JP7538551B2 - Coating composition - Google Patents

Description

This disclosure relates to a coating composition.

Industrial and construction machinery are generally large and can withstand heavy loads, so they are characterized by having thicker constituent substrates (steel plates) than automobile bodies, etc. Therefore, when such industrial and construction machinery are used as substrates, there is a problem that the substrate has a large heat capacity and heat is not sufficiently transferred to the substrate in the heating furnace. For this reason, when painting such substrates, a room temperature film-forming paint composition is selected, which does not require a high-temperature heating process and can form a coating film at room temperature.

Industrial and construction machinery are often used in physically harsh environments, so the coatings that protect their surfaces generally require excellent weather resistance as well as excellent corrosion resistance.

A method for forming a coating film that satisfies both the anticorrosive and weather resistance performances is to use a coating composition with excellent anticorrosive properties as an undercoat coating composition, and then use a topcoat coating composition with excellent weather resistance to form a multi-layer coating film. For example, Patent Document 1 describes a method for forming a thick-film anticorrosive coating film, which is characterized by undercoating a weak-solvent high-solid modified epoxy resin paint containing a binder resin component consisting of a modified epoxy resin having an epoxy equivalent of 400 to 2,000 g/eq based on the total mass of the binder resin component, an amine resin, and a reactive diluent, and then overcoating a weak-solvent high-solid polyurethane resin paint containing a binder resin component consisting of a polyol resin having a hydroxyl value of 10 to 100 mgKOH/g and a polyisocyanate compound.

Patent Document 2 also describes that, for the purpose of improving corrosion resistance, etc., a coating composition containing a hydroxyl-containing resin, barium sulfate, talc, organic resin particles, a color pigment, and a polyisocyanate compound uses 1 to 130 parts by mass of barium sulfate, 1 to 50 parts by mass of talc, 0.1 to 20 parts by mass of organic resin particles, 1 to 100 parts by mass of color pigment, and 10 to 60 parts by mass of polyisocyanate compound, based on 100 parts by mass of the total solid content of the hydroxyl-containing resin.

Patent Document 3 describes that, for the purpose of improving corrosion resistance, etc., in an aqueous coating composition containing acrylic resin particles and a rust inhibitor, the acid value of the acrylic resin particles is set to 10 to 100 mgKOH/g, and 80 mass % or more of the total copolymerization components of the acrylic resin particles is a polymerizable monomer having a solubility parameter value of 9.5 or less, and that the rust inhibitor is an aminosilane, an azole compound, and at least one compound selected from the group consisting of a fatty acid, an aromatic acid, and an aliphatic amine.

JP 2010-188239 A JP 2017-52931 A International Publication No. 2020/026743

According to the method described in Patent Document 1, it is stated that a single undercoat and topcoat coating can provide the same corrosion prevention effect as that achieved by conventional multi-layer coating of each layer. However, this method requires that the undercoat is dried at room temperature for 24 hours after application of the undercoat and then the topcoat is applied, and since the process of forming the multi-layer coating takes a long time, there is a problem that the efficiency of the coating process (also called coating workability) is poor. From the viewpoints of shortening the process of the coating line when forming the coating, reducing carbon dioxide emissions, and saving energy, there is a demand for a coating that can achieve both corrosion resistance and weather resistance with a single coating.

In addition, the weather resistance of the coating films obtained with the coating compositions of Patent Documents 2 and 3 was not fully satisfactory.

This disclosure was made in consideration of the above circumstances, and aims to provide a coating composition that can form a coating film that is both corrosion-resistant and weather-resistant with a single coat.

The present disclosure includes the following.
[1] A coating composition comprising a base composition (I) and a curing agent composition (II),
The base composition (I) contains a coating film-forming resin (A),
The coating film-forming resin (A) has a hydroxyl group,
The curing agent composition (II) contains a polyisocyanate compound (B),
At least one of the base composition (I) and the curing agent composition (II) contains at least one of a silane coupling agent (D) and/or a hydrolysate or condensate of a silane coupling agent,
The silane coupling agent (D) includes an amino group-containing silane coupling agent (D1) and an epoxy group-containing silane coupling agent (D2),
At least one of the base composition (I) and the curing agent composition (II) contains a benzotriazole compound (E).
[2] The coating composition according to [1], wherein the content of the silane coupling agent (D) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the total resin solid content of the coating composition.
[3] The ratio of the content of the amino group-containing silane coupling agent (D1) to the content of the epoxy group-containing silane coupling agent (D2) [(D2)/(D1)] is 0.3 or more and 20 or less. [1] or [2] The coating composition according to the present invention.
[4] The coating composition according to any one of [1] to [3], wherein the content of the benzotriazole compound (E) is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total resin solid content of the coating composition.
[5] The coating composition according to any one of [1] to [4], wherein the hydroxyl value of the coating film-forming resin (A) is 30 mg KOH/g or more and 300 mg KOH/g or less.
[6] The coating composition according to any one of [1] to [5], wherein the film-forming resin (A) comprises an acrylic resin (A1) and/or a polyester resin (A2).
[7] The coating composition according to any one of [1] to [6], wherein the polyisocyanate compound (B) comprises at least one selected from an aliphatic polyisocyanate compound; an aromatic polyisocyanate compound; an alicyclic polyisocyanate compound; a multimer of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound; and a modified product of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound.
[8] The coating composition according to any one of [1] to [7], wherein the molar ratio (NCO/OH) of the isocyanate groups contained in the polyisocyanate compound (B) to the hydroxyl groups contained in the coating film-forming resin (A) is 0.4 or more and 1.6 or less.
[9] At least one of the base composition (I) and the curing agent composition (II) contains an amine compound (F),
The coating composition according to any one of [1] to [8], wherein the amine compound (F) has an aliphatic hydrocarbon group having 6 or more carbon atoms.
[10] The coating composition according to [9], wherein the content of the amine compound (F) is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of a total of resin solid contents of the coating composition.

The coating composition disclosed herein can form a coating film that is both corrosion resistant and weather resistant with a single coat.

The coating composition of the present disclosure is a coating composition comprising a base composition (I) and a curing agent composition (II),
The base composition (I) contains a coating film-forming resin (A),
The coating film-forming resin (A) has a hydroxyl group,
The curing agent composition (II) contains a polyisocyanate compound (B),
At least one of the base composition (I) and the curing agent composition (II) contains at least one of a silane coupling agent (D) and/or a hydrolysate or condensate of a silane coupling agent,
The silane coupling agent (D) includes an amino group-containing silane coupling agent (D1) and an epoxy group-containing silane coupling agent (D2),
At least one of the base composition (I) and the hardener composition (II) contains a benzotriazole compound (E).

