Two-pack type coating composition for in-mold coating

Abstract

Provided is a two-pack type coating composition for in-mold coating which comprises a main preparation and a curing agent, wherein the main preparation comprises a polyol (A), a curing catalyst (B), an electroconductive pigment (C), and a pigment dispersant (D) and the curing agent includes an isocyanurate compound (E). The polyol (A) has a hydroxyl value of 300-1,000 mgKOH / g, the content of the curing catalyst (B) is 0.05-3 parts by mass per 100 parts by mass of the polyol (A), the electroconductive pigment (C) has a DBP oil absorption of 490 cm3 / 100 g or less, and the two-pack type coating composition has a solvent content of 30 mass% or less.

Description

Two-component coating composition for in-mold coating

[0001] The present invention relates to a two-component coating composition for in-mold coating.

[0002] Coating films with various functions are formed on the surfaces of industrial products and the like. The coating film not only protects the coated object but also gives it a beautiful appearance and excellent design. Coating films are generally formed by spraying a coating composition containing a solvent such as an organic solvent and / or an aqueous solvent, followed by drying. However, in recent years, there have been problems such as the scattering of solvent during spray coating, the release of solvent into the atmosphere during the drying process, and CO ２ Furthermore, spray painting requires a drying process, which can lead to reduced productivity.

[0003] Therefore, in-mold coating, in which coating is performed inside a mold, has been proposed as an alternative coating method to spray coating. Patent Document 1 discloses a coating composition for use in in-mold coating.

[0004] International Publication No. 2022 / 092163

[0005] An object of the present invention is to provide a two-component coating composition for in-mold coating that contains a conductive pigment.

[0006] In order to solve the above problems, the present invention provides the following aspects. [1] A two-component coating composition comprising a base agent and a curing agent, wherein the base agent comprises a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D), the curing agent comprises an isocyanurate compound (E), the hydroxyl value of the polyol (A) is 300 mg KOH / g or more and 1000 mg KOH / g or less, the content of the curing catalyst (B) is 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the solid content of the polyol (A), and the conductive pigment (C) has a DBP oil absorption of 490 cm ３[2] The two-component coating composition for in-mold coating, wherein the polyol (A) contains a first polyester polyol having three or more hydroxyl groups and a branched structure. [3] The two-component coating composition according to [2], wherein the proportion of the first polyester polyol in the total content of the polyol (A) is 35% by mass or more. [4] The main agent is a polymerizable compound having a viscosity of 1000 ps / 100 g or less, and a shear rate of 1.0 sec or less. －１ The low shear viscosity (LSV) measured under the conditions of 60°C, shear rate 100 sec －１ The two-component coating composition according to any one of [1] to [3] above, wherein the TI value (LSV / HSV), obtained by dividing the TI value by the high shear viscosity HSV (mPa s) measured under the conditions of [1] to [3], is 2.0 or more and 200 or less. [5] The two-component coating composition according to any one of [1] to [4] above, wherein the content of the conductive pigment (C) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the solid content of the polyol (A). [6] The two-component coating composition according to any one of [1] to [5] above, wherein the polyol (A) comprises at least one selected from the group consisting of polyester polyols, polyether polyols, and polycarbonate polyols. [7] The two-component coating composition according to any one of [1] to [6] above, which is used to form a primer coating film. [8] A method for forming a multilayer coating film, comprising: applying the two-component coating composition according to any one of [1] to [7] above to a substrate placed on one of the molds using a molding machine equipped with a pair of molds, and then curing the two-component coating composition inside the pair of closed molds to form a primer coating film; removing the substrate from the molding machine, and then applying a base coating composition onto the primer coating to form an uncured base coating film; applying a clear coating composition onto the uncured base coating film to form an uncured clear coating film; and curing the uncured base coating film and the uncured clear coating film.

[0007] According to the present invention, it is possible to provide a two-component coating composition for in-mold coating containing a conductive pigment.

[0008] In-mold coating uses a molding machine with a pair of molds (e.g., a cavity and a core). An article to be coated is placed on one of the molds, and a coating composition is applied to the article. The molds are then closed (i.e., pressure is applied to the coating composition), and the coating composition is cured to form a coating film on the article.

[0009] In-mold coating forms a coating film inside a mold, preventing the adhesion of dust between the substrate and the coating film and the incorporation of dust into the coating film. Furthermore, since the coating is less affected by the surface condition of the substrate, the mold pattern can be transferred to the coating film with high precision. Additionally, since the coating composition contains a small amount of solvent, a drying process to remove the solvent is not required, improving productivity. Furthermore, a thick coating film can be formed with reduced sagging and popping.

[0010] Generally, multiple coating films with various functions are formed on the surface of a substrate, such as an automobile body. One of these coating films is a primer coating. A conductive primer coating is formed on a resin substrate. The conductive primer coating allows other coating films to be formed by electrostatic coating.

[0011] Conductivity is imparted by the use of conductive pigments. Conductive pigments form electrical paths, thereby imparting conductivity in the thickness direction of the coating film. Small particle size conductive pigments generally form electrical paths more easily. On the other hand, small particle size conductive pigments increase the viscosity of the coating composition. In particular, coating compositions for in-mold coating tend to have higher viscosities due to the small amount of solvent. High viscosity coating compositions make it difficult to apply uniformly to the substrate. In addition, when the coating composition is applied, the substrate may be heated by the mold, which may cause the curing reaction of the coating composition to proceed simultaneously. In this case, it is even more important that the coating composition has a low viscosity. It can be said that it is generally difficult to achieve both high conductivity and low viscosity.

[0012] In the present disclosure, a two-component coating composition for in-mold coating with a small amount of solvent has a DBP oil absorption of 490 cm ３ A conductive pigment (C) having a specific surface area of ​​100g or less is used. A low DBP oil absorption means that the pigment has a small specific surface area, which can also be said to have a relatively large particle size. In other words, by using a pigment with a low DBP oil absorption, the viscosity increase of the two-component coating composition is suppressed, improving the dispersibility of the conductive pigment (C). This makes it easier to form an electrical path, and the coating film exhibits high conductivity.

[0013] Hereinafter, the weight average molecular weight and number average molecular weight are measured using a polystyrene standard by GPC (gel permeation chromatography) method.

[0014] The hydroxyl value (OHV) and acid value (AV) are determined based on the mass of the solid content. The hydroxyl value and acid value can be measured by a known method described in JIS K 0070:1992. The hydroxyl value and acid value may be calculated from the amount of unsaturated monomer in the raw material monomer of the resin (e.g., polyol (A)).

[0015] The amine value can be determined in accordance with ASTM D2073 by the following method: (1) Accurately weigh out 500 mg of the object to be tested into a 200 ml Erlenmeyer flask. (2) Add approximately 50 ml of glacial acetic acid and dissolve uniformly. (3) Add 5 to 6 drops of indicator (methyl violet solution) and stir until uniform. (4) Titrate with 0.1 N perchloric acid acetic acid solution, and the endpoint is the point at which the color turns bright green. (The above steps (3) and (4) can also be replaced with potentiometric titration.)

[0016] The average particle size is the 50% average particle size (D50) in the volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution measuring device.

[0017] [Two-component coating composition] The two-component coating composition according to the present disclosure comprises a base agent and a curing agent. The base agent comprises a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D). The curing agent comprises an isocyanurate compound (E). By mixing the base agent and the curing agent, the polyol (A) and the isocyanurate compound (E) react to obtain a cured coating film. The base agent and / or the curing agent may each be heated and / or vacuum degassed before mixing. This reduces the amount of water contained in the two-component coating composition obtained by mixing the two, which facilitates improving the appearance of the resulting coating film.

[0018] The two-component coating composition according to the present disclosure is for in-mold coating. The two-component coating composition according to the present disclosure has electrical conductivity and excellent adhesion to the substrate, and is therefore particularly suitable for forming a primer coating film.

[0019] The two-component coating composition may have a coating work time of 30 seconds or more and less than 900 seconds, as measured by the following test. When the coating work time is 30 seconds or more and less than 900 seconds, the two-component coating composition is deemed to be able to maintain suitable fluidity from the start of application of the two-component coating composition to the substrate to completion in in-mold coating. Due to the appropriate fluidity, the two-component coating composition can easily spread inside the mold. Thereafter, the flow of the two-component coating composition stops, allowing the formation of a uniform primer coating film. Whether a two-component coating composition is suitable for in-mold coating can be evaluated based on the coating work time.

[0020] In in-mold coating, the period from the start to the completion of application of a two-component coating composition to a substrate (application period) corresponds to the following period: When a two-component coating composition is injected between a pair of closed molds (i.e., between a substrate placed on one mold and the other mold), the application time is the time from the start of injection of the two-component coating composition to the completion of injection of a predetermined amount. In this case, a two-component coating composition with a coating work time of 30 seconds or more and less than 600 seconds is suitable. Furthermore, when a two-component coating composition is applied to a substrate placed on one mold with the mold open, the application time is the time from the start of application of the two-component coating composition through the operation of closing the mold and spreading the two-component coating composition over the substrate until the mold movement stops. In this case, a two-component coating composition with a coating work time of 60 seconds or more and less than 900 seconds is suitable. When the coating work time is 60 seconds or more and less than 600 seconds, a two-component coating composition can be used in either case.

[0021] - Coating work time measurement test After adding the curing agent to the base agent in a disposable container, mix with a spatula for 15 seconds. The coating work begins when mixing is complete. The sample is stirred in the container with a spatula, and the coating work ends when the sample does not fall out of the container even when the container is turned upside down. The time required from the start to the end of the coating work is the coating work time.

[0022] (Base Component) The base component contains a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D). The polyol (A) is a film-forming resin. The polyol (A) reacts with a curing agent, for example, by heating, to form a three-dimensional cured coating film. Hereinafter, the curable resins containing the polyol (A) contained in the two-component coating composition may be collectively referred to as a film-forming resin.

[0023] The base agent may have a TI value (LSV / HSV) of 2.0 or more and 200 or less, obtained by dividing the low shear viscosity LSV (mPa·s) measured at 60°C and a shear rate of 1.0 sec-1 by the high shear viscosity HSV (mPa·s) measured at 60°C and a shear rate of 100 sec-1. When the TI value (LSV / HSV) of the base agent is 2.0 or more and 200 or less, the coating composition can be said to have high thixotropy. In other words, when applied to a substrate, the viscosity of the coating composition is sufficiently low. Therefore, the conductive pigment (C) can be said to be well dispersed. On the other hand, the viscosity of the coating composition after application is sufficiently high, allowing the conductive pigment (C) to remain highly dispersed in the coating film. Therefore, many conductive paths are formed, further improving the conductivity of the coating film.

[0024] The LSV of the base material is not particularly limited. To enable higher conductivity, the LSV of the base material is, for example, 1,000 mPa·s or more and 150,000 mPa·s or less. The LSV of the base material may be 5,000 mPa·s or more, 7,000 mPa·s or more, or 10,000 mPa·s or more. The LSV of the base material may be 100,000 mPa·s or less, 80,000 mPa·s or less, or 70,000 mPa·s or less.

[0025] The HSV of the base agent is not particularly limited. From the viewpoint of coating workability, the HSV of the base agent is, for example, 100 mPa·s or more and 5,000 mPa·s or less. The HSV of the base agent may be 200 mPa·s or more, or 300 mPa·s or more. The HSV of the base agent may be 2,000 mPa·s or less, or 1,500 mPa·s or less.

[0026] Each component is described in detail below. Polyol (A) Polyol (A) is a film-forming resin. Polyol (A) has two or more hydroxyl groups per molecule. Polyol (A) reacts with a curing agent, for example, by heating, to form a three-dimensional cured coating film.

[0027] The hydroxyl value (including apparent hydroxyl value; the same applies hereinafter) of the polyol (A) is 300 mgKOH / g or more and 1000 mgKOH / g or less. When the hydroxyl value of the polyol (A) is 300 mgKOH / g or more, the adhesion of the coating film to the substrate (especially a resin substrate) is improved. Furthermore, when the base resin and curing agent are mixed, the reaction rate between the polyol (A) and the isocyanurate compound (E) increases, allowing the coated article to be quickly released from the mold, improving productivity. When the hydroxyl value of the polyol (A) is 1000 mgKOH / g or less, the two-component coating composition can maintain fluidity suitable for in-mold coating for a certain period of time.

[0028] The hydroxyl value of the polyol (A) may be 350 mgKOH / g or more, or 500 mgKOH / g or more, and 800 mgKOH / g or less, or 700 mgKOH / g or less.

[0029] When two or more polyols are contained, the apparent hydroxyl value is calculated based on the hydroxyl value and mass proportion of each polyol. Specifically, when polyols A and B are contained, the apparent hydroxyl value is calculated by (hydroxyl value of polyol A × mass proportion of polyol A) + (hydroxyl value of polyol B × mass proportion of polyol B).

[0030] The base agent may contain multiple polyols with different hydroxyl values, as long as the apparent hydroxyl value is 300 mgKOH / g or more and 1000 mgKOH / g or less. For example, the base agent may contain a polyol with a hydroxyl value of less than 300 mgKOH / g and / or a polyol with a hydroxyl value of more than 1000 mgKOH / g.

[0031] The type of polyol (A) is not particularly limited. Examples of polyol (A) include polyester polyols, polyether polyols, polycarbonate polyols, polyacrylate polyols, and polyhydric alcohols. These may be used alone or in combination of two or more. In particular, polyol (A) may include at least one selected from the group consisting of polyester polyols, polyether polyols, and polycarbonate polyols.

[0032] The polyol (A) may have an average of three or more hydroxyl groups per molecule, which tends to increase the hardness of the resulting coating film.

[0033] The polyol (A) may contain a first polyester polyol having three or more hydroxyl groups and a branched structure. This further improves the conductivity. The reason for this is not clear, but it is thought to be as follows: The first polyester polyol facilitates the formation of a crosslinked resin network. Since the conductive particles are fixed in this resin network, it is thought that an electrical path is also easily formed.

[0034] The first polyester polyol can be obtained, for example, by reacting a trihydric or higher polyhydric alcohol compound with two or more polycarboxylic acids, and repeating the reaction as necessary.

[0035] From the viewpoint of electrical conductivity, the proportion of the first polyester polyol in the total content of polyol (A) is, for example, 35% by mass or more. The proportion of the first polyester polyol may be 40% by mass or more, 45% by mass or more, or 50% by mass or more. The proportion of the first polyester polyol may be 100% by mass, 90% by mass or less, or 80% by mass or less.

[0036] Commercially available polyester polyols include, for example, Desmophen VPLS2249 / 1 (manufactured by Sumika Covestro Urethane Co., Ltd.), Desmophen 800 (manufactured by Sumika Covestro Urethane Co., Ltd.), Desmophen XP2488 (manufactured by Sumika Covestro Urethane Co., Ltd.), and Kuraray Polyol P-510 and F-510 (both manufactured by Kuraray Co., Ltd.).

[0037] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and block products thereof. Polyether polyols can be obtained, for example, by adding ethylene oxide and / or propylene oxide to a polyhydric alcohol compound.

[0038] Commercially available polyether polyols include, for example, the Sannix series manufactured by Sanyo Chemical Industries, Ltd. Specific examples include Sannix GP-250, Sannix GP-400, Sannix PP-200, and Sannix GP-600.

[0039] Polycarbonate polyols can be prepared, for example, by reacting a polyhydric polyol with dimethyl carbonate.

[0040] Commercially available polycarbonate polyols include, for example, Duranol T5650E (manufactured by Asahi Kasei Corporation), C-590 (manufactured by Kuraray Co., Ltd.), and ETERNACOLL PH-50 (manufactured by Ube Industries, Ltd.).

[0041] Examples of polyhydric alcohols include ethylene glycol, glycerin, trimethylolpropane, propylene glycol, tetramethylene glycol, and pentaerythritol.

[0042] The weight average molecular weight (Mw) of the polyol (A) is not particularly limited and may be appropriately set depending on the hydroxyl value and the like.

[0043] Other Film-Forming Resins The base resin may contain other film-forming resins in addition to the polyol (A). Examples of film-forming resins include acrylic resins, polyester resins, alkyd resins, polyether resins, polyolefin resins, polyurethane resins, polycarbonate resins, melamine resins, epoxy resins, and carbodiimide resins. These may be used alone or in combination of two or more.

[0044] Curing catalyst (B) The curing catalyst (B) accelerates the curing reaction. The content of the curing catalyst (B) is 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the solid content of the polyol (A). This allows the curing reaction to proceed relatively slowly, and the two-component coating composition can maintain fluidity suitable for in-mold coating for a certain period of time.

[0045] The content of the curing catalyst (B) may be 0.07 parts by mass or more, or 0.08 parts by mass or more, and may be 2.0 parts by mass or less, 1.0 parts by mass or less, 0.5 parts by mass or less, or 0.3 parts by mass or less.

[0046] The curing catalyst (B) is not particularly limited. From the viewpoint of the acceleration effect, the curing catalyst (B) may be, for example, at least one organometallic catalyst containing a metal element selected from the group consisting of Bi, Zn, Al, Zr, and Sn. Among them, at least one organometallic catalyst containing a metal element selected from the group consisting of Bi, Zn, Al, and Zr may be used.

[0047] Examples of organometallic catalysts containing Bi include bismuth carboxylic acid and its salts. Examples of organometallic catalysts containing Zn include zinc complex catalysts. Examples of organometallic catalysts containing Al include aluminum complex catalysts. Examples of organometallic catalysts containing Zr include zirconium chelate catalysts. Examples of organometallic catalysts containing Sn include dialkyltin dicarboxylates such as dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin diacetate; tin oxide compounds such as dibutyltin oxide; and tin carboxylates such as tin 2-ethylhexanoate. These may be used alone or in combination of two or more.

[0048] Commercially available organometallic catalysts containing Bi include, for example, K-KAT 348 (manufactured by Kusumoto Chemicals Co., Ltd.) and K-KAT XK-640 (manufactured by Kusumoto Chemicals Co., Ltd.). Commercially available organometallic catalysts containing Zr include, for example, K-KAT 4205, K-KAT XC-9213, K-KAT XC-A209, and K-KAT 6212 (all manufactured by Kusumoto Chemicals Co., Ltd.). Commercially available organometallic catalysts containing Al include, for example, K-KAT 5218 (manufactured by Kusumoto Chemicals Co., Ltd.). Commercially available organometallic catalysts containing Zn include, for example, K-KAT XK-314, K-KAT XK-635, K-KAT XK-639, and K-KAT XK-620 (all manufactured by Kusumoto Chemicals Co., Ltd.). An example of a commercially available organometallic catalyst containing Sn is TVS TIN LAU (manufactured by Nitto Kasei Co., Ltd.).

[0049] Conductive Pigment (C) The conductive pigment (C) is not particularly limited as long as it can impart conductivity to the coating film. The conductive pigment (C) may be in the form of particles, flakes, fibers, or whiskers. Examples of conductive pigments (C) include conductive carbons such as conductive carbon black, carbon nanotubes, carbon nanofibers, and carbon microcoils; metal powders such as silver, nickel, copper, graphite, and aluminum; antimony-doped tin oxide; phosphorus-doped tin oxide; acicular titanium oxide surface-coated with tin oxide / antimony; antimony oxide, zinc antimonate, indium tin oxide, and carbon or graphite whiskers surface-coated with tin oxide; flake-shaped mica pigments surface-coated with a conductive metal oxide such as tin oxide or antimony-doped tin oxide; and titanium dioxide particles surface-coated with tin oxide or phosphorus. These pigments may be used alone or in combination of two or more. Among these, conductive carbon and conductive carbon black may be used.

[0050] The DBP oil absorption of the conductive pigment (C) is 490 cm ３ The DBP oil absorption of the conductive pigment (C) is 450 cm ３ / 100g or less, 400cm ３ / 100g or less, 300cm ３ / 100g or less, 200cm ３ The DBP oil absorption of the conductive pigment (C) may be 50 cm ３ / 100g or more, 100cm ３ / 100g or more.

[0051] The DBP oil absorption of carbon black is measured in accordance with JIS K 6217-4, "Carbon black for rubber - Fundamental properties - Part 4, Determination of DBP absorption." The DBP oil absorption of other conductive pigments (C) is also measured in the same manner as that of carbon black.

[0052] The content of the conductive pigment (C) is, for example, 5 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the solid content of the polyol (A). This makes it easier to exhibit high conductivity while suppressing an increase in viscosity of the two-component coating composition. The content of the conductive pigment (C) may be 6 parts by mass or more, or may be 8 parts by mass or more. The content of the conductive pigment (C) may be 45 parts by mass or less, or may be 40 parts by mass or less.

[0053] The average particle diameter of the conductive pigment (C) is, for example, 10 nm or more and 50 μm or less. As a result, the DBP oil absorption is 490 cm ３ The conductive pigment (C) is easily dispersed in the base material and the two-component coating composition at a density of 100 g or less, and the conductive pigment (C) has improved dispersibility in the base material and the two-component coating composition. The conductive pigment (C) may have an average particle size of 20 nm or more, or 30 nm or more. The conductive pigment (C) may have an average particle size of 20 μm or less, 10 μm or less, or 1 μm or less.

[0054] The specific surface area of ​​the conductive pigment (C) is, for example, 30 m ２ / g or more 1500m ２ / g or less. This results in a DBP oil absorption of 490 cm ３ The specific surface area of ​​the conductive pigment (C) is easily 40 m / 100 g or less, and the dispersibility in the base material and the two-component coating composition can be improved. ２ / g or more, and ２ The specific surface area of ​​the conductive pigment (C) may be 1200 m / g or more. ２ / g or less, and ２ / g or less, and ２ / g or less.

[0055] Pigment dispersant (D) The pigment dispersant (D) is an additive used to uniformly disperse a pigment (including the conductive pigment (C)) in a solvent or polyol (A), and has a pigment-affinity moiety and a solvent-affinity moiety. The pigment-affinity moiety and the solvent-affinity moiety contain nonionic, cationic, or anionic functional groups. Two or more types of functional groups may be present in one molecule.

[0056] Examples of nonionic functional groups include hydroxyl groups, amide groups, and polyoxyalkylene groups. Examples of cationic functional groups include amino groups, imino groups, and hydrazino groups. Examples of anionic functional groups include carboxyl groups, sulfonic acid groups, and phosphate groups.

[0057] The pigment dispersant (D) is broadly classified into nonionic, cationic, and anionic dispersants depending on the type of functional group. From the viewpoint of dispersibility of the conductive pigment (C), the pigment dispersant (D) may be nonionic or cationic. The pigment dispersant (D) may be cationic.

[0058] The nonionic pigment dispersant typically has a polyoxyalkylene group and an alkyl chain having 14 or more carbon atoms, preferably 14 to 30, and more preferably 16 to 25. Examples of the nonionic pigment dispersant include polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene 2-octyldodidecyl ether, and modified products thereof (such as sulfate ester, phosphate ester, and maleate ester modified products).

[0059] Examples of cationic pigment dispersants include polymeric pigment dispersants having a cationic group at one or both ends of a main chain having a block structure or a graft structure. The number average molecular weight of the polymeric pigment dispersant is, for example, 2,000 to 1,000,000.

[0060] The amine value of the cationic pigment dispersant is, for example, 8 mgKOH / g or more, and may be 10 mgKOH / g or more. The amine value of the cationic pigment dispersant may be 100 mgKOH / g or less, 90 mgKOH / g or less, or 80 mgKOH / g or less.

[0061] The acid value of the cationic pigment dispersant is, for example, 2 mgKOH / g or more, and may be 5 mgKOH / g or more. The acid value of the cationic pigment dispersant may be 20 mgKOH / g or less, 15 mgKOH / g or less, or 10 mgKOH / g or less.

[0062] Examples of anionic pigment dispersants include phthalocyanine derivatives.

[0063] The pigment dispersant (D) can be prepared by a method known to those skilled in the art.

[0064] Examples of commercially available pigment dispersants (D) include the following. These may be used alone or in combination of two or more: Dispex Ultra series FA4404, FA4416, FA4425, FA4431, FA4437, FA4480, FA4483, PA4550, PA4560, PX4575, and PX4585 manufactured by BASF; and TEGO Dispers 650, 651, 652, 655, 660C, 715W, 740W, 750W, 752W, 755W, and 760W manufactured by Evonik. Lubrizol's Solsperse series: 12000S, 20000, 27000, 40000, 41090, 43000, 44000, 45000, 46000, 47000, 5000S, 53095, 64000, 65000, 66000, 67000, WV400 Kyoeisha Chemical's Flowlen series: G-700AMP, G-700DMEA, GW-1500, GW-1640 Kusumoto Chemicals' Disparlon series: DA-703-50, DA-7301, DN-900 BYK ANTI-TERRA-250, DISPERBYK series 102, 180, 184, 185, 187, 190, 191, 192, 193, 194N, 198, 199, 2010, 2012, 2013, 2015, 2096

[0065] The content of the pigment dispersant (D) is, for example, 5% by mass or more and 150% by mass or less relative to the mass of the conductive pigment (C) in terms of controlling the pigment dispersion state and the properties of the two-component coating composition. The content of the pigment dispersant (D) may be 7% by mass or more, or 10% by mass or more. The content of the pigment dispersant (D) may be 100% by mass or less, 50% by mass or less, or 30% by mass or less.

[0066] Other Pigments The base material may contain a pigment other than the conductive pigment (C). Examples of other pigments include non-conductive color pigments, luster pigments, and extender pigments.

[0067] Examples of luster pigments include metal flakes (aluminum, chromium, gold, silver, copper, brass, titanium, nickel, nickel chromium, stainless steel, etc.), metal oxide flakes, pearl pigments, glass flakes coated with metal or metal oxide, silica flakes coated with metal oxide, graphite, hologram pigments, and cholesteric liquid crystal polymers. These may be used alone or in combination of two or more.

[0068] Examples of color pigments include organic color pigments such as azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments; and inorganic color pigments such as yellow lead, yellow iron oxide, red iron oxide, non-conductive carbon black, and titanium dioxide. These may be used alone or in combination of two or more.

[0069] Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc, which may be used alone or in combination of two or more.

[0070] The DBP oil absorption of the other pigment is not particularly limited. The content of the other pigment is not particularly limited. The content of the other pigment may be appropriately set depending on the type, purpose, etc.

[0071] (Curing Agent) The curing agent crosslinks the coating film-forming resin such as polyol (A), improving the corrosion resistance and durability of the resulting coating film.

[0072] Isocyanurate Compound (E) The curing agent contains an isocyanurate compound (E). The isocyanurate compound (E) is a trimer of an isocyanate compound and has a ring structure.

[0073] The isocyanate compound is not particularly limited, and any known isocyanate compound may be used as a curing agent for two-component reactive compositions. Examples of the isocyanate compound include aromatic diisocyanates such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), and metaxylylene diisocyanate (MXDI); hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, and 2-methyl-pentane-1,5-diisocyanate. aliphatic diisocyanates such as 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate. These may be used alone or in combination of two or more.

[0074] Among these, aliphatic diisocyanates or HDI may be used because of their relatively low viscosity. Trimers of these isocyanates have particularly high reactivity with the polyol (A). Therefore, they are more preferably used in the coating layer formation method by in-mold coating.

[0075] The ratio of the isocyanate group equivalent of the isocyanate compound to the hydroxyl group equivalent of the polyol (A), i.e., NCO equivalent / OH equivalent, may be 0.5 / 1.0 or more and 2.0 / 1.0 or less, or 0.9 / 1.0 or more and 1.2 / 1.0 or less. When the equivalent ratio is within the above range, the composition has high curability and is particularly suitable for use in forming a coating layer by in-mold coating.

[0076] Other Curing Agents The curing agent may contain a curing agent other than the isocyanurate compound (E). Examples of other curing agents include amino resins, monomers or dimers of the above-mentioned isocyanate compounds, biuret derivatives of the above-mentioned isocyanate compounds, blocked products of the above-mentioned isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, and oxazoline compounds. These may be used alone or in combination of two or more.

[0077] (Solvent) The content of the solvent in the two-component coating composition is 30% by mass or less. This allows a cured coating film to be obtained quickly. Therefore, a coating film with excellent appearance and physical properties can be obtained by forming a layer by in-mold coating. The content of the solvent may be 10% by mass or less, or may be 0%.

[0078] The solvent is not particularly limited and is usually an organic solvent. Examples of organic solvents include ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethyl propionate, methyl propionate, 3-ethoxyethyl propionate (EEP), ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ether solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, methyl methoxybutanol, ethoxypropanol, ethylene glycol isopropyl ether, ethylene glycol-t-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methoxybutanol, and propylene glycol monobutyl ether; alcohol solvents such as methanol, ethanol, butanol, and propyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as Swazol, Shellsol, and mineral spirits; and aromatic solvents such as xylene, toluene, Solvesso-100 (S-100), and Solvesso-150 (S-150). These may be used alone or in combination of two or more.

[0079] (Others) The two-component coating composition may contain other components as needed. Examples of other components include additives commonly used in the coating and paint fields. Specific examples include surface conditioners, viscosity modifiers, antioxidants, UV inhibitors, antifoaming agents, catalyst assistants, rust inhibitors, and anti-settling agents. These additives may be added to the base agent or the curing agent. The amount of additive is not particularly limited and can be appropriately determined as needed.

[0080] [Multilayer Coating Film] The multilayer coating film comprises a primer coating film formed on an object to be coated, a base coating film formed on the primer coating film, and a clear coating film formed on the base coating film.

[0081] The substrate may be made of resin. In-mold coating is suitable for coating substrates made of resin.

[0082] The resin may be a thermoplastic resin or a thermosetting resin. Examples of the resin include polypropylene (PP) resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), polycarbonate (PC) / ABS resin, PC / acrylonitrile-ethylene-propylene-diene-styrene copolymer (AES resin), AES resin, PC / polybutylene terephthalate (PBT) resin, PC / polyethylene terephthalate (PET) resin, PC resin, polymethyl methacrylate (PMMA) resin, GF-PBT resin, GF-polyamide (PA) resin, Noryl GTX resin, polyvinyl chloride (PVC resin), acrylonitrile-styrene-acrylic (ASA) resin, carbon fiber reinforced plastic (CFRP resin), and glass fiber reinforced plastic (GFRP resin).

