JP2023137097A - Thermosetting coating composition, substrate with cured coating layer, and method for producing the same - Google Patents

Abstract

To provide a thermosetting coating composition that can form a cured coating layer with excellent transparency, substrate adhesion, long-term hydrophilicity, and long-term condensation resistance.SOLUTION: A thermosetting coating composition includes (A) amino resin and (B) colloidal silicas. The content of (A) amino resin is 45 pts.mass or more and 100 pts.mass or less relative to 100 pts.mass of the solid content of the resin component. The content of the (B) colloidal silicas is 150 pts.mass or more relative to 100 pts.mass of the solid content of the resin component.SELECTED DRAWING: None

Description

The present invention relates to thermosetting coating compositions. The present invention also relates to a cured coating formed from a thermosetting coating composition, a substrate with the cured coating, and a method for producing the substrate with the cured coating.

Conventionally, it has been carried out to impart hydrophilicity to cured coating films of industrial products. For example, in the case of industrial products such as automobile parts and plumbing products for bathrooms, kitchens, etc., it is necessary to maintain hydrophilicity for a long period of about 3 to 10 years. Common methods for imparting hydrophilic properties to cured coatings of industrial products include adding surfactants to curable compositions and adding compounds with organic hydrophilic groups such as polyethylene glycol. . However, in the case of the method of blending a non-reactive surfactant to make it hydrophilic, there was a problem that when the cured coating was washed with water, the non-reactive surfactant was washed away and the hydrophilicity could not be maintained. . In addition, in the case of a method of blending polyethylene glycol or the like to make it hydrophilic, there is a problem that once the water absorption performance of polyethylene glycol or the like reaches its upper limit, hydrophilicity cannot be maintained. That is, with conventional methods, it has been difficult to maintain hydrophilicity in industrial products for a long period of time.

Conventionally, in order to improve hydrophilicity, (A) fine silica particles with a chain structure, (B) an organic compound having a (meth)acryloyl group or a (meth)acrylamide group, and (C) a photopolymerization initiator have been used. It has been proposed to form a cured coating film using an active energy ray-curable organic-inorganic hybrid resin composition (see Patent Document 1). In addition, in order to improve hydrophilicity, (A) colloidal silica sol, (B) an acrylic polymer containing active hydrogen and having a weight average molecular weight (Mw) of 5,000 to 200,000, and (C) a reactive silane coupling agent. , (D) a curing agent for the acrylic polymer (B), and a hydrophilic coating material in which the contents of components (A) to (C) are adjusted has been proposed (see Patent Document 2).

Japanese Patent Application Publication No. 2004-083846 International Publication No. 2009/044912

The present inventors discovered that even if the active energy ray-curable organic-inorganic hybrid resin composition described in Patent Document 1 was used, the silica particles would flow out of the cured coating after a long period of time, resulting in long-term hydrophilicity. We found that it is difficult to maintain sexuality. In addition, since the curing mechanism of the active energy ray-curable organic-inorganic hybrid resin composition described in Patent Document 1 is an ultraviolet curing system, ultraviolet irradiation equipment is required, and it is difficult to coat objects with complex surface shapes. There was also the problem that it could not be applied. Furthermore, the present inventors have found that even if the hydrophilic coating material described in Patent Document 2 is composed of only a polyol resin, it is difficult to maintain hydrophilicity for a long period of time.

The present invention was made in view of the above-mentioned background technology and problems, and its purpose is to form a cured coating film that has excellent transparency, substrate adhesion, long-term hydrophilicity, and long-term dew condensation resistance. The object of the present invention is to provide a thermosetting coating composition that can be used.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies and found that the present inventors included (A) amino resin and (B) colloidal silica, and adjusted the content of (A) amino resin and (B) colloidal silica. It has been found that the above problems can be solved by using a thermosetting coating composition. The present invention was completed based on this knowledge.

