Paint composition and method for forming a multilayer film

Abstract

To provide a two-component water-based epoxy resin coating composition that offers excellent storage stability without compromising paintability and is suitable for thick-coat application. [Solution] A two-component water-based paint composition comprising (A) an epoxy resin as a main component and (B) a resin that reacts with epoxy as a curing agent, wherein the paint composition further comprises (C) a pigment, (D) water, and (E) a silane coupling agent as the main component and / or curing agent, and the paint composition satisfies specific conditions with respect to (E) the silane coupling agent.

Description

[Technical Field]

[0001] The present invention relates to a two-component aqueous coating composition containing an epoxy resin and a method for forming a multilayer film using the coating composition. [Background technology]

[0002] Examples of two-component water-based epoxy resin coatings include those described in Japanese Patent Publication No. 2016-194066 (Patent Document 1) and Japanese Patent Publication No. 2019-173006 (Patent Document 2).

[0003] Patent Document 1 describes a film-forming material containing an epoxy resin and an amine curing agent, characterized in that the epoxy equivalent of the epoxy resin is 500 g / eq or more and 2000 g / eq or less, the active hydrogen equivalent of the amine curing agent is 50 g / eq or more and 200 g / eq or less, and the ratio of the active hydrogen equivalent of the amine curing agent to the epoxy equivalent of the epoxy resin is less than 0.4 in terms of [active hydrogen equivalent of amine curing agent / epoxy equivalent of epoxy resin]. Patent Document 1 states that the film-forming material exhibits excellent adhesion to a wide range of substrates and coated surfaces.

[0004] Patent Document 2 describes an aqueous coating material comprising an aqueous epoxy resin (A), an amino group-containing resin (B), and an amino group-containing silane compound (M), characterized in that the mixing ratio thereof satisfies the following conditions (I) and (II). Patent Document 2 states that the aqueous coating material exhibits excellent adhesion to various substrates and coating films. (I)XA / YB>1 (II) YM / YB > 0.8 XA: Epoxy equivalent of water-based epoxy resin (A) YB: Active hydrogen equivalent of amino group-containing resin (B) YM: Active hydrogen equivalent of amino group-containing silane compound (M) [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-194066 [Patent Document 2] Japanese Patent Publication No. 2019-173006 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As described in Patent Documents 1 and 2, two-component water-based epoxy resin coatings have been studied to exhibit excellent adhesion to various substrates and coating films by adjusting the mixing ratio of epoxy resin and amine, or by adjusting the epoxy equivalent and active hydrogen equivalent. On the other hand, two-component water-based epoxy resin coatings generally have the problem of being prone to sagging, making it difficult to apply thick coats.

[0007] Therefore, an object of the present invention is to provide a two-component water-based epoxy resin coating composition that is suitable for thick coating, has excellent storage stability, and does not impair the workability of the coating. Another object of the present invention is to provide a method for forming a multilayer film using such a coating composition. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objective, the inventors have discovered that by using a two-component water-based epoxy resin coating composition, either by using a main component containing an epoxy resin and a specific amount of an amino group-containing silane coupling agent, or by using a curing agent containing a resin that reacts with epoxy and a specific amount of an epoxy group-containing silane coupling agent, it is possible to provide a coating composition that is excellent in storage stability and suitable for thick coating without impairing the coating workability, thus completing the present invention.

[0009] Therefore, the paint composition according to one embodiment of the present invention is a two-component water-based paint composition comprising (A) an epoxy resin as a main component and (B) a resin that reacts with epoxy as a curing agent, The aforementioned paint composition further comprises (C) a pigment, (D) water, and (E) a silane coupling agent as a main component and / or curing agent. The paint composition is characterized in that it satisfies at least one of the following conditions 1 and 2. Condition 1: The paint composition comprises the (E) silane coupling agent as a main component, wherein the (E) silane coupling agent comprises at least the (E1) amino group-containing silane coupling agent, and the amount of the (E1) amino group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of the main component. Condition 2: The paint composition contains the (E) silane coupling agent as a curing agent, wherein the (E) silane coupling agent contains at least the (E2) epoxy group-containing silane coupling agent, and the amount of the (E2) epoxy group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of the curing agent.

[0010] In a preferred example of the coating composition of the present invention, the resin that reacts with the epoxy (B) is a modified polyamine having at least a cyclic structure, and has an active hydrogen equivalent of 80 to 350 g / eq.

[0011] In another preferred example of the coating composition of the present invention, the epoxy resin (A) is a water-dispersible epoxy resin with an epoxy equivalent of 150 to 1000 g / eq.

[0012] In another preferred example of the paint composition of the present invention, the paint composition satisfies condition 1.

[0013] Furthermore, a multilayer film formation method according to one embodiment of the present invention is a multilayer film formation method that includes applying an undercoat paint to a substrate and drying it to form an undercoat film with a thickness of 50 to 150 μm, and applying a topcoat paint on the undercoat film and drying it to form a topcoat film with a thickness of 20 to 75 μm, The aforementioned undercoat paint is the paint composition of the present invention described above. The overcoating paint is selected from the group consisting of acrylic resin-based paints, urethane resin-based paints, epoxy resin-based paints, silicone resin-based paints, and fluororesin-based paints, and is a method for forming a multilayer film.

Advantages of the Invention

[0014] According to the paint composition of the present invention, it is possible to provide a two-component water-based epoxy resin paint composition that has excellent storage stability and is suitable for thick coating without impairing the coating workability. Further, according to the method for forming a multilayer film of the present invention, it is possible to provide a method for forming a multilayer film using such a paint composition.

Modes for Carrying Out the Invention

[0015] Hereinafter, the paint composition and the coated body of the present invention will be described in detail.

[0016] The paint composition according to an embodiment of the present invention is a two-component water-based paint composition that contains (A) an epoxy resin as a main agent and (B) a resin that reacts with epoxy as a curing agent, wherein the paint composition further contains (C) a pigment, (D) water, and (E) a silane coupling agent as the main agent and / or the curing agent, and the paint composition is characterized by satisfying at least one of the following Condition 1 and Condition 2. Condition 1: The paint composition contains the (E) silane coupling agent as the main agent, wherein the (E) silane coupling agent contains at least (E1) an amino group-containing silane coupling agent, and the amount of the (E1) amino group-containing silane coupling agent is 0.1 to 1.0% by mass based on the total amount of the main agent. Condition 2: The paint composition contains the (E) silane coupling agent as the curing agent, wherein the (E) silane coupling agent contains at least (E2) an epoxy group-containing silane coupling agent, and the amount of the (E2) epoxy group-containing silane coupling agent is 0.1 to 1.0% by mass based on the total amount of the curing agent.

[0017] We have found that, in a two-component water-based paint composition containing an epoxy resin as the main component and a resin that reacts with epoxy as the curing agent, by using a main component containing epoxy resin and a specific amount of amino group-containing silane coupling agent, or a curing agent containing a resin that reacts with epoxy and a specific amount of epoxy group-containing silane coupling agent, it is possible to apply a thick film while suppressing the occurrence of drips that may occur during painting, thereby achieving thick coating. This makes it possible to reduce the number of steps in the painting process by applying a thick coat. The reason why such an effect is obtained is thought to be that when the main component contains both epoxy resin and amino group-containing silane coupling agent, the epoxy resin and amino group-containing silane coupling agent react in the main component before the main component is mixed with the curing agent. As a result, the epoxy resin dispersed in the main component is in a state where intermolecular attractive forces can easily act due to interactions between resins and hydrogen bonding (the effect of hydrogen bonding is greater because the number of hydroxyl groups increases due to this reaction), which suppresses the occurrence of drips during painting. This also applies when the curing agent contains both a resin that reacts with epoxy and an epoxy group-containing silane coupling agent. Furthermore, the inventors have found that in order to suppress dripping and achieve thick coating, a main component containing an epoxy resin and an amino group-containing silane coupling agent may be used in combination with a curing agent containing a resin that reacts with epoxy and an epoxy group-containing silane coupling agent, or that thick coating can be achieved by using either the main component or the curing agent alone.

[0018] While adjusting the viscosity of the paint composition is a common method to suppress dripping, simply increasing the viscosity allows for thicker application, but it leads to poor workability and a deterioration in the appearance of the paint film. The paint composition of the present invention, however, allows for suppression of dripping while adjusting the viscosity to a level suitable for painting without increasing the viscosity during paint preparation. Therefore, it is possible to form a paint film without deteriorating workability or the appearance of the paint film.

