JP7493366B2 - Coating composition - Google Patents

Description

The present invention relates to a coating composition, a coating film, and a method for producing a substrate with a coating film.

Conventionally, (large) steel structures such as ships, bridges, tanks, plants, marine buoys, and pipelines are coated with an epoxy resin-based anticorrosive paint composition for the purpose of corrosion protection, and then a topcoat paint composition is applied on top of the formed anticorrosive coating film for the purpose of improving design and weather resistance.

Known examples of the topcoat paint composition include two-liquid reactive curing topcoat paint compositions (e.g., acrylic urethane resin-based paint compositions, fluorourethane resin-based paint compositions). Also known as topcoat paint compositions that are considerate of the human body and the environment during painting are topcoat paint compositions that do not contain compounds with isocyanate groups, specifically polysiloxane resin-based paint compositions.

Polysiloxane resin-based coating compositions are generally capable of forming coating films with high coating hardness, but on the other hand, it has become apparent that the coating films do not have sufficient flexibility, such as bending resistance.
In this regard, Patent Document 1 describes a coating composition that contains a carboxy group-containing acrylic copolymer, an organosiloxane, a tertiary amino group-containing urethane prepolymer, and an epoxy group-containing organosilane compound as a coating composition that can form a coating film that is excellent in flexibility and the like without impairing the weather resistance of the coating film obtained from the polysiloxane resin-based coating composition.

JP 2005-179573 A

It has been found that coating films obtained from conventional topcoat coating compositions such as the coating composition described in Patent Document 1 have room for improvement in terms of the balance between coating hardness and flex resistance, weather resistance, and/or chemical resistance.
Furthermore, conventional topcoat paint compositions such as the paint composition described in Patent Document 1 contain a compound having an isocyanate group, or a compound having an isocyanate group is used in the preparation stage of the paint composition, so it is also desirable to reduce the burden on the human body and the environment during application and preparation of the paint composition.

The present invention has been made in consideration of the above, and aims to provide a coating composition that can maintain its appearance and gloss for a long period of time even when exposed to an environment with high levels of solar radiation and severe ultraviolet rays, and can form a coating film that has a well-balanced coating film hardness and flex resistance, and excellent chemical resistance.

As a result of intensive research into methods for solving the above problems, the inventors discovered that the above problems could be solved by a specific coating composition, which led to the completion of the present invention.
A configuration example of the present invention is as follows.

<1> A coating composition comprising a tertiary amino group-containing acrylic resin (A), a carboxy group-containing resin (B), and an epoxy group-containing silane compound (C).

<2> The coating composition described in <1>, which is room temperature curable.

<3> The coating composition according to <1> or <2>, wherein the resin (B) contains at least one resin selected from a carboxyl group-containing acrylic resin (B1) and a carboxyl group-containing fluororesin (B2).

<4> The coating composition according to any one of <1> to <3>, further comprising a silicone resin (D).

<5> A coating film formed from the coating composition according to any one of <1> to <4>.
<6> A method for producing a substrate with a coating film, comprising the following steps [1] and [2]:
[1] A step of applying the coating composition according to any one of <1> to <4> to a substrate. [2] A step of drying the applied coating composition to form a coating film.

According to the present invention, a weather-resistant coating composition which can be cured at room temperature and has excellent drying properties can be provided. This composition can maintain its appearance and gloss for a long period of time even when exposed to an environment with high levels of solar radiation and severe ultraviolet rays (hereinafter also referred to simply as "weather resistance"), and can form a coating film which has a well-balanced excellent coating film hardness and flex resistance, and excellent chemical resistance.
Furthermore, according to the present invention, it is possible to obtain a coating composition that does not contain or does not use compounds having isocyanate groups that are harmful to the human body and the environment, and therefore it is possible to obtain a coating composition that imposes less strain on the human body and the environment during application or preparation of the coating composition.

<Paint composition>
A coating composition according to one embodiment of the present invention (hereinafter also simply referred to as "the composition") contains a tertiary amino group-containing acrylic resin (A) (hereinafter also referred to as "component (A)"; the same applies to the other components), a carboxy group-containing resin (B) and an epoxy group-containing silane compound (C).

The composition can be easily cured under room temperature drying conditions, and can form a coating film that has excellent weather resistance for a long period of time, even in harsh environments such as those used for anticorrosive coating.
Since the composition cures at room temperature, a coating film can be formed from the composition without being limited by the type of substrate, even if the substrate to be coated has poor heat resistance (a substrate on which a coating film with poor heat resistance has been formed). In addition, since the composition can form a weather-resistant coating film having long-term weather resistance, the period until repainting can be extended and the painting process can be omitted, so that the use of the composition can significantly reduce the maintenance costs associated with painting substrates such as steel structures.

The present composition is preferably applied as a topcoat paint to the outermost surface of a substrate (the surface opposite the substrate) so that its effects can be more fully exerted. The present composition can also be used as an intermediate topcoat paint that serves as both an intermediate coat paint and a topcoat paint.

The composition may be a water-based paint, taking into consideration the burden on the human body and the environment, but it is preferable that it be a solvent-based paint, since drying and curing properties are insufficient in low-temperature environments (e.g., below 5°C).

The composition may be a one-component composition, but considering storage stability and ease of storage, it is preferably a multi-component composition containing a base agent and a curing agent, for example, a two-component composition containing a base agent containing the components (A) and (B) and a curing agent containing the component (C) is desirable. The composition may also be a three-component or higher composition containing a third agent other than the base agent and curing agent.
These base agent, hardener and third agent are usually stored, preserved, transported, etc. in separate containers, and are mixed together immediately before use.

<Tertiary Amino Group-Containing Acrylic Resin (A)>
Component (A) is not particularly limited as long as it is a resin other than component (B), that is, a resin that does not contain a carboxy group and has at least one tertiary amino group in one molecule.
Furthermore, when component (A) contains a tertiary amino group, the reaction between component (B) and component (C) can be promoted.
The component (A) used in the present composition may be one type or two or more types.

In this specification, "acrylic resin" refers to acrylic resin and/or methacrylic resin. Also, "(meth)acrylic" is a general term for acrylic and methacrylic. Similar expressions have similar meanings.

Component (A) can be synthesized, for example, by (co)polymerizing a tertiary amino group-containing unsaturated monomer (a-1) by a known method, specifically, by radical (co)polymerizing the tertiary amino group-containing unsaturated monomer (a-1) and, if necessary, other unsaturated monomers (a-2), provided that at least one of the monomers used in this (co)polymerization is a compound having a (meth)acryloyl group.
In addition, component (A) may be prepared by radically (co)polymerizing other unsaturated monomers (a-2) (at least one of which is a compound having a (meth)acryloyl group) and then modifying the resulting resin so that it has a tertiary amino group.
Component (A) can be synthesized by a conventional method, specifically, by reacting monomers in the presence of a polymerization initiator and a solvent.

