Coating composition and method for forming multi-layer coating film

Abstract

The present invention relates to a coating material composition which contains: an epoxy resin (A); an amine-based curing agent (B); barium sulfate (C) having an average particle diameter of 0.01-5.0 μm; and a zeolite (D). Relative to the total amount of solid content in the epoxy resin (A) and the amine-based curing agent (B), the content of the epoxy resin (A) is 60-99 mass%, the content of the amine-based curing agent (B) is 1-40 mass%, the content of the barium sulfate (C) is 1-100 mass%, and the content of the zeolite (D) is 10-40 mass%.

Description

[Technical Field]

[0001] The present invention relates to a coating composition having excellent corrosion resistance and finished appearance, and a method for forming a multi-layer coating film. [Background technology]

[0002] BACKGROUND ART In painting construction machinery or industrial machinery such as bulldozers, hydraulic excavators, and wheel loaders, various coating compositions are used depending on the desired performance requirements.

[0003] In recent years, manufacturers of construction and industrial machinery have been demanding improved corrosion resistance and finished appearance for their paints.

[0004] Patent Document 1 discloses a coating formation method that is excellent in drying and curing properties, thick film formation properties, corrosion resistance, etc., in which at least one type of coating-forming material is applied to a metal substrate, and is characterized in that the first coating-forming material contains an epoxy resin, an amine curing agent, a pigment, and a non-aqueous solvent.

[0005] Patent Document 2 discloses a paint composition containing an epoxy resin and / or a modified epoxy resin as a resin component, as a one-component primer paint composition that is particularly excellent in rust prevention for iron parts. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-140613 [Patent Document 2] Japanese Patent Publication No. 2008-106177 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the coating film obtained by the coating film formation method described in Patent Document 1 has insufficient corrosion resistance, and the finished appearance is also sometimes unsatisfactory.

[0008] Furthermore, the primer paint composition described in Patent Document 2 has insufficient corrosion resistance and insufficient wet-on-wet compatibility with the topcoat paint, which can result in an insufficient finished appearance for primer / topcoat paint specifications.

[0009] In view of the above-mentioned conventional situation, the problem to be solved by the present invention is to provide a coating composition having excellent corrosion resistance and finished appearance, and a method for forming a multilayer coating film having a coating film obtained from said coating composition. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by a composition containing an epoxy resin, an amine-based curing agent, barium sulfate having a specific average particle size range, and zeolite, and have thus completed the present invention.

[0011] That is, the present invention provides the following <1> ~ <5> It is related to. <1> A coating composition comprising an epoxy resin (A), an amine-based curing agent (B), barium sulfate (C) having an average particle size of 0.01 to 5.0 μm, and zeolite (D), A coating composition, wherein the content of the epoxy resin (A) is 60 to 99 mass%, the content of the amine curing agent (B) is 1 to 40 mass%, the content of the barium sulfate (C) is 1 to 100 mass%, and the content of the zeolite (D) is 10 to 40 mass%, based on the total solid content of the epoxy resin (A) and the amine curing agent (B). <2> the epoxy resin (A) contains an epoxy resin (A1) having a weight-average molecular weight of 350 to 10,000 and an epoxy resin (A2) having a weight-average molecular weight of 15,000 to 60,000; <1> The coating composition according to claim 1. <3> The amine-based curing agent (B) is at least one selected from polyamidoamine, modified aliphatic amine, phenalkamine, and phenalkamide. <1> or <2> The coating composition according to claim 1. <4> A method for forming a multilayer coating film, comprising a step of applying a topcoat coating film to an undercoat coating film on an object to be coated, As the undercoat coating composition for forming the undercoat coating film, <1> ~ <3> A method for forming a multilayer coating film using the coating composition according to any one of the above. <5> <1> ~ <3> 1. A construction machine or industrial machine coated with the coating composition according to any one of claims 1 to 9. [Effects of the Invention]

[0012] The coating composition of the present invention has excellent quick-drying properties because it uses an epoxy resin as the base resin. The coating composition of the present invention also has excellent reactivity because it uses an amine-based curing agent as the curing agent. Therefore, the coating composition of the present invention has excellent corrosion prevention properties.

[0013] Furthermore, the coating composition of the present invention uses barium sulfate having a specific small average particle size range as an extender pigment, which improves the smoothness of the resulting coating film, thereby enabling the production of a multi-layer coating film with an excellent finished appearance.

[0014] Furthermore, since the coating composition of the present invention uses zeolite as a water-absorbing material, it is possible to obtain a coating film that is excellent in water resistance and corrosion resistance.

[0015] Therefore, the coating composition of the present invention can provide a coating composition that is excellent in corrosion resistance and finished appearance, and the coating film obtained from the coating composition of the present invention can provide a multi-layer coating film that is excellent in corrosion resistance and finished appearance. DETAILED DESCRIPTION OF THE INVENTION

[0016] The coating composition of the present invention is a composition containing an epoxy resin (A), an amine-based curing agent (B), barium sulfate (C) having an average particle size of 0.01 to 5.0 μm, and zeolite (D). It will be described in detail below.

