Multilayer coating film

Abstract

To provide a multilayer coating film having a glitter texture and capable of achieving both the hiding property and the chroma of the coating film.SOLUTION: A multilayer coating film of the present disclosure comprises an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, wherein a lightness L * at 45 degrees of the intermediate coating layer is 80 or more, wherein a visible light transmittance of the first base layer is 5 to 30%, wherein a visible light transmittance of the second base layer is 60% or more, and wherein the second base layer comprises a luster pigment.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a multilayer coating film.

Background Art

[0002] On the surface of an object to be coated such as an automobile body, a plurality of coating films (multilayer coating film) having various roles are sequentially formed to protect the object to be coated and at the same time impart a beautiful appearance and excellent design. As a method for forming such a multilayer coating film, a method of forming an undercoat film such as an electrodeposition coating film on an object to be coated having excellent conductivity, and then sequentially forming an intermediate coat film and a topcoat film thereon as necessary is common. Among these coating films, it is the topcoat film including the base coat film that particularly greatly affects the appearance and design of the coating film. Especially in automobiles, the appearance and design of the topcoat film formed on the vehicle body are extremely important.

[0003] The base coat film can be roughly classified into a coating film that does not contain flaky pigments, so-called solid color, and a coating film that contains flaky pigments and has a luster, so-called metallic color. As a typical example of the flaky pigment contained in the coating film having a luster, a flaky aluminum pigment can be mentioned. By including a flaky aluminum pigment in the base coat film, a metallic luster (metallic feeling) can be expressed.

[0004] The appearance of the coating film formed on an automobile is greatly related to the appearance value such as the high-class feeling of the automobile. In addition, customers (consumers) who purchase automobiles tend to seek automobiles having a coating film with excellent design. Due to such diversification of consumer preferences and the trend towards uniqueness, more unique designs are being demanded.

[0005] Patent Document 1 describes a coating film structure in which a coating film made of a color base coat paint containing a coloring pigment on a substrate, a coating film made of a metallic base paint having a lightness difference of 30 or less, a hue difference of 50 or less, and a chroma difference of 30 or less from the coating film made of the color base coat paint, and a coating film made of a top clear paint are laminated.

[0006] Patent Document 2 has a color base layer formed on a substrate and a mica base layer formed on the color base layer. The hiding film thickness of the mica base layer is larger than the coating film thickness of the mica base layer and within 10 times the coating film thickness. The color base layer has a laminated coating with a lightness that is 10 to 30 lower as the L value than the lightness of the mica base layer.

[0007] Patent Document 3 describes a method for forming a multilayer coating film. After coating and heat-curing a cationic electrodeposition paint, a first colored paint having hiding properties for the base, which is a thermosetting type in an organic solvent type or non-aqueous dispersion type and contains a neutralized product of a polyvalent carboxylic acid resin having an acid value of 5 to 100 and an amino resin as essential components, a thermosetting aqueous second colored paint, and a thermosetting aqueous transparent paint are coated, then heated to simultaneously cure the three-layer coating film, and then a thermosetting transparent paint is coated and heat-cured.

[0008] Patent Document 4 describes a method for forming a glossy multilayer coating film having a red to yellow hue on a substrate to be coated. The method includes a step of coating a color base paint on the substrate to be coated to form a color base coating film, a step of coating a glossy paint on the color base coating film to form a glossy coating film, and a step of coating a top clear paint on the glossy coating film to form a top clear coating film. It is also described that the interference color in the highlight portion of the glossy coating film and the color of the color base coating film are the same color system within the range of Munsell hue of 10RP to 10Y.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, when the chroma of the coating film is increased, the hiding power decreases. Conversely, when the hiding power of the coating film is increased, the chroma decreases. In the multilayer coating films described in Patent Documents 1 to 4 known in the art, in a coating film having a glossiness, there are cases where the hiding power and the chroma of the coating film cannot be sufficiently compatible.

[0011] An object of the present disclosure is to provide a multilayer coating film having a glossiness and capable of achieving both the hiding power and the chroma of the coating film.

Means for Solving the Problems

[0012] The present disclosure provides the following aspects. [1] Comprising an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, The 45-degree apparent brightness L* of the intermediate coating layer is 80 or more, The transmittance of the first base layer in the visible light region is 5% or more and 30% or less, The transmittance of the second base layer in the visible light region is 60% or more, The second base layer contains a bright pigment, Multilayer coating film. [2] The absolute value of the difference between the hue h1 of the first base layer and the hue h2 of the multilayer coating film is 20 or less. The multilayer coating film according to [1]. [3] The chroma C1 of the first base layer is 60 or more. The multilayer coating film according to [1] or [2]. [4] The chroma C2 of the multilayer coating film is 60 or more. The multilayer coating film according to any one of [1] to [3]. [5] The glossiness Si15 value of the multilayer coating film is 15 or more. The multilayer coating film according to any one of [1] to [4]. [6] The first base layer contains a coloring pigment, The content of the coloring pigment is 5 parts by mass or more and 60 parts by mass or less in 100 parts by mass of the total solid content of the first base layer, and the multi-layer coating film according to any one of [1] to [5]. [7] The second base layer contains a coloring pigment, The content of the coloring pigment is 2 parts by mass or less in 100 parts by mass of the total solid content of the second base layer, and the multi-layer coating film according to any one of [1] to [6]. [8] The content of the black pigment in the second base coating film is 0 part by mass or more and 0.1 part by mass or less in 100 parts by mass of the total solid content of the second base layer, and the multi-layer coating film according to any one of [1] to [7]. [9] The content of the mica-based pigment in the second base coating film is 0.1 part by mass or more and 15 parts by mass or less in 100 parts by mass of the total solid content of the second base layer, and the multi-layer coating film according to any one of [1] to [8].

[10] The multi-layer coating film according to any one of [1] to [9] further includes a first clear layer between the first base layer and the second base layer.

[11] The multi-layer coating film according to any one of [1] to

[10] further includes a second clear layer laminated on the second base layer.

Effect of the Invention

[0013] The present disclosure provides a multi-layer coating film having a brilliance and capable of achieving both the hiding property and the chroma of the coating film.

Embodiment for Carrying out the Invention

[0014] The multi-layer coating film of the present disclosure includes an intermediate coating layer, a first base layer laminated on the intermediate coating layer, and a second base layer laminated on the first base layer, The 45-degree visual lightness L* of the intermediate coating layer is 80 or more, The transmittance of the first base layer in the visible light region is 5% or more and 30% or less, The transmittance of the second base layer in the visible light region is 60% or more, The second base layer contains a fluorescent pigment.

[0015] The multilayer coating film of the present disclosure has a brilliant feeling and can achieve both the hiding property and the chroma of the coating film. Although the present disclosure should not be construed as being limited to a specific theory, the reason why the multilayer coating film of the present disclosure can exhibit such an effect is considered as follows. That is, in the multilayer coating film of the present disclosure, since the lightness of the intermediate coating layer is 80 or more, the influence of the undercoat layer on the appearance can be suppressed to a certain extent. Then, by stacking a first base layer having permeability and a second base layer having higher permeability than the first base layer and containing a fluorescent pigment on such an intermediate coating layer, as a whole multilayer coating film, the hiding property of the coating film is good, and moreover, it is considered that a multilayer coating film having chroma and a brilliant feeling can be obtained.

[0016] In the present disclosure, the "intermediate coating film" can be a layer disposed below the first base layer, that is, on the substrate side.

[0017] In one aspect, the multilayer coating film of the present disclosure can be used for automotive applications. In such an aspect, the multilayer coating film of the present disclosure can be disposed on an undercoat layer, and the undercoat layer may be disposed on a substrate.

[0018] The substrate may be any one having at least a substrate layer such as a metal layer, a plastic layer, or a foam layer.

[0019] Examples of the metal forming the metal layer include iron, copper, aluminum, tin, zinc, and alloys thereof. The metal layer may be in a plate shape or a molded product. Specific examples of the molded product include automotive bodies and parts such as passenger cars, trucks, motorcycles, and buses.

[0020] The above metal layer (preferably the base layer side of the metal layer) may be previously subjected to chemical conversion treatment with a phosphate, a zirconium salt, a chromate, etc., and then an electrodeposited coating layer may be formed as an undercoat layer. Examples of the electrodeposition coating composition that can be used for forming the electrodeposited coating layer include a cationic electrodeposition coating composition and an anionic electrodeposition coating composition.

[0021] Examples of the resin for forming the above plastic layer include a polypropylene resin, a polycarbonate resin, a urethane resin, a polyester resin, a polystyrene resin, an ABS resin, a vinyl chloride resin, and a polyamide resin. The plastic layer may be in a plate shape or a molded article. Examples of the molded article include automotive parts such as a spoiler, a bumper, a mirror cover, a grille, and a door knob. A primer layer may be provided as an undercoat layer on the plastic layer (preferably the base layer side of the plastic layer).

[0022] (Multi-layer coating film) The multi-layer coating film of the present disclosure includes an intermediate coat layer, a first base layer laminated on the intermediate coat layer, and a second base layer laminated on the first base layer. The multi-layer coating film of the present disclosure may further include a first clear coat between the first base layer and the second base layer. Further, the multi-layer coating film of the present disclosure may further include a second clear coat layer laminated on the second base layer.

[0023] (Intermediate coat layer) The intermediate coat layer can typically be a layer provided on the undercoat layer. The intermediate coat layer can, for example, protect the undercoat layer and impart chipping resistance to the multi-layer coating film, but is not limited thereto.

