Two-pack type coating composition for in-mold coating

Abstract

To provide a two-pack type coating composition for in-mold coating that comprises an electroconductive pigment.SOLUTION: A two-pack type coating composition for in-mold coating comprises a main preparation and a curing agent, wherein the main preparation includes 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 mgKOH / g or more and 1000 mgKOH / g or less, the content of the curing catalyst (B) is 0.05 pt.mass or more and 3 pts.mass or less relative to 100 pts.mass of the polyol (A), the electroconductive pigment (C) has a DBP oil absorption of 490 cm3 / 100 g or less, and the content of a solvent contained in the two-pack type coating composition is 30 mass% or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Coating films having various functions are formed on the surfaces of industrial products and the like. The coating film protects the object to be coated and at the same time imparts a beautiful appearance and an excellent design. The coating film is generally formed by spray-coating a coating composition containing a solvent such as an organic solvent and / or an aqueous solvent and then drying it. However, in recent years, problems such as the scattering of solvents during spray coating, the emission of solvents into the atmosphere during the drying process, and the generation of CO2 have been regarded as issues. Furthermore, since spray coating requires a drying process, productivity is likely to decrease.

[0003] Therefore, as a coating method alternative to spray coating, in-mold coating, which performs coating in a mold, has been proposed. Patent Document 1 discloses a coating composition used for in-mold coating.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides the following aspects. [1] A two-component coating composition containing a main agent and a curing agent, The main agent contains a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D), The curing agent contains 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 with respect to 100 parts by mass of the solid content of the polyol (A), The conductive pigment (C) has a DBP oil absorption of 490 cm 3 / 100 g or less, A two-component coating composition for in-mold coating, wherein the content of the solvent contained in the two-component coating composition is 30% by mass or less. [2] The two-component coating composition according to [1] above, wherein the polyol (A) contains a first polyester polyol (A) having three or more hydroxyl groups and a branched structure. [3] The two-component coating composition according to [2] above, wherein the proportion of the first polyester polyol (A) in the total content of the polyol (A) is 35% by mass or more. [4] The main agent has a TI value (LSV / HSV) obtained by dividing the low-shear viscosity LSV (mPa·s) measured under the conditions of a shear rate of 1.0 sec -1 at 60 °C by the high-shear viscosity HSV (mPa·s) measured under the conditions of a shear rate of 100 sec -1 at 60 °C, which is 2.0 or more and 200 or less. The two-component coating composition according to [1] or [2] above. [5] The content of the conductive pigment (C) is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the polyol (A). The two-component coating composition according to [1] or [2] above. [6] The two-component coating composition according to the above [1], wherein the polyol (A) contains at least one selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol. [7] The two-component coating composition according to the above [1] or [2], which is for forming a primer coating film. [8] After applying the two-component coating composition according to the above [1] to an object to be coated disposed on one of a pair of molds using a molding machine equipped with the pair of molds, the two-component coating composition is cured inside the closed pair of molds to form a primer coating film. After taking out the object to be coated from the molding machine, a base paint composition is applied onto the primer coating film to form an uncured base coating film. A clear paint composition is applied onto the uncured base coating film to form an uncured clear coating film. A method for forming a multilayer coating film, comprising curing the uncured base coating film and the uncured clear coating film.

Effect of the Invention

[0007] According to the present invention, a two-component coating composition for in-mold coating containing a conductive pigment can be provided.

Mode for Carrying Out the Invention

[0008] In in-mold coating, a molding machine having a pair of molds (for example, a cavity and a core) is used. An object to be coated is disposed on one of the molds, and a coating composition is applied to the object to be coated. Thereafter, the coating composition is cured in a state where the pair of molds is closed (that is, a state where pressure is applied to the coating composition), and a coating film is formed on the object to be coated.

[0009] According to in-mold coating, since the coating film is formed in the mold, it is possible to suppress the adhesion of dust or the like between the object to be coated and the coating film, and the mixing of dust or the like into the coating film. In addition, since it is hardly affected by the surface state of the object to be coated, the pattern of the mold can be transferred to the coating film with high precision. In addition, since the amount of solvent contained in the coating composition is small, a drying process for removing the solvent is not required, and productivity is improved. Furthermore, it is possible to form a thick coating film with suppressed sagging and running.

[0010] Generally, a plurality of coating films having various functions are formed on the surface of an object to be coated such as an automobile body. One of the coating films is a primer coating film. The conductive primer coating film is formed on a resin object to be coated. By the conductive primer coating film, other coating films can be formed by electrostatic coating.

[0011] Conductivity is imparted by using a conductive pigment. When the conductive pigment forms an electric conduction path, conductivity in the thickness direction of the coating film is exhibited. A conductive pigment with a small particle size generally easily forms an electric conduction path. On the other hand, a conductive pigment with a small particle size increases the viscosity of the coating composition. In particular, since the coating composition for in-mold coating has a small amount of solvent, the viscosity is more likely to increase. When the viscosity of the coating composition is high, it becomes difficult to apply it uniformly to the object to be coated. In addition, when the coating composition is applied, the object to be coated may be heated by the mold, and the curing reaction of the coating composition may proceed in parallel. In this case, it is even more important that the coating composition has a low viscosity. It can be said that generally, it is difficult to achieve both high conductivity and low viscosity.

[0012] In the present disclosure, in a two-component coating composition for in-mold coating with a small amount of solvent, the DBP oil absorption is 490 cm 3A conductive pigment (C) of 100 g or less is used. A small DBP oil absorption means a small specific surface area of the pigment, which also means a relatively large particle size. That is, by using a pigment with a small DBP oil absorption, an increase in the viscosity of the two-component coating composition is suppressed, and the dispersibility of the conductive pigment (C) is improved. Therefore, an energization path is easily formed, and the coating film exhibits high conductivity.

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

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

[0015] The amine value can be determined by the following method in accordance with ASTM D2073. (1) Weigh 500 mg of the object accurately into a 200 ml Erlenmeyer flask. (2) Add about 50 ml of glacial acetic acid and dissolve it uniformly. (3) Add 5 to 6 drops of an indicator (methyl violet solution) and stir uniformly. (4) Titrate with a 0.1 N perchloric acid acetic acid solution, and take the point when it turns bright green as the end point. (The above (3) and (4) may be replaced by potentiometric titration.)

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

[0017] [Two-component coating composition] The two-component coating composition according to the present disclosure includes a main agent and a curing agent. The main agent includes a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D). The curing agent includes an isocyanurate compound (E). By mixing the main agent and the curing agent, the polyol (A) reacts with the isocyanurate compound (E) to obtain a cured coating film. The main agent and / or the curing agent may each be heated and / or vacuum degassed before mixing. Thereby, the water content in the two-component coating composition obtained by mixing the two is reduced, and the appearance of the obtained coating film is likely to be improved.

[0018] The two-component coating composition according to the present disclosure is for in-mold coating. Since the two-component coating composition according to the present disclosure has conductivity and excellent adhesion to an object to be coated, it is particularly suitable for forming a primer coating film.

[0019] The two-component coating composition can have an application working time measured by the following test of 30 seconds or more and less than 900 seconds. When the application working time is 30 seconds or more and less than 900 seconds, in in-mold coating, it can be considered that the two-component coating composition can maintain suitable fluidity from the start of application to the object to be coated until completion. Due to the appropriate fluidity, the two-component coating composition easily spreads inside the mold. Thereafter, by stopping the flow of the two-component coating composition, a uniform primer coating film can be formed. The application working time can be used to evaluate whether the two-component coating composition is suitable for in-mold coating.

[0020] In in-mold coating, the application period, which is the period from the start to the completion of applying the two-component coating composition to the object to be coated, corresponds to the following periods. When the two-component coating composition is injected between a pair of closed molds (i.e., between the object to be coated 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 operation time of 30 seconds or more and less than 600 seconds is suitable. Also, when the two-component coating composition is applied to the object to be coated 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 on the object to be coated, to the stop of the movement of the mold. In this case, a two-component coating composition with a coating operation time of 60 seconds or more and less than 900 seconds is suitable. If the coating operation time is 60 seconds or more and less than 600 seconds, the two-component coating composition can be applied in either case.

[0021] · Measurement test of coating operation time After adding the curing agent to the main agent in a disposable container, mix with a spatula for 15 seconds. The time when mixing is completed is taken as the start of the coating operation. Stir the sample with a spatula in the container, and the time when the sample does not fall from the container even when the container is turned upside down is taken as the end of the coating operation. The time required from the start to the end of the coating operation is taken as the coating operation time.

[0022] (Main agent) The main agent 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 the curing agent by heating, for example, to form a three-dimensional cured coating film. Hereinafter, the curable resin containing the polyol (A) contained in the two-component coating composition may be generically referred to as the film-forming resin.

[0023] The main agent may have a TI value (LSV / HSV) obtained by dividing the low-shear viscosity LSV (mPa·s) measured at 60°C under a shear rate of 1.0 sec-1 by the high-shear viscosity HSV (mPa·s) measured at 60°C under a shear rate of 100 sec-1, which is 2.0 or more and 200 or less. When the TI value (LSV / HSV) of the main agent is 2.0 or more and 200 or less, it can be said that the coating composition has high thixotropy. That is, when applied to the object to be coated, the viscosity of the coating composition is sufficiently low. Therefore, it can be said that the conductive pigment (C) is well dispersed. On the other hand, the viscosity of the coating composition after application is sufficiently high, and the conductive pigment (C) can exist in the coating film while maintaining a high dispersion state. Therefore, many conductive paths are formed, and the conductivity of the coating film is further improved.

[0024] The LSV of the main agent is not particularly limited. In terms of being able to achieve higher conductivity, the LSV of the main agent is, for example, 1,000 mPa·s or more and 150,000 mPa·s or less. The LSV of the main agent may be 5,000 mPa·s or more, may be 7,000 mPa·s or more, and may be 10,000 mPa·s or more. The LSV of the main agent may be 100,000 mPa·s or less, may be 80,000 mPa·s or less, and may be 70,000 mPa·s or less.

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

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

[0027] The hydroxyl value of the polyol (A) (including the apparent hydroxyl value; the same shall apply hereinafter) 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 object to be coated (especially an object to be coated made of resin) is improved. Further, when the main agent and the curing agent are mixed, the reaction rate between the polyol (A) and the isocyanurate compound (E) increases, so that the coated product can be quickly released from the mold, and the productivity is improved. 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.

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

[0029] The apparent hydroxyl value is calculated based on the hydroxyl value and mass ratio of each polyol when two or more kinds of polyols are contained. Specifically, the apparent hydroxyl value in the case of containing polyols A and B is obtained by (hydroxyl value of polyol A × mass ratio of polyol A) + (hydroxyl value of polyol B × mass ratio of polyol B).

[0030] As long as the apparent hydroxyl value is 300 mgKOH / g or more and 1000 mgKOH / g or less, the main agent may contain a plurality of kinds of polyols having different hydroxyl values. The main agent may contain, for example, a polyol having a hydroxyl value of less than 300 mgKOH / g and / or a polyol having a hydroxyl value exceeding 1000 mgKOH / g.

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

[0032] The polyol (A) may have an average of 3 or more hydroxyl groups per molecule. Thereby, the hardness of the obtained coating film tends to be high.

[0033] The polyol (A) may contain a first polyester polyol having three or more hydroxyl groups and a branched structure. Thereby, the conductivity is further improved. The reason for this is not clear, but it is considered as follows. The first polyester polyol makes it easier to form a network by the crosslinked resin. Since the conductive particles are fixed to this resin network, it is considered that an energization path is also easily formed.

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

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

[0036] Examples of commercially available polyester polyols include Desmophen VPLS2249 / 1 (manufactured by Sumika Covestro Polyurethanes Co., Ltd.), Desmophen 800 (manufactured by Sumika Covestro Polyurethanes Co., Ltd.), Desmophen XP2488 (manufactured by Sumika Covestro Polyurethanes Co., Ltd.), 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 their block copolymers. Polyether polyols can be obtained, for example, by adding ethylene oxide and / or propylene oxide to a polyhydric alcohol compound.

[0038] Examples of commercially available polyether polyols include the Sun Nix series manufactured by Sanyo Chemical Industries, Ltd. Specifically, Sun Nix GP-250, Sun Nix GP-400, Sun Nix PP-200, and Sun Nix GP-600 can be mentioned.

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

[0040] Examples of commercially available polycarbonate polyols include 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 polyol (A) is not particularly limited. The Mw of polyol (A) can be appropriately set according to the hydroxyl value, etc.

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

[0044] · Curing catalyst (B) The curing catalyst (B) promotes 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 with respect to 100 parts by mass of the solid content of the polyol (A). Thereby, the curing reaction proceeds relatively gently, and the two-component coating composition can maintain a fluidity suitable for in-mold coating for a certain period.

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

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

[0047] Examples of the organometallic catalyst containing Bi include bismuth carboxylic acid and its salts. Examples of the organometallic catalyst containing Zn include zinc complex catalysts. Examples of the organometallic catalyst containing Al include aluminum complex catalysts. Examples of the organometallic catalyst containing Zr include zirconium chelate catalysts. Examples of the organometallic catalyst 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 are used alone or in combination of two or more.

[0048] Examples of the commercially available products of the organometallic catalyst containing Bi include K-KAT 348 (manufactured by Kusumoto Chemical Co., Ltd.) and K-KAT XK-640 (manufactured by Kusumoto Chemical Co., Ltd.). Examples of the commercially available products of the organometallic catalyst containing Zr include K-KAT 4205, K-KAT XC-9213, K-KAT XC-A209, and K-KAT 6212 (all manufactured by Kusumoto Chemical Co., Ltd.). Examples of the commercially available products of the organometallic catalyst containing Al include K-KAT 5218 (manufactured by Kusumoto Chemical Co., Ltd.). Examples of the commercially available products of the organometallic catalyst containing Zn include K-KAT XK-314, K-KAT XK-635, K-KAT XK-639, and K-KAT XK-620 (all manufactured by Kusumoto Chemical Co., Ltd.). Examples of the commercially available products of the organometallic catalyst containing Sn include 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 any shape such as particulate, flaky, fibrous or whisker-like. Examples of the conductive pigment (C) include conductive carbons such as conductive carbon black, carbon nanotubes, carbon nanofibers, carbon microcoils; metal powders such as silver, nickel, copper, graphite, aluminum; tin oxide doped with antimony; tin oxide doped with phosphorus; acicular titanium oxide surface-coated with tin oxide / antimony; antimony oxide surface-coated with tin oxide, zinc antimonate, indium tin oxide and carbon or graphite whiskers; flaky mica pigments surface-coated with conductive metal oxides such as tin oxide or antimony-doped tin oxide; titanium dioxide particles surface-coated with tin oxide or phosphorus. These may be used singly or in combination of two or more. Among them, it may be conductive carbon, and may be conductive carbon black.

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

[0051] The DBP oil absorption of carbon black is measured in accordance with "Carbon black for rubber - Basic properties - Part 4, Method for determining DBP absorption" specified in JIS K 6217-4. 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 with respect to 100 parts by mass of the solid content of the polyol (A). Thereby, while suppressing an increase in the viscosity of the two-component coating composition, high conductivity is more likely to be exhibited. The above content of the conductive pigment (C) may be 6 parts by mass or more, and may be 8 parts by mass or more. The above content of the conductive pigment (C) may be 45 parts by mass or less, and 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. Thereby, the DBP oil absorption amount is likely to be 490 cm 3 / 100 g or less, and the dispersibility in the main agent and the two-component coating composition can be improved. The average particle diameter of the conductive pigment (C) may be 20 nm or more, and may be 30 nm or more. The average particle diameter of the conductive pigment (C) may be 20 μm or less, may be 10 μm or less, and may be 1 μm or less.

[0054] The specific surface area of the conductive pigment (C) is, for example, 30 m 2 / g or more and 1500 m 2 / g or less. Thereby, the DBP oil absorption amount is likely to be 490 cm 3 / 100 g or less, and the dispersibility in the main agent and the two-component coating composition can be improved. The specific surface area of the conductive pigment (C) may be 40 m 2 / g or more, and may be 50 m 2 / g or more. The specific surface area of the conductive pigment (C) may be 1200 m 2 / g or less, may be 1100 m 2 / g or less, and may be 500 m 2 / g or less.

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

[0056] Examples of the nonionic functional group include a hydroxyl group, an amide group, and a polyoxyalkylene group. Examples of the cationic functional group include an amino group, an imino group, and a hydrazino group. Examples of the anionic functional group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

[0057] The pigment dispersant (D) is roughly classified into nonionic, cationic, or anionic according to the type of the functional group. From the viewpoint of the dispersibility of the conductive pigment (C), the pigment dispersant (D) may be nonionic or cationic. The pigment dispersant (D) may be cationic.

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

[0059] Examples of the cationic pigment dispersant include a polymer pigment dispersant having a cationic group at one end or both ends of the main chain having a block structure or a graft structure. The number average molecular weight of the polymer 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, may be 90 mgKOH / g or less, and may be 80 mgKOH / g or less.

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

[0062] Examples of the anionic pigment dispersant include phthalocyanine derivatives.

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

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

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

[0066] ·Other pigments The main agent may contain pigments other than the conductive pigment (C). Examples of other pigments include non-conductive coloring pigments, bright pigments, and extender pigments.

[0067] Examples of bright pigments include metal flakes (aluminum, chromium, gold, silver, copper, brass, titanium, nickel, nickel chrome, 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 are used alone or in combination of two or more.

[0068] Examples of coloring pigments include organic coloring 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: inorganic coloring pigments such as lead yellow, yellow iron oxide, red iron oxide, non-conductive carbon black, and titanium dioxide. These are used alone or in combination of two or more.

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

[0070] The DBP oil absorption of other pigments is not particularly limited. The content of other pigments is not particularly limited. The content of other pigments may be appropriately set according to their types, purposes, etc.

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

[0072] · Isocyanurate compound (E) The hardener 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 those known as hardeners for two-component reaction-type compositions are used. 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); aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 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 xylylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate. These may be used alone or in combination of two or more.

[0074] Among them, it may be an aliphatic diisocyanate, and may be HDI, in terms of relatively low viscosity. The trimers of these isocyanates have particularly high reactivity with polyol (A). Therefore, they are more preferably used in the method for forming a coating layer 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): NCO equivalent / OH equivalent may be 0.5 / 1.0 or more and 2.0 / 1.0 or less, and may be 0.9 / 1.0 or more and 1.2 / 1.0 or less. When the equivalent ratio is within the above range, the curability is high, and it is particularly preferably used for forming a coating layer by in-mold coating.

[0076] ·Other curing agents The curing agent may contain other curing agents other than the isocyanurate compound (E). Examples of other curing agents include amino resins, monomers or dimers of the above isocyanate compounds, biuret bodies of the above isocyanate compounds, blocked products of the above 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 contained in the two-component coating composition is 30% by mass or less. Thereby, a cured coating film can be obtained promptly. Therefore, by forming a layer by in-mold coating, a coating film excellent in appearance and physical properties can be obtained. The content of the solvent may be 10% by mass or less, and may be 0%.

[0078] The solvent is not particularly limited. The solvent is usually an organic solvent. Examples of the organic solvent include ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethyl propionate, methyl propionate, ethyl 3-ethoxypropionate (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, shellzol, and mineral spirit; and aromatic solvents such as xylene, toluene, Solvesso - 100 (S - 100), and Solvesso - 150 (S - 150). These can be used alone or in combination of two or more.

[0079] (Others) The two - component coating composition may contain other components as necessary. Examples of the other components include additives that can be usually used in the coating field and paint field. Specifically, surface modifiers, viscosity modifiers, antioxidants, ultraviolet light inhibitors, defoamers, catalyst aids, rust preventives, and anti - settling agents are included. These additives may be added to the main agent or the curing agent. The amount of the additive is not particularly limited and can be appropriately set as necessary.

[0080] [Multi - layer coating film] The multi - layer coating film includes a primer coating film formed on the 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] ·Object to be coated The object to be coated may be made of resin. In-mold coating is suitable for coating resin-made objects to be coated.

[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 by the two-component coating composition according to the present disclosure. The primer coating film is formed adjacent to the object to be coated.

[0084] The thickness of the primer coating film is not particularly limited and is appropriately set according to 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 has one or more layers and may have two or more layers. The thickness of each layer of the cured base coating film 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 may contain, 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-described brightening pigment, coloring pigment, and various additives. A solvent-based base paint composition contains an organic solvent as a main solvent. In the solvent-based base paint composition, the proportion of the organic solvent in the solvent may be 50% by mass or more, may be 70% by mass or more, and 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 incorporated in the lower layer from dropping out and protruding. The thickness of the clear coating film after curing may be 15 μm or more and 50 μm or less from the viewpoints of scratch resistance and smoothness.

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

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

[0090] (Formation of the primer coating film) The primer coating film is formed by in-mold coating. That is, the primer coating film is formed by applying the two-component coating composition according to the present disclosure to an object to be coated disposed on one mold 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 injected between the closed pair of molds. The two-component coating composition may also be applied to an object to be coated disposed on one mold with the mold being open. In the latter case, the mold is closed after the application of the two-component coating composition, and the two-component coating composition is spread over the object to be coated.

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

[0093] The two-component coating composition is cured inside the closed pair of molds. The mold may be heated. This is because the curing reaction of the two-component coating composition is promoted by heating. The two-component coating composition containing the curing catalyst (B) in the above amount can cure gently even under heating. The heating temperature can be appropriately set in consideration of the material of the object to be coated, the type of the 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 formation of the primer coating film, the object to be coated is taken out from the molding machine. Then, a base paint composition is applied onto the primer coating film to form a base coating film, and then a clear paint composition is applied to form a clear coating film.

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

[0096] When applying the clear coating composition, the base coating film may be cured or uncured. From the viewpoints of productivity, adhesion, and water resistance, after laminating (so-called wet-on-wet coating) without curing the base coating film, these plurality of uncured coating films may be cured at once.

[0097] Wet-on-wet coating includes applying a base coating composition on a primer coating film to form an uncured base coating film, applying a clear coating composition on 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 at once.

[0098] Before applying the clear coating composition after applying the base coating composition, preheating may be performed. The preheating is performed, for example, by a method of leaving it for 5 minutes or more and 15 minutes or less under temperature conditions of 20°C or more and 25°C or less, or by a method of heating it for 30 seconds or more and 10 minutes or less under temperature conditions of 50°C or more and 80°C or less.

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

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

Example

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

[0102] [Example 1] 100 parts of polyol (A-1), 0.3 part of curing catalyst (B), 31 parts of conductive pigment (C-1), and a pigment dispersant (D-1) in an amount of 10% by mass (solid content) based on the mass of the conductive pigment (C-1) were uniformly mixed. Next, the obtained mixed solution was put into a wide-mouth glass bottle, the same amount of glass beads with a diameter of about 1.2 mm as the mixed solution was added as a dispersion medium, and the bottle was sealed and dispersed with a paint shaker for 1 hour. Thus, the main agent was obtained.

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

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

[0105] [Examples 2 to 11 and Comparative Examples 1 to 4] The main agent and the curing agent were prepared in the same procedure as in Example 1, except that the types and amounts of each component were changed as described in Table 1.

[0106] The components in the above table are as follows. · Polyol (A-1) Product Name: Desmophen VPLS2249 / 1, manufactured by Sumitomo Chemical Covestro Polyurethane Co., Ltd., polyester polyol, hydroxyl value 512 mgKOH / g, average number of hydroxyl groups 3 or more (A-2) Product Name: Sunnex PP-200, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 560 mgKOH / g, average number of hydroxyl groups 2 (A-3) Product Name: Sunnex PP-400, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 280 mgKOH / g, average number of hydroxyl groups 2 (A-4) Product Name: Sunnex GP-600, manufactured by Sanyo Chemical Industries, Ltd., polyether polyol, hydroxyl value 280 mgKOH / g, average number of hydroxyl groups 3

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

[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 10 μm, specific surface area 5 m 2 / g (C-2) Product Name: #3050B, manufactured by Mitsubishi Chemical Corporation, conductive carbon black, DBP oil absorption 175 cm 3 / 100g, average particle size 50 nm, specific surface area 50 m 2 / g (C-3) Product Name: VULCAN XC-72, manufactured by CABOT Corporation, conductive carbon black, DBP oil absorption 175 cm 3 / 100g, average particle size 30 nm, specific surface area 254 m 2 / g (C-4) Product Name: PRINTEX XE-2b, manufactured by Orion Engineered Carbons, conductive carbon black, DBP oil absorption 420 cm 3 / 100g, average particle size 30 nm, specific surface area 1050 m 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 size 34nm, specific surface area 1400m 2 / g

[0109] · Other pigments (c-1) Product Name: TIPAQUE CR-95, manufactured by Ishihara Sangyo Co., Ltd., Titanium Oxide

[0110] · Pigment dispersant (D-1) Product Name: DISPERBYK-2013, manufactured by BYK, Styrene-Maleic Anhydride Copolymer, Acid Value 8mgKOH / g, Amine Value 18mgKOH / g (D-2) Product Name: SOLSPERSE5000S, manufactured by Lubrizol, Phthalocyanine Derivative

[0111] · Isocyanurate compound (E-1) Product Name: Desmodur N3300, manufactured by Sumika Covestro Urethane Co., Ltd., HDI Trimer, Number Average Molecular Weight 550

[0112] For the main agents prepared in the examples and comparative examples, the following evaluations were carried out. The evaluation results are shown in Table 1.

[0113] (1) TI value of the main agent Using a cone plate type viscometer (product name: DHR-3, manufactured by TA Instruments), at a temperature of 60 °C, the viscosities LSV and HSV of the main agent at shear rates of 1 sec -1 and 100 sec -1 were measured. The TI value was calculated from the following formula. TI value = LSV / HSV

[0114] (2) Pigment dispersibility of the main agent The main agent was heated to 80°C and pre-stirred with a homodisper. Subsequently, using the same amount of glass beads as the main agent, it was dispersed for 1 hour with a paint shaker. Thereafter, the diameter of the dispersed particles contained in the main agent was measured in accordance with JIS K 5600-2-5 using a grind gauge. The measured particle diameter was evaluated according to the following criteria. If it is C evaluation or above, it can be evaluated that the pigment dispersibility is good.

[0115] (Evaluation Criteria) A: Pre-stirring possible, and dispersion particle size 15 μm or less B: Pre-stirring possible, and dispersion particle size more than 15 μm and 50 μm or less C: Pre-stirring possible, and dispersion particle size more than 50 μm -: Due to exceeding the torque of the homodisper, pre-stirring was not possible and particle size measurement was also not possible

[0116] (3) Coating workability A curing agent was added to the main agent. After adding the curing agent, it was mixed for 15 seconds and a sample was taken out. The time when the sample was taken out was regarded as the start of the coating work. The taken-out sample was stirred with a spatula, and the time when the sample reached a state where it did not fall from the spatula was regarded as 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. If it is B evaluation or above, it can be evaluated that it is 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 completely cured during mixing

[0118] A two-component coating composition was prepared from the main agent and the curing agent prepared in the examples and comparative examples, and in-mold coating was performed on the object to be coated by the following method. The following evaluation was performed on the obtained primer coating film. 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 object to be coated (GFRP substrate) was placed in one of the molds. Subsequently, the molds were closed, and a two-component coating composition was injected between the pair of molds. The molds were heated to 100 °C and maintained for 5 minutes while being pressurized at 3 MPa. As a result, a cured primer coating film (film thickness: 200 μm) was formed on the object to be coated.

[0120] (4) Appearance The appearance of the primer coating film was visually evaluated according to the following criteria. If the evaluation is B or higher, it can be evaluated that the appearance is good.

[0121] (Evaluation Criteria) A: None of the generation of granular substances, entrapment of bubbles, and generation of cavities (holes where air easily accumulates) are observed. B: Slight entrapment of bubbles is observed. C: One or more of the generation of granular substances, entrapment of bubbles, and generation of cavities (holes where air easily accumulates) are clearly observed. D: One or more of the generation of granular substances, entrapment of bubbles, and generation of cavities (holes where air easily accumulates) are clearly observed, and the coating composition has cured without wetting and spreading, or the coating composition has leaked and the surface of the object to be coated is exposed. -: In-mold coating cannot be performed.

[0122] (5) Conductivity The surface resistance value of the primer coating film was measured using a surface resistance meter (76634-00, manufactured by Ransburg) and evaluated according to the following criteria. If the evaluation is C or higher, it can be evaluated that there is conductivity. A: Less than 1×10 7 Ω / □ B: 1×10 7 Ω / □ or more and less than 1×10 9 Ω / □ C: 1×10 9 Ω / □ or more and less than 1×10 10 Ω / □ D: 1×10 10 Ω / □ or more -: In-mold coating cannot be performed.

[0123] (6) Adhesion For the primer coating film, the cutting edge of an NT cutter S type (manufactured by NT Co., Ltd.) was held at approximately 30° with respect to the coating film surface, and cuts reaching the object to be coated (11 vertical, 11 horizontal, 2 mm interval) were made to create 100 meshes. An adhesive tape (manufactured by Nichiban Co., Ltd., Cellotape (registered trademark), 24 mm width) was uniformly pressed with fingertips so as not to leave air bubbles to cover all the meshes. The adhesive tape was immediately peeled while being pulled so that the angle formed with the coating film was approximately 90°. After tape peeling, the number of meshes in which the coating film remained was counted and evaluated according to the following criteria. The more meshes in which the coating film remains, the better the adhesion. It can be evaluated that there is adhesion with a B evaluation or higher.

[0124] (Evaluation Criteria) A: The number of meshes is 91 or more B: The number of meshes is 50 or more and 90 or less C: The number of meshes is 20 or more and 49 or less D: The number of meshes is 19 or less -: In-mold coating cannot be performed

[0125]

Table 1

[0126] All of the two-component coating compositions of the examples had good coating workability. The coating films formed by in-mold coating using these coating compositions were excellent in 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 is outside the scope of the present disclosure. In this example, the viscosity of the main agent was very high and the pigment dispersibility was low. Therefore, in-mold coating could not be performed. Comparative Example 2 is an example in which the hydroxyl value of the polyol (A) contained in the coating composition is outside the scope of the present disclosure. In this example, in-mold coating was possible, but the coating film was inferior in adhesion. Comparative Example 3 is an example in which the content of the curing catalyst (B) is more than the range of the present disclosure. In this example, the viscosity of the coating composition became extremely high immediately after mixing the main agent and the curing agent, and in-mold coating could not be carried out. Comparative Example 4 is an example in which the content of the solvent contained in the coating composition is high. In this example, the pigment dispersibility and coating workability of the two-component coating composition were good. On the other hand, the coating film was inferior in all of appearance, conductivity, and adhesion.

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

[0128] Subsequently, a main agent (trade name: R-2810-603-1, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) and a curing agent (R-271 hardener, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) were mixed at a mass ratio of 100 / 40 to prepare a two-component urethane-curable clear paint composition. This clear paint composition was electrostatically applied onto the uncured base coating film to a dry film thickness of 25 μm. Then, it was left standing for 10 minutes and baked at 90 °C for 45 minutes to obtain a multilayer coating film composed of a primer coating film, a base coating film, and a clear coating film.

[0129] The obtained multilayer coating film had a good appearance. From this, it is considered that the primer coating film had good conductivity.

[0130] The present disclosure includes the following aspects. [1] A two-component coating composition containing a main agent and a curing agent, The main agent contains a polyol (A), a curing catalyst (B), a conductive pigment (C), and a pigment dispersant (D), The hardener contains 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 with respect to 100 parts by mass of the solid content of the polyol (A). The conductive pigment (C) has a DBP oil absorption of 490 cm 3 / 100 g or less. A two-component coating composition for in-mold coating, wherein the content of the solvent contained in the two-component coating composition is 30% by mass or less. [2] The polyol (A) in the two-component coating composition according to [1] above contains a first polyester polyol (A) having three or more hydroxyl groups and a branched structure. [3] In the two-component coating composition according to [2] above, the proportion of the first polyester polyol (A) in the total content of the polyol (A) is 35% by mass or more. [4] The main agent has a low shear viscosity LSV (mPa·s) measured under the conditions of 60 °C and a shear rate of 1.0 sec -1 divided by the high shear viscosity HSV (mPa·s) measured under the conditions of 60 °C and a shear rate of 100 sec -1 to obtain a TI value (LSV / HSV) of 2.0 or more and 200 or less in the two-component coating composition according to any one of [1] to [3] above. [5] In the two-component coating composition according to any one of [1] to [4] above, the content of the conductive pigment (C) is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the polyol (A). [6] The polyol (A) in the two-component coating composition according to [1] above contains at least one selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol. [7] A two-component coating composition according to any one of the above [1] to [6], which is for forming a primer coating film. [8] Using a molding machine equipped with a pair of molds, after applying a two-component coating composition according to any one of the above [1] to [7] to an object to be coated disposed on one of the molds, curing the two-component coating composition inside the closed pair of molds to form a primer coating film; After taking out the object to be coated from the molding machine, coating a base paint composition on the primer coating film to form an uncured base coating film; Coating a clear paint composition on the uncured base coating film to form an uncured clear coating film; A method for forming a multilayer coating film, comprising curing the uncured base coating film and the uncured clear coating film.

Industrial Applicability

[0131] The two-component coating composition of the present invention can be suitably used for in-mold coating.

Claims

1. A two-component coating composition comprising a main agent and a curing agent, wherein the main agent contains a polyol (A), a curing catalyst (B), a conductive pigment (C) and a pigment dispersant (D), the curing agent contains 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 with respect to 100 parts by mass of the solid content of the polyol (A), The conductive pigment (C) has an oil absorption of 490 cm ３ / 100 g or less, A two-component coating composition for in-mold coating, wherein the content of the solvent contained in the two-component coating composition is 30% by mass or less.

2. The two-component coating composition according to claim 1, wherein the polyol (A) contains a first polyester polyol (A) 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 (A) in the total content of the polyol (A) is 35% by mass or more.

4. The main agent has a low-shear viscosity LSV (mPa·s) measured under the conditions of a shear rate of 1.0 sec at 60°C, divided by a high-shear viscosity HSV (mPa·s) measured under the conditions of a shear rate of 100 sec at 60°C, and the TI value (LSV / HSV) obtained is 2.0 or more and 200 or less. The two-component coating composition according to claim 1 or 2. －１ The two-component coating composition according to claim 1 or 2, wherein the TI value (LSV / HSV) obtained by dividing the low-shear viscosity LSV (mPa·s) measured under the condition of a shear rate of 1.0 sec at 60°C by the high-shear viscosity HSV (mPa·s) measured under the condition of a shear rate of 100 sec at 60°C is 2.0 or more and 200 or less. －１ The two-component coating composition according to claim 1 or 2, wherein the TI value (LSV / HSV) obtained by dividing the low-shear viscosity LSV (mPa·s) measured under the condition of a shear rate of 1.0 sec at 60°C by the high-shear viscosity HSV (mPa·s) measured under the condition of a shear rate of 100 sec at 60°C is 2.0 or more and 200 or less.

5. The two-component coating composition according to claim 1 or 2, wherein the content of the conductive pigment (C) is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the polyol (A).

6. The two-component coating composition according to claim 1, wherein the polyol (A) contains at least one selected from the group consisting of a polyester polyol, a polyether polyol and a polycarbonate polyol.

7. The two-component coating composition according to claim 1 or 2, which is for forming a primer coating film.

8. After applying the two-component coating composition according to claim 1 to an object to be coated disposed on one of a pair of molds using a molding machine equipped with the pair of molds, curing the two-component coating composition inside the closed pair of molds to form a primer coating film; After taking out the object to be coated from the molding machine, coating a base paint composition on the primer coating film to form an uncured base coating film; Coating a clear paint composition on the uncured base coating film to form an uncured clear coating film; A method for forming a multilayer coating film, comprising curing the uncured base coating film and the uncured clear coating film.

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