JP4259330B2 - Metallic coating composition, coating film forming method and coating film - Google Patents

Description

  The present invention relates to a metallic paint composition, a coating film forming method using the paint, and a coated article. More specifically, the present invention relates to a method for obtaining a glittering coating film excellent in all of brightness, flip-flop properties and concealing properties by selectively using aluminum flakes used in a base coat paint.

Various methods for forming a coating film excellent in brightness, flip-flop property, and concealment property using metallic base coat paint and clear paint have been tried.
Here, the meaning of the words expressing the appearance of the coating film used in the present invention will be described. “Luminous sensation” refers to a lustrous metallic luster. Generally, the larger the particle, the stronger this radiance is, and a coating film with a high “brightness” is preferred. “Flip-flop” refers to a metallic luster with directionality that varies in brightness depending on the viewing angle, with brighter highlights being preferred and darker shades being preferred. “Concealment” refers to the degree of influence of the substrate, and the smaller the influence of the substrate, the better.

As a method of obtaining a coating film appearance excellent in glitter, (A) 100 solid parts by weight of a coating film forming resin, and (B) an average particle diameter D ₅₀
A coating composition containing 0.1 to 30 parts by weight of an aluminum flake pigment having a particle diameter of 20 ± 5 μm, an average particle thickness of 0.5 to 1 μm, and a gradient n in the rosin-Rammler diagram of 2.7 or more. A coating film forming method characterized by top-coating and curing at the same time is known (claims 1 and 2 of Patent Document 1). However, this method is excellent in uniform and dense metallic luster. Although a coating film can be obtained, it has a feeling of brightness and flip-flop properties, but has a disadvantage of insufficient concealment.
JP-A-8-170034

In addition, as a method for obtaining an aluminum-like metallic luster having excellent flip-flop properties, a method for forming a multilayer coating film in which a base coat paint (A), a metallic paint (B), and a clear paint (C) are sequentially applied, comprising: Using (A) a color pigment, the brightness (brightness) of the coating film is set to 0 to 40 in terms of L value, and as a metallic pigment in the metallic paint (B), a thickness of 0.01 to 0.2 μm, What is claimed is: 1. A method for forming a multilayer coating film, comprising using aluminum flakes having an aspect ratio of 100 to 300 and having a solid content of 400 parts by weight or less of the resin composition per 100 parts by weight of the aluminum flakes However, in this method, at least a base coat, a metallic coat (base coat), and a clear are known. Must be 3 coat over preparative, as compared with two-coat consisting of a base coat and a clear layer, there is a disadvantage that the cost and productivity is poor.
JP 2000-084483 A

In addition, a glossy coating film having a design that exhibits interference and has multi-coloredness due to coloration, and exhibits high chroma in the highlight area and glitter and high chroma in the shade area. As a method, an aluminum flake pigment (1) coated with a vehicle and a metal oxide composite comprising two or more metal elements, and a glittering paint composition containing an aluminum flake pigment (2) other than the above (1) are used. (Patent Document 3: Claim 1)
However, this method is not suitable for obtaining a simple silver color because the coating film is colored due to the use of an oxide complex composed of a coloring metal element. Moreover, although it is excellent in radiance, there is a drawback that the concealing property and the flip-flop property are insufficient.
JP 2002-121492 A

In addition, as a method for preventing unevenness in the glitter feeling of the coating film formed by uniforming the orientation of the large particle size glitter material on the surface of the coating film, the first stage for forming the glittering base coating film has an average particle diameter. A coating film forming method using a large particle size scaly glitter material having an average particle diameter of 15 μm or more is known as the second stage for forming a glittering base coating film using a small particle scaly glitter material having a particle size of 10 μm or less. (Patent Document 4: Claims 1 and 2)
However, this method is also a three-coat specification including a first stage glitter base, a second stage glitter base, and a clear, as in Patent Document 2, compared to two coats consisting of a base coat and a clear layer. There is a disadvantage that the cost and productivity are inferior. In addition, the average particle diameter of the glitter base of the second stage is larger than the average particle diameter of the glitter base of the first stage, and it is difficult to obtain a stable brightness.
JP 2002-102798 A

  It is thought that it is very difficult to obtain a metallic coating film that satisfies all of the glitter feeling, flip-flop property, and concealment property in the metallic coating film, and the base coat is divided into the first base coat and the second base coat. A painting method has been devised.

