Coating film manufacturing method and laminated coating film

Abstract

The present invention addresses the problem of providing: a method for producing a coating film, the method enabling the production of a coating film which has good matting properties even in cases where a solvent-free coating composition is used; and preferably, a method for producing a coating film, the method enabling the production of a coating film which achieves good coating film durability, while being capable of suppressing odor during the time of application, and which has good matting properties even in cases where a smooth surface is coated.　A method for producing a coating film according to the present disclosure comprises: a step in which a first coating film is formed by applying a first coating composition to an object to be coated; a step in which a second coating composition is applied onto the first coating film within the time from immediately after the application of the first coating composition to the object to be coated to the time point when the first coating film has been cured and dried, thereby forming a multilayer coating film in which the first coating film and the second coating film are stacked; and a step in which a coating film is formed by curing the multilayer coating film. With respect to this method for producing a coating film, the first coating composition is a two-pack type coating composition which contains a solvent-free base material and a solvent-free curing agent; and the second coating composition contains fine silica particles and a hydrophilic medium.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a coating film and a multilayer coating film. [Background technology]

[0002] Pavements such as asphalt pavements and concrete pavements are widely used as road surfaces for vehicles and pedestrians. Markings are provided on these pavements to identify areas to be traversed and to alert pedestrians to precautions to take when passing through. Furthermore, a coating film may be formed on the surface of the pavement to prevent the pavement from overheating, improve environmental comfort, or repair the pavement. In the field of coatings, which primarily use inorganic materials as substrates for painting and repairing such pavements, solvent-free paints are used to reduce volatile solvents. Examples of known solvent-free paints include epoxy-based paints, urethane-based paints, and urea-based paints.

[0003] As examples of such coatings and coating films formed from such coatings, Patent Document 1 describes a material based on a polyurethane resin composition, which is blended with ultrafine silica particles and polyethylene glycol with an average molecular weight of 100 to 20,000, or its ether or ester. Patent Document 2 describes a coating film obtained by contacting a substrate containing an organic polymer material such as poly(meth)acrylate, polyester, or polycarbonate polyolefin with a silica nanoparticle coating composition containing an aqueous dispersion of silica nanoparticles and an acid with a pKa of less than 5, and then drying the coating composition. Patent Document 3 describes a coating composition containing metal oxide fine particles, a binder component, a surface tension modifier, and a solvent component. Patent Document 4 describes a combination of an organic coating film containing wax particles and an inorganic coating film formed on the organic coating film and consisting of a composition represented by the formula KO·xSiO (3.5≦x≦6.8). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-180601 [Patent Document 2] Special Publication No. 2015-525131 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-246603 [Patent Document 4] Japanese Patent Application Publication No. 2019-22953 Summary of the Invention [Problem to be solved by the invention]

[0005] Coatings formed by applying conventional solvent-free coating compositions tend to have high gloss values. In particular, in recent years, the number of roads (road surfaces) with high smoothness has been increasing. When these coating compositions are applied to roads with high smoothness (road surfaces), the gloss value of the coating film increases, and light reflection is likely to occur on the coating film surface. In this case, the strong reflection of sunlight (e.g., the afternoon sun), lighting, vehicle headlights, etc. can cause dazzle to the driver and reduce the visibility of road markings, etc., which is undesirable from a safety perspective. However, it has still been difficult to reduce the gloss of solvent-free coating compositions (to form a matte coating film).

[0006] Furthermore, unevenness may occur on the road surface due to the influence of ceramic aggregates, etc., scattered on the road surface for the purpose of preventing slippage. This may result in a decrease in the gloss value of the road surface on which the coating film is formed. However, when the aggregate is scattered, the aggregate often scatters, and since the aggregate is scattered for the purpose of preventing slippage on the road surface, uneven distribution of the aggregate is likely to occur. Furthermore, if the amount of aggregate increases, the physical properties of the coating film may deteriorate. Furthermore, for example, when painting a road surface, the viscosity of the paint composition may increase during painting, which may reduce painting workability or may prevent the formation of a coating film that meets the performance requirements for the road surface.

[0007] The present disclosure addresses the need to provide a method for producing a coating film that provides a coating film with good matte properties even when a solvent-free coating composition is used, and preferably provides a method for producing a coating film that provides good matte properties even when applied to a smooth surface, achieves good coating film durability (particularly abrasion resistance and water resistance), and can further suppress odors during application. [Means for solving the problem]

[0008] The present disclosure includes the following. [1] A method for producing a coating film, the step of applying a first coating composition to a substrate to form a first coating film; the step of applying a second coating composition onto the first coating film immediately after the first coating composition is applied to the substrate and before the first coating film is cured and dried, to form a laminated coating film in which the first coating film and the second coating film are laminated; and the step of curing the laminated coating film to form a coating film, the first coating composition is a two-component coating composition containing a solvent-free base agent and a solvent-free curing agent; The method for producing a coating film, wherein the second coating composition contains silica fine particles and a hydrophilic medium. [2] The method for producing a coating film according to [1], wherein in the first coating composition, the solvent-free base agent contains a compound having two or more groups with active hydrogen atoms in the molecule, and the solvent-free curing agent contains a polyisocyanate. [3] The method for producing a coating film according to [2], wherein the compound having two or more groups having an active hydrogen atom in one molecule is at least one selected from the group consisting of polyols and polyamines. [4] The method for producing a coating film according to [2] or [3], wherein in the first coating composition, the molar ratio [NCO / H] of the isocyanate group contained in the solventless curing agent to the group having an active hydrogen atom contained in the solventless main agent is 0.5 or more and 2.0 or less. [5] The method for producing a coating film according to any one of [1] to [4], wherein the first coating composition further contains a pigment. [6] The method for producing a coating film according to [5], wherein the pigment includes a heat-shielding pigment. [7] The method for producing a coating film according to any one of [1] to [6], wherein in the second coating composition, the average primary particle diameter of the silica fine particles is 1 nm or more and 10 μm or less. [8] The method for producing a coating film according to any one of [1] to [7], wherein the second coating composition contains a photocatalyst. [9] The method for producing a coating film according to [8], wherein the photocatalyst contains titanium oxide.

[10] The method for producing a coating film according to any one of [1] to [9], wherein the coating film is formed on the surface of a pavement.

[11] The method for producing a coating film according to any one of [1] to

[10] , wherein the coating film is a coating film for road markings and / or road heat insulation. [Effects of the Invention]

[0009] According to the coating film manufacturing method of the present disclosure, even when a solvent-free coating composition is used, the resulting coating film has good matte properties, and in particular, even when applied to a smooth surface, it is possible to provide a coating film that can achieve good coating film durability (particularly abrasion resistance and water resistance), and furthermore, it is possible to suppress odors during application. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing a coating film in the present disclosure uses a two-component coating composition containing a solvent-free base agent (hereinafter sometimes simply referred to as "base agent") and a solvent-free curing agent (hereinafter sometimes simply referred to as "curing agent") as a first coating composition, and a coating composition containing silica microparticles and a hydrophilic medium as a second coating composition, and includes the steps of applying the first coating composition to an object to be coated to form a first coating film (first coating film forming step), applying the second coating composition onto the first coating film immediately after applying the first coating composition to the object to be coated and before the first coating film becomes hardened and dried, to form a laminated coating film in which the first coating film and the second coating film are laminated (second coating film forming step), and curing the laminated coating film to form a matte coating film (curing step).

[0011] The coating film manufacturing method of the present disclosure includes the second coating film forming step, which reduces (adjusts) the gloss of the formed coating film, resulting in a matte finish. This improves the visibility of road markings and other information for workers and drivers, contributing to improved safety. It is also believed that road surface information can be effectively provided for automated driving, which has been under consideration in recent years.

