Coating composition

Abstract

To provide a coating composition which forms a coating film having good adhesion to both an epoxy-based undercoating film and an old antifouling coating film as a lower layer, as well as good adhesion to an antifouling coating film formed from a silicone-based antifouling coating composition forming an upper layer.SOLUTION: There is provided a coating composition comprising an acrylic resin (A) having an acid value and an epoxy group-containing silane coupling agent (B), wherein the acrylic resin (A) has an acid value of 10 mgKOH / g or more and 35 mgKOH / g or less and a hydroxyl value of 10 mgKOH / g or more and 200 mgKOH / g or less, the content of the acrylic resin (A) in the solid content of the coating composition is 25 mass% or more and 50 mass% or less and the content of the epoxy group-containing silane coupling agent (B) in the solid content of the coating composition is 6 mass% or more and 25 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antifouling coating composition, a coating film using the same, a substrate with an antifouling coating film having the coating film, and a method for producing the same. [Background technology]

[0002] Self-polishing antifouling paint compositions are applied to ships, underwater structures, fishing equipment, etc. to prevent fouling caused by the adhesion of aquatic organisms, and prevent the adhesion of organisms by gradually releasing the antifouling agent contained in the paint. On the other hand, silicone-based antifouling paints, which do not necessarily require an antifouling agent to exhibit antifouling properties, have been attracting attention as environmentally friendly antifouling paints. For example, Patent Document 1 discloses an antifouling coating composition that is a curable organopolysiloxane composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-88653 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, when forming an antifouling coating film formed from a silicone-based antifouling paint such as the antifouling paint described in Patent Document 1 on a substrate, a primer coating film formed from a two-component curing epoxy-based paint was required. However, when a two-component curing epoxy-based paint was used as the primer layer, it was necessary to apply the silicone-based antifouling paint immediately after forming the primer layer, which posed a problem of significant operational constraints. Furthermore, when attempting to newly apply a silicone-based antifouling paint onto an old antifouling coating film formed by a self-polishing antifouling paint, conventionally, a two-component curing epoxy-based paint was applied as an undercoat layer onto the old antifouling coating film, and then the silicone-based antifouling paint was applied. However, because the two-component curing epoxy paint has high coating hardness, there was a problem in that the underlying self-polishing antifouling coating film, which has low coating hardness, would suffer internal fracture. An object of the present invention is to provide a coating composition that forms a coating film that has good adhesion to both an epoxy-based primer coating film and an underlying old antifouling coating film, and also has good adhesion to an overlying antifouling coating film formed from a silicone-based antifouling paint.A further object of the present invention is to provide a coating film formed from the coating composition, a substrate with an antifouling coating film having the coating film, and a method for producing the same. [Means for solving the problem]

[0005] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that the above-mentioned problems can be solved by a coating composition containing a specific amount of an acrylic resin (A) having a specific acid value and hydroxyl value, and further containing a specific amount of an epoxy group-containing silane coupling agent (B), thereby completing the present invention. The present invention relates to the following [1] to

[12] . [1] A coating composition comprising an acrylic resin (A) having an acid value and an epoxy group-containing silane coupling agent (B), wherein the acid value of the acrylic resin (A) is from 10 mgKOH / g to 35 mgKOH / g and the hydroxyl value is from 10 mgKOH / g to 200 mgKOH / g, the content of the acrylic resin (A) in the solid content of the coating composition is from 25% by mass to 50% by mass, and the content of the epoxy group-containing silane coupling agent (B) in the solid content of the coating composition is from 6% by mass to 25% by mass. [2] The coating composition according to [1], wherein the acid value of the solvent-soluble portion of the coating composition is 2 mg KOH / g or more and 10 mg KOH / g or less. [3] The coating composition according to [1] or [2], wherein the ratio of the active hydrogen equivalent (eq) of the epoxy curing agent to the epoxy group equivalent (eq) in the solid content of the coating composition (active hydrogen equivalent / epoxy group equivalent) is 0.05 or less. [4] The coating composition according to any one of [1] to [3], which is for use as an undercoat layer for an antifouling coating composition containing a curable silicone. [5] The coating composition according to [4], wherein the curable silicone is at least one curable silicone selected from the following (1) and (2): (1) Polyorganosiloxane having ketoxime groups at both ends (2) A polyorganosiloxane having hydroxy groups at both ends, and an organosilane represented by the following formula (I):

[0006] [ka] (In formula (I), R 1 represents a substituted or unsubstituted hydrocarbon group having from 1 to 10 carbon atoms, X is a ketoxime group, and a is 0 or 1.

[0007] [6] The coating composition according to [5], wherein the curable silicone is the curable silicone of (1). [7] The antifouling coating composition according to any one of [4] to [6], wherein the antifouling coating composition contains an amino group-containing silane coupling agent. [8] The coating composition according to any one of [1] to [7], which is for use in an undercoat layer formed on a coating film selected from the group consisting of an old antifouling coating film and a one-component or two-component epoxy-based undercoat coating film. [9] A coating film formed from the coating composition according to any one of [1] to [8].

[10] A substrate with an antifouling coating film, comprising, in this order: a substrate; the coating film according to [9]; and an antifouling coating film formed from an antifouling coating composition containing a curable silicone.

[11] A substrate with an antifouling coating film, comprising, in this order: a substrate; a one-component or two-component epoxy-based primer coating film; optionally a previous antifouling coating film; the coating film according to [9]; and an antifouling coating film formed from an antifouling paint composition containing a curable silicone.

[12] A method for producing a substrate with an antifouling coating film, comprising the following steps (1) to (4): Step (1): A step of applying or impregnating a substrate with the coating composition according to any one of [1] to [8] to obtain a coated or impregnated body. Step (2): A step of drying the coated or impregnated body obtained in step (1) to form a coating film. Step (3): A step of applying or impregnating the coating film with an antifouling coating composition containing a curable silicone to obtain a coated or impregnated body. Step (4): A step of drying and curing the coated or impregnated body obtained in step (3) to form a coating film. [Effects of the Invention]

[0008] According to the present invention, there is provided a coating composition which forms a coating film which has good adhesion to both an epoxy-based primer coating film and an underlying old antifouling coating film, and which also has good adhesion to an antifouling coating film formed from an upper layer of a silicone-based antifouling paint. Further, according to the present invention, there are provided a coating film formed from the coating composition, a substrate with an antifouling coating film having said coating film, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] The coating composition of the present invention, the antifouling coating film using the same, the substrate with the antifouling coating film, and the method for producing the same will be described in detail below.

[0010] [Paint composition] The coating composition of the present invention is a coating composition comprising an acrylic resin (A) having an acid value and an epoxy group-containing silane coupling agent (B), wherein the acrylic resin (A) has an acid value of from 10 mgKOH / g to 35 mgKOH / g and a hydroxyl value of from 10 mgKOH / g to 200 mgKOH / g, the content of the acrylic resin (A) in the solid content of the coating composition is from 25 to 50 mass%, and the content of the epoxy group-containing silane coupling agent (B) in the solid content of the coating composition is from 6 to 25 mass%. According to the present invention, there is provided a coating composition which forms a coating film which has good adhesion to both an epoxy-based primer coating film and an underlying old antifouling coating film, and which also has good adhesion to an upper antifouling coating film formed from a silicone-based antifouling paint. The detailed reasons why the above effects are obtained are unknown, but some of the reasons are thought to be as follows. It is believed that the coating composition of this embodiment, containing the epoxy group-containing silane coupling agent (B), provides good adhesion to the epoxy primer coating film. Also, when the old antifouling coating film contains an acrylic resin, it is believed that the coating composition of this embodiment, containing the acrylic resin (A), provides good adhesion. Furthermore, the coating composition of this embodiment contains an acrylic resin (A) having a specific acid value and hydroxyl value and an epoxy group-containing silane coupling agent (B). (B) It is believed that the interaction between the silicone-based antifouling paint and the silicone-based antifouling paint contributes to good adhesion to the antifouling coating film formed as an upper layer. The mechanism by which the effects of the present invention are obtained is not limited to the above. The coating composition of this embodiment will be described in detail below.

[0011] [Acrylic resin (A) having an acid value] The coating composition of this embodiment contains an acrylic resin (A) having an acid value (hereinafter simply referred to as "acrylic resin (A)"). The acrylic resin (A) is a resin having structural units derived from at least one selected from (meth)acrylic acid and its ester compounds. From the viewpoint of adhesion to the lower and upper layers, the acid value of the acrylic resin (A) is from 10 mgKOH / g to 35 mgKOH / g, preferably 10.5 mgKOH / g or more, more preferably 11 mgKOH / g or more, and preferably 30 mgKOH / g or less, more preferably 25 mgKOH / g or less, even more preferably 20 mgKOH / g or less, and still more preferably 15 mgKOH / g or less. The acid value of the acrylic resin (A) can be adjusted appropriately by adjusting the content of structural units derived from monomers having an acid group among the structural units constituting the acrylic resin (A). The acid group contained in the acrylic resin (A) is not particularly limited, but it is preferable that the acrylic resin (A) contains a carboxy group. The acid value of the acrylic resin (A) is measured by the method described in the examples.

[0012] Furthermore, from the viewpoint of adhesion to the upper layer and water resistance, the hydroxyl value of the acrylic resin (A) is from 10 mgKOH / g to 200 mgKOH / g, preferably from 20 mgKOH / g or more, more preferably from 30 mgKOH / g or more, even more preferably from 40 mgKOH / g or more, and preferably from 170 mgKOH / g or less, more preferably from 150 mgKOH / g or less, even more preferably from 130 mgKOH / g or less, still more preferably from 120 mgKOH / g or less, still more preferably from 110 mgKOH / g or less, still more preferably from 100 mgKOH / g or less, still more preferably from 90 mgKOH / g or less, still more preferably from 80 mgKOH / g or less, and still more preferably from 70 mgKOH / g or less. Acrylic resin (A) hydroxyl number can be appropriately adjusted by adjusting the content of structural units derived from monomers having a hydroxyl group in the structural units that constitute the acrylic resin (A). The hydroxyl value of the acrylic resin (A) is measured by the method described in the examples.