[0017] <Epoxy resin (A)> The epoxy resin (A) is preferably an aromatic epoxy resin obtained by reacting a polyphenol compound with epihalohydrin.

[0018] Examples of polyphenol compounds used to form the aromatic epoxy resin include bis(4-hydroxyphenyl)-2,2-propane [bisphenol A], bis(4-hydroxyphenyl)methane [bisphenol F], bis(4-hydroxycyclohexyl)methane [hydrogenated bisphenol F], 2,2-bis(4-hydroxycyclohexyl)propane [hydrogenated bisphenol A], 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-3-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolac, and cresol novolac.

[0019] As the epoxy resin (A) obtained by the reaction of a polyphenol compound with epichlorohydrin, an epoxy resin derived from bisphenol A can be preferably used.

[0020] Modified epoxy resins can also be used as the epoxy resin (A), such as fatty acid-modified epoxy resins, amine-modified epoxy resins, fatty acid amine-modified epoxy resins, urethane-modified epoxy resins, acrylic-modified epoxy resins, and polyester-modified epoxy resins.

[0021] Among these, it is preferable to use fatty acid modified epoxy resins, amine modified epoxy resins, fatty acid amine modified epoxy resins, etc. as modified epoxy resins.

[0022] Commercially available examples of these epoxy resins include Arakid 9201N, Arakid 9203N, Arakid 9205, Arakid 9208, and Modepics 401 (all of which are trade names manufactured by Arakawa Chemical Industries, Ltd.), EPICLON H-405-40, EPICLON H-304-40, EPICLON H-403-45, and EPICLON H-408-40 (all of which are trade names manufactured by DIC Corporation), EPOMIK R140, EPOMIK R301, EPOMIK R304, EPOMIK R307, EPOMIK U466BT60, EPOMIK U455CT60, EPOMIK U452CT60, EPOMIK 811, EPOMIK 872, and EPOMIK 891 (all of which are trade names manufactured by Mitsui Chemicals, Inc.).

[0023] The weight average molecular weight of the epoxy resin (A) is preferably within the range of 300 to 60,000, more preferably 500 to 50,000, and even more preferably 1,000 to 40,000, from the viewpoint of the finished appearance and the coating solid content concentration.

[0024] From the viewpoint of corrosion resistance and chipping resistance, the epoxy resin (A) preferably contains an epoxy resin (A1) having a weight average molecular weight of 350 to 10,000 and an epoxy resin (A2) having a weight average molecular weight of 15,000 to 60,000.

[0025] The weight average molecular weight of the epoxy resin (A1) is preferably 800 to 10,000, more preferably 1,500 to 10,000. The weight average molecular weight of the epoxy resin (A2) is preferably 15,000 to 55,000, more preferably 15,000 to 50,000.

[0026] The number average molecular weight or weight average molecular weight in the present specification is a value obtained by converting the number average molecular weight or weight average molecular weight measured using gel permeation chromatography (GPC) based on the molecular weight of standard polystyrene.

[0027] Specifically, the values ​​were determined using a gel permeation chromatograph "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) and four columns "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (trade names, all manufactured by Tosoh Corporation) under the following conditions: mobile phase tetrahydrofuran, measurement temperature 40°C, flow rate 1 mL / min, and detector RI.

[0028] From the viewpoint of adhesion, the epoxy resin (A) preferably has a hydroxyl value in the range of 50 to 300 mgKOH / g, more preferably 50 to 250 mgKOH / g, and even more preferably 50 to 200 mgKOH / g.

[0029] <Amine-based curing agent (B)> The amine-based curing agent (B) acts as a curing agent for the epoxy resin (A) and is a compound containing, in one molecule, an amino group or at least two groups capable of generating said amino group upon contact with water.

[0030] Examples of the amine curing agent (B) include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and diethylaminopropylamine; alicyclic polyamines such as 1,3-bisaminomethylcyclohexane and isophoronediamine; aromatic polyamines such as xylylenediamine, metaxylenediamine, diaminodiphenylmethane, and phenylenediamine; and modified products of these polyamines, such as polyamides, polyamidoamines, modified aliphatic amines, amine adducts with epoxy compounds, Mannich compounds, Michael adducts, ketimines, and aldimines.

[0031] Examples of the Mannich compounds include phenalkamine and phenalkamide.

[0032] Of the above, by using a ketimine compound, the coating composition of the present invention can be made into a one-pack type coating composition.

[0033] When a ketimine compound is used, among the above polyamine compounds, it is preferable to use a polyamine compound that does not have a secondary amino group in the molecule, that is, that has only a primary amino group that can be blocked with a carbonyl compound as an amino group having an active hydrogen atom, because this has good storage stability after mixing with an epoxy resin.When a ketimine compound that has a secondary amino group in the molecule is used, it is preferable to use it as an adduct compound in which the secondary amino group has been reacted with an epoxy compound to consume the secondary amino group.

[0034] The ketimine compound can be obtained by blocking the polyamine compound with a carbonyl compound. Examples of the carbonyl compound include ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl tert-butyl ketone, methyl sec-butyl ketone, methyl hexyl ketone, diethyl ketone, diisobutyl ketone, and cyclohexanone; and aldehydes such as acetaldehyde and benzaldehyde.