[0083] Primer Coating Film The primer coating film is formed from the two-component coating composition according to the present disclosure. The primer coating film is formed adjacent to the substrate.

[0084] The thickness of the primer coating film is not particularly limited and may be appropriately set depending on the purpose. The thickness of the primer coating film may be 80 μm or more and 500 μm or less.

[0085] Base Coating Film The base coating film is formed adjacent to the primer coating film. The base coating film imparts design properties to the multilayer coating film. The base coating film may be one or more layers, or may be two or more layers. The thickness of each layer of the base coating film after curing may be, for example, 5 μm or more and 60 μm or less.

[0086] The base coating film is formed from a base paint composition. The base paint composition may be aqueous or solvent-based. The base paint composition may be aqueous. An aqueous base paint composition contains, for example, an acrylic resin emulsion, a water-soluble acrylic resin, a curing agent (typically, a melamine resin), and a polyether polyol resin. The base paint composition may further contain the above-mentioned luster pigment, coloring pigment, and various additives. A solvent-based base paint composition contains an organic solvent as the main solvent. In a solvent-based base paint composition, the proportion of the organic solvent in the solvent is 50% by mass or more, may be 70% by mass or more, or may be 100% by mass.

[0087] Clear Coating Film The clear coating film is formed on the base coating film. The clear coating film improves the gloss of the multilayer coating film and prevents the pigment blended in the lower layer from falling off or popping out. The thickness of the clear coating film after curing may be 15 μm or more and 50 μm or less from the viewpoint of scratch resistance and smoothness.

[0088] The clear coating film is formed by a clear coating composition. The clear coating composition may be solvent-based, water-based, or powder-type. The clear coating composition may be solvent-based. From the viewpoints of transparency or acid etching resistance, the solvent-based clear coating composition may contain an acrylic resin and / or polyester resin as a film-forming resin, and an amino resin and / or isocyanate as a curing agent. The solvent-based clear coating composition may also contain an acrylic resin and / or polyester resin having a carboxylic acid and / or an epoxy group. The clear coating composition may contain the various pigments described above to the extent that transparency is not impaired. The clear coating composition may contain various additives as needed.

[0089] [Method for forming multi-layer coating film] The primer coating film is formed by in-mold coating. The method for forming other coating films is not particularly limited.

[0090] (Formation of Primer Coating Film) The primer coating film is formed by in-mold coating, that is, by applying the two-component coating composition according to the present disclosure to a substrate placed on one of the molds using a molding machine equipped with a pair of molds, and then curing the two-component coating composition inside the closed pair of molds.

[0091] The two-component coating composition may be poured between a pair of closed molds. Alternatively, the two-component coating composition may be applied to a substrate placed on one of the molds while the molds are open. In the latter case, after application of the two-component coating composition, the molds are closed and the two-component coating composition is spread over the substrate.

[0092] The two-component coating composition may be applied by the latter method. As described above, the two-component coating composition according to the present disclosure undergoes a relatively gentle curing reaction. Therefore, the two-component coating composition can maintain a fluidity sufficient to easily spread inside a mold by pressing the mold for a certain period of time.

[0093] The two-component coating composition is cured inside a pair of closed molds. The molds may be heated. This is because the curing reaction of the two-component coating composition is accelerated by heating. A two-component coating composition containing the curing catalyst (B) in the above amount can be cured gently even under heat. The heating temperature can be appropriately set taking into consideration the material of the substrate and the type of curing catalyst (B), etc. The heating temperature may be, for example, 70°C or higher and 130°C or lower, or 80°C or higher and 120°C or lower.

[0094] (Formation of base coating film and clear coating film) After the primer coating film is formed, the substrate is removed from the molding machine. Thereafter, a base coating composition is applied onto the primer coating film to form a base coating film, and then a clear coating composition is applied to form a clear coating film.

[0095] The coating method for each coating composition is not particularly limited, and examples of the coating method include air spray coating, airless spray coating, electrostatic spray coating, multi-stage coating by air electrostatic spray coating (typically, two-stage coating), and coating that combines air electrostatic spray coating and a rotary atomizer-type electrostatic coater.

[0096] When the clear coating composition is applied, the base coating film may be cured or uncured. From the viewpoints of productivity, adhesion, and water resistance, the base coating film may be laminated without curing (so-called wet-on-wet coating), and then these multiple uncured coating films may be cured at the same time.

[0097] Wet-on-wet coating involves applying a base coating composition onto a primer coating to form an uncured base coating, applying a clear coating composition onto the uncured base coating to form an uncured clear coating, and simultaneously curing the uncured base coating and the uncured clear coating.

[0098] After application of the base coating composition and before application of the clear coating composition, preheating may be carried out by, for example, leaving the substrate at a temperature of 20°C to 25°C for 5 to 15 minutes, or by heating the substrate at a temperature of 50°C to 80°C for 30 seconds to 10 minutes.

[0099] The curing of each coating composition is carried out, for example, under conditions of a heating temperature of 80° C. to 180° C. and a heating time of 5 to 60 minutes.

[0100] (Molding of the coated object) The resin coated object may be molded in the same molding machine. That is, the method of forming a multilayer coating film according to the present disclosure may include molding the coated object from the above-mentioned resin in a molding machine before forming the primer coating. For example, a resin melted by heating is injected between a pair of molds and cooled. This results in a coated object molded into a predetermined shape. The mold used to mold the coated object may be the same as or different from the mold used to form the primer coating.

[0101] The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0102] [Example 1] 100 parts of polyol (A-1), 0.3 parts of curing catalyst (B), 31 parts of conductive pigment (C-1), and pigment dispersant (D-1) were uniformly mixed in an amount of 10% by mass (solid content) relative to the mass of conductive pigment (C-1). The resulting mixed solution was then placed in a wide-mouth glass bottle, and an equal amount of glass beads with a diameter of approximately 1.2 mm were added as a dispersion medium. The bottle was then sealed and dispersed for 1 hour using a paint shaker. This yielded a base resin.