[0013] The acrylic resin (A) preferably has a structural unit derived from a monomer selected from the group consisting of (meth)acrylic acid, derivatives of (meth)acrylic acid, and other monomers. In this specification, "(meth)acrylic acid" means "acrylic acid or methacrylic acid", and "(meth)acrylate" means "acrylate or methacrylate". The acrylic resin (A) preferably has a structural unit derived from (meth)acrylic acid, from the viewpoint of adjusting the acid value within a desired range. Derivatives of (meth)acrylic acid include: aliphatic or alicyclic (meth)acrylic acid esters in which the alkyl group or cycloalkyl group has about 1 to 30 carbon atoms (about C6 to 30 for the cycloalkyl group), and in which a portion of the hydrogen atoms (H) contained in the alkyl group or cycloalkyl group may be substituted with an aromatic group such as a phenyl group, an alkoxy group of about C1 to C3, or the like, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, benzyl (meth)acrylate, dodecyl (meth)acrylate, or methoxyethyl (meth)acrylate; Hydroxyalkyl (meth)acrylates (OH group-containing unsaturated monomers) in which some of the hydrogen atoms (H) in an alkyl group (approximately C1 to C5) have been replaced with OH groups, such as hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; Silicon-containing (meth)acrylates (silicon-containing unsaturated monomers) such as (meth)acryloxypropylpolydimethylsiloxane; etc. Among these (meth)acrylic acid derivatives, it is preferred to contain one or more selected from aliphatic or alicyclic (meth)acrylic acid esters and hydroxyalkyl (meth)acrylates, as this provides excellent adhesion to the lower and upper layers.

[0014] Other monomers include styrenes such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as ethyl vinyl ether and isobutyl vinyl ether; Dibasic unsaturated monomers such as itaconic acid, maleic acid, and fumaric acid; etc.

[0015] In this embodiment, the acrylic resin (A) preferably has a structural unit derived from a styrene, a structural unit derived from a hydroxyalkyl (meth)acrylate, a structural unit derived from (meth)acrylic acid, and a structural unit derived from a (meth)acrylic acid alkyl ester, from the viewpoint of obtaining a coating film having the desired acid value and hydroxyl value and excellent adhesion to the lower and upper layers. That is, in this embodiment, the acrylic resin (A) is preferably an acrylic resin obtained by copolymerizing styrenes, hydroxyalkyl (meth)acrylate, (meth)acrylic acid, and (meth)acrylic acid alkyl ester. Each of the monomers may be used alone or in combination of two or more.

[0016] As the styrenes, styrene is preferred, and the content of styrenes in the raw material monomers of the acrylic resin (A) is preferably 0.5% by mass or more and 60% by mass or less. The number of carbon atoms in the alkyl group of the hydroxyalkyl (meth)acrylate is preferably 2 or more and 12 or less, more preferably 10 or less, even more preferably 8 or less, still more preferably 6 or less, even more preferably 4 or less, and still more preferably 2 or 3. The number of hydroxyl groups in one molecule of the hydroxyalkyl (meth)acrylate is preferably 1 or more and 3 or less, more preferably 1 or 2, and even more preferably 1. Preferred examples of hydroxyalkyl (meth)acrylates include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate, and among these, 2-hydroxyethyl (meth)acrylate is more preferred, and 2-hydroxyethyl methacrylate is even more preferred. The content of hydroxyalkyl (meth)acrylate in the raw material monomers of the acrylic resin (A) is preferably 5% by mass or more and 25% by mass or less, more preferably 7% by mass or more, and more preferably 20% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of obtaining a desired hydroxyl value. The (meth)acrylic acid is at least one selected from acrylic acid and methacrylic acid, and is preferably methacrylic acid. The content of (meth)acrylic acid in the raw material monomers of the acrylic resin (A) is preferably 1.5% by mass or more and 5.5% by mass or less, more preferably 5.0% by mass or less, and even more preferably 4.5% by mass or less, from the viewpoint of obtaining a desired acid value.

[0017] The number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester is preferably 1 or more and 16 or less, more preferably 12 or less, even more preferably 8 or less, still more preferably 6 or less, and even more preferably 4 or less. Preferred examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. The propyl (meth)acrylate may be n-propyl (meth)acrylate or isopropyl (meth)acrylate, but n-propyl (meth)acrylate is preferred from the viewpoint of availability and the viscosity of the resulting acrylic resin (A). The butyl (meth)acrylate may be n-butyl (meth)acrylate, isobutyl (meth)acrylate, or t-butyl (meth)acrylate, but n-butyl (meth)acrylate is preferred from the viewpoint of availability and the viscosity of the resulting acrylic resin (A). The content of alkyl (meth)acrylate in the raw material monomers of the acrylic resin (A) is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0018] The content of the acrylic resin (A) in the solid content of the coating composition is from 25% by mass to 60% by mass, preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 44% by mass or less, and still more preferably 42% by mass or less, from the viewpoint of adhesion to the lower and upper layers.

[0019] The weight average molecular weight of the acrylic resin (A) is not particularly limited as long as it is 1,000 or more, but from the viewpoint of coating film strength and coating viscosity, it is preferably 3,000 or more, more preferably 5,000 or more, even more preferably 7,000 or more, and is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 150,000 or less, still more preferably 75,000 or less, and even more preferably 50,000 or less. In the present invention, the "weight average molecular weight (Mw)" is measured using GPC (gel permeation chromatography) and calculated by converting it into a standard polystyrene having a known molecular weight. Specifically, it is measured by the method described in the examples.

[0020] The coating composition of this embodiment may contain, as a resin component, other resins in addition to the acrylic resin (A). Examples of other resins include resins other than acrylic resins, acrylic resins with an acid value of less than 10 mgKOH / g, acrylic resins with an acid value of more than 35 mgKOH / g, acrylic resins with a hydroxyl value of less than 10 mgKOH / g, and acrylic resins with a hydroxyl value of more than 200 mgKOH / g. Examples of resins other than acrylic resins include vinyl resins, and specific examples include resins having structural units derived from vinyl chloride, vinyl acetate, and vinyl alcohol. As other resins, commercially available products may be used, such as Solvine C series, A series, TA3 series, and M series (all manufactured by Nissin Chemical Industry Co., Ltd.).

[0021] The content of the other resins is not particularly limited, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and still more preferably 85 parts by mass or less, per 100 parts by mass of the acrylic resin (A).

[0022] [Epoxy group-containing silane coupling agent (B)] The coating composition of this embodiment contains an epoxy group-containing silane coupling agent (B). By containing the acrylic resin (A) and the epoxy group-containing silane coupling agent (B), a coating film with excellent adhesion to the lower and upper layers can be obtained. Specific examples of epoxy group-containing silane coupling agents include glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyl(ethyl)dimethoxysilane, 2-3,4-epoxycyclohexylethyltrimethoxysilane, 2-3,4-epoxycyclohexylethyltriethoxysilane, 8-glycidoxyoctyltrimethoxysilane, 8-glycidoxyoctylmethyldimethoxysilane, and 8-glycidoxyoctylmethyldiethoxysilane. Commercially available silane coupling agents may be used, and examples of such commercially available products include 3-glycidoxypropyltrimethoxysilane "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.) and "Sila-Ace S-510" (manufactured by JNC Corporation).

[0023] The content of the epoxy group-containing silane coupling agent (B) in the solid content of the coating composition is from 6% by mass to 25% by mass, preferably from 7% by mass to 8% by mass, more preferably from 8% by mass to 15% by mass, from the viewpoints of adhesion to the lower and upper layers and film-forming properties, and is preferably from 20% by mass to 15% by mass, more preferably from 15% by mass to 15% by mass.

[0024] [Pigment (C)] The coating composition of the present embodiment may contain a pigment, and examples of the pigment include a filler pigment, a coloring pigment, and whiskers. From the viewpoint of improving the coating film strength, it is preferable to contain a filler pigment. Examples of filler pigments include talc, mica, wollastonite, and other flat, flaky, or needle-shaped pigments. These pigments have a relatively high oil absorption capacity and can impart viscosity to the coating composition, thereby preventing sagging. Furthermore, mica, wollastonite, and other pigments impart strength to the coating film. Talc also relieves internal stress in the coating film, preventing cracking. The coating composition of this embodiment may also contain filler pigments such as potassium feldspar, silica powder, precipitated barium sulfate, elutriated barium sulfate, titanium oxide (also known as titanium white), zinc oxide, calcium carbonate, aluminum hydroxide, carbon black, and alumina. The coating composition of this embodiment may contain, as a coloring pigment, inorganic pigments such as titanium oxide, red iron oxide, yellow iron oxide, black iron oxide, and carbon black, and organic pigments such as naphthol red and phthalocyanine blue. Furthermore, in order to improve crack resistance, the coating composition of this embodiment may contain, in addition to the wollastonite, whiskers such as basic magnesium sulfate, potassium titanate, sepiolite, and xonotlite.

[0025] The content of the pigment (C) in the solid content of the coating composition is preferably 10% by mass or more and 69% by mass or less, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 35% by mass or more, and more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, and still more preferably 50% by mass or less, from the viewpoint of achieving a viscosity suitable for the coating and improving the coating film strength.

[0026] [Thixotropic Agent (D)] The coating composition of this embodiment preferably contains a thixotropic agent for the purpose of improving the anti-sagging properties of the coating and contributing to preventing sedimentation. Examples of thixotropic agents (anti-sagging agents, anti-settling agents) include organic bentonite, salts selected from the group consisting of Al, Ca, or Zn amine salts, stearate salts, lecithin salts, and alkylsulfonate salts; waxes selected from the group consisting of polyethylene wax, oxidized polyethylene wax, amide wax, hydrogenated castor oil wax, and polyamide wax; and synthetic finely powdered silica.