That is, according to the present invention, the following inventions are provided.
[1] A thermosetting coating composition comprising (A) an amino resin and (B) colloidal silica,
The content of the amino resin (A) is 45 parts by mass or more and 100 parts by mass or less based on 100 parts by mass of the solid content of the resin component,
A thermosetting coating composition in which the content of the colloidal silica (B) is 150 parts by mass or more based on 100 parts by mass of the resin component in terms of solid content.
[2] The thermosetting coating composition according to [1], wherein the colloidal silica (B) contains chain silica.
[3] The thermosetting coating composition according to [1] or [2], wherein the thermosetting coating composition contains (C) a polyol resin in addition to the (A) amino resin as the resin component.
[4] The thermosetting coating composition according to [3], wherein the polyol resin (C) contains a (meth)acrylic polyol.
[5] The thermosetting coating composition according to any one of [1] to [4], wherein the amino resin (A) contains a melamine resin.
[6] A cured coating film formed from the thermosetting coating composition according to any one of [1] to [5].
[7] A substrate with a cured coating film, which has a cured coating film formed from the thermosetting coating composition according to any one of [1] to [5] on at least a portion of the substrate surface.
[8] A coating step of applying the thermosetting coating composition according to any one of [1] to [5] to at least one surface of a substrate;
After the coating step, a curing step of curing the thermosetting coating composition by heating to form a cured coating film;
A method for producing a substrate with a cured coating film, comprising:

According to the present invention, it is possible to provide a thermosetting coating composition capable of forming a cured coating film having excellent transparency, substrate adhesion, long-term hydrophilicity, and long-term dew condensation resistance. According to the present invention, it is also possible to provide a cured coating formed from such a thermosetting coating composition, a substrate with the cured coating, and a method for producing the substrate with the cured coating. .

The present invention will be explained in more detail below.
In addition, in this specification, "solid content" refers to a thermosetting coating composition excluding volatile components such as organic solvents, and indicates components that constitute a cured coating film when cured.

<Thermosetting coating composition>
The thermosetting coating composition according to the present invention contains (A) an amino resin and (B) colloidal silica. The thermosetting coating composition may further contain (C) a polyol resin in addition to the (A) amino resin as a resin component. In the present invention, the thermosetting coating composition contains (A) amino resin and (B) colloidal silica, and by adjusting the content of (A) amino resin and (B) colloidal silica, transparency can be improved. It is possible to form a cured coating film with excellent substrate adhesion, long-term hydrophilicity, and long-term dew condensation resistance.

The thermosetting coating composition according to the present invention can be suitably used as a coating material. Cured coating films formed from such thermosetting coating compositions can be applied to various fields where transparency, substrate adhesion, long-term hydrophilicity, and long-term condensation resistance are required. I can do it. In particular, the thermosetting coating composition according to the present invention does not require ultraviolet irradiation equipment for curing, so it can be widely used even on objects with complex surface shapes. Examples of such objects include plumbing products for bathrooms and kitchens, glasses, goggles, show windows, headlamps, rear lamps, face shields, etc. that have complex shapes. . Each component constituting the thermosetting coating composition will be described in detail below.

((A) Amino resin)
(A) The amino resin is not particularly limited, and examples thereof include melamine resin, guanamine resin, glycoluril resin, and urea resin. Among these, melamine resin is preferred from the viewpoint of hydrophilicity and curability. The melamine resin may be either a monomer or a condensate consisting of a dimer or more, or a mixture thereof.

The melamine resin is preferably alkyl etherified. As the lower alcohol used for alkyl etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol, etc. can be used. Among these, methylated melamine resin, butylated melamine resin, and methyl-butyl mixed etherified melamine resin are particularly preferred.

Examples of the methylated melamine resin include MW-30M, NW-30, NW-22, MS-21, MS-11, NM-24X, MS-001, MX-002, and MX manufactured by Sanwa Chemical Co., Ltd. -035, MX-042, MX-706, MX-708, MX-730, MX-750, and Amidia L-105-60 manufactured by DIC Corporation. Examples of the butylated melamine resin include Melan 2220, 22, 221, 282B, 28, 265B-2, 2650LS, 268A, and 803A manufactured by Showa Denko Materials Co., Ltd. Examples of the methyl-butyl mixed etherified melamine resin include MX-43, 45, 410, and 417 manufactured by Sanwa Chemical Co., Ltd.

