Thermosetting coating composition, cured coating film, and laminate

Abstract

To provide a thermosetting coating composition capable of forming a cured coating film excellent in extensibility, toughness and shielding properties.SOLUTION: The thermosetting coating composition according to the present invention comprises a polycarbonate polyol (A) and / or a polyether polyol (B), a carbodiimide-modified diphenylmethane diisocyanate (C), at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), and a color pigment (G).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermosetting coating composition. The present invention also relates to a cured coating film formed from the thermosetting coating composition. Furthermore, the present invention also relates to a laminate comprising the cured coating film. [Background technology]

[0002] In recent years, from an environmental perspective, methods of applying films instead of spray coating have been considered for the surface protection of molded bodies such as automobile interior parts and laptop computer housings. Molded bodies come in a variety of shapes, and if the extensibility and toughness of the cured coating film are insufficient, problems such as cracks will occur when the cured coating film is applied to the molded body. Therefore, there is a demand for coating compositions that can form cured coating films with extensibility and toughness.

[0003] For example, Patent Document 1 proposes a two-component thermosetting polyurethane resin that has excellent scratch resistance, heat resistance, light resistance, and the like and can be obtained by reacting a polyol component (A) with an organic polyisocyanate component (B), in which the polyol component (A) uses at least one compound selected from the group consisting of (a-1) a specific polyether polyol, (a-2) a specific polyester diol, and (a-3) a specific polycarbonate diol, and (a-4) a specific non-amine glycol, and the organic polyisocyanate component (B) uses a specific polycyclic aliphatic polyisocyanate compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-270929 Summary of the Invention [Problem to be solved by the invention]

[0005] When a cured coating film made from the thermosetting coating composition of the present invention is applied to a molded body, it is required to have not only extensibility and toughness but also the shielding property of the underlying molded body. However, the two-component thermosetting polyurethane resin described in Patent Document 1 leaves room for improvement in terms of shielding property and coating film properties.

[0006] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a thermosetting coating composition that can form a cured coating film that is excellent in extensibility, toughness, and shielding properties. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have found that the above problems can be solved by using a thermosetting coating composition containing a polycarbonate polyol (A) and / or a polyether polyol (B), a carbodiimide-modified diphenylmethane diisocyanate (C), at least one isocyanate selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), and a color pigment (G). The present invention was completed based on this finding.

[0008] That is, according to the present invention, the following inventions are provided. [1] A thermosetting coating composition comprising a polycarbonate polyol (A) and / or a polyether polyol (B), a carbodiimide-modified diphenylmethane diisocyanate (C), at least one isocyanate selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), and a color pigment (G). [2] The thermosetting coating composition according to [1], wherein the hydroxyl values ​​(mgKOH / g) of the polycarbonate polyol (A) and the polyether polyol (B) are 30 or more and 300 or less. [3] The thermosetting coating composition according to [1] or [2], wherein the weight average molecular weight of the polycarbonate polyol (A) and the polyether polyol (B) is 300 or more and 8,000 or less. [4] The thermosetting coating composition according to any one of [1] to [3], wherein the molar ratio of isocyanate groups to hydroxyl groups in the thermosetting coating composition is 0.9 or more and 1.5 or less. [5] The thermosetting coating composition according to any one of [1] to [4], wherein the blending ratio of the carbodiimide-modified diphenylmethane diisocyanate (C) to at least one selected from the group consisting of the trimethylolpropane adduct isocyanate (D), the biuret isocyanate (E) and the allophanate isocyanate (F) is 5:95 to 80:20. [6] The thermosetting coating composition according to any one of [1] to [5], further comprising a metal catalyst (H). [7] The thermosetting coating composition according to any one of [1] to [6], further comprising a leveling agent (I). [8] A thermosetting coating composition according to any one of [1] to [7], wherein when the thermosetting coating composition is used to form a cured coating film having a thickness of 20 μm, the cured coating film has an elongation of 200% or more and a breaking strength of 2.0 N / 10 mm or more. [9] A first component containing at least the polycarbonate polyol (A) and / or the polyether polyol (B); and a second component containing at least a carbodiimide-modified diphenylmethane diisocyanate (C) and at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), The thermosetting coating composition according to any one of [1] to [8], which is a multi-component thermosetting coating composition in which the first component and / or the second component further contains a color pigment (G).