[0027] The thixotropic agent (anti-sagging / anti-settling agent) may be a commercially available product. Examples of such commercially available products include amide-based thixotropic agents such as "Disparlon A630-20X," "Disparlon 4200-20," and "Disparlon 6650" (all manufactured by Kusumoto Chemical Co., Ltd.), "ASA T-250F" (manufactured by Ito Oil Mills, Ltd.), and "Flornon RCM-300TL" (manufactured by Kyoeisha Chemical Co., Ltd.), organically modified bentonite-based viscosity modifier (hectorite / quaternary amine) "Bentone 38" (manufactured by Elementis Specialties Inc.), silicon dioxide-based thixotropic agent "Aerosil R972" (manufactured by Nippon Aerosil Co., Ltd.), and polyethylene oxide-based thixotropic agent "ASA D-120" (manufactured by Ito Oil Mills, Ltd.).

[0028] The thixotropic agent is used to prevent the precipitation of solid materials such as the pigment (C) during storage of the coating composition and to improve the coating workability during coating. The content of the thixotropic agent is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.3 mass % or more, even more preferably 0.5 mass % or more, and more preferably 10 mass % or less, even more preferably 5 mass % or less, and even more preferably 3 mass % or less, based on the solid content of the coating composition.

[0029] [Organic solvent (E)] The coating composition of this embodiment may contain an organic solvent (E) in order to maintain the viscosity of the coating composition low and improve coating workability. Examples of the organic solvent (E) include aromatic hydrocarbon organic solvents, aliphatic hydrocarbon organic solvents, alicyclic hydrocarbon organic solvents, ketone organic solvents, ester organic solvents, ether organic solvents, and alcohol solvents. Aromatic hydrocarbon organic solvents and ketone organic solvents are preferred, and aromatic hydrocarbon organic solvents are more preferred. Examples of the aromatic hydrocarbon organic solvent include toluene, xylene, mesitylene, Solvesso (registered trademark) 100, Solvesso 150, Solvesso 200, and the like. Examples of the aliphatic hydrocarbon organic solvent include pentane, hexane, heptane, and octane. Examples of the alicyclic hydrocarbon organic solvent include cyclohexane, methylcyclohexane, and ethylcyclohexane. Examples of the ketone organic solvent include acetylacetone, acetone, methyl ethyl ketone, methyl isobutyl ketone, and dimethyl carbonate, with dimethyl carbonate being preferred. Examples of the ester-based organic solvent include ethyl acetate, propyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate. An example of the ether-based organic solvent is butyl cellosolve. Examples of the alcohol-based organic solvent include isopropanol, isobutyl alcohol, n-butanol, and methoxypropanol.

[0030] The organic solvent (E) may be used alone or in combination of two or more kinds. When the coating composition of this embodiment contains an organic solvent (E), the content of the organic solvent (E) in the coating composition is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, from the viewpoint of improving coating workability, and is preferably 70% by mass or less, more preferably 60% by mass or less, from the viewpoint of suppressing sagging during coating and reducing the environmental load.

[0031] [Other ingredients] In addition to the components described above, the coating composition of this embodiment may contain, as appropriate, known components contained in coating compositions, such as an antifoaming agent, a dispersant / emulsifier, and an antifouling agent. As the defoaming agent, a fluorine-based, silicone-based, acrylic-based, or other defoaming agent can be used. Two or more types of defoaming agents may be used in combination. Commercially available defoaming agents can be used, such as "BYK-011" and "BYK-012" manufactured by BYK Japan Co., Ltd. When the coating composition of the present embodiment contains an antifoaming agent, the content of the antifoaming agent relative to 100 parts by mass of the solid content of the coating composition is preferably 0.0001% by mass or more, more preferably 0.0003% by mass or more, even more preferably 0.001% by mass or more, and preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 0.5% by mass or less.

[0032] The coating composition of the present embodiment may contain a dispersant or emulsifier, and preferably contains a dispersant or emulsifier to improve the dispersibility of pigments and the like in the coating composition and to emulsify them. Examples of dispersants and emulsifiers include nonionic surfactants and anionic surfactants. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene oxypropylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene oxypropylene alkyl phenyl ethers, polyoxyethylene distyryl phenyl ethers, polyoxyethylene oxypropylene distyryl phenyl ethers, and polyoxyethylene tristyryl phenyl ethers, and two or more of these may be used in combination. Examples of anionic surfactants include sulfate ester salts and phosphate ester salts of nonionic surfactants, polyoxyethylene alkyl ether carboxylate salts, alkylbenzene sulfonates, and alkylnaphthalene sulfonates, and two or more of these may be used in combination.

[0033] Furthermore, a polymer dispersant may be used as a dispersant / emulsifier. Examples of the polymer dispersant include (meth)acrylic resins and salts thereof such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid copolymer, and vinylnaphthalene-(meth)acrylic acid copolymer; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, and styrene-α-methylstyrene-(meth)acrylic acid copolymer. ) styrene-based resins such as acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, and styrene-maleic anhydride copolymers, and salts thereof; urethane-based resins and salts thereof, which are linear and / or branched polymer compounds (resins) containing urethane bonds formed by the reaction of an isocyanate group and a hydroxy group, and which may or may not have a crosslinked structure; polyvinyl alcohols; vinyl naphthalene-maleic acid copolymers and salts thereof; vinyl acetate-maleic acid ester copolymers and salts thereof; and water-soluble resins such as vinyl acetate-crotonic acid copolymers and salts thereof.

[0034] As the dispersant / emulsifier, known products may be used, such as DISPER BYK-187, DISPER BYK-190, DISPER BYK-191, DISPER BYK-194N, DISPER BYK-199 (manufactured by BYK-Chemie Co., Ltd.), Aron A-210, A6114 (manufactured by Toagosei Co., Ltd.), and DKS-NL100 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0035] The content of dispersant / emulsifier in the solid content of the coating composition is preferably 0.01 mass% or more and 5 mass% or less, more preferably 0.05 mass% or more, even more preferably 0.15 mass% or more, and more preferably 3 mass% or less, even more preferably 1 mass% or less.

[0036] The coating composition of this embodiment preferably contains a small amount of epoxy curing agent that reacts with the epoxy group of the epoxy group-containing silane coupling agent (B). That is, the epoxy group in the epoxy group-containing silane coupling agent (B) of this embodiment preferably remains unreacted. Note that the acrylic resin (A) does not correspond to the epoxy curing agent. The ratio of the active hydrogen equivalent (eq) of the epoxy curing agent to the epoxy group equivalent (eq) in the solid content of the coating composition of this embodiment (active hydrogen equivalent of epoxy curing agent / epoxy group equivalent) is preferably 0.05 or less, more preferably 0.03 or less, and even more preferably 0.01 or less. It is even more preferable that the coating composition does not contain an epoxy curing agent, i.e., it is 0.

[0037] [Physical properties of coating composition] <Acid value of solvent-soluble matter> The acid value of the solvent-soluble matter in the coating composition of this embodiment is preferably 2 mgKOH / g or more and 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, and even more preferably 10 mgKOH / g or less, from the viewpoint of good adhesion to the topcoat silicone coating film.

[0038] In the present invention, the "acid value of the solvent-soluble content" refers to the acid value of the component (mixture) that is soluble in a specific solvent, as described below, among the solid content excluding volatile components in the coating composition. The solvent-soluble components are thought to be mainly components that form the continuous phase of the coating film, such as resins and resin acids (rosin, versatic acid, etc.). The acid value of the solvent-soluble content is the average value of the acid values ​​of these components, and therefore indicates the overall acid concentration of the continuous phase of the coating film. It is thought that when this acid value is within the above range, the above-mentioned excellent effects can be obtained.

[0039] Acid value is defined as the amount (mg) of potassium hydroxide (KOH) required to neutralize 1 g of a target component, and is expressed in units of mgKOH / g. It is a widely used value to represent the acid group content of a target component. The acid value of the solvent-soluble content can be measured by a method conforming to JIS K 5601-2-1: 1999 for the solvent-soluble content obtained by extracting the composition with a solvent. As the solvent used for extraction, a xylene / ethanol mixed solution (xylene / ethanol=70 / 30 (mass ratio); all of the mixed solutions below have this mass ratio) is generally used from the viewpoint of dissolving components such as the resin that forms the continuous phase of the composition.

[0040] Specifically, the acid value of the solvent-soluble matter can be measured by, for example, a method that involves the following steps (1) to (6). (1) The weighed composition and a xylene / ethanol mixed solution having a mass approximately 10 times that of the composition are placed in a centrifuge tube and mixed thoroughly. (2) After centrifugation at 0°C and 3,500 rpm for 30 minutes, the supernatant is removed and transferred to another container. (3) Add the same amount of xylene / ethanol mixture as in (1) to the extraction residue again, mix, and centrifuge under the same conditions as in (2). Remove the supernatant and add it to the container containing the first supernatant. Repeat this process once more. (4) The total supernatant obtained from the three centrifugations is used as the extract, and the solids content (mass%) of this extract is measured. The solids content (mass%) is determined by weighing a portion of the extract, drying the weighed extract in a hot air dryer at 108°C for 3 hours, measuring the mass of the remaining solids, and calculating the proportion of the solids content (mass%) in the weighed extract. (5) Approximately 5 g of the extract is placed in a beaker, the mass of the extract is measured, and the mass of the solvent-soluble portion of the sample in the extract is calculated using the solid content percentage by mass obtained in (4) above, and this value is designated as x. The extract is diluted with ethanol to a total volume of 50 mL. (6) Add two drops of phenolphthalein-ethanol solution as an indicator to the ethanol diluted solution of the extract prepared in (5) above and 50 mL of ethanol as a blank, and titrate with 0.1 mol / L potassium hydroxide-ethanol solution. The titration is completed when the redness of the solution does not disappear for 30 seconds or more, and the acid value of the solvent-soluble matter is calculated according to the following formula.

[0041] AV={(V X -V0)×f×5.61} / x x: mass of sample (g) V X : Titration volume (mL) for diluted ethanol solution V0: Titration volume relative to the blank (mL) f: Factor of 0.1 mol / L potassium hydroxide solution used in titration

[0042] The solvent-soluble matter can be extracted and its acid value measured not only from the coating composition but also from the formed coating film by the same method.