[0012] In two-component coating compositions, the main component and curing agent begin to react immediately after mixing, and curing proceeds gradually. Without being bound by any particular theory, it is believed that when a first coating film is formed by applying a first coating composition, which is a two-component coating composition, and a second coating composition containing silica microparticles and a hydrophilic medium is applied before the first coating film is completely cured, the silica microparticles aggregate and bond to each other as the hydrophilic medium dries, becoming fixed on the first coating film. As a result, it is believed that not only can a matte coating film be efficiently formed, but also a coating film with good abrasion resistance and water resistance and a long service life can be formed.

[0013] Furthermore, in the present disclosure, a solvent-free coating composition is used as the first coating composition, which reduces odor during storage and application, unlike when using a coating composition containing an organic solvent such as toluene, and prevents fires that may occur due to the use of organic solvents. Furthermore, if a first coating film is formed from the first coating composition and a second coating film is formed before the first coating film is completely cured, there is no reduction in the film thickness of the first coating film, or even if there is, it is very slight. Therefore, the resulting coating film has excellent coating film properties such as abrasion resistance and a long service life.

[0014] Furthermore, in the present disclosure, the gloss of the coating film can be reduced without using a matting agent (e.g., aggregate). This simplifies the process and prevents poor coating appearance due to aggregate scattering, especially when the substrate is relatively smooth. Furthermore, it prevents deterioration of the coating film appearance, such as uneven gloss, and deterioration of the coating film physical properties.

[0015] Thus, the coating film manufacturing method of the present disclosure can form fine surface irregularities on the coating film surface, even when using a solvent-free coating composition, and can form a coating film with a matte effect.Furthermore, it can form a coating film with superior coating film strength, etc.

[0016] In this disclosure, "solvent-free" refers to a "solvent-free type" that can suppress the emission of volatile chemical substances (VOCs), and the incorporation of solvents taking into consideration paintability and workability is permitted, and includes not only those with a solvent (especially VOC) content of 0% by mass, but also those that contain solvent to the extent that the impact of VOC emission can be suppressed. In solvent-free compositions in this disclosure, such as solvent-free base resins, solvent-free curing agents, and solvent-free two-component curing paint compositions, the solvent content may be, for example, 10% by mass or less, further 5% by mass or less, particularly 3% by mass or less, and particularly 1% by mass or less.

[0017] (First paint film formation process) In the first coating film forming step, the first coating composition is applied to a substrate. The base agent and curing agent in the first coating composition may be mixed before or simultaneously with coating. When the base agent and curing agent are mixed before coating, they are preferably mixed immediately before coating.

[0018] The coating method is not particularly limited, and at least one method selected from the group consisting of spray coating, coating using a static method, coating using a collision mix method, slit coater coating, flow coating, and a combination of two or more of these methods can be used, and in particular at least one method selected from the group consisting of coating using a collision mix method, spray coating, slit coater coating, flow coating, and a combination of two or more of these methods can be used.

[0019] When using a coating method such as spray coating, slit coater coating, static coating, or flow coating, the base agent and curing agent may be mixed before coating. When using a coating method such as spray coating or collision mixing coating, the base agent and curing agent may be mixed during coating.

[0020] In one embodiment, the coating method of the present disclosure may include two-liquid impingement mixing spray coating, in which two liquid components, a base resin and a curing agent, are sprayed by collision mixing. Two-liquid impingement mixing spray coating can be performed, for example, by spraying the base resin and the curing agent under high pressure and then causing collision mixing at the coating location. For two-liquid impingement mixing spray coating, it is preferable to use a high-pressure two-liquid impingement mixing type spraying device.

[0021] Examples of substrates to which the first coating composition is applied include pavements such as road surfaces. The type of pavement is not particularly limited, and examples include asphalt pavement and concrete pavement. The asphalt used in the asphalt pavement is not particularly limited, and examples include dense-graded asphalt mixtures, fine-graded asphalt mixtures, dense-graded gap asphalt mixtures, open-graded asphalt mixtures, and porous asphalt mixtures. The surface of the substrate may be smooth like a concrete pavement surface, or may have irregularities like an asphalt pavement surface.

[0022] The pavement may be used as the substrate as it is, or a primer may be applied to the surface of the pavement and, if necessary, cured and dried before use as the substrate. The primer is preferably a solvent-free type, and any conventional primer may be used as appropriate.

[0023] The amount of the first coating composition to be applied can be adjusted so that the film thickness after drying and curing when applied to a smooth surface is 50 μm or more and 2,000 μm or less. The first coating composition may be applied multiple times as needed. The amount of the first coating composition to be applied when applied to a smooth surface is, for example, 100 g / m 2 or more, preferably 300 g / m 2 More preferably, 350 g / m 2 For example, the amount may be 2,000 g / m or more. 2 Less than 1,000 g / m 2 Less than 500 g / m 2 The amount may be as follows:

[0024] In one embodiment, the coating composition may be applied while being heated or kept at a temperature of 10°C to 60°C, or the coating composition immediately after application may be heated or kept at a temperature of 10°C to 60°C. Setting the temperature within this range makes it easy to reduce or suppress the gloss of the resulting coating film. Furthermore, coating films can be formed on substrates with various surface morphologies, and coating films with excellent abrasion resistance and long service life can be formed. Furthermore, the coating film formation time can be further shortened compared to conventional coating film production methods.

[0025] In the first coating film formed by applying the first coating composition, the curing reaction between the base agent and the curing agent proceeds as is. Therefore, the method for drying the first coating film is not particularly limited, and may be, for example, drying at room temperature or forced drying using an infrared heater, burner, etc., depending on the ambient environment such as the air temperature and the temperature of the object to be coated.

[0026] In the present disclosure, the first coating composition is a solvent-free type, and therefore, when the term "drying" is used with respect to the first coating film, it means that the fluidity of the first coating film is reduced, and is not necessarily used in the sense of volatilizing the solvent.

[0027] (First paint composition) The first coating composition used in the first coating film forming step is a solvent-free type and contains a base agent and a curing agent. Because the first coating composition is solvent-free and suppresses the emission of volatile components, no odor is generated during storage or application, reducing the burden on the environment. Furthermore, the first coating composition has better weather resistance than coating compositions containing large amounts of solvents, such as aqueous solvents or organic solvents, and can form a coating film with high toughness, making it suitable as a coating composition for forming markings, coatings, etc. on pavements such as road surfaces.

[0028] (solvent-free base) The base resin comprises a film-forming resin (a).

[0029] The film-forming resin (a) is not particularly limited as long as it is a resin having two or more reactive groups in the molecule that can react with the curing agent (b) described below, and is preferably a resin having two or more groups in the molecule that can react with the curing agent (b) described below to form a urethane bond and / or a urea bond. Examples of reactive groups that can react with the curing agent (b) (preferably groups that can react with the curing agent (b) to form a urethane bond and / or a urea bond) that can react with the curing agent (b) include groups that have an active hydrogen atom.

[0030] Examples of the group having an active hydrogen atom include a hydroxyl group, a substituted or unsubstituted amino group, a silanol group, an active methylene group, a thiol group, a carboxyl group, etc. Examples of the coating film-forming resin (a) include polyols and polyamines.

