Laminated coating for methanol tanks

Abstract

To provide a laminated coating for methanol tanks that suppresses the occurrence of white rust and has excellent corrosion resistance and methanol resistance (including aqueous methanol). [Solution] A laminated coating film for a methanol tank, comprising a corrosion-resistant coating film and a topcoat coating film, wherein the corrosion-resistant coating film is formed from a corrosion-resistant paint composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C), and the topcoat coating film is formed from a topcoat paint composition containing a siloxane-based binder (A2).

Description

Technical Field

[0001] The present invention relates to a laminated coating film for methanol tanks, a methanol tank with a laminated coating film, a coating composition kit for forming a laminated coating film for methanol tanks, and a method for producing a methanol tank with a laminated coating film.

Background Art

[0002] Conventionally, heavy oil has been mainly used as fuel for ships and the like. However, regulations on the emission amounts of nitrogen oxides, sulfur oxides, carbon dioxide and the like contained in exhaust gas have been tightened, and ships and the like using methanol as fuel have been proposed as an environmentally friendly and clean fuel.

[0003] Methanol tanks are used as tanks for using methanol as fuel and for transporting methanol. The methanol tank is a tank formed from a base material such as steel, and an anticorrosion coating film is formed on the surface of the tank to suppress corrosion of the base material.

[0004] As anticorrosion coating films, epoxy resin-based anticorrosion coating films are generally used. However, methanol has a great influence on organic anticorrosion coating films such as epoxy resin-based anticorrosion coating films, and long-term corrosion resistance cannot be expected with organic anticorrosion coating films. Therefore, the use of inorganic anticorrosion coating films instead of organic anticorrosion coating films has been studied.

[0005] As an inorganic anticorrosion coating film, an anticorrosion coating film formed from an inorganic zinc-rich coating composition is known. The inorganic zinc-rich coating composition is a coating composition that contains an inorganic resin such as a hydrolyzed condensate of silicate as a binder component and contains a large amount of zinc powder. It can prevent corrosion of base materials such as steel materials through the sacrificial anticorrosion effect of zinc and the formation of an oxide film with high barrier properties in corrosive environments, and thus is widely used for anticorrosion applications.

[0006] As an example of an inorganic zinc-rich paint composition, a paint composition containing zinc powder and a hydrolysis condensate of silicate as a binder component is known (e.g., Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-306638 [Overview of the project] [Problems that the invention aims to solve]

[0008] Although the anticorrosive coating formed from the inorganic zinc-rich paint composition exhibits good resistance to methanol, it was found that white rust occurs when the coating comes into contact with saltwater (e.g., seawater) or methanol (including aqueous methanol) because the coating contains a large amount of zinc powder, indicating that there is room for improvement in this respect.

[0009] This invention was made in view of the above, and aims to provide a laminated coating for methanol tanks that suppresses the occurrence of white rust and has excellent corrosion resistance and methanol resistance (including aqueous methanol). [Means for solving the problem]

[0010] The inventors of the present invention, after diligently studying to solve the aforementioned problems, found that the following configuration example can solve the aforementioned problems, and thus completed the present invention. The configuration example of the present invention is shown below.

[0011] [1] A laminated coating film comprising an anticorrosion coating film and a topcoat coating film, The aforementioned anticorrosion coating is a coating formed from an anticorrosion coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C). The aforementioned topcoat film is a coating film formed from a topcoat paint composition containing a siloxane-based binder (A2). Laminated coating for methanol tanks.

[0012] [2] The laminated coating film according to [1], wherein the siloxane-based binders (A1) and (A2) are condensates of at least one compound (a) selected from tetraalkoxysilane and alkyltrialkoxysilane.

[0013] [3] The laminated coating film according to [1] or [2], wherein the content of zinc powder (C) relative to 100% by mass of the solid content of the topcoat paint composition is 5% by mass or less.

[0014] [4] The laminated coating film according to any one of [1] to [3], wherein the weight-average molecular weight (Mw) of the siloxane-based binder (A2) is 500 to 10,000.

[0015] [5] A methanol tank with a laminated coating, wherein the laminated coating described in any of [1] to [4] is located on the methanol tank, with the corrosion-resistant coating side facing the methanol tank.

[0016] [6] A corrosion-preventive coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C), A topcoat paint composition containing a siloxane-based binder (A2) and A coating composition kit for forming a laminated coating film for methanol tanks, comprising the following features.

[0017] [7] Step 1 involves applying a corrosion-preventive coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C) to a methanol tank, drying it, and forming a corrosion-preventive coating film. Step 2 involves applying a topcoat paint composition containing a siloxane-based binder (A2) onto the aforementioned anticorrosion coating film and drying it to form a topcoat coating film. A method for manufacturing a methanol tank with a laminated coating. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a laminated coating film for methanol tanks that suppresses the occurrence of white rust and is excellent in corrosion resistance and methanol resistance (including water-containing methanol). MODE FOR CARRYING OUT THE INVENTION

[0019] Unless otherwise specified in the present specification, "methanol" refers to methanol used as fuel or the like, and includes water-containing methanol and the like. That is, unless otherwise specified in the present specification, "methanol" does not mean only 100% methanol, but refers to methanol including components that may be contained in methanol used as fuel or the like (e.g., impurities contained during methanol production).