[10] A cured coating film formed from the thermosetting coating composition according to any one of [1] to [9].

[11] A laminate comprising a substrate and the cured coating film according to

[10] laminated on the substrate.

[12] The laminate according to

[11] , further comprising a hard coat layer on the cured coating film. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a thermosetting coating composition capable of forming a cured coating film that is excellent in extensibility, toughness, and shielding properties. Furthermore, the thermosetting coating composition according to the present invention has excellent workability due to its long pot life. Furthermore, according to the present invention, it is also possible to provide a cured coating film formed from such a thermosetting coating composition. Furthermore, according to the present invention, it is also possible to provide a laminate comprising such a cured coating film. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. [Figure 2] 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in more detail below. In this specification, the term "solid content" refers to the components remaining after excluding volatile components such as organic solvents from the thermosetting coating composition, and which constitute the cured coating film when cured.

[0012] <Thermosetting paint composition> The thermosetting coating composition of the present invention comprises a polycarbonate polyol (A) and / or a polyether polyol (B), a carbodiimide-modified diphenylmethane diisocyanate (C), at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), and a color pigment (G). The thermosetting coating composition may further comprise a metal catalyst (H) and / or a leveling agent (I). By including the above components, the thermosetting coating composition of the present invention can form a cured coating film with excellent extensibility, toughness, and shielding properties. Such a thermosetting coating composition can be used for surface coating of various molded articles such as components, frames, and housings.

[0013] The thermosetting coating composition according to the present invention is preferably a multi-component thermosetting coating composition comprising a first component as a main component and a second component as a curing agent. The first component of the multi-component thermosetting coating composition comprises at least a polycarbonate polyol (A) and / or a polyether polyol (B), and the second component comprises at least a carbodiimide-modified diphenylmethane diisocyanate (C) and at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), and it is preferred that the first component and / or the second component further comprise a color pigment (G).

[0014] The compounding ratio of the first component (main agent) to the second component (curing agent) can be adjusted appropriately depending on the amount of hydroxyl groups in the first component and the amount of isocyanate groups in the second component. For example, from the viewpoint of curability, the amount of the second component is preferably 1.0 to 50 parts by mass, more preferably 2.0 to 45 parts by mass, and even more preferably 3.0 to 40 parts by mass, per 100 parts by mass of the first component.

[0015] The thermosetting coating composition of the present invention may further contain other components in addition to the above components (A) to (I). Each component constituting the thermosetting coating composition will be described in detail below.

[0016] ((A) to (B) Polyols) The thermosetting coating composition according to the present invention contains a polycarbonate polyol (A) and / or a polyether polyol (B) as the main polyol.

[0017] Polycarbonate polyol is a compound having at least two carbonate bonds in the main skeleton of the molecule and two or more hydroxyl groups. As the polycarbonate polyol, a conventionally known polycarbonate polyol can be used. The polycarbonate polyol may be used alone or in combination of two or more.

[0018] The polycarbonate polyol is not particularly limited, and examples thereof include reaction products obtained by polycondensation of the following polyol components and carbonate components: Examples of the polyol component include diols such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 2-methylpropanediol, dipropylene glycol, and diethylene glycol, as well as reaction products of these diols with dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, and hexahydrophthalic acid. Examples of the carbonate component include aromatic carbonates or aliphatic carbonates such as diphenyl carbonate, bis(chlorophenyl) carbonate, dinaphthyl carbonate, phenyltoluyl carbonate, phenylchlorophenyl carbonate, 2-tolyl-4-tolyl carbonate, dimethyl carbonate, diethyl carbonate, diethylene carbonate, and ethylene carbonate.

[0019] The hydroxyl value (mgKOH / g) of the polycarbonate polyol is preferably from 30 to 300, more preferably from 40 to 290, and even more preferably from 50 to 280. When the hydroxyl value of the polycarbonate polyol is within the above range, the extensibility and breaking strength are good.