[0031] The polyol may be any compound having two or more hydroxyl groups in the molecule. Specific examples include high-molecular-weight polyols such as polyether polyols, polyester polyols, acrylic polyols, castor oil-based polyols, and polycarbonate polyols; and low-molecular-weight polyols. The number-average molecular weight of the polyol may be, for example, 50 or more, and even 500 or more, and may be, for example, 10,000 or less, and even 3,000 or less. The number-average molecular weight of the high-molecular-weight polyol may be, for example, 500 or more, preferably 600 or more, and more preferably 700 or more, and may be, for example, 10,000 or less, even 5,000 or less, particularly 3,000 or less, and particularly 1,000 or less. The molecular weight of the low-molecular-weight polyol may be, for example, less than 500, particularly 300 or less, and may be 50 or more. In the present disclosure, the number average molecular weight represents a polystyrene equivalent value determined by gel permeation chromatography (GPC).

[0032] The hydroxyl value of the polyol is preferably 50 mgKOH / g or more, and preferably 2,000 mgKOH / g or less, more preferably 1,500 mgKOH / g or less, even more preferably 500 mgKOH / g or less, and even more preferably 350 mgKOH / g or less. When the hydroxyl value of the polyol is in the above range, a coating film with excellent strength is easily obtained. In the present disclosure, the hydroxyl value refers to the hydroxyl value of the solid content, and can be measured in accordance with the provisions of JIS K 0070.

[0033] The number of hydroxyl groups contained in the polyol is 2 or more, preferably 6 or less, more preferably 4 or less, and further preferably 3 or less per molecule.

[0034] The polyether polyol refers to a polyol having a plurality of ether bonds in the molecule, and examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxytetramethylene glycol, polyoxyhexamethylene glycol, and polyoxyoctamethylene glycol.

[0035] The polyester polyol refers to a polyol having a plurality of polyester bonds in the molecule. Examples of the polyester polyol include an esterification reaction product of a low-molecular-weight polyol with a polycarboxylic acid, a ring-opening condensation product of a cyclic ester compound, and a copolymer thereof.

[0036] The low-molecular-weight polyol used in producing the polyester polyol is, for example, a polyol having a molecular weight of less than 500. Specific examples include linear or branched aliphatic polyols having 1 to 8 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methylpentane-1,5-diol, and diethylene glycol; polyols containing an alicyclic structure, such as cyclohexanedimethanol; and aromatic polyols, such as bisphenol A and bisphenol F.

[0037] Examples of polycarboxylic acids used in the production of the polyester polyol include aliphatic polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid; and anhydrides of the aliphatic polycarboxylic acids and aromatic polycarboxylic acids. Among these, aliphatic polycarboxylic acids are preferred, and adipic acid is more preferred.

[0038] Examples of the cyclic ester compound used in the production of the polyester polyol include ε-caprolactone and 3-methylvalerolactone.

[0039] The acrylic polyol refers to a polyol having units derived from a radically polymerizable monomer. Examples of the radically polymerizable monomer include (meth)acrylic acid; (meth)acrylic acid esters of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; (meth)acrylic monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; and aromatic monomers such as styrene and α-methylstyrene. The radically polymerizable monomer includes at least a (meth)acrylic monomer having a hydroxyl group. In this disclosure, (meth)acrylic acid refers to acrylic acid and methacrylic acid.

[0040] The acrylic polyol can be produced by polymerizing the radical polymerizable monomer in the absence of a solvent or in the presence of an organic solvent. The polymerization temperature may be 80 to 140° C., and the polymerization time may be 1 to 8 hours.

[0041] The polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as benzoyl peroxide, t-butyl peroxide, and cumene hydroperoxide; and organic azo compounds such as azobiscyanovaleric acid and azoisobutyronitrile.

[0042] The organic solvent that can be used in producing the acrylic polyol is preferably a solvent having a boiling point of 60 to 250°C. Specific examples include water-insoluble organic solvents such as butyl acetate, xylene, toluene, methyl isobutyl ketone, propylene glycol, dipropylene glycol dimethyl ether, and methyl ether acetate; and water-soluble organic solvents such as tetrahydrofuran, ethanol, methanol, propanol, isopropanol, 2-butanol, t-butyl alcohol, dioxane, methyl ethyl ketone, ethylene glycol, ethylene glycol monobutyl ether, 2-methoxypropanol, 2-butoxypropanol, diethylene glycol monobutyl ether, butyl diglycol, N-methylpyrrolidone, ethylene carbonate, and propylene carbonate.

[0043] The castor oil-based polyols include castor oil and its derivatives, specifically monoglycerides and diglycerides of castor oil fatty acids, and mixtures thereof. By including a castor oil-based polyol in the film-forming resin (a), the viscosity of the base resin can be reduced, making it easier to thoroughly mix the base resin with the curing agent.

[0044] Examples of low molecular weight polyols for the coating film-forming resin (a) include ethylene glycol, propylene glycol, butane glycol, hexanediol, methylpentanediol, neopentyl glycol, polyethylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerin, pentaerythritol, dipentaerythritol, sorbitol, inositol, mannitol, glucose, and fructose.

[0045] The polyol preferably contains a castor oil-based polyol, and the content of the castor oil-based polyol in the polyol is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, for example, 100% by mass or less.

[0046] The content of the polyol in the coating film-forming resin (a) is preferably 85% by mass or more, more preferably 80% by mass or more, even more preferably 70% by mass or more, and is preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 93% by mass or less.

[0047] The polyamine may be any compound having two or more amino groups in the molecule, and examples thereof include aromatic polyamines in which two or more amino groups are substituted on the aromatic ring of an aromatic hydrocarbon compound; aliphatic polyamines in which two or more amino groups are substituted on an aliphatic hydrocarbon compound; and alicyclic polyamines in which two or more amino groups are substituted on an alicyclic hydrocarbon compound, with aromatic polyamines being preferred.

[0048] In the present disclosure, the aromatic hydrocarbon compound in the aromatic polyamine includes compounds consisting of only an aromatic ring; compounds in which a substituent such as an alkyl group, an alkoxy group, an alkylthio group, or a halogen atom is bonded to an aromatic ring; and compounds in which two or more aromatic rings are bonded to a linking group such as an alkylene group, an oxygen atom, or -CO-. The number of carbon atoms in the alkyl group, alkoxy group, or alkylthio group as the substituent is, for example, 1 to 10, preferably 1 to 5, and the number of carbon atoms in the alkylene group as the linking group is, for example, 1 to 10, preferably 1 to 5. The alkyl group, alkoxy group, alkylthio group, and alkylene group may be linear or branched. Examples of the halogen atom as the substituent include a chlorine atom.

[0049] Examples of the aromatic polyamines include diaminotoluenes (e.g., 2,4-diaminotoluene, 2,6-diaminotoluene, 3,4-diaminotoluene, and phenylenediamine), diethyldiaminotoluenes (e.g., 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, and 2,4-diethyl-6-methyl-1,3-diaminobenzene; DETDA), 4,4'-diamino-3,3'-dichlorodiphenylmethane, and 4,4'-diamino-3,3'-diethyl-5,5'-dimethylphenylmethane ( Examples of aromatic diamines include aromatic diamines such as MEDDM, 1,3,5-triethyl-2,6-diaminobenzene, 4,4'-diaminodiphenylmethane, 3,5,3',5'-tetraethyl-4,4'-diaminodiphenylmethane, 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine, bisaminophenylfluorene, diaminodiphenyl ether, diaminonaphthalene, and diaminobenzophenone; and aromatic triamines such as triaminobenzene (1,3,5-triaminobenzene, 1,2,4-triaminobenzene).

[0050] Commercially available aromatic polyamines may be used. Examples of commercially available aromatic polyamines include diaminodiphenylmethane-based amines (Iharacuramine MT, Curehard-MED, both manufactured by Kumiai Chemical Co., Ltd.), phenylenediamine-based amines (Ethacure 100, manufactured by Albemare Corporation), bisaminophenylfluorene-based amines (BAFL, manufactured by JFE Chemical Corporation), diaminodiphenyl ether-based amines (4,4'-diaminodiphenyl ether, manufactured by JFE Chemical Corporation), diaminonaphthalene-based aromatic polyfunctional amines, and diaminobenzophenone-based aromatic polyfunctional amines.