  An object of the present invention is to obtain a metallic coating film that satisfies all of glitter, flip-flop properties, and concealment properties by a highly productive wet-on-wet 2-coat 1-bake coating method.

  As a result of earnest research to solve the above problems, the present inventor has selectively used three different types of aluminum flake pigments as a base coat paint, thereby achieving all the performances of glitter, flip-flop, and concealment. It was found that a metallic coating film satisfying the above conditions can be obtained by 2 coats and 1 bake, and the present invention has been completed based on this finding.

That is, the present invention, (A) an average particle diameter _{D 50} of more than 13 .mu.m, 25 [mu] m or less, an average thickness of 0.5μm or more, 1. Aluminum flake pigment of 5 μm or less,
(B) An average particle diameter D ₅₀ of 13 μm or more, 25 μm or less, an average thickness of 0.01 μm or more (excluding 0.08 μm or less ) , an aluminum flake pigment of less than 0.5 μm, and (C) an average particle diameter D ₅₀ contains 4 μm or more and less than 13 μm, an aluminum flake pigment having an average thickness of 0.01 μm or more (excluding 0.08 μm or less) and 0.5 μm or less,
In the solid content mass ratio of the aluminum flake pigment, A / B is 10/90 to 90/10, (A + B) / C is 90/10 to 30/70, and (A + B + C) with respect to 100 mass parts of resin solid content. ) Is 5 to 50 parts by mass in solid content, to provide a metallic paint composition.

The present invention also provides a method for forming a coating film in which the above-described metallic paint is applied, and then the clear paint is applied and cured by wet-on-wet.
Furthermore, this invention provides the coating film obtained by said method with said coating material.

  By applying the coating composition of the present invention to wet-on-wet two-coat one-bake coating, it is possible to obtain a metallic coating film appearance excellent in all of glitter, flip-flop properties and concealment properties by an inexpensive method with high productivity.

  In the metallic paint composition and the coating film forming method of the present invention, a metallic base coat paint and a clear paint containing three types of aluminum flake pigments are sequentially applied on a substrate by wet on wet.

  The metallic base coat paint used in the method of the present invention is a liquid paint containing a film-forming base resin, a scaly glitter pigment, a solvent, an additive, and a crosslinking agent added as necessary. Examples of the base resin include acrylic resins having a crosslinkable functional group such as hydroxyl group, carboxyl group, silanol group, and epoxy group, polyester resin, alkyd resin, fluororesin, urethane resin, silicone-containing resin, and cellulose resin. Can be mentioned. These base resins can be used individually by 1 type, or can also be used in combination of 2 or more type.

  Examples of the additive include an ultraviolet absorber, a hindered amine light stabilizer, an antioxidant, a rheology control agent, and a surface conditioner. By adding an ultraviolet absorber, a hindered amine light stabilizer, an antioxidant, etc., the weather resistance of the coating film can be improved. By adding a rheology control agent, the coating workability and the coating film appearance can be improved. By adding the surface conditioner, the appearance of the coating film can be improved.

  Examples of the crosslinking agent include melamine resin, polyisocyanate compound or block polyisocyanate compound, epoxy resin or epoxy compound, carboxyl group-containing resin or compound, acid anhydride, alkoxysilane group-containing resin or compound, and the like. These crosslinking agents can be used alone or in combination of two or more.

Aluminum flake pigment of metallic base coating composition used in the present invention the method is (A) an average particle diameter _{D 50} of more than 13 .mu.m, 25 [mu] m or less, an average thickness of 0.5μm or more, 1.5 [mu] m or less aluminum flake pigment (B) the average particle diameter _{D 50} of more than 13 .mu.m, 25 [mu] m or less (excluding 0.08μm or less) the average thickness is more than 0.01 [mu] m, the aluminum flake pigment (C) of less than 0.5μm average particle diameter _{D 50} of 4μm or more, It consists of three types of aluminum flake pigments having an average thickness of less than 13 μm, an average thickness of 0.01 μm or more (excluding 0.08 μm or less) , and 1.3 μm or less. / 90-90 / 10, (A + B) / C is 90 / 10-30 / 70, and (A + B + C) is solid with respect to 100 parts by mass of resin solid content. In 5 to 50 parts by weight.