[0035] As the carbonyl compound, ketones can be preferably used from the viewpoint of achieving both curability and storage stability.

[0036] From the viewpoint of the drying properties and corrosion resistance of the coating composition of the present invention, among the above amine-based curing agents (B), polyamidoamines, modified aliphatic amines, phenalkamines, and phenalkamides can be preferably used.

[0037] Commercially available products of such amine-based curing agents (B) include, for example, Ancamide 2634, Ancamine 2089K (both manufactured by Evonik), NC-540, LITE-3100 (both manufactured by Cardrite), and the like.

[0038] The amine-based curing agent (B) can be used alone or in combination of two or more kinds.

[0039] The mixing ratio of the epoxy resin (A) and the amine curing agent (B) is usually such that the total amount of active hydrogen bonded to the amino groups in the amine curing agent (B) (including the generated amino groups) is 0.5 to 5 equivalents, and more preferably 0.6 to 3 equivalents, per equivalent of the epoxy groups in the epoxy resin (A).

[0040] In view of corrosion resistance and finished appearance, the coating composition of the present invention contains 60 to 99 mass % of epoxy resin (A), preferably 70 to 90 mass %, and 1 to 40 mass % of amine curing agent (B), based on the total solid content of the epoxy resin (A) and the amine curing agent (B), and preferably 10 to 30 mass %.

[0041] <Barium sulfate (C)> The coating composition of the present invention contains barium sulfate (C) having an average particle size of 0.01 to 5 μm, preferably 0.05 to 4 μm, and more preferably 0.05 to 3 μm (hereinafter, barium sulfate (C) having an average particle size of 0.01 to 5 μm will be simply abbreviated as barium sulfate (C)).

[0042] Examples of commercially available products of such barium sulfate (C) include BLANC FIXE MICRO (manufactured by Sachtraben K.K., trade name, barium sulfate having an average particle size of 0.7 μm), Barium Sulfate HF (manufactured by Shenzhen Jiaxin Chemical Co., Ltd., trade name, barium sulfate having an average particle size of 0.9 μm), Varifine BF-20 (manufactured by Sakai Chemical Industry Co., Ltd., trade name, barium sulfate having an average particle size of 0.03 μm), BARIACE B-30 (manufactured by Sakai Chemical Industry Co., Ltd., trade name, barium sulfate having an average particle size of 0.3 μm), and SPARWITE W-5HB (manufactured by Sino-Can Co., Ltd., trade name, barium sulfate powder, average particle size: 1.6 μm).

[0043] In this specification, the average particle size is a value obtained by measuring particle size distribution by dynamic light scattering.

[0044] Specifically, the average particle size is a value measured using, for example, UPA-EX250 (trade name, manufactured by Nikkiso Co., Ltd., a particle size distribution measuring device using dynamic light scattering).

[0045] From the viewpoint of finished appearance, the content of barium sulfate (C) in the coating composition of the present invention is 1 to 100 mass%, preferably 5 to 80 mass%, and more preferably 10 to 75 mass%, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B).

[0046] <Zeolite (D)> Zeolite is a general term for crystalline aluminosilicate, and its constituent elements are Al, Si, O, and cations (positive ions), and it has a tetrahedral structure of SiO4 and AlO4 (Si 4+ or Al 3+ Zeolites are compounds with a basic structure of a tetrahedron (a tetrahedron formed around a center). These pores are connected in a complex and regular pattern, forming one, two, or three dimensional regular pores, which are roughly the same size as small molecules with diameters of a few Å to a dozen Å, and are characteristic of zeolites. Cations exist within these pores, and these pores are the basis for the various functions of zeolites. Because only molecules smaller than the diameter of the pores can enter zeolites, and they can be screened out from larger molecules, some zeolites are called molecular sieves.

[0047] Zeolites include natural zeolites, primarily composed of hydrous aluminosilicates, and synthetic zeolites, primarily composed of Na2O·Al2O3·xSiO2·yH2O. Synthetic zeolites, also known as permite, are produced by either a dry process in which sodium carbonate, silica, alumina, or kaolin are eutecticized, or by a wet process in which sodium silicate and sodium aluminate are combined to form a gel. Both natural and synthetic zeolites possess ion exchange capacity, retain their crystalline structure even upon dehydration, and possess molecular-sized pores after dehydration, resulting in large adsorption capacity. Furthermore, zeolites produced by hydrothermal synthesis, in which sodium aluminosilicate gels are crystallized and dehydrated to yield pores of a certain size, are commonly referred to as molecular sieves.

[0048] By using barium sulfate (C) and zeolite (D) in combination, the water resistance of the coating composition of the present invention can be improved.

[0049] Zeolite (D) is preferably what is generally called a molecular sieve from the viewpoints of finishability and corrosion resistance. It is commercially available in powder or pellet form, and depending on the type of raw zeolite, it is commercially available as molecular sieve 3A, molecular sieve 4A, molecular sieve 5A, molecular sieve 13X, etc. The numbers indicate the approximate pore diameter (angstroms) of the zeolite, and the capital letters indicate the type of zeolite, with A representing LTA zeolite and X representing FAU zeolite.