[0020] The weight-average molecular weight (Mw) of the polycarbonate polyol is preferably 300 or more and 8000 or less, more preferably 500 or more and 7500 or less, and even more preferably 700 or more and 7000 or less. When the weight-average molecular weight (Mw) value of the polycarbonate polyol is within the above numerical range, the extensibility and breaking strength are good. The weight-average molecular weight (Mw) of the polycarbonate polyol is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0021] Polyether polyol is a compound having at least two ether bonds in the main skeleton of the molecule and having two or more hydroxyl groups. As the polyether polyol, a conventionally known polyether polyol can be used. The polyether polyol may be used alone or in combination of two or more.

[0022] The repeating units in the main skeleton of the polyether polyol may be either saturated hydrocarbons or unsaturated hydrocarbons, and examples thereof include 1,4-butanediol units, 2-methyl-1,4-butanediol units, 3-methyl-1,4-butanediol units, 1,3-propanediol units, 1,2-propylene glycol units, 2-methyl-1,3-propanediol units, 2,2-dimethyl-1,3-propanediol units, 3-methyl-1,5-pentanediol units, 1,2-ethylene glycol units, 1,6-hexanediol units, 1,7-heptanediol units, 1,8-octanediol units, 1,9-nonanediol units, 1,10-decanediol units, and 1,4-cyclohexanedimethanol units. Examples of such polyether polyols include reaction products obtained by addition polymerization of alkylene oxides such as propylene oxide and ethylene oxide to compounds having two or more hydroxyl groups in the molecule, such as glycol, glycerin, and sucrose.

[0023] The hydroxyl value (mgKOH / g) of the polyether polyol is preferably from 30 to 300, more preferably from 40 to 290, and even more preferably from 50 to 280. When the hydroxyl value of the polyether polyol is within the above range, the elongation and breaking strength are good.

[0024] The weight-average molecular weight (Mw) of the polyether polyol is preferably 300 to 8000, more preferably 350 to 7000, and even more preferably 400 to 6000. When the weight-average molecular weight (Mw) of the polyether polyol is within the above range, the extensibility and breaking strength are good. The weight-average molecular weight (Mw) of the polyether polyol is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0025] The total content of polycarbonate polyol and polyether polyol is 15% by mass or more and 70% by mass or less, preferably 25% by mass or more and 65% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, relative to 100% by mass of the solid content in the thermosetting coating composition. The content of the polycarbonate polyol and polyether polyol is 30% by mass or more and 90% by mass or less, preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less, based on 100% by mass of the solid content in the first component. If the content of the polycarbonate polyol and polyether polyol is within the above range, the elongation and breaking strength can be improved.

[0026] ((C)~(F) Isocyanates) The thermosetting coating composition of the present invention contains, as the isocyanate curing agent, a carbodiimide-modified diphenylmethane diisocyanate (C) and at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F). The isocyanate groups (NCO groups) of the isocyanates (C) to (F) react with the hydroxyl groups (OH groups) contained in the polycarbonate polyol (A) and the polyether polyol (B) to cure and form a polyurethane. The combination of these specific isocyanates enables the formation of a cured coating film with excellent extensibility and toughness.

[0027] The isocyanate monomers of the trimethylolpropane adduct isocyanate (D), biuret isocyanate (E), and allophanate isocyanate (F) are not particularly limited, and examples thereof include hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), and diphenylmethane diisocyanate (MDI). These trimethylolpropane adduct isocyanates, biuret isocyanates, and allophanate isocyanates may be used alone or in combination of two or more.

[0028] The blending ratio ((C):{(D) + (E) + (F)}) of the carbodiimide-modified diphenylmethane diisocyanate (C) to at least one selected from the group consisting of the trimethylolpropane adduct isocyanate (D), the biuret isocyanate (E), and the allophanate isocyanate (F) is preferably 5:95 to 80:20, more preferably 10:90 to 75:25, even more preferably 20:80 to 70:30, and still more preferably 30:70 to 65:35. When the blending ratio of the carbodiimide-modified diphenylmethane diisocyanate (C) to at least one selected from the group consisting of the trimethylolpropane adduct isocyanate (D), the biuret isocyanate (E), and the allophanate isocyanate (F) is within the above range, a cured coating film having excellent extensibility and toughness can be easily formed.

[0029] The molar ratio of isocyanate groups to hydroxyl groups (NCO groups / OH groups) in the thermosetting coating composition is preferably 0.9 to 1.5, more preferably 0.95 to 1.45, and even more preferably 1.0 to 1.4. If the molar ratio of isocyanate groups to hydroxyl groups in the thermosetting coating composition is within the above numerical range, the reactivity will be good, and it will be easy to form a cured coating film that is excellent in extensibility and toughness.