The properties of each particle described in the present invention can be determined by the following measuring method.
The average particle diameter D ₅₀ indicates the 50% value of the particle size distribution measured by laser diffraction particle size distribution measuring apparatus. The average particle thickness (μm) is a value determined by the formula [4000 / water surface coverage (cm ² / g)], and the measurement method is, for example, “Aluminum Handbook” (9th edition, issued on April 15, 1972). , Association of Light Metals; Asakura Shoten), page 1243.

(A) an average particle diameter _{D 50.} 13 to 25 [mu] m, the aluminum flake pigment with an average thickness of 0.5 to 1.5 [mu] m, the brightness sensation in the coating film, can give flip-flop property, masking property It is inferior to that. Examples of commercially available aluminum flake pigments include “Alpaste 56-501”, “Alpaste TCR-3030”, and “Alpaste TCR-3040” manufactured by Toyo Aluminum Co., Ltd.

The aluminum flake pigment (A) has an unfavorable appearance when the average particle diameter D ₅₀ is 25 μm or more and / or the average thickness is 1.5 μm or more.

(B) The aluminum flake pigment has a feature that it can provide the coating film with a hiding property without greatly impairing the flip-flop property and the brightness, and as a commercially available aluminum flake pigment, Toyo Aluminum ( "Alpaste 61-528" manufactured by Co., Ltd., "SAP 550N" manufactured by Showa Aluminum Co., Ltd., and the like.

(C) Aluminum flake pigments can provide concealing properties to the coating film, but have a characteristic that flip-flop properties and brightness cannot be obtained. Examples of commercially available aluminum flake pigments include “Alpaste 6390NS” and “Alpaste 5680NS” manufactured by Toyo Aluminum Co., Ltd.

  The mass ratio (A / B) of the aluminum flake pigment (A) and the aluminum flake pigment (B) is 10/90 to 90/10, preferably 10/90 to 80/20, more preferably 10 / 90 to 70/30. When (A / B) is smaller than 10/90, the brightness is insufficient and the metallic luster is poor. When (A / B) is larger than 90/10, the concealability is insufficient and the substrate is easily affected by the substrate, and a stable silver color cannot be obtained.

The mass ratio ((A + B) / C) of the aluminum flake pigment (A) and the aluminum flake pigment (B) plus the aluminum flake pigment (C) is 90/10 to 30/70, preferably Is 90/10 to 40/60, more preferably 90/10 to 50/50. When ((A + B) / C) is larger than 90/10, the concealability is insufficient and the substrate is easily affected by the substrate, and a stable silver color cannot be obtained. When this is smaller than 30/70, the luminance is insufficient and the flip-flop property is insufficient.
Furthermore, the total amount of aluminum flake pigments (A), (B), and (C) is 5 to 50 parts by mass, preferably 5 to 40 parts by mass, more preferably 100 parts by mass of the resin solid content. 5 to 30 parts by mass. When the total amount of the aluminum flake pigments (A), (B), and (C) is less than 5 parts by mass, the concealability is insufficient, and when it exceeds 50 parts by mass, the appearance is deteriorated.

In the present invention, a mica pigment can be used as necessary. The shape and type of the mica pigment are not particularly limited, and examples thereof include white mica pigment, interference mica pigment, and colored mica pigment. Mica pigments in which the surface of mica powder is coated with metal oxides such as TiO ₂ , SnO ₂ , ZrO ₂ , Fe ₂ O ₃ , ZnO ₂ , Cr ₂ O ₃ , CoO, V ₂ O ₅ , and their hydrates. Can be suitably used because it is excellent in glitter and pearl. As a commercial product of white mica pigment, for example, “Iriodin 103WNT” manufactured by Merck Japan Co., Ltd., and as a commercial product of interference mica pigment, for example, “Iriodin 225WNT” manufactured by Merck Japan Co., Ltd. Examples of the commercially available products include “Iriodin 504WII” and “Iriodin New GP Blue Green WNT” manufactured by Merck Japan Co., Ltd.

  In the method of the present invention, the method for applying the metallic base coat paint is not particularly limited, and for example, it can be applied by air spray coating, airless spray coating, low-pressure atomizing spray coating (HVLP), electrostatic coating, or the like. Although there is no restriction | limiting in particular in the thickness of a coating film, It is preferable that the cured coating film thickness is 5-20 micrometers.

