JP2004275971A - Method for forming double layer coating film, double layer coating film and article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a double layer coating film capable of forming an inter coating film which is uniformly mixed with a white coating material and a black coating material and has a uniform spectra reflectance, and an article having the double layer coating film. <P>SOLUTION: In the method for forming the double layer coating film by successively forming the inter coating film, a base coating film and a clear coating film on a substrate formed with a primer coating film, the method for forming the double layer coating film comprises the formation of the inter coating film by using an inter coating apparatus in which white a coating material supply means supplying the white coating material in a variable supply amount and a black coating material supply means supplying the black coating material in a variable supply amount are provided, and the white coating material supply means and the black coating material supply means are independently from each other connected to a rotary atomizing type coating gun, wherein the white coating material and the black coating material have pigment concentrations (PWC) of 2 to 60 mass%, non volatile contents of 35 to 60 mass%, and coating material viscosities of 0.03 to 0.3 Pa s. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１１２】
【表２】

【０１１３】
実施例では、Ｎ−１〜Ｎ−９の各色を有し、塗膜均一性に優れた中塗り塗膜を得ることができた。これにより、任意のセットグレー中塗り塗装を行うことが明らかとなった。また、中塗り塗膜とベース塗膜との分光反射率の差が小さい塗膜を得ることができることも明らかとなり、実施例の複層塗膜形成方法によると外観等の優れた複層塗膜を得ることができた。一方、白色系塗料及び黒色系塗料の塗料粘度差が０．０３Ｐａ・ｓより大きい場合（比較例１、２）、それぞれの塗料粘度が０．０３Ｐａ・ｓ未満、０．３Ｐａ・ｓを超える場合（比較例３〜４）には、塗膜均一性に劣る中塗り塗膜が得られる結果となった。
【０１１４】
【発明の効果】
本発明の複層塗膜形成方法は、上述の構成よりなるので、白色系塗料及び黒色系塗料が均一に混合され、均一な分光反射率を有する中塗り塗膜を形成することができるものである。従って、自動車及び部品等に好適に適用することができる。
【図面の簡単な説明】
【図１】本発明における中塗り塗装装置の全体構成を示す概略図である。
【図２】本発明における回転霧化式塗装ガンの縦断面図である。
【図３】実施例１の中塗り塗膜の分光反射率スペクトルを示す図である。
【図４】実施例２の中塗り塗膜の分光反射率スペクトルを示す図である。
【図５】実施例３の中塗り塗膜の分光反射率スペクトルを示す図である。
【図６】実施例４の中塗り塗膜の分光反射率スペクトルを示す図である。
【図７】実施例５の中塗り塗膜の分光反射率スペクトルを示す図である。
【図８】実施例６の中塗り塗膜の分光反射率スペクトルを示す図である。
【図９】実施例７の中塗り塗膜の分光反射率スペクトルを示す図である。
【図１０】実施例８の中塗り塗膜の分光反射率スペクトルを示す図である。
【図１１】比較例１の中塗り塗膜の分光反射率スペクトルを示す図である。
【図１２】比較例２の中塗り塗膜の分光反射率スペクトルを示す図である。
【図１３】比較例３の中塗り塗膜の分光反射率スペクトルを示す図である。
【図１４】比較例４の中塗り塗膜の分光反射率スペクトルを示す図である。
【符号の説明】
１ 白色系塗料供給手段
２ 黒色系塗料供給手段
３ 回転霧化式塗装ガン
４、７ 貯留タンク
５、８ 管路
６、９ 容量可変ポンプ
１１ ガン本体
１２ エアモータ
１３ ケーシング
１４ スリーブ
１５ 回転軸
１６ 流出孔
１７ ディスク板
１８ カップ
１９ ねじ部材
２０ 白色系塗料供給路
２１、２３ 塗料噴出ノズル
２２ 黒色系塗料供給路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a multilayer coating, a multilayer coating, and an article.