[0019] The paint composition of the present invention is a two-component paint composition. A two-component paint composition is a paint composition comprising a main component and a curing agent. A two-component paint composition can be prepared by mixing the main component, the curing agent, and additives selected as needed during painting. In the paint composition of the present invention, the main component is an agent containing epoxy resin, and the curing agent is an agent containing a resin that reacts with epoxy.

[0020] The paint composition of the present invention is a water-based paint composition. In this specification, a water-based paint composition is a paint composition that contains water as the main solvent (the solvent with the highest content in the paint). The water that can be used in the water-based paint composition is not particularly limited, but examples include tap water, deionized water, distilled water, and other pure water. Furthermore, when storing the paint composition for a long period of time, water that has been sterilized by ultraviolet irradiation or the like may be used to prevent the growth of mold and bacteria. The amount of water contained in the paint composition of the present invention is preferably 30 to 90% by mass, and more preferably 40 to 70% by mass.

[0021] In this specification, the term "film-forming component" refers to the component excluding volatile components such as water and organic solvents, and is the component that ultimately forms a paint film. In this specification, the component remaining after drying the paint composition at 130°C for 60 minutes is treated as the film-forming component. The mass fraction of the component remaining after drying the paint composition at 130°C for 60 minutes (film-forming component) may be referred to as the heating residue (or non-volatile content (NV)).

[0022] The paint composition of the present invention contains an epoxy resin as a main component. In this specification, the epoxy resin is referred to as component (A) and may be referred to as "(A) epoxy resin". The epoxy resin is included in the main component.

[0023] Epoxy resins are resins that have epoxy groups in their molecules and can be cured by the reaction of these epoxy groups. Epoxy resins are generally known as resins with excellent corrosion resistance because they have high adhesion to substrates, especially metal substrates, and also have a shielding effect that protects the substrate from environmental factors (e.g., water, oxygen, etc.) that affect the corrosion of the substrate.

[0024] The epoxy resin is preferably a resin having at least two epoxy groups in one molecule, and is obtained, for example, by reacting a polyhydric alcohol or polyhydric phenol with a halohydrin. Specific examples include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyglycol type epoxy resin, bisphenol F type epoxy resin, epoxidized oil, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0025] The epoxy resin is preferably a water-dispersible epoxy resin. A water-dispersible epoxy resin is an epoxy resin that can be distributed in water to form a heterogeneous system (e.g., an emulsion or suspension).

[0026] The epoxy resin is preferably in the form of an epoxy resin emulsion or an epoxy resin dispersion. In this specification, a resin emulsion means an emulsion obtained by dispersing a resin in an aqueous medium mainly composed of water, and a resin dispersion means a dispersion obtained by dispersing a resin in an aqueous medium mainly composed of water. The epoxy resin emulsion is not particularly limited, but is prepared by emulsifying the epoxy resin in an aqueous medium mainly composed of water using a conventional forced emulsification method (a method using an emulsifier and a high-speed stirrer, etc.). Examples of emulsifiers include polyoxyethylene alkylphenol ether-based nonionic surfactants, polyethers such as polyoxyethylene-polyoxypropylene block copolymers, and adducts of at least one of the nonionic surfactant and the polyethers with a diisocyanate compound. The emulsifier may be used alone or as a blend of two or more. Commercially available epoxy resin emulsions include, for example, Epulsion EA-1, 2, 3, 7, 12, 20, 55, and HD2 (manufactured by Henkel Japan); Yukaresin KE-002, KE-116, E-1022, KE-301C (manufactured by Yoshimura Oil & Chemical Co., Ltd.); Adekaresin EM-101-50 (manufactured by Adeka Corporation); jER W1155R55, jER W3435R67, jER W2821R70 (manufactured by Mitsubishi Chemical Corporation). On the other hand, commercially available epoxy resin dispersions include, for example, Beckpox EP2381 (manufactured by Ornex Corporation); EPI-REZ6530-WH-53 (manufactured by Momentive Corporation).

[0027] The epoxy resin may be a modified epoxy resin. Examples of modified epoxy resins include urethane-modified epoxy resins, amine-modified epoxy resins, isocyanate-modified epoxy resins, acrylic-modified epoxy resins, polyester-modified epoxy resins, and dimer acid-modified epoxy resins.

[0028] The epoxy equivalent of the epoxy resin is preferably 150 to 1,000 g / eq, more preferably 200 to 700 g / eq, and even more preferably 300 to 600 g / eq. When the epoxy equivalent is 150 g / eq or higher, sufficient coating film properties are easily obtained. On the other hand, when the epoxy equivalent is 1,000 g / eq or lower, leveling properties are less likely to decrease, and a uniform coating film is easily obtained. The epoxy resin may be used alone or as a blend of two or more types. The epoxy equivalent of the epoxy resin can be determined according to JIS K 7236:2001 "Method for determining the epoxy equivalent of epoxy resin". When using multiple epoxy resins, the epoxy equivalent is determined from the total epoxy resin used.

[0029] In the paint composition of the present invention, the amount of epoxy resin is preferably 25 to 70% by mass, and more preferably 25 to 50% by mass, relative to the total amount of film-forming components. When the paint composition contains multiple epoxy resins, the amount of epoxy resin described herein is the total amount of epoxy resins.

[0030] The paint composition of the present invention contains a resin that reacts with epoxy as a curing agent. In this specification, the resin that reacts with epoxy is referred to as component (B) and may also be referred to as "(B) resin that reacts with epoxy". Epoxy refers to a compound having an epoxy group, and the above-mentioned (A) epoxy resin and the (E2) epoxy group-containing silane coupling agent described later are included in epoxy. The resin that reacts with epoxy is included in the curing agent.

[0031] Resins that react with epoxy are resins used to react with epoxy resins, particularly their epoxy groups, to promote or control the curing reaction. Resins that react with epoxy are preferably resins that have active hydrogen that reacts with epoxy groups, and more preferably polyamine resins. Polyamine resins are resins that have at least two amino groups in one molecule. Examples of polyamine resins include those produced by condensation polymerization of amines and aldehydes, etherification of amines with alcohols, ring-opening polymerization of heterocyclic amines (such as ethyleneimine), condensation of amines and carboxylic acids, or the Mannich reaction of amines, formaldehyde, and ketones or phenols. Here, polyamine resins that also have amide bonds in their molecules, such as those produced by condensation of amines and carboxylic acids, are sometimes referred to as "polyamideamine resins" or "polyamideamines." Furthermore, ring-opening polymerization of alkylene oxides such as ethylene oxide and propylene oxide can be used for etherification of amines with alcohols.

[0032] Examples of amines that can be used in the production of polyamine resins include aliphatic polyamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, triaminopropane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, and 1,3-bisaminomethylcyclohexane; aromatic polyamines such as phenylenediamine, metaxylylenediamine, paraxylylenediamine, and diaminodiphenylmethane; and amines with heterocyclic structures such as ethyleneimines.

[0033] Furthermore, the polyamine resin may be a modified polyamine resin. A modified polyamine resin is a polyamine resin in which some of the amino groups have been modified. Known methods can be used to modify the amino groups, such as amidation of the amino group, the Mannich reaction between the amino group and a carbonyl compound, and the addition reaction between the amino group and an epoxy group.

[0034] The resin that reacts with epoxy preferably contains a polyamine resin having at least a cyclic structure, more preferably contains a polyamine having at least a cyclic structure, and preferably contains a modified polyamine having at least a cyclic structure. The polyamine resin having a cyclic structure is preferably a modified polyamine resin having a cyclic structure, and even more preferably a polyamine in which the amino groups of the polyamine resin are Mannich-modified. By using a polyamine resin having a cyclic structure, the adhesion of the coating film to the substrate can be further improved.

[0035] The amount of polyamine resin having a cyclic structure is preferably 50 to 100% by mass, and more preferably 60 to 90% by mass, relative to the total amount of resin reacting with epoxy. If the paint composition contains multiple polyamine resins having cyclic structures, the amount of polyamine resin having a cyclic structure described herein is the total amount of polyamine resins having cyclic structures.