[0020] <<Laminated Coating Film for Methanol Tanks>> The laminated coating film for a methanol tank according to the present invention (hereinafter also referred to as "the present laminated coating film") is a laminated coating film including an anticorrosion coating film and a top coating film, wherein the anticorrosion coating film is a coating film formed from an anticorrosion coating composition containing a siloxane-based binder (A1), an extender pigment (B) and zinc powder (C), and the top coating film is a coating film formed from a top coating composition containing a siloxane-based binder (A2).

[0021] The present laminated coating film is usually formed on a methanol tank in the order of methanol tank, anticorrosion coating film and top coating film for use. The present laminated coating film may be provided on the inner surface of the methanol tank, on the outer surface of the methanol tank, or on both the inner and outer surfaces of the methanol tank. From the viewpoint that the effects of the present invention are more exhibited, it is preferably provided at least on the inner surface of the methanol tank. When the present laminated coating film is provided on the inner surface of a methanol tank, the present laminated coating film may be provided on a part of the inner surface, but it is preferable to provide the present laminated coating film on at least a portion of the inner surface that is in contact with methanol, and it is more preferable to provide the present laminated coating film on the entire inner surface.

[0022] <Corrosion-resistant coating> The aforementioned anticorrosive coating is a coating formed from an anticorrosive paint composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C).

[0023] The thickness of the anticorrosion coating is preferably 15 μm or more, more preferably 30 μm or more, and even more preferably 70 μm or more, from the viewpoint that a laminated coating with particularly excellent corrosion resistance can be easily obtained, and preferably 300 μm or less, more preferably 200 μm or less, from the viewpoint that a laminated coating with excellent crack resistance can be easily obtained.

[0024] [Corrosion-preventive coating composition] The aforementioned anticorrosive coating composition contains a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C). The corrosion-preventive coating composition is preferably a so-called inorganic zinc-rich coating composition. The anticorrosion coating composition may be an organic solvent-based anticorrosion coating composition, or, from the viewpoint of reducing environmental impact, a water-based anticorrosion coating composition may also be used.

[0025] The anticorrosion coating composition may be a one-component composition, or it may be a two-component or more composition containing a first agent and a second agent. In particular, if the anticorrosion coating composition contains water, it is preferable that it be a two-component or more composition. When the anticorrosive coating composition is a two-component composition consisting of a first component and a second component, it is preferable that the siloxane-based binder (A1) is incorporated into the first component and the zinc powder (C) is incorporated into the second component. In particular, when the anticorrosive coating composition contains water, it is preferable that the siloxane-based binder (A1) and water are incorporated into the first component and the zinc powder (C) is incorporated into the second component. In this case, the extender pigment (B) may be incorporated into the first component, into the second component, or into both the first and second components. A preferred example of the aforementioned two-component composition is a one-liquid, one-powder composition consisting of a liquid first agent and a powdered second agent.

[0026] The first and second agents, etc., are usually stored, transported, etc., in separate containers, and are mixed together to form a corrosion-resistant paint composition before use (e.g., immediately before painting). In other words, these first and second agents, etc., can be considered components of a kit for preparing a corrosion-resistant paint composition. The first and second agents are agents that can be stored after being prepared and before the composition is prepared. For example, the siloxane-based binder-containing liquid and resin varnish described in the following examples are usually mixed with other components and used shortly after being prepared, and therefore do not fall under the category of the first and second agents.

[0027] [Siloxane-based binder (A1)] Siloxane-based binders (A1) are typically silicate condensates, specifically compounds obtained by hydrolysis and condensation of silicates. The siloxane-based binder (A1) may be used as a single agent or as a set of two or more agents.

[0028] The content of the siloxane-based binder (A1) in the anticorrosive coating composition is usually 1 to 15% by mass, preferably 2 to 10% by mass, and more preferably 3 to 8% by mass, based on 100% by mass of the solid content of the anticorrosive coating composition, in order to easily form an anticorrosive coating film with excellent corrosion resistance, crack resistance, and adhesion to methanol tanks. The content of the siloxane-based binder (A1) is the amount obtained by converting the mass of the siloxane-based binder (A1) to the mass of SiO2, that is, the amount obtained by converting the amount of substance (mol) of Si atoms contained in the siloxane-based binder (A1) to the mass of SiO2.

[0029] In this specification, the solid content of the anticorrosive coating composition, the topcoat coating composition, and each raw material refers to the residue (heated residue) obtained by heating each composition or each raw material containing volatile components such as solvents using a hot air dryer in accordance with JIS K 5601-1-2:2008 (heating temperature: 125°C, heating time: 60 minutes).

[0030] Examples of the siloxane-based binder (A1) include condensates of at least one compound (a) selected from tetraalkoxysilanes and alkyltrialkoxysilanes, and more specifically, partially hydrolyzed condensates of the compound (a) and / or its low-level condensates.

[0031] Examples of the tetraalkoxysilane include tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, tetra-i-propyl orthosilicate, tetra-n-butyl orthosilicate, and tetra-sec-butyl orthosilicate. Examples of the alkyltrialkoxysilane include methyltrialkoxysilanes such as methyltrimethoxysilane and methyltriethoxysilane.

[0032] Examples of low-level condensates of compound (a) include methyl polysilicate, ethyl polysilicate, and other low-level condensates of the tetraalkoxysilane. Low condensates are condensates with a degree of condensation of 2 to 20 (2 to 20 silicon atoms).