According to this disclosure, it is possible to form a coating film that is both corrosion resistant and weather resistant with a single coat of paint.

Although the present disclosure should not be interpreted as being limited to a particular theory, the reason why the coating composition of the present disclosure exhibits the above-mentioned effect is believed to be as follows. That is, the coating composition of the present disclosure contains a coating film-forming resin having a hydroxyl group and a polyisocyanate compound as its curing agent, and further contains an amino group-containing silane coupling agent, an epoxy group-containing silane coupling agent, and a benzotriazole compound as silane coupling agents. Therefore, when the coating composition of the present disclosure is applied to a substrate, the benzotriazole compound can interact with the substrate surface through π-π interaction, and at the same time, the amino group-containing silane coupling agent and the epoxy group-containing silane coupling agent are thought to interact with the substrate surface or be incorporated into the resin. As a result, in the resulting coating film, the benzotriazole compound is fixed in a state of covering the substrate surface, and further, the silane coupling agent is thought to increase the adhesion between the coating film and the substrate surface, as well as increase the water resistance, weather resistance, and heat resistance of the coating film itself. As a result, it is believed that the use of the coating composition of the present disclosure makes it possible to form a coating film that is both corrosion-resistant and weather-resistant.

In this disclosure, the film formed after the coating composition is applied and before it is dried or cured is also referred to as the coating film, and the film formed after it is dried or cured is also referred to as the coating film.

(Paint composition)
The coating composition includes a base composition (I) and a curing agent composition (II), and may be a two-liquid curing type coating composition. The base composition (I) and the curing agent composition (II) are stored separately, mixed just before painting, and then the mixture is applied to the coating. The base composition (I) includes a coating film-forming resin (A), and the curing agent composition (II) includes a polyisocyanate compound (B). At least one of the base composition (I) and the curing agent composition (II) includes a silane coupling agent (D) and/or a hydrolyzate or condensate of a silane coupling agent, and at least one of the base composition (I) and the curing agent composition (II) includes a benzotriazole compound (E). At least one of the base composition (I) and the curing agent composition (II) may each include one or more selected from a color pigment, an extender pigment, and an anti-rust pigment.

(A) Film-forming resin The base composition (I) contains a film-forming resin (A). The film-forming resin (A) has a hydroxyl group. The film-forming resin (A) preferably contains an acrylic resin (A1) and/or a polyester resin (A2), and more preferably contains an acrylic resin (A1).

(A1) Acrylic Resin The acrylic resin (A1) is a polymer of a monomer mixture containing an ethylenic monomer and has a hydroxyl group. By including the acrylic resin (A1) in the base composition (I), the obtained coating film can be given adhesion to the substrate, and the corrosion resistance and weather resistance of the coating film can be improved.

The ethylenic monomers include hydroxyl group-containing monomers and other monomers.

Examples of hydroxyl group-containing monomers include the (meth)acrylic acid hydroxyalkyl ester, the (meth)acrylic acid polyalkylene glycol monoester, and the ε-caprolactone-modified (meth)acrylate.

Examples of other monomers used in the acrylic resin (A1) include the carboxyl group-containing monomers; the (meth)acrylic acid alkyl esters; alicyclic (meth)acrylic monomers such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and adamantyl (meth)acrylate; amino group-containing (meth)acrylic acid esters such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and butylaminoethyl (meth)acrylate; amide group-containing monomers such as (meth)acrylamide, N-methylol (meth)acrylamide, methoxybutyl (meth)acrylamide, and diacetone (meth)acrylamide; amino group-containing (meth)acrylamides such as aminoethyl (meth)acrylamide, dimethylaminomethyl (meth)acrylamide, and methylaminopropyl (meth)acrylamide; cyanide vinyl monomers such as (meth)acrylonitrile and α-chloroacrylonitrile; saturated aliphatic carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; and the styrene monomers.
The ethylenic monomers may be used alone or in combination of two or more kinds.

Other monomers used in the acrylic resin (A1) are preferably the (meth)acrylic acid alkyl esters and the alicyclic (meth)acrylic monomers, and more preferably acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, etc.

The hydroxyl value of the acrylic resin (A1) is preferably 30 mgKOH/g or more and 300 mgKOH/g or less, more preferably 50 mgKOH/g or more and 200 mgKOH/g or less. When the hydroxyl value of the acrylic resin (A1) is within the above range, the corrosion resistance and weather resistance of the resulting coating film can be improved.

The acid value of the acrylic resin (A1) is preferably 0 mgKOH/g or more and 20 mgKOH/g or less, more preferably 0 mgKOH/g or more and 15 mgKOH/g or less.

In this disclosure, the acid value and hydroxyl value are both expressed as solid content equivalents and can be measured by a method conforming to JIS K 0070.

The number average molecular weight of the acrylic resin (A1) is preferably 3,000 to 20,000, more preferably 3,000 to 15,000, and even more preferably 3,500 to 12,000. When the number average molecular weight of the acrylic resin (A1) is within the above range, the appearance, corrosion resistance, and weather resistance of the resulting coating film can be improved.
In the present disclosure, the number average molecular weight is a value calculated in terms of polystyrene by gel permeation chromatography (GPC).

The acrylic resin (A1) can be produced by polymerizing the monomer mixture without a solvent or in the presence of a suitable organic solvent. Examples of the polymerization method include a radical polymerization method, which can be carried out using a radical polymerization initiator. Specifically, the polymerization may be a bulk polymerization method, a solution polymerization method, or a bulk-suspension two-stage polymerization method in which suspension polymerization is carried out after bulk polymerization. Among these, the solution polymerization method is particularly preferred, and an example of the method that can be used is heating the monomer mixture in the presence of a radical polymerization initiator at a temperature of, for example, 80 to 200°C while stirring.

As the acrylic resin (A1), commercially available products may be used. There is no particular limitation on commercially available products, and examples of such products include the Acrydic series, such as Acrydic A-428 (manufactured by DIC Corporation), the Dianale series, such as Dianale LC-2657 (manufactured by Mitsubishi Chemical Corporation), and the Hitaleoid series (manufactured by Showa Denko Materials Co., Ltd.).

The solid content of the acrylic resin (A1) may be preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less, based on 100 parts by mass of the total solid content of the coating-forming resin (A).

In this disclosure, the solid content of a certain component refers to the heating residue when the component is heated at 105°C for 1 hour.

(A2) Polyester Resin The polyester resin (A2) may be a condensate of a polyol and a polybasic acid and/or a modified product of the condensate, and has a hydroxyl group.

Examples of the polyol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol or 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (BASHPN), N,N-bis-(2-hydroxyethyl)dimethylhydantoin, polycaprolactone polyol, glycerin, sorbitol, ammonium nitrile, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol, and tris-(hydroxyethyl)isocyanate. Only one type of polyol may be used, or two or more types may be used in combination.