[0002]
[Prior art]
In the coating of automobile bodies and parts, it is required that the intermediate paint color be concealed by the finish color as much as possible, and the intermediate paint color must have a spectral reflectance close to the spectral reflectance of the finish color. And may be. In addition, in the coating line for automobile bodies and parts, it is necessary to sequentially apply intermediate coatings on vehicle bodies and parts having different finish colors. Therefore, in order to perform the intermediate coating as described above, the spectral reflectance of the intermediate coating paint is required. Must be adjusted sequentially.
[0003]
For this reason, an apparatus has been proposed in which an intermediate coating of a desired spectral reflectance is performed by arbitrarily changing the mixing ratio of a white paint and a black paint (for example, see Patent Document 1).
[0004]
However, in the apparatus disclosed herein, the white paint and the black paint are mixed and then supplied to the coating gun. For this reason, when the mixture ratio of the white paint and the black paint is changed, since the mixed paint before the change of the mixture ratio remains before the coating gun, it is necessary to dispose and wash the remaining mixed paint, A complicated operation is required when changing the spectral reflectance.
[0005]
An intermediate coating device that has a rotary atomizing paint gun that enables mixing and atomization of white paint and black paint, and that is connected to the paint gun independently of white paint and black paint. Is disclosed (for example, refer to Patent Document 2). This is an apparatus in which the white paint supply means and the black paint supply means are separately supplied to the coating gun, so that there is no need to dispose of residual paint and to clean pipes and the like when the paint mixture ratio changes. Things.
[0006]
However, even when the intermediate coating is performed using this intermediate coating device, depending on the white paint and the black paint to be used, the white paint and the black paint are uniformly dispersed in the cup of the rotary atomizing coating device. Because they are not mixed, an intermediate coating film having a uniform spectral reflectance may not be obtained.
[0007]
[Patent Document 1]
JP-A-2000-135559 (page 2)
[Patent Document 2]
JP-A-10-277436 (page 2)
[0008]
[Problems to be solved by the invention]
In view of the above situation, the present invention provides a method for forming a multi-layer coating film in which a white coating and a black coating are uniformly mixed to form an intermediate coating film having a uniform spectral reflectance. The purpose of the present invention is to provide an article having:
[0009]
[Means for Solving the Problems]
The present invention is a method for forming a multilayer coating film in which an intermediate coating film, a base coating film, and a clear coating film are sequentially formed on a substrate on which an undercoat coating film has been formed. A white paint supply means for supplying a variable amount of white paint and a black paint supply means for supplying a black paint with a variable supply amount, wherein the white paint supply means and the black paint supply means Are formed independently using an intermediate coating apparatus connected to a rotary atomizing type coating gun, wherein the white paint and the black paint have a pigment concentration (PWC) of 2 to 60 mass%. %, The nonvolatile content is 35 to 60% by mass, and the paint viscosity is 0.03 to 0.3 Pa · s. The difference in the paint viscosity between the white paint and the black paint is 0.03 Pa · s or less. And mixing the white paint and the black paint The intermediate coating composition has a pigment concentration (PWC) of 2 to 60% by mass, a non-volatile content of 35 to 60% by mass, and a coating viscosity of 0.03 to 0.3 Pa · s. It is a forming method.
[0010]
The intermediate coating film is preferably a gray or white intermediate coating film.
The spectral reflectance in the reflection region within the wavelength range of 300 to 700 nm of the intermediate coating film is within ± 15% of the spectral reflectance of the base coating film in the reflection region within the wavelength range of 300 to 700 nm. Is preferred.
[0011]
The base coating and the clear coating are preferably coatings formed by applying a glitter-containing base coating and a clear coating by a wet-on-wet method and simultaneously curing the coatings.
[0012]
The present invention is a multilayer coating film formed by the above multilayer coating film forming method.
The present invention is also an article having the multilayer coating film.
Hereinafter, the present invention will be described in detail.
[0013]
In the method for forming a multilayer coating film of the present invention, an intermediate coating film, a base coating film, and a clear coating film are sequentially formed on a substrate on which an undercoat coating film has been formed. This makes it possible to form a suitable multi-layer coating film composed of an undercoating film, an intermediate coating film, a base coating film, and a clear coating film on a substrate such as an automobile body and parts.