[0024] The 45-degree specular gloss L* of the above intermediate coat layer is 80 or more, and preferably can be 80 or more and 100 or less. When the 45-degree specular gloss L* of the intermediate coat layer is in such a range, the brilliance and hiding power of the resulting multi-layer coating film can be improved.

[0025] In the present disclosure, the 45-degree brightness L* can be measured in accordance with JIS Z 8723.

[0026] The above intermediate coating film is formed from an intermediate coating composition containing an intermediate coating film-forming resin, a coloring pigment, a extender pigment, etc. As the above coating film-forming resin, a compound exemplified by the coating film-forming resin (A) used in the first or second base coating composition described later can be used. As the coating film-forming resin used in the above intermediate coating composition, a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate is preferably used from the viewpoints of various performances of the intermediate coating film and the like.

[0027] Examples of the coloring pigment contained in the above intermediate coating composition include pigments having no chroma such as carbon black and titanium dioxide, and pigments having chroma for complementing the hue of the base layer. When the above intermediate coating composition contains a pigment, the content of the pigment is preferably 0.1 part by mass or more and preferably 50 parts by mass or less with respect to 100 parts by mass of the resin solid content.

[0028] In a preferred embodiment, the content of a white coloring pigment such as titanium dioxide is preferably 20 parts by mass or more, more preferably 25 parts by mass or more with respect to 100 parts by mass of the resin solid content, and the content of a black coloring pigment such as carbon black is preferably 0.1 part by mass or less, more preferably 0.05 part by mass or less with respect to 100 parts by mass of the resin solid content, and the content of other colored coloring pigments is preferably 0.2 part by mass or less, more preferably 0.1 part by mass or less with respect to 100 parts by mass of the resin solid content. By the content range of the pigment being within such a range, it may be easy to make the brightness of the intermediate coating layer within a desired range.

[0029] The thickness of the above intermediate coating film is preferably, for example, 3 to 50 μm, and more preferably 5 to 30 μm.

[0030] (First base layer) The first base layer is laminated on the primer layer. The first base layer may be laminated in direct contact with the primer layer, or may be laminated on the primer layer via another layer provided on the primer layer. The first base layer can, for example, impart color to a multilayer coating film, but is not limited thereto.

[0031] The transmittance of the first base layer in the visible light region is 5% or more and 30% or less, and preferably can be 9% or more and 20% or less.

[0032] In the present disclosure, the transmittance in the visible light region means the transmittance with respect to light having a wavelength of 400 nm or more and 700 nm or less. Such transmittance in the visible light region can be measured in accordance with JIS R 32124.

[0033] The first base layer preferably contains a coloring pigment. Examples of such coloring pigments include azo chelate pigments, azomethine azo pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, monoazo pigments, indanthrone pigments, disazo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, quinophthalone pigments, isoindolinone pigments, naphthol pigments, pyrazolone pigments, ansanthrone pigments, anthraquinone pigments, anthrapyrimidine pigments, metal complex pigments and other organic coloring pigments; lead yellow, iron oxide, yellow iron oxide, transparent iron oxide, iron black, iron chromium, bismuth manganese, bismuth vanadate, chromium oxide, molybdate orange, red iron oxide, titanium yellow, zinc white, zinc yellow, ocher, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine blue, cobalt blue, phthalocyanine blue, cobalt violet and other inorganic coloring pigments; graphite pigments, other colored and colored flat pigments, etc.

[0034] The coloring pigment may be a chromatic color or an achromatic color, and may be a color such as red, blue, yellow, green, purple, brown, white, black, gray, etc.

[0035] In the above first base layer, the content of the coloring pigment is preferably 5 parts by mass or more and 60 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the total solid content of the first base layer. When the content of the coloring pigment in the first base layer is within such a range, good color stability during film thickness variation can be achieved. In the present disclosure, the solid content means the heat residue defined in JIS K 5601-1-2:2008, and is calculated by measuring the percentage of the mass of the residue after heating at 105°C for 60 minutes with respect to the original mass.

[0036] The thickness of the first base layer is, for example, 3 μm or more, preferably 5 μm or more, and for example, 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.

[0037] The above first base layer can be formed using a first base paint composition. The first base paint composition contains a film-forming resin (A1) and a curing agent (B1). In one aspect, the above first base paint composition further contains a coloring pigment (C1), and in another aspect, the above first base paint composition does not contain a coloring pigment (C1).

[0038] (Film-forming resin (A1)) The above film-forming resin (A) is a resin capable of forming a coating film by reacting with a curing agent (B1) described later, and preferably contains one or more selected from an acrylic resin, a polyol resin, a polyester resin, a polyurethane resin, an epoxy resin, a fluororesin, and a silicone resin, and more preferably contains one or more selected from an acrylic resin, a polyol resin, and a polyester resin. The above film-forming resin (A1) preferably has a hydroxyl group.

[0039] The above coating film-forming resin (A1) preferably contains an aqueous resin. An aqueous resin is a resin dispersed in an aqueous medium and may be an emulsion or a dispersion. Examples of such an aqueous resin include an acrylic resin aqueous dispersion, a polyester resin aqueous dispersion, a polyurethane resin aqueous dispersion, and an epoxy resin aqueous dispersion.

[0040] The above coating film-forming resin (A1) preferably contains an acrylic resin, and more preferably contains an acrylic resin aqueous dispersion. The acrylic resin aqueous dispersion may be either an acrylic resin emulsion or an acrylic resin dispersion, and is preferably an acrylic resin emulsion. The acrylic resin contained in the acrylic resin aqueous dispersion may be in the form of particles in an aqueous medium.

[0041] Typically, the above acrylic resin is obtained as a polymer of a monomer mixture containing a (meth)acrylic monomer, and the acrylic resin aqueous dispersion is obtained by emulsion polymerization of the above monomer mixture. The above monomer mixture preferably contains a hydroxyl group-containing monomer, and may further contain an acid group-containing monomer and other monomers. In one aspect, the above monomer mixture preferably contains an alkyl (meth)acrylate, a hydroxyl group-containing monomer, and an acid group-containing monomer, and more preferably contains an alkyl (meth)acrylate, a hydroxyl group-containing monomer, an acid group-containing monomer, and a styrene-based monomer. In the present disclosure, (meth)acrylic acid represents acrylic acid and methacrylic acid.

[0042] The above alkyl (meth)acrylate is an alkyl (meth)acrylate having no acid group and no hydroxyl group. By the above monomer mixture containing an alkyl (meth)acrylate, the main skeleton of the acrylic resin can be favorably formed.

[0043] Examples of the above (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and the like. Only one kind of (meth)acrylic acid alkyl ester may be used, or two or more kinds may be used in combination.

[0044] Examples of the hydroxyl group-containing monomer include (meth)acrylic monomers having a hydroxyl group. Specifically, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate; ε-caprolactone-modified (meth)acrylic monomers, and the like can be mentioned.

[0045] As the ε-caprolactone-modified (meth)acrylic monomer, commercially available products may be used. Examples of such commercially available products include Placcel FA-1, Placcel FA-2, Placcel FA-3, Placcel FA-4, Placcel FA-5, Placcel FM-1, Placcel FM-2, Placcel FM-3, Placcel FM-4, and Placcel FM-5 (all manufactured by Daicel Chemical Industries, Ltd.). Only one kind of hydroxyl group-containing monomer may be used, or two or more kinds may be used in combination.

[0046] By including the hydroxyl group-containing monomer in the above monomer mixture, hydrophilicity is imparted to the resulting acrylic resin, and the curing reactivity between the acrylic resin and a curing agent (B) described later can be enhanced.

[0047] The acid group-containing monomer may be a (meth)acrylic monomer having an acid group, and such an acid group may be a carboxyl group, a sulfonic acid group, or a phosphoric acid group. From the viewpoint of improving dispersion stability and promoting the curing reaction, it is preferably a carboxyl group. By including the acid group-containing monomer in the monomer mixture, various stabilities such as the storage stability, mechanical stability, and stability against freezing of the resulting acrylic resin can be improved, and the curing reaction between the acrylic resin and the curing agent (B) during film formation can be promoted.

[0048] Examples of the acid group-containing monomer include carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid; sulfonic acid group-containing monomers such as p-vinylbenzenesulfonic acid, p-acrylamidopropanesulfonic acid, and t-butylacrylamidosulfonic acid; and phosphoric acid group-containing monomers such as the monophosphate ester of 2-hydroxyethyl (meth)acrylate and the monophosphate ester of 2-hydroxypropyl (meth)acrylate. Only one kind of acid group-containing monomer may be used, or two or more kinds may be used in combination.

[0049] Examples of the other monomers include at least one monomer selected from the group consisting of styrene-based monomers, (meth)acrylonitrile, and (meth)acrylamide. Examples of the styrene-based monomer include styrene and α-methylstyrene. Only one kind of the other monomer may be used, or two or more kinds may be used in combination.

[0050] The monomer mixture may further contain crosslinkable monomers such as carbonyl group-containing monomers, hydrolyzable silyl group-containing monomers, and various polyfunctional vinyl monomers. By including the crosslinkable monomer in the monomer mixture, self-crosslinkability can be imparted to the resulting acrylic resin. Only one kind of crosslinkable monomer may be used, or two or more kinds may be used in combination.

[0051] Examples of the carbonyl group-containing monomer include monomers containing a keto group such as acrolein, diacetone (meth)acrylamide, acetacetooxyethyl (meth)acrylate, formylstyrene, and alkyl vinyl ketones having 4 to 7 carbon atoms (e.g., methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone).

[0052] Examples of the hydrolyzable silyl group-containing monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, and the like.