[0036] Polyamine resins having a cyclic structure can be obtained by using a substance having a cyclic structure during their manufacture. Examples of amines having a cyclic structure that can be used in the manufacture of polyamine resins include piperazines such as N-aminoethylpiperazine, aliphatic polyamines such as 1,3-bisaminoethylcyclohexane, isophoronediamine, 1-cyclohexylamino-3-aminopropane, 1,4-diaminocyclohexane, di(aminocyclohexyl)methane, 1,3-di-(aminocyclohexyl)propane, 2,4-diamino-cyclohexaneN,N'-diethyl-1,4-diaminocyclohexane, and 3,3'-dimethyl-4,4'-diaminocyclohexylmethane; and aromatic polyamines such as phenylenediamine, metaxylylenediamine, paraxylylenediamine, and diaminodiphenylmethane. Aliphatic polyamines having a cyclic structure are sometimes referred to as alicyclic polyamines. Examples of alcohols having a cyclic structure that can be used in the manufacture of polyamine resins include phenol and its derivatives. Examples of phenol derivatives include phenols in which a benzene ring is substituted with a hydrocarbon group, and in particular, phenols substituted with linear or branched hydrocarbon groups which may have one or more unsaturated bonds. Here, the hydrocarbon group is preferably a long-chain hydrocarbon group having 10 to 20 carbon atoms, and especially preferably an alkyl group. A specific example of a phenol derivative is cardanol.

[0037] The polyamine resin having a cyclic structure is preferably a polyamine resin obtained by the Mannich reaction of amines, formaldehyde, and a phenol derivative. Here, the cyclic structure is derived from the phenol derivative, and the amines are preferably chain compounds (or acyclic compounds) such as ethylenediamine. The phenol derivative is as described above, with cardanol being particularly preferred. Such polyamine resins are sometimes referred to as phenalkamines.

[0038] From the viewpoint of reactivity with epoxy resins, it is preferable that the resin that reacts with epoxy includes a polyamine resin having a cyclic structure and a polyamine resin not having a cyclic structure. Here, the polyamine resin that can be used in combination with the polyamine resin having a cyclic structure is not particularly limited, and for example, polyoxyethylene amines (also called polyetheramines) such as polyoxyethylenediamine and polyoxypropylenediamine can be used.

[0039] When using a polyamine resin having a cyclic structure and a polyamine resin not having a cyclic structure in combination, the amount of the polyamine resin having a cyclic structure is preferably 50 to 99% by mass of the total amount of resin that reacts with epoxy, and the amount of the polyamine resin not having a cyclic structure is preferably 1 to 50% by mass of the total amount of resin that reacts with epoxy.

[0040] The resin that reacts with the epoxy is preferably formulated in the form of an emulsion, a dispersion, or an aqueous solution.

[0041] The active hydrogen equivalent of the resin that reacts with epoxy is preferably 80 to 350 g / eq, and more preferably 100 to 250 g / eq. The active hydrogen equivalent of the resin that reacts with epoxy is the mass [g / eq] of the resin containing 1 equivalent of active hydrogen. For example, if the resin that reacts with epoxy is a polyamine resin, it is the value obtained by dividing the molecular weight of the resin that reacts with epoxy by the number of hydrogen atoms in the amino group per molecule. Furthermore, if multiple resins that react with epoxy are included, the active hydrogen equivalent of the resins that react with epoxy is calculated by dividing the total weight of the resins that react with epoxy by the total number of moles of active hydrogen contained in the resins that react with epoxy. Here, by dividing the weight of each resin that reacts with epoxy by its respective active hydrogen equivalent, the number of moles of active hydrogen contained in each resin that reacts with epoxy can be determined, and the sum of the determined number of moles of active hydrogen is the total number of moles of active hydrogen contained in the resins that react with epoxy.

[0042] In the paint composition of the present invention, the amount of resin that reacts with epoxy is preferably 3 to 30% by mass, and more preferably 10 to 20% by mass, relative to the total amount of film-forming components. When the paint composition contains multiple resins that react with epoxy, the amount of resin that reacts with epoxy described herein is the total amount of resins that react with epoxy.

[0043] The paint composition of the present invention contains a pigment as a main component and / or a curing agent. In this specification, the pigment is sometimes referred to as component (C) and "(C) pigment". The pigment may be contained in the main component, in the curing agent, or in both the main component and the curing agent.

[0044] As pigments, those commonly used in the paint industry, such as extender pigments, coloring pigments, and rust-preventive pigments, can be used.

[0045] Examples of extender pigments include silica, talc, mica, calcium carbonate, and barium sulfate. The amount of extender pigment is, for example, 10 to 50% by mass relative to the total amount of film-forming components. If the paint composition contains multiple extender pigments, the amount of extender pigment described here refers to the total amount of extender pigments.

[0046] Examples of coloring pigments include titanium dioxide, iron oxide (such as red iron oxide), carbon black, lead yellow, molybdate orange, ultramarine, Prussian blue, phthalocyanine blue, phthalocyanine green, quinacridone red, naphthol red, benzimidazolone yellow, Hansa yellow, benzimidazolone orange, and dioxazine violet. The amount of coloring pigment is, for example, 1 to 20% by mass relative to the total amount of film-forming components. If the paint composition contains multiple coloring pigments, the amount of coloring pigment described here refers to the total amount of coloring pigments.

[0047] Examples of rust-preventive pigments include zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, calcium zinc phosphate, aluminum zinc phosphate, zinc phosphate, aluminum phosphate, zinc phosphate molybdate, aluminum phosphate molybdate, magnesium phosphate, and vanadic acid / phosphate mixed pigments. Among these, phosphate-based rust-preventive pigments are preferred from the viewpoint of corrosion resistance. Examples of phosphate-based rust-preventive pigments include salts of phosphate compounds such as phosphoric acid, phosphorous acid, and polyphosphate (magnesium salts, calcium salts, zinc salts, aluminum salts, phosphate molybdate salts, etc.). The amount of rust-preventive pigment is, for example, 1 to 20% by mass relative to the total amount of film-forming components. When a paint composition contains multiple rust-preventive pigments, the amount of rust-preventive pigment described here is the total amount of rust-preventive pigments.

[0048] Furthermore, flake pigments can be used as pigments. Flake pigments may be classified as extender pigments, coloring pigments, or rust-preventive pigments, or they may not be classified as such. Flake pigments are pigments that have a thin, flat shape like foil, and specific examples include metallic pigments such as zinc, nickel, chromium, tin, copper, silver, platinum, gold, and aluminum, as well as glass flakes, talc, mica, kaolin clay, and mica-like iron oxide. Metallic pigments also include pigments of alloys such as stainless steel. In addition, flake pigments, such as talc and mica, may be surface-treated with inorganic metal oxides such as titanium dioxide and silica, or organic materials such as silicone resin.

[0049] Flake-shaped pigments, based on their flake shape, exhibit an effect of inhibiting the penetration of corrosive factors such as water, oxygen, and chlorides, thereby improving the environmental barrier properties of the coating film and contributing to its corrosion resistance. They also exhibit an effect of reducing internal stress in the coating film. By reducing internal stress, the adhesion of the coating film can be further improved, and thicker coating films can be advantageously formed.

[0050] The flake-like pigment preferably has an aspect ratio of 2 or more, more preferably an aspect ratio of 2 or more and less than 100, and even more preferably an aspect ratio of 2 to 30.

[0051] In this specification, the aspect ratio refers to the ratio (D / T) of the average particle diameter (D) to the average thickness (T) of the pigment. The average particle diameter of the pigment is the 50% particle diameter (D) of the volume-based particle size distribution. 50 This refers to the particle size distribution, which is determined from the particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. The particle size of the pigment is expressed as the equivalent spherical diameter by the laser diffraction / scattering method. The average thickness, on the other hand, is the average value of the thicknesses measured for 100 or more pigments using a scanning electron microscope (SEM).

[0052] The flake-like pigment preferably has an average particle size of 1 to 150 μm, and more preferably 3 to 60 μm. While a larger average particle size of the flake-like pigment can improve environmental barrier properties, if it is too large, it can increase the unevenness of the coating film, potentially degrading its appearance.

[0053] The amount of flake-like pigment is preferably 1.0 to 20.0 volume percent relative to the total amount of film-forming components. While a higher amount of flake-like pigment can improve environmental barrier properties, too much may reduce adhesion to the substrate.