[0014]
In the method for forming a multilayer coating film of the present invention, the intermediate coating film is a white paint supply means for supplying a white paint with a variable supply amount and a black paint for supplying a black paint with a variable supply amount. A paint supply means is provided, and the white paint supply means and the black paint supply means are formed independently of each other using an intermediate coating apparatus connected to a rotary atomizing paint gun. Using the above-mentioned intermediate coating apparatus, and by using a white paint and a black paint in which the pigment concentration, the nonvolatile content, and the paint viscosity are specified in a specific range, a white paint and a white paint in the cup of the intermediate coating apparatus are used. The black paint can be uniformly mixed, and as a result, an intermediate coating film having a uniform spectral reflectance can be formed. In addition, by using the above-mentioned intermediate coating apparatus, it is not necessary to dispose of unnecessary paint due to a change in the mixing ratio and to wash the shunts and the like, so that the intermediate coating film can be formed more efficiently.
[0015]
The intermediate coating apparatus includes a white paint supply unit that supplies a white paint with a variable supply amount and a black paint supply unit that supplies a black paint with a variable supply amount. Are separately and independently connected to a rotary atomizing type coating gun.
[0016]
Hereinafter, an example of the intermediate coating apparatus will be described with reference to FIGS.
FIG. 1 is a schematic view showing the entire configuration of the intermediate coating apparatus, and FIG. 2 is a longitudinal sectional view of a rotary atomizing type coating gun.
[0017]
In FIG. 1, the intermediate coating apparatus includes a white paint supply unit 1 that supplies a white paint with a variable supply amount, a black paint supply unit 2 that supplies a black paint with a variable supply amount, A rotary atomizing type coating gun 3 that enables mixing and atomization of paint is provided.
[0018]
The white paint supply means 1 includes a storage tank 4 storing white paint, and a variable capacity pump 6 interposed in the middle of a pipe 5 connected to the storage tank 4. The paint supply means 2 comprises a storage tank 7 for storing a black paint and a variable capacity pump 9 interposed in a pipe 8 connected to the storage tank 7.
[0019]
The pipeline 5 of the white paint supply means 1 and the pipeline 8 of the black paint supply means 2 are connected to the rotary atomizing coating gun 3 independently of each other. The system paint is supplied to the rotary atomizing type coating gun 3 with the supply amount being variable.
[0020]
In FIG. 2, a casing 13 of an air motor 12 is screwed to a tip of a gun body 11 of the rotary atomizing type coating gun 3. The air motor 12 includes a rotating shaft 15 rotatably supported by a sleeve 14 pressed into a casing 13.
[0021]
A cup 18 having a disk plate 17 having a plurality of outflow holes 16 on its outer periphery is fixed to a tip end portion of the rotation shaft 15 of the air motor 12 with a screw member 19. A paint jet nozzle 21 connected to the supplied white paint supply path 20 and a paint jet nozzle 23 connected to the black paint supply path 22 provided in the casing 13 are provided.
[0022]
According to such a rotary atomizing type coating gun 3, the cup 18 is driven to rotate in accordance with the rotation of the air motor 12, and the paint supplied into the cup 18 from the paint ejection nozzles 21 and 23 is subjected to centrifugal force. The mixing is performed while moving forward along the inner surface, and reaches the leading edge of the cup 18 through the outflow hole 16 having the disk plate 17. The paint that has reached the leading edge of the cup 18 is formed into a predetermined pattern by shaving air, and is sprayed on an object (not shown).
[0023]
Therefore, by the rotation of the cup 18, that is, the rotation of the air motor 12, the white paint ejected from the paint ejection nozzle 21 and the black paint ejected from the paint ejection nozzle 23 are mixed in the cup 18. Therefore, unless mixing in this portion is efficient, an intermediate coating film having a uniform spectral reflectance cannot be formed.
[0024]
As the intermediate coating apparatus, it is preferable that the white paint supply means and the black paint supply means are connected to a rotary atomizing paint gun independently of each other, for example, described in JP-A-10-277436. Intermediate coating apparatus or the like can be used.