[0043] <Hydroxyl value of solvent-soluble matter> The hydroxyl value of the solvent-soluble matter in the coating composition of this embodiment, from the viewpoint of good adhesion to the topcoat silicone coating film and the water resistance of the coating film, is preferably 2 mgKOH / g or more and 100 mgKOH / g or less, more preferably 3 mgKOH / g or more, even more preferably 5 mgKOH / g or more, and more preferably 50 mgKOH / g or less, even more preferably 30 mgKOH / g or less, and still more preferably 20 mgKOH / g or less.

[0044] In the present invention, the "hydroxyl value of the solvent-soluble component" refers to the hydroxyl value of a component (mixture) soluble in a specific solvent, obtained in the same manner as in measuring the acid value of the solvent-soluble component. The hydroxyl value of the solvent-soluble matter is measured as follows. The hydroxyl value is defined as the amount (mg) of potassium hydroxide (KOH) required to neutralize the acetic acid bonded to the hydroxyl groups after acetylating 1 g of the target component, and is expressed in units of mgKOH / g. It is a value that is widely used to express the hydroxyl group content of a target component. The hydroxyl value of the solvent-soluble portion can be measured by extracting the composition with a solvent and measuring the solvent-soluble portion by a method conforming to JIS K 0070: 1992. Methyl ethyl ketone is generally used as the solvent for extraction, as it dissolves components such as the resin that forms the continuous phase of the composition. Specifically, the hydroxyl value of the solvent-soluble matter can be measured by, for example, a method involving the following steps (1) to (9). (1) The weighed composition and approximately 10 times the mass of methyl ethyl ketone are placed in a centrifuge tube and mixed thoroughly. (2) After centrifugation at 0°C and 3,500 rpm for 30 minutes, the supernatant is removed and transferred to another container. (3) Add the same amount of methyl ethyl ketone as in (1) to the extraction residue, mix, and centrifuge under the same conditions as in (2). Remove the supernatant and add it to the container containing the first supernatant. Repeat this process once more. (4) The total supernatant obtained from the three centrifugations is used as the extract, and the solids content (mass%) of this extract is measured. The solids content (mass%) is determined by weighing a portion of the extract, drying the weighed extract in a hot air dryer at 108°C for 3 hours, measuring the mass of the remaining solids, and calculating the proportion of the solids content (mass%) in the weighed extract. (5) Approximately 5 g of the extract was placed in a flat-bottom flask, and 5 mL of an acetylation reagent (25 g of acetic anhydride with pyridine to a total volume of 100 mL) was added. As a blank measurement, only the acetylation reagent was placed in the flat-bottom flask. (6) Place a funnel on the mouth of the flat-bottom flask and heat in an oil bath at approximately 100°C for 1 hour. (7) After cooling, add 1 mL of water through the funnel and shake to decompose the acetic anhydride. Then, heat the flask in an oil bath at approximately 100°C for 10 minutes. (8) After cooling, wash the funnel and flask walls with 5 mL of ethanol and 30 to 50 mL of tetrahydrofuran (THF). (9) Add 2-3 drops of phenolphthalein indicator and titrate with 0.5 mol / L potassium hydroxide-ethanol solution. The titration ends when the redness of the solution does not disappear for 30 seconds or more. Calculate the hydroxyl value of the solvent-soluble portion according to the following formula.

[0045] A=[{(V0-V X )×f×28.05} / x]+AV A: Hydroxyl value V0: Titration volume relative to the blank (mL) V X : Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in titration f: Factor of 0.5 mol / L potassium hydroxide ethanol solution used in titration x: Mass (g) of sample AV: Acid value

[0046] <Viscosity> The viscosity of the paint composition of this embodiment is preferably 60 KU or more, more preferably 63 KU or more, still more preferably 65 KU or more, and preferably 85 KU or less, more preferably 80 KU or less, still more preferably 75 KU or less. The viscosity of the paint composition is measured by the method described in the examples.

[0047] <VOC content> The VOC (volatile organic compound) content of the paint composition of this embodiment is preferably low from the viewpoints of reducing environmental load and work load, preferably 700 g / L or less, more preferably 650 g / L or less, still more preferably 620 g / L or less, and from the viewpoint of setting the viscosity within a desired range, preferably 350 g / L or more, more preferably 400 g / L or more, still more preferably 450 g / L or more. The VOC content in the paint composition can be calculated from the composition of the paint composition and the specific gravity of each component. Also, when measuring the VOC content from the obtained paint composition, it is measured in accordance with ISO 11890-1. In addition, solvents exempted from VOC are defined in the regulations of each country. For example, in the United States, dimethyl carbonate is an organic solvent exempted from VOC.

[0048] 〔Use of paint composition〕 The paint composition of this embodiment is preferably used as an undercoat layer for an antifouling paint composition containing curable silicone. <Antifouling paint composition containing curable silicone> The antifouling coating composition containing the curable silicone (hereinafter also simply referred to as the antifouling coating composition) preferably contains at least one curable silicone (a) selected from the following (1) and (2): (1) Polyorganosiloxane having ketoxime groups at both ends (2) A polyorganosiloxane having hydroxy groups at both ends, and an organosilane represented by the following formula (I):

[0049] [ka] (In formula (I), R 1 represents a substituted or unsubstituted hydrocarbon group having from 1 to 10 carbon atoms, X is a ketoxime group, and a is 0 or 1.

[0050] (Curable silicone (a)) The curable silicone (a) is selected from the above (1) or (2). From the viewpoint of curability, the curable silicone (a) is preferably the above curable silicone (1). Each of these will be described in detail below. <(1) Polyorganosiloxane having ketoxime groups at both ends> The polyorganosiloxane having ketoxime groups at both ends (hereinafter also referred to as "polyorganosiloxane (a1)") has at least a polyorganosiloxane structure as the main chain and a reactive site having a ketoxime group, and has the reactive site at both ends. The main chain has a polyorganosiloxane structure, such as a polydimethylsiloxane structure or a polymethylphenylsiloxane structure, with a polydimethylsiloxane structure being preferred. The main chain may contain alkylene groups or polyoxyalkylene groups in block form. Furthermore, as a linking site between the main chain and the reactive site, for example, an alkylene group or a polyoxyalkylene group may be present. The reactive sites of the polyorganosiloxane (a1) react with each other or with the organosilicon crosslinking agent (f) contained in the antifouling coating composition to form a crosslinked structure, resulting in a cured silicone product and forming an antifouling coating film. They may also react with the silane coupling agent (g) to form part of the cured silicone product.

[0051] The reactive site preferably has a ketoximesilyl group, and the reactive site is preferably located at both ends of the main chain. The polyorganosiloxane having ketoxime groups at both ends is preferably a compound represented by the following formula (II).

[0052] [ka] (In formula (II), R 11 , R 12 each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogenated alkyl group; R 21 ~R 24 each independently represents an alkyl group having 1 to 4 carbon atoms, n represents an integer of 10 or more and 10,000 or less, and a represents an integer of 1 or more and 3 or less.

[0053] In formula (II), n represents an integer of 10 or more and 10,000 or less, preferably 100 or more and 1,000 or less, and may be appropriately selected so that the kinematic viscosity and weight average molecular weight described below fall within suitable ranges. a represents an integer of 1 or more and 3 or less, preferably 1 or 2, and more preferably 2. R 11 and R 12 each independently represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkenyl group having from 2 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms, an aralkyl group having from 7 to 10 carbon atoms, or a halogenated alkyl group having from 1 to 10 carbon atoms.11 may be the same or different, and R 12 When there are multiple 12 may be the same or different. The alkyl group preferably has 1 or more and 6 or less, more preferably 1 or more and 3 or less, even more preferably 1 or 2, and still more preferably 1 carbon atom. The alkenyl group preferably has 2 or more and 6 or less carbon atoms, more preferably 2 or more and 3 or less carbon atoms, and a vinyl group (-CH=CH2) is particularly preferred. The alkoxy group preferably has 1 or more and 6 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or 2 carbon atoms. The aryl group preferably has 6 or more and 8 or less carbon atoms, and may have a substituent such as an alkyl group on the aromatic ring. Examples include a phenyl group, a tolyl group (methylphenyl group), a xylyl group (dimethylphenyl group), and a naphthyl group. The number of carbon atoms in the aralkyl group is preferably 7 or more and 9 or less, and examples thereof include a benzyl group, a 2-phenylethyl group, a 2-naphthylethyl group, and a diphenylmethyl group. The number of carbon atoms in the halogenated alkyl group is preferably 1 or more and 6 or less, and examples thereof include groups in which some or all of the hydrogen atoms contained in the alkyl group have been replaced with halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Among these, R 11 is preferably a methyl group, and R 12 is preferably a vinyl group.

[0054] In formula (II), R 21 ~R 24 Each independently represents an alkyl group having 1 to 4 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. Among these, -ON=C(R 21 R 22 ) or -ON=C(R 23 R 24) is preferably a dimethyl ketoxime group, a methyl ethyl ketoxime group, a diethyl ketoxime group, a methyl isopropyl ketoxime group, or a methyl isobutyl ketoxime group.

[0055] <(2) Polyorganosiloxane having hydroxy groups at both ends, and organosilane represented by formula (I)> The polyorganosiloxane having hydroxy groups at both ends (hereinafter also referred to as "polyorganosiloxane (a2)") has at least a polyorganosiloxane structure as the main chain and a reactive site having a hydroxy group, and has the reactive site at both ends. The main chain has a polyorganosiloxane structure, such as a polydimethylsiloxane structure or a polymethylphenylsiloxane structure, with a polydimethylsiloxane structure being preferred. The main chain may contain alkylene groups or polyoxyalkylene groups in block form. Furthermore, as a linking site between the main chain and the reactive site, for example, an alkylene group or a polyoxyalkylene group may be present. The silanol groups react with an organosilane represented by the formula (I) described below (hereinafter also referred to as "organosilane (a3)") to obtain a polyorganosiloxane (polyorganosiloxane (a1)) having ketoxime groups at both ends. The polyorganosiloxane (a2) reacts with the reactive sites of the polyorganosiloxane (a1) obtained by the above reaction or with the organosilicon crosslinking agent (f) contained in the antifouling coating composition to form a crosslinked structure, becoming a silicone cured product and forming an antifouling coating film. It may also react with the silane coupling agent (g) to form part of the silicone cured product.

