JP7840738B2 - Polyurethane resin composition - Google Patents

Description

This invention relates to a polyurethane resin composition, a coating film, a coated substrate, and a method for producing the same.

Traditionally, large steel structures such as ships, bridges, tanks, plants, buoys, and underwater pipelines have been coated with various types of coatings to provide various functions, including corrosion resistance. For example, after applying an epoxy resin-based anticorrosive paint as a primer, a topcoat is applied to the resulting anticorrosive coating to enhance aesthetics and weather resistance.

A polyurethane resin composition is known as the topcoat paint mentioned above.
Such polyurethane resin compositions form a coating film through the reaction of a polyol and an isocyanate. However, since isocyanates readily react with moisture in the air to generate carbon dioxide, there is a problem that the coating film formed from polyurethane resin compositions is prone to foaming.

Regarding this issue, for example, Patent Document 1 describes that a curable composition containing a (polyurethane) prepolymer and a ketimine compound obtained from a polyoxyalkylene polyamine and a ketone compound was able to form a coating film without foaming.

Japanese Patent Publication No. 2001-151844

In recent years, regulations regarding the content of volatile organic compounds (VOCs) have become stricter from the perspective of environmental protection and workplace safety, and high-solid-type polyurethane resin compositions are desired in the polyurethane resin compositions mentioned above.
However, it was found that when a conventional polyurethane resin composition is made high-solid, significant foaming occurs when a coating film is formed from the high-solid type polyurethane resin composition obtained by this high-solid process.

Furthermore, for example, when a polyurethane resin composition is used as a topcoat paint to form a topcoat film, the topcoat film is sometimes required to be stain-resistant, that is, to have excellent stain resistance. However, conventional coatings formed from polyurethane resin compositions had room for improvement in terms of this stain resistance.

This invention has been made in view of the above, and aims to provide a polyurethane resin composition that can form a coating film with suppressed foaming and excellent stain resistance.

After diligently studying methods to solve the aforementioned problems, we discovered that a specific composition can solve these problems, and thus completed the present invention.
The following are examples of the configuration of the present invention.

[1] A main component comprising a (meth)acrylic polyol having a glass transition temperature of 20°C or higher, and a ketimine compound,
A polyurethane resin composition containing a curing agent containing a polyisocyanate compound.

[2] The polyurethane resin composition according to [1], wherein the solid content of the polyisocyanate compound relative to 100% by mass of the polyurethane resin composition is 5% by mass or more.

[3] The polyurethane resin composition according to [1] or [2], wherein the ketimine compound is a compound obtained using at least one selected from the group consisting of bis(aminomethyl)norbornane, metaxylylenediamine, and diethylenetriamine.

[4] The polyurethane resin composition according to any one of [1] to [3], wherein the (meth)acrylic polyol is a compound having a styrene skeleton.

[5] The polyurethane resin composition according to any one of [1] to [4], wherein the polyurethane resin composition is a high-solid type polyurethane resin composition with a solid content volume of 40% or more in the composition.

[6] A polyurethane resin composition according to any one of [1] to [5], for use in ships.

[7] A coating film formed from any of the polyurethane resin compositions described in [1] to [6].

[8] A coated substrate containing a substrate on which a primer film has been formed and the coating film described in [7].

[9] A method for manufacturing a coated substrate, comprising the following steps 1 to 3.
Step 1: A step of forming a primer film on a substrate. Step 2: A step of applying a polyurethane resin composition described in any of [1] to [6] onto the primer film formed in Step 1. Step 3: A step of drying the applied polyurethane resin composition to form a coating film.

According to the present invention, it is possible to provide a polyurethane resin composition, particularly a high-solid type polyurethane resin composition, that can form a coating film in which foaming is suppressed and which has excellent stain resistance.
Furthermore, when applying a polyurethane resin composition, the composition may be applied in multiple layers, resulting in a thick coating film. Conventionally, foaming was more likely to occur as the thickness of the coating film increased. However, with the polyurethane resin composition according to the present invention, foaming can be sufficiently suppressed even when a thick coating film is formed (or has been formed).

Polyurethane resin composition
The polyurethane resin composition according to the present invention (hereinafter also simply referred to as "this composition") contains a main component comprising a (meth)acrylic polyol having a glass transition temperature of 20°C or higher and a ketimine compound, and a curing agent comprising a polyisocyanate compound.

Since this composition is a multi-component composition consisting of the main component and the curing agent, it has superior storage stability compared to a one-component composition (e.g., a composition consisting of a polyurethane prepolymer and a ketimine compound), and can easily form a coating film with excellent coating performance such as weather resistance and gloss retention.
In particular, in terms of having excellent storage stability, one of the features of this composition is that the ketimine compound is not incorporated into a curing agent containing a polyisocyanate compound, but rather into a main component different from the curing agent.

The composition is not particularly limited as long as it is a multi-component composition containing the main component and the curing agent, and depending on the components used, it may be a three-component or more composition containing a third component other than the first and second components.
These main components, curing agents, and third components (hereinafter collectively referred to as "component n") are usually stored, transported, etc., in separate containers, and mixed together to form the composition before use (e.g., immediately before painting). In other words, these components n can be considered components of a kit for preparing the composition, and to put it another way, the composition can be considered a kit for a polyurethane resin composition containing the main component and curing agent.
In the present invention, the nth agent is an agent that can be stored after the preparation of these agents and before the preparation of the present composition. For example, the ketimine compound described in the following examples and the (polyurethane) prepolymer described in Patent Document 1 are usually mixed with other components and used shortly after the preparation of the ketimine compound or (polyurethane) prepolymer, and therefore do not fall under the category of the nth agent in the present invention.