[0030] ((G) Coloring pigment) As the coloring pigment, conventionally known coloring pigments for coating compositions can be used. Examples of coloring pigments include black pigments such as carbon black, aniline black, and black iron oxide; red pigments such as red iron oxide, red lead oxide, diketopyrrolopyrrole, perinone, anthraquinone, perylene, indigoid, and quinacridone; yellow pigments such as yellow iron oxide, zinc yellow, chrome yellow, isoindolinone, isoindoline, azomethine, anthraquinone, anthrone, xanthene, and disazo pigments; and white pigments such as titanium oxide and zinc white. Among these, black pigments are preferred from the viewpoint of opacity. These coloring pigments may be used alone or in combination of two or more.

[0031] The content of the color pigment is preferably 10% by mass or more and 45% by mass or less, more preferably 15% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 35% by mass or less, based on 100% by mass of the solid content in the thermosetting coating composition. If the content of the color pigment is within the above range, the shielding properties of the cured coating film can be improved. The content of the color pigment is preferably 25% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less, based on 100% by mass of the solid content in the first component. If the content of the color pigment is within the above range, the shielding properties of the cured coating film can be improved.

[0032] ((H) Metal catalyst) The metal catalyst is not particularly limited, and conventionally known metal catalysts for thermosetting coating compositions can be used. Examples of metal catalysts include tin-based catalysts (butyltin carboxylate, trimethyltin laurate, dibutyltin dilaurate, etc.), lead-based catalysts (lead octoate, etc.), bismuth-based catalysts, zinc-based catalysts, and aluminum-based catalysts. Among these, tin-based catalysts are preferred from the viewpoint of reactivity. These catalysts may be used alone or in combination of two or more.

[0033] The content of the metal catalyst is preferably 0.008% by mass or more and 0.1% by mass or less, more preferably 0.01% by mass or more and 0.08% by mass or less, and even more preferably 0.02% by mass or more and 0.06% by mass or less, based on 100% by mass of the solid content in the thermosetting coating composition. If the content of the catalyst is within the above numerical range, the reaction promotion effect and the pot life are well balanced, and workability is improved. The content of the metal catalyst is preferably 0.01% by mass or more and 0.1% by mass or less, more preferably 0.02% by mass or more and 0.09% by mass or less, and even more preferably 0.03% by mass or more and 0.07% by mass or less, based on 100% by mass of the solid content in the first component. If the content of the catalyst is within the above range, the reaction-accelerating effect and the pot life are well balanced, and workability is improved.

[0034] ((I) Leveling Agent) The leveling agent is not particularly limited, and any conventionally known leveling agent can be used, including fluorine-based leveling agents, silicone-based leveling agents, and acrylic polymer-based leveling agents.

[0035] Commercially available UV-reactive fluorine-based leveling agents include Ftergent 601AD, Ftergent 601ADH2, Ftergent 602A, Ftergent 650AC, and Ftergent 681, all manufactured by Neos Corporation. Examples of UV non-reactive fluorine-based leveling agents include FTX-218, Ftergent 215M, Ftergent 710FL, Ftergent 220P, Ftergent 228P, Ftergent 208G, Ftergent 240G, Ftergent 710FM, Ftergent 710FS, Ftergent 710FL, Ftergent 730LM, Ftergent 710FM, and Ftergent 683. Examples of UV-reactive silicone leveling agents include those manufactured by Big Chemie Japan Co., Ltd. under the trade names BYK-UV3500, BYK-UV3505, BYK-UV3510, BYK-UV3530, BYK-UV3570, BYK-UV3575, and BYK-UV3576. Examples of UV non-reactive silicone leveling agents include BYK-3550, BYK-SILCLEAN 3700, and BYK-SILCLEAN 3720. Examples of other leveling agents such as acrylics include BYK-UV3535, which is a UV reactive type, and BYK-399 and BYK-3440, which are UV non-reactive types. These may be used alone or in combination of two or more. Among these, silicone-free BYK-399 is preferred.