[0025]
In the method for forming a multilayer coating film according to the present invention, the intermediate coating film is formed by the intermediate coating device using an intermediate coating material obtained by mixing a white paint and a black paint. By forming using the intermediate coating in the present invention, when a base coating is further formed, the intermediate coating color of the intermediate coating is concealed, and the difference in spectral reflectance with the base coating is relatively small. The intermediate coating film can be formed uniformly and efficiently.
[0026]
The white paint, the black paint and the intermediate paint obtained by mixing these paints according to the present invention each have a specific pigment concentration, nonvolatile content, and paint viscosity. An intermediate coating having uniform spectral reflectance can be formed by performing intermediate coating with the intermediate coating apparatus using a coating material having such physical properties. For example, using a white paint and a black paint having a pigment concentration out of the range specified in the present invention, a nonvolatile content or a paint viscosity, and performing the intermediate coating with the above-mentioned intermediate coating apparatus, the white paint It becomes difficult to mix the black paint and the black paint uniformly in the cup of the apparatus, and an intermediate paint that is not uniformly mixed is prepared, and as a result, an intermediate paint film having non-uniform spectral reflectance and the like. May be formed. On the other hand, when using a white paint and a black paint having a specific pigment concentration, a nonvolatile content and a paint viscosity in the present invention and applying the above-mentioned intermediate coating apparatus, the white paint and the black paint are used. Because of the uniform mixing in the cup of the apparatus, an intermediate coating having the physical properties defined in the present invention is prepared. For this reason, in the present invention, an intermediate coating film having a uniform spectral reflectance can be formed.
[0027]
In the white paint and the black paint, the pigment concentration [PWC = total pigment mass / (total pigment mass + total resin solid mass)] has a lower limit of 2% by mass and an upper limit of 60% by mass. If the amount is less than 2% by mass, the concealing property may be reduced due to insufficient pigment. If it exceeds 60% by mass, it becomes difficult to mix the white paint and the black paint uniformly, so that an intermediate coating film having a uniform spectral reflectance cannot be formed. The lower limit is preferably 5% by mass, and the upper limit is preferably 50% by mass.
[0028]
The white paint and the black paint have a nonvolatile content of a lower limit of 35% by mass and an upper limit of 60% by mass. When the amount is less than 35% by mass, the amount of the solvent is too large, so that a high-solids intermediate coating cannot be obtained, and the volume shrinkage increases, so that the finished appearance of the coating film may be inferior. If it exceeds 60% by mass, it becomes difficult to mix the white paint and the black paint uniformly, so that an intermediate coating film having a uniform spectral reflectance cannot be formed. The lower limit is preferably 40% by mass, and the upper limit is preferably 55% by mass.
[0029]
Each of the white paint and the black paint has a paint viscosity of a lower limit of 0.03 Pa · s and an upper limit of 0.3 Pa · s (a lower limit of 15 seconds and an upper limit of 55 seconds in a paint viscosity of No. 4 Ford Cup). If it is less than 0.03 Pa · s, the appearance of the coating film may be poor or the basic performance of the coating film may not be maintained. If it exceeds 0.3 Pa · s, it becomes difficult for the white paint and the black paint to be uniformly mixed in the cup, so that an intermediate coating film having a uniform spectral reflectance cannot be formed. In the present invention, the paint viscosity means a value measured as a dynamic viscoelastic modulus with respect to a sinusoidal stress, and can be measured, for example, using a rhesol G-3000 manufactured by UBM. The paint viscosity in the present invention is the paint viscosity. The lower limit is more preferably 0.05 Pa · s (20 seconds with a No. 4 Ford Cup), and even more preferably 0.07 Pa · s (25 seconds with a No. 4 Ford Cup). The upper limit is more preferably 0.2 Pa · s (50 seconds with a No. 4 Ford Cup), and even more preferably 0.17 Pa · s (45 seconds with a No. 4 Ford Cup).