[0051] The content of the aromatic polyamine in the polyamine is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, and is, for example, 100% by mass or less.

[0052] The number of amino groups contained in the polyamine is 2 or more, preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less per molecule.

[0053] The amine value of the polyamine may be preferably 100 mgKOH / g or more, more preferably 200 mgKOH / g or more, and may be 1,200 mgKOH / g or less, more preferably 800 mgKOH / g or less. Having the amine value of the polyamine within this range facilitates the formation of a tough coating film and shortens the curing time. Furthermore, the pot life of the first coating composition can be adjusted, improving workability during application. In the present disclosure, the amine value refers to the solid content amine value, and can be measured in accordance with the provisions of JIS K 7237.

[0054] The content of the polyamine is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the polyol.

[0055] The film-forming resin (a) preferably contains a polyol and a polyamine, and the total content of the polyol and the polyamine in the film-forming resin (a) is preferably 80% by mass or more, more preferably 90% by mass or more, and preferably 100% by mass or less.

[0056] In one embodiment, the film-forming resin (a) may include an epoxy resin, a urethane resin, or a urea resin.

[0057] The base material may further contain a pigment. Examples of the pigment include inorganic pigments and organic pigments. The pigment may be in the form of solid particles or hollow particles.

[0058] Examples of the inorganic pigments include carbonates, titanium oxide, zinc oxide, precipitated barium sulfate, talc, silica, zirconia, alumina silicate, zirconia silicate, kaolin, bentonite, smectite, glass flakes (silica fillers), iron oxide, acicular titanium oxide, anthraquinone, bismuth vanadate, carbon black, composite oxide pigments, seashell chalk, eggshell calcium, etc. Examples of the organic pigments include quinophthalone pigments, benzimidazolone pigments, isoindoline pigments, isoindolineone pigments, dioxazine pigments, phthalocyanine pigments (copper phthalocyanine pigments, chlorinated copper phthalocyanine, brominated copper phthalocyanine, etc.), indanthrene pigments, perylene pigments, diketopyrrolopyrrole pigments, azo pigments, azomethine azo pigments, quinacridone pigments, aniline pigments, etc.

[0059] In one embodiment, the pigment may contain an extender pigment. The extender pigment may contain, for example, at least one selected from the group consisting of carbonates, titanium oxide, zinc oxide, precipitated barium sulfate, talc, silica, zirconia, alumina silicate, zirconia silicate, kaolin, seashell chalk, and eggshell calcium, and particularly at least one selected from the group consisting of carbonates, titanium oxide, and talc. By containing such a pigment, a coating film formed using the first coating composition of the present disclosure can exhibit a white color and can be used to form white lines, etc.

[0060] The pigment may contain a heat-shielding pigment. When the first coating composition of the present disclosure contains a heat-shielding pigment, the resulting coating film has high solar reflectance and can exhibit a heat-shielding function, which is effective in countering the heat island effect. The first coating composition can also be classified as a solar reflectance coating for roofs as specified in JIS K 5675.

[0061] In the present disclosure, a heat-shielding pigment refers to a pigment that does not absorb light in the near-infrared wavelength region (wavelengths of 780 nm to 2,500 nm) or has low absorptance of light in the near-infrared wavelength region (wavelengths of 780 nm to 2,500 nm). The absorptance of light in the near-infrared wavelength region can be evaluated, for example, by solar absorptance in accordance with JIS R 3106. The solar absorptance of the heat-shielding pigment may be, for example, 60% or less, and may vary depending on the color of the heat-shielding pigment; for example, it may be 30% or less for yellow or red heat-shielding pigments, and 15% or less for white heat-shielding pigments.

[0062] The heat-shielding pigment may be a white heat-shielding pigment, a red heat-shielding pigment, a blue heat-shielding pigment, a yellow heat-shielding pigment, a black heat-shielding pigment, etc. The black heat-shielding pigment may be a pigment toned by mixing at least one selected from chromatic heat-shielding pigments such as a red heat-shielding pigment, a blue heat-shielding pigment, and a yellow heat-shielding pigment with an optional pigment other than the heat-shielding pigment.

[0063] The white heat-shielding pigment may be titanium oxide, and an example of a commercially available product thereof is Typec CR-97 (manufactured by Ishihara Sangyo Kaisha).

[0064] Commercially available examples of the red heat-shielding pigment include Fastogen Super Magenta RH (manufactured by DIC Corporation), Fastogen Super Red 7100Y (manufactured by DIC Corporation), Rubicron Red 400RG (manufactured by Tosoh Corporation), and Pacific Red 2020 (manufactured by BASF). These may be used alone or in combination of two or more.

[0065] Commercially available examples of the blue heat-shielding pigment include Dipyroxide Blue #9453 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Fastogen Blue 5485K (manufactured by DIC Corporation), Fastogen Blue RSKE (manufactured by DIC Corporation), Cyanine Blue 5240KB (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and Lionol Blue SPG-8 (manufactured by Toyocolor Co., Ltd.) These may be used alone or in combination of two or more.

[0066] Examples of commercially available yellow heat-shielding pigments include Symuler Fast Yellow 4192 (manufactured by DIC Corporation), Syco Pearl Yellow L-1110 (manufactured by BASF), and Irgacolor Yellow 2GLMA (manufactured by BASF). These may be used alone or in combination of two or more.

[0067] Examples of the black heat-shielding pigment include azomethine azo pigments, perylene pigments, aniline pigments, and calcined composite oxide pigments. These may be used alone or in combination of two or more.

[0068] The heat-shielding pigments are only examples, and the pigments exemplified above may also function as heat-shielding pigments. In such cases, these "pigments" may be used as heat-shielding pigments.

[0069] One or more of the pigments can be used. When two or more pigments are used, the pigments may be mixed in advance before preparing the main agent and the first coating composition, or primary color main agents or primary color first coating compositions containing only the respective pigments may be prepared, and then the primary color main agents or primary color first coating compositions may be mixed respectively.

[0070] The average particle size (D50) of the pigment is the average particle size (D50) of dispersed particles of the pigment, and is preferably 50 μm or less, more preferably 35 μm or less, and may be, for example, 0.2 μm or more, or even 3 μm or more. The average particle size (D50) of the pigment can be measured using a particle size measuring device such as a laser diffraction / scattering particle size distribution measuring device (Microtrac MT3300EX II, manufactured by Microtrac-Bell). In the present disclosure, D50 is the particle size at which the total volume of particles, accumulated from the smallest particle size to a certain particle size in the particle size distribution, is 50% when expressed as a percentage of the total volume of the particles.

[0071] The content of the pigment is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 12 parts by mass or more, and preferably 55 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, per 100 parts by mass of the solids content of the first coating composition. By having the pigment content within this range, the viscosity of the base agent becomes appropriate, the mixability of the base agent and the curing agent is good, and the reaction between the film-forming resin and the curing agent is not inhibited, resulting in the formation of a coating film with excellent strength. Furthermore, the tinting power of the first coating composition is also good.

[0072] The first coating composition may contain a filler (particles composed of the same material as general pigments but with a larger particle size than general pigments). Examples of such particles include ceramic beads such as SiO2, Al2O3, ZrO2, 3Al2O3·2SiO2, and zirconia silicate, and glass beads. The average particle size (D50) of the filler is preferably 500 μm or less, more preferably 200 μm or less, and preferably greater than 50 μm, more preferably 60 μm or more. The shape of the filler may be particulate, spherical, hollow spherical, fibrous, or granular.