Among the alkyl etherified melamine resins mentioned above, those containing methylol groups, imino groups, or both methylol groups and imino groups in the molecule as functional groups have low-temperature curability when the object to be coated is a plastic base material. It is more preferable from the viewpoint of These may be used alone or in combination of two or more.

The weight average degree of polymerization of the melamine resin is not particularly limited, but is preferably 1.5 or more and 10.0 or less, more preferably 2.0 or more and 9.0 or less. When the weight average degree of polymerization of the melamine resin is within the above numerical range, a coating film with a good balance between hardness and flexibility can be obtained, and defects such as cracks are less likely to occur. Note that the weight average degree of polymerization can be calculated based on the weight average molecular weight determined in terms of standard polystyrene by gel permeation chromatography (GPC).

(A) The content of the amino resin is 45 parts by mass or more and 100 parts by mass or less, preferably 47 parts by mass or more and 100 parts by mass based on 100 parts by mass of the resin component in terms of solid content in the thermosetting coating composition. or less, and more preferably 50 parts by mass or more and 100 parts by mass or less. If the content of the amino resin is within the above numerical range, the main reaction mechanism is self-condensation reaction between the amino resins, and by taking advantage of the hydrophilicity of the amino resin itself, the cured coating film has particularly excellent long-term hydrophilicity. can be obtained.

((B) Colloidal silica)
(B) Colloidal silica is a colloidal solution of silicon dioxide (silica, SiO ₂ ) or its hydrate. Depending on the properties of the dispersion medium (solvent), colloidal solutions can be divided into aqueous colloidal silica and organic solvent-based organosilica sol, and either can be used. Preferably, the colloidal silica is in a dispersed state. The dispersed state refers to a state in which silica is suspended as fine particles in a medium (for example, water) due to electrostatic repulsion between silica particles whose surfaces are positively or negatively charged. Colloidal silica in a dispersed state is preferable because it can form a coating film with higher transparency.

Examples of organic solvents used as a dispersion medium for colloidal silica include methanol, ethanol, normal propanol, isopropanol, normal butanol, isobutanol, t-butanol, ethylene glycol, propylene glycol, trimethylene glycol, butanediol, and ethylene glycol monopropyl. Examples include ether, propylene glycol monomethyl ether, methyl ethyl ketone, methyl isobutyl ketone, and the like.

As the silica forming colloidal silica, chain silica is preferably used. Chained silica is silica in which silica particles are bonded in a chain to form an elongated shape, and more preferably silica is silica in which silica particles are bonded in a chain and has an elongated shape extending only in one plane. . In addition to the above-mentioned basic structure, the chain silica partially has at least one type selected from the group consisting of a branched structure, a cyclic structure, a crosslinked structure, a spherical structure, a rod-like structure, a flat structure, and a scale-like structure. It may have a fine structure. By incorporating chain silica, the surface area of the silica increases, which increases the number of silanol groups exposed on the surface of the cured coating, creating fine irregularities on the surface of the cured coating, making the structural hydrophilic effect more pronounced. . Therefore, by using chain silica, it is possible to make it more hydrophilic than when using spherical silica.

It is preferable that the chain silica is not subjected to hydrophobic treatment so that it can easily maintain hydrophilicity for a long period of time. On the other hand, in order to further improve the hydrophilicity of the chain silica, a hydrophilic treatment may be performed to introduce a hydrophilic group onto the surface. The method of hydrophilic treatment is not particularly limited, and can be carried out by conventionally known methods. Hydrophilic groups to be introduced include hydroxyl groups, alkali metal salts thereof, silanol groups, alkali metal salts thereof, carboxylic acid groups, alkali metal salts thereof, sulfonic acid groups, alkali metal salts thereof, phosphoric acid groups, and alkali metal salts thereof. Other examples include polyalkylene oxide groups, additions and inclusion products thereof with alkali metal compounds, quaternary ammonium bases, quaternary phosphonium bases, and the like. Among these, polyalkylene oxide groups and silicate groups having a high concentration of hydroxyl groups or silanol groups are particularly preferred, and these hydrophilic groups are chemically bonded to the surface of silica via an appropriate functional group. It is preferable to introduce it. Particularly from the viewpoint of prolonging hydrophilicity, surface-untreated silica having a high concentration of silanol groups is particularly preferred.