[0030]
In the method for forming a multilayer coating film of the present invention, the difference between the above-mentioned white paint and the above-mentioned black paint is 0.03 Pa · s or less (15 sec or less as a paint viscosity using a No. 4 Ford cup). . Thereby, in the intermediate coating apparatus, an intermediate coating in which the white paint and the black paint are uniformly mixed in the cup is prepared, and as a result, an intermediate coating having uniform spectral reflectance is prepared. Can be formed. It is preferably at most 0.02 Pa · s, more preferably at most 0.01 Pa · s.
[0031]
In the intermediate coating, the pigment concentration [PWC = total pigment mass / (total pigment mass + total resin solid mass)] has a lower limit of 2% by mass and an upper limit of 60% by mass. If the amount is less than 2% by mass, the concealing property may be reduced due to insufficient pigment. If it exceeds 60% by mass, it becomes difficult for the white paint and the black paint to be uniformly mixed in the cup, so that an intermediate coat having a uniform spectral reflectance cannot be formed. The lower limit is preferably 5% by mass, and the upper limit is preferably 50% by mass.
[0032]
The lower coating has a lower limit of 35% by mass and an upper limit of 60% by mass. When the amount is less than 35% by mass, the amount of the solvent is too large, so that a high-solids intermediate coating cannot be obtained, and the volume shrinkage increases, so that the finished appearance of the coating film may be inferior. If it exceeds 60% by mass, it becomes difficult for the white paint and the black paint to be uniformly mixed in the cup, so that an intermediate coat having a uniform spectral reflectance cannot be formed. The lower limit is preferably 40% by mass, and the upper limit is preferably 55% by mass.
[0033]
The intermediate coating composition has a coating viscosity of 0.03 Pa · s as a lower limit and 0.3 Pa · s as an upper limit (a lower limit of 15 seconds and an upper limit of 55 seconds in a No. 4 Ford cup paint viscosity). If it is less than 0.03 Pa · s, the appearance of the coating film may be poor or the basic performance of the coating film may not be maintained. If it exceeds 0.3 Pa · s, it becomes difficult for the white paint and the black paint to be uniformly mixed in the cup, so that an intermediate coating film having a uniform spectral reflectance cannot be formed. The lower limit is more preferably 0.05 Pa · s (20 seconds with a No. 4 Ford Cup), and even more preferably 0.07 Pa · s (25 seconds with a No. 4 Ford Cup). The upper limit is more preferably 0.2 Pa · s (50 seconds with a No. 4 Ford Cup), and even more preferably 0.17 Pa · s (45 seconds with a No. 4 Ford Cup). The pigment concentration, the nonvolatile content, and the paint viscosity of the intermediate coating are the pigment concentration, the nonvolatile content, and the paint viscosity of the paint obtained by mixing the white paint and the black paint, respectively.
[0034]
The white paint and the black paint are not particularly limited, and conventionally known paints can be used.For example, a standard intermediate paint containing carbon black or titanium dioxide as a main pigment can be used. it can. The white paint and the black paint may further contain a color pigment and an extender pigment.
[0035]
The film-forming resin contained in the white paint and the black paint is not particularly limited, and examples thereof include an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a urethane resin.
[0036]
When the film-forming resin contained in the white paint and the black paint has a carboxylic acid group, the acid value preferably has a lower limit of 10 and an upper limit of 100. If it is less than 10, the adhesiveness of the coating film is poor and curing may be poor. If it exceeds 100, the hydrophilicity is too high and the water resistance of the coating film may be poor. The lower limit is more preferably 20 and the upper limit is more preferably 80.
[0037]
When the film-forming resin contained in the white paint and the black paint has a hydroxyl group, the hydroxyl value preferably has a lower limit of 30 and an upper limit of 150. If it is less than 30, curing failure may occur. If it exceeds 150, excessive hydroxyl groups may remain in the cured coating film, resulting in poor water resistance. The lower limit is more preferably 50, and the upper limit is more preferably 150.
[0038]
The film-forming resin contained in the white paint and the black paint preferably has a number average molecular weight obtained by gel permeation chromatography (GPC) of a lower limit of 1,000 and an upper limit of 10,000. If it is less than 1,000, physical properties such as solvent resistance of the cured coating film may be inferior, and if it exceeds 10,000, the viscosity of the resin solution is high, and it is difficult to handle the resulting resin in terms of emulsification and dispersion. Not only that, the appearance of the resulting coating film may be significantly reduced. The lower limit is more preferably 1500 and the upper limit is more preferably 7000.