[0033] The low condensate is preferably a low condensate of tetraethyl orthosilicate. Examples of low condensates of tetraethyl orthosilicate include "ethyl silicate 45", "ethyl silicate 40", and "ethyl silicate 48" (all manufactured by Colcoat Co., Ltd.), "silicate 45" and "silicate 40" (both manufactured by Tama Chemical Industry Co., Ltd.), and "TES40WN" (both manufactured by Asahi Kasei Wacker Silicone Co., Ltd.). As the siloxane-based binder (A1), a partially hydrolyzed condensate of ethyl silicate 40 (manufactured by Colcoat Co., Ltd.) is particularly preferred.

[0034] The weight-average molecular weight (Mw) of the siloxane-based binder (A1) is typically 500 to 10,000, preferably 700 to 9,000, and more preferably 750 to 5,000. When the Mw of the siloxane-based binder (A1) is 500 or higher, it is easy to obtain a corrosion-resistant coating composition with excellent drying properties, and it tends to be easy to form a corrosion-resistant coating film with excellent corrosion resistance. On the other hand, when the Mw of the siloxane-based binder (A1) is 10,000 or lower, it tends to be easy to form a corrosion-resistant coating film with excellent crack resistance.

[0035] In this specification, the Mw of the siloxane-based binder is a value (polystyrene equivalent) obtained using a calibration curve created with polystyrene as the standard substance, based on values ​​measured by gel permeation chromatography (GPC). Specifically, it is measured by the method described in the examples below.

[0036] Siloxane-based binders (A1) can be produced using conventionally known methods, for example, by partially hydrolyzing and condensing one or more of the aforementioned compounds (a) and / or their low-level condensates in an organic solvent in the presence of an appropriate amount of water and, if necessary, a catalyst, so that Mw reaches a desired value.

[0037] Examples of organic solvents used in the aforementioned partial hydrolysis condensation reaction include the organic solvents listed in the section on organic solvents described later. One type of organic solvent may be used, or two or more types may be used.

[0038] The amount of water used in the aforementioned partial hydrolysis condensation reaction is usually 3 to 10 parts by mass, preferably 4 to 8 parts by mass, per 100 parts by mass of compound (a) and its low condensate.

[0039] Catalysts that can be used in the aforementioned partial hydrolysis condensation reaction include, for example, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; formic acid; organotin compounds such as dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin dimaleate, dioctyltin maleate, and tin octoate; phosphoric acid, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, and didecyl phosphate. Examples include phosphoric acid or phosphate esters such as phosphates; organic titanate compounds such as diisopropoxybis(acetylacetate)titanium and diisopropoxybis(ethylacetate)titanium; organic aluminum compounds such as tris(ethylacetate)aluminum and tris(acetylacetonate)aluminum; and organic zirconium compounds such as tetrabutylzirconate, tetrakis(acetylacetonate)zirconium, tetraisobutylzirconate, and butoxytris(acetylacetonate)zirconium. Among these, inorganic acids are preferred, and hydrochloric acid is more preferred, due to the good storage stability of the first agent. The catalyst may be one type or two or more types.

[0040] When a catalyst is used in the aforementioned partial hydrolysis condensation reaction, the amount of catalyst used is usually 0.01 to 2.0 parts by mass, preferably 0.02 to 1.0 parts by mass, per 100 parts by mass of the compound (a) and its low condensate.

[0041] When manufacturing the siloxane-based binder (A1), boron compounds, as described later, may be used. By introducing a structure derived from a boron compound into the siloxane-based binder (A1), a corrosion-resistant coating composition with excellent drying properties can be easily obtained. Examples of the boron compound include boric acid and boron trioxide. When a boron compound is used in the production of the siloxane-based binder (A1), the amount of the boron compound used is usually 0.3 to 11 parts by mass, preferably 2 to 6 parts by mass, per 100 parts by mass of the compound (a) and its low condensate.

[0042] The hydrolysis rate of the siloxane-based binder (A1) is preferably 35-75%, more preferably 38-63%. When the hydrolysis rate of the siloxane-based binder (A1) is within the aforementioned range, a corrosion-resistant coating composition with excellent drying properties can be easily obtained, and a corrosion-resistant coating film with excellent crack resistance can be easily formed. Furthermore, when a siloxane-based binder (A1) with a hydrolysis rate within the aforementioned range is used as the first agent, a first agent with superior storage stability can be easily obtained.

[0043] The hydrolysis rate (%) refers to the reaction rate of the reactive groups (alkoxy groups) contained in compound (a) and / or its low-level condensate when the siloxane-based binder (A1) is a partially hydrolyzed condensate of compound (a) and / or its low-level condensate, and can be calculated by the following formula 1. Hydrolysis rate (%)=(W / 18×2 / (S / E))×100 (Formula 1) In Equation 1, W is the mass (g) of water used in the preparation of the siloxane-based binder (A1), S is the mass (g) of the compound (a) and the low condensate, and E is the equivalent of the reaction groups of the compound (a) and the low condensate.

[0044] [Extender pigment (B)] The extender pigment (B) can be any pigment other than zinc powder (C), and conventionally known extender pigments can be used. The extender pigment (B) may be of one type or of two or more types.

[0045] Examples of extender pigments (B) include silica, talc, clay, kaolin, mica, feldspars (e.g., potassium feldspar, orthoclase, microcline, albite, anorthite), barium sulfate, bentonite, calcium carbonate, alumina, zinc oxide, magnesium carbonate, and barium carbonate, with silica, kaolin, mica, feldspars (especially potassium feldspar), and calcium carbonate being preferred.