Examples of the monomer (a-1) include
dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminobutyl (meth)acrylate;
tertiary amino group-containing (meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dipropylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N,N-dimethylaminobutyl(meth)acrylamide;
tertiary amino group-containing vinyl ethers, such as dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, dimethylaminopropyl vinyl ether, and dimethylaminobutyl vinyl ether;
Tertiary amino group-containing aromatic unsaturated monomers such as vinylpyridine;
Examples include:
The monomer (a-1) may be used alone or in combination of two or more.

As the monomer (a-1), among these, dialkylaminoalkyl (meth)acrylate is preferred from the viewpoints of the stability of the resin (A) and reactivity with the epoxy group-containing compound, and dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate are more preferred.

The amount of the monomer (a-1) used is preferably 1% by mass or more, more preferably 2% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the total of the monomers used in synthesizing component (A), from the viewpoints that a composition having excellent drying properties and/or curing properties can be easily obtained, and a coating film having excellent chemical resistance, water resistance, and coating film hardness can be easily obtained.

Examples of the monomer (a-2) include
(meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, and alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate;
hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, mono(meth)acrylate of cyclohexanedimethanol, polyoxyalkylene glycol (meth)acrylate (the alkylene group has 2 to 4 carbon atoms, and the number of moles of alkylene oxide added is 1 to 50), and caprolactone-modified hydroxy(meth)acrylate;
Acid anhydride group-containing unsaturated monomers such as maleic anhydride and itaconic anhydride;
Amide group-containing unsaturated monomers such as N-butoxymethyl(meth)acrylamide, (meth)acrylamide, diacetone(meth)acrylamide, and n-methylol(meth)acrylamide;
Vinyl group-containing unsaturated monomers such as styrene, vinyl toluene, α-methyl styrene, vinyl acetate, and vinyl benzoate;
Cyano group-containing unsaturated monomers such as acrylonitrile and methacrylonitrile;
Sulfonic acid group-containing unsaturated monomers such as p-styrenesulfonic acid;
Sulfonamide group-containing unsaturated monomers such as p-styrenesulfonamide and N-methyl-p-styrenesulfonamide;
Fluorine-containing vinyl monomers;
Ultraviolet absorbing unsaturated monomers (R-UVA) such as 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzotriazole and 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole;
Light-stable unsaturated monomers (R-HALS) such as 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine and 4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine;
Examples include:
The monomer (a-2) may be used alone or in combination of two or more.

Among these, methyl (meth)acrylate, n-butyl (meth)acrylate, and styrene are preferred as the monomer (a-2) because they can easily produce a coating film that is well-balanced in terms of weather resistance, flexibility (flexibility), and gloss.

The amount of the monomer (a-2) used is preferably 70% by mass or more, more preferably 80% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, based on 100% by mass of the total of the monomers used in synthesizing component (A), from the viewpoints that a composition having excellent drying properties and/or curing properties can be easily obtained, and a coating film having excellent chemical resistance, water resistance, and coating film hardness can be easily obtained.

The glass transition temperature (Tg) of component (A) is preferably -5°C or higher, more preferably 0°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, from the viewpoints of being able to easily obtain a coating film that has a good balance between coating film hardness and flex resistance and is less prone to stickiness and cracking.

In the present invention, the Tg is a value approximately calculated by the following Fox formula described in Fox T. G., Bull. Am. Physics Soc. 1, 3, p. 123 (1956).
In addition, when a resin contains a constituent unit derived from a monomer whose Tg is unknown, such as a monomer whose Tg (Tg _n ) is not described in the following document, and the total amount of the constituent units derived from the monomer whose Tg is unknown is 10 mass% or less, the Tg is calculated using only the monomer whose Tg is known, and when the total amount of the constituent units derived from the monomer whose Tg is unknown exceeds 10 mass%, the Tg of the resin can be measured by DSC (differential scanning calorimetry) or the like.

［式中、Ｘ_nは、成分（Ａ）を合成する際に用いたモノマーｎの、成分（Ａ）を合成する際に用いたモノマー全量に対する質量分率（質量％／１００）であり、Ｔｇ_nは、該モノマーｎのホモポリマーのガラス転移温度（ケルビン）である。］

[In the formula, _Xn is the mass fraction (mass%/100) of the monomer n used in synthesizing component (A) relative to the total amount of monomers used in synthesizing component (A), and _Tgn is the glass transition temperature (Kelvin) of a homopolymer of the monomer n.]

For Tg _n , the values described in, for example, Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975) can be referred to. According to this handbook, for example, the Tg of polystyrene is 373K, the Tg of polybutyl methacrylate is 293K, the Tg of polybutyl acrylate is 219K, the Tg of poly2-hydroxyethyl methacrylate is 328K, and the Tg of polymethacrylic acid is 458K.

The weight average molecular weight (hereinafter also simply referred to as "Mw") of component (A) is preferably 1,000 or more, more preferably 3,000 or more, and particularly preferably 4,000 or more, from the viewpoint of being able to easily obtain a coating film which is less likely to crack, has excellent flex resistance, and is excellent in weather resistance and chemical resistance, etc., and is preferably 100,000 or less, more preferably 50,000 or less, and particularly preferably 30,000 or less.
In the present invention, Mw is a weight average molecular weight calculated as standard polystyrene measured by GPC (gel permeation chromatography), and specifically, it can be measured by the method described in the following examples.

The amine value of the non-volatile content of the component (A) is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, and is preferably 50 mgKOH/g or less, more preferably 40 mgKOH/g or less.
By using component (A) having an amine value within the above range, a composition having excellent drying properties and/or curing properties can be easily obtained, and a coating film having excellent weather resistance and chemical resistance can be easily obtained.
The amine value can be measured in accordance with JIS K 7237:1995.

The content of component (A) (non-volatile content) in 100% by mass of the non-volatile content of the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and particularly preferably 40% by mass or less.
When the content of component (A) is within the above range, a coating film can be easily obtained which is less susceptible to cracking, has a good balance of weather resistance, coating hardness and flexibility (flex resistance), and has excellent adhesion to substrates.

The non-volatile content (solid content) of the composition refers to the mass percentage of the coating film (heating residue) after the composition is sufficiently reacted and cured (heated), or the coating film (heating residue) itself. The non-volatile content can be calculated by measuring the mass of the heating residue and the wire when 1±0.1 g of the composition (for example, the composition immediately after mixing the base agent and the curing agent) is weighed out and placed on a flat-bottomed dish, spread evenly using a wire of known mass, dried at 23°C for 24 hours, and then heated at a heating temperature of 108°C for 3 hours (at normal pressure). Note that this non-volatile content is equivalent to the total amount of solid content (components other than the solvent) of the raw material components used in the composition.