This composition is prepared by mixing the aforementioned agent n, but after or during this preparation, it may be diluted depending on the coating method, etc.
Except for descriptions relating to such dilution, each description in this specification refers to the product before dilution.

From the viewpoint of environmental protection and safety in the work environment, this composition is preferably a so-called high-solid type polyurethane resin composition.
Examples of the high-solid polyurethane resin composition include compositions in which the solid content by volume is preferably 40% or more, more preferably 50% or more, and even more preferably 55% or more. There is no particular upper limit to the solid content in the composition, but it is preferably 80% or less.
The volume of solids in this composition (also known as volume solids) can be measured in accordance with ISO 3233:1998.

The solid content of this composition can be calculated as the mass percentage of the residual content of the composition, obtained by measuring the mass of the residual content (non-volatile content) and the wire after heating at a heating temperature of 125°C for 1 hour (under normal pressure) using a flat-bottomed dish weighing 1 ± 0.1 g of this composition (composition immediately after mixing with agent n), spreading it uniformly using a wire of known mass, and heating it.
Furthermore, the solid content of each component listed below (e.g., the solid content of acrylic polyol) refers to the components other than the solvent and dispersion medium in each component.
Furthermore, since the solid content of this composition is approximately equal to the sum of the solid content of each component used in its preparation, it can also be calculated from the solid content of each component used in its preparation.

The VOC content in this composition is preferably 40% by mass or less, more preferably 30% by mass or less, from the viewpoint of environmental protection and safety of the working environment. Furthermore, the VOC content in this composition is preferably 450 g/L or less, more preferably 400 g/L or less.

The VOC content in this composition can be calculated using the specific gravity and solid content of the composition, as shown in the following formulas (1) and (2). The specific gravity and solid content of the composition may be measured values as shown below, or values calculated from each component used in preparing the composition.
VOC content (mass%) = (100-solid content)/100... (1)
VOC content (g/L) = Composition specific gravity x 1000 x (100 - solid content) / 100... (2)
Composition specific gravity (g/ml): This value is calculated by filling a 100 ml specific gravity cup with the composition (the composition immediately after mixing with the nth agent) under a temperature of 23°C and measuring the mass of the composition.

This composition is suitably used on substrates such as iron and steel (iron, steel, ferroalloy, carbon steel, mild steel, alloy steel, etc.), non-ferrous metals (zinc, aluminum, copper, brass, galvanized steel, zinc sprayed steel, etc.), and stainless steel (SUS304, SUS410, etc.), and is particularly suitably used on substrates made of iron or stainless steel. Specifically, such substrates are used in ships, bridges, or other structures, and are suitably used in (large) iron or stainless steel structures such as ships, bridges, offshore structures, plants, tanks, and containers, and are further suitably used in ships, especially the deck, superstructure, and hull of ships.
This composition can be suitably used as a topcoat paint on the substrate, particularly on the substrate on which an undercoat film has been formed.

<Main ingredient>
The main component of this composition is not particularly limited as long as it contains a (meth)acrylic polyol having a glass transition temperature of 20°C or higher, and a ketimine compound.

[(meth)acrylic polyol]
The (meth)acrylic polyol is not particularly limited as long as it has a glass transition temperature (Tg) of 20°C or higher.
The (meth)acrylic polyol used in this composition may be one type or two or more types.
In addition, this composition may use any (meth)acrylic polyol with a Tg of 20°C or higher, and may also use a (meth)acrylic polyol with a Tg of less than 20°C along with a (meth)acrylic polyol with a Tg of 20°C or higher, but it is preferable that all of the (meth)acrylic polyols used in this composition are (meth)acrylic polyols with a Tg of 20°C or higher.

In this specification, (meth)acrylic means acrylic and/or methacrylic, and the following expressions such as "(meth)acrylate" also mean the same.

Examples of (meth)acrylic polyols include (meth)acrylic compounds having hydroxyl groups, either alone or as copolymers thereof; copolymers of (meth)acrylic compounds having hydroxyl groups with other compounds copolymerizable with said compounds; and modified products of these (co)polymers.

Examples of the hydroxyl group-containing (meth)acrylic compounds include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.
The (meth)acrylic compound having a hydroxyl group may be used individually or in combination of two or more types.