Examples of the polybasic acid include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyl tetraphthalic acid, methyl tetrahydrophthalic anhydride, himic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, and endo acid anhydride. Only one basic acid may be used, or two or more basic acids may be used in combination.

Examples of the modified materials include modified polyester resins such as urethane modified polyester resin, epoxy modified polyester resin, acrylic modified polyester resin, and silicone modified polyester resin.

The hydroxyl value of the polyester resin (A2) is preferably 50 mgKOH/g or more and 200 mgKOH/g or less, more preferably 60 mgKOH/g or more and 180 mgKOH/g or less, and even more preferably 70 mgKOH/g or more and 150 mgKOH/g or less. When the hydroxyl value of the polyester resin (A2) is within the above range, the corrosion resistance and weather resistance of the resulting coating film can be improved.

The acid value of the polyester resin (A2) is preferably 0 mgKOH/g or more and 50 mgKOH/g or less, more preferably 0 mgKOH/g or more and 30 mgKOH/g or less, and even more preferably 0 mgKOH/g or more and 25 mgKOH/g or less.

The number average molecular weight of the polyester resin (A2) is preferably 1,000 or more and 5,000 or less, more preferably 1,200 or more and 4,000 or less, and even more preferably 1,500 or more and 3,500 or less. When the number average molecular weight of the polyester resin (A2) is within the above range, the appearance, corrosion resistance, and weather resistance of the resulting coating film can be improved.

The solid content of the polyester resin (A2) may be preferably 0% by mass or more and 50% by mass or less, more preferably 0% by mass or more and 30% by mass or less, and even more preferably 0% by mass or more and 10% by mass or less, based on 100 parts by mass of the total solid content of the coating film-forming resin (A).

The coating film-forming resin (A) may contain, in addition to the acrylic resin (A1) and/or polyester resin (A2), other resins such as epoxy resins and urethane resins, as necessary.

The hydroxyl value of the film-forming resin (A) is preferably 30 mgKOH/g or more and 300 mgKOH/g or less, more preferably 50 mgKOH/g or more and 200 mgKOH/g or less. When the hydroxyl value of the film-forming resin (A) is within the above range, the resulting coating film can have good corrosion resistance and weather resistance.

The acid value of the film-forming resin (A) is preferably 0 mgKOH/g or more and 50 mgKOH/g or less, more preferably 0 mgKOH/g or more and 30 mgKOH/g or less, and even more preferably 0 mgKOH/g or more and 20 mgKOH/g or less.

The number average molecular weight of the film-forming resin (A) is preferably 1,000 or more and 15,000 or less, more preferably 1,200 or more and 12,000 or less. When the number average molecular weight of the film-forming resin (A) is within the above range, the corrosion resistance and weather resistance of the resulting coating film can be improved.

The solid content of the film-forming resin (A) may be, based on 100 parts by mass of the solid content of the coating composition, preferably 20 parts by mass or more and 70 parts by mass or less, more preferably 25 parts by mass or more and 60 parts by mass or less, and even more preferably 30 parts by mass or more and 53 parts by mass or less.

Polyisocyanate Compound (B)
The polyisocyanate compound (B) represents a compound having two or more isocyanate groups in one molecule.

The polyisocyanate compound (B) preferably includes at least one selected from an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, an alicyclic polyisocyanate compound, an aromatic polyisocyanate compound, an aromatic polyisocyanate compound, a multimer of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound, and a modified product of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound. The aliphatic polyisocyanate compound, the aromatic polyisocyanate compound, and the alicyclic polyisocyanate compound may be a monomer or a multimer. The polyisocyanate compound (B) may be a so-called asymmetric type. The number of carbon atoms of the polyisocyanate compound (B) is preferably 5 to 24, more preferably 6 to 18.

Examples of the aliphatic polyisocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, undecane diisocyanate-(1,11), lysine ester diisocyanate, diethylene glycol diisocyanate, dipropylene glycol diisocyanate, triethylene glycol diisocyanate, and thiodipropyl diisocyanate.

Examples of the aromatic polyisocyanate include 1,5-dimethyl-2,4-bis(isocyanatomethyl)benzene, 1,5-trimethyl-2,4-bis(ω-isocyanatoethyl)-benzene, 1,3,5-trimethyl-2,4-bis(isocyanatomethyl)benzene, 1,3,5-triethyl-2,4-bis(isocyanatomethyl)benzene, 2,4- and/or 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,4-diisocyanatoisopropylbenzene, and the like.

Examples of the alicyclic polyisocyanate compound include cyclohexane diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate, etc.

The polymers include allophanate bodies, uretdione bodies, biuret bodies, isocyanurate bodies, trimethylolpropane (TMP) adduct bodies, etc., of the aliphatic polyisocyanate compounds, the aromatic polyisocyanate compounds, and the alicyclic polyisocyanate compounds.

Examples of the modified product include carbodiimide compounds and uretonimine compounds obtained by self-polymerization of the aliphatic polyisocyanate compounds, the aromatic polyisocyanate compounds, and the alicyclic polyisocyanate compounds; and compounds in which a urethane group, a urea group, and an oxazolidone group are formed by modifying the aliphatic polyisocyanate, the aromatic polyisocyanate, and the alicyclic polyisocyanate with one or more compounds selected from a compound having a hydroxyl group, an amine compound, and an epoxy compound.
The polyisocyanate compound (B) may be used alone or in combination of two or more kinds.

The polyisocyanate compound (B) preferably contains one or more polymers selected from the aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate, more preferably contains at least one isocyanurate selected from the aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate, and further preferably contains an isocyanurate of the aliphatic polyisocyanate. When the polyisocyanate compound (B) contains one or more isocyanurates selected from the aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate, the content of the isocyanurate in the polyisocyanate compound (B) is preferably 60% by mass or more and 100% by mass or less.

In the coating composition, the molar ratio (NCO/OH) of the isocyanate groups of the polyisocyanate compound (B) to the hydroxyl groups of the coating film-forming resin (A) is preferably 0.4 to 1.6, more preferably 0.8 to 1.3. When the molar ratio (NCO/OH) is within this range, the coating composition is sufficiently cured, and the resulting coating film can have better corrosion resistance and weather resistance.