[0103] Separately, 176 parts of an isocyanurate compound (E-1) was prepared as a curing agent. The NCO / OH ratio was 1.0 / 1.0, and the solvent content of both the base resin and the curing agent was 0%.

[0104] In the table, the amount of curing catalyst (B) is shown as a percentage (PHR) relative to 100% by mass of the resin solids (polyol (A) and isocyanurate compound (E)). The amount of solvent is shown as a mass percentage relative to the entire two-component coating composition. The amount of pigment dispersant (D) is shown as a mass percentage relative to the conductive pigment (C).

[0105] Examples 2 to 11 and Comparative Examples 1 to 4 The base resin and the curing agent were prepared in the same manner as in Example 1, except that the type and amount of each component was changed as shown in Table 1.

[0106] The components in the table above are as follows. Polyols (A-1) Trade name: Desmophen VPLS2249 / 1, manufactured by Sumika Covestro Urethane Co., Ltd., polyester polyol, hydroxyl value 512 mg KOH / g, average number of hydroxyl groups 3 or more (A-2) Trade name: Sannix PP-200, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 560 mg KOH / g, average number of hydroxyl groups 2 (A-3) Trade name: Sannix PP-400, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 280 mg KOH / g, average number of hydroxyl groups 2 (A-4) Trade name: Sannix GP-600, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 280 mg KOH / g, average number of hydroxyl groups 3

[0107] Curing catalyst (B-1) Product name: TVS TIN LAU, manufactured by Nitto Kasei Co., Ltd., Sn-containing organometallic catalyst

[0108] Conductive pigment (C-1) Product name: MCP-10, manufactured by Nippon Graphite Co., Ltd., graphite, DBP oil absorption 140 cm ３ / 100g, average particle size 10μm, specific surface area 5m ２ / g (C-2) Product name: #3050B, manufactured by Mitsubishi Chemical Corporation, conductive carbon black, DBP oil absorption 175 cm ３ / 100g, average particle diameter 50nm, specific surface area 50m ２ / g (C-3) Trade name: VULCAN XC-72, manufactured by CABOT, conductive carbon black, DBP oil absorption 175 cm ３ / 100g, average particle diameter 30nm, specific surface area 254m ２ / g (C-4) Trade name: PRINTEX XE-2b, manufactured by Orion Engineered Carbons, conductive carbon black, DBP oil absorption 420 cm ３ / 100g, average particle diameter 30nm, specific surface area 1050m ２ / g (C-5) Product name: Ketjenblack EC600JD, manufactured by Lion Specialty Chemicals, conductive carbon black, DBP oil absorption 495 cm ３ / 100g, average particle diameter 34nm, specific surface area 1400m ２ / g

[0109] Other pigments (c-1) Product name: TIPAQUE CR-95, manufactured by Ishihara Sangyo Kaisha, Ltd., titanium oxide

[0110] Pigment dispersant (D-1) Trade name: DISPERBYK-2013, manufactured by BYK, styrene-maleic anhydride copolymer, acid value 8 mg KOH / g, amine value 18 mg KOH / g (D-2) Trade name: SOLSPERSE5000S, manufactured by Lubrizol, phthalocyanine derivative

[0111] Isocyanurate compound (E-1) Trade name: Desmodur N3300, manufactured by Sumika Covestro Urethane Co., Ltd., HDI trimer, number average molecular weight 550

[0112] The main components prepared in the examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.

[0113] (1) TI value of base resin Using a cone-plate type viscometer (trade name: DHR-3, manufactured by TA Instruments), the TI value of the base resin was measured at a shear rate of 1 sec at a temperature of 60°C. －１ and 100 sec －１ The viscosity LSV and HSV were measured at this time. The TI value was calculated using the following formula: TI value = LSV / HSV

[0114] (2) Pigment Dispersibility of Base Agent The base agent was heated to 80°C and pre-mixed using a Homo Disper. Next, the base agent was dispersed for 1 hour using a paint shaker with the same amount of glass beads as the base agent. Thereafter, the diameter of the dispersed particles contained in the base agent was measured using a grind gauge in accordance with JIS K 5600-2-5. The measured particle diameters were evaluated according to the following criteria. A rating of C or higher can be evaluated as good pigment dispersibility.

[0115] (Evaluation criteria) A: Pre-mixing is possible, and the dispersed particle size is 15 μm or less. B: Pre-mixing is possible, and the dispersed particle size is more than 15 μm and 50 μm or less. C: Pre-mixing is possible, and the dispersed particle size is more than 50 μm. -: Pre-mixing is not possible because the torque of the homodisper is exceeded, and particle size measurement is also not possible.

[0116] (3) Coating Workability A curing agent was added to the base agent. After adding the curing agent, the mixture was mixed for 15 seconds and then a sample was removed. The time when the sample was removed was considered to be the start of the coating work. The removed sample was stirred with a spatula, and the time when the sample no longer fell from the spatula was considered to be the end of the coating work. The time required from the start to the end of the coating work was calculated as the coating work time and evaluated according to the following criteria. A rating of B or higher was considered to be suitable for in-mold coating.

[0117] (Evaluation criteria) A: 60 seconds or more and less than 600 seconds B: 30 seconds or more and less than 60 seconds, or 600 seconds or more and less than 900 seconds C: Less than 30 seconds, or 900 seconds or more -: The sample was completely cured during mixing

[0118] Two-component coating compositions were prepared from the base resins and curing agents prepared in the Examples and Comparative Examples, and in-mold coated onto substrates using the following method. The resulting primer coatings were evaluated as follows. The evaluation results are shown in Table 1.

[0119] (Formation of primer coating film) In a molding machine equipped with a pair of molds, the substrate (GFRP substrate) was placed in one of the molds. The molds were then closed, and the two-component coating composition was injected between the pair of molds. The molds were heated to 100°C and pressurized at 3 MPa, and maintained for 5 minutes. This formed a cured primer coating film (film thickness 200 μm) on the substrate.

[0120] (4) Appearance The appearance of the primer coating film was visually evaluated according to the following criteria: A rating of B or higher indicates that the appearance is good.