[0073] The base agent may further contain an organometallic catalyst. By including a metal catalyst, it is easy to adjust the reactivity of the coating composition, even when the reactivity between the base agent and the curing agent is low. Furthermore, it is possible to suppress the reaction between the curing agent and water, thereby suppressing foaming in the first coating composition. Furthermore, it is possible to improve workability during coating.

[0074] The organometallic catalyst may be any catalyst capable of contributing to the reaction between the base resin and the curing agent. In one embodiment, the organometallic catalyst may be an ester compound of tin, lead, bismuth, zinc, titanium, or the like. Specific examples include dibutyltin dilaurate, bismuth tris(2-ethylhexanoate), lead octoate, and bismuth octoate. Tin esters and / or bismuth esters are preferred as the organometallic catalyst.

[0075] The content of the organometallic catalyst may be, for example, 0.0 to 2% by mass in the solid content of the base agent, from the viewpoint of the reactivity between the base agent and the curing agent.

[0076] The base agent may further contain a dehydrating agent, which can further suppress the generation of carbon dioxide due to the reaction between the moisture adhering to the coated object and the curing agent described below, thereby suppressing unevenness and porosity on the resulting coating film.

[0077] The dehydrating agent is not particularly limited, and examples thereof include synthetic zeolite molecular sieves, calcium sulfate, calcium oxide, and the like.

[0078] The content of the dehydrating agent may be, for example, 0.3 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the solid content of the coating composition, from the viewpoint of sufficiently dehydrating the water that may be contained in the coating composition and suppressing foaming.

[0079] The base material may further contain additives such as aggregates, antifoaming agents, leveling agents, anti-sagging agents, surface conditioners, viscosity adjusters, dispersants, light stabilizers, antioxidants, ultraviolet absorbers, and waxes.

[0080] The base resin can be prepared by mixing the film-forming resin (a) with, as needed, a pigment, an organometallic catalyst, a dehydrating agent, additives, etc. A mixer such as a roll mill, a paint shaker, a pot mill, a disperser, or a sand grind mill may be used for the mixing.

[0081] (solvent-free hardener) The curing agent comprises a compound (curing agent (b)) having two or more groups in its molecule that can react with the reactive groups of the film-forming resin (a) (preferably groups having active hydrogen atoms). Examples of groups that can react with the reactive groups of the film-forming resin (a) include isocyanate groups, and the curing agent preferably comprises a polyisocyanate. Without being bound by any particular theory, it is believed that when the curing agent comprises a compound having an isocyanate group, the isocyanate groups are more likely to interact with the silanol groups on the surface of the silica microparticles contained in the second coating composition, thereby promoting the fixation of the silica microparticles to the surface of the first coating film.

[0082] Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as cyclohexane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate and isophorone diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate; and polymers (biuret, isocyanurate, allophanate, adduct) of the aliphatic diisocyanates, alicyclic diisocyanates and aromatic diisocyanates. The polyisocyanates also include modified polyisocyanates in which some of the isocyanate groups have been modified with polyol or the like.

[0083] The polyisocyanates may be used alone or in combination of two or more kinds.

[0084] In one embodiment, the polyisocyanate preferably contains an aliphatic polyisocyanate or an alicyclic polyisocyanate, more preferably an aliphatic polyisocyanate, and even more preferably hexamethylene diisocyanate or a hexamethylene diisocyanate polymer. This can improve the weather resistance of the coating film and suppress discoloration. The total content of the aliphatic polyisocyanate and the alicyclic polyisocyanate in the polyisocyanate is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less.

[0085] The content of the polyisocyanate in the curing agent is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less.

[0086] The curing agent may further contain the additives and the like.

[0087] The molar ratio [NCO / H] of the isocyanate group contained in the curing agent to the group having an active hydrogen atom contained in the base resin may be, for example, 0.5 or more, further 0.7 or more, particularly 0.8 or more, and may be, for example, 2.0 or less, further 1.7 or less, particularly 1.6 or less, and particularly 1.55 or less. When the hardness ratio [NCO / H] is within the above range, the curing reaction between the base resin and the curing agent proceeds sufficiently, making it easy to obtain a tougher coating film, and the resulting coating film may have good abrasion resistance and water resistance.

[0088] (Aggregate spreading process) After the first coating film forming step and before the second coating film forming step, a step of scattering aggregate on the surface of the first coating film (aggregate scattering step) may be included.

[0089] By including the aggregate scattering step, the resulting coating film can be imparted with anti-slip properties.

[0090] As the aggregate, artificial aggregates produced using one or more materials selected from glass flakes, glass beads, expanded shale, fly ash, coal ash, clay, expanded slate, ready-mixed concrete sludge, paper sludge, waste foundry sand, perlite, fireproof stone, and obsidian as the main raw material; natural aggregates such as volcanic gravel, etc. can be used as appropriate.

[0091] The particle size distribution of the aggregate can be selected appropriately, and it may be coarse aggregate containing particles that can pass through a sieve with 5 mm openings at 85% or more by mass, or fine aggregate containing particles that can pass through a sieve with 10 mm openings at 100% by mass and particles that can pass through a sieve with 5 mm openings at 85% or more by mass.

[0092] The aggregate may be dispersed alone, or a dispersion liquid may be prepared by dispersing the aggregate with a dispersion resin and a dispersion medium, if necessary, and then dispersed. The dispersion resin may be an acrylic resin, a polyester resin, a urethane resin, or the like, and the dispersion medium may be water or a hydrophilic solvent, as described below, as appropriate.

[0093] The method for scattering the aggregate is not particularly limited, and any method used in the relevant field can be used as appropriate.

[0094] The amount of the aggregate to be scattered is not particularly limited, and can be adjusted appropriately within a range in which at least a portion of the first paint film is exposed.

[0095] (Second paint film formation process) Next, a second coating composition is applied onto the first coating film immediately after the first coating composition is applied to the substrate and before the first coating film has hardened and dried, thereby forming a laminated coating film consisting of the first and second coating films. By applying the second coating composition within this time period, a matte coating film can be efficiently formed, and a coating film with good abrasion resistance and water resistance and a long service life can be formed.

[0096] In this disclosure, the term "hardened and dried state" refers to the hardened and dried state specified in JIS K 5600-1-1, and specifically means "a state in which, when the center of the coating surface is firmly pinched between the thumb and index finger, no fingerprint indentation is left on the coating surface, no movement of the coating film is felt, and when the center of the coating surface is rapidly and repeatedly rubbed with the fingertips, no scratches are left on the coating surface."

[0097] The method for applying the second coating composition is not particularly limited, and can be any commonly used application method such as dipping, brushing, roller, roll coater, spray (air spray, airless spray), curtain flow coater, roller curtain coater, die coater, slit coater, or flow coating, and can particularly include spray coating, slit coater coating, and flow coating.

[0098] In one embodiment, the coating method is preferably spray coating, and more preferably airless spray coating, which allows the use of coating equipment normally used in road paving work.

[0099] When spray coating is performed, the discharge volume (flow rate) and discharge pressure (atomization pressure) are not limited. Furthermore, the nozzle / head shape and diameter of the coating device are not particularly limited. In one embodiment, the coating conditions are a discharge volume of 0.02 L / min to 20 L / min, a discharge pressure of 0.2 MPa to 20 MPa, and a gun distance of 10 mm to 1 m. The discharge time, number of reciprocating strokes, pattern, movement time, and the like can also be appropriately set within a range that does not impair the effects obtained by the present disclosure.