[0036] The content of the leveling agent is preferably 0.04% by mass or more and 0.6% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and even more preferably 0.1% by mass or more and 0.4% by mass or less, based on 100% by mass of the solid content in the thermosetting coating composition. If the content of the leveling agent is within the above numerical range, the smoothness of the coating film is easily improved. The content of the leveling agent is preferably 0.05% by mass or more and 0.6% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.2% by mass or more and 0.4% by mass or less, relative to 100% by mass of the solid content in the first component. If the content of the leveling agent is within the above range, the smoothness of the coating film is likely to be improved.

[0037] (Other ingredients) The thermosetting coating composition of the present invention may contain other components in addition to the above components (A) to (I) as long as the object of the present invention is not impaired. Such other components may include, as needed, light stabilizers, ultraviolet absorbers, antistatic agents, polymerization inhibitors, non-reactive diluents, matting agents, dispersants, anti-settling agents, adhesion improvers, photosensitizers, antibacterial agents, antifungal agents, antiviral agents, plasticizers, luminescent materials, solvents, etc.

[0038] When a cured coating film having a thickness of 20 μm is formed using the thermosetting coating composition of the present invention, the elongation of the cured coating film is preferably 200% or more, more preferably 250% or more, and even more preferably 300% or more, and the breaking strength of the cured coating film is preferably 2.0 N / 10 mm or more, more preferably 3.0 N / 10 mm or more, and even more preferably 4.0 N / 10 mm or more. If the elongation and breaking strength values ​​of the cured coating film satisfy the above values, it can be said that the cured coating film has excellent extensibility and toughness. The elongation and breaking strength values ​​of the cured coating film are values ​​measured by the measurement methods described in the examples below.

[0039] <Method for preparing thermosetting coating composition> The thermosetting coating composition of the present invention can be obtained by mixing and stirring the first and second components using a conventionally known device such as a mixer, disperser, stirrer, etc. Examples of such devices include a mixing and dispersion mill, a homodisper, a mortar mixer, a roll, a paint shaker, a homogenizer, etc.

[0040] In the present invention, the thermosetting coating composition can be diluted with a solvent as needed, for example, to adjust the viscosity to a level suitable for application. The solvent is not particularly limited as long as it dissolves the resin component of the thermosetting coating composition. Specific examples include 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 ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and diethylene glycol monoethyl ether), 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.

[0041] <Laminate> The laminate according to the present invention comprises a substrate and the cured coating film laminated on the substrate. The laminate may further comprise a hard coat layer on the cured coating film. The laminate may further comprise another layer, such as an adhesive layer, between the substrate and the cured coating film.

[0042] Schematic cross-sectional views of embodiments of laminates according to the present invention are shown in Figures 1 and 2. Laminate 11 shown in Figure 1 has a substrate 12 and a cured coating film 13 laminated on substrate 12. Laminate 21 shown in Figure 2 has a substrate 22, a cured coating film 23 laminated on substrate 22, and a hard coat layer 24 laminated on cured coating film 23. In addition, when the laminate is used after peeling off the substrate (such as a release film), the laminate may have a substrate, a hard coat layer laminated on the substrate, and a cured coating film laminated on the hard coat layer.

[0043] The substrate is not particularly limited, and various resin films can be used, such as polyurethane resin, polyester resin, polycarbonate resin, polystyrene resin, polyolefin resin, polyethersulfone resin, acrylonitrile-styrene copolymer resin, polyamide resin, cellulose resin, polyarylate resin, polymethyl methacrylate resin, and polymethacrylimide resin.

[0044] The thickness of the substrate is not particularly limited, but is preferably 10 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0045] The thickness of the cured coating film is not particularly limited, but is preferably from 1 μm to 50 μm, and more preferably from 10 μm to 30 μm.

[0046] The composition of the hard coat layer is not particularly limited, and may be a conventionally known hard coat layer used for protecting the surface of molded articles such as automobile interior parts, laptop computer housings, etc. Examples of compositions used for the hard coat layer include conventionally known thermosetting paints, ultraviolet-curing paints, etc.

[0047] The thickness of the hard coat layer is not particularly limited, but is preferably from 1 μm to 30 μm, and more preferably from 3 μm to 15 μm.