(C) Solvent The coating composition preferably contains a solvent (C) as a dispersion medium. Specifically, at least one of the base composition (I) and the hardener composition (II) preferably contains an organic solvent as a dispersion medium, and the base composition (I) and the hardener composition (II) preferably contain an organic solvent as a dispersion medium. The organic solvent (C) may include those commonly used in solvent-based paints, for example, aromatic hydrocarbon solvents such as toluene, xylene, and mesitylene; ketone solvents such as methyl ethyl ketone and cyclohexanone; ether solvents such as dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether, 2-methoxypropanol (propylene glycol monomethyl ether), diethylene glycol monobutyl ether, butyl diglycol, and 2-butoxypropanol; ether acetate solvents such as methoxybutyl acetate, methyl ether acetate, ethylene glycol monoethyl ether acetate (cellosolve acetate), ethylene glycol monobutyl ether acetate (butyl cellosolve acetate), and propylene glycol monomethyl ether acetate; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and isobutyl acetate; petroleum ether; and petroleum naphtha.

As the solvent (C), a commercially available product may be used. For example, Solvesso 100 (manufactured by Exxon Chemical Co.) may be mentioned.

(D) Silane Coupling Agent In the production method of the present disclosure, at least one of the main agent (I) and the curing agent (II) in the coating composition contains at least one of a silane coupling agent (D) and/or a hydrolyzate or condensate of the silane coupling agent (D). The condensate may be, for example, a dimer to tetramer of the silane coupling agent (D).

In the present disclosure, the silane coupling agent (D) refers to a compound having a hydrolyzable silyl group and an organic group bonded to the silicon atom of the hydrolyzable silyl group. The silane coupling agent (D) includes an amino group-containing silane coupling agent (D1) and an epoxy group-containing silane coupling agent (D2).

The amino group-containing silane coupling agent (D1) represents a silane coupling agent having an amino group. The amino group may be a primary and/or secondary amino group.

The amino group-containing silane coupling agent (D1) is preferably represented by the following formula (1):
X ¹ -SiR ¹ _n (OR ¹ ) _3-n (1)
[In formula (1),
R ¹ independently at each occurrence represents a C _1-4 alkyl group;
^X1 represents an organic group containing an amino group;
n represents an integer of 0 to 2.
The compound includes a compound represented by the formula:

The organic group containing an amino group may preferably be an organic group containing a primary and/or secondary amino group. The organic group containing an amino group is preferably an organic group represented by the following formula:
-R ¹² -NR ¹¹ -R ¹² -NR ¹¹ ₂
-R ¹² -NR ¹¹ ₂
[Wherein,
R ¹¹ independently represents an optionally substituted C _1-6 alkyl group, an optionally substituted C _6-10 aromatic hydrocarbon group, or a hydrogen atom in each occurrence;
R ¹² , at each occurrence, independently represents a C _1-10 alkylene group, preferably a C _1-6 alkylene group, and more preferably a C _1-4 alkylene group.
Examples of the group include a group represented by the following formula:

Examples of the substituent that the C _1-10 alkylene group represented by R ¹² and the C _6-10 aromatic hydrocarbon group represented by R ¹² may have include a vinyl group and a C _6-10 aromatic hydrocarbon group. Examples of the C _6-10 aromatic hydrocarbon group represented by R ¹¹ and the C _6-10 aromatic hydrocarbon group which is the substituent include a phenyl group, a tolyl group, a xylyl group, a vinylphenyl group and a naphthyl group.

Examples of the amino group-containing silane coupling agent (D1) include N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-8-aminooctyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine.

The amino group-containing silane coupling agent (D1) and its hydrolysate or condensate may be a commercially available product, such as KBM-602, KBM-603, KBE-603, KBM-903, KBM-6803, KBM-573, or KBP-90 (all manufactured by Shin-Etsu Chemical Co., Ltd.).
The amino group-containing silane coupling agent (D1) may be used alone or in combination of two or more kinds.

The content of the amino group-containing silane coupling agent (D1) may be preferably 0.1 parts by mass or more and 15 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, even more preferably 0.3 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 2 parts by mass or less, relative to 100 parts by mass of the total resin solids of the coating composition. When the content of the amino group-containing silane coupling agent (D1) is within the above range, the storage stability of the resulting coating composition can be improved, and the corrosion resistance and weather resistance of the resulting coating film can be improved.

In this disclosure, the content of the amino group-containing silane coupling agent (D) represents the total amount of the silane coupling agent (D) itself contained in the coating composition and the amount of the hydrolyzate or condensate of the silane coupling agent (D) converted into the amount of unreacted silane coupling agent (D), and may be, for example, the amount of the silane coupling agent (D) used in preparing the coating composition. The same applies to the contents of the amino group-containing silane coupling agent (D1) and the epoxy group-containing silane coupling agent (D2).

In addition, in this disclosure, the resin solid content of the coating composition means the total amount of solid content of the resin components that may be contained in the base composition (I) and the hardener composition (II), and more specifically, means the total amount of solid content of the coating film-forming resin (A) and the polyisocyanate compound (B).

The epoxy group-containing silane coupling agent (D2) represents a silane coupling agent having an epoxy group.

The epoxy group-containing silane coupling agent (D2) is preferably represented by the following formula (2):
X ² -R ² -SiR ¹ _n (OR ¹ ) _3-n (2)
[In formula (2),
R ¹ independently at each occurrence represents a C _1-4 alkyl group;
^R2 represents a _C1-6 alkylene group;
^X2 represents one selected from an epoxy group, an epoxycycloalkyl group, and a glycidoxy group;
n represents an integer of 0 to 2.
The compound includes a compound represented by the formula:

Examples of epoxy group-containing silane coupling agents (D2) include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethylethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 5,6-epoxyhexyltriethoxysilane, etc.

The epoxy group-containing silane coupling agent (D2) and its hydrolysate or condensate may be a commercially available product, such as KBM-403, KBE-403, KBE-402, or KBM-303 (all manufactured by Shin-Etsu Chemical Co., Ltd.).
The epoxy group-containing silane coupling agent (D2) may be used alone or in combination of two or more kinds.

The content of the epoxy group-containing silane coupling agent (D2) may be preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.1 parts by mass or more and 20 parts by mass or less, even more preferably 0.3 parts by mass or more and 15 parts by mass or less, and even more preferably 0.3 parts by mass or more and 12 parts by mass or less, relative to 100 parts by mass of the total resin solids. When the content of the epoxy group-containing silane coupling agent (D2) is within the above range, the storage stability of the paint can be good, and the corrosion resistance and weather resistance of the resulting coating film can be good.

The ratio of the content of the amino group-containing silane coupling agent (D1) to the content of the epoxy group-containing silane coupling agent (D2) [(D2)/(D1)] is preferably 0.3 to 30, more preferably 0.3 to 20, even more preferably 1 to 17, and even more preferably 3 to 17. By being in the above range, the corrosion resistance and weather resistance of the resulting coating film can be improved.

The total content of the amino group-containing silane coupling agent (D1) and the epoxy group-containing silane coupling agent (D2) is preferably 50 parts by mass or more and 100 parts by mass or less, more preferably 70 parts by mass or more and 100 parts by mass or less, and even more preferably 80 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the silane coupling agent (D).