[0100] The amount of the second coating composition to be applied can be adjusted so that the film thickness after drying and curing when applied to a smooth surface is preferably 0.1 to 50 μm, more preferably 1 to 30 μm, and even more preferably 1 to 10 μm. The amount of the second coating composition to be applied when applied to a smooth surface is, for example, 10 to 100 g / m 2The second coating composition may be applied multiple times as needed. By applying an amount within the above range, a matte coating film can be efficiently formed, and a coating film with good abrasion resistance and water resistance and a long service life can be formed.

[0101] When the second coating film forming step is carried out, the temperature may be, for example, 0° C. or higher and 40° C. or lower, and the humidity may be 0% or higher and 70% or lower.

[0102] (Second paint composition) The second coating composition used in the second coating film forming step contains silica fine particles and a hydrophilic medium.

[0103] The second coating composition contains silica fine particles, which allows for efficient formation of a matte coating film and a coating film with good abrasion resistance and water resistance and a long service life. The silica content in the silica fine particles is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less.

[0104] The silica fine particles may be surface-treated with a silane coupling agent or the like.

[0105] The average primary particle diameter of the silica fine particles may be, for example, 1 nm or more, further 3 nm or more, particularly 10 nm or more, and may be, for example, 10 μm or less, further 5 μm or less, particularly 1 μm or less, and particularly 500 nm or less. When the average primary particle diameter of the silica fine particles is within the above range, they aggregate appropriately upon drying of the hydrophilic medium, and the matte properties of the resulting coating film are improved.

[0106] In the present disclosure, the average primary particle size of the silica fine particles can be measured by observation with an electron microscope.

[0107] The silica fine particles may be wet-process silica fine particles obtained by reacting a silica precursor such as an alkali sodium silicate or a silicate ester in water to produce silica, and then stabilizing the reaction solution by adjusting the pH to an acidic or basic state. The reaction solution may further contain a hydrophilic solvent, as described below. Alternatively, the silica fine particles may be dry-process silica particles obtained by combustion hydrolysis of silicon tetrachloride.

[0108] The pH of the reaction solution when stabilizing in the acidic range is, for example, 2.0 to 5.0, preferably 2.0 to 4.0. For stabilization in the acidic range, an acid such as hydrochloric acid, sulfuric acid, phosphoric acid, or acetic acid can be used. When stabilizing in the acidic range, metals (particularly alkali metals) that may be contained in the silica precursor may be removed.

[0109] The pH of the reaction solution when stabilizing in the basic range is, for example, 8.0 to 11.0, preferably 8.5 to 10.5. Examples of the stabilization in the basic range include ammonia; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; and alkaline earth metal hydroxides such as calcium hydroxide.

[0110] The content of silica microparticles in the second coating composition is preferably 0.1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 25% by mass or less.

[0111] Examples of the hydrophilic medium include water; a hydrophilic solvent; and a mixture of water and a hydrophilic solvent. In the present disclosure, the hydrophilic solvent refers to a solvent having a water solubility of 50 g / L or more at 20°C. Specific examples include alcohol solvents such as methanol, ethanol, propanol, butanol, 3-methoxybutanol, and 3-methyl-3-methoxybutanol; and ketone solvents such as acetone and methyl ethyl ketone. These hydrophilic solvents may be used alone or in combination of two or more. The hydrophilic medium preferably contains at least water. The water content of the hydrophilic medium may be, for example, 30% by mass or more, preferably 50% by mass or more, and particularly 80% by mass or more, with the upper limit being 100% by mass. By keeping the water content within the above range, odor can be reduced and the safety of painting workers can be ensured.

[0112] The content of the hydrophilic medium in the second coating composition is preferably 60% by mass or more, more preferably 75% by mass or more, and preferably 99.9% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0113] In one embodiment, the second coating composition may contain a photocatalyst. By including a photocatalyst in the second coating composition, a photocatalytic function, i.e., a strong oxidizing effect, is exerted on the surface of the laminate coating film, which has the advantage of contributing to the removal of harmful substances and pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) from the atmosphere. Examples of the photocatalyst include titanium oxide, zinc oxide, and tungsten oxide, with titanium oxide being preferred. The photocatalyst may be titanium oxide or the like to which metals and / or oxides such as Ag and Cu have been added or supported, or may be coated with silica, porous calcium phosphate, or the like. The content of the photocatalyst is preferably 0.5 to 5.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, per 1 part by mass of the silica fine particles.

[0114] The second coating composition may further contain additives such as pigments, aggregates, film-forming aids, drying retarding aids, viscosity adjusters, preservatives, mildew inhibitors, antiseptics, antifoaming agents, light stabilizers, antioxidants, ultraviolet absorbers, and pH adjusters.

[0115] The pH of the second coating composition may be 2.0 to 6.0, 2.0 or more but less than 6.0, 2.0 to 5.0, or 2.0 to 4.0 when used in an acidic range. Also, it may be 8.0 to 11.0 or 8.5 to 10.5 when used in a basic range. Furthermore, it may be 6.0 to 8.0 when used in a neutral range.

[0116] The second coating composition can be produced by mixing silica fine particles, a hydrophilic medium, and the additives used as needed. When wet silica fine particles are used as the silica fine particles, the dispersion (suspension) of silica fine particles stabilized in the reaction solution in the acidic or basic range may be used as is.

[0117] As the silica fine particles or the dispersion (suspension) of silica fine particles, commercially available products may be used. Examples of the commercially available products include Snowtex 30, Snowtex 50-T, Snowtex N, Snowtex O, Snowtex C, Snowtex AK, Snowtex 30L, Snowtex N-40, Snowtex O-40, Snowtex OL, Snowtex MP-1040, Snowtex MP4540-M, Snowtex XS, Snowtex S, Snowtex ZL, Snowtex YL, methanol silica sol, MA-ST-M (methanol-dispersed silica sol), IPA-ST (isopropyl alcohol-dispersed silica sol), IPA-ST-ZL (isopropyl alcohol-dispersed silica sol), MEK-ST-40 (methyl ethyl ketone-dispersed silica sol), MEK-ST-L (methyl ethyl ketone-dispersed silica sol), MIBK-ST (methyl isobutyl ketone-dispersed silica sol), MIBK-ST-L (methyl isobutyl ketone-dispersed silica sol) (all manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20, 30, 50, 20A, 30A, 20Q (ADEKA) Cataroid 350, 20H, 30, 30H, 40, 50, SA, SN (manufactured by JGC Catalysts and Chemicals Co., Ltd.), Silicadol 20, 20A, 30, 40 (manufactured by Nippon Chemical Industry Co., Ltd.), Cyton (registered trademark) X-30, D-30, T-40 (manufactured by DA Nanomaterials), Ludox (registered trademark) SM-30, L, HS-30, HS-40, TM, AM (manufactured by W.R. Grace Co., Ltd.), Examples include Nalcoag 1115, 1130, 1030, 1140, 1050, and 2327 (manufactured by Nalco Corporation). These may be used alone or in combination of two or more.

[0118] (hardening process) In the curing step, the first coating film and the second coating film formed on the first coating film are cured to form a matte coating film.

[0119] Without being bound by any particular theory, it is believed that during the curing process, as the hydrophilic medium derived from the second coating composition dries, the silica microparticles become more likely to aggregate, and at the same time, the hardening of the first coating film progresses. As a result, the unevenness caused by the aggregation of the silica microparticles is fixed on the hardened first coating film, making it possible to form a coating film that has a matte finish and is also abrasion-resistant.

[0120] The curing method is not particularly limited, and may be room temperature curing or forced curing using an infrared heater, burner, etc. depending on the ambient environment such as air temperature and the temperature of the object to be coated.

[0121] In one embodiment, the second coating film may be heated or kept at a temperature of 10°C or higher and 60°C or lower in a state where it has been formed.