[0048] <Method of manufacturing laminate> The laminate of the present invention comprises a coating step of coating the above-mentioned thermosetting coating composition on at least one surface of a substrate; a curing step of heating and curing the thermosetting coating composition to form a cured coating film after the coating step; Each step will be described in detail below.

[0049] (Coating process) The coating step is a step of applying the multi-component thermosetting coating composition to at least one surface of a substrate by a conventionally known method. For example, a coating machine such as a bar coater, a gravure coater, a roll coater (such as a natural roll coater or a reverse roll coater), an air knife coater, a spin coater, or a blade coater can be used for coating. Among these, a coating method using a gravure coater is preferred from the viewpoint of workability and productivity.

[0050] (hardening process) The curing step is a step in which the thermosetting coating composition applied to the substrate is heated and cured. Examples of heating methods include hot air drying (jet dryer, etc.). The heating temperature is not particularly limited as long as it is a temperature sufficient to cure the thermosetting coating composition, but is preferably 60 to 170°C, and more preferably 100 to 160°C. The heating time is also not particularly limited as long as it is a time sufficient to cure the thermosetting coating composition, but is preferably 1 minute or longer. [Example]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0052] To prepare the thermosetting coating composition, the following materials were prepared: (1st component) (A) Polycarbonate polyol 1: hydroxyl value 228.0 mgKOH / g, weight average molecular weight (Mw) 1000, manufactured by Kuraray Co., Ltd., trade name Kuraray Polyol C-590 (A) Polycarbonate polyol 2: hydroxyl value 112.0 mgKOH / g, weight average molecular weight (Mw) 2700, manufactured by Kuraray Co., Ltd., trade name Kuraray Polyol C-1090 (A) Polycarbonate polyol 3: hydroxyl value 110.0 mgKOH / g, weight average molecular weight (Mw) 3300, manufactured by Asahi Kasei Corporation, trade name Duranol T5651 (A) Polycarbonate polyol 4: hydroxyl value 54.8 mg KOH / g, weight average molecular weight (Mw) 6300, manufactured by Kuraray Co., Ltd., trade name Kuraray Polyol C-2090 (B) Polyether polyol 1: hydroxyl value 263.0 mgKOH / g, weight average molecular weight (Mw) 400, manufactured by ADEKA Corporation, trade name ADEKA Polyether P-400 (B) Polyether polyol 2: hydroxyl value 110.0 mgKOH / g, weight average molecular weight (Mw) 1000, manufactured by ADEKA Corporation, trade name ADEKA Polyether P-1000 Other polyol 1 (polycaprolactone triol): hydroxyl value 83.4 mg KOH / g, weight average molecular weight (Mw) 2000, manufactured by Daicel Corporation, trade name Plaxel L320AL Other polyol 2 (polyester polyol): hydroxyl value 130.0 mgKOH / g, weight average molecular weight (Mw) 3000, manufactured by DIC Corporation, product name Burnock D6-439 (G) Pigment: Black pigment, Mikuni Color Co., Ltd., product name MHI Black #A119 (H) Metal catalyst: tin-based catalyst, manufactured by DIC Corporation, trade name Grec TL (I) Leveling agent: BYK-399, manufactured by BYK-Chemie Japan Co., Ltd. Light stabilizer: Riasorb UV-123, manufactured by Rianlon Corporation UV absorber: BASF Ltd., product name: Tinuvin 479 Solvent: Butyl acetate (Second component) (C) Carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI): isocyanate group ratio 29.0%, manufactured by Tosoh Corporation, trade name Millionate MTL (D) Trimethylolpropane adduct type xylylene diisocyanate (TMP adduct type XDI): isocyanate group ratio 11.6%, manufactured by Mitsui Chemicals, Inc., product name Takenate D-110N (D) Trimethylolpropane adduct type bis(isocyanatomethyl)cyclohexane (TMP adduct type H6XDI): isocyanate group ratio 11.0%, manufactured by Mitsui Chemicals, Inc., trade name Takenate D-120N (D) Trimethylolpropane adduct type tolylene diisocyanate (TMP adduct type TDI): isocyanate group ratio 13.0%, manufactured by Mitsui Chemicals, Inc., product name Takenate D-103H (D) Trimethylolpropane adduct type isophorone diisocyanate (TMP adduct type IPDI): isocyanate group ratio 10.5%, manufactured by Mitsui Chemicals, Inc., trade name Takenate D-140N (D) Trimethylolpropane adduct type hexamethylene diisocyanate 1 (TMP adduct type HDI1): isocyanate group ratio 6.0%, weight average molecular weight (Mw) 3700, manufactured by Asahi Kasei Corporation, product name Duranate E405-70B (D) Trimethylolpropane adduct type hexamethylene diisocyanate 2 (TMP adduct type HDI2): isocyanate group ratio 7.3%, weight average molecular weight (Mw) 3700, manufactured by Asahi Kasei Corporation, product name Duranate E402-80B (E) Biuret-type hexamethylene diisocyanate 1 (Biuret-type HDI1): Isocyanate group ratio 23.3%, manufactured by Mitsui Chemicals, Inc., product name Takenate D-165N (E) Biuret-type hexamethylene diisocyanate 2 (biuret-type HDI2): isocyanate group ratio 23.5%, weight average molecular weight (Mw) 350, manufactured by Asahi Kasei Corporation, product name Duranate 24A-100 (F) Allophanate-type hexamethylene diisocyanate (allophanate-type HDI): isocyanate group ratio 19.0%, manufactured by Mitsui Chemicals, Inc., product name Takenate D-178NL