[0054] In the paint composition of the present invention, the pigment volume concentration (PVC) is preferably 20-35%, more preferably 21-33%, and even more preferably 23-31%. If the PVC is too high, the resin component becomes relatively low, and the dispersibility of the pigment tends to decrease, which may reduce the storage stability of the paint composition or the corrosion resistance of the coating film. In addition, if the PVC is too high, the adhesion to the substrate may decrease.

[0055] In this specification, Pigment Volume Concentration (PVC) is the ratio of the total volume of pigment to the total volume of the film-forming components, and can be calculated from the composition and specific gravity of the components constituting the film-forming components.

[0056] The paint composition of the present invention is a water-based paint composition as described above, and contains water as a main component and / or curing agent. In this specification, water is sometimes referred to as component (D) and "(D) water". Water may be contained in the main component, in the curing agent, or in both the main component and the curing agent.

[0057] The coating composition of the present invention contains a silane coupling agent as a main component and / or curing agent. In this specification, the silane coupling agent is sometimes referred to as component (E) and as "(E) silane coupling agent". The silane coupling agent may be contained in the main component, in the curing agent, or in both the main component and the curing agent. Examples of silane coupling agents include amino group-containing silane coupling agents and epoxy group-containing silane coupling agents. In this specification, the amino group-containing silane coupling agent may be referred to as component (E1) and as "(E1) amino group-containing silane coupling agent", and the epoxy group-containing silane coupling agent may be referred to as component (E2) and as "(E2) epoxy group-containing silane coupling agent".

[0058] In one embodiment, the paint composition of the present invention contains (E) a silane coupling agent as the main component, wherein the (E) silane coupling agent contains at least (E1) an amino group-containing silane coupling agent, and the amount of the (E1) amino group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of the main component. According to this embodiment, the occurrence of dripping that may occur during painting can be suppressed. This is because, since the main component contains (A) epoxy resin and (E1) an amino group-containing silane coupling agent, it is thought that the (A) epoxy resin and (E1) amino group-containing silane coupling agent react in the main component before being mixed with the curing agent. For this reason, the paint composition of the present invention can be said to be a two-component water-based epoxy resin paint composition suitable for thick coating, as it allows for the application of a thick film while suppressing the occurrence of dripping that may occur during painting without impairing the paintability. Furthermore, from the viewpoint of storage stability of the main component, the amount of (E1) amino group-containing silane coupling agent contained in the main component is 0.1 to 1.0% by mass relative to the total amount of the main component. In this embodiment, the (E) silane coupling agent contained in the main component may not include a silane coupling agent that does not fall under (E1) an amino group-containing silane coupling agent, for example, (E2) an epoxy group-containing silane coupling agent, or it may include a silane coupling agent that does not fall under (E1) an amino group-containing silane coupling agent, for example, (E2) an epoxy group-containing silane coupling agent, in addition to (E1) an amino group-containing silane coupling agent.

[0059] In another embodiment, the paint composition of the present invention includes (E) a silane coupling agent as a curing agent, wherein the (E) silane coupling agent includes at least (E2) an epoxy group-containing silane coupling agent, and the amount of the (E2) epoxy group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of curing agent. According to this embodiment, the occurrence of dripping that may occur during painting can be suppressed. This is because the curing agent contains a resin that reacts with (B) epoxy and an (E2) epoxy group-containing silane coupling agent, and it is thought that the resin that reacts with (B) epoxy and the (E2) epoxy group-containing silane coupling agent react in the curing agent before being mixed with the main component. For this reason, the paint composition of the present invention can be said to be a two-component water-based epoxy resin paint composition suitable for thick coating, as it allows for the application of a thick film while suppressing the occurrence of dripping that may occur during painting without impairing the paintability. Furthermore, from the viewpoint of storage stability of the curing agent, the amount of (E2) epoxy group-containing silane coupling agent contained in the curing agent is 0.1 to 1.0% by mass relative to the total amount of curing agent. In this embodiment, the (E) silane coupling agent included in the curing agent may not include a silane coupling agent that does not fall under (E2) epoxy group-containing silane coupling agent, for example, (E1) amino group-containing silane coupling agent, or it may include a silane coupling agent that does not fall under (E2) epoxy group-containing silane coupling agent, for example, (E1) amino group-containing silane coupling agent, in addition to (E2) epoxy group-containing silane coupling agent.

[0060] In another embodiment, the paint composition of the present invention comprises a main component and a curing agent, wherein the (E) silane coupling agent contained in the main component contains at least an (E1) amino group-containing silane coupling agent, the amount of which is 0.1 to 1.0% by mass relative to the total amount of the main component, and the (E) silane coupling agent contained in the curing agent contains at least an (E2) epoxy group-containing silane coupling agent, the amount of which is 0.1 to 1.0% by mass relative to the total amount of the curing agent. According to this embodiment, the occurrence of dripping that may occur during painting can be suppressed. This is thought to be because the resin and the silane coupling agent react in the main component and the curing agent respectively before they are mixed. For this reason, the paint composition of the present invention can be said to be a two-component water-based epoxy resin paint composition suitable for thick coating, as it allows for the application of a thick film while suppressing the occurrence of dripping that may occur during painting without impairing the paintability. Furthermore, from the viewpoint of storage stability of the main component, the amount of (E1) amino group-containing silane coupling agent contained in the main component is 0.1 to 1.0% by mass relative to the total amount of the main component, and from the viewpoint of storage stability of the curing agent, the amount of (E2) epoxy group-containing silane coupling agent contained in the curing agent is 0.1 to 1.0% by mass relative to the total amount of the curing agent. In this embodiment, the (E) silane coupling agent contained in the main component may not include silane coupling agents that do not fall under the category of (E1) amino group-containing silane coupling agents, such as (E2) epoxy group-containing silane coupling agents, or it may include (E1) amino group-containing silane coupling agents in addition to silane coupling agents that do not fall under the category of (E1) amino group-containing silane coupling agents, such as (E2) epoxy group-containing silane coupling agents.Furthermore, in this embodiment, the (E) silane coupling agent contained in the curing agent may not include a silane coupling agent that does not fall under (E2) epoxy group-containing silane coupling agent, for example, (E1) amino group-containing silane coupling agent, or it may include a silane coupling agent that does not fall under (E2) epoxy group-containing silane coupling agent, for example, (E1) amino group-containing silane coupling agent, in addition to (E2) epoxy group-containing silane coupling agent.

[0061] When the paint composition of the present invention contains (A) an epoxy resin and (E1) an amino group-containing silane coupling agent as main components, the ratio (A:E1) of the epoxy equivalent of (A) the epoxy resin and the active hydrogen equivalent of (E1) the amino group-containing silane coupling agent in the main component is preferably 30:1 to 5:1, and more preferably 20:1 to 10:1. By adjusting the ratio (A:E1) of the epoxy equivalent of (A) the epoxy resin and the active hydrogen equivalent of (E1) the amino group-containing silane coupling agent in the main component to the above-specified range, it is possible to ensure storage stability while significantly reducing the effect of suppressing dripping that may occur during painting. Here, the epoxy equivalent of (A) the epoxy resin can be determined by the method described above. Furthermore, the active hydrogen equivalent of (E1) the amino group-containing silane coupling agent is the mass [g / eq] of the silane coupling agent containing 1 equivalent of active hydrogen, and is the value obtained by dividing the molecular weight of the silane coupling agent by the number of hydrogen atoms of active hydrogen per molecule. In this context, the hydrogen atoms referred to as "active hydrogen" are those directly bonded to a nitrogen atom, such as those found in amino groups or imino groups. Furthermore, when multiple (E1) amino group-containing silane coupling agents are present, the active hydrogen equivalent of each (E1) amino group-containing silane coupling agent is calculated by dividing the total weight of the (E1) amino group-containing silane coupling agents by the total number of moles of active hydrogen contained in the (E1) amino group-containing silane coupling agents. Here, the number of moles of active hydrogen contained in each (E1) amino group-containing silane coupling agent can be determined by dividing the weight of each (E1) amino group-containing silane coupling agent by its respective active hydrogen equivalent, and the sum of these determined moles of active hydrogen is the total number of moles of active hydrogen contained in the (E1) amino group-containing silane coupling agents.

[0062] When the paint composition of the present invention contains (B) a resin that reacts with epoxy and (E2) an epoxy group-containing silane coupling agent as a curing agent, the ratio (B:E2) of the active hydrogen equivalent of (B) the resin that reacts with epoxy and the epoxy equivalent of (E2) the epoxy group-containing silane coupling agent contained in the curing agent is preferably 100:1 to 38:1, and more preferably 80:1 to 50:1. By adjusting the ratio (B:E2) of the active hydrogen equivalent of (B) the resin that reacts with epoxy and the epoxy equivalent of (E2) the epoxy group-containing silane coupling agent contained in the curing agent to the above-specified range, it is possible to ensure storage stability while increasing the effect of suppressing the occurrence of drips that may occur during painting. Here, the active hydrogen equivalent of (B) the resin that reacts with epoxy can be determined by the method described above. Furthermore, the epoxy equivalent of (E2) the epoxy group-containing silane coupling agent is the mass [g / eq] of the silane coupling agent containing 1 equivalent of epoxy group, and is the value obtained by dividing the molecular weight of the silane coupling agent by the number of epoxy groups per molecule. Furthermore, if multiple (E2) epoxy group-containing silane coupling agents are included, the epoxy equivalent of the (E2) epoxy group-containing silane coupling agent is calculated by dividing the total weight of the (E2) epoxy group-containing silane coupling agents by the total number of moles of epoxy groups contained in the (E2) epoxy group-containing silane coupling agents. Here, by dividing the weight of each (E2) epoxy group-containing silane coupling agent by its respective epoxy equivalent, the number of moles of epoxy groups contained in each (E2) epoxy group-containing silane coupling agent can be determined, and the sum of the determined number of moles of epoxy groups is the total number of moles of epoxy groups contained in the (E2) epoxy group-containing silane coupling agents.

[0063] (E1) Examples of amino group-containing silane coupling agents include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldiethoxy Examples include silane, N-β-(aminoethyl)-γ-aminopropyltriisopropoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-8-aminooctyltrimethoxysilane, γ-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, etc. (E1) The effect of suppressing dripping can be enhanced by using a primary amino group-containing silane coupling agent in combination with a secondary amino group-containing silane coupling agent, or by using a silane coupling agent that contains both primary and secondary amino groups. (E1) The amino group-containing silane coupling agent may have multiple amino groups, but it is preferable that the (E1) amino group-containing silane coupling agent has one amino group (which can also be called a monoamine if the focus is on the amino group) and / or has two amino groups (which can also be called a diamine if the focus is on the amino group).

[0064] Furthermore, it is preferable that the (E1) amino group-containing silane coupling agent includes a primary amino group-containing silane coupling agent having one amino group (which can also be called a primary monoamine if focusing on the amino group) and / or a secondary amino group-containing silane coupling agent having one amino group (which can also be called a secondary monoamine if focusing on the amino group). Having one amino group in the (E1) amino group-containing silane coupling agent enhances the effect of suppressing sauce formation without reducing storage stability or increasing viscosity.

[0065] (E2) Examples of epoxy group-containing silane coupling agents include glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethylmethoxysilane, γ-glycidoxypropyl(ethyl)dimethoxysilane, β-3,4-epoxycyclohexylethyltrimethoxysilane, β-3,4-epoxycyclohexylethyltriethoxysilane, 8-glycidoxyoctyltrimethoxysilane, 8-glycidoxyoctylmethyldimethoxysilane, 8-glycidoxyoctylmethyldiethoxysilane, epoxysilane oligomers, and the like.

[0066] In the coating composition of the present invention, the amount of (E) silane coupling agent is preferably 0.5 to 4.0% by mass, and more preferably 1.5 to 3.3% by mass, relative to the total amount of coating film-forming components.

[0067] In the paint composition of the present invention, when the amount of epoxy resin (A) contained in the main component is 100 parts by mass, the amount of amino group-containing silane coupling agent (E1) contained in the main component is preferably 0.2 to 6.0 parts by mass, and more preferably 0.8 to 5.0 parts by mass.

[0068] In the paint composition of the present invention, when the amount of resin that reacts with (B) epoxy contained in the curing agent is 100 parts by mass, the amount of (E2) epoxy group-containing silane coupling agent contained in the curing agent is preferably 0.2 to 3.0 parts by mass, and more preferably 1.0 to 2.0 parts by mass.

[0069] In the paint composition of the present invention, when the total amount of (A) epoxy resin and (B) resin that reacts with epoxy contained in the paint composition is 100 parts by mass, the total amount of (E1) amino group-containing silane coupling agent and (E2) epoxy group-containing silane coupling agent contained in the paint composition is preferably 0.1 to 5.0 parts by mass, and more preferably 0.5 to 4.5 parts by mass.

[0070] The paint composition of the present invention may contain, as appropriate for the purpose, other components such as resins not corresponding to component (A) or (B), dispersants, film-forming aids, antifreeze agents, viscosity modifiers, surface modifiers, defoaming agents, rust inhibitors not corresponding to rust-inhibiting pigments, anti-settlement agents, anti-skinning agents, anti-sagging agents, anti-separation agents, matting agents, adhesion enhancers, leveling agents, drying agents, catalysts, plasticizers, antifungal agents, antibacterial agents, antiviral agents, preservatives, insecticides, antistatic agents, and conductivity enhancers. Each of these components may be contained in the main component, in the curing agent, or in both the main component and the curing agent. The non-volatile content of the viscosity modifier is preferably 0 to 0.6% by mass relative to the non-volatile content of the paint composition.

[0071] The paint composition of the present invention is a two-component paint composition as described above, and can be prepared by preparing the main component and hardener in advance and mixing the main component, hardener, and additives as needed during painting. The main component and hardener can be prepared by mixing various components as needed and appropriately selected.

[0072] The paint composition of the present invention preferably has a viscosity of 1 to 1000 (Pa·s, 23℃) at a shear rate of 0.1 (1 / s), and a viscosity of 0.05 to 10 (Pa·s, 23℃) at a shear rate of 1000 (1 / s).

[0073] In this specification, the viscosity of the paint composition is measured using a rheometer (e.g., an Anton Paar MCR302e rheometer) after adjusting the liquid temperature to 23°C. For example, the viscosity of the paint composition can be easily adjusted by using a solvent such as water for dilution during the preparation of the paint composition.

[0074] As described above, the paint composition of the present invention allows for the application of a thick film while suppressing the occurrence of drips that may occur during painting without impairing paintability. For example, it is possible to set the viscosity ratio, determined by the viscosity at a shear rate of 0.1 (1 / s) (Pa·s, 23°C) / the viscosity at a shear rate of 1000 (1 / s) (Pa·s, 23°C), to a value greater than 300, preferably greater than 350. In this specification, the value of the viscosity ratio determined by the viscosity at a shear rate of 0.1 (1 / s) (Pa·s, 23°C) / the viscosity at a shear rate of 1000 (1 / s) (Pa·s, 23°C) is defined as the TI value. TI is an abbreviation for Thixotropic Index. The larger the TI value, the more effectively the viscosity decreases during painting, resulting in superior paintability. There is no particular upper limit to the TI value, but for example, it may be 800 or less.

[0075] From the viewpoint of workability and ease of preparation, the viscosity of the main component is preferably 80 KU or more and less than 140 KU at 23°C, and more preferably 80 KU or more and less than 120 KU at 23°C. Here, the viscosity of the main component is measured using a Stormer viscometer after adjusting the liquid temperature to 23°C.

[0076] The coating method for the paint composition of the present invention is not particularly limited, and known coating methods such as brush coating, roller coating, trowel coating, spatula coating, flow coater coating, and spray coating (e.g., air spray coating, airless spray coating) can be used.

[0077] The drying method for the paint composition of the present invention is not particularly limited and may be either natural drying at ambient temperature or forced drying using a drying machine, etc. However, the paint composition of the present invention is preferably a paint composition that is intended to be naturally dried at ambient temperature. An ambient temperature of about 5 to 40°C is assumed.

[0078] The paint composition of the present invention is a two-component, water-based epoxy resin paint composition suitable for thick coating, and can form a thick film with a dry film thickness of 50 to 150 μm in a single coating.

[0079] The paint composition of the present invention is suitable as a primer.

[0080] From the viewpoint of providing adhesion in thick coatings, the paint composition of the present invention preferably has a glass transition temperature (Tg) of 10 to 70°C for the coating film formed from the paint composition, and more preferably has a glass transition temperature (Tg) of 20 to 60°C.

[0081] In this specification, the glass transition temperature can be measured by differential scanning calorimeter (DSC) in accordance with JIS K 7121:2012 (Method for measuring the transition temperature of plastics). For example, approximately 10 mg of the sample (e.g., a piece of coating) is placed in an aluminum pan for measurement, and DSC measurement is performed under the following measurement conditions. (Measurement temperature conditions) -80℃ to 220℃ (20℃ / min)

[0082] Next, the method for forming a multilayer film according to the present invention will be described in detail.

[0083] The multilayer film is composed of at least two types of coating films (for example, a two-layer structure of an undercoat and a topcoat, or a three-layer structure of an undercoat, an intermediate coat, and a topcoat). In the multilayer film formation method of the present invention, at least one type of coating film of the multilayer film is formed by the paint composition of the present invention as described above.

[0084] A method for forming a multilayer film according to one embodiment of the present invention includes applying a primer to a substrate and drying it to form a primer film, and applying a topcoat paint on the primer film and drying it to form a topcoat film, where the primer is the paint composition of the present invention. In this embodiment, a further coating film may be formed between the primer film and the topcoat film. For example, a method for forming a multilayer film according to another embodiment of the present invention includes applying a primer to a substrate and drying it to form a primer film, applying an intermediate coating paint on the primer film and drying it to form an intermediate coating film, and applying a topcoat paint on the intermediate coating film and drying it to form a topcoat film, where the primer is the paint composition of the present invention.

[0085] The base material can take on various shapes, including two-dimensional base materials such as films, sheets, and plates, and three-dimensional base materials that are complex three-dimensional objects. The surface of the base material may be smooth or may have irregularities. Specific examples of base materials include steel materials such as steel plates, steel pipes, and steel bars, as well as steel structures such as steel towers, bridges, and plants.

[0086] The substrate may have its surface subjected to pretreatments such as degreasing, chemical conversion treatment, polishing, plating, or metal spraying.

[0087] The substrate may have a prior coating on its surface. The prior coating may cover part or all of the surface of the substrate. In this specification, "prior coating" means a coating that is already present on the substrate when painting, in particular repair, is performed.

[0088] If the substrate has an old paint film on its surface, the substrate surface, including the old paint film, can be coated with the paint composition. If the old paint film is intact, the paint composition can be applied to the old paint film without peeling or removing it from the substrate surface. Since contaminants such as dust and dirt adhere to the old paint film, removing these contaminants can improve the adhesion of the new paint film to the old paint film. Methods for removing contaminants include high-pressure water cleaning, alkaline cleaning such as caustic soda, acidic cleaning with inorganic or organic acids, cleaning with bleach such as perchloric acid, scraping, and wiping with a cloth.

[0089] The dry film thickness of the primer coating is preferably 50 to 150 μm. Since the primer coating is formed by the paint composition of the present invention, it can be produced in a single coat, but is not limited to this, and the primer coating may be formed by multiple coats.

[0090] The undercoat film is a coating film formed from the paint composition of the present invention, and its glass transition temperature (Tg) is preferably 10 to 70°C, and more preferably 20 to 60°C.

[0091] The topcoat paint is preferably selected from the group consisting of acrylic resin-based paints, urethane resin-based paints, epoxy resin-based paints, silicone resin-based paints, and fluororesin-based paints. Acrylic resin-based paints refer to paints that form a coating film containing acrylic resin, urethane resin-based paints refer to paints that form a coating film containing urethane resin, epoxy resin-based paints refer to paints that form a coating film containing epoxy resin, silicone resin-based paints refer to paints that form a coating film containing silicone resin, and fluororesin-based paints refer to paints that form a coating film containing fluororesin.

[0092] The dry film thickness of the topcoat is preferably 20 to 75 μm. The topcoat may be formed in a single coat or in multiple coats.

[0093] The intermediate coating paint is preferably selected from the group consisting of acrylic resin-based paints, urethane resin-based paints, epoxy resin-based paints, silicone resin-based paints, and fluororesin-based paints. The intermediate coating paint may be a paint that forms a coating film containing a resin different from the resin contained in the topcoat coating film.

[0094] The dry film thickness of the intermediate coating is preferably 15 to 50 μm. The topcoat may be formed in a single coat or in multiple coats. [Examples]

[0095] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0096] <Examples of paint composition preparation> The main component and hardener were prepared by mixing the materials according to the formulations shown in Tables 1-3. The obtained main component and hardener were then mixed according to the mixing ratios shown in Tables 4-6, diluting with water as needed to prepare the paint composition. The formulations shown in Tables 1-3 and the mixing ratios shown in Tables 4-6 are based on mass.

[0097] The details of the materials used in preparing the paint composition are shown below.

[0098] (A) Epoxy resin Epoxy resin 1: ADEKA Resin EM101-50 (Epoxy resin emulsion manufactured by ADEKA Corporation; Non-volatile content 47% by mass, epoxy equivalent 510 g / eq) Epoxy resin 2: jER W2801 (Epoxy resin emulsion manufactured by Mitsubishi Chemical Corporation; non-volatile content 70% by mass, epoxy equivalent 190-205 g / eq)

[0099] (B) Resins that react with epoxy Polyamine resin 1: Cardolite NX-8401 (Amine resin emulsion manufactured by Cardolite; modified polyamine having at least a cyclic structure, non-volatile content 57% by mass, active hydrogen equivalent 165 g / eq) Polyamine resin 2: Daitokral X-7024 (amine resin emulsion manufactured by Daito Sangyo Co., Ltd.; modified polyamine having at least a cyclic structure, non-volatile content 50% by mass, active hydrogen equivalent 196 g / eq) Polyamine resin 3: JEFFAMINE T-403 (polyetheramine manufactured by HUNTSUMAN; non-volatile content 100% by mass, active hydrogen equivalent 81 g / eq)

[0100] (C) Pigment Aluminum tripolyphosphate: K-WHITE#84S (manufactured by Teika, aspect ratio less than 2, non-volatile content 100% by mass) Mica: Average particle size 23 μm, aspect ratio 70, non-volatile content 100% by mass Aluminum: EMR-7670 (manufactured by Toyo Aluminum Co., Ltd., silica-treated aluminum paste, average particle size 16 μm, aspect ratio 2-16, non-volatile content 60% by mass) Talc: Average particle size 14 μm, aspect ratio 2 to less than 20, non-volatile content 100% by mass Calcium carbonate: Average particle size 6 μm, aspect ratio less than 2, non-volatile content 100% by mass Silica: SYLYSIA 350 (manufactured by Fuji Silysia Chemical Co., Ltd., average particle size 3.9 μm, aspect ratio less than 2, non-volatile content 100% by mass) Titanium dioxide: White pigment, aspect ratio less than 2, non-volatile content 100% by mass Carbon black: Black pigment, aspect ratio less than 2, non-volatile content 100% by mass Yellow iron oxide: Oxide pigment, aspect ratio less than 2, non-volatile content 100% by mass Red iron oxide: rust-colored pigment, aspect ratio less than 2, non-volatile content 100% by mass

[0101] (D)Water Ion-exchanged water The "(D) Water" column in the table indicates the amount of water mixed with the epoxy resin emulsion or other materials during the preparation of the main component or curing agent, rather than the water used as a solvent in the epoxy resin emulsion or other materials.