[0122] In one embodiment, the coating film produced by the manufacturing method of the present disclosure is a pavement coating film, particularly a road marking coating film and / or a road heat-insulating coating film. Also, in an embodiment, the coating film of the present disclosure is a white road marking coating film and / or a road heat-insulating coating film, which can be used, for example, for white lines on road surfaces.

[0123] Multilayer coating films produced by the production method of the present disclosure are also included within the technical scope of the present invention. The multilayer coating film comprises a first coating film and a second coating film provided on the first coating film.

[0124] The first coating film corresponds to the cured product of the first coating composition (i.e., the reaction product of the base resin and the curing agent) and contains a resin having a urethane bond and / or a urea bond. The resin having a urethane bond and / or a urea bond is preferably a urethane resin and / or a urea resin.

[0125] The content of the resin having a urethane bond and / or a urea bond in the first coating film is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less.

[0126] The thickness of the first coating film is preferably 50 μm or more, more preferably 150 μm or more, and is preferably 2,000 μm or less, more preferably 1,500 μm or less.

[0127] The second coating film corresponds to a cured product of the first coating composition, and at least a portion of the first coating film and at least a portion of the second coating film are bonded by a chemical bond. Without being bound by any particular theory, when the second coating composition is applied to the uncured first coating film, the first coating film may contain unreacted isocyanate groups derived from the curing agent. It is believed that chemical bonds can be formed by the interaction of these isocyanate groups with silanol groups on the surface of the silica microparticles. Examples of such chemical bonds include hydrogen bonds and covalent bonds.

[0128] The second coating film contains silica. The silica content in the second coating film is 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less.

[0129] The thickness of the second coating film is preferably 0.1 to 50 μm, more preferably 1 to 30 μm, and still more preferably 1 to 10 μm.

[0130] In one embodiment, an aggregate may be present between the first coating film and the second coating film, and at least a part of the first coating film and at least a part of the second coating film may be in direct contact with each other.

[0131] The laminated coating film preferably has a heat shielding function. The presence or absence of the heat shielding function can be determined after calculating the "solar reflectance" and "lightness" of the laminated coating film in accordance with JIS K 5675.

[0132] The solar reflectance is calculated from the spectral reflectance obtained in a specified wavelength range and indicates the ratio of the reflected light beam from the coating film to the solar radiation incident on the coating film surface. The solar reflectance is determined in accordance with JIS K 5602 in the near-infrared wavelength range (wavelength: 780 nm to 2,500 nm) and the total wavelength range (wavelength: 300 nm to 2,500 nm).

[0133] The lightness is calculated in accordance with 3.2 of JIS K 5600-4-4 and JIS K 5600-4-5.

[0134] When the lightness (L*) calculated for the laminated coating film is 40.0 < L* < 80.0, the solar reflectance (ρIR) value in the near-infrared wavelength range is preferably not less than the value of the lightness (L*). When the lightness (L*) calculated for the laminated coating film is 40.0 or less, the solar reflectance (ρIR) in the near-infrared wavelength range is preferably 40.0% or more. If the solar reflectance is within the above range, the laminated coating film can have a heat shielding function.

Examples

[0135] The present disclosure will be described more specifically by the following examples, but the present disclosure is not limited thereto.

[0136] Preparation of the first coating composition [Solvent-free main agent composition] The components contained in the solvent-free base composition used in the first coating composition are as follows. Paint film forming resin : Polyol 1: URIC-H368 (Ito Oil Mills, castor oil-based polyol); solid content hydroxyl value: 195 mg KOH / g, number average molecular weight: approximately 700 Polyol 2: GP-400 (Sanyo Chemical Industries, Ltd., polyether polyol: solid content hydroxyl value: 400 mg KOH / g) Polyamine 1: Ethacure 100 (manufactured by Albemarle, aromatic polyfunctional amine (DETDA)); solids amine value: 629 mg KOH / g others : Organometallic catalyst: TVS Tin Laur (manufactured by Nitto Kasei Co., Ltd., dibutyltin laurate (DBTL)) Dehydrating agent: Zeolum A4 (Tosoh Corporation, zeolite) pigment : Pigment 1: Typaque CR-97 (manufactured by Ishihara Sangyo Kaisha, titanium dioxide) Pigment 2: Chromofine A-1103 (Dainichiseika Color & Chemicals Mfg. Co., Ltd., azomethine azo pigment)

[0137] The solvent-free base compositions containing the above ingredients were blended in the amounts (parts by mass) shown in Table 1 and mixed using a disper to prepare solvent-free base compositions.

[0138] [Solvent-free curing agent composition] The solvent-free curing agent composition used in the first coating composition had the following components, and was used as is as the solvent-free curing agent composition. Polyisocyanate 1: Coronate HXLV (Tosoh Corporation, aliphatic isocyanate compound; hexamethylene diisocyanate trimer); NCO content: 23.2% by mass Polyisocyanate 2: Millionate MR-200 (manufactured by Tosoh Corporation, aromatic isocyanate compound; polymeric MDI); NCO content: 31% by mass

[0139] Preparation of the second coating composition [Second paint composition] The second coating composition contains the following components: Silica microparticles 1: Snowtex O (Nissan Chemical Industries, Ltd., silica sol); average primary particle diameter: 12 nm, solid content: 20% by mass, hydrophilic medium: water Silica microparticles 2: Snowtex N (Nissan Chemical Industries, Ltd., silica sol); average primary particle diameter: 12 nm, solid content: 20% by mass, hydrophilic medium: water Silica microparticles 3: IPA-ST (Nissan Chemical Industries, Ltd., isopropanol silica sol); average primary particle size: 12 nm, solid content: 30% by mass, hydrophilic medium: isopropanol (water solubility: 1,000 g / L water) Silica microparticles 4: MA-ST-M (Nissan Chemical Industries, Ltd., methanol silica sol); average primary particle diameter: 12 nm, solid content: 30% by mass, hydrophilic medium: methanol (water solubility: 1,000 g / L water) Silica microparticles 5: TOL-ST (Nissan Chemical Industries, Ltd., toluene silica sol; average primary particle diameter: 12 nm, solid content: 40% by mass), medium: toluene (water solubility: 0.5 g / L water) Silica microparticles 6: Sicastar 43-02-204 (manufactured by Corefront, COOH-modified silica particles); average primary particle diameter: 20 μm, solid content: 100% by mass Hydrophilic medium: distilled water Photocatalyst: Tersus IN (Shin-Etsu Chemical Co., Ltd., photocatalytic coating liquid: ultraviolet and visible light responsive titanium oxide); solid concentration: 0.66% by mass (including titanium oxide concentration: 0.33% by mass); medium: water

[0140] The second coating composition containing the above ingredients was blended in the amounts (parts by mass) shown in Table 1 and mixed using a disper to prepare the second coating composition. However, the value for silica fine particles indicates the solid content parts by mass.

[0141] Example 1 The solvent-free base composition and the solvent-free curing agent composition were mixed using a disper immediately before coating so that the molar ratio [NCO / H] of the isocyanate group contained in the solvent-free curing agent to the group containing an active hydrogen atom contained in the solvent-free base composition was 1.0 (first coating composition). Then, using a 30 mil doctor blade, the composition was applied to a substrate (SPCC steel plate) so that the film thickness after curing was 200 μm, and a test plate with an uncured first coating film was obtained.

[0142] Next, the obtained test plate was cured at 23°C (ambient temperature) for 30 minutes for the curing time shown in Table 1, and then the second coating composition was applied by airless spray coating under the coating conditions below so that the film thickness after drying would be 5 μm, forming an uncured second coating film. Thereafter, the first coating film and the second coating film were dried and cured under conditions of 23°C for 72 hours, yielding a test plate with a multilayer coating film.