<Carboxy Group-Containing Resin (B)>
There are no particular limitations on component (B) so long as it has at least one carboxy group in one molecule.
The component (B) used in the present composition may be one type or two or more types.

Specific examples of component (B) include carboxyl group-containing acrylic resin (B1), carboxyl group-containing fluororesin (B2), carboxyl group-containing polyester resin, and carboxyl group-containing alkyd resin. Among these, carboxyl group-containing acrylic resin (B1) and carboxyl group-containing fluororesin (B2) are preferred because they can easily form a coating film that has a good balance of weather resistance and chemical resistance, and carboxyl group-containing acrylic resin (B1) is more preferred because of its ease of availability.

The Tg of component (B) is preferably −5° C. or higher, more preferably 0° C. or higher, and is preferably 50° C. or lower, more preferably 40° C. or lower, from the viewpoints of being able to easily obtain a coating film which is well-balanced in terms of coating hardness and flex resistance and which is less prone to stickiness, cracks, and the like.
The Tg can be measured or calculated in the same manner as described in the section on component (A).

When component (B1) is used as component (B), it is preferred that at least one type of component (B1), in particular all types of component (B1) used, satisfy the following requirements.
Requirement: Either the Tg of component (A) or the Tg of component (B1) is 10° C. or lower, and the other is 20° C. or higher. Preferably, either the Tg of component (A) or the Tg of component (B1) is 8° C. or lower, and the other is 25° C. or higher.
By satisfying this requirement, it is possible to easily obtain a coating film that is excellent in a well-balanced manner in coating hardness and flex resistance. When resins having a Tg of more than 20° C. are used as both component (A) and component (B1), it tends to be difficult to obtain a coating film that is excellent in flex resistance, and when resins having a Tg of less than 10° C. are used as both component (A) and component (B1), it tends to be difficult to obtain a coating film that is excellent in coating hardness.

When component (B2) is used as component (B), a coating film that is particularly well-balanced in terms of coating hardness and flex resistance can be easily obtained regardless of the relationship between the Tg of component (A) and the Tg of component (B2).

The Mw of component (B) is preferably 1,000 or more, more preferably 3,000 or more, and particularly preferably 4,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, and particularly preferably 30,000 or less, from the viewpoint of being able to easily obtain a coating film that is less likely to crack, has excellent flex resistance, and is excellent in weather resistance and chemical resistance.

The acid value of the non-volatile content of the component (B) is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, and is preferably 70 mgKOH/g or less, more preferably 60 mgKOH/g or less.
By using component (B) having an acid value within the above range, a composition having excellent drying properties and/or curing properties can be easily obtained, and a coating film having excellent weather resistance and chemical resistance can be easily obtained.
The acid value can be measured in accordance with JIS K 0070:1992.

The content of component (B) (non-volatile content) in 100% by mass of the non-volatile content of the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and particularly preferably 40% by mass or less.
When the content of component (B) is within the above range, a coating film having a good balance between excellent chemical resistance and flex resistance as well as excellent adhesion to the substrate can be easily obtained.

[Carboxy group-containing acrylic resin (B1)]
Component (B1) can be synthesized, for example, by (co)polymerizing a carboxyl group-containing unsaturated monomer by a known method, specifically, by radical (co)polymerizing a carboxyl group-containing unsaturated monomer and, if necessary, a non-carboxyl group-containing unsaturated monomer, provided that at least one of the monomers used in this (co)polymerization is a compound having a (meth)acryloyl group.
In addition, component (B1) may be prepared by radically (co)polymerizing a non-carboxyl group-containing unsaturated monomer (wherein at least one of the monomers is a compound having a (meth)acryloyl group) and then modifying the resulting resin so that it has a carboxy group.
Component (B) can be synthesized by a conventional method, specifically, by reacting monomers in the presence of a polymerization initiator and a solvent.

Examples of the carboxy group-containing unsaturated monomer include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, allyloxypropionic acid, 2-(meth)acryloylethylsuccinic acid, 3-butenoic acid, 4-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2-heptenoic acid, 3-heptenoic acid, 3-octenoic acid, 2-nonenoic acid, 3-nonenoic acid, 9-decenoic acid, 10-undecenoic acid, and 2-tridecenoic acid. Of these, it is preferable to use (meth)acrylic acid.
The carboxyl group-containing unsaturated monomer may be used alone or in combination of two or more kinds.

The amount of the carboxyl group-containing unsaturated monomer used is preferably 1% by mass or more, more preferably 2% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the total of the monomers used in synthesizing component (B1), from the viewpoints that a composition with excellent drying properties can be easily obtained, and a coating film with excellent chemical resistance, water resistance, and coating hardness can be easily obtained.

Examples of the unsaturated monomer not containing a carboxy group include the same monomers as those exemplified as the monomers (a-1) and (a-2) above. Among these, it is preferable to use methyl (meth)acrylate, n-butyl (meth)acrylate, and styrene.
The non-carboxyl group-containing unsaturated monomer may be used alone or in combination of two or more kinds.

The amount of the non-carboxyl group-containing unsaturated monomer used is preferably 70% by mass or more, more preferably 80% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, based on 100% by mass of the total of the monomers used in synthesizing component (B1), from the viewpoints that a composition having excellent drying properties and/or curing properties can be easily obtained, and a coating film having excellent chemical resistance, water resistance, and coating film hardness can be easily obtained.

[Carboxy group-containing fluororesin (B2)]
The component (B2) may be obtained by synthesizing, for example, a fluoroolefin and a carboxyl group-containing monomer by (co)polymerization using a known method, or may be a commercially available product. When synthesizing the component (B2), for example, the component (B2) can be synthesized by copolymerizing a fluoroolefin (b1) and an unsaturated carboxylic acid (b2) having a carboxyl group, and further copolymerizing a vinyl ether (b3) and/or a vinyl ester (b4) as necessary.

Examples of the fluoroolefins (b1) include
Fluoroethylenes such as CClF= _CF2 , CHCl= _CF2 , _CCl2 = _CF2 , CClF=CClF, CHF= _CCl2 , _CH2 =CClF, _CCl2 =CClF, _CF2 = _CF2 , and _CF2 = _CH2 ;
_CF2ClCF = _CF2 , CF3CCl ₌ CF2 _{, CF3CF} =CFCl, CF2ClCCl=CF2 _, CF2ClCF=CFCl, CFCl2CF ₌ CF2, CF3CCl ₌ CClF, _CF3CCl = _CCl2 , CClF2CF _{= CCl2 , CCl3CF = CF2 , CF2ClCCl =} CCl2, CFCl2CCl=CCl2, CF3CF _{= CHCl} , _{CClF2CF = CHCl} , _CH3CCl =CHCl, _CHF2CCl = _CCl2 , CF2ClCH= _CCl2 , _CF2ClCCl =CHCl, _CCl3 Fluoropropenes such as CF=CHCl, CHBrCF= _CCl2 , _CF2 = _{CFOCF3 , CF2} = _CFOC3F7 ;
Fluoroolefins _having 4 or more carbon atoms, such as _CF3CCl = _CFCF3 , _CF2 = _CFCF2CClF2 , _{and CF3CF2CF} = _CCl2 ;
Examples include:
Among these, perhaloolefins in which all hydrogen atoms of olefins are substituted with halogens, such as CF ₂ ═CF ₂ and CClF═CF ₂ , are preferred.
The fluoroolefins (b1) may be used alone or in combination of two or more.

Examples of the unsaturated carboxylic acids (b2) having a carboxy group include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, allyloxypropionic acid, 2-(meth)acryloylethylsuccinic acid, 3-butenoic acid, 4-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2-heptenoic acid, 3-heptenoic acid, 3-octenoic acid, 2-nonenoic acid, 3-nonenoic acid, 9-decenoic acid, 10-undecenoic acid, and 2-tridecenoic acid. One or more of the unsaturated carboxylic acids (b2) having a carboxy group may be used.

Examples of the vinyl ether (b3) include
aliphatic alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, octyl vinyl ether, neopentyl vinyl ether, and t-butyl vinyl ether;
alicyclic alkyl vinyl ethers such as cyclohexyl vinyl ether;
aromatic vinyl ethers such as phenyl vinyl ether, benzyl vinyl ether, and naphthyl vinyl ether;
isopropenyl ethers such as methyl isopropenyl ether, ethyl isopropenyl ether, propyl isopropenyl ether, butyl isopropenyl ether, and cyclohexyl isopropenyl ether;
hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 9-hydroxynonyl vinyl ether, 1-hydroxymethyl-4-vinyloxymethylcyclohexane, and 3-chloro-2-hydroxypropyl vinyl ether;
hydroxyalkyl isopropenyl ethers such as 2-hydroxyethyl isopropenyl ether, 3-hydroxypropyl isopropenyl ether, 4-hydroxybutyl isopropenyl ether, 9-hydroxynonyl isopropenyl ether, 1-hydroxymethyl-4-isopropenoxymethylcyclohexane, and 3-hydroxy-2-chloropropyl isopropenyl ether;
Examples include:
The vinyl ethers (b3) may be used alone or in combination of two or more.

Examples of the vinyl esters (b4) include compounds represented by CH ₂ ═CHOCOR ³ (R ³ : an optionally substituted aliphatic, alicyclic or aromatic monovalent hydrocarbon group having 1 to 20 carbon atoms).
The substituent in R ³ may be a hydroxyl group, a halogen atom, etc., but is preferably not a hydroxyl group.
The vinyl esters (b4) may be used alone or in combination of two or more.

Suitable examples of the vinyl ester (b4) include:
fatty acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl pivalate, vinyl caprylate, and vinyl stearate;
Aromatic carboxylic acid vinyl esters such as vinyl benzoate and vinyl pt-butylbenzoate;
Examples include:

In addition, when synthesizing the component (B2), monomers other than the above (b1) to (b4) may be used.
Examples of the other monomer include
Olefins such as ethylene, propylene, and isobutylene;
haloolefins such as vinyl chloride and vinylidene chloride;
Allyl carboxylates such as allyl formate, allyl butyrate, allyl benzoate, and allyl cyclohexanecarboxylate;
Allyl ethers such as allyl ethyl ether and allyl phenyl ether;
Examples include:

Component (B2) can be synthesized, for example, by the methods described in JP-A-7-238116 and JP-A-8-157537.

<Epoxy Group-Containing Silane Compound (C)>
Component (C) is not particularly limited and may be any of a monomer, oligomer, and polymer as long as it has at least one epoxy group in one molecule, and the component (C) used in the present composition may be one type or two or more types.
Since component (C) has an epoxy group, a coating film exhibiting the above-mentioned effects can be obtained. On the other hand, when only a compound not having an epoxy group is used, the above-mentioned desired effects are not exhibited.

As component (C), from the viewpoint of being able to easily form a coating film having superior weather resistance, etc., a compound having an epoxy group and an alkoxy group is preferred, an alkoxy group-containing silane coupling agent having one epoxy group in one molecule is more preferred, and a compound represented by the following formula is particularly preferred. The compound represented by the following formula has the function of chemically bonding the pigment described below to a coating film-forming component such as components (A), (B) and (D), and also has the effect of improving the adhesion of the coating film formed to the substrate.
X-SiR _n Y _3-n
[n is 0 or 1, X is an epoxy group, a group in which a hydrocarbon group is partially substituted with an epoxy group, or a group in which a hydrocarbon group is partially substituted with an ether bond or the like and the group is partially substituted with an epoxy group, R is an alkyl group, and Y is an alkoxy group such as a methoxy group or an ethoxy group.]

Examples of silane compounds represented by the above formula include γ-glycidoxyalkyl alkyl dialkoxysilanes such as γ-glycidoxypropyl methyl dimethoxysilane and γ-glycidoxypropyl methyl diethoxysilane; γ-glycidoxyalkyl trialkoxysilanes such as γ-glycidoxypropyl trimethoxysilane and γ-glycidoxypropyl triethoxysilane; 3,4-epoxycyclohexyl alkyl alkyl dialkoxysilanes such as 3,4-epoxycyclohexyl ethyl methyl dimethoxysilane; 3,4-epoxycyclohexyl alkyl trialkoxysilanes such as 3,4-epoxycyclohexyl ethyl trimethoxysilane, 3,4-epoxycyclohexyl ethyl triethoxysilane, and 3,4-epoxycyclohexyl ethyl tripropoxysilane, and these may be oligomers or polymers obtained by dehydration condensation.

The oligomer may be a compound having a number average molecular weight (Mn) of preferably 200 or more, more preferably 300 or more, and preferably 2,000 or less, more preferably 1,000 or less.
The polymer is preferably a compound having a Mw of 3,000 or more, more preferably 5,000 or more, and preferably 50,000 or less, more preferably 30,000 or less.

The content of component (C) (non-volatile content) in 100% by mass of the non-volatile content of the composition is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less.
When the content of component (C) is within the above range, a composition that is excellent in coating workability and has excellent drying properties that can be cured at room temperature can be easily obtained, and a coating film that is excellent in balance between weather resistance and flexibility (flexibility) can be easily obtained.

From the viewpoints that a composition having excellent drying properties and ease of application can be easily obtained, and a coating film having an excellent balance between weather resistance and flexibility (flexibility) can be easily obtained, the mass ratio of component (B) to component (C) (mass of component (B)/mass of component (C)) is preferably 0.5 or more, more preferably 1.0 or more, and preferably 10 or less, more preferably 7.5 or less.
In addition, when the following component (E) is used, it is preferable to use components (C) and (E) so that the mass ratio of component (B) to the total of components (C) and (E) (mass of component (B)/(total mass of component (C)+component (E))) is in the same range as the above ratio.

<Other ingredients>
The present composition may contain, as necessary, other components in addition to the components (A) to (C) described above, such as a silicone resin (D), an epoxy group-containing acrylic resin (E), a pigment, a dispersant, an antifoaming agent, a leveling agent, a thickener, an anti-sagging agent (anti-settling agent), a curing accelerator, a light stabilizer (light absorber), and an organic solvent, provided the effects of the present invention are not impaired.
These other components may each be used alone or in combination of two or more.
The other components may be blended in the base component or in the curing agent component.

The present composition preferably contains substantially no compound having an isocyanate group, in order to provide a coating composition that imparts less stress to the human body and the environment when applied.
When a fluororesin is used, a compound having an isocyanate group is usually used to prepare a room temperature curable coating composition. However, with the present composition, even when component (B2) is used, it is possible to obtain a room temperature curable coating composition that does not contain a compound having an isocyanate group.
The phrase "substantially free of compounds having an isocyanate group" means that the content of compounds having an isocyanate group in 100% by mass of the nonvolatile content of the composition is 0.001% by mass or less.

[Silicone resin (D)]
The component (D) is a resin having a siloxane bond, and is not particularly limited as long as it is a resin containing no epoxy groups, and may be either linear or branched.
When the present composition contains component (D), it tends to be possible to easily obtain a coating film that is more excellent in weather resistance, coating hardness and chemical resistance.

Component (D) may also have, for example, a reactive group other than an epoxy group (e.g., an amino group, a carboxy group). When a component having a reactive group is used as component (D), the reactive groups can react with each other or with the reactive groups in components (A), (B), (C) and/or (E) to form a high molecular weight component or a three-dimensional crosslinked structure, thereby improving the weather resistance and hardness of the coating film. Component (D) having such a reactive group can be blended with a curing agent.

Component (D) is preferably a resin represented by the following formula (I):

［式（Ｉ）中、Ｒ¹はそれぞれ独立に、炭素数１～８のアルキル基、炭素数６～８のアリール基、炭素数１～８のアルコキシ基、これらの基の水素原子がアミノ基および／またはカルボキシ基で置換された基、または、エポキシ基以外の反応性基である。Ｒ²はそれぞれ独立に、炭素数１～８のアルキル基、炭素数６～８のアリール基、これらの基の水素原子がアミノ基および／またはカルボキシ基で置換された基、水素原子、または、エポキシ基以外の反応性基である。また、ｎは繰り返し数を示す。］

[In formula (I), R ¹ 's are each independently an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a group in which a hydrogen atom of these groups is substituted with an amino group and/or a carboxy group, or a reactive group other than an epoxy group. R ² 's are each independently an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, a group in which a hydrogen atom of these groups is substituted with an amino group and/or a carboxy group, a hydrogen atom, or a reactive group other than an epoxy group. In addition, n represents the number of repetitions.]

Examples of the alkyl group having 1 to 8 carbon atoms in R ¹ and R ² include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group.
The aryl group having 6 to 8 carbon atoms in R ¹ and R ² may be a group having a substituent such as an alkyl group on the aromatic ring, and examples thereof include a phenyl group, a methylphenyl group, and a dimethylphenyl group.
Examples of the alkoxy group having 1 to 8 carbon atoms in R ¹ include a methoxy group, an ethoxy group, a propoxy group, and a phenoxy group.

The above R ¹ is preferably a methyl group, an ethyl group, a propyl group or a phenyl group, and the above R ² is preferably a methyl group, an ethyl group, a phenyl group or a hydrogen atom.
Examples of the reactive group other than the epoxy group in R ¹ and R ² include an amino group and a carboxy group.

The Mw of component (D) is preferably 400 or more, more preferably 500 or more, and preferably 10,000 or less, more preferably 7,000 or less, from the viewpoint that a coating film having an excellent balance of weather resistance and flexibility (flexibility) can be easily obtained.
The repeat number n is preferably selected so that the Mw of component (D) is in the above range.
Since component (D) having a Mw exceeding the upper limit of the above range has a high viscosity, in consideration of handling, dilution with an organic solvent, etc., described below, is often required to reduce the viscosity of the present composition containing such component (D). As a result, the solvent content in the present composition increases, and it may not be possible to reduce the VOC (volatile organic compounds) in the present composition.

Component (D) is preferably a resin having weather resistance and water repellency, such as methyl silicone resin or methyl phenyl silicone resin, and more preferably contains one or more structural units selected from the group consisting of the following: dimethyl siloxane unit (a1), diphenyl siloxane unit (a2), methyl phenyl siloxane unit (a3), monomethyl siloxane unit (a4), monopropyl siloxane unit (a5), and monophenyl siloxane unit (a6).

［式（ａ１）～（ａ６）中、Ｓｉ－Ｏ－における、Ｏに結合し、Ｓｉに結合していない「－」は、結合手を示し、Ｓｉ－Ｏ－は、必ずしもＳｉ－Ｏ－ＣＨ₃を示すわけではない。］

[In formulas (a1) to (a6), in Si—O—, “-” that is bonded to O and not bonded to Si represents a bond, and Si—O— does not necessarily represent Si—O—CH ₃ ]

Component (D) may be synthesized by a conventionally known synthesis method, or may be a commercially available product. Examples of commercially available products include "Dow Corning 3074 intermediate" and "Dow Corning 3055" (manufactured by DuPont Toray Specialty Materials Co., Ltd.), and "SILRES HP2000" (manufactured by Wacker Asahi Kasei Silicone Co., Ltd.).

When the composition contains component (D), the content of component (D) (non-volatile content) in 100% by mass of the non-volatile content of the composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, and particularly preferably 1.5% by mass or more, from the viewpoint of being able to easily obtain a coating film having a good balance between weather resistance and flexibility (flex resistance), and is preferably 45% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[Epoxy group-containing acrylic resin (E)]
The component (E) is a resin other than the components (A) to (C), and is not particularly limited as long as it is an acrylic resin having at least one epoxy group in one molecule.
When the present composition contains component (E), it tends to be possible to easily obtain a coating film that is superior in flexibility (flex resistance) and gloss.
When the present composition is a two-component composition containing a base agent containing components (A) and (B) and a curing agent containing component (C), it is preferable to mix component (E) in the curing agent.

Component (E) can be synthesized, for example, by (co)polymerizing an epoxy group-containing unsaturated monomer by a known method, specifically, by radical (co)polymerizing an epoxy group-containing unsaturated monomer and, if necessary, an epoxy group-free unsaturated monomer, provided that at least one of the monomers used in this (co)polymerization is a compound having a (meth)acryloyl group.
In addition, component (E) may be prepared by radically (co)polymerizing an unsaturated monomer not containing an epoxy group (provided that at least one of the monomers is a compound having a (meth)acryloyl group) and then modifying the resulting resin so that the resin has an epoxy group.
Component (E) can be synthesized by a conventional method.

Examples of the epoxy group-containing unsaturated monomer include glycidyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and allyl glycidyl ether. Among these, it is preferable to use glycidyl (meth)acrylate.
The epoxy group-containing unsaturated monomer may be used alone or in combination of two or more kinds.

The amount of the epoxy group-containing unsaturated monomer used is preferably 1% by mass or more, more preferably 2% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, based on 100% by mass of the total of the monomers used in synthesizing component (E), from the viewpoint of being able to easily obtain a coating film having excellent chemical resistance, water resistance, and coating hardness.

Examples of the non-epoxy-group-containing unsaturated monomer include the same monomers as those exemplified as the monomer (a-2) above.
Of these, it is preferable to use methyl (meth)acrylate, n-butyl (meth)acrylate, and styrene.
The epoxy group-free unsaturated monomer may be used alone or in combination of two or more kinds.

Component (E) can be synthesized, for example, by the method described in WO 2014/175246.

The Mw of component (E) is preferably 1,000 or more, more preferably 3,000 or more, and is preferably 50,000 or less, more preferably 30,000 or less, from the viewpoint of being able to easily obtain a coating film that is well-balanced in terms of flexibility (flex resistance) and coating hardness.

When the present composition contains component (E), the content of component (E) (non-volatile content) in 100% by mass of the non-volatile content of the present composition is preferably 1% by mass or more, more preferably 2% by mass or more, and is preferably 25% by mass or less, more preferably 20% by mass or less, from the viewpoint of being able to easily obtain a coating film having excellent flexibility (flex resistance) and gloss, etc.

[Pigment]
Examples of the pigment include extender pigments and color pigments, and they may be either organic or inorganic.
When the present composition is a multi-component composition containing a base agent and a curing agent, the pigment may be blended into either the base agent or the curing agent, or into both, or into a third agent other than these. However, when the present composition is a two-component composition containing a base agent containing components (A) and (B) and a curing agent containing component (C), it is preferable to blend the pigment into the base agent.

When the composition contains a pigment, the content of the pigment in 100% by mass of the nonvolatile content of the composition is preferably 20% by mass or more, more preferably 25% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, from the viewpoints of being excellent in weather resistance and flexibility (flexibility) and being able to easily form a coating film having a stress relaxation effect.

The extender pigment is not particularly limited, and any conventionally known pigment can be used, except for the color pigments described below.
Examples of the extender pigment include talc, mica, barium sulfate (including precipitated barium sulfate and elutriated barium sulfate), (potassium) feldspar, kaolin, alumina white, clay, magnesium carbonate, barium carbonate, calcium carbonate, dolomite, silica, glass flakes, and plastic flakes. Particularly preferred are talc, silica, (precipitated) barium sulfate, (potassium) feldspar, and mica.

When the composition contains an extender pigment, the content of the extender pigment in 100% by mass of the nonvolatile content of the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, from the viewpoint of being able to easily form a coating film with excellent flexibility (flex resistance), etc.

The color pigment is not particularly limited, and any conventionally known pigment can be used.
Examples of the color pigment that can be used include conventional inorganic pigments such as carbon black, titanium dioxide (titanium white), iron oxide (red oxide), yellow iron oxide, ultramarine, aluminum flakes, scaly iron oxide, and stainless steel flakes, and organic pigments such as cyanine blue and cyanine green. Titanium white, carbon black, and red oxide are particularly preferred.

When the composition contains a color pigment, the content of the color pigment in 100% by mass of the nonvolatile content of the composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less.

[Anti-sagging agent (anti-settling agent)]
As the anti-sagging agent (anti-settling agent), there can be used conventionally known agents such as stearate salts, lecithin salts, alkylsulfonates and other organic clay waxes, polyethylene wax, amide wax, hydrogenated castor oil wax, synthetic fine silica, oxidized polyethylene wax, etc., of which amide wax, synthetic fine silica, oxidized polyethylene wax, and organic clay wax are preferred.

When the composition contains an anti-sagging agent (anti-settling agent), the content of the anti-sagging agent (anti-settling agent) in 100% by mass of the non-volatile content of the composition is preferably 0.3 to 10% by mass.

[Organic solvent]
The organic solvent is not particularly limited, but examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as butyl acetate, alcohol solvents such as isopropanol and benzyl alcohol, and aliphatic hydrocarbon solvents such as mineral spirits, n-hexane, n-octane, 2,2,2-trimethylpentane, isooctane, n-nonane, cyclohexane, and methylcyclohexane.

When the composition contains an organic solvent, the content of the organic solvent in 100% by mass of the composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less.

Method for preparing the composition
The present composition can be prepared by mixing (kneading) each of the above-mentioned components.
In this mixing (kneading), the components may be added and mixed at once or may be added and mixed in several batches. Also, the components may be mixed while being heated or cooled depending on the season, environment, etc.
In the mixing (kneading), a conventionally known mixer, disperser, stirrer, etc. can be used, and examples thereof include a mixing/dispersing mill, a mortar mixer, a roll, a paint shaker, and a homogenizer.

<Coating film, substrate with coating film>
A coating film according to one embodiment of the present invention (hereinafter also referred to as "the coating film") is formed using the present composition, and a substrate with a coating film according to one embodiment of the present composition (hereinafter also referred to as "the substrate with the coating film") is a laminate comprising the present coating film and an article to be coated (substrate). Such a substrate with the present coating film can be produced, for example, by a method comprising the following steps [1] and [2].
Step [1]: A step of applying the present composition to a substrate. Step [2]: A step of drying the applied present composition to form a coating film.

The composition may be applied directly to substrates made of materials such as steel (iron, steel, ferroalloy, carbon steel, mild steel, alloy steel, etc.), non-ferrous metals (aluminum, copper, brass, zinc plating, zinc spraying, etc.), and stainless steel (SUS304, SUS410, etc.), but is usually applied to substrates having a conventionally known anticorrosive coating, antirust coating, or other primer coating, etc.

Examples of substrates made of the above-mentioned materials include ships; land structures such as bridges, tanks, plants, and steel towers; and marine structures such as port facilities, offshore buoys, pipelines, FPSOs (floating production, storage, and offloading of offshore oil and gas), FLNGs (floating offshore liquefaction of natural gas), oil drilling rigs, oil storage bases, megafloats, offshore wind power generation facilities, and tidal power generation facilities; and (large) steel structures. Among these, the material is preferably used for substrates that require weather resistance.

The dry film thickness of this coating is not particularly limited and may be selected appropriately depending on the desired application, but in order to obtain a coating film with sufficient weather resistance, it is usually 15 μm or more, preferably 25 μm or more, and usually 300 μm or less, preferably 200 μm or less.

The coating method in the step [1] is not particularly limited, and examples thereof include conventionally known methods such as spray coating, such as airless spray coating and air spray coating, and coating using a brush, roller, spatula, trowel, etc. Among these, spray coating is preferred because it can easily coat a large-area substrate such as the structure.
In such coating, it is preferable to coat the coating so that the dry film thickness of the resulting coating falls within the above range.

When applying this composition, the viscosity of the coating composition may be adjusted to an appropriate value as desired.

When applying the present composition, a coating film of the desired thickness may be formed by applying it once (one coat), or a coating film of the desired thickness may be formed by applying it twice or more (two or more coats).
Here, "coating two or more times" refers to a method in which the process of forming a dry coating film on the substrate via the above-mentioned steps [1] and [2] is carried out at least once, and then a dry coating film is formed on the dry coating film obtained via the above-mentioned steps [1] and [2].

The drying conditions in the step [2] are not particularly limited and may be appropriately set depending on the method for forming the coating film, the type of substrate, the application, the coating environment, etc., but the drying temperature, in the case of drying at room temperature, is usually 5 to 35° C., more preferably 10 to 30° C. Note that, although forced drying (e.g., 30 to 90° C.) may be performed by heating or blowing air if desired, drying and curing are usually performed under natural conditions.
The drying time varies depending on the method for drying the coating film, but in the case of drying at room temperature, it is usually 1 to 7 days, preferably 1 to 3 days.

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

[Production Example 1] <Synthesis of tertiary amino group-containing acrylic resin 1>
In the reactor, 41.5 parts by mass of xylene was charged as a solvent and heated to 110°C under a nitrogen stream. Then, a mixture of 100 parts by mass of a monomer component mixture (styrene: 38.0 parts by mass, n-butyl methacrylate: 37.0 parts by mass, n-butyl acrylate: 15.0 parts by mass, and dimethylaminoethyl methacrylate: 10.0 parts by mass) and 4.2 parts by mass of 2,2'-azobis(2-methylbutyronitrile) as an initiator was added dropwise to the reactor over 3 hours while maintaining the temperature of the reactor at 110°C. After the addition, the mixture was kept at the same temperature for 2 hours to synthesize a tertiary amino group-containing acrylic resin 1.

[Production Example 2] <Synthesis of tertiary amino group-containing acrylic resin 2>
In the reactor, 41.5 parts by mass of xylene was charged as a solvent and heated to 110 ° C. under a nitrogen stream. Then, a mixture of 100 parts by mass of a monomer component mixture (styrene: 28.0 parts by mass, n-butyl methacrylate: 29.0 parts by mass, n-butyl acrylate: 33.0 parts by mass, and dimethylaminoethyl methacrylate: 10.0 parts by mass) and 4.2 parts by mass of 2,2'-azobis (2-methylbutyronitrile) as an initiator was added dropwise to the reactor over 3 hours while maintaining the temperature of the reactor at 110 ° C. After the dropwise addition, the mixture was kept at the same temperature for 2 hours to synthesize a tertiary amino group-containing acrylic resin 2.

[Production Example 3] <Synthesis of Carboxy Group-Containing Acrylic Resin 1>
In the reactor, 29.7 parts by mass of xylene and 12.7 parts by mass of n-butanol were charged as a solvent, and the temperature was raised to 115 ° C. under a nitrogen stream. Thereafter, 100 parts by mass of a mixture of monomer components (styrene: 53.0 parts by mass, methyl methacrylate: 5.0 parts by mass, n-butyl acrylate: 35.0 parts by mass, and methacrylic acid: 7.0 parts by mass) and a mixture of 3.0 parts by mass of t-butylperoxy-2-ethylhexanoate and 0.8 parts by mass of t-butylperoxybenzoate as initiators were added dropwise to the reactor over 4 hours while maintaining the temperature of the reactor at 115 ° C. After the addition, the mixture was kept at the same temperature for 4 hours to synthesize a carboxyl group-containing acrylic resin 1.

[Production Example 4] <Synthesis of Carboxy Group-Containing Acrylic Resin 2>
In the reactor, 29.4 parts by mass of xylene and 12.6 parts by mass of n-butanol were charged as a solvent, and the temperature was raised to 115 ° C. under a nitrogen stream. Thereafter, 100 parts by mass of a mixture of monomer components (styrene: 38.0 parts by mass, methyl methacrylate: 5.0 parts by mass, n-butyl acrylate: 50.0 parts by mass, and methacrylic acid: 7.0 parts by mass) and a mixture of 3.0 parts by mass of t-butylperoxy-2-ethylhexanoate and 0.8 parts by mass of t-butylperoxybenzoate as an initiator were dropped into the reactor over 4 hours while maintaining the temperature of the reactor at 115 ° C. After dropping, the mixture was kept at the same temperature for 4 hours to synthesize a carboxyl group-containing acrylic resin 2.

[Production Example 5] <Synthesis of Carboxy Group-Containing Acrylic Resin 3>
In the reactor, 29.7 parts by mass of xylene and 12.7 parts by mass of n-butanol were charged as a solvent, and the temperature was raised to 115 ° C. under a nitrogen gas flow. Then, 100 parts by mass of a mixed solution of monomer components (styrene: 44.0 parts by mass, methyl methacrylate: 5.0 parts by mass, n-butyl acrylate: 44.0 parts by mass, and methacrylic acid: 7.0 parts by mass) and a mixed solution of 3.0 parts by mass of t-butylperoxy-2-ethylhexanoate and 0.8 parts by mass of t-butylperoxybenzoate as an initiator were dropped into the reactor over 4 hours while maintaining the temperature of the reactor at 115 ° C. After dropping, the mixture was kept at the same temperature for 4 hours to synthesize a carboxyl group-containing acrylic resin 3.

[Production Example 6] <Synthesis of epoxy group-containing acrylic resin>
In the reactor, 42.0 parts by mass of xylene was charged as a solvent, and the temperature was raised to 120°C under a nitrogen stream. Then, a mixture of 100 parts by mass of a monomer component mixture (styrene: 35.0 parts by mass, methyl methacrylate: 20.5 parts by mass, n-butyl acrylate: 29.5 parts by mass, and glycidyl methacrylate: 15.0 parts by mass) and 5.0 parts by mass of 2,2'-azobis(2-methylbutyronitrile) as an initiator was added dropwise to the reactor over 3 hours while maintaining the temperature of the reactor at 120°C. Next, 0.5 parts by mass of t-butylperoxy-2-ethylhexanoate was added to the reactor, and the mixture was kept at the same temperature for 2 hours to synthesize an epoxy group-containing acrylic resin.

<Weight average molecular weight (Mw)>
The Mw of the raw materials used in the following Examples and Comparative Examples, calculated as standard polystyrene, was measured using GPC under the following conditions.
GPC conditions: Apparatus: "Alliance 2695" (Waters)
Column: One "TSKgel Super H4000" and two "TSKgel Super H2000" columns connected together (both manufactured by Tosoh Corporation, inner diameter 6 mm x length 15 cm)
Eluent: Tetrahydrofuran 99% (Stabilized with BHT)
Flow rate: 0.6 ml/min
Detector: "RI-104" (Shodex)
Column thermostat temperature: 40°C
Standard substance: Standard polystyrene Sample preparation method: The raw materials used in the following examples and comparative examples were weighed into sample tubes and diluted approximately 100 times with tetrahydrofuran.

<Glass transition temperature (Tg)>
The glass transition temperatures (Tg) of the raw materials used in the following Examples and Comparative Examples were calculated by the Fox formula.

[Examples 1 to 10 and Comparative Examples 1 to 7]
The components constituting the base agent shown in Table 1 were placed in a plastic container in the amounts (values) shown in Table 1, and after stirring using a high-speed disperser, an appropriate amount of glass beads were added and dispersed for 1 to 2 hours using a paint shaker. The glass beads were then removed to prepare the base agent.
In addition, each component constituting the curing agent shown in Table 1 was added to a container according to the amount (numerical value) shown in Table 1, and the curing agent was prepared by thoroughly dispersing the components using a high-speed disperser.
When applying the coating, the prepared base agent and curing agent were mixed to prepare a coating composition.
The numerical values of each component in Table 1 indicate parts by mass. The explanation of each component in Table 1 is shown in Table 2.

<Flexibility>
A tinplate having dimensions of 150 mm x 10 mm x 0.3 mm (thickness) was prepared. Each of the coating compositions prepared as described above was applied to the surface of the tinplate using an air spray so that the dry film thickness was 50 μm, and the coating was dried at 50 ° C for 7 days to prepare a flex resistance test plate. Next, the obtained flex resistance test plate was subjected to a flex resistance test using a mandrel having a diameter of 10 mm in accordance with JIS K 5600-5-1: 1999 (flex resistance (cylindrical mandrel method)). The coating state of the bent part was visually observed, and the flex resistance of the coating film was evaluated according to the following evaluation criteria. The results are shown in Table 1.

(Evaluation criteria)
◯: Neither cracking occurred in the coating film nor peeling from the tin plate occurred.
x: Either cracks occurred in the coating film or peeling occurred from the tinplate.

<Weather resistance>
An alodine-treated aluminum plate having dimensions of 150 mm x 70 mm x 0.8 mm (thickness) was prepared. Each of the coating compositions prepared as described above was applied to the surface of the aluminum plate using an air spray so that the dry film thickness was 50 μm, and the coating was dried at 23 ° C for 7 days to prepare a weathering test plate. Next, the obtained weathering test plate was subjected to a weathering test for 2000 hours using a QUV accelerated weathering tester (type: QUV Accelerated Weathering Tester, UV-B313 type lamp, manufactured by Q-Lab Co., Ltd.) in accordance with JIS K 5600-7-7:2008 (accelerated weathering resistance and accelerated light resistance (xenon lamp method)).

After that, a glossmeter (model: BYK-Gardner) was used to measure the reflectance (60° gloss) of light incident at an angle of 60° from the vertical direction of the coating surface after the test, and the gloss retention rate (%) was calculated relative to the 60° gloss value of the coating film before the weather resistance test was conducted. The results are shown in Table 1. In addition, based on this gloss retention rate value, the weather resistance of the coating film was evaluated according to the following evaluation criteria.

(Evaluation criteria)
⊚: Gloss retention was 90% or more.
Good: Gloss retention was 80% or more and less than 90%.
x: Gloss retention was less than 80%.

<Coating film hardness>
A cold-rolled steel plate (JIS G 3141:2017, SPCC-SB) having dimensions of 150 mm x 10 mm x 0.3 mm (thickness) was prepared. Each coating composition prepared as described above was applied to the surface of this steel plate using an air spray so that the dry film thickness was 50 μm, and the coating was dried at 23 ° C. for 7 days to prepare a coating hardness test plate. Next, using the obtained coating hardness test plate, the hardness of the coating film was measured in accordance with JIS K 5600-5-4:1999 (scratch hardness (pencil method)), and the hardness of the coating film was evaluated according to the following evaluation criteria. The results are shown in Table 1.

(Evaluation criteria)
A: The pencil hardness was HB or higher (e.g., HB, F, H, 2H, etc.).
Δ: Pencil hardness was B to 4B.
×: The pencil hardness was 5B or less (e.g., 5B, 6B, . . . ).

<Chemical resistance>
A cold-rolled steel plate (JIS G 3141:2017, SPCC-SB) having dimensions of 150 mm x 70 mm x 0.8 mm (thickness) was prepared. Each of the coating compositions prepared as described above was applied to the surface of this steel plate so that the dry film thickness was 50 μm, and the plate was dried at 23 ° C. for 7 days to prepare a chemical resistance test plate. Next, a chemical resistance test was performed using the obtained chemical resistance test plate in accordance with JIS K 5659:2018.

Specifically, in the acid resistance test, a chemical resistance test plate was immersed in a 5 g/L aqueous sulfuric acid solution at 23° C. for 168 hours, and then removed from the aqueous solution. The coating film condition on the surface of the obtained test plate was visually observed, and the acid resistance of the coating film was evaluated according to the following evaluation criteria.
Specifically, in the alkali resistance test, a chemical resistance test plate was immersed in a saturated aqueous solution of calcium hydroxide at 23° C. for 168 hours, and then removed from the aqueous solution. The state of the coating film on the surface of the test plate obtained was visually observed, and the alkali resistance of the coating film was evaluated according to the following evaluation criteria. The results are shown in Table 1.

(Evaluation criteria)
◯: The coating film did not show any discoloration, blistering, cracking, or peeling from the steel plate.
Δ: Discoloration such as whitening occurred in the coating film, but neither blistering, cracking nor peeling from the steel plate occurred.
x: The coating film either blistered, cracked or peeled off from the steel plate.

Claims (5)

A coating composition comprising a tertiary amino group-containing acrylic resin (A), a carboxy group-containing resin (B) , an epoxy group- containing silane compound (C) and a silicone resin (D) , which is an organic solvent-based coating composition. The coating composition according to claim 1, which is room temperature curable. The coating composition according to claim 1 or 2, wherein the resin (B) contains at least one resin selected from a carboxyl group-containing acrylic resin (B1) and a carboxyl group-containing fluororesin (B2). A coating film formed from the coating composition according to any one of claims 1 to 3 . A method for producing a substrate having a coating film, comprising the following steps [1] and [2]:
[1] A step of applying the coating composition according to any one of claims 1 to 3 to a substrate. [2] A step of drying the applied coating composition to form a coating film.