[0053] The polyfunctional vinyl monomer is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule. Specific examples of the polyfunctional vinyl monomer include polyfunctional vinyl compounds such as divinylbenzene, ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, allyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexane di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate; polyfunctional monomers such as triallyl cyanurate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and the like.

[0054] Only one kind of the crosslinkable monomer may be used, or two or more kinds may be used in combination. Preferred crosslinkable monomers include, for example, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, and divinylbenzene. By using these crosslinkable monomers, there is an advantage that the average particle diameter of the acrylic resin contained in the obtained acrylic resin aqueous dispersion can be suitably controlled to 100 nm or less.

[0055] The amount of the crosslinkable monomer is preferably 0.2 to 20% by mass, more preferably 0.5 to 20% by mass, based on the total amount of the monomer mixture. By including the crosslinkable monomer in the above range in the monomer mixture, there is an advantage that the average particle diameter of the acrylic resin contained in the prepared acrylic resin aqueous dispersion can be suitably controlled to 100 nm or less.

[0056] In the film-forming resin (A1), the acrylic resin contained in the acrylic resin aqueous dispersion may be in the form of particles, and the average particle diameter of such particles is preferably 0.01 μm or more and 1.0 μm or less. In the present disclosure, the average particle diameter is the volume average particle diameter determined by the dynamic light scattering method, and specifically, it can be measured using an electrophoretic light scattering photometer ELSZ series (manufactured by Otsuka Electronics Co., Ltd.) or the like.

[0057] In the film-forming resin (A1), the acrylic resin contained in the acrylic resin aqueous dispersion may be core-shell type particles.

[0058] In the film-forming resin (A1), the acid value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 1 mgKOH / g or more and 80 mgKOH / g or less, more preferably 2 mgKOH / g or more and 70 mgKOH / g or less, still more preferably 3 mgKOH / g or more and 60 mgKOH / g or less.

[0059] In the film-forming resin (A1), the hydroxyl value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good. In the present disclosure, both the acid value and the hydroxyl value are values in terms of solid content and are measured by a method in accordance with JIS K 0070.

[0060] In the film-forming resin (A1), the weight-average molecular weight of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 50,000 or more and 5,000,000 or less, more preferably 50,000 or more and 1,000,000 or less. When it is within the above range, various properties such as the hardness, adhesion, and water resistance of the resulting coating film can be improved. In the present disclosure, the weight-average molecular weight is a value obtained by converting the measurement result of gel permeation chromatography (GPC) using polystyrene as a standard.

[0061] In the solid content of the above film-forming resin (A1), the content of the solid content of the acrylic resin aqueous dispersion is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 85% by mass or less, still more preferably 50% by mass or more and 80% by mass or less. When it is within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the resulting coating film is improved.

[0062] The acrylic resin aqueous dispersion can be produced by heating and emulsifying polymerization of the above monomer mixture in an aqueous medium in the presence of a radical polymerization initiator and an emulsifier with stirring. The reaction temperature may be, for example, about 30 to 100°C. The reaction time can be appropriately selected according to the reaction scale and reaction temperature, and may be, for example, about 1 to 10 hours. In the emulsion polymerization, for example, the monomer mixture or the monomer pre-emulsion may be added all at once or dropped gradually into a reaction vessel charged with water and an emulsifier. By appropriately selecting such procedures, the reaction temperature can be adjusted. The above monomer pre-emulsion can be prepared by emulsifying the monomer mixture and at least a part of water and an emulsifier.

[0063] As the radical polymerization initiator, a known initiator used in the emulsion polymerization of acrylic resins can be used. The radical polymerization initiator is preferably a water-soluble radical polymerization initiator. For example, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate can be used in an aqueous solution state. In addition, a so-called redox initiator in which an oxidizing agent such as potassium persulfate, sodium persulfate, ammonium persulfate, or hydrogen peroxide is combined with a reducing agent such as sodium bisulfite, sodium thiosulfate, Rongalit, or ascorbic acid can also be used in an aqueous solution state. Only one kind of radical polymerization initiator may be used, or two or more kinds may be used in combination.

[0064] As the emulsifier, for example, an anionic or nonionic emulsifier selected from micelle compounds having a hydrocarbon group with 6 or more carbon atoms and a hydrophilic moiety such as a carboxylate, sulfonate, or sulfate partial ester in the same molecule can be used. Examples of anionic emulsifiers include alkali metal salts or ammonium salts of sulfuric acid half-esters of alkylphenols or higher alcohols; alkali metal salts or ammonium salts of alkyl or allyl sulfonates; alkali metal salts or ammonium salts of sulfuric acid half-esters of polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, or polyoxyethylene allyl ethers. Examples of nonionic emulsifiers include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, or polyoxyethylene allyl ethers. Further, as other examples of emulsifiers, various anionic and nonionic reactive emulsifiers having groups such as (meth)acrylic, propenyl, allyl, allyl ether, and maleic acid groups having a radically polymerizable unsaturated double bond in the molecule can be mentioned.

[0065] Commercially available products may be used as the emulsifier. Examples of commercially available products include, for example, Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Chemical Industries, Ltd.), Adeka Resope SR-10 (manufactured by ADEKA Corporation), Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the like. Only one type of emulsifier may be used, or two or more types may be used in combination.

[0066] In emulsion polymerization, auxiliaries (chain transfer agents) for molecular weight adjustment such as mercaptan compounds and lower alcohols can be used as necessary. By using these auxiliaries, emulsion polymerization can proceed favorably, and smooth and uniform formation of the coating film can be promoted to improve the adhesion of the coating film to the object to be coated.

[0067] As emulsion polymerization, any polymerization method such as a one-stage continuous monomer dropping method, a core-shell polymerization method which is a multi-stage monomer feeding method, and a power feed polymerization method in which the monomer composition fed during polymerization is continuously changed can be appropriately selected.

[0068] A neutralizing agent may be added to the obtained acrylic resin aqueous dispersion to neutralize at least a part of the acid groups that may be contained in the acrylic resin. By neutralization, the stability of the acrylic resin aqueous dispersion can be improved. Examples of the neutralizing agent include basic compounds. Examples of the basic compounds include ammonia; organic amines such as monomethylamine, dimethylamine, trimethylamine, triethylamine, diisopropylamine, monoethanolamine, diethanolamine, and dimethylethanolamine (dimethylaminoethanol); and inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. Only one type of neutralizing agent may be used, or two or more types may be used in combination.

[0069] The above polyol resin is a resin having two or more hydroxyl groups in the molecule, and examples thereof include polyether polyol and polycarbonate polyol. As the above polyol resin, polyether polyol such as polypropylene glycol is preferable.

[0070] In the above first base paint composition, the content of the solid content of the above polyol resin is preferably 1 part by mass or more and 70 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, still more preferably 10 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass in total of the solid content of the above acrylic resin aqueous dispersion.

[0071] The polyester resin aqueous dispersion can be prepared, for example, by condensing a polyhydric alcohol component and a polybasic acid component and dispersing them in water with a basic compound. The polyurethane resin aqueous dispersion can be prepared, for example, by polymerizing a polyol compound, a compound having an active hydrogen group and a hydrophilic group in the molecule, and an organic polyisocyanate, if necessary, using a chain extender and a polymerization terminator, and dispersing the obtained polymer in water.

[0072] In the above first base paint composition, the content of the solid content of the above polyester resin aqueous dispersion is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, still more preferably 30 parts by mass or more and 70 parts by mass or less, based on 100 parts by mass in total of the solid content of the above acrylic resin aqueous dispersion.

[0073] The hydroxyl value of the film-forming resin (A1) is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0074] The content ratio of the solid content of the above film-forming resin (A1) is preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 85% by mass or less, still more preferably 20% by mass or more and 80% by mass or less in 100% by mass of the solid content of the aqueous first base paint composition.

[0075] (Hardener (B1)) The above curing agent (B1) can be a compound having two or more groups capable of reacting with the film-forming resin (A1) in one molecule, and together with the film-forming resin (A1), it corresponds to a film-forming component. As the above curing agent (B1), one or more selected from amino resins (melamine resins, urea resins, benzoguanamine resins, etc.), blocked isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds, and metal ions can be used.

[0076] In one aspect, it is preferable that the above curing agent (B1) contains an amino resin, and more preferably contains a melamine resin. By containing the melamine resin, a coating film can be formed by the self-polymerization of the melamine resin and the reaction between the amino group contained in the melamine resin and the hydroxyl group that may be contained in the film-forming resin (A1).

[0077] The melamine resin is obtained by modifying a condensate of an amino compound such as melamine and an aldehyde compound such as formaldehyde or acetaldehyde with a lower alcohol such as methanol, ethanol, propanol, or butanol. The melamine resin is preferably a compound having three reactive functional groups represented by the following formula or its polycondensate as reactive functional groups in one molecule of the triazine nucleus. -NX 1 X 2 [X 1 、X 2 each independently represents a hydrogen atom, a methylol group, or -CH2-OR 1 . R 1 represents an alkyl group having 1 to 8 carbon atoms, preferably a linear or branched alkyl group having 1 to 8 carbon atoms. When a plurality of -CH2-OR 1 are contained in the same molecule, the plurality of R 1 may be the same or different.

[0078] As the melamine resin, -N(CH2OR as a reactive functional group 1)Fully alkyl type containing only 2; methylol group type containing -N(CH2OR 1 )(CH2OH) as a reactive functional group; imino group type containing -N(CH2OR 1 )(H) as a reactive functional group; four types of methylol / imino group types containing -N(CH2OR 1 )(CH2OH) and -N(CH2OR 1 )(H), or containing -N(CH2OH)(H) can be exemplified. In the above fully alkyl type, methylol group type, imino group type or methylol / imino group type melamine resin, R 1 is preferably an alkyl group having 1 to 4 carbon atoms, preferably a methyl group, n-butyl group or isobutyl group. In one aspect, a mixture of a methyl group and a butyl group may be present, in another aspect, only a methyl group may be present, and in yet another aspect, only a butyl group may be present.