[0056] The polyorganosiloxane (a2) is preferably a compound represented by the following formula (III).

[0057] [ka] (In formula (III), p represents an integer of 10 or more and 10,000 or less, b represents an integer of 1 or more and 3 or less, and R 13 and R 14 each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogenated alkyl group.

[0058] In formula (III), p represents an integer of 10 or more and 10,000 or less, preferably 100 or more and 1,000 or less, and may be appropriately selected so that the viscosity and weight average molecular weight described below fall within suitable ranges. b represents an integer of 1 or more and 3 or less, preferably 1 or 2, and more preferably 1. R 13 and R 14 each independently represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkenyl group having from 2 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms, an aralkyl group having from 7 to 10 carbon atoms, or a halogenated alkyl group having from 1 to 10 carbon atoms. 13 may be the same or different, and R 14 When there are multiple 14 may be the same or different. The alkyl group preferably has 1 or more and 6 or less, more preferably 1 or more and 3 or less, even more preferably 1 or 2, and still more preferably 1 carbon atom. The alkenyl group preferably has 2 or more and 6 or less carbon atoms, more preferably 2 or more and 3 or less carbon atoms, and is further preferably a vinyl group (-CH=CH2). The alkoxy group preferably has 1 or more and 6 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or 2 carbon atoms. The aryl group preferably has 6 or more and 8 or less carbon atoms, and may have a substituent such as an alkyl group on the aromatic ring. Examples include a phenyl group, a tolyl group (methylphenyl group), a xylyl group (dimethylphenyl group), and a naphthyl group. The number of carbon atoms in the aralkyl group is preferably 7 or more and 9 or less, and examples thereof include a benzyl group, a 2-phenylethyl group, a 2-naphthylethyl group, and a diphenylmethyl group. The number of carbon atoms in the halogenated alkyl group is preferably 1 or more and 6 or less, and examples thereof include groups in which some or all of the hydrogen atoms contained in the alkyl group have been replaced with halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Among these, R 13 and R 14 is preferably a methyl group.

[0059] The organosilane (a3) ​​is represented by the following formula (I):

[0060] [ka] (In formula (I), R 1 represents a substituted or unsubstituted hydrocarbon group having from 1 to 10 carbon atoms, X is a ketoxime group, and a is 0 or 1.

[0061] In formula (I), a is 0 or 1, and is preferably 1 from the viewpoint of the reactivity of the resulting polyorganosiloxane having methyl isobutyl ketoxime groups at both ends. R 1 represents a hydrocarbon group having 1 to 10 carbon atoms, and is preferably an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. The alkyl group preferably has 1 or more and 6 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or 2 carbon atoms. The alkenyl group preferably has 2 or more and 6 or less carbon atoms, more preferably 2 or more and 3 or less carbon atoms, and is preferably a vinyl group (-CH=CH2). Among these, R 1 is preferably a vinyl group. X is preferably a dimethyl ketoxime group, a methyl ethyl ketoxime group, a diethyl ketoxime group, a methyl isopropyl ketoxime group, or a methyl isobutyl ketoxime group.

[0062] The polyorganosiloxane (a2) and the organosilane (a3) ​​may be mixed with reference to the stoichiometric ratio, and it is preferable to add an excess amount of the organosilane (a3) ​​relative to the stoichiometric ratio. Specifically, the amount of organosilane (a3) ​​blended per 100 parts by mass of polyorganosiloxane (a2) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less.

[0063] From the viewpoint of improving coating workability, the curability of the antifouling coating composition, and the strength of the coating film formed, the weight average molecular weight (Mw) of the curable silicone (a) is preferably 500 or more, more preferably 5,000 or more, even more preferably 10,000 or more, still more preferably 15,000 or more, still more preferably 20,000 or more, and is preferably 1,000,000 or less, more preferably 100,000 or less, still more preferably 50,000 or less, and still more preferably 40,000 or less.

[0064] From the viewpoint of improving the ease of production of the antifouling coating composition, the ease of application of the antifouling coating composition, its curability, and the strength and flexibility of the coating film formed, the viscosity of the curable silicone (a) at 25°C is preferably at least 20 mPa·s, more preferably at least 100 mPa·s, even more preferably at least 500 mPa·s, and even more preferably at least 1,000 mPa·s, and is preferably at most 100,000 mPa·s, more preferably at most 10,000 mPa·s, and even more preferably at most 7,000 mPa·s. The viscosity of the curable silicone (a) at 25° C. is measured using a B-type rotational viscometer (for example, model BM, manufactured by Tokyo Keiki Co., Ltd.). As described below, when the polyorganosiloxane (a1) or polyorganosiloxane (a2) is kneaded with the silica particles (b) and then added to the antifouling coating composition, the viscosity of the kneaded mixture is preferably 20 mPa·s or more, more preferably 100 mPa·s or more, even more preferably 500 mPa·s or more, and even more preferably 1,000 mPa·s or more, and is preferably 100,000 mPa·s or less, more preferably 10,000 mPa·s or less, and even more preferably 7,000 mPa·s or less.

[0065] From the viewpoint of improving the strength of the antifouling coating film formed, the content of the curable silicone (a) in the solid content of the antifouling coating composition is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 88% by mass or less. Here, the "solid content of the antifouling coating composition" refers to the components excluding the organic solvent (i) described below and volatile components contained as solvents in each component, and can be regarded as an antifouling coating film. Alternatively, the "solid content of the antifouling coating composition" may be calculated by measuring the solid content (heat residue) obtained by drying the coating composition in a hot air dryer at 125°C for 1 hour. The "content of each component in the antifouling coating film" can be calculated from the content of each component remaining after subtracting the organic solvent (i) described below, volatile components contained as solvents in each component, and components that are eliminated and volatilized after the curing reaction.

[0066] The antifouling coating composition preferably contains other components in addition to the curable silicone (a). Examples of other components include silica particles (b), slipping agents (c), coloring pigments (d), and biological repellents (e), organosilicon crosslinking agents (f), silane coupling agents (g), curing catalysts (h), organic solvents (i), pigments other than silica particles (b) and coloring pigments (d), dehydrating agents other than organosilicon crosslinking agents (f), anti-sagging agents, anti-settling agents, enzymes, flame retardants, and thermal conductivity improvers. It is preferable to contain silica particles (b), slipping agents (c), coloring pigments (d), and biological repellents (e), organosilicon crosslinking agents (f), silane coupling agents (g), curing catalysts (h), and organic solvents (i).

[0067] (Silica particles (b)) From the viewpoint of the hardness, flexibility, and strength of the antifouling coating film to be formed, the antifouling coating composition preferably contains silica particles (b). Examples of the silica particles (b) include hydrophobic silica particles (b1) and hydrophilic silica particles (b2). The silica particles (b) not only improve the physical properties of the antifouling coating film formed, but also improve the fluidity and thixotropy of the antifouling coating composition. The antifouling coating composition preferably contains at least one selected from the group consisting of hydrophobic silica particles (b1) and hydrophilic silica particles (b2), preferably contains at least hydrophobic silica particles (b1), and more preferably contains both hydrophobic silica particles (b1) and hydrophilic silica particles (b2). For preferred embodiments of the silica particles (b) contained in the antifouling coating composition, see paragraphs 0030 to 0037 of WO 2023 / 054487.

[0068] When the antifouling coating composition contains silica particles (b), the content of the silica particles (b) in the solid content of the antifouling coating composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoint of improving the strength and hardness of the antifouling coating film to be formed.

[0069] The content of silica particles (b) per 100 parts by mass of curable silicone (a) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, from the viewpoint of improving the strength and hardness of the antifouling coating film that is formed.

[0070] (Slip agent (c)) The antifouling coating composition preferably contains a slip agent (c) from the viewpoint of the coating workability and antifouling properties of the antifouling coating composition. The slipping agent (c) can impart slipping properties to the antifouling coating film formed, thereby improving the ability to inhibit adhesion of aquatic organisms (antifouling properties). The slipping agent (c) preferably has fluidity at 25°C, and more preferably is liquid. When the slipping agent has fluidity, it is thought that the mobility within the antifouling coating film is high, and the effect of providing slip to the surface can be enhanced. In addition, the viscosity of the antifouling coating composition can be reduced, improving the applicability. The slipping agent (c) is preferably one or more selected from oils and polymers having hydrophilic groups, and the slipping agent (c) preferably includes at least one selected from the group consisting of silicone oil (c1), acrylic polymers having hydrophilic groups (c2), and paraffin oil (c3). For preferred embodiments of the slip agent (c) contained in the antifouling coating composition and its content, see paragraphs 0038 to 0072 of WO 2023 / 054487.

[0071] (Color pigment (d)) It is also preferred that the antifouling coating composition contains a color pigment (d). When the antifouling coating composition contains the color pigment (d), the coating strength can be increased. For preferred embodiments of the color pigment (d) contained in the antifouling coating composition and its content, see paragraphs 0073 to 0074 of WO 2023 / 054487.

[0072] (Biorepellent (e)) The antifouling coating composition may contain a biological repellent (e) for the purpose of enhancing the antifouling properties of the antifouling coating film formed. For preferred embodiments of the biological repellent (e) contained in the antifouling coating composition and its content, see paragraph 0078 of WO 2023 / 054487.

[0073] (Organosilicon Crosslinking Agent (f)) The antifouling coating composition preferably contains an organosilicon crosslinking agent (f) to improve the curing rate, the strength of the antifouling coating film, and the adhesion to the substrate. However, the organosilicon crosslinking agent is not limited to those intended for these functions, and may be added for the purpose of functioning as a wetting agent for the pigment, for example. The organosilicon crosslinking agent (f) is an organosilane having three or four hydrolyzable groups on the silicon atom, and when three hydrolyzable groups are present, one additional hydrocarbon group, and also includes partial condensates thereof, excluding compounds corresponding to the above organosilane (a3). For preferred embodiments of the organosilicon crosslinking agent (f) contained in the antifouling coating composition and its content, see paragraphs 0079 to 0081 of WO 2023 / 054487.