The content of the silane coupling agent (D) may be preferably 0.1 parts by mass or more and 40 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, even more preferably 0.7 parts by mass or more and 20 parts by mass or less, and even more preferably 1 part by mass or more and 15 parts by mass or less, based on 100 parts by mass of the total resin solid content of the coating composition.

The silane coupling agent (D) may contain other silane coupling agents in addition to the amino group-containing silane coupling agent (D1) and the epoxy group-containing silane coupling agent (D2).

The silane coupling agent (D) may be contained in at least one of the base composition (I) and the curing agent composition (II), and may be contained only in the base composition (I), may be contained only in the curing agent composition (II), or may be contained in both the base composition (I) and the curing agent composition (II). In one embodiment, the amino group-containing silane coupling agent (D1) is preferably contained in the base composition (I), and the epoxy group-containing silane coupling agent (D2) is preferably contained in the curing agent composition (II).

(E) Benzotriazole Compound At least one of the base composition (I) and the curing agent (II) composition contains a benzotriazole compound (E). By containing the benzotriazole compound (E), the corrosion resistance of the resulting coating film is good.

The benzotriazole compound (E) is preferably a benzotriazole compound that does not have an ultraviolet absorbing function, and preferably does not include, for example, a benzotriazole compound in which an alkylphenol group is bonded to the nitrogen atom at the 2-position of the benzotriazole skeleton.

The benzotriazole compound (E) is preferably represented by the following formula (3):

［式（３）中、
Ｒ^４は、Ｃ_１－４アルキル基、カルボキシル基又は水素原子を表し、
Ｒ^５は、置換又は非置換のアミノアルキル基、ホスホニウム塩基、ナトリウム原子又は水素原子を表す。］
で表され得る。前記ベンゾトリアゾール化合物（Ｅ）は、式（３）で表される化合物の互変異性体であってもよい。

[In formula (3),
^R4 represents a _C1-4 alkyl group, a carboxyl group, or a hydrogen atom;
^R5 represents a substituted or unsubstituted aminoalkyl group, a phosphonium base, a sodium atom, or a hydrogen atom.
The benzotriazole compound (E) may be a tautomer of the compound represented by formula (3).

Specific examples of the benzotriazole compound (E) include 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1,2,3-benzotriazole sodium salt aqueous solution, tolyltriazole, nitrobenzotriazole, 1H-benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate, N,N-bis(2-ethylhexyl)(1H-benzotriazol-1-yl)methylamine, and 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4or5-methylbenzotriazole.

As the benzotriazole compound (E), a commercially available product may be used. Examples of the commercially available product include BT-120, BT-120SG, BT-LX, CBT-1, CBT-SG, TT-LX, JCL-400, TT-130F, and TT-LYX (all manufactured by Johoku Chemical Industry Co., Ltd.), VENZONE N-BTA, VENZONE OA-372, and VENZONE OA-386 (all manufactured by Daiwa Kasei Co., Ltd.), etc.

The content of the benzotriazole compound (E) is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more and 5 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the total resin solids of the coating composition. When the content of the benzotriazole compound (E) is within the above range, the corrosion resistance and weather resistance of the resulting coating film can be improved.

The benzotriazole compound (E) may be contained in either the base composition (I) or the hardener composition (II), and is preferably contained in the base composition (I).

(F) Amine compound At least one of the base composition (I) and the curing agent (II) composition preferably contains an amine compound (F). By containing the amine compound (F), the corrosion resistance of the resulting coating film can be improved.

The amine compound (F) preferably has an aliphatic hydrocarbon group having 6 or more carbon atoms. The aliphatic hydrocarbon group may be a saturated or unsaturated aliphatic hydrocarbon group, and the number of carbon atoms in the aliphatic hydrocarbon group is preferably 8 to 20. The aliphatic hydrocarbon group is preferably bonded to a nitrogen atom of the amine compound (F).

The amine compound (F) preferably has one selected from a _C1-4 alkyl group, a _C1-4 hydroxyalkyl group and a polyoxyalkylene group, more preferably a polyoxyalkylene group, in addition to the aliphatic hydrocarbon group. The polyoxyalkylene group may preferably be a polyoxyethylene group and/or a polyoxypropylene group, more preferably a polyoxyalkylene group.

Specific examples of the amine compound (F) include alkylamines, tallow alkylamines, bis(2-hydroxyethyl)alkyl(coconut)amines, polyoxyethylene alkyl(coconut)amines, polyoxyethylene alkyl(coconut)amines, bis(2-hydroxyethyl)alkyl(oleyl)amines, polyoxyethylene alkyl(oleyl)amines, polyoxyethylene alkyl(oleyl)amines, bis(2-hydroxyethyl)alkyl(tallow)amines, polyoxyethylene alkyl(tallow)amines, polyoxyethylene alkyl(tallow)amines, bis(2-hydroxyethyl)alkyl(hardened tallow)amines, polyoxyethylene alkyl(hardened tallow)amines, coconut alkyl dimethylamines, tallow alkyl dimethylamines, and dodecyl dimethylamine.

As the amine compound (F), a commercially available product may be used. Examples of the commercially available product include Liponol C/12, Liponol C/15, Liponol C/25, Liponol O/12, Liponol O/15, Liponol O/25, Liponol T/12, Liponol T/15, Liponol T/25, Liponol HT/12, Liponol HT/14, Lipomin DMMCD, Lipomin DMTD, and Lipomin DM12D (manufactured by Lion Specialty Chemicals).

The content of the amine compound (F) is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more and 5 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the total resin solid content of the coating composition. When the content of the amine compound (F) is within the above range, the corrosion resistance of the resulting coating film can be improved.

The coating composition may further contain a pigment. Examples of the pigment include color pigments, extender pigments, and anti-rust pigments, and it is preferable that the coating composition contains one or more selected from color pigments and extender pigments.

Examples of the color pigments include organic color pigments such as azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, diketopyrrolopyrrole pigments, and metal complex pigments; and inorganic color pigments such as yellow lead, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide.

The content of the color pigment is preferably 5 parts by mass or more and 55 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, and even more preferably 15 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the resin solids content of the coating composition.

Examples of the extender pigment include talc, clay, calcium carbonate, magnesium carbonate, barium sulfate, silicic acid, silicates, aluminum oxide hydrate, calcium sulfate, gypsum, micaceous iron oxide (MIO), glass flake, suzolite mica, and clarite mica.
In one embodiment, the extender pigment is selected from the group consisting of calcium carbonate, barium sulfate, and talc. For example, heavy calcium carbonate, light calcium carbonate, precipitated barium sulfate, and surface-treated talc can be used. Such extender pigments can be used alone or in combination.