[0053] <Preparation of Thermosetting Coating Composition> [Example 1] Thermosetting coating compositions were prepared according to the formulations shown in Tables 1 and 2. Specifically, a first component containing 22.9 parts by mass of solvent, 24.6 parts by mass of polycarbonate polyol 1 (A), 0.02 parts by mass of metal catalyst, 0.06 parts by mass of light stabilizer, 0.12 parts by mass of UV absorber, 0.1 parts by mass of leveling agent, and 52.2 parts by mass of pigment organic solvent dispersion (F) was mixed with a second component containing 11.15 parts by mass of carbodiimide-modified MDI (C) and 16.05 parts by mass of TMP adduct type HDI1 (D) and stirred to obtain a thermosetting coating composition.

[0054] [Examples 2 to 19, Comparative Examples 1 to 6] Thermosetting coating compositions were obtained in the same manner as in Example 1, except that the amounts of each component were changed according to the formulations shown in Tables 1 to 6.

[0055] <Production of test specimens of cured coating films> Each of the thermosetting coating compositions prepared above was applied to a release film using a bar coater to a dry film thickness of approximately 20 μm, and then placed in an oven at 150° C. for 1 hour to form a cured coating film, yielding a substrate with a cured coating film. Next, a piece measuring 15 cm long and 1 cm wide was cut out from the resulting substrate with the cured coating film alone to obtain each test specimen with the cured coating film.

[0056] <Evaluation of cured coating film> (Appearance evaluation) Each test specimen of the cured coating film produced above was visually evaluated according to the following criteria. The evaluation results are shown in Tables 7 to 9. Evaluation results of "good" or "fair" indicate passing. [Evaluation criteria] ○: No aggregation occurred. △: Slight aggregation etc. occurred. ×: Coagulation etc. occurred over the entire coating film.

[0057] (stretchability and toughness) Each of the cured coating film specimens prepared above was clamped between jigs at the top and bottom, 2.5 cm apart, and pulled at a rate of 50 mm / min using a small tabletop testing machine (EZ-L, manufactured by Shimadzu Corporation). The elongation (%) of each cured coating film specimen until it broke was measured. The breaking strength (N) of each cured coating film specimen at the time of breaking was also measured at the same time. The measurement results are shown in Tables 7 to 9. A specimen with an elongation of 200% and a breaking strength of more than 2.0 N was judged to pass. In Comparative Example 6, the cured coating film specimen shrunk when peeled from the substrate (release film), making it impossible to measure the elongation and breaking strength of the cured coating film. The result of Comparative Example 6 in Table 9 ("-") indicates that measurement was not possible.

[0058] (pot life) To each of the thermosetting coating compositions prepared above, 5 parts by mass of a cure adjuster (acetylacetone) was added per 100 parts by mass of the first component, and the change in viscosity at 23°C (initial viscosity: approximately 10 mPa s) was measured using a B-type viscometer (BLII type viscometer, manufactured by Toki Sangyo Co., Ltd.) and evaluated according to the following criteria. The evaluation results are shown in Tables 7 to 9. [Evaluation criteria] ○: Viscosity was 500 mPa·s or less 6 hours after preparation. ×: Viscosity was greater than 500 mPa·s 6 hours after preparation.