[0102] (E) Silane coupling agent (E1) Amino group-containing silane coupling agent Amino group-containing silane coupling agent 1: 3-aminopropyltrimethoxysilane, active hydrogen equivalent 89.65 (g / eq) Amino group-containing silane coupling agent 2: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, active hydrogen equivalent 74.13 (g / eq) (E2) Epoxy group-containing silane coupling agent Epoxy group-containing silane coupling agent 1: 3-glycidoxypropyltrimethoxysilane, epoxy equivalent 236.4 (g / eq) Epoxy group-containing silane coupling agent 2: KR-516 manufactured by Shin-Etsu Chemical Co., Ltd., epoxy silane oligomer, epoxy equivalent 280 (g / eq), non-volatile content 100% by mass

[0103] Silane materials that do not fall under component (E1) or component (E2) KR500: Methyl-based silicone oligomer (manufactured by Shin-Etsu Chemical Co., Ltd., non-volatile content 100% by mass)

[0104] Other additives Dispersant: Floren GW-1640 (manufactured by Kyoeisha Chemical Co., Ltd., non-volatile content 40% by mass) Film-forming aid: Dipropylene glycol n-butyl ether Antifreeze: Ethylene glycol (0% by mass of non-volatile content, antifreeze for paints) Viscosity modifier 1: SN Thickener 665T (manufactured by Sunopco, urethane-modified polyether compound, 30% by mass of non-volatile content) Surface modifier: Polyflow KL-900 (manufactured by Kyoeisha Chemical Co., Ltd., amphiphilic oligomer, non-volatile content 100% by mass) Defoaming agent: SN Deformer 1312 (manufactured by Sunopco, 50% by mass of non-volatile content) Rust inhibitor: Sodium nitrite (100% by mass of non-volatile content)

[0105] <Confirmation test regarding the reaction between resin and silane coupling agent> The following four measurement samples were prepared, and IR (infrared spectroscopy) measurements were performed on each sample. (i) An aqueous dispersion of an epoxy resin (Sample 1) prepared by mixing 71 parts by mass of Adeka Resin EM101-50 and 29 parts by mass of jER W2801 (ii) A mixed solution (Sample 2) obtained by mixing 100 parts by mass of the aqueous dispersion of the epoxy resin in (i) above and 1.3 parts by mass of an amino group-containing silane coupling agent (KBM-903 manufactured by Shin-Etsu Chemical Co., Ltd.) and then allowing the mixture to stand at 23°C for 20 minutes (iii) An aqueous solution of an amino group-containing silane coupling agent (Sample 3) prepared by mixing an amino group-containing silane coupling agent (KBM-903 manufactured by Shin-Etsu Chemical Co., Ltd.) and water at a mass ratio of 1:1 IR measurement was carried out by measuring the IR spectrum at wavelengths of 4000 to 700 cm using a Fourier transform infrared spectrophotometer (FT / IR-4600, manufactured by JASCO Corporation) -1

[0106] Regarding the IR measurement results, in Sample 1, peaks of the epoxy resin were confirmed, and a peak derived from an epoxy group was observed around 1250 cm -1 and a peak derived from an OH group was observed around 3400 cm -1 In Sample 2, compared with Sample 1, the peak intensity around 1250 cm -1 weakened, and the peak intensity around 3400 cm -1 strengthened. This is considered to suggest a decrease in epoxy groups due to the reaction between the amino groups of the amino group-containing silane coupling agent and the epoxy groups of the epoxy resin, and the formation of Si-OH due to the hydrolysis of the amino group-containing silane coupling agent. In Sample 3, peaks were observed around 3400 cm -1 and around 1000 to 1100 cm -1 but no peak was observed around 1250 cm -1 Therefore, it can be seen that the peak around 1250 cm -1 is not derived from the silane coupling agent [[ID=?]] [[ID=?]]

[0107] [[ID=?]] The prepared coating composition was used to evaluate the thick coating suitability, storage stability, viscosity, and workability. The results are shown in Tables 4 to 6

[0108] ​ <Suitable for thick application> The main component and hardener prepared in the above <Example of Paint Composition Preparation> were mixed at 23°C, diluted with 5% water, and allowed to stand for 30 minutes to prepare the paint composition. Sag testers (gap sizes 600, 700, 800, 900, 1000 μm) were placed on a 20 × 20 × 1 cm glass plate, and the paint composition was poured in from the top of the sag tester. Painting was performed by moving the sag tester in a straight line at a constant speed. After painting, the glass plate was quickly propped up vertically so that the thicker film thickness side was facing downwards, and it was checked whether flow (sagging) occurred in the paint composition. The suitability for thick coating was evaluated according to the following criteria. Paint compositions that receive an evaluation of "○" or "△" are considered to be paint compositions that can suppress the occurrence of sagging that may occur during thick film coating. (standard) ○: No flow (slack) occurs in the 1000 μm gap. △: No flow (slack) occurs in the 900 μm gap. ×: Flow (slack) is occurring in a gap of 800 μm.

[0109] <Storage stability of the main ingredient> The main component prepared in the above <Example of Paint Composition Preparation> was placed in a sealed container and left to stand at 50°C for 4 weeks. The changes in properties during this period were observed, and the storage stability was evaluated according to the following criteria. Main components that receive an evaluation of "○" or "△" are considered to have excellent storage stability. (standard) ○: No change, or very little change. △: Slight changes in characteristics are observed. ×: Significant change in viscosity, or solidification occurs.

[0110] <Storage stability of hardening agent> The curing agents prepared in the above <Example of Paint Composition Preparation> were placed in a sealed container and left to stand at 50°C for 4 weeks. Changes in properties were observed, and storage stability was evaluated according to the following criteria. Curing agents with an evaluation of "○" or "△" are considered to have excellent storage stability. (standard) ○: No change, or very little change. △: Slight changes in characteristics are observed. ×: Significant change in viscosity, or solidification occurs.

[0111] <Viscosity of the main component> The viscosity of the main component prepared according to the above <Example of Paint Composition Preparation> was measured immediately after preparation. The measurement was performed at a liquid temperature of 23°C using a digital stomer viscometer. The initial viscosity was evaluated according to the following criteria. (standard) ○: 80 KU or more, less than 120 KU △: 120 KU or more, less than 140 KU ×: Unmeasurable

[0112] <Workability (thick film coating properties)> The paint composition was prepared according to the description in the above <Example of Paint Composition Preparation>. Here, the paint composition was diluted with water using a Rion viscometer so that its viscosity was in the range of 60 to 80 (dPa·s) at 23°C. A 450 × 450 mm tin plate was painted using a roller with a pile length of 20 mm, while controlling the film thickness with a WET gauge so that the dry film thickness was 120 μm or more. The workability (thick film coating ability) was evaluated according to the following criteria. Paint compositions that receive an evaluation of "○" or "△" are considered to be paint compositions that can be applied as a thick film. (standard) ○: Allows for coating with a film thickness 1.5 times or more than the specified wet film thickness (250 μm to 350 μm), and enables uniform coating with smooth roller rotation. △: While coating with a film thickness greater than the specified wet film thickness (250μm~350μm) is possible, some problems such as slippage may occur. ×: It is not possible to paint with the specified wet film thickness (250 μm to 350 μm).

[0113] <Workability (appearance after painting)> The paint composition prepared according to the description in <Example of Paint Composition Preparation> above was diluted with water using a Rion viscometer so that its viscosity was in the range of 60-80 (dPa·s) at 23°C. Then, a 450 × 450 mm tinplate was coated using a roller with a pile length of 20 mm to a dry film thickness of 120 μm, and dried at 23°C for 48 hours to prepare a test plate. The dry film thickness was measured using an electromagnetic film thickness gauge (Elcometer 456 separate type film thickness gauge, manufactured by Elcometer). The film thickness was measured at 25 points in a grid pattern of 5 columns and 5 rows, excluding a 50 mm radius from the edge of the test plate. The mean and standard deviation were calculated, and the coefficient of variation was calculated from these values. Workability (appearance after coating) was evaluated according to the following criteria. A paint composition that receives a "○" or "△" evaluation indicates that it is possible to form a paint film without deteriorating the appearance of the coating. (standard) ○: The coefficient of variation of the measured dry coating thickness is less than 25%. △: The coefficient of variation of the measured dry coating thickness is between 25% and less than 40%. ×: The coefficient of variation of the measured dry coating thickness is 40% or higher. -: Evaluation was not performed due to poor workability (film thickness coating properties).

[0114] <Workability (TI value)> The paint composition was prepared without dilution according to the description in <Example of Paint Composition Preparation> above. The viscosity (Pa·s, 23℃) of the paint composition was measured using a rheometer at shear rates of 0.01 (1 / s) and 1000 (1 / s). The ratio of viscosity at shear rate 0.1 (1 / s) to viscosity at shear rate 1000 (1 / s) was calculated as the TI value, and the workability (TI value) was evaluated according to the following criteria. The larger the TI value, the greater the degree of viscosity reduction at high shear rates. Paint compositions with an evaluation of "○" or "△" are considered to have good paint workability because their viscosity decreases significantly during painting. (evaluation) ○: Viscosity ratio exceeds 350 △: Viscosity ratio is 350 or less and greater than 300 ×: The viscosity ratio is 300 or less.