Other compounds include, for example, unsaturated carboxylic acid compounds such as (meth)acrylic acid, maleic acid, and fumaric acid; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and cetyl (meth)acrylate. Alkyl (meth)acrylate esters such as lauryl (meth)acrylate; fluorine-containing (meth)acrylic compounds such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, and 2-(perfluorooctyl)ethyl (meth)acrylate; isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate Examples include (meth)acrylic compounds having an alicyclic structure such as phosphate and dicyclopentenyloxyethyl (meth)acrylate; (meth)acrylic compounds having an ether linkage such as polyethylene glycol mono(meth)acrylate, methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate; benzyl (meth)acrylate; 2-ethyl-2-methyl-[1,3]-dioxolan-4-yl-methyl (meth)acrylate; dimethylaminoethyl (meth)acrylate; unsaturated carboxylic acid ester compounds such as diethyl maleate and diethyl phthalate; vinyl compounds such as styrene, α-methylstyrene, vinyl acetate, vinyl benzoate, vinyltoluene, acrylonitrile, methacrylonitrile, vinylpyridine, vinylpyrrolidone, and vinyl chloride; and (meth)acrylamide compounds such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide.
The aforementioned other compounds may be used individually or in combination of two or more.

The modified material is not particularly limited, but examples include alkyd resin-modified (meth)acrylic polyols and fatty acid-modified (meth)acrylic polyols. Among these, alkyd resin-modified (meth)acrylic polyols are preferred because they allow for easy acquisition of coatings with excellent stain resistance and gloss.
Furthermore, the aforementioned modified material refers to a resin in which the proportion of structural units derived from the modified component is less than 50% by mass.

The alkyd resin-modified acrylic resin can be obtained by conventionally known methods. Specifically, it can be synthesized using one or more of the hydroxyl group-containing (meth)acrylic compounds alone or in copolymer form with one or more alkyd resins; it can be synthesized using one or more of the hydroxyl group-containing (meth)acrylic compounds and copolymer form with one or more alkyd resins; and it can be synthesized using one or more hydroxyl group-containing (meth)acrylic compounds, one or more alkyd resins, and optionally one or more of the other compounds.
The aforementioned alkyd resin can be obtained by conventionally known methods, but it is preferable that the resin is obtained by polycondensation of a conventionally known (semi-)drying oil or (semi-)drying oil fatty acid, a conventionally known acid component, and a conventionally known polyhydric alcohol component.

As the (meth)acrylic polyol, it is preferable that the compound has a styrene skeleton because it allows for easy adjustment of the Tg of the (meth)acrylic polyol, reduces the cost of the (meth)acrylic polyol, and allows for easy acquisition of a coating with excellent coating strength. Furthermore, as the compound having a styrene skeleton, a (meth)acrylic polyol having a styrene skeleton and an alkyd resin modified product of a (meth)acrylic polyol having a styrene skeleton are preferred.

The Tg of the (meth)acrylic polyol is preferably 20°C or higher, more preferably 25°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher, from the viewpoint of easily obtaining a coating film with excellent stain resistance and coating hardness. The upper limit of the Tg is preferably 80°C or lower, more preferably 70°C or lower, from the viewpoint of easily obtaining a coating film with excellent crack resistance.

In this specification, Tg can be approximately calculated using the following formula by Fox, as described in Fox T. G., Bull. Am. Physics Soc. 1, 3, p. 123 (1956).

[In the formula, _Xn is the mass fraction (mass%/100) of a certain monomer n relative to 100% by mass of the total monomers used in the synthesis of the (meth)acrylic polyol, and _Tgn is the glass transition temperature (Kelvin) of the homopolymer of the monomer n.]

Tg _n can be referenced, for example, from the values listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975). According to this handbook, for example, the Tg of polystyrene is 373K, the Tg of poly(methyl methacrylate) is 378K, the Tg of poly(butyl methacrylate) is 297K, the Tg of polyhydroxyethyl methacrylate is 328K, and the Tg of polymethacrylic acid is 458K.

The weight-average molecular weight (Mw) of (meth)acrylic polyol, as measured by gel permeation chromatography (GPC), is preferably 3,000 to 40,000, more preferably 4,000 to 25,000, from the standpoint that a coating film with excellent weather resistance can be easily obtained.
Furthermore, when this composition is a high-solid type polyurethane resin composition, it is preferable to use a low molecular weight (meth)acrylic polyol. The Mw of the (meth)acrylic polyol used in such a high-solid type polyurethane resin composition is preferably 22,000 or less, and more preferably 4,000 to 18,000.

The hydroxyl value of the (meth)acrylic polyol is preferably 30 to 200 mg KOH/g, and more preferably 40 to 150 mg KOH/g, from the viewpoint that a coating film with excellent weather resistance and stain resistance can be easily obtained.
Furthermore, when this composition is a high-solid type polyurethane resin composition, it is preferable to use a (meth)acrylic polyol with a high hydroxyl value. The hydroxyl value of the (meth)acrylic polyol used in such a high-solid type polyurethane resin composition is preferably 40 mg KOH/g or more, and more preferably 45 to 100 mg KOH/g.