  The clear coating used in the method of the present invention is a coating that forms a colorless transparent or colored transparent coating film. By sequentially applying the metallic base coat paint and the clear paint by wet on wet, the design properties, finished appearance, weather resistance, chemical resistance, water resistance, moisture resistance and the like of the coating film can be further improved. There are no particular restrictions on the clear coating used, for example, acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, silicone-containing resins having crosslinkable functional groups such as hydroxyl groups, carboxyl groups, silanol groups, and epoxy groups. Thermosetting comprising a base resin and a crosslinking agent such as melamine resin, polyisocyanate compound or block polyisocyanate compound, epoxy resin or epoxy compound, carboxyl group-containing resin or compound, acid anhydride, alkoxysilane group-containing resin or compound The organic solvent type coating material which has a resin composition, a solvent, various additives, etc. as a component can be mentioned.

  In the method of the present invention, the clear coating method is not particularly limited, and for example, it can be applied by air spray coating, airless spray coating, electrostatic coating or the like. Although there is no restriction | limiting in particular also in the thickness of a coating film, It is preferable that cured coating film thickness is 10-50 micrometers.

  In the method of the present invention, the metallic base coat paint and the clear paint are sequentially applied by wet on wet. That is, if necessary, a metallic base coat paint is applied onto a substrate on which an undercoat film or an intermediate coat film has been formed, and a clear paint is applied before the metallic base coat paint is sufficiently dried. The paint and clear paint are cured and dried simultaneously. By applying wet-on-wet, energy can be saved, the coating process can be simplified, and the cost for forming the glitter coating can be reduced.

  After coating by wet-on-wet, it is possible to cure by crosslinking in the range from room temperature to 180 ° C. From room temperature to 100 ° C., the use of a two-component urethane paint is preferred, and at 100 ° C. to 180 ° C., for example, the use of a one-pack type acrylic melamine resin is preferred, but it is not particularly limited thereto.

When the material such as plastic having low heat resistance or the intermediate coating is a two-component urethane coating, the curing temperature is more preferably 70 to 120 ° C. In addition, when the material such as a metal having high heat resistance or the intermediate coating is a one-component melamine coating, the curing temperature is more preferably 120 to 160 ° C. The curing time varies depending on the curing temperature, and 10 to 50 minutes is appropriate at a curing temperature of 70 to 120 ° C, and 10 to 40 minutes is appropriate at a curing temperature of 120 to 160 ° C.
There is no particular limitation on the substrate on which the metallic coating film is formed by the method of the present invention, and for example, it can be applied to various substrates such as wood, metal, glass, cloth, plastic products, plastic foams, The present invention can be particularly suitably applied to a metal product capable of cationic electrodeposition. Examples of plastic products include molded products such as polypropylene, ABS, polyester, nylon, and the like. Specifically, automobile parts such as passenger cars, trucks, motorcycles, buses, personal computers, mobile phones, etc. An industrial product etc. can be mentioned. Examples of metal products that can be cationically electrodeposited include iron, copper, aluminum, tin, zinc, and the like, and alloys containing these metals. Specifically, such as passenger cars, trucks, motorcycles, buses, etc. Car bodies can be mentioned.

  In the method for forming a metallic coating film of the present invention, an undercoating film or an intermediate coating film can be formed on a substrate. As a method for forming the undercoat film, it is preferable to apply a cationic electrodeposition paint having excellent anticorrosive properties as the undercoat film after chemical conversion treatment with phosphate, chromate or the like on the metal substrate. In addition, an undercoating material can be applied to the plastic substrate as necessary. For example, it is preferable to apply a chlorinated polyolefin resin-based paint or the like to a low-polarity base material such as a polypropylene base material.

  In the method of the present invention, by forming an intermediate coating film on the substrate, the underlying defects are concealed, the surface smoothness after the top coating is secured, the appearance is improved, and the impact resistance and chipping resistance are increased. The coating film performance such as can be imparted. The intermediate coating used for forming the intermediate coating film can be composed of organic or inorganic color pigments, extender pigments, and the like, and a film-forming thermosetting resin, a solvent, a crosslinking agent, and the like.

There is no restriction | limiting in particular in the coating-film formation thermosetting resin used for intermediate coating, For example, an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, a urethane resin etc. can be mentioned. Moreover, as a crosslinking agent, a melamine resin, a polyisocyanate compound, a block polyisocyanate compound etc. can be mentioned, for example.
It is also possible to apply the metallic base coat paint in an uncured state after applying the intermediate paint on the base material that has been primed. In order to cure the intermediate coating, it is preferable to heat to a curing temperature of 60 to 180 ° C. If the curing temperature is less than 60 ° C, curing may not proceed sufficiently. When the curing temperature exceeds 180 ° C., the coating film may be yellowed or the physical properties of the coating film may be deteriorated such that the coating film becomes hard and brittle. When the material such as plastic with low heat resistance or the intermediate coating is a two-component urethane paint, it can be cured from room temperature to 180 ° C., but the curing temperature should be 70 to 120 ° C. More preferred. In addition, when the material such as a metal having high heat resistance or the intermediate coating is a one-component melamine coating, the curing temperature is more preferably 120 to 160 ° C. The curing time varies depending on the curing temperature, 10 to 50 minutes is appropriate at a curing temperature of 70 to 120 ° C, and 10 to 40 minutes is appropriate at a curing temperature of 120 to 160 ° C.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

In Examples and Comparative Examples, evaluation was performed by the following method.
(1) Luminance sensation Visually evaluate the degree of appearance of a high-glossy metallic luster design from the highlight position of the test plate.
3- The above design was clearly expressed.
2- The above design was almost developed.
1- The design is not sufficiently developed.
(2) Flip-flop property The degree of high change is visually evaluated from the highlight and shade positions of the test plate.
3- Expressed a clear change.
2- The change was almost expressed.
1—Insufficient expression of change.
(3) Concealment property Using a tin plate as a base material, a concealment rate test paper conforming to JIS K5600-4-1 4.1.2 Method B (Concealment rate test paper) is placed, and the base coat paint is continuously sprayed. After coating and baking so as to change the film thickness, the film thickness of the tin plate at the same site where the transparency of the white background and the black background of the concealment rate test paper was not known was measured to obtain the concealment film thickness. For the film thickness measurement, Deltascope MP30 manufactured by Fisher Instruments Co., Ltd. was used. The concealing film thickness is 20 μm or less, and is considered to meet the object of the present invention. The thinner the concealing film thickness, the better the concealing property, and the smaller the amount of metallic paint used.
(4) Appearance of coating film 3-No problem.
2- No problem in practical use.
1- Inhalation or ticking is easily seen.

Example 1
Acrylic resin “LB-9020” (manufactured by NOF BASF Coatings Co., Ltd., heating residue 55% by mass, hydroxyl value 56 mgKOH / g) 37.12 parts by mass, rheology control agent “LC-0988” (NOF fat BASF coating Made by Su Co., Ltd., inorganic, heating residue 10% by mass) To 5.83 parts by mass, as aluminum flake pigment (A), Toyo Aluminum Co., Ltd. “Alpaste TCR3040” (heating residue 80% by mass, Average particle diameter D ₅₀ 17 μm, average thickness 0.8 μm) 1.17 parts by mass, aluminum flake pigment (B), “SAP 550N” manufactured by Showa Aluminum Powder Co., Ltd. (heating residue 65% by mass, average particle diameter D ₅₀ 21.1 μm, average thickness 0.24 μm) 5.74 parts by mass, aluminum flake pigment (C), Toyo Aluminum Ltd. "Alpaste 6390NS" (heating residue 67% by weight, an average particle diameter _{D 50} 8 [mu] m, an average thickness of 0.18 .mu.m) 1.74 parts by weight, and melamine resin "U-VAN 122" (Mitsui Chemicals, Inc. Butylated melamine resin, heated residue 60% by mass) 14.58 parts by mass, surface modifier “Modaflow” (manufactured by Monsanto Co., Ltd., acrylic copolymer, heated residue 100% by mass) 0.2 parts by mass, 10 parts by mass of xylene and 23.61 parts by mass of butyl acetate were added, and the mixture was stirred and homogenized with a disper for 10 minutes to prepare a metallic base coat paint.