[0050] Of the above molecular sieves, molecular sieve 3A and molecular sieve 5A, and particularly molecular sieve 5A, can be preferably used.

[0051] The effective diameter of the pores varies depending on the location and size of the metal cations near the pores of the molecular sieve crystal; for example, Type 5A is Type 4A in which the sodium ions are replaced with calcium ions.

[0052] From the viewpoint of finished appearance, the pore diameter (effective diameter of the pores) of the zeolite (D) is preferably 0.50 nm or less, more preferably 0.10 to 0.50 nm, and even more preferably within the range of 0.20 to 0.50 nm.

[0053] From the viewpoint of finished appearance, the content of the zeolite (D) in the coating composition of the present invention is 10 to 40 mass%, preferably 15 to 30 mass%, and more preferably 15 to 25 mass%, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B).

[0054] The coating composition of the present invention may contain an anti-rust pigment for the purpose of improving corrosion resistance. Specific examples of the anti-rust pigment include zinc oxide, phosphite compounds, phosphate compounds, molybdate compounds, bismuth compounds, and metal ion-exchanged silica.

[0055] Examples of the phosphite compounds include calcium phosphite compounds such as EXPERT NP-1000 and EXPERT NP-1020C, and aluminum phosphite compounds such as EXPERT NP-1100 and EXPERT NP-1102 (all of the EXPERT series are trade names manufactured by Toho Pigment Co., Ltd.).

[0056] Examples of the phosphate compound include aluminum dihydrogen tripolyphosphate treated with a metal compound, such as chlorides, hydroxides, carbonates, and sulfates of zinc, calcium, magnesium, manganese, bismuth, cobalt, tin, zirconium, titanium, strontium, copper, iron, lithium, aluminum, nickel, and sodium.

[0057] Commercially available aluminum dihydrogen triphosphate treated with the above metal compounds includes K-WHITE 140, K-WHITE Ca650, K-WHITE 450H, K-WHITE G-105, K-WHITE 105, and K-WHITE K-82 (all trade names manufactured by Teika Corporation).

[0058] Commercially available molybdate compounds include, for example, LF Bousei M-PSN, LF Bousei MC-400WR, LF Bousei PM-300, and PM-308 (all trade names manufactured by Kikuchi Color Co., Ltd.).

[0059] Examples of the bismuth compound include bismuth oxide, bismuth hydroxide, basic bismuth carbonate, bismuth nitrate, bismuth silicate, and organic acid bismuth.

[0060] Examples of the metal ion-exchanged silica include calcium ion-exchanged silica, magnesium ion-exchanged silica, etc. Phosphate-modified metal ion-exchanged silica can also be used as the metal ion-exchanged silica.

[0061] The calcium ion-exchanged silica is silica microparticles in which calcium ions have been introduced into a fine porous silica carrier by ion exchange. Commercially available calcium ion-exchanged silica products include SHIELDEX (registered trademark) C303, SHIELDEX C-3, and SHIELDEX C-5 (all manufactured by W.R. Grace & Co.), and Silomask 52 (manufactured by Fuji Silysia Chemical Ltd.).

[0062] The magnesium ion-exchanged silica is a fine silica particle in which magnesium ions are introduced into a fine porous silica support by ion exchange. Commercially available magnesium ion-exchanged silica products include Silomask 52M (Fuji Silysia Chemical Ltd.) and Novinox ACE-110 (SNCZ, France).

[0063] When an anti-rust pigment is used in the coating composition of the present invention, the amount used is preferably 1 to 50 mass %, more preferably 10 to 40 mass %, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B), from the viewpoints of corrosion prevention and finished appearance.

[0064] In order to achieve a desired color, color pigments can be used in the coating composition of the present invention. Specific examples of color pigments include titanium white, zinc molybdate, calcium molybdate, carbon black, graphite, iron black, Prussian blue, ultramarine, cobalt blue, copper phthalocyanine blue, indanthrone blue, yellow lead, synthetic yellow iron oxide, red iron oxide, transparent red iron oxide, bismuth vanadate, titanium yellow, zinc yellow, monoazo yellow, ochre, disazo, isoindolinone yellow, metal complex azo yellow, and quinophthalone. Examples of the pigments include yellow, benzimidazolone yellow, monoazo red, unsubstituted quinacridone red, azo lake (Mn salt), quinacridone magenta, anthanthrone orange, dianthraquinonyl red, perylene maroon, perylene red, diketopyrrolopyrrole chrome vermilion, chlorinated phthalocyanine green, brominated phthalocyanine green, pyrazolone orange, benzimidazolone orange, dioxazine violet, and perylene violet.

[0065] When a color pigment is used in the coating composition of the present invention, the amount used is preferably 20 to 150 mass %, particularly preferably 40 to 130 mass %, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B) from the viewpoint of finished appearance.

[0066] The coating composition of the present invention may contain an extender pigment (excluding barium sulfate (C)) as needed.

[0067] Examples of the extender pigment include clay, silica, barium sulfate (excluding barium sulfate (C)), talc, calcium carbonate, white carbon, diatomaceous earth, magnesium aluminum carbonate flakes, and mica flakes.