[0079] Commercially available products may be used as the melamine resin. Examples of commercially available products include methylol / imino type methyl / butyl mixed etherified melamine resins such as Cymel 202; imino type methyl / butyl mixed etherified melamine resins such as Cymel 204, Cymel 211, Cymel 250, Cymel 254, Mycote 212, Mycote 518, Mycote 525; fully alkyl type methylated melamine resins such as Cymel 350; imino group type methylated melamine resins such as Cymel 325, Cymel 327, Cymel 385, Cymel 701, Cymel 712, Mycote 723, Mycote 776; imino group type butylated melamine resins such as Mycote 508, methylol group type methylated melamine resins such as Cymel 370, methylol group type methyl / isobutyl mixed etherified melamine resins such as Mycote 2677 (the above are manufactured by Ornex Japan Co., Ltd.), etc.

[0080] The content of the solid content of the above melamine resin may be 0% by mass in 100% by mass of the total solid content of the above curing agent (B1), preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and still more preferably 95% by mass or more and 100% by mass or less.

[0081] The content of the melamine resin may be 0 parts by mass in 100 parts by mass in total of the solid content of the coating film-forming resin (A1) and the solid content of the curing agent (B1), preferably 10 parts by mass or more and 90 parts by mass or less, and more preferably 20 parts by mass or more and 80 parts by mass or less. As a result, there is an advantage that various physical properties such as the hardness, adhesion, and water resistance of the obtained coating film become good.

[0082] The blocked isocyanate compound can be prepared by adding a blocking agent having active hydrogen to a polyisocyanate composed of trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, etc. Such a blocked isocyanate resin dissociates the blocking agent by heating to generate an isocyanate group, which reacts with a functional group in the resin component to cure.

[0083] The content rate of the solid content of the curing agent (B1) in the aqueous first base coating composition is preferably 20% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less in 100% by mass in total of the solid content of the coating film-forming resin (A1) and the solid content of the curing agent (B1).

[0084] (Colored pigment (C1)) The above coloring pigments are not particularly limited. For example, azo chelate pigments, azomethine azo pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, monoazo pigments, indanthrone pigments, disazo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, quinophthalone pigments, isoindolinone pigments, naphthol pigments, pyrazolone pigments, ansanthrone pigments, anthraquinone pigments, anthrapyrimidine pigments, metal complex pigments and other organic coloring pigments; lead yellow, iron oxide, yellow iron oxide, transparent iron oxide, iron black, iron chromium, bismuth manganese, bismuth vanadate, chromium oxide, molybdate orange, red iron oxide, titanium yellow, zinc white, zinc yellow, ocher, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine, cobalt blue, phthalocyanine blue, cobalt violet and other inorganic coloring pigments; graphite pigments, other colored and tinted flat pigments, etc. The above coloring pigments may be chromatic or achromatic, and may be colors such as red, blue, yellow, green, purple, brown, white, black, gray, etc.

[0085] As the above coloring pigment (C1), from the viewpoints of improving weather resistance and ensuring hiding power, it is preferably a coloring pigment. In particular, titanium dioxide is more preferable because it has excellent coloring hiding power and is inexpensive. Also, as a pigment, a standard gray paint composition mainly composed of carbon black and titanium dioxide may be used. In addition, a paint composition having the same lightness or hue as the second base paint composition and a paint composition combining various coloring pigments may also be used. The first base paint composition of the present disclosure can act as a primer when applying the second base paint composition, and when it contains a coloring pigment, it can also act as a color base.

[0086] In the first base paint composition, the pigment mass concentration of the above pigment (PWC, the ratio of the mass of the pigment to the total solid content of the first base paint composition) is preferably 5% by mass or more and 60% by mass or less. By setting the PWC to 5% by mass, it becomes easier to enhance the hiding power. By setting the PWC to 60% by mass or less, it becomes easier to suppress the increase in viscosity during curing, so it becomes easier to ensure the fluidity and obtain a good coating film appearance.

[0087] (Luminous pigment) The first base paint composition may further contain a luminous pigment. In one aspect, the first base paint composition contains a luminous pigment, and in another aspect, the first base paint composition does not contain a luminous pigment.

[0088] Examples of the luminous pigment include metallic luminous pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys thereof; mica pigments such as interference mica pigments and white mica pigments; graphite pigments; glass flake pigments, and the like.

[0089] The average particle diameter of the above luminous pigment may preferably be 1 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less. The average thickness of the above luminous pigment may preferably be 0.01 μm or more and 6 μm or less, more preferably 0.1 μm or more and 5 μm or less.

[0090] In the present disclosure, the average particle diameter of the luminous pigment means the average major axis. The measurement of the average particle diameter can be performed by observing the luminous pigment using a shape analysis laser microscope (for example, VK-X 250 manufactured by Keyence Corporation, etc.) and obtaining the number average value of the maximum length (major axis) of 100 arbitrarily selected pigments.

[0091] Also, in the present disclosure, the average thickness t of the above luminous pigment can be calculated by the following formula based on the water surface spreading area (WCA: m 2 / g) per 1 g of the luminous pigment. t (μm) = 0.4 / [WCA (m 2 / g)] In the present disclosure, the water surface spreading area can be measured in accordance with JIS K 5906.

[0092] The water surface spreading area (WCA) of the above-described luminous pigment is preferably 0.06 m 2 / g or more and 40 m 2 / g or less, more preferably 0.08 m 2 / g or more and 4 m 2 / g or less. When the water surface spreading area of the luminous pigment is within the above range, a coating film with a highly particulate appearance can be obtained.

[0093] When the above-described luminous pigment is an aluminum pigment, surface treatment may be performed as necessary. Examples of surface treatments that can be applied to aluminum pigments include surface treatments using metal oxide-based compounds, surface treatments using phosphorus compounds, surface treatments using amine compounds, surface treatments using silane compounds, and the like.

[0094] Examples of the above-described metal oxide-based compounds include metal oxides containing at least transition metal elements as constituent metals, alkali metal salts thereof, and ammonium salts thereof. Specifically, molybdenum trioxide, molybdic acid, alkali metal molybdates, ammonium molybdates, vanadic acid, alkali metal vanadates, ammonium vanadates, and the like can be mentioned. The alkali metal is not particularly limited, and examples thereof include sodium and potassium. Among them, as the above-described metal oxide-based compound, it is preferable to use one or more metal oxide-based compounds selected from the group consisting of molybdic acid, alkali metal molybdates, ammonium molybdates, vanadic acid, alkali metal vanadates, and ammonium vanadates.

[0095] Examples of the above-described phosphorus compounds include organic phosphates, organic phosphites, organic phosphonic acids, and amine salts of these compounds. These phosphorus compounds may be used alone or in combination of two or more.

[0096] Examples of the amine compound include linear or branched primary amines, linear or branched secondary amines, linear or branched tertiary amines, alicyclic primary amines, alicyclic secondary amines, alicyclic tertiary amines, aromatic group-containing primary amines, aromatic group-containing secondary amines, aromatic group-containing tertiary amines, and the like. These amine compounds may have substituents (such as a hydroxyl group, etc.) as necessary. These amine compounds may be used alone or in combination of two or more.

[0097] Examples of the silane compound include alkoxysilane compounds, vinyl group-containing silane coupling agents, epoxy group-containing silane coupling agents, styryl group-containing silane coupling agents, (meth)acrylic group-containing silane coupling agents, amino group-containing silane coupling agents, isocyanate group-containing silane coupling agents, ureido group-containing silane coupling agents, mercapto group-containing silane coupling agents, acid anhydride group-containing silane coupling agents, and partial condensates thereof. These silane compounds may be used alone or in combination of two or more.

[0098] The above surface treatment can be carried out under treatment conditions commonly used by those skilled in the art. The above surface treatment may be carried out only one kind or in combination of two or more kinds.

[0099] Commercially available products may be used as the above-mentioned brilliant pigments. Examples of commercially available products include Alpaste 93-0647, 06-0672, TCR-2020, MG1000, etc. (all manufactured by Toyo Aluminum Co., Ltd.), Aluminum Paste MH-9901, etc. (manufactured by Asahi Kasei Corporation), and the like.

[0100] In one aspect, the above-mentioned fluorescent pigment can be preferably 1 part by mass or more and 45 parts by mass or less, more preferably 2 parts by mass or more and 35 parts by mass or less, based on 100 parts by mass of the resin solid content of the film-forming resin (A1). The pigment mass concentration of the above-mentioned fluorescent pigment in the aqueous first base paint composition can be preferably 2% by mass or more and 40% by mass or less, more preferably 2.5% by mass or more and 35% by mass, still more preferably 3% by mass or more and 30% by mass or less. Note that the above-mentioned aqueous first base paint composition may not contain a fluorescent pigment. In another aspect, the pigment mass concentration of the fluorescent pigment in the above-mentioned first base paint composition can be 0% by mass.

[0101] The above-mentioned colored pigment (C1) and fluorescent pigment may be used in the preparation of the first base paint composition after being made into a pigment dispersion paste. The pigment dispersion paste is obtained by previously dispersing a pigment, a pigment dispersant, and a part of the film-forming resin (A1) used as needed in a small amount of an aqueous medium. The pigment dispersant may be a resin having a structure containing a pigment affinity part and a hydrophilic part. Examples of the pigment affinity part and the hydrophilic part include nonionic, cationic, and anionic functional groups. The pigment dispersant may have two or more types of the above-mentioned functional groups in one molecule.