[0143] <Airless spray painting conditions> Discharge: 3 turns back from fully closed Air pressure: 0.3 MPa Distance from workpiece to gun: 30cm

[0144] <Evaluation items> (Odor) When the second coating compositions obtained in the Examples and Comparative Examples were applied to test panels having the first coating film as described above, the odor intensity was evaluated sensorily based on a 6-point odor intensity rating system. The evaluation criteria were as follows: A score of 3 or higher was considered a pass. 0 points: Odorless 1 point: barely detectable smell 2 points: A weak smell that you can identify 3 points: Easily detectable odor 4 points: Strong odor 5 points: Strong odor

[0145] (gloss value) The gloss value at 60 degrees of the coating film surface of the test plates obtained in the examples and comparative examples was measured using a gloss meter (Micro-Tri-Gloss, manufactured by BYK Gardner). The evaluation criteria are as follows: ○: Gloss value is less than 50 △: Gloss value is 50 or more and less than 70 ×: Gloss value is 70 or more

[0146] (water resistance) Half of the test plates obtained in the Examples and Comparative Examples were immersed in water at 23°C for 30 minutes, then the test plates were removed and the immersed portion was rubbed back and forth 10 times with a gauze lightly pressed with the index finger under running water. The gloss values ​​at 60° were then measured for both the immersed and non-immersed portions. The evaluation criteria were as follows: ○: Gloss value is less than 50 △: Gloss value is 50 or more and less than 70 ×: Gloss value is 70 or more

[0147] (wear resistance) The abrasion resistance of the coating film of the test plates obtained in the Examples and Comparative Examples was evaluated using a stationary (torsion) testing machine AI-900 (manufactured by Iwata Kogyosho Co., Ltd.) Specifically, a tire was brought into contact with the coating surface of the test plate, and the tire was rotated while a load was applied to the contact area in a direction perpendicular to the coating surface, to evaluate the abrasion resistance of the coating film. The test conditions were test temperature: 23°C, load: 50 kgf, rotation speed: 10 rpm, test time: 120 minutes, and the tire used was a pneumatic tire with a diameter of 220 mm, width of 65 mm, and air pressure of 2.0 x 100 kPa. The evaluation criteria are as follows: ○: Gloss value is less than 50 △: Gloss value is 50 or more and less than 70 ×: Gloss value is 70 or more

[0148] (NOx decomposition) The test plates obtained in Examples 32 and 1 were evaluated for NOx decomposition ability according to the method specified in JIS R 1701-1. That is, one test plate cut to 50 × 100 mm was placed in a reaction vessel described in JIS R 1701-1. Air (25 °C, 50% RH) containing 1.0 ppm NO gas was mixed into the light-shielded reaction vessel and supplied at a flow rate of 1.5 L / min for 20 minutes. Thereafter, while the air was still being introduced, the intensity was set at 3 mW / cm. 2 The reaction vessel was then irradiated with ultraviolet light for 20 minutes using a black light, and the reaction vessel was then again shielded from light while the air was introduced. The amount of NOx decomposition was calculated from the NO and NO2 concentrations before and after black light irradiation according to the following formula. The evaluation criteria are as follows: NOx decomposition amount (ppb) = [NO (after irradiation) - NO (during irradiation)] - [NO2 (during irradiation) - NO2 (after irradiation)] The black light used was (bright line spectrum: 351 nm), and the test plate was pretreated by irradiating it with the black light for 12 hours or more before carrying out the NOx decomposition test. ○: NOx decomposition amount is 0.5 ppb or more. ×: The amount of NOx decomposed is less than 0.5 ppb.

[0149] <Examples 2 to 33 and Comparative Examples 1 to 5> Coating films were formed in the same manner as in Example 1, except that they were formed under the conditions shown in Table 1, and evaluations were carried out for odor, gloss value, water resistance, and abrasion resistance. Examples 32 and 33 were also evaluated for NOx decomposition ability. Note that for NOx decomposition ability, the test plate obtained in Example 1, to which no photocatalyst was added, was used as a standard.

[0150] The evaluation results for odor, gloss value, water resistance, and abrasion resistance are shown in Tables 1A to 1H.

[0151] [Table 1A]

[0152] [Table 1B]

[0153] [Table 1C]

[0154] [Table 1D]

[0155] [Table 1E]

[0156] [Table 1F]

[0157] [Table 1G]

[0158] [Table 1H]

[0159] Examples 1 to 32 are examples of the present invention, and the obtained multilayer coating films had good matte properties, and the obtained coating films also had good water resistance and abrasion resistance.Furthermore, odor during application was suppressed.

[0160] Furthermore, when the NOx decomposition ability was evaluated for Examples 32 and 1, the NOx decomposition ability of Example 32, in which a photocatalyst was added, was evaluated as ○, while the NOx decomposition ability of Example 1, in which a photocatalyst was not added, was evaluated as ×.

[0161] Comparative Example 1 is an example that does not include the second coating step, and the gloss (mattness) of the resulting multilayer coating film was not fully satisfactory. Comparative Example 2 is an example in which the second coating composition did not contain silica fine particles, and the gloss (mattness) of the resulting multilayer coating film was not fully satisfactory. Comparative Example 3 is an example in which the second coating composition did not contain silica fine particles, and the gloss (mattness) of the resulting multilayer coating film was not fully satisfactory, and the odor was also unsatisfactory. For Comparative Examples 1 to 3, the gloss (mattness) evaluation was poor, so the water resistance and abrasion resistance of the coating film were not evaluated. Comparative Example 4 is an example in which the first coating film reached a cured and dried state before the second coating composition was applied, and the water resistance and abrasion resistance of the resulting multilayer coating film were not fully satisfactory. Comparative Example 5 is an example in which the second coating composition did not contain a hydrophilic medium but contained toluene, and the odor was not satisfactory.

Claims

1. A method for producing a coating film, comprising: A step of applying the first coating composition to an object to be coated to form a first coating film; a step of applying a second coating composition onto the first coating film immediately after the first coating composition is applied to the substrate and before the first coating film is cured and dried, thereby forming a laminated coating film in which the first coating film and the second coating film are laminated; and A step of curing the laminated coating film to form a coating film, the first coating composition is a two-component coating composition containing a solvent-free base agent and a solvent-free curing agent; the solvent-free base contains a film-forming resin (a) and a pigment; the film-forming resin (a) comprises at least one selected from polyols and polyamines; the solventless curing agent comprises a polyisocyanate; The content of the pigment is 5 parts by mass or more and 55 parts by mass or less relative to 100 parts by mass of the solid content of the first coating composition, The method for producing a coating film, wherein the second coating composition contains silica fine particles and a hydrophilic medium.

2. 2. The method for producing a coating film according to claim 1, wherein in the first coating composition, the molar ratio [NCO / H] of the isocyanate group contained in the solvent-free curing agent to the group having an active hydrogen atom contained in the solvent-free main component is 0.5 or more and 2.0 or less.

3. The method for producing a coating film according to claim 1 , wherein the pigment comprises a heat-shielding pigment.

4. The method for producing a coating film according to claim 1, wherein in the second coating composition, the silica fine particles have an average primary particle diameter of 1 nm or more and 10 μm or less.

5. The method for producing a coating film according to claim 1 , wherein the second coating composition contains a photocatalyst.

6. The method for producing a coating film according to claim 5 , wherein the photocatalyst contains titanium oxide.

7. The method for producing a coating film according to claim 1 , wherein the coating film is formed on a surface of a pavement.

8. The method for producing a coating film according to any one of claims 1 to 7, wherein the coating film is a coating film for road markings and / or road heat insulation.

Images