[0068] When an extender pigment is used in the coating composition of the present invention, the amount used is preferably 20 to 150 mass %, more preferably 40 to 140 mass %, and even more preferably 40 to 130 mass %, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B), from the viewpoint of water resistance and corrosion resistance.

[0069] A rheology control agent can be used in the coating composition of the present invention for the purpose of controlling the fluidity of the coating to improve the finished appearance and coating workability.

[0070] Specific examples of rheology control agents include clay minerals (e.g., metal silicates, montmorillonite), acrylic resins (e.g., those containing a structure consisting of an acrylic acid ester or methacrylic acid ester polymer or oligomer in the molecule), polyolefins (e.g., polyethylene, polypropylene, etc.), amides (higher fatty acid amides, polyamides, oligomers, etc.), polycarboxylic acids (including derivatives having at least two carboxyl groups in the molecule), cellulose (including various derivatives such as nitrocellulose, acetylcellulose, cellulose ether, etc.), urethanes (polymers, oligomers, etc. containing a urethane structure in the molecule), ureas (polymers, oligomers, etc. containing a urea structure in the molecule), and urethane ureas (polymers, oligomers, etc. containing a urethane structure and a urea structure in the molecule).

[0071] Commercially available rheology control agents include, for example, amide waxes such as Disparlon 6900 (Kusumoto Chemicals Co., Ltd.), Disparlon A603 (Kusumoto Chemicals Co., Ltd.), and Thixol W300 (Kyoeisha Chemical Co., Ltd.); polyethylene waxes such as Disparlon 4200 (Kusumoto Chemicals Co., Ltd.); CAB (cellulose acetate butyrate, Eastman Chemical Products Co.), HEC (hydroxyethyl cellulose), hydrophobic HEC, and CMC (carboxymethyl cellulose). Examples of rheology control agents include cellulose-based rheology control agents such as BYK-410, BYK-411, BYK-420, and BYK-425 (all manufactured by BYK-Chemie Co., Ltd.); urethane urea-based rheology control agents such as BYK-410, BYK-411, BYK-420, and BYK-425 (all manufactured by BYK-Chemie Co., Ltd.); polyolefin-based rheology control agents such as Floon SA-345HF (manufactured by Kyoeisha Chemical Co., Ltd.); and higher fatty acid amide-based rheology control agents such as Floon HR-4AF (manufactured by Kyoeisha Chemical Co., Ltd.).

[0072] When a rheology control agent is used in the coating composition of the present invention, the amount used is preferably within the range of 0.1 to 20 mass %, more preferably 0.5 to 15 mass %, and even more preferably 0.8 to 10 mass %, based on the total solid content of the epoxy resin (A) and the amine-based curing agent (B), from the viewpoints of finished appearance and coating workability.

[0073] The coating composition of the present invention may further contain, as necessary, a pigment dispersant, a surface conditioner, a surfactant, an antifoaming agent, a curing agent (excluding the amine-based curing agent (B)), a curing catalyst, a preservative, an antifreeze, etc.

[0074] In the coating composition of the present invention, a crosslinking reaction between the epoxy resin (A) as the base resin and the amine curing agent (B) usually proceeds at room temperature, except when the amine curing agent (B) is a ketimine compound. Therefore, the coating composition of the present invention is a two-component coating composition consisting of a base resin containing component (A) and a curing agent containing component (B), and is usually suitable for use by mixing the base resin and curing agent immediately before application and adding a solvent such as an organic solvent as necessary to adjust the viscosity.

[0075] In this case, it is generally preferred that components (C), (D), and any other components used as needed be blended into the base resin. Mixing can be carried out using a mixing device such as a disper or homogenizer.

[0076] The coating composition of the present invention can be applied by a coating method such as dip coating, brush coating, roll brush coating, spray coating, roll coating, spin coating, dip coating, bar coating, flow coating, electrostatic coating, airless coating, electrodeposition coating, die coating, etc. The dry film thickness is usually in the range of 10 μm to 150 μm, preferably 30 μm to 80 μm.

[0077] The coating composition of the present invention can be cured by drying for 10 to 120 minutes at room temperature to 160°C, preferably for 20 to 90 minutes at 60 to 120°C. In this specification, room temperature means 15 to 25°C.

[0078] Examples of substrates include cold-rolled steel sheets, black steel sheets, alloyed galvanized steel sheets, electro-galvanized steel sheets, etc., and construction or industrial machinery made from these materials, such as bulldozers, hydraulic excavators, wheel loaders, etc. These may be subjected to shot blasting, surface conditioning, surface treatment, etc., as necessary.

[0079] The coating composition of the present invention has excellent corrosion resistance and finished appearance, and can therefore be suitably used as a primer coating for the above-mentioned substrates, particularly as a primer coating composition for forming a primer coating film in a multilayer coating film consisting of a wet-on-wet primer coating film and a topcoat coating film.

[0080] The wet-on-wet coating method is a multi-layer coating process in which an upper coating film is formed on an uncured lower coating film.

[0081] The method for forming a multilayer coating film of the present invention is a method for forming a multilayer coating film that includes a step of applying a topcoat coating film to an undercoat coating film on an object to be coated, and is a method in which the coating composition of the present invention is used as an undercoat coating composition for forming the undercoat coating film.

[0082] The coating composition of the present invention has excellent wet-on-wet suitability and can therefore be particularly suitably used in a method of forming a coating film by forming an uncured coating film (undercoat coating film) from the coating composition of the present invention on a substrate, forming a topcoat coating film from the topcoat coating composition on the uncured coating film, and drying both coating films simultaneously.

[0083] As the topcoat paint composition for forming the topcoat paint film, any conventionally known paint composition can be used without limitation, specifically, for example, a urethane resin-based paint composition, an acrylic resin-based paint composition, a silicone resin-based paint composition, a fluororesin-based paint composition, an oil-based paint composition, a phthalic acid resin-based paint composition, etc.

[0084] In the above-mentioned wet-on-wet coating film forming method, the coating composition of the present invention can be applied by the coating method described above. The dry film thickness of the uncured coating film (undercoat coating) is usually in the range of 10 μm to 150 μm, preferably 20 μm to 60 μm.

[0085] The topcoat coating composition of the present invention can be applied to an uncured coating film by a coating method such as dip coating, brush coating, roll brush coating, spray coating, roll coating, spin coating, dip coating, bar coating, flow coating, electrostatic coating, airless coating, electrodeposition coating, or die coating. The dry thickness of the topcoat coating film is typically within the range of 10 μm to 150 μm, preferably 20 μm to 60 μm. A multilayer coating film can then be obtained by drying at room temperature to 160°C for 10 to 120 minutes, preferably 60 to 120°C for 20 to 90 minutes.

[0086] After the coating composition of the present invention has been applied to form the uncured coating film (primer coating film), setting or preheating at room temperature can be carried out as required. [Example]

[0087] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, "parts" means parts by mass, and "%" means % by mass.

[0088] Manufacture of primer coating composition Example 1 Preparation of Primer Coating Composition No. 1 Primer coating composition No. 1 was obtained by the following steps 1 and 2.

[0089] Step 1: An appropriate amount of butyl acetate was added to 40 parts (solids) of JER1001 (Note 1), 40 parts of BLANC FIXE MICRO (Note 4), 40 parts of TI-SELECT TS-6200 (Note 10), 20 parts of K-WHITE 105 (Note 11), 40 parts of SUNLITE SL-1500 (Note 12), 10 parts of TALC MS (Note 13), and 20 parts of MOLECULAR SIEVE 5A(P) (Note 14), and the mixture was dispersed in a sand mill to obtain a pigment dispersion paste.

[0090] Step 2: 40 parts (solids) of JER1001 (Note 1) was blended with the pigment dispersion paste obtained above, and a surface conditioner and antifoaming agent were added and stirred. Butyl acetate was added to adjust the solids content. Just before application, 20 parts (solids) of NC-540 (Note 17) and butyl acetate were added to obtain Primer Coating Composition No. 1 with a solids content of 60% by mass and a coating viscosity of 20 seconds at 25°C (measured with an Iwata cup).

[0091] Examples 2 to 16: Preparation of primer coating compositions Nos. 2 to 16 Primer coating compositions Nos. 2 to 16 were obtained in the same manner as in Example 1, except that the formulations shown in Tables 1 and 2 were used.

[0092] Comparative Examples 1 to 7: Preparation of Primer Coating Compositions Nos. 17 to 23 Primer coating compositions Nos. 17 to 23 were obtained in the same manner as in Example 1, except that the formulations shown in Table 3 were used.

[0093] In addition, in step 1 of coating composition No. 8, JER1001 (Note 1) was replaced with JER1007 (Note 2), and in step 1 of No. 18, JER1001 (Note 1) was replaced with Araquid 9205 (Note 3).

[0094] Preparation of topcoat paint composition Production Example 1: Production of acrylic resin solution 28 parts of Swazol 1000 (Cosmo Oil Co., Ltd., aromatic hydrocarbon solvent), 85 parts of toluene, 41.6 parts of styrene, 6.9 parts of n-butyl acrylate, 19 parts of isobutyl methacrylate, 15 parts of Placcel FM-3 (Note 21), 17 parts of 2-hydroxyethyl methacrylate, 0.5 parts of acrylic acid, and 8 parts of di-tert-butyl hydroperoxide were reacted under nitrogen gas at 110°C to obtain an acrylic resin solution with a solids concentration of 45% by mass. The resulting acrylic resin had an acid value of 3.9 mg KOH / g, a hydroxyl value of 94.9 mg KOH / g, and a weight-average molecular weight of 11,000.

[0095] (Note 21) Plaxel FM-3: Trade name, manufactured by Daicel Chemical Industries, Ltd., ε-caprolactone-modified vinyl monomer of 2-hydroxyethyl acrylate

[0096] Preparation Example 2 Preparation of topcoat paint composition No. 1 A base paint was prepared by blending 80 parts (solids) of the acrylic resin solution obtained in Preparation Example 1 with 12 parts of TI-SELECT TS-6200 (Note 10), 12 parts of Hoster Palm Yellow H-3G (Note 22), 15 parts of BARIFINE BF-20 (Note 7), 12 parts of Bayferrox 4905 (Note 23), and 1 part of TINUVIN 292 (Note 24). The solids were adjusted with Swazol 1000 (Cosmo Oil Co., Ltd., an aromatic hydrocarbon solvent). The mixture was dispersed in a sand mill to obtain a base paint. Just before application, 20 parts (solids) of Sumidur N3300 (Note 25) and 0.5 parts of KBM-403 (Note 26) were added and stirred to obtain topcoat paint composition No. 1 with a solids content of 60%.

[0097] (Note 22) Hoster Palm Yellow H-3G: Clariant, trade name, Hansa Yellow-based yellow pigment (Note 23) Bayferrox 4905: Lanxess Co., Ltd., product name, red pigment (Note 24) TINUVIN292: BASF Ltd., product name, light stabilizer (Note 25) Sumidur N3300: Sumika Covestro Urethane Co., Ltd., product name, isocyanurate-modified HDI (HDI trimer) (Note 26) KBM-403: Shin-Etsu Chemical Co., Ltd., trade name, epoxy group-containing silane coupling agent

[0098] <Preparation of multi-layer coated panels> Preparation of multi-layer coating plate No. 1 (for example) Multilayer coating film-formed coated plate No. 1 was obtained by the following steps 1 to 3.

[0099] Step 1: The primer coating composition No. 1 obtained in Example 1 was spray-coated onto a cold-rolled steel plate (size 0.8 x 70 x 150 mm, Palbond #3020) to a dry film thickness of 40 μm, and the mixture was allowed to set at 25°C for 3 minutes to form a primer coating film.

[0100] Step 2: Next, topcoat paint composition No. 1 obtained in Production Example 2 was used on the primer coating, and 10 parts of Kanpe Industrial Urethane Thinner 205 (a two-component urethane paint thinner manufactured by Kansai Paint Co., Ltd.) was mixed with 100 parts of topcoat paint composition No. 1, and sprayed wet-on-wet onto the primer coating to form a topcoat paint film with a dry film thickness of 40 μm.

[0101] Step 3: The multi-layer coating film obtained by the primer coating film in Step 1 and the topcoat coating film in Step 2 was set at 25°C for 10 minutes, then heated and dried at 80°C for 30 minutes, and further dried at room temperature (20°C) for 72 hours to obtain multi-layer coating film-formed coated board No. 1.

[0102] Preparation of multi-layer coating plates No. 2 to No. 16 (for examples) Multi-layer coating film-formed coated boards Nos. 2 to 16 were obtained in the same manner as multi-layer coating film-formed coated board No. 1, except that the primer coating compositions shown in Tables 1 to 2 were used.

[0103] Preparation of multi-layer coating plates No. 17 to No. 23 (for comparison) Multi-layer coating film-formed coated boards Nos. 17 to 23 were obtained in the same manner as multi-layer coating film-formed coated board No. 1, except that the primer coating composition was changed to each of the paints in Table 3.

[0104] Coating performance test Each multi-layer coating plate was subjected to coating performance tests for the test items described below. The test results are also shown in Tables 1 to 3.

[0105] Performance evaluation Finished appearance (Note 27): The painted surface appearance of each multi-layer coated board was evaluated visually and by 60-degree gloss value according to the following criteria.

[0106] ◎ indicates that there was no mixed layer between the top coat and primer coat, the smoothness was good, and the 60 degree gloss value was 90 or more. ◯ indicates that there was no mixed layer between the topcoat and primer coatings, the smoothness was good, and the 60 degree gloss value was 75 or more and less than 90. △ indicates that the topcoat and primer coatings were mixed together, and at least one of the following defects in the finished appearance were observed: waviness, matt discoloration, and chipped surface; and the 60-degree gloss value was 60 or more but less than 75. × indicates that the topcoat and primer coatings were significantly mixed together, and at least one of the finish appearances selected from undulation, mattness and chipping was significantly deteriorated, and the 60° gloss value was less than 60.

[0107] Corrosion resistance (Note 28): A cross-cut scratch was made with a knife on each multi-layer coating coated panel down to the base material, and then a 120-hour salt spray resistance test was conducted in accordance with JIS Z-2371. The rust and blister width from the knife cut were evaluated according to the following criteria.

[0108] ◎ indicates that the maximum width of the rust or blister was less than 2 mm (one side) from the cut part. ○ indicates that the maximum width of the rust or blister was 2 mm or more and less than 3 mm (one side) from the cut part. △ indicates that the maximum width of the rust or blister was 3 mm or more and less than 4 mm (one side) from the cut portion. × indicates that the maximum width of the rust or blister was 4 mm or more (on one side) from the cut part.

[0109] Chipping resistance (Note 29): Each multi-layer coated panel was fixed to the specimen holder of a chipping test device (Suga Test Instruments Co., Ltd., stone chipping tester "JA-400 type") so that the coated surface was perpendicular to the stone outlet. At 20°C, the test was performed at a pressure of 0.294 MPa (3 kgf / cm 2 500g of crushed granite stone (grain size 6) was sprayed onto the coating surface five times using compressed air. After that, adhesive cloth tape (manufactured by Fuji Kogyo Co., Ltd.) was applied to the coating surface and then quickly peeled off, after which the degree of scratches on the coating film was evaluated according to the following criteria.