[0046] The silica is preferably fine powder silica with an average primary particle diameter of 1 μm or less. The average primary particle diameter of the fine powder silica is preferably 5 to 100 nm. The specific surface area of ​​the fine silica powder is preferably 50 m². 2 It is 1 / g or more. The fine silica powder may be silica with a treated surface or silica without a treated surface. In this specification, the average primary particle diameter of nanoscale particles is the average value of the major axis of primary particles observed by an electron microscope.

[0047] The median diameter of the extender pigments other than silica is, for example, 0.1 to 50 μm. In this specification, the median diameter is measured by laser diffraction. The shape of the extender pigment (B) is not particularly limited, and pigments of various shapes such as spherical, needle-shaped, plate-shaped, flake-shaped, and fibrous can be used.

[0048] The content of the extender pigment (B) in the anticorrosive coating composition is preferably 3 to 70% by mass, more preferably 5 to 50% by mass, based on 100% by mass of the solid content of the anticorrosive coating composition, in order to easily obtain an anticorrosive coating composition with excellent storage stability and to easily form an anticorrosive coating film with excellent corrosion resistance, crack resistance, and adhesion to methanol tanks.

[0049] [Zinc powder (C)] The zinc powder (C) is not particularly limited in terms of shape, size, etc., and any zinc powder known in the paint field can be used. The zinc powder (C) may be of one type or of two or more types.

[0050] Examples of zinc powder (C) include metallic zinc powder and zinc alloy powder. Examples of zinc alloys include alloys of zinc with at least one selected from aluminum, magnesium, and tin.

[0051] The zinc powder (C) can take various forms, such as spherical or flaky shapes. The median diameter of the zinc powder (C) is preferably 1 to 30 μm.

[0052] The zinc powder (C) content in the anticorrosive coating composition is typically 30 to 95% by mass, preferably 50 to 92% by mass, and more preferably 65 to 90% by mass, based on 100% by mass of the solid content of the anticorrosive coating composition, in order to easily form an anticorrosive coating film with excellent long-term corrosion resistance.

[0053] [Other ingredients] The anticorrosive coating composition may also contain other components besides the siloxane-based binder (A1), extender pigment (B), and zinc powder (C), as long as they do not impair the effects of the present invention. Other components include known components that have been used in conventional zinc-rich paint compositions. Specific examples include organic resins, curing accelerators, thickeners (anti-sagging agents), organic solvents, water, rust-inhibiting pigments, coloring pigments, adhesion enhancers, film-forming aids, wetting agents, defoaming agents, antifreeze agents, leveling agents, dispersants, anti-settling agents, plasticizers, flame retardants, antifungal agents, UV absorbers, antioxidants, surfactants, and stabilizers. Each of these other components may be used individually or in combination of two or more.

[0054] • Organic resins The anticorrosive coating composition may also contain organic resins other than the siloxane-based binder (A1). When an organic resin is incorporated into a two-component anticorrosive coating composition containing a first component containing a siloxane-based binder (A1) and a second component containing zinc powder (C), it is preferable that the organic resin be incorporated into the first component. Examples of organic resins include butyral resins such as polyvinyl butyral resin and (meth)acrylic resins.

[0055] Examples of polyvinyl butyral resins include Esrec BM-1, Esrec BM-2, and Esrec BL-1 (product names; manufactured by Sekisui Chemical Co., Ltd.). An example of an acrylic resin is Dianaal BR-106 (product name; manufactured by Mitsubishi Chemical Corporation).

[0056] When an organic resin is incorporated into an anticorrosive coating composition, the amount of the organic resin is preferably 0.1 to 10% by mass, more preferably 0.2 to 8% by mass, relative to 100% by mass of the solid content of the anticorrosive coating composition, in order to easily obtain an anticorrosive coating composition with excellent paintability and to easily form an anticorrosive coating film with excellent crack resistance.

[0057] • Curing accelerator A curing accelerator may be added to the anticorrosive coating composition. If a boron compound is used when producing the siloxane-based binder (A1), and a siloxane-based binder (A1) containing the boron compound is obtained, the obtained siloxane-based binder (A1) containing the boron compound may be used as is in the anticorrosive coating composition. A curing accelerator acts, for example, as a curing catalyst when drying (curing) an anticorrosive paint composition to form a coating film.

[0058] Examples of curing accelerators include boric acid, boron trioxide and other boron compounds, oxalic acid, ferric chloride, and zinc chloride. Among these, boron compounds such as boric acid and boron trioxide are preferred because they allow for easy acquisition of corrosion-resistant coating compositions with excellent storage stability and easy formation of corrosion-resistant coating films with excellent crack resistance.

[0059] When a curing accelerator is added to an anticorrosive coating composition, the amount of the curing accelerator added is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, relative to 100% by mass of the solid content of the anticorrosive coating composition, in order to easily obtain an anticorrosive coating composition with excellent storage stability and drying properties, and to easily form an anticorrosive coating film with excellent crack resistance.

[0060] • Thickening agent The anticorrosive coating composition may contain a thickening agent. Any conventionally known thickening agent can be used without restriction. Examples of thickening agents include organic thickening agents such as polyamide wax, polyethylene wax, and oxidized polyethylene wax; and inorganic thickening agents such as bentonite and bentonite treated with quaternary ammonium salts (organic bentonite).