[0102] Examples of the nonionic functional group include a hydroxyl group, an amide group, a polyoxyalkylene group, etc. Examples of the cationic functional group include an amino group, an imino group, a hydrazino group, etc. Examples of the anionic functional group include a carboxyl group, a sulfo group, a phosphoric acid group, etc. Such a pigment dispersant can be produced by a method well known to those skilled in the art.

[0103] The pigment dispersant is not particularly limited as long as it does not contain a volatile basic substance in its solid content or has a content of 3% by mass or less, but those that can efficiently disperse the pigment with a small amount of the pigment dispersant are preferred. Commercially available products may be used as the pigment dispersant. Examples of commercially available products include, for example, Disperbyk-180 and Disperbyk-190 (both manufactured by BYK Chemie), which are anionic-nonionic dispersants, EFKAPOLYMER4550 (manufactured by BASF), EFKAPOLYMER4585 (manufactured by BASF), Solsperse 27000 (manufactured by Lubrizol), which is a nonionic dispersant, Solsperse 41000 and Solsperse 53095 (both manufactured by Lubrizol), which are anionic dispersants, and Disperbyk-2015 (manufactured by BYK Chemie) as a polymer copolymer, etc.

[0104] The weight average molecular weight of the pigment dispersant is preferably 1,000 or more and 100,000 or less, more preferably 2,000 or more and 100,000 or less, and still more preferably 4,000 or more and 50,000 or less.

[0105] The pigment dispersion paste can be prepared by mixing and dispersing the pigment dispersant, the pigment, and a part of the film-forming resin (A1) used as necessary according to a known method. The ratio of the pigment dispersant during the production of the pigment dispersion paste is preferably 1% by mass or more and 50% by mass or less based on the solid content of the pigment dispersion paste. By the ratio of the pigment dispersant being within the above range, the pigment dispersion stability and the physical properties of the resulting coating film can be maintained in a better range. The above ratio of the pigment dispersant is more preferably 3% by mass or more and more preferably 5% by mass or less.

[0106] The first base paint composition of the present disclosure preferably contains an aqueous medium. The aqueous medium in the present disclosure may be water; a hydrophilic solvent; or a mixture of water and a hydrophilic solvent. Examples of the hydrophilic solvent include glycol solvents such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, and triethylene glycol; glycol ether solvents such as ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether; alcohol solvents such as methanol, ethanol, isopropyl alcohol, and benzyl alcohol; cyclic ether solvents such as dioxane and tetrahydrofuran; ketone solvents such as acetone; and N-methyl-2-pyrrolidone, etc.

[0107] (Other components) In addition to the above components, the first base paint composition may contain additives commonly used by those skilled in the art as long as they do not affect the coating film performance and coating film appearance. Examples of the additives include pigments such as extender pigments, coloring pigments, and rust preventive pigments; anti-sagging and anti-settling agents; curing catalysts (organometallic catalysts); anti-color separation agents; dispersants; anti-foaming and anti-crawling agents; surface modifiers; viscosity regulators; thickeners; leveling agents; matting agents; antioxidants; ultraviolet light inhibitors; plasticizers; film-forming aids; anti-foaming agents; and phosphoric acid group-containing organic compounds, etc. Examples of the extender pigment include titanium oxide, calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, clay, talc, silica, and calcined kaolin, etc.

[0108] (Viscosity regulator) The first base paint composition of the present disclosure preferably contains a viscosity regulator. By containing a viscosity regulator, thixotropy is imparted to the first base paint composition, the coating workability is improved, and the appearance of the resulting multilayer coating film can be improved.

[0109] Examples of the viscosity modifier include organic viscosity modifiers and inorganic viscosity modifiers. Examples of the organic viscosity modifiers include crosslinked or non-crosslinked resin particles; swollen dispersions of fatty acid amides, amide-based fatty acids, phosphate salts of long-chain polyaminoamides, and other polyamide-based viscosity modifiers; and colloidal swollen dispersions of polyethylene oxide and other polyethylene-based viscosity modifiers. Examples of the inorganic viscosity modifiers include organic bentonite viscosity modifiers such as organic acid smectite clay and montmorillonite.

[0110] Examples of the thickener include associative nonionic urethane thickeners, alkali-swellable thickeners, and bentonite, which is an inorganic intercalation compound.

[0111] In the first base paint composition, the solid content concentration (total content ratio of the solid content) is 15% by mass or more and 40% by mass or less, more preferably 18% by mass or more and 35% by mass or less, and still more preferably 20% by mass or more and 30% by mass or less.

[0112] The first base paint composition can be produced by a method commonly used by those skilled in the art, such as kneading and dispersing a film-forming resin (A1), a curing agent (B1), a coloring pigment (C1) used as necessary, a pearlescent pigment, other components, and additives using a disper, a homogenizer, a kneader, or the like. In the above production method, for example, it is preferable to prepare and mix a paste containing the coloring pigment (C1) or the pearlescent pigment and a pigment dispersant used as necessary. As the pigment dispersant, the above commercially available pigment dispersants and the like can be used.

[0113] (First clear layer) The first clear layer can preferably be disposed between the first base layer and the second base layer. By including the first clear layer, unevenness and the like caused by the first base coating film can be smoothed, the first base coating film can be protected, and further aesthetics can be imparted. In one aspect, the multi-layer coating film of the present disclosure includes the first clear layer, and in another aspect, the multi-layer coating film of the present disclosure does not include the first clear layer.

[0114] The thickness of the above-mentioned first clear layer is preferably 15 μm or more and 40 μm or less, more preferably 20 μm or more and 30 μm or less.

[0115] The above-mentioned first clear layer can be formed by a first clear paint composition. As the above-mentioned first clear paint composition, a clear paint composition containing a film-forming resin, a curing agent, etc. can be used. A coloring component can also be further contained as long as it does not interfere with the design property of the base. In addition, a matting agent can also be contained to obtain a coating film with a desired gloss (gloss value, for example, from full gloss to full matte). Examples of the form of the clear paint composition include solvent-based, water-based, and powder-based types.

[0116] Preferable examples of the solvent-based clear paint composition include, from the viewpoints of transparency or acid etching resistance, etc., a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate, or an acrylic resin and / or a polyester resin having a carboxylic acid / epoxy curing system, etc.

[0117] Examples of the water-based clear paint composition include those containing a resin obtained by neutralizing a film-forming resin contained in the examples of the above-mentioned solvent-based clear paint with a base to make it water-based. This neutralization can be carried out by adding a tertiary amine such as dimethylethanolamine and triethylamine before or after polymerization.

[0118] As the powder-based clear paint composition, ordinary powder paints such as thermoplastic and thermosetting powder paints can be used. Since a coating film with good physical properties can be obtained, a thermosetting powder paint is preferred. Specific examples of the thermosetting powder paint include epoxy-based, acrylic-based, and polyester-based powder clear paint compositions, etc., and an acrylic-based powder clear paint composition with good weather resistance is particularly preferred.

[0119] In the first clear paint composition, in order to ensure the painting workability, it is preferable that a viscosity control agent is added. As the viscosity control agent, those generally exhibiting thixotropy can be used. As such, for example, conventionally known ones can be used. The first clear paint composition may contain a curing catalyst, a surface conditioner, etc. as necessary.

[0120] (Second base layer) The second base layer is laminated on the first base layer. The second base layer may be laminated in direct contact with the first base layer, or may be laminated on the first base layer via another layer provided on the first base layer, for example, the first clear layer. The second base layer can, for example, impart a brilliance to the multilayer coating film, but is not limited thereto.

[0121] The transmittance of the second base layer in the visible light region is 60% or more, preferably 65% or more and 100% or less, more preferably 70% or more and 100% or less, and still more preferably 75% or more and 100% or less.

[0122] The second base layer contains a bright pigment (C2). Examples of such bright pigments include metallic bright pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, and alloys thereof; mica pigments such as interference mica pigments and white mica pigments; graphite pigments; glass flake pigments, etc. From the viewpoint of imparting a transparency to the obtained multilayer coating film, the second base layer preferably contains a mica pigment.

[0123] In the bright pigment (C2), the content of the mica pigment is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and still more preferably 95% by mass or more and 100% by mass or less in the total solid content of the bright pigment (C2).

[0124] The average particle diameter of the above-described brilliant pigment (C2) is preferably 1 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less. The average thickness of the above-described brilliant pigment (C1) is preferably 0.01 μm or more and 6 μm or less, more preferably 0.1 μm or more and 5 μm or less.

[0125] When the above-described brilliant pigment (C2) is an aluminum pigment, surface treatment may be carried out as necessary. Examples of surface treatments that can be applied to aluminum pigments include surface treatment using metal oxide-based compounds, surface treatment using phosphorus compounds, surface treatment using amine compounds, surface treatment using silane compounds, and the like. As the above-described metal oxide-based compounds, phosphorus compounds, amine compounds, and silane compounds, the same compounds as those exemplified in the description of the brilliant pigment used in the above-described first base paint composition can be used. The above-described surface treatment can be carried out under treatment conditions commonly used by those skilled in the art. The above-described surface treatment may be carried out with only one type, or two or more types may be used in combination.

[0126] Commercially available products may be used as the above-described brilliant pigment. Examples of commercially available products include Alpaste 93-0647, 06-0672, TCR-2020, MG1000, etc. (all manufactured by Toyo Aluminum Co., Ltd.), Aluminum Paste MH-9901, etc. (manufactured by Asahi Kasei Corporation), and the like.