The primary average particle diameter of the silica particles is preferably 1 nm to 300 nm, more preferably 3 to 100 nm, and even more preferably 5 to 50 nm. As long as the primary average particle diameter of the silica particles is within the above range, the shape of each silica particle unit may be spherical or rod-shaped. The chain structure of silica is preferably a combination of 3 or more and 20 or less silica particle units, more preferably 4 or more and 10 or less silica particle units. The average length of the chain structure of silica is preferably 10 nm to 500 nm, more preferably 30 to 300 nm, and still more preferably 40 to 200 nm. Note that the primary average particle diameter of silica can be measured by the BET method, dynamic light scattering method, electron microscopy, or the like. If the primary average particle diameter of the silica particles and the average length of the chain structure are within the above numerical ranges, long-term hydrophilicity can be further improved.

As the chain silica, commercially available products can also be used. Commercially available products include, for example, product names: MA-ST-UP, IPA-ST-UP, PGM-ST-UP, MEK-ST-UP, etc. manufactured by Nissan Chemical Co., Ltd.
Furthermore, as the spherical silica, commercially available products can be similarly used. Can be mentioned.

(B) The content of colloidal silica is 150 parts by mass or more, preferably 150 parts by mass or more and 1000 parts by mass or less, based on 100 parts by mass of the resin component in terms of solid content in the thermosetting coating composition. More preferably, the content is 170 parts by mass or more and 700 parts by mass or less, more preferably 190 parts by mass or more and 600 parts by mass or less, and even more preferably 200 parts by mass or more and 500 parts by mass or less. When the content of colloidal silica is within the above range, a cured coating film particularly excellent in long-term dew condensation resistance can be obtained.

((C) Polyol resin)
(C) The polyol resin is not particularly limited, and examples thereof include (meth)acrylic polyol, polyester polyol, polyether polyol, polycarbonate polyol, and the like. Among these, it is preferable to use (meth)acrylic polyol. These may be used alone or in combination of two or more.

The (meth)acrylic polyol is not particularly limited, but for example, a polymer of a (meth)acrylic compound containing a (meth)acrylic compound having a hydroxyl group can be used. As the (meth)acrylic compound having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc. can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use 2-hydroxyethyl (meth)acrylate.

Other compounds that can be copolymerized with (meth)acrylic compounds having hydroxyl groups include, for example, unsaturated carboxylic acid compounds such as (meth)acrylic acid, maleic acid, fumaric acid; methyl (meth)acrylate, ethyl (meth)acrylate; 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 (meth)acrylic acid alkyl esters such as acrylate, isostearyl (meth)acrylate, cetyl (meth)acrylate, lauryl (meth)acrylate; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3, (Meth)acrylic compounds having a fluorine atom such as 3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate; isobornyl ( (Meth)acrylic compounds having an alicyclic structure such as meth)acrylate, cyclohexyl (meth)acrylate, cydiclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate; polyethylene glycol mono(meth)acrylate, methoxy (Meth)acrylic compounds having ether groups such as ethyl (meth)acrylate, methoxybutyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 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; styrene, α - Vinyl compounds such as methylstyrene, vinyl acetate, vinyl benzoate, vinyltoluene, acrylonitrile, vinylpyridine, vinylpyrrolidone, vinyl chloride; acrylamide compounds such as N,N dimethyl (meth)acrylamide, N,N diethyl (meth)acrylamide, etc. etc. can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use (meth)acrylic acid, methyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and methoxyethyl (meth)acrylate. .

The weight average molecular weight (Mw) of the (meth)acrylic polyol is 500 to 100,000, more preferably 1000 to 50,000, and even more preferably 2000 to 20,000. Weight average molecular weight (Mw) can be measured using gel permeation chromatography (GPC).