The hydroxyl value mentioned above is a value measured by the following method.
Accurately weigh 2 g of (meth)acrylic polyol into a round-bottom flask, add 5 ml of acetylation reagent (a solution of 25 g of acetic anhydride dissolved in pyridine to a volume of 100 ml), and heat in a glycerin bath at 95-100°C for 1 hour. Then remove the flask from the glycerin bath, let it cool, add 1 ml of water and shake. Heat the flask again in a glycerin bath for 10 minutes, let it cool, and add 5 ml of ethanol. Next, add phenolphthalein-ethanol solution and titrate with 0.5 M (N/2) potassium hydroxide-ethanol solution. The titration endpoint is reached when the purple color does not disappear for 30 seconds, and the amount of N/2 potassium hydroxide-ethanol solution used in this test is determined.
In parallel with the main test, a blank test was conducted in the same manner except that (meth)acrylic polyol was not used, and the amount of N/2 potassium hydroxide-ethanol solution used in the blank test was confirmed.
The hydroxyl value A (mgKOH/g) of (meth)acrylic polyol is calculated using the following formula.
A=[{(B-C)×f×28.05}/S]+D
[S: Amount of (meth)acrylic polyol used in weighed tests (g), B: Amount of N/2 potassium hydroxide-ethanol solution used in blank tests (ml), C: Amount of N/2 potassium hydroxide-ethanol solution used in the main test (ml), f: Factor of the N/2 potassium hydroxide-ethanol solution, D: Acid value (mgKOH/g)]

The acid value is measured as follows.
Accurately weigh 1 to 5 g of (meth)acrylic polyol into a conical beaker, add 30 to 50 ml of a toluene/ethanol = 7/3 (volume ratio) mixed solution to dissolve the (meth)acrylic polyol, add 2 drops of phenolphthalein-ethanol solution as an indicator, and titrate with N/10 potassium hydroxide-ethanol solution. The titration endpoint is reached when the red color of the solution does not disappear for 30 seconds.
The acid value D (mgKOH/g) of (meth)acrylic polyol is calculated using the following formula.
D=(B×f×5.61)/S
[S: Amount of (meth)acrylic polyol used (g), B: Amount of N/10 potassium hydroxide-ethanol solution used (ml), f: Factor of N/10 potassium hydroxide-ethanol solution]

The (meth)acrylic polyol content in this composition is preferably 10 to 70% by mass, more preferably 20 to 50% by mass, based on 100% by mass of the solid content of this composition, in order to easily obtain a coating film with a good balance of foam resistance, stain resistance, and weather resistance.

[Ketimine compounds]
The ketimine compound is not particularly limited, but specifically, examples include reaction products of a primary or secondary amino group-containing compound with a ketone compound.
The ketimine compound used in this composition may be one type or two or more types.

The amino group-containing compound is preferably a primary amino group-containing compound, and more preferably a compound having two or more amino groups.
The amino group-containing compound may be an amine compound, or a modified amine compound obtained by modifying the amine compound (e.g., polyamidation, epoxy adductation, Mannichation, alkylphenolation).
The amino group-containing compound may be used individually or in combination of two or more types.

Examples of the amine compounds include aliphatic amines, alicyclic amines, aromatic amines, heterocyclic amines, polyoxyalkylene polyamines, and aminoalkoxysilanes.

Specific examples of the aliphatic amines include alkylene polyamines such as methylenediamine, ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, and trimethylhexamethylenediamine; diethylenetriamine [DETA], dipropylenetriamine, triethylenetetramine, tripropylenetetramine, and tetraethylene Examples include polyalkylene polyamines such as lenpentamine, tetrapropylenepentamine, pentaethylenehexamine, nonaethylenedecamine, bis(hexamethylene)triamine, and triethylene-bis(trimethylene)hexamine; and alkylaminoalkylamines such as dimethylaminoethylamine, diethylaminoethylamine, dibutylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine, dipropylaminopropylamine, dibutylaminopropylamine, and dimethylaminobutylamine.

Other aliphatic amines include, for example, tetra(aminomethyl)methane, tetrakis(2-aminoethylaminomethyl)methane, 1,3-bis(2'-aminoethylamino)propane, tris(2-aminoethyl)amine, bis(cyanoethyl)diethylenetriamine, bis(aminomethyl)cyclohexane, isophoronediamine (IPDA), mensendiamine, bis(aminomethyl)norbornane [norbornanediamine, NBDA], o-xylylenediamine, metaxylylenediamine [MXDA], p-xylylenediamine, bis(aminomethyl)naphthalene, bis(aminoethyl)naphthalene, 1,4-bis(3-aminopropyl)piperazine, 1-(2'-aminoethylpiperazine), and 1-[2'-(2''-aminoethylamino)ethyl]piperazine.

Specific examples of the aforementioned alicyclic amines include cyclohexanediamine, diaminodicyclohexylmethane (particularly 4,4'-methylenebiscyclohexylamine), 4,4'-isopropylidenebiscyclohexylamine, norbornanediamine, and 2,4-di(4-aminocyclohexylmethyl)aniline.

Specific examples of the aforementioned aromatic amines include phenylenediamine, naphthalenediamine, diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, diaminodiethylphenylmethane, 2,4'-diaminobiphenyl, 2,3'-dimethyl-4,4'-diaminobiphenyl, and 3,3'-dimethoxy-4,4'-diaminobiphenyl.

Specific examples of the aforementioned heterocyclic amines include 1,4-diazacycloheptane, 1,11-diazacycloeicosane, and 1,15-diazacyclooctacosane.

Specific examples of the aminoalkoxysilanes mentioned above include 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, and 3-(2-aminoethylamino)propylmethyldiethoxysilane.

Specific examples of the aforementioned polyoxyalkylene polyamines include polyoxyethylene polyamines, polyoxypropylene polyamines, polyoxytetramethylene polyamines, and polyoxyethylene polyoxypropylene polyamines (e.g., diethylene glycol bis(3-aminopropyl) ether).