[0127] In the second base layer, the content of the brilliant pigment (C2) is preferably 0.1 part by mass or more and 15 parts by mass or less, more preferably 0.5 part by mass or more and 10 parts by mass or less, still more preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the solid content of the second base layer.

[0128] In the second base layer, the content of the mica pigment is preferably 0.1 part by mass or more and 15 parts by mass or less, more preferably 0.5 part by mass or more and 10 parts by mass or less, still more preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the solid content of the second base layer.

[0129] The second base layer may contain a coloring pigment. As such a coloring pigment, any of the pigments exemplified as the coloring pigments that the first base layer may contain can be used.

[0130] In the second base layer, the content of the coloring pigment is preferably 2 parts by mass or less, more preferably 0.001 part by mass or more and 1 part by mass or less, still more preferably 0.01 part by mass or more and 0.1 part by mass or less, per 100 parts by mass of the total solid content of the second base layer. When the content of the coloring pigment in the second base layer is within such a range, transparency and hue variability can be improved.

[0131] In the second base layer, it is preferable that the content of the black pigment is small. For example, in the second base layer, the content of the black pigment is preferably 0 part by mass or more and 0.1 part by mass or less, more preferably 0 part by mass or more and 0.05 part by mass or less, still more preferably 0 part by mass or more and 0.001 part by mass or less, per 100 parts by mass of the total solid content of the second base layer. When the content of the black pigment is within such a range, it is easy to enhance the transparency of the resulting multilayer coating film.

[0132] The thickness of the second base layer is, for example, 0.1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and is, for example, 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less.

[0133] The second base layer can be formed using a second base paint composition. The second base paint composition contains a film-forming resin (A2) and a curing agent (B2). In one aspect, the second base paint composition further contains a bright pigment (C2), and in such an aspect, the second base paint composition may or may not further contain a coloring pigment. In another aspect, the second base paint composition does not contain a bright pigment (C2), and in such an aspect, the second base paint composition may or may not further contain a coloring pigment.

[0134] (Film-forming resin (A2)) The above coating film-forming resin (A2) is a resin capable of forming a coating film by reacting with a curing agent (B2) described later, and any of the resins described as the coating film-forming resin (A1) can be used. The resin composition of the coating film-forming resin (A1) and the resin composition of the coating film-forming resin (A2) may be the same or different.

[0135] The above coating film-forming resin (A2) preferably contains an acrylic resin, and more preferably contains an acrylic resin aqueous dispersion. By both the coating film-forming resin (A1) and the coating film-forming resin (A2) containing an acrylic resin, and by the coating film-forming resin (A2) containing an acrylic resin, the storage stability of the resulting coating composition, and various properties such as the water resistance and weather resistance of the resulting coating film can be improved. Also, the adhesion between the first base coating film and the second base coating film can be improved. As the above acrylic resin and acrylic resin aqueous dispersion, any of the resins and aqueous dispersions described as the acrylic resin and acrylic resin aqueous dispersion in the coating film-forming resin (A1) can be used, and they can be produced by the same method.

[0136] In the coating film-forming resin (A2), the acrylic resin contained in the acrylic resin aqueous dispersion may be in particulate form, and the average particle diameter of such particles is preferably 0.01 μm or more and 1.0 μm or less.

[0137] In the coating film-forming resin (A2), the acrylic resin contained in the acrylic resin aqueous dispersion may be core-shell type particles.

[0138] In the coating film-forming resin (A2), the acid value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 1 mgKOH / g or more and 80 mgKOH / g or less, more preferably 2 mgKOH / g or more and 70 mgKOH / g or less, still more preferably 3 mgKOH / g or more and 60 mgKOH / g or less.

[0139] In the film-forming resin (A2), the hydroxyl value of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. When it is within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0140] In the film-forming resin (A2), the weight average molecular weight of the acrylic resin contained in the acrylic resin aqueous dispersion is preferably 50,000 or more and 5,000,000 or less, more preferably 50,000 or more and 1,000,000 or less. When it is within the above range, there is an advantage that various properties such as the hardness, adhesion, and water resistance of the obtained coating film become good.

[0141] In the solid content of the above film-forming resin (A2), the content of the solid content of the acrylic resin aqueous dispersion is preferably 20% by mass or more and 90% by mass or less, more preferably 25% by mass or more and 85% by mass or less, still more preferably 30% by mass or more and 80% by mass or less. When it is within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the obtained coating film becomes good.

[0142] In the above second base paint composition, the content of the solid content of the above polyol resin can be preferably 1 part by mass or more and 90 parts by mass or less, more preferably 10 parts by mass or more and 70 parts by mass or less, still more preferably 30 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total of the solid content of the above acrylic resin aqueous dispersion.

[0143] In the above second base paint composition, the content of the solid content of the above polyester resin aqueous dispersion can be preferably 20 parts by mass or more and 80 parts by mass or less, more preferably 30 parts by mass or more and 70 parts by mass or less, still more preferably 40 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass in total of the solid content of the above acrylic resin aqueous dispersion.

[0144] The above coating-forming resin (A2) preferably has a hydroxyl group. The hydroxyl value of the coating-forming resin (A2) is preferably 30 mgKOH / g or more and 120 mgKOH / g or less, more preferably 35 mgKOH / g or more and 100 mgKOH / g or less. By being within the above range, there is an advantage that the curing reaction proceeds sufficiently and the hardness of the resulting coating film becomes good.

[0145] The content of the solid content of the above coating-forming resin (A2) can be preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 85% by mass or less, still more preferably 20% by mass or more and 80% by mass or less in 100% by mass of the solid content of the aqueous second base coating composition.

[0146] (Hardener (B2)) The above hardener (B2) can be a compound having two or more groups capable of reacting with the coating-forming resin (A2) in one molecule, and together with the coating-forming resin (A2), it corresponds to a coating-forming component. As the above hardener (B2), any of the compounds described as the hardener (B1) can be used. The hardener (B1) and the hardener (B2) may be the same or different.

[0147] In one aspect, the above hardener (B2) preferably contains an amino resin, and more preferably contains a melamine resin. By containing a melamine resin, a coating film can be formed by the self-polymerization of the melamine resin and the reaction between the amino group contained in the melamine resin and the hydroxyl group that may be contained in the coating-forming resin (A2).

[0148] The content of the solid content of the above melamine resin may be 0% by mass in 100% by mass of the total solid content of the above hardener (B2), preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, still more preferably 95% by mass or more and 100% by mass or less.

[0149] The content of the above melamine resin may be 0 part by mass in 100 parts by mass in total of the solid content of the above coating film-forming resin (A2) and the solid content of the curing agent (B2), preferably 10 parts by mass or more and 80 parts by mass or less, and may further be 20 parts by mass or more and 70 parts by mass or less. Thereby, there is an advantage that various physical properties such as the hardness, adhesion, and water resistance of the obtained coating film become good.

[0150] The content rate of the solid content of the curing agent (B2) in the aqueous second base coating composition is preferably 20% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less in 100% by mass in total of the solid content of the coating film-forming resin (A2) and the solid content of the curing agent (B2).

[0151] (Glossy pigment (C2)) The glossy pigment (C2) has the same meaning as the glossy pigment (C2) that can be contained in the second base layer.

[0152] The second base coating composition of the present disclosure contains an aqueous medium. Such an aqueous medium has the same meaning as the aqueous medium that can be contained in the first base coating composition.

[0153] (Other components) In addition to the above components, the second base coating composition may contain additives that are usually used by those skilled in the art within a range that does not affect the coating film performance and the coating film appearance. As the above additives, for example, one or more of those used in the first base coating composition may be appropriately contained.

[0154] (Viscosity regulator) The second base coating composition of the present disclosure preferably contains a viscosity regulator. The viscosity regulator may appropriately contain one or more of those used as the first base coating composition.

[0155] The above second base layer preferably contains a coloring pigment. As such a coloring pigment, for example, one or more of those used in the first base coating composition may be appropriately contained. As the above extender pigment, for example, one or more of those used in the first base coating composition may be appropriately contained.

[0156] As the above-mentioned pigment, from the viewpoint of improving weather resistance and ensuring hiding power, it is preferably a coloring pigment. In particular, titanium dioxide is more preferable because it has excellent coloring hiding power and is inexpensive. Further, as the pigment, a standard gray paint composition having carbon black and titanium dioxide as main pigments may be used. Alternatively, a paint composition having the same lightness or hue as the second base paint composition and a paint composition combining various coloring pigments may be used. The first base paint composition of the present disclosure can act as a primer when applying the second base paint composition, and by containing a coloring pigment, it can also act as a color base.

[0157] The above-mentioned bright pigment (C2) and the above-mentioned coloring pigment may be used in the preparation of the second base paint composition after being made into a pigment dispersion paste. The pigment dispersion paste is obtained by previously dispersing a pigment, a pigment dispersant, and a part of the film-forming resin (A2) used as necessary in a small amount of an aqueous medium. As such a pigment dispersant, any of the compounds and materials described as the pigment dispersants that can be used in the first base paint composition can be used.

[0158] Examples of the above-mentioned thickener include associative nonionic urethane thickeners, alkali-swellable thickeners, bentonite which is an inorganic intercalation compound, and the like.

[0159] In the second base paint composition, the solid content concentration is 15% by mass or more and 40% by mass or less, preferably 18% by mass or more and 35% by mass or less, more preferably 20% by mass or more and 30% by mass or less.