The content of the extender pigment is preferably 0 parts by mass or more and 100 parts by mass or less, more preferably 0 parts by mass or more and 70 parts by mass or less, and even more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the resin solids content of the paint composition.

The rust-preventive pigment is preferably a phosphoric acid-based rust-preventive pigment. Examples of the phosphoric acid-based rust-preventive pigment include metal salts of phosphoric acids. Examples of the phosphoric acids include orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, and metaphosphoric acid, and examples of metals that may be contained in the metal salts include iron, aluminum, calcium, molybdenum, and zinc. Specific examples of the phosphoric acid-based rust-preventive pigment include iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, aluminum phosphomolybdate, and aluminum zinc phosphomolybdate.

In one embodiment, the content of the anti-rust pigment is preferably 0 parts by mass or more and 100 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the resin solid content of the coating composition.

In another aspect, the coating composition of the present disclosure can provide a coating film having both corrosion resistance and weather resistance even when it does not contain an anti-rust pigment. From this perspective, the content of the anti-rust pigment may be 0 parts by mass or more and 30 parts by mass or less, further 0 parts by mass or more and 20 parts by mass or less, and particularly 0 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the resin solid content of the coating composition.

Other components, etc. The solvent-based topcoat paint composition may contain various known additives as necessary. As the various additives, additives used in paint compositions can be appropriately used, for example, resin particles, other resin components, anti-sagging/anti-settling agents, curing catalysts (organometallic catalysts), color separation inhibitors, dispersants, antifoaming/anti-popping agents, viscosity regulators, leveling agents, matting agents, UV absorbers, light stabilizers, antioxidants, surface conditioners, pinhole inhibitors, plasticizers, film-forming assistants, etc. The blending amounts of these components are appropriately adjusted within a range that does not impair the effects of the present disclosure.

In the coating composition, the total solid content is preferably 20% by mass or more and 75% by mass or less, and more preferably 30% by mass or more and 70% by mass or less.

<Preparation of Coating Composition>
The base composition (I) and the hardener composition (II) of the coating composition can be prepared by mixing the various components by a method known to those skilled in the art. The coating composition can be prepared by a method commonly used by those skilled in the art. For example, a kneading and mixing means using a kneader or roll, or a dispersing and mixing means using a sand grind mill or disperser, or other methods commonly used by those skilled in the art can be used.

The timing for mixing the base composition (I) and the hardener composition (II) in the coating composition may be immediately before use. For example, the base composition (I) and the hardener composition (II) may be mixed before use and applied by a normal coating method. Alternatively, the coating may be applied by sending each liquid to a two-liquid mixing gun and mixing them at the tip of the gun.

(Paint film formation process)
In the coating film forming step, the coating composition is applied onto an object to be coated, thereby forming a coating film.

The method of applying such a coating composition is not particularly limited, but examples include commonly used coating methods such as immersion, brush, roller, roll coater, air spray, airless spray, curtain flow coater, roller curtain coater, and die coater. In the above-mentioned spray coating, a two-liquid mixing gun may be used as necessary. These can be appropriately selected depending on the object to be coated.

The coating composition can be applied so that the dry coating film has a thickness of 30 to 200 μm, preferably 40 to 150 μm (hereinafter, the "dry coating film" is also referred to as the "coating film" or "dry coating film", and the "dry coating film" is also referred to as the "coating film thickness" or "dry coating film thickness"). In one embodiment, the coating composition can be applied so that the dry coating film has a thickness of 50 to 120 μm, further 60 to 110 μm. By using the coating composition, a smooth and defect-free coating film can be obtained even when a thick coating is applied. In addition, by making the coating film 30 μm or more, it becomes easy to sufficiently protect the substrate, and by making it 100 μm or less, it becomes easy to suppress the occurrence of defects such as popping in the coating film.

Examples of the substrate include metal substrates such as iron, zinc, tin, copper, titanium, and tinplate. These metal substrates may be plated with zinc, copper, chromium, etc., or may be surface-treated with a surface treatment agent such as chromate, zinc phosphate, or zirconium salt.

The coating composition of the present disclosure can be suitably used for coating objects with large heat capacity, such as metal substrates, which are difficult to sufficiently transfer heat to in a heating furnace. Specific examples of such coating objects include construction machinery (e.g., bulldozers, scrapers, hydraulic excavators, excavators, transport machines (trucks, trailers, etc.), cranes and loading machines, foundation construction machines (diesel hammers, hydraulic hammers, etc.), tunnel construction machines (boring machines, etc.), road rollers, etc.); industrial machinery such as light and heavy electrical equipment, agricultural machinery, steel furniture, machine tools, and large vehicles, which are called general industrial use; and other coating objects that are difficult to heat up even when heated, etc. The method for producing a multilayer coating film in the present disclosure can be suitably used for coating construction machinery or industrial machinery, which are coating objects with large heat capacity and difficult to heat up even when heated.

(Drying process)
In the drying step, the coating film is dried, thereby forming a coating film.

In one embodiment, the drying temperature may be 5 to 35°C, and the drying time may be 1 to 10 days. In another embodiment, the drying temperature may be, for example, 50 to 100°C, or even 60 to 80°C, and the drying time in this case may be 15 to 60 minutes.

The coating composition of the present disclosure can form a coating film with good corrosion resistance and weather resistance with a single coat. Therefore, the coating composition of the present disclosure can be suitably used for coating objects with a large heat capacity, such as construction machinery or industrial machinery.

The present disclosure will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

<Production of Resin>
(Production Example 1) Preparation of Coating Film-Forming Resin (A1-1) 60 parts by mass of butyl acetate was charged into a 1 L reaction vessel equipped with a stirrer, a temperature regulator, a dropping funnel, a reflux condenser, a nitrogen inlet tube and a thermometer, and the temperature was set to 120 ° C. Next, 25.0 parts by mass of styrene, 0.6 parts by mass of methacrylic acid, 8.7 parts by mass of methyl methacrylate, 19.7 parts by mass of 2-hydroxyethyl methacrylate, 1.0 parts by mass of n-butyl acrylate, 45.0 parts by mass of n-butyl methacrylate and 4 parts by mass of t-butylperoxy-2-ethylhexanoate as a reaction initiator were charged into the dropping funnel to prepare a monomer solution. While maintaining the inside of the reaction vessel at 120 ° C., this monomer solution was dropped over 3 hours. After the dropwise addition, the mixture was maintained at 120° C. for an additional hour to obtain a coating film-forming resin (A1-1) (number average molecular weight: 3,000, solids hydroxyl value: 85 mg KOH/g, solids acid value: 4 mg KOH/g, solids concentration: 60% by mass).