[0074] (Silane coupling agent (g)) The antifouling coating composition preferably contains a silane coupling agent (g) for the purpose of improving the curing rate, the curability of the antifouling coating film, and the adhesion to the substrate. The silane coupling agent (g) is an organic alkoxysilane having at least one alkoxy group and at least one organic reactive group on the silicon atom. The alkoxy group is preferably a methoxy group or an ethoxy group, and more preferably a methoxy group. One to three alkoxy groups are bonded to the silicon atom, preferably two or three, and more preferably three. Examples of the organic reactive group include an amino group, a mercapto group, an epoxy group, an isocyanate group, a ureido group, a vinyl group, an acrylic group, a methacrylic group, and a styryl group. Of these, an amino group, a mercapto group, an epoxy group, an isocyanate group, and a ureido group are preferred, an amino group, a mercapto group, and an epoxy group are more preferred, and an amino group is even more preferred. Specific preferred organic reactive groups containing an amino group include a 2-(aminoethyl)-3-aminopropyl group and a 3-aminopropyl group. In this embodiment, the antifouling coating composition preferably contains an amino group-containing silane coupling agent, and the inclusion of an amino group-containing silane coupling agent is preferred because it reacts with the epoxy group-containing silane coupling agent contained in the coating composition of this embodiment, thereby improving the adhesion between the coating film formed from the coating composition of this embodiment and the antifouling coating film formed from the antifouling coating composition.

[0075] Examples of the silane coupling agent (g) include 3-(2-aminoethylamino)propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-(2-aminoethylamino)ethylamino)propyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-isocyanatepropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. 3-(2-aminoethylamino)propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane are preferred, and 3-(2-aminoethylamino)propyltrimethoxysilane is more preferred. The silane coupling agent (g) may be a condensate of the above-mentioned compound. The silane coupling agent (g) may be used alone or in combination of two or more kinds.

[0076] When the antifouling coating composition contains a silane coupling agent (g), the content of the silane coupling agent (g) in the solid content of the antifouling coating composition is preferably 0.05% by mass or more and 3% by mass or less, and more preferably 0.1% by mass or more and 1% by mass or less. The content of the silane coupling agent (g) in the antifouling coating composition relative to 100 parts by mass of the curable silicone (a) is preferably 0.03 parts by mass or more and 3 parts by mass or less, more preferably 0.1 parts by mass or more and 1 part by mass or less.

[0077] The antifouling coating composition preferably contains an organosilicon crosslinking agent (f) and / or a silane coupling agent (g), more preferably contains at least a silane coupling agent (g), and even more preferably contains at least an amino group-containing silane coupling agent, for the purpose of improving the curability, strength, and adhesion to the substrate of the antifouling coating film.

[0078] (Curing catalyst (h)) The antifouling coating composition preferably contains a curing catalyst (h) in order to improve the curing rate and the film strength of the antifouling coating film. As the curing catalyst (h), tin compounds, titanium compounds, fatty acid salts of alkali metals, and amine compounds are preferred, titanium compounds and amine compounds are more preferred, and titanium compounds are even more preferred. For preferred embodiments of the curing catalyst (h) contained in the antifouling coating composition and its content, see paragraphs 0086 to 0089 of WO 2023 / 054487.

[0079] (Organic solvent (i)) The antifouling coating composition may contain an organic solvent (i) in order to maintain a low viscosity and improve coating workability. Examples of the organic solvent (i) include aromatic hydrocarbon organic solvents, aliphatic hydrocarbon organic solvents, alicyclic hydrocarbon organic solvents, ketone organic solvents, and ester organic solvents, with aromatic hydrocarbon organic solvents and ketone organic solvents being preferred, and aromatic hydrocarbon organic solvents being more preferred. Examples of the aromatic hydrocarbon organic solvent include toluene, xylene, and mesitylene, with xylene being preferred. Examples of the aliphatic hydrocarbon organic solvent include pentane, hexane, heptane, and octane. Examples of the alicyclic hydrocarbon organic solvent include cyclohexane, methylcyclohexane, and ethylcyclohexane. Examples of the ketone organic solvent include acetylacetone, acetone, methyl ethyl ketone, methyl isobutyl ketone, and dimethyl carbonate. Examples of the ester-based organic solvent include ethyl acetate, propyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate. The organic solvent (i) may be used alone or in combination of two or more kinds. When the antifouling coating composition contains an organic solvent (i), the content of the organic solvent (i) in the coating composition is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of improving coating workability, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of suppressing sagging during coating and reducing the environmental load.

[0080] (Other optional ingredients) Examples of pigments other than the silica particles (b) and color pigment (d) include mica, calcium carbonate, barium carbonate, potassium feldspar, kaolin, and short glass fibers. These inorganic fillers may be used alone or in combination of two or more. Examples of the dehydrating agent include zeolite, porous alumina, orthoesters such as alkyl orthoformate esters, orthoboric acid, and isocyanate compounds. Examples of the anti-sagging and anti-settling agents include organic clay waxes (stearate salts of Al, Ca, Zn, lecithin salts, alkylsulfonates, etc.), organic waxes (polyethylene wax, oxidized polyethylene wax, amide wax, polyamide wax, hydrogenated castor oil wax, etc.), and mixtures of organic clay waxes and organic waxes. Examples of the enzyme include serine proteases, cysteine ​​proteases, metalloproteinases, cellulases, hemicellulases, pectinases, and glycosidases. Examples of the flame retardant include antimony oxide and paraffin oxide. The thermal conductivity improver includes boron nitride, aluminum oxide, and the like.

[0081] (Embodiments of antifouling coating composition) The antifouling coating composition may be a one-component antifouling coating composition in which the above components are contained in one composition, or a multi-component antifouling coating composition in which the above components are contained in two or more compositions and mixed before application. From the viewpoint of preventing deterioration during storage, a multi-component antifouling coating composition is preferred, and from the viewpoint of coating workability, a one-component antifouling coating composition is more preferred. Examples of the multi-component antifouling coating composition include a two-component antifouling coating composition and a three- or more-component antifouling coating composition. From the viewpoint of coating workability, a two-component antifouling coating composition is preferred, and from the viewpoint of preventing deterioration during storage, a three- or more-component antifouling coating composition is preferred. When the antifouling coating composition is a multi-component antifouling coating composition, it is preferable that the polyorganosiloxane (a2), the organosilane (a3), the organosilicon crosslinking agent (f), the silane coupling agent (g), and the curing catalyst (h) are contained in different liquids, and it is more preferable that the silane coupling agent (g), the organosilane (a3), the organosilicon crosslinking agent (f), and the curing catalyst (h) are contained in yet another different liquid. The silica particles (b), the color pigment (d) and the biological repellent (e) are preferably contained in the same liquid as the polyorganosiloxane (a1) or the polyorganosiloxane (a2). The content of each component in the antifouling coating composition of the present invention is the content relative to the total amount of all components, even in the case of a multi-component antifouling coating composition.

[0082] (Method of manufacturing antifouling coating composition) The antifouling coating composition is preferably produced as follows. It is preferable to first include a step of kneading the polyorganosiloxane (a1) or polyorganosiloxane (a2) with the silica particles (b). Heating may be performed during or after kneading. By pre-kneading these components, the affinity between the two components is improved, and aggregation of silica and an increase in the viscosity of the coating composition can be suppressed. The heating conditions are preferably 100° C. or higher, more preferably 100° C. to 300° C., and even more preferably 140° C. to 200° C. The pressure is preferably normal pressure or reduced pressure, and the treatment time is preferably 3 hours to 30 hours.

[0083] The antifouling coating composition can be obtained by mixing and stirring the ingredients. When the antifouling coating composition is a one-component antifouling coating composition, it is obtained by appropriately adding the curable silicone (a) and optional components such as silica particles (b), slipping agent (c), color pigment (d), biological repellent (e), organosilicon crosslinking agent (f), silane coupling agent (g), curing catalyst (h) and organic solvent (i), and mixing and stirring them.

[0084] When the antifouling coating composition is a multi-component antifouling coating composition, the polyorganosiloxane (a2), the organosilane (a3), the organosilicon crosslinking agent (f), the silane coupling agent (g), and the curing catalyst (h) are preferably contained in different liquids. When the antifouling coating composition is a three-component or more multi-component antifouling coating composition, the silane coupling agent (g), the organosilicon crosslinking agent (f), and the curing catalyst (h) are preferably contained in further different liquids. Furthermore, the silica particles (b), the color pigment (d), and the biological repellent (e) are preferably contained in the same liquid as the polyorganosiloxane (a1) and / or the polyorganosiloxane (a2). The slipping agent (c) may be contained in either liquid, and it is preferable that the liquid containing the polyorganosiloxane (a1) and / or the polyorganosiloxane (a2) also contains silicone oil (c1), an acrylic polymer (c2) having a hydrophilic group, and paraffin oil (c3). Mixing and stirring is preferably carried out at a temperature of 0°C or higher and 50°C or lower.

[0085] <Anti-fouling coating film> The antifouling coating film is an antifouling coating film formed from the above-mentioned antifouling coating composition. The antifouling coating film can be formed by applying or impregnating at least the coating composition of the present embodiment onto a substrate, drying the resulting coating film, and then applying or impregnating the above-mentioned antifouling coating composition onto the coating film, followed by drying and curing the resulting coating film. The antifouling coating film is preferably an antifouling coating film used for the purpose of preventing substrates from being fouled by aquatic organisms in water.