The polyester polyol is not particularly limited, but may be prepared by known methods such as polycondensation reaction of diol and dicarboxylic acid or dicarboxylic acid chloride, esterification of diol or dicarboxylic acid and transesterification reaction, etc. You can use those obtained at
Diols used in the synthesis of polyester polyols are not particularly limited, but include, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dibropylene glycol, and triethylene. Examples include glycol, tripropylene glycol, tetraethylene glycol, and tetrapropylene glycol.
Dicarboxylic acids used in the synthesis of polyester polyols are not particularly limited, but include, for example, adipic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, dimaleic acid, terephthalic acid, isophthalic acid, Examples include phthalic acid.

Examples of polyether polyols include, but are not particularly limited to, polyethylene oxide, polypropylene oxide, ethylene oxide/propylene oxide random copolymers, and the like.

The polycarbonate polyol is not particularly limited, but includes, for example, a reaction product obtained by polycondensing component A and component B below. Component A is not particularly limited, but includes, for example, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, 1, Diols such as 4-cyclohexanedimethanol, 2-methylpropanediol, dipropylene glycol, and diethylene glycol, or these diols and dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, and hexahydrophthalic acid. Examples include reaction products with acids. Component B is not particularly limited, but includes, for example, diphenyl carbonate, bis(chlorophenyl) carbonate, dinaphthyl carbonate, phenyltolyl carbonate, phenylchlorophenyl carbonate, 2-tolyl-4-tolyl carbonate, dimethyl carbonate. , aromatic carbonates or aliphatic carbonates such as diethyl carbonate, diethylene carbonate, and ethylene carbonate.

The content of the polyol resin (C) is preferably less than 55 parts by mass, more preferably less than 50 parts by mass, based on 100 parts by mass of the resin component in the thermosetting coating composition in terms of solid content. In the present invention, stress relaxation is not possible due to the low content of polyol resin as a resin component, and curing shrinkage of the coating film increases. However, by blending a large amount of colloidal silica, curing shrinkage can be suppressed. can.

(Other ingredients)
The thermosetting coating composition according to the present invention may contain other components other than the above-mentioned components (A) to (C) as long as the object of the present invention is not impaired. Other ingredients include leveling agents, polymerization inhibitors, antistatic agents, antioxidants, non-reactive diluents, matting agents, antifoaming agents, dispersants, antisettling agents, dispersants, heat stabilizers, and adhesive properties. An improver, a silane coupling agent, a plasticizer, etc. can be added as necessary.

<Method for preparing thermosetting coating composition>
The thermosetting coating composition according to the present invention can be obtained by mixing and stirring the above-mentioned components using a conventionally known device such as a mixer, a disperser, or an agitator. Such devices include, for example, mixing/dispersing mills, homodispers, mortar mixers, rolls, paint shakers, homogenizers, and the like.

In the present invention, the thermosetting coating composition can be diluted with a solvent as necessary, such as by adjusting the viscosity to be suitable as a coating composition. The solvent is not particularly limited as long as it dissolves the resin component in the resin composition. Specifically, aromatic hydrocarbons (e.g. toluene, xylene and ethylbenzene), esters or ether esters (e.g. ethyl acetate, butyl acetate and methoxybutyl acetate), ethers (e.g. diethyl ether, tetrahydrofuran, ethylene glycol monoethyl ethers, ethylene glycol monobutyl ether, monomethyl ether of propylene glycol and monoethyl ether of diethylene glycol), ketones (e.g. acetone, methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone and cyclohexanone), alcohols (e.g. methanol, ethanol, n - or i-propanol, n-, i-, sec- or t-butanol, 2-ethylhexyl alcohol and benzyl alcohol), amides (e.g. dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.), sulfoxides (e.g. dimethyl sulfoxide), water, and mixed solvents of two or more of these.

(cured coating film)
The cured coating film is formed from the thermosetting coating composition described above. The thickness of the cured coating film is not particularly limited, but is usually 1 to 100 μm, preferably 1.5 to 20 μm, and more preferably 2 to 10 μm. The upper limit is preferably 100 μm from the viewpoint of drying properties and curability, and the lower limit is preferably 1 μm from the viewpoints of transparency, substrate adhesion, long-term hydrophilicity, and long-term dew condensation resistance. The film thickness in the present invention refers to the thickness of a cured coating film when a cross section of the cured coating film is observed using an optical microscope, a scanning electron microscope (SEM), or the like. When forming a film with such a thickness, a film of a desired thickness may be formed by one coating, or a film of a desired thickness may be formed by a plurality of coatings.