(Preparation Examples 2 to 5) Preparation of Coating-Forming Resins (A1-2) to (A1-5) Coating-forming resins (A1-2) to (A1-5) were prepared in the same manner as above, except that the monomer types and amounts were changed as shown in Table 1. The specific values of each coating-forming resin, such as the number average molecular weight, are shown in Table 1.

(Production Example 6) Preparation of coating film-forming resin (A2-1) 51.6 parts by mass of isophthalic acid, 6.2 parts by mass of adipic acid, 15.4 parts by mass of neopentyl glycol, 8.2 parts by mass of trimethylolpropane, 18.6 parts by mass of 1,6-hexanediol, 0.05 parts by mass of di-n-butyltin oxide and 3 parts by mass of xylene were mixed in a reaction vessel equipped with a stirrer, a temperature regulator, a reflux condenser, a nitrogen inlet tube and a thermometer, and the temperature was gradually raised to 220 ° C. under a nitrogen atmosphere, and an esterification reaction was carried out while distilling off the water produced. The reaction was allowed to proceed until the acid value of the reaction product was 40, and then 55 parts by mass of isobutyl acetate was added to obtain a coating film-forming resin (A2-1) (number average molecular weight: 1,200, solid acid value: 40 mg KOH / g, solid hydroxyl value: 100 mg KOH / g, solid concentration: 60% by mass).

(Preparation Examples 7 to 10) Preparation of Film-Forming Resins (A2-2) to (A2-4) Film-forming resins (A2-2) to (A2-4) were prepared in the same manner as above, except that the monomer types and amounts were changed as shown in Table 2. Table 2 shows the specific values of each film-forming resin, such as the number average molecular weight.

Example 1
<Production of Coating Composition 1>
In a dispersion vessel, 48 parts by mass of the coating film-forming resin (A1-1) (28.80 parts by mass as solids), 16.75 parts by mass of heavy calcium carbonate Super #2000 as an extender pigment, 12.55 parts by mass of TAROX synthetic iron oxide LL-XLO as a coloring pigment, 2.0 parts by mass of BYK-161 as a dispersant, and 10 parts by mass of butyl acetate as an organic solvent (C-1) were added, and glass beads were added and dispersed, and the particle size was dispersed until it became 12 μm or less. Then, 0.33 parts by mass of BT-120 as a benzotriazole compound (E-1), 0.33 parts by mass of KBE-903 as an amino group-containing silane coupling agent (D1-1), 2.00 parts by mass of TINUVIN292 as a light stabilizer, and 1.00 parts by mass of TINUVIN384-2 as an ultraviolet absorber were added, and the mixture was stirred and mixed to prepare a main composition 1. The benzotriazole compound (E-1) was used by dissolving 0.33 parts by mass of BT-120 in 1.0 part by mass of dipropylene glycol monomethyl ether as the organic solvent (C-2).

Separately, 16.8 parts by mass of a butyl acetate solution of Duranate TKA-100 (solids concentration: 50% by mass) as an isocyanurate-type polyisocyanate compound and 3 parts by mass of KBM403 as an epoxy group-containing silane coupling agent (D2-1) were added and stirred to obtain hardener composition 1.

<Preparation of test specimens having coating film>
A JIS G 3141 (SPCC-SB) cold-rolled steel plate having a size of 0.8×70×150 mm was polished and degreased with xylene. Next, the isocyanate group of the polyisocyanate compound contained in the curing agent composition 1 was mixed with the hydroxyl group of the acrylic resin, which is the coating film-forming resin in the main composition 1, using a disperser so that the molar ratio (NCO/OH) was 1.0 (coating composition (1)), and the coating was applied to the steel plate using an air spray so that the dry film thickness was 70 μm to form an undried coating film. After leaving it at room temperature (23° C.) for 10 minutes, it was dried (forced drying) at 80° C. for 30 minutes to form a coating film, and a test piece was obtained.

<Examples 2 to 39 and Comparative Examples 1 to 7>
Coating compositions were produced in the same manner as in Example 1, except that the type and/or amount of each component was changed to the amounts shown in Tables 3 to 6.

(Details of materials used)
Polyisocyanate Compound (B)
(B-1) Duranate TKA-100 (manufactured by Asahi Kasei Corporation, isocyanurate-type polyisocyanate), NCO content: 21.7% by mass, solid content: 100% by mass
(B-2) Duranate D201 (manufactured by Asahi Kasei Corporation, bifunctional polyisocyanate), NCO content: 15.8% by mass, solid content: 100% by mass
(B-3) Desmodur N31100 (manufactured by Sumika Covestro Urethane Co., Ltd., allophanate type polyisocyanate), NCO content: 19.5% by mass, solid content concentration: 100% by mass
Organic solvent (C)
(C-1) Butyl acetate (manufactured by Kyowa Hakko Chemical Co., Ltd.)
(C-2) Dipropylene glycol monomethyl ether (manufactured by The Dow Chemical Company)
Silane coupling agent (D)
(D1-1) KBE-903 (Shin-Etsu Chemical Co., Ltd., 3-aminopropyltriethoxysilane), active ingredient concentration: 100% by mass
(D1-2) KBM-603 (Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane), active ingredient concentration: 100% by mass
(D2-1) KBM-403 (Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane), active ingredient concentration: 100% by mass
(D2-2) KBE-403 (Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltriethoxysilane), active ingredient concentration: 100% by mass
(D2-3) KBM-4803 (manufactured by Shin-Etsu Chemical Co., Ltd., 8-glycidoxyoctyltrimethoxysilane), active ingredient concentration: 100% by mass
(d-1) KBM-3033 (manufactured by Shin-Etsu Chemical Co., Ltd., n-propyltrimethoxysilane), active ingredient concentration: 100% by mass
Benzotriazole Compound (E)
(E-1) BT-120 (manufactured by Johoku Chemical Industry Co., Ltd., 1,2,3-benzotriazole), active ingredient concentration: 100% by mass
(E-2) BT-LX (manufactured by Johoku Chemical Industry Co., Ltd., 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole), active ingredient concentration: 100% by mass
(E-3), TINUVIN99-2 (manufactured by BASF Japan, C7-C9-alkyl-3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]propionether, ultraviolet absorber), active ingredient concentration: 95% by mass
Amine Compound (F)
(F-1) Liponol T/15 (manufactured by Lion Specialty Chemicals, polyoxyethylene alkyl (beef tallow) amine), active ingredient concentration: 100% by mass
(F-2) Liponol T/25 (manufactured by Lion Specialty Chemicals, polyoxyethylene alkyl (beef tallow) amine), active ingredient concentration: 100% by mass
Other materials: Super #2000 (made by Maruo Calcium Co., Ltd., heavy calcium carbonate; extender pigment)
TAROX synthetic iron oxide LL-XLO (manufactured by Titanium Industries Co., Ltd., synthetic iron oxide; color pigment)
LF Bosei ZP-DL (Kikuchi Color Co., Ltd., zinc phosphate, anti-rust pigment)
BYK-161 (BYK Japan, dispersant)
TINUVIN 292 (BASF Japan, light stabilizer)
TINUVIN384-2 (manufactured by BASF Japan, ultraviolet absorber)