Next, on a tin plate degreased with isopropyl alcohol, a polyester one-component melamine paint “HIEIPICO No.500 intermediate coat” (manufactured by NOF BASF Coatings Co., Ltd.) is used as an intermediate coat. Air spray coating was carried out to set, and after setting for 10 minutes, it was cured by heating at 140 ° C. for 20 minutes to prepare an intermediate coating plate.
On this intermediate coating plate, diluted thinner (butyl acetate / xylene = 70/30 (mass ratio) so that the viscosity of the paint is 12 seconds at “Ford Cup # 4” (25 ° C.) with respect to the above metallic base coat paint. )), The diluted paint whose viscosity was adjusted was wet-on-wet and air-sprayed to a dry coating thickness of 20 μm and flashed off for 1 minute. In addition, an acrylic one-component melamine paint "Bellcoat No6200 Clear" (manufactured by NOF BASF Coatings Co., Ltd.) as a clear paint is wet-on-wet and air spray painted so that the dry film thickness is 30 μm. went. Then, after leaving it indoors for 10 minutes, it heat-dried at 140 degreeC for 20 minutes, and produced the test plate. The coating film was evaluated after 24 hours, and the evaluation results are shown in Table 1.

(Examples 2 to 13)
In the same manner as in Example 1, metallic base coats were prepared with the coating compositions shown in Tables 1 and 2, and test plates were prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

(Example 14)
Acrylic resin “LB-9020” (manufactured by NOF BASF Coatings Co., Ltd., heating residue 55% by mass, hydroxyl value 56 mgKOH / g) 44.52 parts by mass, rheology control agent “LC-0988” (NOF fat BASF coating Sou Co., Ltd., inorganic, heating residue 10% by mass) 5.83 parts by mass, aluminum flake pigment (A), Toyo Aluminum Co., Ltd. “Alpaste TCR3040” (heating residue 80% by mass, average Particle size D ₅₀ 17 μm, average thickness 0.8 μm) 2.33 parts by mass, aluminum flake pigment (B), “SAP 550N” manufactured by Showa Aluminum Powder Co., Ltd. (residual residue 65% by mass, average particle size D ₅₀ (21.1 μm, average thickness 0.24 μm) 4.31 parts by mass, aluminum flake pigment (C), manufactured by Toyo Aluminum Co., Ltd. Paste 6390NS "(heating residue 67% by weight, an average particle diameter _{D 50} 8 [mu] m, an average thickness of 0.18 .mu.m) 1.74 parts by weight," Sumidur N75 as the polyisocyanate resin "(Sumitomo Bayer Urethane Co., polyisocyanate Resin, non-volatile content = 75%, isocyanate content = 16.5%), 6.24 parts by mass, surface modifier “Modaflow” (manufactured by Monsanto Co., Ltd., acrylic copolymer, heating residue 100% by mass) 0 2 parts by weight, 10 parts by weight of xylene and 24.83 parts by weight of butyl acetate were mixed and stirred uniformly with a disper for 2 minutes to prepare a metallic base coat paint.

  Next, on the intermediate coating plate prepared in the same manner as in Example 1, with respect to this metallic base coat paint, diluted thinner (ford cup # 4) (25 ° C.) so that the paint viscosity becomes 11 seconds. The diluted coating material whose viscosity was adjusted with butyl acetate / xylene = 70/30 (mass ratio) was wet-on-wet applied with air spray so that the dry coating thickness was 20 μm, and flashed off for 1 minute. Furthermore, as a clear paint, a two-component polyurethane paint “High Urethane No. 6500 Clear” (manufactured by NOF BASF Coatings Co., Ltd.) is wet-on-wet and air-sprayed to a dry coating thickness of 30 μm. A test plate was prepared. The coating film was evaluated after being left indoors for 3 days, and the evaluation results are shown in Table 2.

(Comparative Examples 1 to 6)
In the same manner as in Example 1, a metallic base coat was prepared with the coating composition shown in Table 3, and a test plate was prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3.

In Tables 1 to 3, the subscripts indicate the following.
1): Trade name, manufactured by Toyo Aluminum Co., Ltd., 80% by weight of heating residue, average particle size D ₅₀ 17 μm,
Average thickness 0.80μm
2): Product name, manufactured by Toyo Aluminum Co., Ltd., heating residue 70% by mass, average particle size D ₅₀ 21 μm,
Average thickness 1.00μm
3): Trade name, manufactured by Toyo Aluminum Co., Ltd., 75% by weight of heating residue, average particle size D ₅₀ 28 μm,
Average thickness 1.00μm
4): Trade name, manufactured by Showa Aluminum Powder Co., Ltd., heating residue 65 mass%, average particle diameter D ₅₀ 21.1 μm, average thickness 0.24 μm
5): Product name, manufactured by Toyo Aluminum Co., Ltd., heating residue 67% by mass, average particle size D ₅₀ 8 μm
Average thickness 0.18μm