[0061] When a thickening agent is added to an anticorrosive coating composition, the amount of the thickening agent added is preferably 0.05 to 5% by mass, and more preferably 0.1 to 3% by mass, based on 100% by mass of the solid content of the anticorrosive coating composition.

[0062] • Organic solvents The anticorrosion coating composition may contain an organic solvent. If an organic solvent is used when producing the siloxane-based binder (A1), and a siloxane-based binder (A1) containing the organic solvent is obtained, the obtained siloxane-based binder (A1) containing the organic solvent may be used as is in the anticorrosion coating composition. When an organic solvent is added to a two-component anticorrosive coating composition containing a first component containing a siloxane-based binder (A1) and a second component containing zinc powder (C), it is preferable to add the organic solvent to the first component. Adding the organic solvent to the first component tends to improve the storage stability and pot life of the first component.

[0063] As the organic solvent, it is preferable to use at least one organic solvent (S1) selected from glycol ether solvents, ketone solvents, and acetate ester solvents, for example, because it improves the storage stability of the siloxane-based binder (A1). This is presumed to be because the silanol groups that the siloxane-based binder (A1) may contain are stabilized by forming hydrogen bonds with the oxygen atoms of the organic solvent (S1), thereby suppressing the condensation reaction.

[0064] Examples of glycol ether solvents include 1-methoxy-2-propanol (propylene glycol monomethyl ether) and propylene glycol monomethyl ether acetate, with 1-methoxy-2-propanol being preferred. Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, with methyl ethyl ketone being preferred. Examples of acetate ester solvents include ethyl acetate and butyl acetate, with ethyl acetate being preferred. Among these, glycol ether-based solvents are preferred, and 1-methoxy-2-propanol is more preferred.

[0065] The anticorrosion coating composition may contain an organic solvent (S2) other than the organic solvent (S1) because its drying properties can be easily adjusted. Examples of organic solvents (S2) include conventional organic solvents commonly used in anticorrosive coating compositions, such as alcohol-based solvents, aromatic solvents, and cellosolve-based solvents. Examples of alcohol-based solvents include methanol, ethanol, isopropanol, and butanol. Examples of aromatic solvents include benzene, xylene, and toluene. Examples of cellosolve-based solvents include methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

[0066] If the anticorrosion coating composition contains an organic solvent, the content of the organic solvent is preferably 10 to 60% by mass, more preferably 15 to 40% by mass, based on 100% by mass of the anticorrosion coating composition. If the first agent contains an organic solvent, the content of the organic solvent is preferably 10 to 95% by mass, more preferably 50 to 90% by mass, based on 100% by mass of the first agent.

[0067] ·water The anticorrosion coating composition may contain water. If water is used when manufacturing the siloxane-based binder (A1) and a siloxane-based binder (A1) containing water is obtained, the obtained siloxane-based binder (A1) containing water may be used as is in the anticorrosion coating composition. When a two-component anticorrosive coating composition containing a first component containing a siloxane-based binder (A1) and a second component containing zinc powder (C) contains water, the first component usually contains water.

[0068] <Topcoat film> The aforementioned topcoat film is a coating film formed from a topcoat paint composition containing a siloxane-based binder (A2). Because this laminated coating is formed on top of the aforementioned anticorrosion coating, the occurrence of white rust is suppressed, and it has excellent corrosion resistance and methanol resistance (even when exposed to methanol, peeling or dissolution (elution) of the top coating is almost nonexistent).

[0069] The thickness of the topcoat film is preferably 3 to 25 μm, more preferably 3 to 15 μm, and even more preferably 5 to 10 μm, from the viewpoint that the occurrence of white rust is suppressed and a laminated coating film with excellent methanol resistance can be easily obtained.

[0070] [Topcoat paint composition] The aforementioned topcoat paint composition contains a siloxane-based binder (A2). The topcoat paint composition preferably contains 5% by mass or less of the zinc powder (C) relative to 100% by mass of solids, and more preferably contains substantially no zinc powder (C), in order to easily obtain a laminated paint film in which the occurrence of white rust is further suppressed. A topcoat paint composition that is substantially free of zinc powder (C) means that zinc powder (C) is not used when preparing the topcoat paint composition. Specifically, the zinc powder (C) content in the topcoat paint composition is preferably 0.5% by mass or less, and more preferably 0% by mass, based on 100% by mass of the solid content of the topcoat paint composition.

[0071] [Siloxane-based binder (A2)] Siloxane-based binders (A2) are typically silicate condensates, specifically compounds obtained by hydrolysis and condensation of silicates. Specific examples and preferred examples of the siloxane-based binder (A2) are as described in the section for the siloxane-based binder (A1) above. The siloxane-based binder (A1) used in the anticorrosive coating composition and the siloxane-based binder (A2) used in the topcoat coating composition applied on the anticorrosive coating film formed from the anticorrosive coating composition may be the same siloxane-based binder or may be different siloxane-based binders. The siloxane-based binder (A2) may be used as a single agent or as a combination of two or more agents.

[0072] The weight-average molecular weight (Mw) of the siloxane-based binder (A2) is typically 500 to 10,000, preferably 700 to 9,000, and more preferably 750 to 5,000. When the Mw of the siloxane-based binder (A2) is 500 or higher, it tends to be easy to obtain a topcoat paint composition with excellent drying properties. On the other hand, when the Mw of the siloxane-based binder (A2) is 10,000 or lower, it tends to be easy to form a topcoat film with excellent crack resistance.

[0073] The content of the siloxane-based binder (A2) in the topcoat paint composition is preferably 60 to 100% by mass, more preferably 70 to 90% by mass, and even more preferably 80 to 87% by mass, based on 100% by mass of the solid content of the topcoat paint composition, in order to suppress the occurrence of white rust and to easily obtain a laminated coating film with excellent methanol resistance. The content of the siloxane-based binder (A2) is the amount obtained by converting the mass of the siloxane-based binder (A2) to the mass of SiO2, that is, the amount obtained by converting the amount of substance (moles) of Si atoms contained in the siloxane-based binder (A2) to the mass of SiO2.

[0074] [Other ingredients] The topcoat paint composition may contain other components besides the siloxane-based binder (A2), as long as they do not impair the effects of the present invention. Other components include known components that have been used in conventional paint compositions, and specific examples include organic resins, curing accelerators, thickeners (anti-sagging agents), organic solvents, water, extender pigments, rust-inhibiting pigments, coloring pigments, adhesion enhancers, film-forming aids, wetting agents, defoaming agents, antifreeze agents, leveling agents, dispersants, anti-settling agents, plasticizers, flame retardants, antifungal agents, UV absorbers, antioxidants, surfactants, and stabilizers. Specific examples of the organic resin, curing accelerator, thickener, organic solvent, and extender pigment are as described in the section on anticorrosive coating compositions. Each of these other components may be used individually or in combination of two or more.

[0075] The topcoat paint composition may also contain organic resins other than the siloxane-based binder (A2). When an organic resin is incorporated into a topcoat paint composition, the amount of the organic resin is preferably 5 to 15% by mass, more preferably 6 to 10% by mass, relative to 100% by mass of the solid content of the topcoat paint composition, in order to easily obtain a topcoat paint composition with excellent paintability and to easily form a topcoat film with excellent crack resistance.

[0076] The topcoat paint composition may contain an organic solvent. If the topcoat paint composition contains an organic solvent, the content of the organic solvent is preferably 10 to 95% by mass, more preferably 50 to 90% by mass, based on 100% by mass of the topcoat paint composition.

[0077] The topcoat paint composition may contain water. When the topcoat paint composition contains water, the amount of water is preferably 1.5 to 5% by mass, more preferably 1.5 to 4% by mass, even more preferably 1.5 to 3% by mass, and particularly preferably 1.5 to 2.5% by mass, based on 100% by mass of the topcoat paint composition, in order to easily form a topcoat paint film with excellent crack resistance.

[0078] ≪Method for manufacturing this laminated coating and methanol tank with laminated coating≫ In the methanol tank with a laminated coating according to the present invention, it is preferable that the laminated coating be on the methanol tank such that the corrosion-resistant coating side faces the methanol tank, in order to better demonstrate the effects of the present invention, and that the laminated coating be on at least the inner surface of the methanol tank such that the corrosion-resistant coating side faces the methanol tank.

[0079] Preferably, the laminated coating is formed on a methanol tank by a method comprising: step 1, applying the anticorrosive coating composition to a methanol tank and drying (curing) the applied anticorrosive coating composition to form the anticorrosive coating; and step 2, applying the topcoat coating composition onto the formed anticorrosive coating and drying (curing) the applied topcoat coating composition to form the topcoat coating. Since this method allows for the manufacture of a methanol tank with a laminated coating, this method can also be described as a method for manufacturing a methanol tank with a laminated coating.

[0080] The methanol tank is not particularly limited, and any tank used for using methanol as fuel or for transporting methanol can be used. A preferred example of the methanol tank is a methanol storage tank. The material of the methanol tank is not particularly limited and can be, for example, iron (iron, steel, ferroalloy, carbon steel, mild steel, alloy steel, etc.), non-ferrous metals (zinc, aluminum, copper, brass, galvanized, zinc sprayed, etc.), or stainless steel (SUS304, SUS410, etc.).

[0081] The methanol tank may be treated as necessary to remove rust, oil, moisture, dust, slime, salt, etc., and to improve the adhesion of the anti-corrosion coating that is formed (for example, blasting (ISO8501-1 Sa2 1 / 2), power tool treatment (ISO8501-1 St3), friction method, or degreasing to remove oil and dust). Furthermore, when using mild steel (such as SS400) as a methanol tank, it is desirable to prepare the surface by polishing the tank surface with grit blasting or similar methods as needed (e.g., adjusting the arithmetic mean roughness (Ra) to approximately 30-75 μm).

[0082] There are no particular restrictions on the method of applying the anticorrosive coating composition or the topcoat coating composition, and conventionally known methods can be used without limitation. However, spray painting such as air spray or airless spray, brush painting, and roller painting are preferred. When applying this coating, it is preferable to apply the coating so that the thickness of the formed anticorrosive coating film and topcoat coating film falls within the aforementioned range. When forming a corrosion-resistant coating or topcoat coating of the aforementioned thickness, the desired thickness can be formed in a single coat, or it can be formed in two (or more) coats.

[0083] There are no particular limitations on the method for drying (curing) the anticorrosive coating composition or the topcoat coating composition. To shorten the drying (curing) time, the composition may be dried by heating to about 5 to 60°C. However, a more common method is to leave the composition at room temperature in the atmosphere for about 1 to 14 days to dry it. Since the anticorrosive coating composition and the topcoat coating composition harden when the siloxane-based binder contained in these compositions undergoes a hydrolysis condensation reaction due to water in the composition or moisture (humidity) in the air, the humidity may be adjusted as necessary during the drying or hardening process.

[0084] ≪Laminated Coating Composition Kit for Methanol Tanks≫ The paint composition kit for forming a laminated coating film for methanol tanks according to the present invention comprises the anticorrosive paint composition and the topcoat paint composition. Using this kit, for example, a laminated coating for a methanol tank (a methanol tank with a laminated coating) can be formed in the same manner as the method for manufacturing a methanol tank with a laminated coating. [Examples]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0086] [Preparation Example 1] A siloxane-based binder-containing solution was prepared by charging 33.7 parts by mass of alkyl silicate, 47.5 parts by mass of 1-methoxy-2-propanol, 8.3 parts by mass of ethanol (industrial ethanol), 1.9 parts by mass of deionized water, and 0.1 parts by mass of 35% hydrochloric acid as a catalyst into container (1). Further, 1.2 parts by mass of boron trioxide was added to container (1), and the mixture was stirred at 25°C for 1 hour and 30 minutes, followed by 16 hours of cooling. In a separate container (2), 1.2 parts by mass of acrylic resin and 6.0 parts by mass of xylene were placed and stirred at 25°C for 30 minutes to prepare a resin varnish. Next, 7.2 parts by mass of resin varnish prepared in container (2) was added to the siloxane-based binder-containing liquid prepared in container (1), and the mixture was dispersed and stirred at 25°C until homogenized to prepare the first component.

[0087] The second component was prepared by mixing 280.0 parts by mass of zinc powder, 11.6 parts by mass of kaolin, 7.2 parts by mass of mica, and 1.2 parts by mass of calcium carbonate at 25°C.

[0088] The anticorrosive coating composition was prepared by placing the prepared (immediately after preparation) second agent and the first agent, which had been stored at 23°C for one month after preparation, into a polyethylene container and dispersing them with a high-speed disperser for 10 minutes.

[0089] [Preparation Examples 2-6] A corrosion-preventive coating composition was prepared by performing the same procedure as in Preparation Example 1, except that the type and amount (numerical value, parts by mass) of each raw material were changed as shown in Table 1. In preparation examples 5 and 6, the extender pigments listed in Table 1 were used in the container (2) when preparing the first agent, in the amounts (numerical values, parts by mass) listed in Table 1.

[0090] [Preparation Examples 7-10] Except for changing the types and quantities (numerical values, parts by mass) of each raw material as shown in Table 2, the same procedure as for the preparation of the first agent in Preparation Example 1 was followed. The obtained first agent was used as the topcoat paint composition.

[0091] [Comparative Preparation Example 1] A topcoat paint composition was prepared by mixing 30.0 parts by mass of 1-methoxy-2-propanol, 30.0 parts by mass of epoxy resin, and 40.0 parts by mass of xylene.

[0092] [Comparative Preparation Example 2] The first component was prepared by mixing 30.0 parts by mass of 1-methoxy-2-propanol, 30.0 parts by mass of epoxy resin, and 40.0 parts by mass of xylene. A topcoat paint composition was prepared by mixing 100.0 parts by mass of the prepared first component with 15.0 parts by mass of polyamidoamine (second component).

[0093] Table 3 shows the details of each ingredient listed in Tables 1 and 2.

[0094] <Weight-average molecular weight (Mw) of siloxane-based binders> The weight-average molecular weight (Mw) of the siloxane-based binder in the siloxane-based binder-containing solution (siloxane-based binder-containing solution immediately after preparation) prepared using the same method as in Preparation Examples 1 to 10 was measured by gel permeation chromatography (GPC) under the following measurement conditions. Each of the prepared siloxane-based binder-containing solutions was diluted with tetrahydrofuran (THF), and the resulting solutions were filtered through a membrane filter to obtain the solutions used as GPC measurement samples. (Measurement conditions) • Equipment: Waters Japan Ltd. 2695 Separation Module (Aliance GPC Multi-System) • Column: A column consisting of three TSKgel Super H4000, TSKgel Super H2000, and TSKgel Super H2000 columns, all manufactured by Tosoh Corporation, connected in series. ·Eluent:THF ·Flow rate: 0.6mL / min • Detector: Shodex RI-104 Column constant temperature bath temperature: 40°C • Standard material: Polystyrene

[0095] [Table 1]

[0096] [Table 2]

[0097] [Table 3]

[0098] [Examples 1-8 and Comparative Examples 1-3] On blast-treated steel plates (150 mm x 70 mm x 2.3 mm, Sa2 1 / 2 or higher), each anticorrosive coating composition prepared in Preparation Examples 1 to 6 (each anticorrosive coating composition listed in Table 4) was applied by air spray to a dry film thickness of 75 μm, and the coating was dried for one day at 25°C and 70% relative humidity to form an anticorrosive coating film. Test plates (steel plates with laminated coatings) were prepared by applying each topcoat paint composition prepared in Preparation Examples 7-10 and Comparative Preparation Examples 1-2 (topcoat paint compositions listed in Table 4) to the formed anticorrosive coating film using an air spray so that the dry film thickness was 8 μm, and then drying for 7 days at 25°C and 70% relative humidity to form the topcoat film. The blast-treated steel plate corresponds to a methanol tank.

[0099] <Saltwater resistance> In accordance with JIS K 5600-6-1:2016, the condition of the test plates was visually evaluated after immersion in a 3% salt solution at room temperature for 90 days, according to the corrosion resistance evaluation criteria below. If the corrosion resistance evaluation criterion below is 3 or 4, it can be said that there are no practical problems.

[0100] (Corrosion resistance evaluation criteria) 4. The laminated coating is free from blistering, peeling, and red rust from the steel plate, and the total area of ​​white rust on the laminated coating surface is 1% or less of the entire laminated coating surface. 3: The laminated coating does not have blistering, peeling, or red rust from the steel plate, but the total area of ​​white rust on the laminated coating surface exceeds 1% but is 5% or less of the entire laminated coating surface. 2: The laminated coating has slight blistering, peeling, and / or red rust from the steel plate, and the total area of ​​white rust on the laminated coating surface exceeds 5% but is 33% or less of the entire laminated coating surface. 1: The laminated coating has blistering, peeling, and / or red rust from the steel plate, and the total area of ​​white rust on the laminated coating surface exceeds 33% but is 100% or less of the entire laminated coating surface.

[0101] <Methanol tolerance> In accordance with JIS K 5600-6-1:2016, the condition of the test plates after immersion in methanol at room temperature for 90 days was visually evaluated according to the same corrosion resistance evaluation criteria as for saltwater resistance. Furthermore, the condition of the topcoat on the test plate after immersion was visually evaluated according to the coating film resistance evaluation criteria below. Only when the coating film resistance evaluation criterion below is 3 can it be said that there are no practical problems.

[0102] (Criteria for evaluating coating film resistance) 3: No peeling or dissolution of the topcoat film. 2: Less than 10% of the entire topcoat film surface is peeling or dissolving. 1: More than 10% of the entire topcoat film surface is peeling or dissolving.

[0103] <Water-resistant methanol-containing properties> In accordance with JIS K 5600-6-1:2016, the test plates were immersed in a solution of 95 parts by mass of methanol and 5 parts by mass of water at room temperature for 90 days. The condition of the test plates was then visually evaluated according to the same corrosion resistance evaluation criteria as for saltwater resistance. The condition of the topcoat film on the test plates after immersion was also visually evaluated according to the same coating film resistance evaluation criteria as for methanol resistance.

[0104] <Crack resistance> On blast-treated steel plates (150 mm x 70 mm x 2.3 mm, Sa2 1 / 2 or higher), each anticorrosive coating composition prepared in Preparation Examples 1 to 6 (each anticorrosive coating composition listed in Table 4) was applied by air spray to a dry film thickness of 200 μm, and dried at 25°C for one day to form an anticorrosive coating film. Test plates (steel plates with laminated coatings) were prepared by applying each topcoat paint composition prepared in Preparation Examples 7-10 and Comparative Preparation Examples 1-2 (topcoat paint compositions listed in Table 4) to the formed anticorrosive coating film using an air spray so that the dry film thickness was 15 μm, and then drying for 7 days at 25°C and 70% relative humidity to form the topcoat film. The condition of the laminated coating surface of the fabricated test boards was evaluated according to the crack resistance evaluation criteria described below. The blast-treated steel plate corresponds to a methanol tank.

[0105] (Crack resistance evaluation criteria) 4. No cracks were observed in the laminated coating even under a microscope (20x magnification). 3. When the laminated coating is observed under a microscope (20x magnification), cracks are visible in the laminated coating, but these cracks are not visible to the naked eye. 2: Visual inspection revealed cracks in a portion of the laminated coating. 1: Visual inspection reveals cracks across the entire surface of the laminated coating.

[0106] [Table 4]

Claims

1. A laminated coating film comprising a corrosion-resistant coating film and a topcoat coating film, The aforementioned anticorrosion coating is a coating formed from an anticorrosion coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C). The aforementioned topcoat film is a film formed from a topcoat paint composition containing a siloxane-based binder (A2). Laminated coating for methanol tanks.

2. The laminated coating film according to claim 1, wherein the siloxane-based binders (A1) and (A2) are condensates of at least one compound (a) selected from tetraalkoxysilane and alkyltrialkoxysilane.

3. The laminated coating film according to claim 1, wherein the content of zinc powder (C) relative to 100% by mass of the solid content of the topcoat paint composition is 5% by mass or less.

4. The laminated coating film according to claim 1, wherein the weight-average molecular weight (Mw) of the siloxane-based binder (A2) is 500 to 10,000.

5. A methanol tank with a laminated coating, wherein the laminated coating described in any one of claims 1 to 4 is provided on the methanol tank, such that the corrosion-resistant coating side faces the methanol tank.

6. A corrosion-preventive coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C), A topcoat paint composition containing a siloxane-based binder (A2) and A coating composition kit for forming a laminated coating film for methanol tanks, comprising the following features.

7. Step 1 involves applying a corrosion-preventive coating composition containing a siloxane-based binder (A1), an extender pigment (B), and zinc powder (C) to a methanol tank, and drying it to form a corrosion-preventive coating film. Step 2 involves applying a topcoat paint composition containing a siloxane-based binder (A2) onto the aforementioned anticorrosion coating and drying it to form a topcoat coating. A method for manufacturing a methanol tank with a laminated coating.

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