[0115] A paint composition that receives a rating of "○" or "△" in the above-mentioned <Suitability for Thick Coating> and also receives a rating of "○" or "△" in the above-mentioned <Workability (Thick Film Coating Ability)> is recognized as a paint composition suitable for thick coating. A paint composition containing a main component that is rated "○" or "△" in the above-mentioned <Storage Stability of Main Component> and a curing agent that is rated "○" or "△" in the above-mentioned <Storage Stability of Curing Agent> is recognized as a paint composition with excellent storage stability. A paint composition that receives a rating of "○" or "△" in the above-mentioned <Workability (thick film coating ability)>, a rating of "○" or "△" in the above-mentioned <Workability (appearance after coating)>, and a rating of "○" or "△" in the above-mentioned <Workability (TI value)> is recognized as a paint composition with excellent coating workability.

[0116] The paint compositions of Examples 1 to 13 exhibited excellent storage stability and application workability, and were suitable for thick-coat application. The paint composition of Comparative Example 1 did not contain (E1) an amino group-containing silane coupling agent or (E2) an epoxy group-containing silane coupling agent, resulting in insufficient paintability, sagging during thick-film coating, and the inability to apply a thick film. The paint composition of Comparative Example 2, by incorporating silica, was able to suppress the sagging that could occur during thick-film coating, but the inability to apply a thick film remained. The paint composition of Comparative Example 3 contained a viscosity modifier instead of (E1) an amino group-containing silane coupling agent or (E2) an epoxy group-containing silane coupling agent, but its paintability was insufficient. Furthermore, although it was possible to apply a thick film with the paint composition of Comparative Example 3, sagging was observed during thick film application. The paint composition of Comparative Example 4 was a paint composition with an even higher viscosity modifier content than that of Comparative Example 3, and while it was possible to suppress sagging during thick film application, its paintability was insufficient. The paint composition of Comparative Example 5 had insufficient storage stability of the main component because it contained too much (E1) amino group-containing silane coupling agent in the main component. The paint composition of Comparative Example 6 had insufficient storage stability of the curing agent because it contained too much (E2) epoxy group-containing silane coupling agent in the curing agent. In Comparative Example 7, the paint composition contained a (E1) amino group-containing silane coupling agent as a hardener, rather than as a main component. As a result, the paint had insufficient workability, and sagging occurred during thick-film coating, making it impossible to apply a thick film.

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] [Table 4]

[0121] [Table 5]

[0122] [Table 6]

[0123] <Durability evaluation of the painting system> The prepared paint compositions were evaluated for their durability in a hypothetical coating system, specifically for their resistance to repeated wet-cold cycles. The prepared paint compositions were diluted with water using a Rion viscometer to achieve a viscosity of 40-80 dPa·s at 23°C.

[0124] (Examples of preparation of intermediate and topcoat paint compositions) For topcoats 1 and 2 and intermediate coat 1, the main component and hardener were first prepared by mixing the materials according to the formulation shown in Table 7. Then, the obtained main component and hardener were mixed in the mixing ratios shown in Table 7 to prepare the paint composition. For topcoat 3, the paint composition was prepared by mixing the materials according to the formulation shown in Table 7. The formulations and mixing ratios shown in Table 7 are based on mass.

[0125] The details of the materials used in preparing the paint composition are shown below. Acrylic resin 1: Acronal 7659 (BASF, acrylic silicone resin emulsion, non-volatile content 50% by mass, acid value / hydroxyl value = 15 / 0) Acrylic resin 2: Proprietary synthetic resin (acrylic resin emulsion, non-volatile content 45% by mass, acid value / hydroxyl value = 12.9 / 0, methyl methacrylate (MMA) / butyl acrylate (BA) / butyl methacrylate (BMA) / cyclohexyl methacrylate (CHMA) / methacrylic acid (MAA) / 1,2,2,6,6-pentamethyl-4-piperidyl methacrylic acid (LA82) = 20 / 27 / 20 / 30 / 2 / 1 (mass ratio), particle size 110 nm) Carbodiimide compound: E-07S (manufactured by Nisshinbo Chemical Co., Ltd., non-volatile content 42%) Calcium carbonate: Average particle size 6 μm, aspect ratio less than 2, non-volatile content 100% by mass Polyamine resin 1: Cardolite NX-8401 (Amine resin emulsion manufactured by Cardolite; modified polyamine having at least a cyclic structure, non-volatile content 57% by mass, active hydrogen equivalent 165 g / eq) Talc: Average particle size 14 μm, aspect ratio 2 to less than 20, non-volatile content 100% by mass Titanium dioxide: White pigment, aspect ratio less than 2, non-volatile content 100% by mass Dispersant: Floren GW-1640 (manufactured by Kyoeisha Chemical Co., Ltd., non-volatile content 40% by mass) Film-forming aid: Dipropylene glycol n-butyl ether Antifreeze: Ethylene glycol (0% by mass of non-volatile content, antifreeze for paints) UV absorber: EVERSORB 80 (manufactured by Eiko Chemical Co., Ltd., benzotriazole compound, 84% by mass of non-volatile content) Viscosity modifier 2: PRIMAL RM-2020NPR (manufactured by Dow Chemical, urethane-associated thickening compound, non-volatile content 20% by mass) Viscosity modifier 3: PRIMAL RM-6000 (manufactured by Dow Chemical Company, urethane-associated thickening compound, non-volatile content 17.5% by mass)

[0126] [Table 7]

[0127] (Resistant to repeated cycles of wet and cold temperatures) A test of resistance to repeated wet-cold cycles was conducted in accordance with JIS K 5659 (2018) "Weather-resistant coatings for steel structures," section 7.18 "Wet-cold cycle resistance." Here, the dry film thickness of the primer was set to 110-130 μm, the intermediate coat thickness to 25-35 μm if an intermediate coat was included, the topcoat thickness to 20-30 μm, and the topcoat thickness to 50-60 μm if an intermediate coat was not included. The primer, intermediate coat, and topcoat paints used in the coating system are shown in Table 8. Ten cycles of testing were performed. The wet-cold cycle resistance was evaluated according to the following criteria. The results are shown in Table 8. (standard) ○: No blistering, cracking, or peeling of the coating. ×: The paint film has blisters, cracks, or peeling.

[0128] The test results showed no blistering, cracking, or peeling of the coating on any of the test panels, confirming that the coating possesses excellent durability.

[0129] [Table 8]

Claims

1. A two-component water-based paint composition comprising (A) an epoxy resin as the main component and (B) a resin that reacts with epoxy as the curing agent, The aforementioned paint composition further comprises (C) a pigment, (D) water, and (E) a silane coupling agent as a main component and / or curing agent. The paint composition satisfies at least one of the following conditions 1 and 2: A paint composition characterized in that the resin that reacts with the epoxy (B) is a polyamine resin and contains at least a modified polyamine having a cyclic structure. Condition 1: The paint composition comprises the (E) silane coupling agent as a main component, wherein the (E) silane coupling agent comprises at least the (E1) amino group-containing silane coupling agent, and the amount of the (E1) amino group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of the main component. Condition 2: The paint composition contains the (E) silane coupling agent as a curing agent, wherein the (E) silane coupling agent contains at least the (E2) epoxy group-containing silane coupling agent, and the amount of the (E2) epoxy group-containing silane coupling agent is 0.1 to 1.0% by mass relative to the total amount of the curing agent.

2. The coating composition according to claim 1, characterized in that the resin that reacts with the epoxy (B) is a modified polyamine having at least a cyclic structure, and has an active hydrogen equivalent of 80 to 350 g / eq.

3. The paint composition according to claim 1, characterized in that the epoxy resin (A) is a water-dispersible epoxy resin and has an epoxy equivalent of 150 to 1000 g / eq.

4. The paint composition according to claim 1, characterized in that the paint composition satisfies the above condition 1.

5. A method for forming a multilayer film, comprising: applying a primer to a substrate and drying it to form a primer film with a thickness of 50 to 150 μm; and applying a topcoat on the primer film and drying it to form a topcoat film with a thickness of 20 to 75 μm, The aforementioned undercoat paint is the paint composition according to any one of claims 1 to 4. A method for forming a multilayer film, characterized in that the topcoat paint is selected from the group consisting of acrylic resin-based paints, urethane resin-based paints, epoxy resin-based paints, silicone resin-based paints, and fluororesin-based paints.

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