 4 was heated to 60 ° C., and after performing the following cooling and heating cycles (12 hours) for 120 cycles (60 days in total), the steel sheet was kept in a normal temperature environment and cooled to normal temperature.
Cold cycle: Hold at 60 ° C for 2 hours → Cool to 32 ° C over 1 hour → Cool to 5 ° C over 1 hour → Cool to -20 ° C over 1 hour → Hold at -20 ° C for 2 hours → Over 1 hour Heat to 0 ° C → Heat to 20 ° C over 1 hour → Hold at 20 ° C for 1 hour → Heat to 40 ° C over 1 hour → Heat to 60 ° C over 1 hour

The appearance of the obtained steel sheet with the topcoat coating film 4 after the cooling and heating cycle was visually confirmed, and if there were no blister, cracks or lifting on the coating film surface, ○, or any of blister, cracks and lifting on the coating film surface. The case where it occurred was evaluated as x. The results are shown in Table 3.

Claims (7)

An epoxy resin-based coating composition that is coated on a coating film containing a thermoplastic resin, satisfies the following requirement (1), and contains an aliphatic or alicyclic diglycidyl ether (C).
Requirement (1): The storage elastic modulus of a coating film having a dry film thickness of 150 μm formed from the epoxy resin-based coating composition at 20 ° C. is 1,200 MPa or more and 6,000 MPa or less. The epoxy resin-based coating composition according to claim 1, which contains an amine curing agent (B) and an epoxy compound (A) other than the aliphatic or alicyclic diglycidyl ether (C). Other than the aliphatic or alicyclic diglycidyl ether (C), amine curing agent (B), and the aliphatic or alicyclic diglycidyl ether (C) coated on a coating film containing a thermoplastic resin. The ratio of the content of the aliphatic or alicyclic diglycidyl ether (C) to the content of the epoxy compound (A) is 0.4 to 1.2. Epoxy resin-based paint composition. The epoxy resin-based coating composition according to any one of claims 1 to 3, wherein the content of the solvent is 0 to 10% by mass. The epoxy resin-based coating composition according to any one of claims 1 to 4, wherein the thermoplastic resin is a (meth) acrylic resin. A coating film containing a thermoplastic resin and
A laminated coating film having a coating film formed from the epoxy resin-based coating composition according to any one of claims 1 to 5. A method for repairing a coating film, which comprises a step of forming a coating film from the epoxy resin-based coating composition according to any one of claims 1 to 5 on a coating film containing a thermoplastic resin.