Among these amine compounds, bis(aminomethyl)norbornane, metaxylylenediamine, and diethylenetriamine are preferred because they allow for easy acquisition of coatings with excellent foam resistance and stain resistance, and diethylenetriamine is more preferred because it allows for easy acquisition of coatings with remarkably excellent foam resistance.

Examples of the ketone compounds include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl tert-butyl ketone, ethyl butyl ketone, dimethyl ketone, diethyl ketone, dipropyl ketone, diisopropyl ketone, dibutyl ketone, methyl amyl ketone, methyl hexyl ketone, methylcyclohexyl ketone, methyl phenyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and cycloheptanone. Among these, methyl isobutyl ketone and methyl ethyl ketone are preferred.
One ketone compound may be used, or two or more may be used.

The ketimine compound is preferably obtained by reacting the ketone compound with one amino group of the amino group-containing compound in an amount such that the number of carbonyl groups in the ketone compound is 0.5 to 1.0.

The ketimine compound content in this composition is preferably 0.2 to 2% by mass, more preferably 0.4 to 1% by mass, based on 100% by mass of the solid content of the composition, in order to easily obtain a coating film with excellent foam resistance.

[Additives]
The main component may, as necessary and insofar as it does not impair the effects of the present invention, contain other components besides (meth)acrylic polyol and ketimine compounds, such as conventionally known additives like pigments, thixotropes (anti-sagging and anti-settling agents), dispersants, light stabilizers, leveling agents, defoamers, thickeners, film-forming aids, plasticizers, surfactants, organic solvents, antifungal agents, preservatives, UV absorbers, and pH adjusters.
Each of these additives may be used individually or in combination of two or more types.

Pigments The pigments mentioned above include conventionally known coloring pigments and extender pigments. Examples of coloring pigments include inorganic pigments such as carbon black, titanium dioxide, red iron oxide, iron oxide, iron hydroxide, and ultramarine; and organic pigments such as phthalocyanine blue and phthalocyanine green. Examples of extender pigments include barium sulfate (including precipitated barium sulfate and extirpated barium sulfate), calcium carbonate, potassium feldspar, kaolin, clay, talc, mica, bentonite, magnesium carbonate, and silica.

When this composition contains a pigment, its content is preferably 20 to 70% by mass, more preferably 40 to 60% by mass, relative to 100% by mass of the solid content of this composition, in order to easily obtain a coating film that is well balanced in terms of flexibility and adhesion to the undercoat film.

When this composition contains a pigment, the pigment volume concentration (PVC) in this composition is preferably 5 to 35%, more preferably 15 to 25%, from the viewpoint of easily obtaining a coating film that has a good balance of flexibility and adhesion to the undercoat film.

The aforementioned PVC refers to the total volume concentration of pigments relative to the volume of solids in this composition. Specifically, PVC can be calculated using the following formula.
PVC [%] = Total volume of all pigments in this composition × 100 / Volume of solids in this composition

The volume of solids in the composition can be calculated from the mass and true density of the solids in the composition. The mass and true density of the solids may be measured values or values calculated from the raw materials used.
The volume of the pigment can be calculated from the mass and true density of the pigment used. The mass and true density of the pigment may be measured values or values calculated from the raw materials used. For example, it can be calculated by separating the pigment from other components from the solid content of the composition and measuring the mass and true density of the separated pigment.

• Switotherapeutic agents Examples of switotherapeutic agents include organic clay salts such as stearate salts, lecithin salts, and alkyl sulfonates of Al, Ca, and Zn; clays such as bentonite clay and hectorite clay; and organically modified products of these clays (e.g., organically modified hectorite clay); oxidized polyethylene waxes; ethylene-vinyl acetate waxes; polyamide waxes; hydrogenated castor oil waxes; and synthetic fine silica. Among these, organic switotherapeutic agents such as organically modified hectorite clay are preferred because they can easily form coating films with excellent smoothness.

If this composition contains a thixotrope, its content is preferably 0.4 to 2.0% by mass, more preferably 0.8 to 1.6% by mass, relative to 100% by mass of the solid content of this composition, in order to easily obtain a coating film with excellent smoothness.

• Dispersant The dispersant is not particularly limited, but examples include various dispersants such as copolymers having compatible chains, such as fatty acids, polyaminos, polyethers, polyesters, polypolyurethanes, and polyacrylates, which have pigment-adsorbing groups (pigment affinity groups) such as carboxyl groups, phosphate groups, amino groups, groups of these salts, and ammonium bases.

If this composition contains a dispersant, its content is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.3% by mass, relative to 100% by mass of the solid content of this composition, in order to easily obtain a coating film with excellent smoothness.

• Light stabilizer Examples of the light stabilizer include hindered amine-based light stabilizers.
Examples of the hindered amine-based light stabilizers include bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, and bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl) decandioate ester.

If this composition contains a light stabilizer, its content is preferably 0.1 to 2% by mass, more preferably 0.3 to 1.0% by mass, based on 100% by mass of the solid content of this composition, in order to easily obtain a coating film with excellent weather resistance.

• Leveling agent: It is preferable to include the leveling agent in this composition.
The leveling agent is not particularly limited, but examples include various leveling agents such as fluorine-based, acrylic-based, and silicone-based agents.

If this composition contains a leveling agent, its content is preferably 0.01 to 1.0% by mass, more preferably 0.05 to 0.3% by mass, relative to 100% by mass of the solid content of this composition. This is because it improves the paint repellency when the composition is applied, enhances wettability to the coated surface (e.g., substrate), and facilitates the acquisition of a coating with a uniform film thickness.

- Defoaming agent As the defoaming agent, various conventionally known defoaming agents such as polymer-based, acrylic-based, silicone-based, mineral oil-based, and olefin-based agents can be used, but polymer-based and olefin-based defoaming agents are preferred.

If this composition contains an antifoaming agent, its content is preferably 0.01 to 2.0% by mass, more preferably 0.1 to 1.0% by mass, relative to 100% by mass of the solid content of the composition, in order to suppress foam generation during the manufacturing and painting of the composition, and to break any foam that has already been generated in the composition.

• Organic solvents This composition may contain organic solvents, and is preferably a so-called solvent-based paint (different from water-based paints).
Examples of the aforementioned organic solvents include conventionally known organic solvents such as aromatic, aliphatic, ketone, ether, ester, and alcohol-based solvents. Specifically, these include aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as mineral spirits and cyclohexane; ketone solvents such as methyl isobutyl ketone and cyclohexanone; ether or ester solvents such as butyl acetate, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate; and alcohol-based solvents such as n-butyl alcohol and isopropyl alcohol.

The amount of organic solvent used is preferably such that the VOC content in the composition falls within the aforementioned range.

<Hardening agent>
The curing agent in this composition is not particularly limited as long as it contains a polyisocyanate compound.

[Polyisocyanate compounds]
The polyisocyanate compound is not particularly limited and includes conventionally known polyisocyanate compounds, specifically, linear hydrocarbons containing isocyanate groups such as tetramethylene diisocyanate and hexamethylene diisocyanate, branched hydrocarbons containing isocyanate groups such as 2,2,4-trimethylhexamethylene diisocyanate, and isocyanate group-containing compounds such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated toluene diisocyanate. Examples include cyclic hydrocarbons, diisocyanate group-containing aromatic hydrocarbons such as p-phenylenediisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, 1,3-xylenediisocyanate, dianisidine diisocyanate, tetramethylxylenediisocyanate, 1,5-naphthalenediisocyanate, tolylenediisocyanate, and 4,4-diphenylmethanediisocyanate; and dimers or trimers of the aforementioned isocyanates (biuret modified, isocyanurate modified).
Among these, hexamethylene diisocyanate, isophorone diisocyanate, and isocyanurate-modified forms of these isocyanates are preferred as polyisocyanate compounds.
The polyisocyanate compound used in this composition may be one type or two or more types.

The polyisocyanate compound content in this composition is preferably 5% by mass or more, more preferably 5.0 to 18.0% by mass, and even more preferably 8.0 to 15.0% by mass, based on 100% by mass of the solid content of this composition, in order to easily obtain a coating film that is well balanced in terms of foam resistance, stain resistance, and weather resistance.
Furthermore, when this composition is a high-solids polyurethane resin composition, it is preferable to use a (meth)acrylic polyol with a low molecular weight and high hydroxyl value. When using such a (meth)acrylic polyol, it tends to be necessary to use a large amount of polyisocyanate compound so that the polyisocyanate compound reacts sufficiently with the (meth)acrylic polyol. In such cases, the amount of polyisocyanate compound used is preferably 8.0% by mass or more, more preferably 9.0 to 15.0% by mass, based on 100% by mass of the solids content of this composition.
Thus, when using a large amount of polyisocyanate compound, conventional compositions exhibited significant foaming. However, with this composition, even when using a large amount of polyisocyanate compound, a coating film with suppressed foaming can be easily obtained.

Furthermore, the amount of polyisocyanate compound in this composition is preferably such that the reaction ratio represented by the following formula is 0.7 to 1.5, more preferably 0.9 to 1.3, in order to easily obtain a coating film that is well balanced in terms of foam resistance, stain resistance, and weather resistance.
Reaction ratio = NCO equivalent of polyisocyanate compound / (OH equivalent of polyol compound + active hydrogen equivalent of ketimine compound)

[Additives]
The curing agent may, as necessary and insofar as it does not impair the effects of the present invention, contain other components besides the polyisocyanate compound, such as conventionally known additives like pigments, thixotropes (anti-sagging and anti-settling agents), dispersants, light stabilizers, leveling agents, defoamers, thickeners, film-forming aids, plasticizers, surfactants, organic solvents, antifungal agents, preservatives, ultraviolet absorbers, and pH adjusters.
Each of these additives may be used individually or in combination of two or more types.
Specific examples of these additives are the same as those described in the section on the main ingredient.

<Method for preparing this composition>
The main agent and hardener can be prepared by mixing (kneading) the components to be incorporated into these agents. During this mixing (kneading), the components may be added and mixed all at once, or they may be added and mixed in multiple stages.
This composition can be prepared by mixing (kneading) these main components, a curing agent, and other agents (e.g., a third component) as needed.
During the mixing (kneading) process, conventionally known devices such as mixers, dispersers, and agitators can be used. Examples of such devices include dispersers, mixing/dispersing mills, mortar mixers, rolls, paint shakers, and homogenizers. Furthermore, the mixing (kneading) process may be carried out with heating, cooling, etc., depending on the season, environment, etc.

≪Coating films, coated substrates≫
The coating film according to the present invention (hereinafter also referred to as "the coating film") is formed using the composition described above, and the coated substrate according to the present invention (hereinafter also referred to as "the coated substrate") is a laminate having the coating film and the substrate.

The film thickness of this coating is typically 20 to 200 μm, preferably 50 to 100 μm, based on dry thickness.

The material of the base material is not particularly limited and includes, for example, iron and steel (iron, steel, ferroalloy, carbon steel, mild steel, alloy steel, etc.), non-ferrous metals (zinc, aluminum, copper, brass, galvanized, zinc sprayed, etc.), and stainless steel (SUS304, SUS410, etc.), with iron and steel or stainless steel being preferred.
The base material is preferably a ship, a bridge, or other structure, more preferably a (large) steel or stainless steel structure such as a ship, bridge, offshore structure, plant, tank, or container, even more preferably a ship, and particularly preferably the deck, superstructure, or hull of a ship.

The aforementioned substrate may have an undercoat coating for the purpose of improving adhesion to the substrate and corrosion resistance, and it is preferable that it has such an undercoat coating. In other words, it is preferable that the substrate with the coating coating is a substrate with a coating coating that includes a substrate on which an undercoat coating has been formed and the coating coating itself.
In this specification, the term "undercoat" refers to a coating film provided between the main coating film and the substrate (a coating film provided beneath the main coating film), and includes not only known undercoat films (primer coatings) in the narrow sense, but also known coating films referred to as so-called intermediate coating films.
The aforementioned undercoat film may consist of one layer or two or more layers.

The aforementioned primer coating film can be a coating film formed from various primer compositions such as epoxy resin-based or inorganic zinc-based primers. The aforementioned intermediate coating film can be a coating film formed from various intermediate coating paint compositions such as epoxy resin-based or polyurethane resin-based primers.

The thickness of the aforementioned undercoat film is typically 50 to 500 μm, preferably 100 to 350 μm, based on its dry thickness.

The aforementioned substrate may be a substrate that has undergone pretreatment such as cleaning or blasting to remove rust, dirt, paint (old paint film), etc., adhering to the substrate, or a substrate on which the aforementioned undercoat film has been formed after such pretreatment.

A coated substrate containing the substrate on which the aforementioned undercoat film is formed and the main coating film can be manufactured, for example, by a method including the following steps 1 to 3.
Step 1: A step of forming a primer film on the substrate. Step 2: A step of applying the composition onto the primer film formed in Step 1. Step 3: A step of drying the applied composition to form the main coating film.

Examples of painting methods in steps 1 and 2 include brush painting, air spray painting, airless spray painting, and roll coater painting. Spray painting is preferred because it offers excellent workability and productivity, allows for easy painting of large areas of substrates, and better demonstrates the effects of the present invention.
The aforementioned undercoat film and main coating film may be formed in a single coat, or they may be formed in two or more coats.

The conditions for forming the aforementioned undercoat film and the conditions for step 3 include, for example, a drying time of typically 1 to 30 days, preferably 1 to 7 days, and a drying temperature of typically 5 to 40°C, preferably 10 to 30°C, or even room temperature.

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

[Synthesis Example 1] <Synthesis of Ketimine Compound 1>
103.0 parts by mass of diethylenetriamine and 400.0 parts by mass of methyl isobutyl ketone were charged into a reactor, and the reaction was continued at 105-135°C for 14 hours under a nitrogen stream, while removing the water produced by azeotrope. Next, the temperature was raised to 190°C while removing residual ketone, and when the temperature reached 190°C, the pressure in the reactor was reduced to 190 mmHg, and the water produced during the reaction was recovered under reduced pressure. After that, the temperature was lowered to 80°C, then 180.2 parts by mass of phenylglycidyl ether was added, and the mixture was kept warm at the same temperature for 1 hour, then the temperature was raised to 100°C and kept warm for 2 hours. After the 2 hours of warming, 2.7 parts by mass of trimethyl orthoformate was added as a dehydrating agent to obtain ketimine compound 1.

[Synthesis Example 2] <Synthesis of Ketimine Compound 2>
136.0 parts by mass of metaxylylenediamine and 400.0 parts by mass of methyl isobutyl ketone were charged into a reactor, and the reaction was continued at 100-135°C for 16 hours under a nitrogen stream, while removing the water produced by azeotrope. Next, the temperature was raised to 190°C while removing residual ketone, and when the temperature reached 190°C, the pressure in the reactor was reduced to 40 mmHg, and the water produced during the reaction was recovered under reduced pressure. After that, the temperature was lowered to 80°C, then 23.2 parts by mass of phenylglycidyl ether was added, and the mixture was kept warm at the same temperature for 1 hour, then the temperature was raised to 100°C and kept warm for 2 hours. After the 2 hours of warming, 2.9 parts by mass of trimethyl orthoformate was added as a dehydrating agent to obtain ketimine compound 2.