[0086] The coating composition of this embodiment is preferably used for a primer layer to be formed on a coating film selected from the group consisting of an old antifouling coating film and a one-component or two-component epoxy-based coating film, and it is preferable to apply the antifouling coating composition containing the above-mentioned curable silicone on the primer layer. <Old antifouling coating> The term "old antifouling coating film" refers to an antifouling coating film that has been used and that has become necessary to form a different antifouling coating film from the old antifouling coating film. In other words, the old antifouling coating film is the antifouling coating film that serves as the underlying layer when a new antifouling coating film is formed on top of the old antifouling coating film. The old antifouling coating film is not particularly limited, but it is preferable that the antifouling coating film is a self-polishing antifouling coating film, and an example of such a film is a self-polishing antifouling coating film containing a hydrolyzable polymer having a silyl ester group or a hydrolyzable polymer having a metal ester group, as described in Japanese Patent No. 5033133. <Epoxy primer coating> An example of an epoxy-based coating film is the two-component epoxy resin-based undercoat coating film described in Japanese Patent No. 4271280.

[0087] [Substrate with antifouling coating film and method for producing same] The substrate with an antifouling coating film of this embodiment has, in this order, a substrate, a one-component or two-component epoxy-based undercoat coating film, optionally a previous antifouling coating film, a coating film formed from the paint composition of this embodiment, and an antifouling coating film formed from an antifouling coating composition containing a curable silicone. That is, the substrate with the antifouling coating film of this embodiment preferably comprises, in this order, a substrate, a one-component or two-component epoxy-based undercoat film, a coating formed from the paint composition of this embodiment, and an antifouling coating film formed from an antifouling coating composition containing a curable silicone, or alternatively, a substrate, a one-component or two-component epoxy-based undercoat film, an old antifouling coating film, a coating formed from the paint composition of this embodiment, and an antifouling coating film formed from an antifouling coating composition containing a curable silicone, in this order. In the former case, the substrate has a one-component or two-component epoxy-based undercoat film as the lower layer of the coating formed from the paint composition of this embodiment, and an antifouling coating film formed from an antifouling coating composition containing a curable silicone as the upper layer. In the latter case, the substrate has, in this order, a one-component or two-component epoxy-based undercoat film as the lower layer of the coating formed from the paint composition of this embodiment, and an antifouling coating film formed from an antifouling coating composition containing a curable silicone. paint composition The coating film has an old antifouling coating film as a lower layer formed from the antifouling coating composition containing the curable silicone as a top layer.

[0088] The method for producing a substrate with an antifouling coating film preferably comprises the following steps (1) to (4). Step (1): A step of applying or impregnating a substrate provided with a one-component or two-component epoxy-based primer coating film and, optionally, a previous antifouling coating film, with the coating composition of the present embodiment to obtain a coated or impregnated body. Step (2): A step of drying the coated or impregnated body obtained in step (1) to form a coating film. Step (3): A step of applying or impregnating the coating film with an antifouling coating composition containing a curable silicone to obtain a coated or impregnated body. Step (4): A step of drying and curing the coated or impregnated body obtained in step (3) to form a coating film.

[0089] <Step (1) and Step (3)> Step (1) is a step of applying or impregnating the coating composition of the present embodiment onto a substrate having a one-component or two-component epoxy-based primer coating film and, optionally, an old antifouling coating film, to obtain a coated or impregnated body, and step (3) is a step of applying or impregnating the coating film formed by the coating composition of the present embodiment with an antifouling coating composition containing a curable silicone, to obtain a coated or impregnated body. Steps (1) and (3) are preferably steps for obtaining a coated body by coating. Examples of methods for applying the coating composition of the present invention or the antifouling coating composition containing a curable silicone include known methods such as brush coating, roller coating, spray coating, roll coater coating, flow coater coating, slit coater coating, gravure coater coating, spin coater coating, curtain roll coater coating, electrostatic coating, dip coating, silk printing, and spin coating. The thickness of the coating film formed in steps (1) and (3) is set so that the final coating film has a thickness described below. The coating film may be formed by one coating, or by two or more coatings (two or more coatings). The thickness of the coating film formed from the coating composition of this embodiment is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 50 μm or more, and is preferably 1,000 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less. When the coating film has such a configuration, it is preferable because it has excellent adhesion to the upper and lower layers. The thickness of the antifouling coating film is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 50 μm or more, and is preferably 1,000 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less. When the antifouling coating film has such an embodiment, the antifouling coating film has excellent long-term antifouling properties.

[0090] <Steps (2) and (4)> Step (2) is a step of drying the coated or impregnated body obtained in step (1) to form a coating film, and step (4) is a step of drying and curing the coated or impregnated body obtained in step (3) to form a coating film. The coated or impregnated body according to the above-described method can be dried, or dried and cured, by leaving it, for example, at 23°C for preferably 0.5 to 14 days, more preferably 1 to 10 days, to obtain a coating film. The above-mentioned drying and curing may be carried out under heating and / or while blowing air.

[0091] Here, the substrate is not particularly limited, but is preferably a substrate that comes into contact with seawater or fresh water, more preferably at least one selected from ships, underwater structures, fishing materials, water supply and drainage pipes, and equipment used on or underwater, more preferably ships and underwater structures, and particularly preferably ships. Specific examples include ships (e.g., large steel ships such as container ships and tankers, hull shells of fishing boats, FRP boats, wooden boats, yachts, etc., especially the waterline to bottom portion of the ship, including any of these ships being built or repaired), underwater structures (e.g., oil pipelines, water supply and drainage pipes for factories and thermal and nuclear power plants, undersea cables, seawater utilization equipment (seawater pumps, etc.), megafloats, coastal roads, undersea tunnels, port facilities, various underwater civil engineering structures in canals and waterways, etc.), fishing materials (e.g., ropes, fishing nets, fishing gear, floats or buoys, etc.), seawater supply and drainage pipes for factories and thermal and nuclear power plants, etc., and equipment used underwater or above water (e.g., solar panels, observation windows for instruments and devices, camera lenses, underwater lights, underwater sensors, etc.).

[0092] The material of the substrate is not particularly limited, but examples thereof include steel, aluminum, wood, FRP, glass, plastic, etc., particularly for ships, and glass, plastic, etc., for equipment used on or underwater. The substrate may also be treated with other treatment agents such as a rust inhibitor. [Example]

[0093] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0094] [Synthesis of acrylic resin] <Synthesis of acrylic resin solution (a-1)> A reactor was charged with 17.5 parts by weight of xylene (Xy) as a solvent and 17.5 parts by weight of butyl acetate to obtain a mixed solution. Under a nitrogen stream, the mixed solution was heated to 115°C (reaction temperature), and then 100 parts by weight of a mixed solution of monomer components (styrene: 1.0 part by weight, methyl methacrylate (MMA): 43.0 parts by weight, n-butyl acrylate (BA): 38.0 parts by weight, 2-hydroxyethyl methacrylate (2-HEMA): 11.0 parts by weight, and methacrylic acid (MAA): 7.0 parts by weight) and 0.5 parts by weight of an initiator (t-butylperoxy-2-ethylhexanoate) were added dropwise over 3 hours while maintaining the temperature inside the reactor at 115°C. After the dropwise addition, the mixture was kept at 115°C for 1 hour, and then 0.4 parts by mass of t-butylperoxy-2-ethylhexanoate and 0.4 parts by mass of t-butylperoxybenzoate were added and kept at 115°C for 2 hours to prepare an acrylic resin solution (a-1). The acrylic resin contained in the acrylic resin solution (a-1) is referred to as an acrylic resin (A-1), and the same applies hereinafter.

[0095] <Synthesis of acrylic resin solutions (a-2) to (a-7)> Acrylic resin solutions (a-2) to (a-7) were prepared in the same manner as in the synthesis of acrylic resin solution (a-1), except that the mixed solution of the monomer components used was changed to the composition shown in Table 1. In Table 1, the abbreviations are as follows: St: styrene MMA: Methyl methacrylate BMA: n-butyl methacrylate BA: n-butyl acrylate 2-HEMA: 2-hydroxyethyl methacrylate MAA: methacrylic acid

[0096] The obtained acrylic resin solution was subjected to the following measurements. (Weight average molecular weight (Mw) of acrylic resin) The weight average molecular weight (Mw) of the acrylic resin was measured using GPC under the following conditions. GPC conditions Device: "HLC-8220GPC" (Tosoh Corporation) Column: "TSKgel SuperH2000" and "TSKgel SuperH4000" connected together (both manufactured by Tosoh Corporation, 6 mm (inner diameter) x 15 cm (length)) Eluent: tetrahydrofuran (THF) Flow rate: 0.500mL / min Detector: RI Column thermostat temperature: 40℃ Standard material: polystyrene Sample preparation method: THF was added to the polymer solution, and the mixture was filtered through a membrane filter to obtain a sample for GPC measurement.

[0097] (Solid content measurement) The acrylic resin solution was dried in a hot air dryer at 108°C for 3 hours, and the heating residue (synonymous with "solid content") was measured, and the solid content ratio in the acrylic resin solution was calculated using the following formula. Solid content ratio (mass%) in acrylic resin solution = (mass of the heating residue / mass of resin solution before heating) × 100 (%)

[0098] (Acid value measurement) The acid value of the acrylic resin is measured by the following method. 5 g of acrylic resin solution was accurately weighed into a conical beaker, and 30 to 50 mL of a 7 / 3 (volume ratio) toluene / ethanol mixed solution was added to dissolve the resin solution. Two drops of phenolphthalein-ethanol solution were added as an indicator, and the solution was titrated with N / 10 potassium hydroxide-ethanol solution. The titration endpoint was when the redness of the solution did not disappear after 30 seconds, and the acid value of the acrylic resin solution was calculated using the following formula. Acid value (AV) of acrylic resin solution R)=(B×f×5.61) / S (B: Amount of 0.1 mol / L potassium hydroxide-ethanol solution used (mL), f: Factor of 0.1 mol / L potassium hydroxide-ethanol solution, S: Mass of resin solution (g))

[0099] The acid value in terms of solid content was calculated from the calculated acid value of the acrylic resin solution and the solid content ratio. Acid value (solid content) = AV R ÷(solid content ratio in acrylic resin solution (mass%) / 100)

[0100] (Measurement of hydroxyl value) The hydroxyl value of the acrylic resin is measured by the following method. Five grams of acrylic resin solution was accurately weighed into a flat-bottom flask, and 5 mL of acetylation reagent (25 g of acetic anhydride with pyridine to a total volume of 100 mL) was added. Similarly, 5 mL of acetylation reagent alone was weighed into a flat-bottom flask as a blank measurement. These flat-bottom flasks were heated at 100°C for 1 hour. After cooling, 1 mL of water was added and the mixture was heated at 100°C for 10 minutes. After cooling, 5 mL of ethanol and 30-50 mL of THF were added to dissolve the resin solution. Two drops of phenolphthalein-ethanol solution were added as an indicator, and the mixture was titrated with a N / 2 potassium hydroxide-ethanol solution. The titration endpoint was when the redness of each solution persisted for 30 seconds, and the hydroxyl value of the acrylic resin solution was calculated using the following formula: The hydroxyl value of the acrylic resin solution (A R )=[{(C0-C)×f×28.05} / S]+AV R (C0: titration volume (mL) for blank, C: titration volume (mL) of 0.5 mol / L potassium hydroxide-ethanol solution, f: factor of 0.5 mol / L potassium hydroxide-ethanol solution, S: mass of resin solution (g), AV R (Acid value) The hydroxyl value calculated as solid content was calculated from the calculated hydroxyl value of the acrylic resin solution and the solid content ratio. Hydroxyl value (solid content) = A R÷(solid content ratio in acrylic resin solution (mass%) / 100)

[0101] [Table 1]

[0102] [Production of coating composition] <Ingredients of the coating composition> The components used in the coating composition are shown in Table 2.