When the cured coating film formed from the above-mentioned thermosetting coating composition has a thickness of 2 to 4 μm, the haze measured in accordance with JIS K 7136 is preferably 1.0% or less, and 0.0% or less. It is more preferably 9% or less, and even more preferably 0.8% or less. Further, the cured coating film with a thickness of 2 to 4 μm preferably has a total light transmittance of 70% or more, more preferably 80% or more, and 90% or more, as measured in accordance with JIS K 7361-1. % or more is more preferable. If the haze and total light transmittance are within the above ranges, the transparency will be excellent.

<Substrate with cured coating>
The substrate with a cured coating film according to the present invention has a cured coating film formed from the above thermosetting coating composition on at least a portion of the substrate surface. The base material is not particularly limited, and various plastic films can be used. Examples of plastic films include polyester resins, polycarbonate resins, polystyrene resins, polyolefin resins, polyethersulfone resins, acrylonitrile-styrene copolymer resins, polyamide resins, cellulose resins, polyarylate resins, polymethyl methacrylic resins, and polymethacrylimide resins. Films such as In addition, since the thermosetting coating composition of the present invention can form a transparent cured coating film with high total light transmittance and low haze, it is preferable to use a transparent plastic film.

The thickness of the base material is not particularly limited, but is usually 10 μm or more and 500 μm or less, preferably 30 to 400 μm.

<Method for producing base material with coating film>
The coated substrate according to the present invention includes a coating step of applying the above-mentioned thermosetting coating composition to at least one surface of the substrate;
After the coating step, a curing step of curing the photocurable resin composition by heating to form a cured coating film;
This includes: Each step will be explained in detail below.

(Coating process)
The coating step is a step of applying the above-mentioned thermosetting coating composition onto one side of the substrate by a conventionally known method. For coating, coating machines such as a bar coater, a gravure coater, a roll coater (such as a natural roll coater and a reverse roll coater), an air knife coater, a spin coater, and a blade coater can be used. Among these, a coating method using a gravure coater is preferred from the viewpoint of workability and productivity.

The film thickness after curing and drying is preferably within the range of the film thickness of the above-mentioned cured coating film.

When using a resin composition diluted with a solvent, it is preferable to dry it after application. Note that drying may be performed simultaneously with the curing step described below.

(Curing process)
The curing step is a step of heating the coated surface of the base material to cure the applied thermosetting coating composition to form a cured coating film. Examples of the heating method include hot air drying (hot air dryer, dryer, etc.). The heating temperature is preferably 80 to 150°C, more preferably 90 to 140°C, and even more preferably 100 to 130°C from the viewpoint of coating film smoothness, coating film appearance, and drying rate.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

The following materials were used to prepare the thermosetting coating composition.
・Amino resin 1 (butylated melamine resin, manufactured by Showa Denko Materials Co., Ltd., product name: Melan 2220)
・Amino resin 2 (methylated melamine resin, containing methylol groups/imino groups, weight average degree of polymerization: 5.7, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MS-001)
・Amino resin 3 (methylated melamine resin, containing methylol groups/imino groups, weight average degree of polymerization: 7.2, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-002)
・Amino resin 4 (methylated melamine resin, containing methylol groups/imino groups, weight average degree of polymerization: 2.7, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-042)
・Amino resin 5 (methyl-butyl mixed etherified melamine resin, containing methylol groups/imino groups, weight average degree of polymerization: 1.8, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-410)
・Amino resin 6 (methylated melamine resin, containing methylol groups/imino groups, weight average degree of polymerization: 2.6, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-706)
・Amino resin 7 (methylated melamine resin, imino group-containing, weight average degree of polymerization: 3.0, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-708)
・Amino resin 8 (methylated melamine resin, imino group-containing, weight average degree of polymerization: 2.4, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MX-730)
・Colloidal silica 1 (organosilica sol, spherical silica, average particle size 12 nm, manufactured by Nissan Chemical Co., Ltd., product name: PGM-ST)
・Colloidal silica 2 (organosilica sol, chain silica, average particle size 12 nm, manufactured by Nissan Chemical Co., Ltd., product name: PGM-ST-UP)