<Evaluation items>
1) Corrosion Resistance A 10 cm long cross-cut was made with a cutter knife on the coating film of the test plate obtained in the Examples and Comparative Examples so as to reach the substrate, and a salt spray test (SST) was carried out for 120 hours using a salt spray tester ST-11L (manufactured by Suga Test Instruments Co., Ltd.) in accordance with the neutral salt spray resistance test method described in JIS K 5600-7-1 (JIS Z 2371). After the test, the corrosion resistance of the coating film was visually evaluated according to the following criteria based on the occurrence of rust and blisters from the cross-cut portion.
○: The maximum width of the rust or blister that has occurred is less than 1 mm from the crosscut portion. ○△: The maximum width of the rust or blister that has occurred is 1 mm or more and less than 2 mm from the crosscut portion. △: The maximum width of the rust or blister that has occurred is 2 mm or more and less than 3 mm from the crosscut portion. ×: The maximum width of the rust or blister that has occurred is 3 mm or more from the crosscut portion.

2) Weather resistance The test plates obtained in the examples and comparative examples were subjected to an accelerated weather resistance test using a Super Xenon Weather Meter SX2-75 (manufactured by Suga Test Instruments Co., Ltd.) according to the xenon lamp method described in JIS K 5600-7-7. The 60° gloss value of the coating film after 1,000 hours of testing was measured using a multi-angle gloss meter GS-4K (manufactured by Suga Test Instruments Co., Ltd.), and the weather resistance of the coating film was evaluated according to the following criteria based on the rate of change (gloss retention) from the 60° gloss value before the test.
○: Gloss retention is 80% or more. ○△: Gloss retention is 70% or more but less than 80%. △: Gloss retention is 60% or more but less than 70%. ×: Gloss retention is less than 60%.

For all evaluation items, a grade of △ or higher was deemed a pass. However, if both corrosion resistance and weather resistance were △, the item was deemed a fail.

Examples 1 to 38 are examples of the present invention, and it was confirmed that a coating film with good corrosion resistance and weather resistance can be formed with a single coat of paint.

Comparative Example 1 is an example in which the amino group-containing silane coupling agent (D1) was not used, and the corrosion resistance and weather resistance of the resulting coating film were not fully satisfactory.
Comparative Example 2 is an example in which neither the amino group-containing silane coupling agent (D1) nor the benzotriazole compound (E) was used, and the corrosion resistance and weather resistance of the resulting coating film were not fully satisfactory.
Comparative Example 3 is an example in which the benzotriazole compound (E) was not used, and the corrosion prevention properties of the resulting coating film were not fully satisfactory.
Comparative Example 4 is an example in which the epoxy group-containing silane coupling agent (D2) was not used, and the corrosion resistance and weather resistance of the resulting coating film were not fully satisfactory.
Comparative Example 5 is an example in which neither the epoxy group-containing silane coupling agent (D2) nor the benzotriazole compound (E) was used, and the corrosion resistance and weather resistance of the resulting coating film were not fully satisfactory.
Comparative Example 6 is an example in which neither the amino group-containing silane coupling agent (D1) nor the epoxy group-containing silane coupling agent (D2) was used, and the resulting coating film had poor weather resistance and was not fully satisfactory in terms of corrosion resistance.
Comparative Example 7 is an example in which a silane coupling agent other than the amino group-containing silane coupling agent (D1) and the epoxy group-containing silane coupling agent (D2) was used, and the corrosion resistance and weather resistance of the obtained coating film were not fully satisfactory.

The coating composition of the present disclosure can form a coating film with good corrosion resistance and weather resistance with a single coat. Therefore, the coating composition of the present disclosure can be suitably used for coating objects with a large heat capacity, such as construction machinery or industrial machinery.

Claims (9)

A coating composition comprising a base composition (I) and a curing agent composition (II),
At least one of the base composition (I) and the curing agent composition (II) contains at least one of a silane coupling agent (D) and/or a hydrolysate or condensate of a silane coupling agent,
The silane coupling agent (D) includes an amino group-containing silane coupling agent (D1) and an epoxy group-containing silane coupling agent (D2),
The base composition (I) contains a coating film-forming resin (A) ; an amino group-containing silane coupling agent (D1) and/or at least one of a hydrolysis product or a condensation product of the amino group-containing silane coupling agent (D1); and a benzotriazole compound (E) .
The coating film-forming resin (A) comprises an acrylic resin (A1) having a hydroxyl group and/or a polyester resin (A2) having a hydroxyl group,
The curing agent composition (II) is a coating composition comprising at least one of a polyisocyanate compound (B); and an epoxy group-containing silane coupling agent (D2), and/or a hydrolysis product or condensation product of the epoxy group- containing silane coupling agent (D2) . The coating composition according to claim 1, wherein the content of the silane coupling agent (D) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the total resin solid content of the coating composition. The coating composition according to claim 1, wherein the ratio of the content of the amino group-containing silane coupling agent (D1) to the content of the epoxy group-containing silane coupling agent (D2) [(D2)/(D1)] is 0.3 or more and 20 or less. The coating composition according to claim 1, wherein the content of the benzotriazole compound (E) is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total resin solid content of the coating composition. The coating composition according to claim 1, wherein the hydroxyl value of the film-forming resin (A) is 30 mg KOH/g or more and 300 mg KOH/g or less. The coating composition according to claim 1, wherein the polyisocyanate compound (B) includes at least one selected from an aliphatic polyisocyanate compound; an aromatic polyisocyanate compound; an alicyclic polyisocyanate compound; a polymer of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound; and a modified product of an aliphatic polyisocyanate compound, an aromatic polyisocyanate compound, or an alicyclic polyisocyanate compound. The coating composition according to claim 1, wherein the molar ratio (NCO/OH) of the isocyanate groups contained in the polyisocyanate compound (B) to the hydroxyl groups contained in the coating film-forming resin (A) is 0.4 or more and 1.6 or less. At least one of the base composition (I) and the curing agent composition (II) contains an amine compound (F),
The coating composition according to any one of claims 1 to 7 , wherein the amine compound (F) has an aliphatic hydrocarbon group having 6 or more carbon atoms. 9. The coating composition according to claim 8 , wherein the content of the amine compound (F) is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of a total of resin solid contents of the coating composition.