[0160] The above-mentioned second base paint composition can be produced by a method commonly used by those skilled in the art, such as kneading and dispersing the film-forming resin (A2), the curing agent (B2), the bright pigment (C2) used as necessary, other components, additives, etc. using a disper, a homogenizer, a kneader, etc. In the above manufacturing method, for example, it is preferable to prepare and mix in advance a paste containing a phosphorescent pigment (C2) and, if necessary, a pigment dispersant to be used. As the pigment dispersant, the above-mentioned commercially available pigment dispersants or the like can be used.

[0161] (Second clear layer) The above second clear layer can preferably be laminated on the above second base layer. By including the second clear layer, unevenness and the like caused by the second base coating film can be smoothed, the second base coating film can be protected, and furthermore, an aesthetic appearance can be imparted. In one aspect, the multilayer coating film of the present disclosure includes a second clear layer.

[0162] The thickness of the above second clear layer can be 10 μm or more and 80 μm or less, preferably 20 μm or more and 60 μm or less. When the thickness of the second clear layer is within such a range, unevenness can be sufficiently concealed, and defects such as runs or sags during painting can be suppressed.

[0163] The above second clear layer can be formed from a second clear paint composition. As the above second clear paint composition, a clear paint composition containing a film-forming resin, a curing agent, and the like can be used. A coloring component can also be further contained as long as it does not interfere with the design of the base. In addition, a matting agent can also be contained to obtain a coating film with a desired gloss (gloss value, for example, from full gloss to full matte). Examples of the form of the clear paint composition include solvent-based, water-based, and powder-based.

[0164] Preferable examples of the solvent-based clear paint composition include, from the viewpoints of transparency or acid etching resistance, etc., a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate, or an acrylic resin and / or a polyester resin having a carboxylic acid / epoxy curing system, etc.

[0165] Examples of the aqueous clear coating composition include those containing a resin obtained by neutralizing a film-forming resin contained in the examples of the solvent-based clear coating with a base to make it aqueous. This neutralization can be carried out by adding a tertiary amine such as dimethylethanolamine and triethylamine before or after polymerization.

[0166] As the powder clear coating composition, ordinary powder coatings such as thermoplastic and thermosetting powder coatings can be used. Since a coating film with good physical properties can be obtained, a thermosetting powder coating is preferred. Specific examples of the thermosetting powder coating include epoxy-based, acrylic-based, and polyester-based powder clear coating compositions, etc. Among them, an acrylic-based powder clear coating composition with good weather resistance is particularly preferred.

[0167] In the second clear coating composition, in order to ensure coating workability, it is preferable to add a viscosity control agent. As the viscosity control agent, those generally showing thixotropy can be used. As such, for example, those known in the art can be used. The first clear coating composition may contain a curing catalyst, a surface conditioner, etc. as necessary.

[0168] The absolute value |h2 - h1| of the difference between the hue h1 of the first base layer and the hue h2 of the multilayer coating film is preferably 20 or less, more preferably 0 or more and 5 or less, and still more preferably 0 or more and 3 or less. By being in such a range of the absolute value of the color difference, it is easy to obtain the target hue and the coating workability can be good.

[0169] In the present disclosure, the hue is a parameter in the L*C*H* color system and can be measured in accordance with JIS Z8729. Also, the hue h1 of the first base layer may be measured in a state where the first base layer is formed on the intermediate coating layer before forming the second base layer.

[0170] The chroma C1 of the above-described first base layer can preferably be 30 or more, more preferably 45 or more and 100 or less, and still more preferably 60 or more and 100 or less. When the chroma of the first base layer is within such a range, the chroma of the resulting multilayer coating film can be increased.

[0171] The chroma C1 of the above-described multilayer coating film can preferably be 30 or more, more preferably 45 or more and 100 or less, and still more preferably 60 or more and 100 or less.

[0172] In the present disclosure, the chroma can be measured in accordance with JIS Z8729, similar to the hue.

[0173] The specular gloss value Si15 of the above-described multilayer coating film can preferably be 15 or more.

[0174] (Method for manufacturing a multilayer coating film) The multilayer coating film of the present disclosure includes a step of coating an intermediate coating composition on an object to be coated to form an intermediate coating layer, a first base coating film forming step of coating a first base coating composition on the above-described intermediate coating layer to form a first base coating film, a second base coating film forming step of coating an aqueous second base coating composition on the above-described first base coating film to form a second base coating film, and at least a heat curing step of heat-curing the above-described first base coating film and second base coating film to form a multilayer coating film.

[0175] Typically, the intermediate coating layer can be formed by coating an intermediate coating composition to form an intermediate coating film and heat-curing the intermediate coating film. The heating temperature and time in the case of heat-curing the intermediate coating film can be appropriately selected according to the composition of the coating composition (aqueous or solvent-based) and the type of the object to be coated. The heating temperature can be appropriately selected, for example, in the range of 80 to 180 °C, preferably in the range of 100 to 160 °C. The heating time can be appropriately selected, for example, in the range of 5 minutes to 60 minutes, preferably in the range of 10 minutes to 30 minutes. When preheating the intermediate coat film, the temperature may be, for example, 30 to 80°C, and the preheating time may be, for example, 1 minute to 60 minutes.

[0176] As the above-mentioned object to be coated, it can be used for various substrates, for example, metal molded products, plastic molded products, foams, etc. The aqueous base paint composition of the present disclosure can be suitably used in the automotive exterior panel coating such as automotive bodies and automotive parts. As the metal molded product, for example, plates and molded products made of iron, copper, aluminum, tin, zinc, etc., and alloys containing these metals can be mentioned. Specifically, automotive bodies and parts such as passenger cars, trucks, motorcycles, buses, etc. can be mentioned.

[0177] The above-mentioned metal molded product may be previously subjected to chemical conversion treatment with phosphate, zirconium salt, chromate, etc., and then an electrodeposition coating film may be formed as an undercoat layer. As the electrodeposition paint composition that can be used for forming the electrodeposition coating film, a cationic electrodeposition paint composition and an anionic electrodeposition paint composition can be mentioned.

[0178] As the above-mentioned plastic molded product, for example, plates and molded products made of polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. can be mentioned. Specific examples of plastic molded products include automotive parts such as spoilers, bumpers, mirror covers, grills, door knobs, etc. These plastic molded products may be subjected to primer coating for enabling electrostatic coating as an undercoat layer.

[0179] The above-mentioned first base paint composition and second base paint composition can be applied to the object to be coated by methods generally used in the paint field. Examples of coating methods include multi-stage coating (preferably two-stage coating) by air spray coating, airless spray coating, electrostatic spray coating, air electrostatic spray coating, and coating combining air electrostatic spray coating and a rotary atomization type electrostatic coating machine.

[0180] When applying and heat-curing the above-described first base paint composition and second base paint composition, the heating temperature and time can be appropriately selected according to the composition of the paint composition (aqueous or solvent-based) and the type of the object to be painted. The heating temperature can be appropriately selected, for example, in the range of 80 to 180 °C, preferably in the range of 100 to 160 °C. The heating time can be appropriately selected, for example, in the range of 5 minutes to 60 minutes, preferably in the range of 10 minutes to 30 minutes. The temperature when preheating the first base coating film or the second base coating film may be, for example, 30 to 80 °C, and the preheating time may be, for example, 1 minute to 60 minutes.

[0181] It is preferable to apply the above-described first base paint composition so that the dry film thickness t1 of the cured first base coating film is within the range of 8 to 20 μm, and more preferably so that it is 10 to 15 μm. Also, it is preferable to apply the second base paint composition so that the dry film thickness of the cured second base coating film t2 is within the range of 8 to 20 μm, and more preferably so that it is 10 to 15 μm.

[0182] The above manufacturing method may further include a first clear coating film forming step of applying a first clear paint on the first base coating film after forming the first base coating film and before forming the second base coating film to form a first clear coating film. That is, a clear paint may be applied wet-on-wet on the uncured first base coating film without heat-curing it to form an uncured first clear coating film. In the heat-curing step, the uncured first base coating film and the first clear coating film may be simultaneously heat-cured to form a multi-layer coating film including a first base layer and a first clear layer. By forming the first clear coating film, unevenness and the like caused by the first base coating film can be smoothed, protected, and further an aesthetic appearance can be imparted.

[0183] The above manufacturing method may further include a second clear coating film forming step of coating a second clear coating material on the second base coating film after the formation of the second base coating film and before heat curing to form a second clear coating film. That is, a clear coating material may be wet-on-wet coated on the uncured second base coating film without heat curing it to form an uncured second clear coating film. In the heat curing step, the uncured second base coating film and the second clear coating film may be simultaneously heat cured to form a multi-layer coating film including a second base layer and a second clear layer. By forming the second clear coating film, unevenness and the like caused by the second base coating film can be smoothed, protected, and further an aesthetic appearance can be imparted. The above manufacturing method may include both the first clear coating film forming step and the second clear coating film forming step.

[0184] Examples of the method of coating the clear coating material include a coating method using a rotary atomizing electrostatic coater called a micro bell or a micro bell.

[0185] When including the clear coating film forming step, the heat curing temperature in the heat curing step is preferably 80 to 180°C, more preferably 120 to 160°C, from the viewpoints of curability and physical properties of the obtained multi-layer coating film. The heat curing time can be arbitrarily set according to the above temperature, and it is appropriate that the time is 10 to 30 minutes at a heat curing temperature of 80°C to 160°C.

[0186] The multi-layer coating film of the present disclosure has a brilliance, can achieve both the hiding property and the chroma of the coating film, and is preferably used for coating automobile bodies and the like.

Example

[0187] The present invention will be described more specifically by the following examples, but the present invention is not limited thereto.