[0110] ◎ indicates that the size of the scratch was 1.0 mm or less in diameter. A mark with a circle indicates that the size of the scratch was greater than 1.0 mm in diameter but less than 1.5 mm. △ indicates that the size of the scratch was more than 1.5 mm in diameter but not more than 2.0 mm. × indicates that the scratch size was greater than 2.0 mm in diameter.

[0111] [Table 1]

[0112] [Table 2]

[0113] [Table 3]

[0114] In Tables 1 to 3, the numerical values ​​shown for each component are the solid content.

[0115] (Note 1) JER1001: Mitsubishi Chemical Corporation, product name, bisphenol A epoxy resin, weight average molecular weight 2000, hydroxyl value 128 mg KOH / g (Note 2) JER1007: Mitsubishi Chemical Corporation, product name, bisphenol A epoxy resin, weight average molecular weight 10,000, hydroxyl value 188 mg KOH / g (Note 3) Arakyd 9205: Arakawa Chemical Industries, Ltd., trade name, modified bisphenol A epoxy resin, weight average molecular weight 30,000, hydroxyl value 215 mg KOH / g (Note 4) BLANC FIXE MICRO: Sachtraben Co., Ltd., product name, barium sulfate, average particle size 0.7 μm, oil absorption 13 ml / 100 g (Note 5) Barium sulfate HF: Shenzhou Jiaxin Chemical Co., Ltd., product name, barium sulfate, average particle size 0.9μm, oil absorption 14ml / 100g (Note 6) SPARWITE W-5HB: Sino-Can Micronized Product co., Ltd., product name, barium sulfate, average particle size 1.6μm, oil absorption 13ml / 100g (Note 7) BARIFINE BF-20: Sakai Chemical Industry Co., Ltd., product name, barium sulfate, average particle size 0.03 μm, oil absorption 24 ml / 100 g (Note 8) Barium sulfate BA: Sakai Chemical Industry Co., Ltd., product name, barium sulfate, average particle size 8 μm, oil absorption capacity 8 ml / 100 g (Note 9) LAKABAR SF: LAKAVISUTH LTD, trade name, barium sulfate, average particle size 10.4μm, oil absorption 10ml / 100g (Note 10) TI-SELECT TS-6200: Chemours Co., Ltd., product name, titanium dioxide (Note 11) K-WHITE 105: Product name, manufactured by Teika Corporation, aluminum dihydrogen triphosphate (Note 12) Sunlight SL-1500: Takehara Chemical Industry Co., Ltd., product name, calcium carbonate (Note 13) Talc MS: Nippon Talc Co., Ltd., product name, talc (Note 14) Molecular sieve 5A(P): Union Showa Co., Ltd., product name, sodium calcium amino silicate, pore size 0.42 nm (Note 15) Molecular sieve 3A: Union Showa Co., Ltd., product name, sodium calcium amino silicate, pore size 0.25 nm (Note 16) Molecular Sieve 13X: Union Showa Co., Ltd., product name, sodium calcium amino silicate, pore size 1.0 nm (Note 17) NC-540: Cardright Corporation, product name, Phenalkamine (Note 18) LITE-3100: Cardlite Corporation, product name, phenalkamide (Note 19) Ankamide 2634: Evonik Japan Co., Ltd., product name, polyamidoamine (Note 20) TMA K13: Tsuno Foods Co., Ltd., product name, ketimine, polyamidoamine ketone condensate

[0116] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2021-39032) filed on March 11, 2021, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0117] It is possible to provide a coated article having a coating film that is excellent in corrosion resistance and finished appearance.

Claims

1. A coating composition comprising an epoxy resin (A), an amine-based curing agent (B), barium sulfate (C) having an average particle size of 0.01 to 5.0 μm, and zeolite (D), A coating composition, wherein the content of the epoxy resin (A) is 60 to 99 mass%, the content of the amine curing agent (B) is 1 to 40 mass%, the content of the barium sulfate (C) is 1 to 100 mass%, and the content of the zeolite (D) is 10 to 40 mass%, based on the total solid content of the epoxy resin (A) and the amine curing agent (B).

2. 2. The coating composition according to claim 1, wherein the epoxy resin (A) contains an epoxy resin (A1) having a weight average molecular weight of 350 to 10,000 and an epoxy resin (A2) having a weight average molecular weight of 15,000 to 60,000.

3. 3. The coating composition according to claim 1, wherein the amine-based curing agent (B) is at least one selected from the group consisting of polyamidoamine, modified aliphatic amine, phenalkamine, and phenalkamide.

4. A method for forming a multilayer coating film, comprising a step of applying a topcoat coating film to an undercoat coating film on an object to be coated, A method for forming a multilayer coating film, comprising using the coating composition according to any one of claims 1 to 3 as an undercoat coating composition for forming the undercoat coating film.

5. A construction machine or industrial machine coated with the coating composition according to any one of claims 1 to 3.

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