(Synthesis of polyol resin 1)
158 parts by mass of propylene glycol 1-monomethyl ether (PGM) was placed in a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, and the temperature was raised to 115°C. Subsequently, 50 parts by mass of 2-hydroxyethyl methacrylate (2-HEMA), 50 parts by mass of methoxyethyl methacrylate (MEMA), and 5 parts by mass of t-butylperoxy 2-ethylhexanoate were added to the flask over 1 hour. Added dropwise. Thereafter, the reaction was carried out for 4 hours while the temperature inside the flask was maintained at 115° C. to obtain polyol resin 1 ((meth)acrylic polyol, Mw: 6400).

(Synthesis of polyol resin 2)
Polyol resin 2 (acrylic polyol, Mw: 6600) was obtained in the same manner as in the synthesis of polyol resin 1, except that 2-HEMA was changed to 30 parts by weight and MEMA was changed to 70 parts by weight.

[Examples 1 to 16, Comparative Examples 1 to 2]
[Preparation of thermosetting coating composition]
A thermosetting coating composition was prepared by stirring and mixing each component according to the formulations listed in Tables 1 and 2.

[Manufacture of substrate with cured coating film]
The thermosetting coating composition prepared above was coated once on a PET film (thickness: 100 μm, manufactured by Toyobo Co., Ltd., product name: Cosmoshine A4300) using a wire bar coater so that the dry film thickness was about 3 μm. The coating was applied and allowed to stand for 10 minutes in a hot air dryer set at 110° C. to cure the coating, thereby forming a cured coating to produce a substrate with a cured coating.

[Evaluation of substrate with cured coating]
(Appearance of paint film)
The appearance of the substrate with the cured coating produced above was visually evaluated according to the following criteria. The measurement results are shown in Tables 3 and 4.
[Evaluation criteria]
○: The coating film has no defects in appearance (defects in appearance such as whitening, spots, cracks, etc.) and is colorless and transparent.
×: There is a defect in the appearance of the coating film.

(optical properties)
The haze (HZ) of the substrate with the cured coating produced above was measured in accordance with JIS K 7136 using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., model number: NDH4000), and the haze (HZ) was measured in accordance with JIS K 7361- The total light transmittance (TT) was measured according to 1. The measurement results are shown in Tables 3 and 4. If the haze value was 1% or less, it was considered to be a pass. On the other hand, if the haze value exceeded 1%, it was judged as a failure. Moreover, if the total light transmittance was 90% or more, it was considered to be a pass. On the other hand, if the total light transmittance was less than 90%, it was judged as a failure.

(Base material adhesion)
According to the grid test method described in JIS K 5600-5-6, a cutter was used to cut 100 squares (10 squares x 10 squares) with a width of 1 mm onto the cured coating film of the substrate with the cured coating film manufactured above. ) scratches were made on a grid pattern to prepare a test piece. Subsequently, Cellotape (registered trademark) (trade name, manufactured by Nichiban Co., Ltd.) was attached to the test piece. Thereafter, this Sellotape (registered trademark) was immediately pulled upward at an angle of 45 degrees with respect to the grid pattern to peel it off. The number of coats remaining in a grid pattern was counted, and this number of coats was used as an index of adhesion to the base material, which was evaluated according to the following criteria. The measurement results are shown in Tables 3 and 4.
[Evaluation criteria]
○: There was no peeling at all. (Number of coatings 100/100)
Δ: There was slight peeling. (Number of coatings: 90 or more and less than 100/100)
×: There was a lot of peeling. (Number of coatings less than 90/100)

(Hydrophilicity: initial)
For the substrate with the cured coating film manufactured above, 1 μL of water was dropped onto the surface of the cured coating film, and the contact angle was measured after 10 seconds using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., model number: DM-500). did. The hydrophilicity of the cured coating film was evaluated using the following criteria. The measurement results are shown in Tables 3 and 4.
[Evaluation criteria]
◎: The contact angle was 30° or less, and the hydrophilicity was very good.
○: The contact angle was more than 30° and less than 40°, and the hydrophilicity was good.
×: The contact angle was more than 40°, and the hydrophilicity was poor.