[Synthesis Example 3] <Synthesis of Ketimine Compound 3>
154.0 parts by mass of bis(aminomethyl)norbornane and 400.0 parts by mass of methyl isobutyl ketone were charged into a reactor, and the reaction was continued at 100-135°C for 18 hours under a nitrogen stream, while removing the water produced by azeotrope. Next, the temperature was raised to 190°C while removing residual ketone, and when the temperature reached 190°C, the pressure in the reactor was reduced to 40 mmHg, and the water produced during the reaction was recovered under reduced pressure. After that, the temperature was lowered to 80°C, then 13.7 parts by mass of phenylglycidyl ether was added, and the mixture was kept warm at the same temperature for 1 hour, then the temperature was raised to 100°C and kept warm for 2 hours. After the 2 hours of warming, 3.2 parts by mass of trimethyl orthoformate was added as a dehydrating agent to obtain ketimine compound 3.

[Example 1]
The main component was prepared by dispersing 140 parts by mass of acrylic polyol, 10.5 parts by mass of ketimine compound, 28 parts by mass of titanium dioxide, 13 parts by mass of barium sulfate, 1 part by mass of thixotrope, 0.3 parts by mass of dispersant, 0.5 parts by mass of light stabilizer, 0.2 parts by mass of leveling agent, 0.5 parts by mass of defoaming agent, 8 parts by mass of butyl acetate, and 8 parts by mass of xylene using a paint shaker.
A curing agent was prepared by stirring 90 parts by mass of a polyisocyanate compound and 10 parts by mass of butyl acetate.
A polyurethane resin composition was prepared by mixing 92% by mass of the prepared main component with 8% by mass of the curing agent and degassing the mixture.

[Examples 2-9 and Comparative Examples 1-4]
The main component and hardener were prepared in the same manner as in Example 1, except that the types and amounts of each component constituting the main component and hardener were changed as shown in Table 1 below.
The prepared main component and curing agent were mixed to the mixing ratio (mass%) shown in Table 1, and then degassed to prepare a polyurethane resin composition.
Table 2 provides a description of each component listed in Table 1.

<Foam resistance>
Test plates were prepared by coating a base material (tinplate) with the polyurethane resin compositions prepared in the examples and comparative examples, respectively, using an applicator (gap of 350 μm).
Immediately after coating with the polyurethane resin composition, the prepared test plates were placed in a constant temperature and humidity chamber at 23°C/50% RH. After 24 hours in the chamber, the blistering of the coating on the surface of the test plates was visually inspected and evaluated according to the ASTM evaluation criteria. The results are shown in Table 1.

The ASTM evaluation criteria are indicated in order of blister size from largest to smallest: 2, 4, 6, and 8. "F" indicates a "Few" blister quantity, "M" indicates a "Medium" quantity, "MD" indicates a "Medium Dense" quantity, and "D" indicates a "Dense" quantity. The blister size and quantity are indicated by numbers and letters (for example, a blister size of 8 with a quantity of "Few" would be "8F"). "10" indicates no blister was detected.

<Stain resistance>
Using an applicator (gap of 0.3 mm), the polyurethane resin compositions prepared in Examples 1-5 and 7-9 were applied to a base material (tinplate), respectively, and dried at room temperature for 7 days. After that, the materials were strongly dried at 50°C for 24 hours and then returned to room temperature to prepare test plates.
Half of the main surface (the surface with the largest area) of the prepared test plate was coated with a carbon black aqueous solution (carbon black concentration 5% by mass), dried at 50°C for 1 hour, and then the carbon black was washed off with running water.
The L-value (L0) of the main surface of the test plate that was not coated with the carbon black aqueous solution and the L-value (L1) of the area coated with the carbon black aqueous solution and then washed off with running water were measured using a Spectrophotometer CM-3700A (light source: C, field of view: 2°) manufactured by Konica Minolta Japan, Inc., and the difference in L-values (ΔL = L1 - L0) was calculated. The results are shown in Table 3.

Claims (8)

A main component comprising a (meth)acrylic polyol having a glass transition temperature of 20°C or higher, and a ketimine compound,
It contains a curing agent containing a polyisocyanate compound ,
The ketimine compound is a compound obtained using at least one selected from the group consisting of bis(aminomethyl)norbornane, metaxylylenediamine, and diethylenetriamine.
Polyurethane resin composition. The polyurethane resin composition according to claim 1, wherein the solid content of the polyisocyanate compound relative to 100% by mass of the polyurethane resin composition is 5% by mass or more. The polyurethane resin composition according to claim 1 or 2 , wherein the (meth)acrylic polyol is a compound having a styrene skeleton. The polyurethane resin composition according to any one of claims 1 to 3 , wherein the polyurethane resin composition is a high-solid type polyurethane resin composition in which the volume of solids in the composition is 40% or more. A polyurethane resin composition according to any one of claims 1 to 4 , for use in ships. A coating film formed from the polyurethane resin composition according to any one of claims 1 to 5 . A coated substrate containing a substrate on which an undercoat film has been formed and the coating film according to claim 6 . A method for manufacturing a coated substrate, comprising the following steps 1 to 3.
Step 1: A step of forming an undercoat film on a substrate. Step 2: A step of applying the polyurethane resin composition described in any one of claims 1 to 5 onto the undercoat film formed in Step 1. Step 3: A step of drying the applied polyurethane resin composition to form a coating film.