In Examples 1-5, the case where the ratio of the aluminum pigment (A) and the aluminum pigment (B) was changed was shown. In all cases, a coating film excellent in brightness, flip-flop property, coating film appearance property and hiding property (20 μm or less) is obtained. In particular, the characteristics in Examples 1, 2, and 3 were the best.
In Examples 6-8, the case where the ratio of the aluminum pigment (C) to the aluminum pigment (A) and the aluminum pigment (B) was changed was shown. When the aluminum pigment (C) was increased, the brightness and flip-flop properties were slightly lowered, but it was at a level causing no practical problems. In addition, Example 6 had the best characteristics, and then Example 7 had the next best characteristics. In Example 8, the brightness and slip flop properties are slightly inferior.

In Examples 9 to 11, the ratio of the resin solid content to the aluminum pigment (A), the aluminum pigment (B), and the aluminum pigment (C) was changed. In this case, when the aluminum pigment (A + B + C) was increased with respect to the resin solid content, the appearance was slightly lowered, but it was a level with no practical problem. In Example 11, the coating film appearance was slightly deteriorated.
Examples 12 and 13 are cases where the average particle diameter D ₅₀ and the average thickness of the aluminum pigment (A) were changed. When the average particle diameter D ₅₀ is increased, but hiding film thickness increases, no problem will 20μm or less.
Example 14 is a case where the paint type is changed to an acrylic urethane paint. Also in this case, a coating film excellent in brightness, flip-flop property, coating film appearance property, and concealing property (20 μm or less) is obtained.

However, in Comparative Example 1 in which the amount of aluminum pigment (B) is large due to the ratio of aluminum pigment (A) to aluminum pigment (B), the glitter and flip-flop properties are insufficient, and Comparative Example 2 in which there are many aluminum pigments (A). Then, the masking film thickness becomes 28 μm, and the masking film thickness exceeds 20 μm and becomes insufficient.
In Comparative Examples 3 and 4, the ratio of the aluminum pigment (C) to the aluminum pigment (A) and the aluminum pigment (B) is changed. In Comparative Example 3 with a small amount of aluminum pigment (C), the masking film thickness becomes 26 μm, and the masking film thickness exceeds 20 μm and becomes insufficient. On the contrary, in the comparative example 4 where there are many aluminum pigments (C), the concealing property and the flip-flop property are insufficient.
Further, Comparative Examples 5 and 6 are cases in which the ratio of the resin solid content to the aluminum pigment (A), the aluminum pigment (B), and the aluminum pigment (C) is changed. When the aluminum pigment (A + B + C) decreases with respect to the resin solid content, as shown in Comparative Example 5, the concealing property is remarkably reduced, and the brightness and flip-flop properties are also affected by the influence of the substrate. On the other hand, when the aluminum pigment (A + B + C) increases with respect to the resin solid content, the coating film appearance deteriorates.

As described above, according to the present invention, a metallic base coating composition is formed by wet-on-wet two-coat one-bake coating so that a metallic coating appearance excellent in all of glitter, flip-flop properties, and concealment properties can be obtained with high productivity and low cost. Can be obtained by the method.

Claims (3)

(A) an average particle diameter _{D 50} of more than 13 .mu.m, 25 [mu] m or less, an average thickness of 0.5μm or more, 1. Aluminum flake pigment of 5 μm or less,
(B) An average particle diameter D ₅₀ of 13 μm or more, 25 μm or less, an average thickness of 0.01 μm or more (excluding 0.08 μm or less ) , an aluminum flake pigment of less than 0.5 μm, and (C) an average particle diameter D ₅₀ contains 4 μm or more and less than 13 μm, an aluminum flake pigment having an average thickness of 0.01 μm or more (excluding 0.08 μm or less) and 0.5 μm or less,
In the solid content mass ratio of the aluminum flake pigment, A / B is 10/90 to 90/10, (A + B) / C is 90/10 to 30/70, and (A + B + C) with respect to 100 mass parts of resin solid content. ) Is 5 to 50 parts by mass in solid content, a metallic paint composition.   After applying the metallic paint composition according to claim 1, a clear paint is applied on the metallic paint composition by a wet-on-wet method, and the metallic paint composition and the clear paint are cured, Coating film forming method. A coating film obtained by the method according to claim 2.