[0121] (Evaluation criteria) A: No generation of granular matter, entrapment of bubbles, or formation of voids (holes where air can easily accumulate) is observed B: Some entrapment of bubbles is observed C: One or more of the generation of granular matter, entrapment of bubbles, or formation of voids (holes where air can easily accumulate) is clearly observed D: One or more of the generation of granular matter, entrapment of bubbles, or formation of voids (holes where air can easily accumulate) is clearly observed, and the coating composition has hardened without wetting and spreading, or the coating composition has leaked, exposing the surface of the coated object -: In-mold coating is not possible

[0122] (5) Electrical Conductivity The surface resistance of the primer coating film was measured using a surface resistance meter (76634-00, manufactured by Ransburg) and evaluated according to the following criteria. A rating of C or higher indicates electrical conductivity. A: 1 × 10 ７ Ω / □ or less B: 1 x 10 ７ Ω / □ or more 1×10 ９ Less than Ω / □ C: 1 x 10 ９ Ω / □ or more 1×10 １０ Ω / □ or less D: 1 x 10 １０ Ω / □ or more -: In-mold coating not possible

[0123] (6) Adhesion The cutting blade of an NT Cutter S type (manufactured by NT Corporation) was held at approximately 30 degrees to the coating surface, and slits (11 vertical lines, 11 horizontal lines, 2 mm intervals) reaching the substrate were made into 100 grids on the primer coating. Adhesive tape (Nichiban Corporation, Cellotape (registered trademark), 24 mm wide) was evenly applied with fingertips to cover all the grids, ensuring no air bubbles remained. The adhesive tape was immediately peeled off while being pulled so that the angle between the tape and the coating was approximately 90°. After peeling the tape, the number of grids with remaining coating was counted and evaluated according to the following criteria. The more grids with remaining coating, the better the adhesion. A rating of B or higher was considered to be good adhesion.

[0124] (Evaluation criteria) A: Number of squares is 91 or more B: Number of squares is 50 to 90 C: Number of squares is 20 to 49 D: Number of squares is 19 or less -: In-mold coating cannot be performed

[0125]

[0126] All of the two-component coating compositions in the examples exhibited excellent coating workability. The coating films formed by in-mold coating using these coating compositions exhibited excellent appearance, conductivity, and adhesion. Comparative Example 1 is an example in which the oil absorption of the conductive pigment (C) contained in the coating composition was outside the range of the present disclosure. In this example, the viscosity of the base resin was very high, resulting in poor pigment dispersibility. As a result, in-mold coating was not possible. Comparative Example 2 is an example in which the hydroxyl value of the polyol (A) contained in the coating composition was outside the range of the present disclosure. In this example, in-mold coating was possible, but the coating film exhibited poor adhesion. Comparative Example 3 is an example in which the content of the curing catalyst (B) was higher than the range of the present disclosure. In this example, the viscosity of the coating composition became very high immediately after mixing the base resin and curing agent, making in-mold coating impossible. Comparative Example 4 is an example in which the content of the solvent contained in the coating composition was high. In this example, the two-component coating composition exhibited excellent pigment dispersibility and coating workability. However, the coating film exhibited poor appearance, conductivity, and adhesion.

[0127] Example 12 A primer coating film was formed in the same manner as above using the two-component coating composition of Example 1. A one-component silver base paint composition (product name: R-333, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was electrostatically applied onto the primer coating film to a dry film thickness of 15 μm to form an uncured base coating film.

[0128] Next, a two-component urethane curing clear coating composition was prepared by mixing a base agent (product name: R-2810-603-1, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) and a curing agent (R-271 Curing Agent, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) in a mass ratio of 100 / 40. This clear coating composition was electrostatically applied onto an uncured base coating film to a dry film thickness of 25 μm. The coating was then left to stand for 10 minutes and baked at 90°C for 45 minutes to obtain a multilayer coating film consisting of a primer coating film, a base coating film, and a clear coating film.

[0129] The resulting multi-layer coating film had a good appearance, which suggests that the primer coating film had good electrical conductivity.

[0130] The two-component coating composition of the present invention can be suitably used for in-mold coating.

[0131] This application claims priority based on Japanese Patent Application No. 2023-214684, filed on December 20, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A two-component coating composition comprising a base agent and a curing agent, wherein the base agent comprises a polyol (A), a curing catalyst (B), a conductive pigment (C) and a pigment dispersant (D), the curing agent comprises an isocyanurate compound (E), the hydroxyl value of the polyol (A) is 300 mgKOH / g or more and 1000 mgKOH / g or less, the content of the curing catalyst (B) is 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the solid content of the polyol (A), and the conductive pigment (C) has a DBP oil absorption of 490 cm ３ / 100g or less, and a content of a solvent contained in the two-component coating composition is 30 mass% or less.

2. The two-component coating composition according to claim 1, wherein the polyol (A) comprises a first polyester polyol having three or more hydroxyl groups and a branched structure.

3. The two-component coating composition according to claim 2, wherein the proportion of the first polyester polyol in the total content of the polyol (A) is 35 mass% or more.

4. The base material is heated at 60°C and a shear rate of 1.0 sec. －１ The low shear viscosity LSV (mPa·s) measured under the conditions of 60°C, shear rate 100 sec －１ 4. The two-component coating composition according to claim 1, wherein the TI value (LSV / HSV) obtained by dividing the TI value by the high shear viscosity HSV (mPa·s) measured under the conditions of 5. The two-component coating composition according to any one of claims 1 to 4, wherein the content of the conductive pigment (C) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the solid content of the polyol (A).

6. The two-component coating composition according to any one of claims 1 to 5, wherein the polyol (A) comprises at least one selected from the group consisting of polyester polyols, polyether polyols, and polycarbonate polyols.

7. The two-component coating composition according to any one of claims 1 to 6, which is used for forming a primer coating film.

8. A method for forming a multi-layer coating film comprising: applying a two-component coating composition according to any one of claims 1 to 7 to a substrate placed on one of the substrates using a molding machine equipped with a pair of dies, and then curing the two-component coating composition inside the pair of closed dies to form a primer coating film; after removing the substrate from the molding machine, applying a base paint composition onto the primer coating film to form an uncured base coating film; applying a clear paint composition onto the uncured base coating film to form an uncured clear coating film; and curing the uncured base coating film and the uncured clear coating film.

Images