[0188] [Example 1] (I) Preparation of the object to be coated As the object to be coated, a zinc phosphate-treated steel sheet provided with a cured electrodeposition coating film was prepared. The cured electrodeposition coating film was formed by electrodepositing "Power Niks", a cationic electrodeposition coating composition manufactured by Nippon Paint Co., Ltd., on the zinc phosphate-treated steel sheet so that the dry film thickness became 20 μm, and then heating at 160 °C for 30 minutes.

[0189] (II) Preparation of Paint (II-1) Preparation of Intermediate Coating Paint 51.0 parts by mass of a thermosetting polyester resin (manufactured by Nippon Paint Co., Ltd., hydroxyl value 80, acid value 8 mgKOH / g, number average molecular weight 1800, solid content 70% by mass) and 49 parts by mass of titanium dioxide pigment "CR-97" (manufactured by Ishihara Sangyo Co., Ltd.) were added and uniformly dispersed. Further, 25.5 parts by mass of a melamine resin "Uban 128" (manufactured by Mitsui Cytec Co., Ltd., solid content 60% by mass) was added and uniformly dispersed to obtain a white intermediate coating paint.

[0190] (II-2) Preparation of Base Paint Composition For the preparation of the base paint composition, an aqueous resin composition obtained by mixing the following (1) to (9) was used. (1) 236 parts of an acrylic emulsion resin (average particle diameter 150 nm, non-volatile content 20% by mass, solid content acid value 20 mgKOH / g, hydroxyl value 40 mgKOH / g) manufactured by Nippon Paint Co., Ltd., (2) 10 parts by mass of a 10% by mass aqueous solution of dimethylethanolamine, (3) 28.3 parts by mass of a water-soluble acrylic resin (non-volatile content 30% by mass, solid content acid value 40 mgKOH / g, hydroxyl value 50 mgKOH / g) manufactured by Nippon Paint Co., Ltd., (4) 8.6 parts by mass of "Prime Pole PX-1000" (bifunctional polyether polyol, number average molecular weight 400, hydroxyl value 278 mgKOH / g, primary / secondary hydroxyl value ratio = 63 / 37, non-volatile content 100%) manufactured by Sanyo Chemical Industries, Ltd., (5) 21.5 parts by mass of "Cymel 204" (mixed alkylated melamine resin, non-volatile content 100% by mass) manufactured by Mitsui Chemicals, Inc. (6) 26 parts by mass of "Neolets R-9603" (polycarbonate-based urethane emulsion resin, non-volatile content 33% by mass) manufactured by Abisia Co., Ltd., (7) 0.2 parts by mass of lauryl acid phosphate, (8) 10 parts by mass of 2-ethylhexanol, (9) 25 parts by mass of mono-2-ethylhexyl ether, A base paint composition containing the above was prepared.

[0191] In the above aqueous resin composition, the total solid content mass of the film-forming resin and the solid content mass of the curing agent (the solid content amount of the main resin) was 100 parts by mass. The pigments shown in Table 1 were added to the above aqueous resin composition so as to have the contents (PWC) shown in Table 1, and a first base paint composition and a second base paint composition were obtained.

[0192] The mass concentration of the pigment is calculated by the following formula: Pigment mass concentration (PWC) = (mass of pigment) / [(total mass of resin solid content of film-forming resin, resin solid content of curing agent, and solid content of additive) + (total mass of pigment)] × 100 (%) Calculated by.

[0193] (II-3) Preparation of clear paint As the clear paint, an acid epoxy curing type clear paint (trade name: Mac Flow O-1820 Clear, manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was prepared.

[0194] (III) Formation of multi-layer coating film On the object to be coated, the intermediate coating paint (pre-diluted at 25 seconds (measured at 20 °C using a No. 4 Ford cup)) was air-sprayed using an Anest Iwata air spray gun W-101-132G to a dry film thickness of 35 μm. This coated plate was heated in a dryer at 140 °C for 30 minutes to obtain a coated article of the intermediate coating layer. Subsequently, the first base paint was air-sprayed to a dry film thickness of 15 μm under the conditions of room temperature of 23°C and humidity of 68%. After setting for 3 minutes, preheating was carried out at 80°C for 4 minutes. The painted plate was allowed to cool to room temperature, and the clear paint was air-sprayed to a dry film thickness of 25 μm and set for 7 minutes. This painted plate was heated in a dryer at 140°C for 30 minutes to obtain a painted article with a first base layer. Subsequently, the second base paint was air-sprayed to a dry film thickness of 15 μm under the conditions of room temperature of 23°C and humidity of 68%. After setting for 3 minutes, preheating was carried out at 80°C for 4 minutes. The painted plate was allowed to cool to room temperature, and the clear paint was air-sprayed to a dry film thickness of 35 μm and set for 7 minutes. Finally, this painted plate was heated in a dryer at 140°C for 30 minutes to obtain a painted article with a multilayer coating film.

[0195] (IV) Evaluation The following evaluations were performed on the painted articles. The results of evaluations (1) to (6) are shown in Table 1. (1) Lightness L*45 Using a spectrophotometer (BYK Gardner, BYK-mac i), the lightness L*45 of the intermediate coating layer was obtained. (2) Chroma C*45 Using a spectrophotometer (BYK Gardner, BYK-mac i), the chroma C*45 of the first base layer and the multilayer coating film was obtained. (3) Glitter feeling Si15 value Using a spectrophotometer (BYK Gardner, BYK-mac i), the glitter feeling Si15 value of the multilayer coating film was obtained. (4) Hue h15 Using a spectrophotometer (BYK Gardner, BYK-mac i), h15 was obtained. Let the hue of the first base coating film be h1 and the hue of the multilayer coating film be h2, and the difference h1 - h2 was calculated. (5) Transmittance in the visible light range The individual light transmittances of the first base coating film and the second base coating film were measured using a spectrophotometer (manufactured by Hitachi, product name: U-4100) in the wavelength range of 400 to 700 nm under the conditions of wavelength scan mode, scan speed of 60 nm / min, and sampling interval of 2 nm. The average light transmittance was obtained by averaging the light transmittances every 10 nm. (6) Concealability Color stability during film thickness variation Coated articles having a multilayer coating film with the film thickness of the base coating film varied by ±20% were prepared and compared with the coated articles prepared with the normal film thickness, and it was evaluated whether there was a sense of disharmony in color visually. ○: Almost no sense of disharmony ×: Sense of disharmony

[0196] [Example 2, Comparative Examples 1 to 7] Except that the pigment compositions in the first base paint and the second base paint were changed to those shown in Table 1, a multilayer coating film was obtained and evaluated in the same manner as in Example 1.

[0197]

Table 1

[0198] Examples 1 and 2 are examples of the present disclosure, and it was confirmed that they have a luster and can achieve both concealability and chroma of the coating film. Comparative Examples 1 and 2 are examples where the 45-degree specular gloss of the intermediate coating layer is less than 80, the color stability during film thickness variation is not sufficient, and the chroma is not sufficiently satisfactory. Comparative Example 3 is an example where the transmittance of the second base layer in the visible light region is less than 60%, the color stability during film thickness variation is not sufficient, and the chroma is not sufficiently satisfactory. Comparative Example 4 is an example where the second base layer does not contain a bright pigment, and the coating film did not show a luster. Comparative Example 5 is an example where the transmittance of visible light of the first base layer exceeds 30%, the color stability during film thickness variation is not sufficient, and the chroma is not sufficiently satisfactory.

Industrial Applicability

[0199] The multilayer coating film of the present disclosure has a brilliant feeling, can achieve both the hiding property and the chroma of the coating film, and is preferably used for coating automobile bodies and the like.

Claims

1. It comprises an intermediate coat layer, a first base layer laminated on the intermediate coat layer, and a second base layer laminated on the first base layer, the 45-degree visual lightness L* of the intermediate coat layer is 80 or more, the transmittance of the first base layer in the visible light range is 5% or more and 30% or less, the transmittance of the second base layer in the visible light range is 60% or more, the second base layer contains a pearlescent pigment, a multilayer coating film.

2. The multilayer coating film according to Claim 1, wherein the absolute value of the difference between the hue h1 of the first base layer and the hue h2 of the multilayer coating film is 20 or less.

3. The multilayer coating film according to Claim 1, wherein the chroma C1 of the first base layer is 60 or more.

4. The multilayer coating film according to Claim 1, wherein the chroma C2 of the multilayer coating film is 60 or more.

5. The multilayer coating film according to Claim 1, wherein the brilliance feeling Si15 value of the multilayer coating film is 15 or more.

6. The first base layer contains a coloring pigment, The content of the coloring pigment is 5 parts by mass or more and 60 parts by mass or less in 100 parts by mass of the total solid content of the first base layer. The multilayer coating film according to Claim 1.

7. The second base layer contains a coloring pigment, The content of the coloring pigment is 2 parts by mass or less in 100 parts by mass of the total solid content of the second base layer. The multilayer coating film according to Claim 1.

8. The content of the black pigment in the second base coating film is 0 part by mass or more and 0.1 part by mass or less in 100 parts by mass of the total solid content of the second base layer. The multilayer coating film according to Claim 1.

9. The content of the mica-based pigment in the second base coating film is 0.1 part by mass or more and 15 parts by mass or less in 100 parts by mass of the total solid content of the second base layer. The multilayer coating film according to Claim 1.

10. The multilayer coating film according to any one of Claims 1 to 9, further comprising a first clear layer between the first base layer and the second base layer.

11. The multilayer coating film according to Claim 10, further comprising a second clear layer laminated on the second base layer.

Images