[0059] (shielding property) Each test specimen of the cured coating film produced above was placed on a sheet with letters printed on it, and a judgment was made as to whether the letters were visible or not, and the evaluation was performed according to the following criteria. The evaluation results are shown in Tables 7 to 9. [Evaluation criteria] ○: The characters were not visible. ×: The characters were visible.

[0060] <Production of laminate> First, a thermosetting coating composition for the hard coat layer was prepared. Specifically, the first component containing 3.82 parts by weight of solvent, 57.1 parts by weight of acrylic polyol, 38.5 parts by weight of polyester polyol, 0.03 parts by weight of metal catalyst, 0.15 parts by weight of light stabilizer, 0.30 parts by weight of ultraviolet absorber, and 0.1 parts by weight of leveling agent was mixed with the second component containing 63.2 parts by weight of XDI, and stirred to obtain a thermosetting coating composition for the hard coat layer. Next, the thermosetting coating composition for the hard coat layer prepared above was applied to a release film using a bar coater to a dry film thickness of approximately 3 μm, and then the film was placed in an oven at 150°C for 1 hour to form a hard coat layer. Next, the thermosetting coating composition obtained in Example 2 was applied onto the hard coat layer of the release film using a bar coater to a dry film thickness of approximately 20 μm, and then placed in an oven at 150°C for 1 hour to form a cured coating film, thereby obtaining a laminate (layer structure: release film / hard coat layer / cured coating film).

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] [Table 5]

[0066] [Table 6]

[0067] [Table 7]

[0068] [Table 8]

[0069] [Table 9] [Explanation of symbols]

[0070] 11, 21: Laminate 12, 22: Base material 13, 23: Cured coating film 24: Hard coat layer

Claims

1. A thermosetting coating composition comprising: a polycarbonate polyol (A) and / or a polyether polyol (B); a carbodiimide-modified diphenylmethane diisocyanate (C); at least one isocyanate selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F); and a color pigment (G).

2. 2. The thermosetting coating composition according to claim 1, wherein the polycarbonate polyol (A) and the polyether polyol (B) have a hydroxyl value (mgKOH / g) of 30 or more and 300 or less.

3. 2. The thermosetting coating composition according to claim 1, wherein the weight average molecular weight of the polycarbonate polyol (A) and the polyether polyol (B) is 300 or more and 8,000 or less.

4. 2. The thermosetting coating composition according to claim 1, wherein the molar ratio of isocyanate groups to hydroxyl groups in the thermosetting coating composition is 0.9 or more and 1.5 or less.

5. The thermosetting coating composition according to claim 1, wherein the blending ratio of the carbodiimide-modified diphenylmethane diisocyanate (C) to at least one selected from the group consisting of the trimethylolpropane adduct isocyanate (D), the biuret isocyanate (E), and the allophanate isocyanate (F) is 5:95 to 80:

20.

6. The thermosetting coating composition of claim 1 further comprising a metal catalyst (H).

7. 2. The thermosetting coating composition of claim 1, further comprising a leveling agent (I).

8. 2. The thermosetting coating composition according to claim 1, wherein, when the thermosetting coating composition is used to form a cured coating film having a thickness of 20 μm, the cured coating film has an elongation of 200% or more and a breaking strength of 2.0 N / 10 mm or more.

9. a first component containing at least the polycarbonate polyol (A) and / or the polyether polyol (B); and a second component containing at least a carbodiimide-modified diphenylmethane diisocyanate (C) and at least one selected from the group consisting of a trimethylolpropane adduct isocyanate (D), a biuret isocyanate (E), and an allophanate isocyanate (F), 2. The thermosetting coating composition according to claim 1, wherein the first component and / or the second component is a multi-component thermosetting coating composition further comprising a coloring pigment (G).

10. A cured coating film formed from the thermosetting coating composition according to any one of claims 1 to 9.

11. A laminate comprising a substrate and the cured coating film according to claim 10 laminated on the substrate.

12. The laminate according to claim 11 , further comprising a hard coat layer on the cured coating film.

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