[0103] [Table 2]

[0104] Each component was blended according to the blending amounts (parts by mass) shown in Table 3, and mixed and stirred to obtain coating compositions (Examples 1 to 8 and Comparative Examples 1 to 11).

[0105] [evaluation] The resulting coating compositions were evaluated as follows. <Viscosity> The viscosity (unit: KU) at a liquid temperature of 25°C was measured using a Stormer viscometer (KU-2, manufactured by Brookfield).

[0106] <Adhesion test 1: Adhesion to primer epoxy coating> An epoxy resin-based anticorrosion paint (trade name "Banno 500" manufactured by Chugoku Toryo Co., Ltd.) was spray-painted onto a sandblasted steel plate (300 mm long x 100 mm wide x 2.3 mm thick) to a dry film thickness of 150 μm, and then dried at room temperature (23°C) for 24 hours. Next, an epoxy resin-based binder (trade name "CMP Bioclean SG-R" manufactured by Chugoku Toryo Co., Ltd.) was spray-painted onto the plate to a dry film thickness of 100 μm, and then dried at room temperature for 24 hours. Next, the paint compositions of each of the above examples and comparative examples were thoroughly mixed onto this primer coating, and then applied using a spray paint machine so that the dry film thickness was 50 μm.After leaving it at room temperature for one week, a test panel with a coating was prepared. The prepared test panels with coating were used and evaluated according to the cross-cut method (cross-cut interval: 2 mm) of JIS K 5600-5-6:1999 on a 6-point scale from 0 to 5 as specified in the JIS. A smaller number indicates better adhesion. The results are shown in Table 3.

[0107] <Adhesion test 2: Adhesion to primer self-polishing antifouling paint (old antifouling paint film)> Sandblasted steel plates (300 mm long x 100 mm wide x 2.3 mm thick) were spray-painted with an epoxy resin-based anticorrosion paint (product name "Banno 500" manufactured by Chugoku Toryo Co., Ltd.) to a dry film thickness of 150 μm and allowed to dry at room temperature (hereinafter, 23 °C) for 24 hours. Next, an epoxy resin-based anticorrosion paint (product name "Banno 500N" manufactured by Chugoku Toryo Co., Ltd.) was spray-painted with a dry film thickness of 100 μm and allowed to dry at room temperature for 24 hours. A zinc acrylic polymer-based hydrolysis-type antifouling paint (self-polishing antifouling paint) (product name "Sea Grand Prix 500HS" manufactured by Chugoku Toryo Co., Ltd.) was spray-painted with a dry film thickness of 100 μm and allowed to dry at room temperature for 7 days to prepare test plates. The resulting test plates were immersed in Miyajima Bay, Hiroshima Prefecture for 6 months to obtain the old antifouling coating film. Next, the coating compositions of each of the above examples and comparative examples were thoroughly mixed onto the coating film (old antifouling coating film) formed by this self-polishing antifouling paint, and then painted using a spray paint machine so that the dry film thickness was 50 μm.After leaving it at room temperature for one week, a test panel with a coating film was prepared. Using the obtained test plates, adhesion was evaluated by the cross-cut method in the same manner as in <Adhesion Test 1: Adhesion to Primer Epoxy Coating Film>.

[0108] <Adhesion tests 3 and 4: Adhesion to topcoat silicone-based antifouling coating> An epoxy resin-based anticorrosive paint (trade name "Banno 500", manufactured by Chugoku Paint Co., Ltd.) was applied to a sandblasted steel plate (300 mm long x 100 mm wide x 2.3 mm thick) using a spray painter to a dry film thickness of 150 μm and dried at room temperature (hereinafter, 23 ° C) for 24 hours. Next, an epoxy resin-based anticorrosive paint (trade name "CMP Bioclean SG-R", manufactured by Chugoku Paint Co., Ltd.) was applied to a dry film thickness of 100 μm using a spray painter and dried at room temperature for 24 hours. Next, the coating compositions of each of the examples and comparative examples were thoroughly mixed, and then applied to a dry film thickness of 50 μm using a spray painter and dried at room temperature for 24 hours. Next, in adhesion test 3, a silicone resin-based antifouling paint A was applied to a dry film thickness of 150 μm using a spray painter and dried at room temperature for 7 days to prepare a coated test plate. In adhesion test 4, a test plate with a coating film was prepared in the same manner except that silicone resin-based antifouling paint B was used instead of silicone resin-based antifouling paint A. The silicone resin-based antifouling paint A used in adhesion test 3 is the antifouling paint composition described in Example 6 of WO 2023 / 054487, and the silicone resin-based antifouling paint B used in adhesion test 4 is the antifouling paint composition described in Example 1 of WO 2023 / 054487. The obtained test panels were immersed in Miyajima Bay, Hiroshima Prefecture for 3 months, and then the adhesion of the topcoat silicone-based antifouling coating film was evaluated by the following method. A single cut was made in the silicone-based antifouling coating film on the coating surface of the test plate using a single blade specified in JIS K5600-5-6, and the film was rubbed perpendicular to the cut with a paper cloth. The degree of delamination between the film and the coating film formed from the coating composition of the example and comparative example was evaluated according to the following criteria. The results are shown in Table 3 below. 0: No damage to the coating other than cuts is observed. 1: There is slight paint damage around the cut, but no other damage. 2: There is delamination of the coating around the cut, but the delamination does not spread any further. 3: Delamination occurs within 10 mm of the cut. 4: Delamination occurs within 10 mm or more from the cut. 5: No coating is present.

[0109] [Table 3]

[0110] The examples and comparative examples show that the coating composition of the present invention can provide a coating film that has excellent adhesion to the underlying old antifouling coating film and epoxy-based primer coating film, and also has excellent adhesion to the upper layer antifouling coating film obtained from the antifouling coating composition containing curable silicone.

Claims

1. A coating composition comprising an acrylic resin (A) having an acid value and an epoxy group-containing silane coupling agent (B), the acrylic resin (A) has an acid value of 10 mgKOH / g or more and 35 mgKOH / g or less and a hydroxyl value of 10 mgKOH / g or more and 200 mgKOH / g or less; The content of the acrylic resin (A) in the solid content of the coating composition is 25% by mass or more and 50% by mass or less, The content of the epoxy group-containing silane coupling agent (B) in the solid content of the coating composition is 6% by mass or more and 25% by mass or less. A coating composition for use as an undercoat layer of an antifouling coating composition containing a curable silicone.

2. 2. The coating composition according to claim 1, wherein the acid value of the solvent-soluble portion of the coating composition is 2 mgKOH / g or more and 10 mgKOH / g or less.

3. 2. The coating composition according to claim 1, wherein the ratio of the active hydrogen equivalents (eq) of the epoxy curing agent to the epoxy group equivalents (eq) in the solid content of the coating composition (active hydrogen equivalents / epoxy group equivalents) is 0.05 or less.

4. 2. The coating composition according to claim 1, wherein the curable silicone is at least one curable silicone selected from the following (1) and (2): (1) Polyorganosiloxane having ketoxime groups at both ends (2) A polyorganosiloxane having hydroxy groups at both ends, and an organosilane represented by the following formula (I): 【Chemistry 1】 (In formula (I), R １ represents a substituted or unsubstituted hydrocarbon group having from 1 to 10 carbon atoms, X is a ketoxime group, and a is 0 or 1.

5. 5. The coating composition according to claim 4, wherein the curable silicone is the curable silicone of (1).

6. The coating composition according to claim 1, wherein the antifouling coating composition contains an amino group-containing silane coupling agent.

7. 2. The coating composition according to claim 1, which is for use in an undercoat layer formed on a coating film selected from the group consisting of an old antifouling coating film and a one-component or two-component epoxy-based undercoat coating film.

8. A coating film formed from the coating composition according to any one of claims 1 to 7.

9. A substrate with an antifouling coating film, comprising, in this order: a substrate; the coating film according to claim 8; and an antifouling coating film formed from an antifouling coating composition containing a curable silicone.

10. A substrate with an antifouling coating film, comprising, in this order: a substrate; a one-component or two-component epoxy-based primer coating film; optionally an old antifouling coating film; the coating film according to claim 8; and an antifouling coating film formed from an antifouling coating composition containing a curable silicone.

11. A method for producing a substrate with an antifouling coating film, comprising the following steps (1) to (4): Step (1): A step of applying or impregnating a substrate with the coating composition according to any one of claims 1 to 7 to obtain a coated or impregnated body. Step (2): A step of drying the coated or impregnated body obtained in step (1) to form a coating film. Step (3): A step of applying or impregnating the coating film with an antifouling coating composition containing a curable silicone to obtain a coated or impregnated body. Step (4): A step of drying and curing the coated or impregnated body obtained in step (3) to form a coating film.

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