(Hydrophilicity: after hot water test)
The substrate with the cured coating produced above was immersed in hot water at 60° C. for 24 hours to conduct a hot water test. Subsequently, 1 μL of water was dropped onto the surface of the cured coating film after the hot water test, and the contact angle 10 seconds later was measured in the same manner as above to evaluate hydrophilicity. The measurement results are shown in Tables 3 and 4.

(Hydrophilicity: after constant temperature and humidity test)
The substrate with the cured coating film produced above was left standing in a constant temperature and humidity machine set at 85° C. and 85% RT for 250 hours and 500 hours to conduct a constant temperature and humidity test. Hydrophilicity was evaluated by dropping 1 μL of water onto the surface of the cured coating film after each time period had elapsed, and measuring the contact angle 10 seconds later in the same manner as above. The measurement results are shown in Tables 3 and 4.

(Condensation resistance: initial)
Regarding the substrate with the cured coating film produced above, water was sprayed onto the surface of the cured coating film, and it was visually confirmed whether the water droplets wetted and spread on the coating film. The dew condensation resistance of the cured coating film was evaluated using the following criteria. An evaluation of "○" or "△" was regarded as a pass, and an evaluation of "x" was regarded as a failure. The evaluation results are shown in Tables 3 and 4.
[Evaluation criteria]
○: Water droplets completely wetted and spread on the coating film.
△: Water droplets were slightly generated on the coating film.
×: Water droplets were generated on the coating film.

(Condensation resistance: repeated)
Condensation resistance as described above for the substrate with the cured coating film produced above: As in the initial evaluation, water was repeatedly sprayed on the cured coating surface 10 times, and then the cured coating surface was sprayed again. Water was sprayed on the coating film, and it was visually confirmed whether the water droplets spread on the coating film. Condensation resistance was evaluated in the same manner as above. The evaluation results are shown in Tables 3 and 4.

(Condensation resistance: after hot water test)
A hot water test was conducted in the same manner as above for the substrate with the cured coating film produced above. Subsequently, water was sprayed on the surface of the cured coating film after the hot water test, and it was visually confirmed whether the water droplets wetted and spread on the coating film. Condensation resistance was evaluated in the same manner as above. The evaluation results are shown in Tables 3 and 4.

(Condensation resistance: after constant temperature and humidity test)
A constant temperature and humidity test was conducted on the substrate with the cured coating film manufactured above in the same manner as above. Subsequently, water was sprayed onto the surface of the cured coating film after the constant temperature and humidity test, and it was visually confirmed whether the water droplets wetted and spread on the coating film. Condensation resistance was evaluated in the same manner as above. The evaluation results are shown in Tables 3 and 4.

Claims (8)

A thermosetting coating composition comprising (A) an amino resin and (B) colloidal silica,
The content of the amino resin (A) is 45 parts by mass or more and 100 parts by mass or less based on 100 parts by mass of the solid content of the resin component,
A thermosetting coating composition in which the content of the colloidal silica (B) is 150 parts by mass or more based on 100 parts by mass of the resin component in terms of solid content. The thermosetting coating composition according to claim 1, wherein the colloidal silica (B) contains chain silica. The thermosetting coating composition according to claim 1 or 2, wherein the thermosetting coating composition contains (C) a polyol resin in addition to the (A) amino resin as the resin component. The thermosetting coating composition according to claim 3, wherein the polyol resin (C) contains a (meth)acrylic polyol. The thermosetting coating composition according to any one of claims 1 to 4, wherein the amino resin (A) contains a melamine resin. A cured coating film formed from the thermosetting coating composition according to any one of claims 1 to 5. A substrate with a cured coating film having a cured coating film formed from the thermosetting coating composition according to any one of claims 1 to 5 on at least a portion of the substrate surface. A coating step of applying the thermosetting coating composition according to any one of claims 1 to 5 on at least one surface of a substrate;
After the coating step, a curing step of curing the thermosetting coating composition by heating to form a cured coating film;
A method for producing a substrate with a cured coating film, comprising: