Coating composition for rotary atomization-type electrostatic coating device, coating film, and vehicle

Abstract

The present invention addresses the problem of providing a coating composition for a rotary atomization-type electrostatic coating device, wherein it is possible to suppress uneven paint spreading and improve coating efficiency. This coating composition for a rotary atomization-type electrostatic coating device is characterized in that the rotary atomization-type electrostatic coating device does not use shaping air to atomize the coating composition and the coating composition has an electrical resistance value of 0.02-1.5 MΩ.

Description

Coating composition for rotary atomizer electrostatic coating device, coating film and vehicle

[0001] The present invention relates to a coating composition for a rotary atomizer electrostatic coating device, a coating film, and a vehicle.

[0002] Conventionally, coating equipment has been known that atomizes (also called atomization) paint by spraying shaping air onto the paint released from a bell cup. However, this type of coating equipment has the drawback of reducing coating efficiency because the accompanying flow of the shaping air is reflected by the workpiece, causing the atomized paint to fly up.

[0003] In response to this, a rotary atomization electrostatic coating device that does not use shaping air has been proposed (see, for example, Patent Document 1). The coating device in Patent Document 1 is configured to release paint filaments from grooves in a rotary head, which are then electrostatically atomized. The electrostatically atomized paint then adheres to a grounded workpiece (an electrical conductor) by electrostatic force, and is then coated.

[0004] JP 2019-055345 A

[0005] However, Patent Document 1 focuses only on the diameter of the paint filaments, and does not pay attention to the properties and composition of the paint itself.

[0006] Furthermore, the inventors' investigations revealed that when paints used in conventional coating devices using shaping air are applied using the rotary atomization electrostatic coating device of Patent Document 1, some of the electrostatically atomized paint discharged from the rotary head does not adhere to the object being coated, but instead adheres to the outer periphery of the rotary head, which is not the object being coated, resulting in reduced coating efficiency. In this case, the paint that had adhered to the outer periphery of the rotary head may fly off and adhere to the object being coated, damaging its appearance. Furthermore, when paint adheres to objects not to be coated (also known as "paint adhesion"), not only does this reduce coating efficiency, but it also results in unnecessary steps and costs, such as curing the objects not to be coated, removing paint that has adhered to them, and cleaning or replacing the objects not to be coated.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a coating composition for use in a rotary atomizer electrostatic coating device that can suppress coating adhesion and increase coating efficiency.

[0008] Another object of the present invention is to provide a coating film using such a coating composition.

[0009] Another object of the present invention is to provide a vehicle having such a coating.

[0010] The coating composition according to the present invention is a coating composition for a rotary atomizer electrostatic coating device, characterized in that the rotary atomizer does not use shaping air to atomize the coating composition, and the coating composition has an electrical resistance value of 0.02 to 1.5 MΩ, which makes it possible to suppress coating adhesion and increase coating efficiency.

[0011] In one embodiment of the coating composition according to the present invention, the coating composition contains one or more selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether, and blocked isocyanates in an amount of 0.5% by mass or more, based on the total mass of the coating composition.

[0012] In one embodiment of the coating composition according to the present invention, the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound is a blocked isocyanate, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more.

[0013] In one embodiment of the coating composition according to the present invention, the blocked isocyanate is a blocked isocyanate of 1,6-hexamethylene diisocyanate.

[0014] In one embodiment of the coating composition according to the present invention, the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound being one or more selected from the group consisting of methanol, ethanol, 1-propanol, and diethyl ether, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more.

[0015] In one embodiment of the coating composition according to the present invention, the electrical resistance value is 0.02 to 1.0 MΩ.

[0016] In one embodiment of the coating composition according to the present invention, the coating composition is a coating composition for forming a coating film on an outer panel of a vehicle.

[0017] In one embodiment of the coating composition according to the present invention, the coating composition is a coating composition for forming an intermediate coating film on a vehicle exterior panel.

[0018] The coating film according to the present invention is a coating film made using the coating composition for the rotary atomizer electrostatic coating device.

[0019] The vehicle according to the present invention is a vehicle having the above coating film.

[0020] According to the present invention, it is possible to provide a coating composition for a rotary atomizer electrostatic coating device that can suppress coating adhesion and increase coating efficiency. According to the present invention, it is possible to provide a coating film using such a coating composition. According to the present invention, it is possible to provide a vehicle having such a coating film.

[0021] Hereinafter, embodiments of the present invention will be described. These descriptions are for the purpose of illustrating the present invention and are not intended to limit the present invention in any way.

[0022] In the present invention, two or more embodiments can be combined in any manner.

[0023] As used herein, ranges of values ​​are intended to include the upper and lower limits of the range unless otherwise specified, for example, 0.02 to 1.5 MΩ means 0.02 MΩ or more and 1.5 MΩ or less.

[0024] In the present invention, the paint and the paint composition can be used interchangeably.

[0025] (Coating composition for rotary atomization type electrostatic coating device) The coating composition according to the present invention is a coating composition for a rotary atomization type electrostatic coating device, characterized in that the rotary atomization type electrostatic coating device does not use shaping air for atomizing the coating composition, and the electrical resistance value of the coating composition is 0.02 to 1.5 MΩ.

[0026] The inventors have conducted studies and found that in a rotary atomization electrostatic coating device that does not use shaping air to atomize a coating composition, by setting the electrical resistance value of the coating composition to 0.02 to 1.5 MΩ, it is possible to suppress coating adhesion and increase coating efficiency.

[0027] The electrical resistance of the coating composition of the present invention is 0.02 to 1.5 MΩ. If the electrical resistance is less than 0.02 MΩ, the droplets of the coating composition cannot be sufficiently charged. If the electrical resistance is more than 1.5 MΩ, the coating adhesion cannot be suppressed.

[0028] In one embodiment, the electrical resistance of the coating composition of the present invention is 0.02 MΩ or greater, 0.05 MΩ or greater, 0.1 MΩ or greater, 0.2 MΩ or greater, 0.3 MΩ or greater, 0.4 MΩ or greater, 0.5 MΩ or greater, 0.6 MΩ or greater, 0.7 MΩ or greater, 0.8 MΩ or greater, 0.9 MΩ or greater, 1.0 MΩ or greater, 1.1 MΩ or greater, 1.2 MΩ or greater, 1.3 MΩ or greater, or 1.4 MΩ or greater. In another embodiment, the electrical resistance of the coating composition of the present invention is 1.5 MΩ or less, 1.4 MΩ or less, 1.3 MΩ or less, 1.2 MΩ or less, 1.1 MΩ or less, 1.0 MΩ or less, 0.9 MΩ or less, 0.8 MΩ or less, 0.7 MΩ or less, 0.6 MΩ or less, 0.5 MΩ or less, 0.4 MΩ or less, 0.3 MΩ or less, 0.2 MΩ or less, 0.1 MΩ or less, or 0.05 MΩ or less.

[0029] In one embodiment of the coating composition according to the present invention, the electrical resistance is 0.02 to 1.0 MΩ. Further investigation by the present inventors revealed that, in the case of rotary atomizer electrostatic coating devices, such as those described in paragraph

[0038] of Patent Document 1, in which a voltage generator controls the voltage applied to the rotary head to maintain a constant current flowing between the rotary head and the workpiece (hereinafter sometimes referred to as a "voltage-controlled constant current type device"), if the electrical resistance of the coating composition is high, a high voltage is applied to the rotary atomizer electrostatic coating device to maintain a constant current, which can result in an abnormal shutdown of the coating device. An abnormal shutdown of the coating device results in unnecessary work or loss of raw materials, such as identifying the cause of the shutdown, eliminating the cause, discarding or recoating defective coated products due to uneven coating caused by the shutdown, and restarting the coating device, thereby reducing productivity. In contrast, by setting the electrical resistance of the coating composition to 0.02 to 1.0 MΩ, high voltage is prevented from being applied to the coating device, abnormal shutdown of the coating device is suppressed, and stable coating can be achieved.

[0030] The method for controlling the electrical resistance of the coating composition of the present invention to the range of 0.02 to 1.5 MΩ is not particularly limited, but examples include blending one or more selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether, and blocked isocyanates. Examples of blocked isocyanates include blocked isocyanates of 1,6-hexamethylene diisocyanate. Commercially available blocked isocyanates include those manufactured by Baxenden under the trade name "7961" and those manufactured by Asahi Kasei Corporation under the trade names "Duranate SBB-70P" and "Duranate MFK-60B."

[0031] The amount of one or more selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether, and blocked isocyanate is, for example, 0.5 mass% or more relative to the total mass of the coating composition. In one embodiment, the amount of one or more selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether, and blocked isocyanate is 0.5 to 10 mass% relative to the total mass of the coating composition.

[0032] In one embodiment of the coating composition according to the present invention, the coating composition contains one or more selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether, and blocked isocyanates in an amount of 0.5% by mass or more, based on the total mass of the coating composition.

[0033] Alternatively, the electrical resistance of the coating composition of the present invention can be controlled within the range of 0.02 to 1.5 MΩ by, for example, blending a compound having a certain dielectric constant.

[0034] In one embodiment of the coating composition according to the present invention, the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more, which makes it easier to control the electrical resistance of the coating composition within the range of 0.02 to 1.5 MΩ.

[0035] Examples of compounds having a dielectric constant of 3.0 F / m or more (hereinafter, may be simply referred to as "predetermined compounds") include alcohol-based solvents such as methanol: 33.1 F / m, ethanol: 23.8 F / m, 1-propanol: 22.1 F / m, isobutanol (2-methylpropanol): 18.9 F / m, diacetone alcohol: 18.2 F / m, n-butanol: 17.1 F / m, 2-butanol: 15.5 F / m, and benzyl alcohol: 13.1 F / m.

[0036] Other examples of the predetermined compound include diethyl ether (dielectric constant: 4.2 F / m) and blocked isocyanate.

[0037] In one embodiment of the coating composition according to the present invention, the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound is a blocked isocyanate, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more.

[0038] In one embodiment of the coating composition according to the present invention, the blocked isocyanate is a blocked isocyanate of 1,6-hexamethylene diisocyanate.

[0039] In one embodiment of the coating composition according to the present invention, the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound being one or more selected from the group consisting of methanol, ethanol, 1-propanol, and diethyl ether, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more.

[0040] In the coating composition according to the present invention, it is preferable that the predetermined compound is not an alcohol-based solvent, from the viewpoint of reducing VOCs derived from the coating composition.

[0041] In one embodiment of the coating composition according to the present invention, the predetermined compound is a blocked isocyanate.

[0042] The predetermined compounds may be used alone or in combination of two or more.

[0043] By setting the mass ratio of the predetermined compound to the total mass of the coating composition of the present invention to 0.5 mass% or more, it becomes easier to control the electrical resistance value of the coating composition of the present invention to a range of 0.02 to 1.5 MΩ. In one embodiment, the mass ratio of the predetermined compound to the total mass of the coating composition of the present invention is 0.5 to 10 mass%.

[0044] The coating composition of the present invention may contain other components such as resins, crosslinking agents, pigments, solvents (solvents other than the specified compounds), pigment dispersants, anti-sagging agents, viscosity modifiers, anti-settling agents, reaction accelerators, crosslinking accelerators, curing agents, leveling agents, surface conditioners, antifoaming agents, plasticizers, preservatives, anti-mold agents, UV stabilizers, etc. These optional components may be used alone or in combination of two or more.

[0045] Resin Component As the resin component, resin components of conventionally known coating compositions can be used. Examples of resin components include polyester resins, melamine resins, epoxy resins, acrylic resins, alkyd resins, fluororesins, polyurethane resins, polyether resins, and modified products thereof. Polymeric compounds containing or consisting of inorganic components, such as silicone resins and alkoxysilane condensates, can also be used as the resin component. The resin component may be used alone or in combination of two or more.

[0046] The content of the resin component is not particularly limited and may be adjusted appropriately.

[0047] The resin component preferably has a curable functional group that reacts with the crosslinking agent. Any functional group that reacts with the crosslinking agent may be used, such as a hydroxy group, a carboxy group, or an epoxy group. The curable functional group possessed by the resin component used in the coating composition of the present invention is preferably a hydroxy group, since it can react with a blocked isocyanate compound having a dielectric constant within a specific range.

[0048] Crosslinking Agent The crosslinking agent can be selected depending on the curable functional group of the resin component. Examples of the crosslinking agent include carbodiimide compounds, hydrazine compounds, amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, amine compounds, polyamide compounds, and polycarboxylic acid compounds. The crosslinking agent may be used alone or in combination of two or more.

[0049] The crosslinking agent used in the coating composition of the present invention is preferably a blocked isocyanate compound having a dielectric constant within a specific range. Such a blocked isocyanate compound may be used in combination with other crosslinking agents.

[0050] The isocyanate compound (1) may be an alicyclic, aromatic group-containing aliphatic, or aromatic compound. Suitable examples of the isocyanate compound include diisocyanates and their isocyanurates (trimers of diisocyanates).

[0051] As the diisocyanate, for example, a diisocyanate having 5 to 24, preferably 6 to 18, carbon atoms can be used.

[0052] For example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, undecane diisocyanate-(1,11), lysine ester diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (IPDI), 4,4'-diisocyanatodicyclodicyclomethane, ω,ω'-dipropyl ether diisocyanate, thiodipropyl diisocyanate, cyclohexyl-1,4-diisocyanate, isocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,5-dimethyl-2,4-bis(isocyanatomethyl)benzene, 1,5-trimethyl-2,4-bis(ω-isocyanatoethyl)-benzene, 1,3,5-trimethyl-2,4-bis(isocyanatomethyl)benzene, 1,3,5-triethyl-2,4-bis(isocyanatomethyl)benzene, dicyclohexyldimethylmethane-4,4'-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and diphenylmethane-4,4'-diisocyanate.

[0053] Also usable are aromatic diisocyanates such as 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanatodiphenylmethane, 1,4-diisocyanatoisopropylbenzene, cyclohexyl-1,4-diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate. Mixtures of these compounds can also be used.

[0054] The isocyanurate may be a trimer of the above-mentioned diisocyanate, and a mixture of diisocyanates and trimers may also be used.

[0055] Melamine Resin The melamine resin is not particularly limited and may be the same as or different from the melamine resin (ii) contained in the intermediate coating composition. Examples of melamine resins that can be used include methylated melamine resins, butylated melamine resins, and methyl-butyl mixed melamine resins. Examples include "Cymel-303" and "Cymel 254" manufactured by Nippon Cytec Co., Ltd., "U-Van 20N60" and "U-Van 128" manufactured by Mitsui Chemicals, Inc., and the "Sumimal Series" manufactured by Sumitomo Chemical Co., Ltd.

[0056] The amount of melamine resin used is preferably 10 to 40% by mass based on the solid content of the film-forming resin, such as urea-modified acrylic resin, urethane-modified polyester resin, or melamine resin. 15 to 35% by mass is even more preferable. If the amount of melamine resin used is 10% by mass or more, curability is enhanced. Furthermore, if the amount of melamine resin used is 40% by mass or less, chipping resistance is improved when the film is formed.

[0057] Pigments The pigment is not particularly limited, and known paint pigments can be used. Examples of pigments include color pigments such as titanium dioxide, carbon black, iron oxide red, and phthalocyanine blue; extender pigments such as precipitated barium sulfate, calcium carbonate, talc, mica, and kaolin; anti-rust pigments; and infrared reflective pigments. The pigments may be used alone or in combination of two or more.

[0058] The shape of the luster pigment is not particularly limited. The luster pigment may be colored. For example, a luster pigment having an average particle size (D50) of 2 to 50 μm and a scale-like shape with a thickness of 0.1 to 5 μm is preferred. Furthermore, luster pigments having an average particle size in the range of 10 to 35 μm are more preferably used because they have an excellent luster.

[0059] The pigment concentration (PWC) of the bright pigment in the coating composition is, for example, 1 to 23.0%. When the PWC of the bright pigment is 23% or less, the appearance of the coating film tends to be better. The PWC of the bright pigment is preferably 1.5% to 20.0%, and more preferably 2.0% to 18.0%. The pigment concentration (PWC) indicates the pigment content (%) based on the resin solids mass.

[0060] Examples of luster pigments include uncolored or colored metallic luster materials such as metals or alloys, and mixtures thereof, interference mica powder, colored mica powder, white mica powder, graphite, and colorless or colored flat pigments. Uncolored or colored metallic luster materials such as metals or alloys, and mixtures thereof, interference mica powder, colored mica powder, and white mica powder are preferred because they have excellent dispersibility and can form highly transparent coating films. Specific examples of metals include aluminum, aluminum oxide, copper, zinc, iron, nickel, and tin.

[0061] Furthermore, if necessary, a coloring pigment may be contained. Examples of the coloring pigment include the coloring pigments described in the description of the intermediate coating composition and inorganic pigments. Furthermore, calcium carbonate, barium sulfate, clay, talc, etc. may be used in combination as an extender pigment.

[0062] The total pigment concentration (PWC) in the metallic paint composition, including the luster pigment and all other pigments, is 1 to 50%, preferably 1.5% to 40%, and more preferably 2.0% to 30%. A total pigment concentration (PWC) of 50% or less tends to result in a better coating appearance.

[0063] Solvents The solvent can be appropriately selected from solvents used in conventional coating compositions. For example, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, diacetone alcohol, and benzyl alcohol; esters such as ethyl acetate, butyl acetate, isobutyl acetate, ethyl propionate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as diethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, dioxane, and tetrahydrofuran (THF); ethylene glycol, diethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, dioxane, and tetrahydrofuran (THF); Examples of the solvent include glycols such as ethylene glycol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, pentamethylene glycol, and 1,3-octylene glycol; amides such as formamide, N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO), and N-methylpyrrolidone (NMP); ketones such as acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, mesitylene, and dodecylbenzene; and halogenated solvents such as chloroform and dichloromethylene.

[0064] The coating composition of the present invention is, in one embodiment, a solvent-based coating.

[0065] The coating composition of the present invention may be used in any known coating application as long as it is used in a rotary atomization electrostatic coating device. Examples of applications of the coating composition of the present invention include primer coats, topcoat base coats, and topcoat clear coats for the outer panels of vehicles such as automobiles, motorcycles, trains, buses, trucks, and taxis; primer coats, topcoat base coats, and topcoat clear coats for vehicle parts; aircraft such as airplanes and helicopters; home appliances such as refrigerators, washing machines, and televisions; computer equipment such as personal computers and smartphones; building materials such as steel doors, steel sashes, steel shutters, storerooms, fences, stairs, guardrails, and doorknobs; hot water gas appliances such as meter boxes, ventilation fans, and water heaters; steel furniture such as lockers, cabinets, partitions, and racks; cast iron pipes such as valves; primer coats, topcoat base coats, and topcoat clear coats for the outer panels of cast metals such as conveyors, chain blocks, and manhole covers.

[0066] In one embodiment of the coating composition according to the present invention, the coating composition is a coating composition for forming a coating film on an outer panel of a vehicle.

[0067] In one embodiment of the coating composition according to the present invention, the coating composition is a coating composition for forming an intermediate coating film on a vehicle exterior panel.

[0068] The substrate to be coated with the coating composition is not particularly limited as long as it can be coated with a rotary atomizer-type electrostatic coating device, and can be appropriately selected. Examples of the substrate include metals such as steel plate, iron, aluminum, and copper; glass, plastic, and wood with a thin metal film or conductive thin film formed on the surface; and the like. The substrate may be subjected to a zinc plating treatment, a chemical conversion treatment, an electrodeposition treatment, etc.

[0069] The rotary atomization electrostatic coating device using the coating composition for rotary atomization electrostatic coating device of the present invention may be a known rotary atomization electrostatic coating device, such as the coating device described in Patent Document 1. The rotary atomization electrostatic coating device may be a voltage-controlled constant current type device, or a current-controlled constant voltage type device (a rotary atomization electrostatic coating device that controls the current applied to the rotary head to maintain a constant voltage flowing between the rotary head and the workpiece).

[0070] In one embodiment, the rotary atomizer electrostatic coating device using the coating composition for rotary atomizer electrostatic coating device of the present invention is a voltage-controlled constant current type device.

[0071] - Method for preparing coating composition The method for preparing the coating composition is not particularly limited except that the electrical resistance value of the coating composition is set to 0.02 to 1.5 MΩ, and the coating composition can be prepared by mixing the respective components by a conventionally known method.

[0072] (Coating Film) The coating film according to the present invention is a coating film made using the coating composition for the rotary atomizer electrostatic coating device.

[0073] The thickness of the coating film after drying is not particularly limited and may be adjusted as appropriate. For example, the thickness of the coating film after drying is 5 to 50 μm. In one embodiment, the thickness of the coating film after drying is 25 to 40 μm. In another embodiment, the thickness of the coating film after drying is 30 to 35 μm.

[0074] In one embodiment, the coating of the present invention is an intermediate coat for the exterior of a vehicle. In another embodiment, the coating of the present invention is a topcoat base coat for the exterior of a vehicle. In another embodiment, the coating of the present invention is a topcoat clear coat for the exterior of a vehicle. In another embodiment, the coating of the present invention is an intermediate coat for the exterior of an automobile. In another embodiment, the coating of the present invention is a topcoat base coat for the exterior of an automobile. In another embodiment, the coating of the present invention is a topcoat clear coat for the exterior of an automobile.

[0075] - Method for producing coating film The method for producing the coating film is not particularly limited, except that the coating composition for a rotary atomization type electrostatic coating device of the present invention is used to apply the coating using a rotary atomization type electrostatic coating device. For example, a conventional coating method such as forming a multi-layer coating film or baking can be used.

[0076] The drying temperature after application of the coating composition for a rotary atomizer electrostatic coating device of the present invention may be adjusted appropriately depending on the solvent, coating environment, etc. For example, in the case of a drying time of 20 to 30 minutes, the drying temperature is 140 to 150°C.

[0077] Examples of articles having the coating film of the present invention include, but are not limited to, vehicles such as automobiles, motorcycles, trains, buses, trucks, and taxis; vehicle parts; aircraft such as airplanes and helicopters; home appliances such as refrigerators, washing machines, and televisions; computer equipment such as personal computers and smartphones; construction materials such as steel doors, steel sashes, steel shutters, storerooms, fences, stairs, guardrails, and doorknobs; hot water and gas appliances such as meter boxes, ventilation fans, and water heaters; steel furniture such as lockers, cabinets, partitions, and racks; cast iron pipes such as valves; and castings such as conveyors, chain blocks, and manhole covers.

[0078] The coating film on the article of the present invention may consist solely of one or more coating films of the present invention, or the coating film on the article may consist of one or more coating films of the present invention and one or more coating films made using known coating compositions.

[0079] (Vehicle) The vehicle according to the present invention is a vehicle having the above coating film. The vehicle is not particularly limited and can be appropriately selected from known vehicles. Examples of the vehicle include automobiles, motorcycles, trains, buses, trucks, taxis, truck cranes, trailers, garbage trucks, tanks, and other specialized vehicles.

[0080] The coating film on the vehicle of the present invention may consist solely of one or more coating films of the present invention, while the coating film on the article may consist of one or more coating films of the present invention as well as one or more coating films made from known paint compositions.

[0081] The present invention will be described in more detail below by way of examples, but these examples are intended to illustrate the present invention and are not intended to limit the present invention in any way.

[0082] The materials used in the examples are as follows: Prescribed compound 1: blocked isocyanate, trade name "7961" manufactured by Baxenden, indicated as "7961" in Table 1 Prescribed compound 2: blocked isocyanate, trade name "Duranate MFK-60B" manufactured by Asahi Kasei Corporation, indicated as "MFK-60B" in Table 1 Prescribed compound 3: ethanol Prescribed compound 4: diethyl ether

[0083] Production Example 1: Production of urethane-modified polyester resin for intermediate coating composition

[0047] A 2L reaction vessel equipped with a nitrogen inlet tube, a stirrer, a temperature controller, a cooling tube equipped with a dropping funnel, and a decanter was charged with 440 parts by mass of isophthalic acid, 20 parts by mass of hexahydrophthalic acid, 40 parts by mass of azelaic acid, 300 parts by mass of trimethylolpropane, and 200 parts by mass of neopentyl glycol. Once the raw materials were dissolved by heating and became stirrable, 0.2 parts by mass of dibutyltin oxide was added, stirring was started, and the reaction temperature was gradually increased from 180 to 220°C over 3 hours. The resulting condensation water was distilled out of the system. When the temperature reached 220°C, the temperature was maintained for 1 hour, and 20 parts by mass of xylene was gradually added to the reaction vessel, allowing the condensation reaction to proceed in the presence of the solvent. When the resin acid value reached 10 mgKOH / g, the mixture was cooled to 100°C, and 100 parts by mass of hexamethylene diisocyanate was gradually added over 30 minutes. After further holding for 1 hour, 200 parts by mass of xylene and 200 parts by mass of butyl acetate were added to obtain a urethane-modified polyester resin with a solid content of 70%, a number average molecular weight of 2000, an acid value of 8 mgKOH / g (solid content), a hydroxyl value of 120 (solid content), and a resin Tg of 60°C.

[0084] Production Example 2: Preparation of non-aqueous dispersion for intermediate coating composition (a) Preparation of dispersion-stable resin 90 parts by mass of butyl acetate was charged into a vessel equipped with a stirrer, temperature control device, and reflux condenser. Next, 20 parts by mass of a solution consisting of 38.9 parts by mass of methyl methacrylate, 38.8 parts by mass of stearyl methacrylate, 22.3 parts by mass of 2-hydroxyethyl acrylate, and 5.0 parts by mass of azobisisobutyronitrile was added, and the mixture was heated with stirring to increase the temperature. The remaining 85 parts by mass of the above mixed solution was added dropwise at 110°C over 3 hours, and then a solution consisting of 0.5 parts by mass of azobisisobutyronitrile and 10 parts by mass of butyl acetate was added dropwise over 30 minutes. The reaction solution was stirred and refluxed for an additional 2 hours to increase the conversion rate to resin, and then the reaction was terminated to obtain an acrylic resin with a solids content of 50% and a number average molecular weight of 5,600.

[0085] (b) Preparation of non-aqueous dispersion 90 parts by mass of butyl acetate and 120 parts by mass of the acrylic resin obtained in (a) Preparation of Dispersion Stabilizing Resin (60 parts by mass as solids) were added to a vessel equipped with a stirrer, cooler, and temperature controller. Next, a solution consisting of 7.0 parts by mass of styrene, 1.8 parts by mass of methacrylic acid, 12.0 parts by mass of methyl methacrylate, 8.5 parts by mass of ethyl acrylate, 40.7 parts by mass of 2-hydroxyethyl acrylate, and 1.4 parts by mass of azobisisobutyronitrile was added dropwise at 100 ° C. over 3 hours, and then a solution consisting of 0.1 parts by mass of azobisisobutyronitrile and 1 part by mass of butyl acetate was added dropwise over 30 minutes. Stirring of the reaction solution was continued for another 1 hour, resulting in an emulsion with a solids content of 60% and a particle size of 180 nm. This emulsion was diluted with butyl acetate to obtain a core-shell butyl acetate dispersion having a viscosity of 300 cps (25°C), a particle size of 180 nm, a non-aqueous dispersion content of 40% by mass, and a Tg of 23°C and a hydroxyl value of 162 (solid content).

[0086] Preparation Example 3: Preparation of Intermediate Coating Composition 1

[0049] A 1 L vessel was charged with 107 parts by mass of the urethane-modified polyester resin varnish for intermediate coating compositions obtained in the previous Preparation Example, 280 parts by mass of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha), 13 parts by mass of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Corporation), 7 parts by mass of LMS-100 (flaky talc manufactured by Fuji Talc Co., Ltd.), 47 parts by mass of butyl acetate, and 47 parts by mass of xylene. An equal amount of GB503M (glass beads with a particle size of 1.6 mm) was then added, and the mixture was dispersed at room temperature for 3 hours using a benchtop sand grinder mill to produce a gray pigment paste. The particle size measured at the end of dispersion using a grind gauge was 5 μm or less. The glass beads were filtered to obtain a pigment paste.

[0087] To 100 parts by mass of the pigment paste, 130 parts by mass of the urethane-modified polyester resin for intermediate coating compositions, 53 parts by mass of the non-aqueous dispersion for intermediate coating compositions, 71 parts by mass of U-VAN 128 (a melamine resin manufactured by Mitsui Chemicals, Inc., solids content 60%), 0.5 parts by mass of blocked isocyanate "7961" (manufactured by Baxenden), and 6.7 parts by mass of blocked isocyanate "Duranate MFK-60B" (manufactured by Asahi Kasei Corporation, solids content **%) were mixed.

[0088] The mixture was then diluted with a 1 / 1 mixed solvent of ethoxyethyl propionate and S-100 (an aromatic hydrocarbon solvent manufactured by Exxon Chemical Company) using a No. 4 Ford cup to a dilution rate of 19 seconds at 20°C to prepare intermediate coating composition 1. The nonvolatile content at the time of application was 49%.

[0089] (Production Examples 4 to 11: Production of Intermediate Coating Compositions 2 to 9) Intermediate coating compositions 2 to 9 were prepared in the same manner as in Production Example 3, except that the blending amounts of the two blocked isocyanates and the blending amount of ethanol or diethyl ether in intermediate coating composition 1 were changed as shown in Table 1.

[0090] (Production Example 12: Production of comparative intermediate coating composition) A comparative intermediate coating composition was prepared in the same manner as in Production Example 3, except that the blending amounts of the two blocked isocyanates in intermediate coating composition 1 were changed as shown in Table 1.

[0091] (Production Example 13: Production of urethane-modified polyester resin for base coating composition) 334 parts by mass of isophthalic acid, 311 parts by mass of hexahydrophthalic acid, 57 parts by mass of ethylene glycol, 105 parts by mass of trimethylolpropane, and 289 parts by mass of neopentyl glycol were charged into a 2 L reaction vessel equipped with a nitrogen inlet tube, a stirrer, a temperature controller, a cooling tube equipped with a dropping funnel, and a decanter. When the raw materials were dissolved by heating and became stirrable, 0.2 parts by mass of dibutyltin oxide was added, stirring was started, and the reaction temperature was gradually raised from 180 to 220 ° C. over 3 hours. The condensation water produced was distilled out of the system. When the temperature reached 220 ° C., the temperature was maintained for 1 hour, and 20 parts by mass of xylene was gradually added to the reaction vessel, and the condensation reaction was allowed to proceed in the presence of a solvent. When the resin acid value reached 8 mgKOH / g, the mixture was cooled to 100°C, and 10 parts by mass of hexamethylene diisocyanate was gradually added over 30 minutes. After further holding for 1 hour, 344 parts by mass of xylene, 43 parts by mass of butyl acetate, and 43 parts by mass of n-butanol were added to obtain a urethane-modified polyester resin with a solids content of 70%, a number-average molecular weight of 1,800, a weight-average molecular weight of 10,000, an acid value of 6 mgKOH / g (solids content), and a hydroxyl value of 100 (solids content).

[0092] (Production Example 14: Production of acrylic resin for base coating composition) A 1 L reaction vessel fitted with a cooling tube equipped with a nitrogen inlet tube, a stirrer, a temperature regulator, a dropping funnel and a decanter was charged with 50 parts by mass of xylene and 14 parts by mass of n-butanol, and the temperature was set to 110 ° C. Next, a solution containing 5 parts by mass of styrene, 35.3 parts by mass of ethyl acrylate, 41.1 parts by mass of butyl methacrylate, 15.5 parts by mass of hydroxyethyl acrylate, 3.1 parts by mass of methacrylic acid and 4.0 parts by mass of t-butylperoxy-2-ethylhexanoate was added dropwise over 3 hours. Next, a solution consisting of 1.0 part by mass of t-butylperoxy-2-ethylhexanoate and 6 parts by mass of xylene was added dropwise over 30 minutes, and then the mixture was maintained at 110 ° C. for an additional 1 hour. An acrylic resin having a solid content of 60%, an acid value of 20 mg KOH / g (solid content), a hydroxyl value of 75 (solid content) and a number average molecular weight of 5,000 was obtained.

[0093] (Production Example 15: Production of Solvent-Based Metallic Base Coating Composition) A stainless steel container was charged with 75 parts by mass of AS-9606 (urea-modified acrylic resin manufactured by Mitsubishi Rayon Co., Ltd., urea modification amount 6.5%, acid value 12 mg KOH / g (solid content), hydroxyl value 70 (solid content), weight average molecular weight 7000, Tg 16°C), 14.3 parts by mass of the urethane-modified polyester for the base coating composition of Production Example 13, 25 parts by mass of the acrylic resin for the base coating composition of Production Example 14, and 2.9 parts by mass of Cyanine Blue G-314 (a blue pigment manufactured by Sanyo Dye Co., Ltd.) and Varifine. 33.9 parts by mass of a pigment dispersion paste obtained by dispersing 6.0 parts by mass of BF-40 (barium sulfate pigment manufactured by Sakai Chemical Industry Co., Ltd.) so that the particle size of each pigment was 5 μm or less, 50 parts by mass of U-BAN 20N60 (butylated melamine resin manufactured by Mitsui Chemicals, Inc., solids content 60%), and 11.6 parts by mass of Aluminum Paste 7640NS (aluminum pigment manufactured by Toyo Aluminum K.K.) were weighed and stirred with a tabletop stirrer to prepare a pale blue solvent-borne metallic base coating composition (PWC 17.0%).

[0094] Next, the solvent-based metallic base paint composition was diluted with a dilution thinner consisting of 10 parts by mass of Solvesso 150 (a hydrocarbon solvent manufactured by Exxon Oil Company), 40 parts by mass of ethyl acetate, 40 parts by mass of toluene, and 10 parts by mass of butyl acetate to a dilution of 12.5 seconds / 20°C using a No. 4 Ford cup to prepare base paint composition 1.

[0095] (Production Example 16: Synthesis of acid anhydride group-containing acrylic resin (component (A)) A reaction vessel equipped with a thermometer, a stirrer, a condenser, a nitrogen inlet tube, and a dropping funnel was charged with 46.5 parts by mass of propylene glycol monomethyl ether acetate and 51.8 parts by mass of Solvesso 100 (an aromatic hydrocarbon solvent manufactured by Esso Corporation), and the temperature was raised to 130°C. Using a dropping funnel, 16.4 parts by mass of styrene monomer, 18.86 parts by mass of n-butyl acrylate, 7.7 parts by mass of isobornyl acrylate, 22.53 parts by mass of cyclohexyl methacrylate, 13.94 parts by mass of 2-ethylhexyl acrylate, 18 parts by mass of maleic anhydride, and 2. To the resulting mixture, 57 parts by mass of t-butylperoxy 2-ethylhexanoate and a solution consisting of 8.5 parts by mass of t-butylperoxy 2-ethylhexanoate and 5.2 parts by mass of Solvesso 100 were added dropwise over 3 hours. After completion of the dropwise addition, the mixture was maintained at 130°C for 30 minutes, and then a solution consisting of 1 part by mass of t-butylperoxy 2-ethylhexanoate and 2.2 parts by mass of Solvesso 100 was added dropwise over 30 minutes. After completion of the dropwise addition, the reaction was continued at 130°C for an additional 1 hour, yielding a varnish with a non-volatile content of 58% that contained an acid anhydride group-containing acrylic resin having a number average molecular weight of 3,100 and 1.84 mmol / g (solids content) of acid anhydride groups.

[0096] (Production Example 17: Synthesis of Carboxyl Group-Containing Polyester Resin (Component (A)) A reaction vessel equipped with a thermometer, a stirrer, a condenser, and a nitrogen inlet tube was charged with 8.85 parts by mass of pentaerythritol, 57.5 parts by mass of PLACCEL M (ε-caprolactone monomer, trade name, manufactured by Daicel Corporation), 33.92 parts by mass of RIKACID HH-A (hexahydrophthalic anhydride, trade name, manufactured by New Japan Chemical Co., Ltd.), and 0.1 parts by mass of dibutyltin oxide, and the mixture was heated to 150°C. After maintaining the temperature at 150°C for 2 hours, 616 parts by mass of hexahydrophthalic anhydride dissolved by heating was added, and the mixture was maintained at 150°C for 1 hour, cooled, and diluted with 33.4 parts by mass of 3-ethoxyethyl propionate to obtain a varnish with a number average molecular weight of 2500, a weight average molecular weight / number average molecular weight = 1.3, a carboxyl group content of 2.2 mmol / g (solids content), and a hydroxyl group content of 0.32 mmol / g (solids content), and a non-volatile content of 75% containing the carboxyl group-containing polyester resin.

[0097] Production Example 18: Synthesis of acrylic resin containing hydroxyl groups and epoxy groups (component (c)) An autoclave equipped with a thermometer, a stirrer, a condenser, a nitrogen inlet tube, and a dropping funnel was charged with 23.7 parts by mass of 3-ethoxyethyl propionate, and the temperature was raised to 170°C. Using a liquid transfer pump, 25 parts by mass of styrene, 30.3 parts by mass of glycidyl methacrylate, 8 parts by mass of n-butyl acrylate, 23.9 parts by mass of isobornyl acrylate, 12.8 parts by mass of 4-hydroxybutyl acrylate, and a solution consisting of 3.0 parts by mass of di-tert-amyl peroxide and 2.6 parts by mass of 3-ethoxyethyl propionate were added dropwise to the reaction vessel over 3 hours.

[0098] After the dropwise addition was completed, the mixture was maintained at 170°C for 30 minutes, and then a solution consisting of 0.4 parts by mass of di-tert-butyl peroxide and 1.5 parts by mass of 3-ethoxyethyl propionate was added dropwise over 30 minutes using a liquid pump. After the dropwise addition was completed, the reaction was continued for another hour at 170°C, yielding a varnish with a non-volatile content of 76% that contained an acrylic resin having a number average molecular weight of 2,200, epoxy groups of 2.1 mmol / g (solid content), and hydroxyl groups of 0.9 mmol / g (solid content).

[0099] (Production Example 19: Preparation of clear coating composition 1) 32 g of the resin solids of the prepared acid anhydride group-containing acrylic resin (component (A)), 15 g of the resin solids of the prepared carboxyl group-containing polyester resin (component (B)), and 0.5 parts by mass of a tetrabutylammonium bromide curing catalyst were mixed in a stainless steel beaker to form a first package.

[0100] Separately, 53 g of the prepared acrylic resin (component (c)) as resin solids was mixed with 2 parts by weight of the ultraviolet absorber "Tinuvin 900" manufactured by Ciba Specialty Corporation, 1 part by weight of the light stabilizer "Sanol LS-440" manufactured by Sankyo Machinery Co., Ltd., and 0.1 parts by weight of the surface conditioner "Modaflow" manufactured by UCB Corporation to prepare a second package. If stored in this two-component state, there will be no reaction under room temperature conditions. The first and second packages obtained above were mixed immediately before use, and the viscosity was adjusted to 28 seconds using a Ford Cup No. 4 with a mixed solvent consisting of butyl acetate / xylene = 1 / 1 to prepare clear coating composition 1.

[0101] (Examples 1 to 9 and Comparative Example 1) The electrical resistance and viscosity of the resulting coating compositions were measured and the deposition ability onto the rotary head was evaluated as follows. The results are shown in Table 1.

[0102] Electrical Resistance Value The electrical resistance value was measured using a product called "Megaohm Tester" manufactured by Ransberg.

[0103] Viscosity: The viscosity of the coating composition was measured at a temperature of 23°C using a Ford Cup No. 4.

[0104] - Coating composition adhesion to the outer periphery of the rotary head A cationic electrodeposition coating composition "V-50" (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was electrodeposited onto a 0.8 mm thick, 30 cm long, 40 cm wide dull steel plate that had been subjected to a zinc phosphate conversion treatment, to a cured film thickness of approximately 20 μm, and after heating and curing at 160°C for 30 minutes, intermediate coating compositions 1 to 9 or a comparative intermediate coating composition, base coating composition 1, or clear coating composition 1 was applied using a rotary atomizer electrostatic coating device to a cured film thickness of approximately 25 μm. The outer periphery of the rotary head after painting was visually inspected and evaluated according to the following criteria. Criteria A, B, and C are acceptable. A: No adhesion of the coating composition to the outer periphery of the rotary head was observed. B: Very slight adhesion of the coating composition to the outer periphery of the rotary head was observed. C: A small amount of adhesion of the coating composition to the outer periphery of the rotary head was observed. D: Significant adhesion of the coating composition to the outer periphery of the rotary head was observed.

[0105]

[0106] According to the present invention, it is possible to provide a coating composition for a rotary atomizer electrostatic coating device that can suppress coating adhesion and increase coating efficiency. According to the present invention, it is possible to provide a coating film using such a coating composition. According to the present invention, it is possible to provide a vehicle having such a coating film.

Claims

1. A coating composition for a rotary atomizer type electrostatic coating device, characterized in that the rotary atomizer type electrostatic coating device does not use shaping air for atomizing the coating composition, and the coating composition has an electrical resistance value of 0.02 to 1.5 MΩ.

2. A coating composition for use in a rotary atomizer electrostatic coating device as described in claim 1, wherein the coating composition contains at least one selected from the group consisting of methanol, ethanol, 1-propanol, diethyl ether and blocked isocyanate in an amount of at least 0.5 mass% based on the total mass of the coating composition.

3. A coating composition for a rotary atomizer type electrostatic coating device as described in claim 1, wherein the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound is a blocked isocyanate, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass% or more.

4. The coating composition for use in a rotary atomizer electrostatic sprayer according to claim 3, wherein said blocked isocyanate is a blocked isocyanate of 1,6-hexamethylene diisocyanate.

5. A coating composition for a rotary atomizer type electrostatic coating device as described in claim 1, wherein the coating composition contains a compound having a dielectric constant of 3.0 F / m or more, the compound being one or more selected from the group consisting of methanol, ethanol, 1-propanol and diethyl ether, and the mass ratio of the compound to the total mass of the coating composition is 0.5 mass % or more.

6. The coating composition for use in a rotary atomizer electrostatic coating device according to claim 1, wherein said electrical resistance value is 0.02 to 1.0 MΩ.

7. The coating composition for use in a rotary atomizer type electrostatic coating device according to claim 1, wherein the coating composition is for forming a coating film on an exterior panel of a vehicle.

8. The coating composition for use in a rotary atomizer type electrostatic coating device according to claim 1, wherein the coating composition is a coating composition for forming an undercoat coating film on an exterior panel of a vehicle.

9. A coating film formed using the coating composition for a rotary atomizer type electrostatic coating device according to claim 1.

10. A vehicle having the coating film according to claim 9.

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