[0039]
The method for producing the film-forming resin contained in the white paint and the black paint is not particularly limited, and can be appropriately selected depending on the type and properties of the intended film-forming resin. For example, conventionally known production methods such as a melt polymerization method, a transesterification method, an interfacial polymerization method, and a solution polymerization method can be used.
[0040]
As the curing agent contained in the white paint and the black paint, a curing agent known to those skilled in the art can be appropriately selected according to the type of the film-forming resin. Generally, from the viewpoint of pigment dispersibility and coating workability, the film-forming resin is a polyester resin and / or an acrylic resin having a hydroxyl group, and the curing agent is a polyisocyanate and / or a melamine resin. Is preferred. In addition, from the viewpoint of storage stability, the polyisocyanate may have an isocyanate group blocked by a blocking agent known to those skilled in the art, such as alcohols such as butyl cellosolve and 2-ethylhexanol and oximes such as methyl ethyl ketoxime. preferable.
[0041]
It is preferable that the solid content mass ratio of the film-forming resin and the curing agent in the white paint and the black paint is 85/15 to 50/50. If the above ratio exceeds 85/15, the curability may decrease, and if it is less than 50/50, various properties of the obtained coating film may decrease.
[0042]
The white paint and the black paint are, if necessary, in addition to the above components, an organic solvent, a curing catalyst, a surface conditioner, an antifoaming agent, a plasticizer, a film forming aid, an ultraviolet absorber, and an antioxidant. Etc. can be contained. These are not particularly limited, and those well known by those skilled in the art can be used.
[0043]
The method for obtaining the white paint and the black paint is not particularly limited. For example, a mixture of the film-forming resin, the curing agent, the pigment, and the like is kneaded using a kneader, a roll, or the like, and a sand grind mill. And can be obtained by using all methods well known to those skilled in the art, such as dispersing using a disperser or the like.
[0044]
In the method for forming a multilayer coating film of the present invention, the object to be coated is a substrate on which an undercoat coating film is formed. The undercoat film is formed by an electrodeposition paint. The electrodeposition paint for forming the undercoating film is not particularly limited, and may be either a cationic type or an anionic type, but is preferably a cationic type from the viewpoint of corrosion resistance and rust prevention.
[0045]
The substrate is not particularly limited, and examples thereof include iron, steel, aluminum, tin, zinc, and the like, and alloys and castings containing these metals. Specifically, there may be mentioned car bodies and parts such as passenger cars, trucks, motorcycles, and buses. These metals are preferably subjected to a surface treatment before the electrodeposition coating is performed.
[0046]
In the method for forming a multilayer coating film of the present invention, the intermediate coating film is formed on the base material on which the undercoat film is formed. The intermediate coating film is generally formed to conceal base defects, to secure surface smoothness after the top coating (improve appearance), and to impart physical properties of the coating film (such as impact resistance and chipping resistance). The intermediate coating film is formed by applying an intermediate coating material in which the white paint and the black paint are mixed using the intermediate coating device.
[0047]
The intermediate coating is usually applied so as to have a dry film thickness of 20 to 40 μm. If it is less than 20 μm, the concealment of the base may be insufficient, and if it is more than 40 μm, sagging at the time of coating, wrinkles at the time of heat curing, or the appearance of the obtained intermediate coating film may be reduced. is there.
[0048]
After the intermediate coating material is applied, it is cured by a predetermined heat to obtain an intermediate coating film. The conditions for the heat curing are not particularly limited, and are appropriately determined according to the type of the intermediate coating material. As the conditions for the heat curing, for example, the heating temperature is preferably lower limit 110 ° C. and upper limit 180 ° C., and the heating time is preferably lower limit 10 minutes and upper limit 60 minutes. The lower limit of the heating temperature is more preferably 120 ° C, and the upper limit is more preferably 160 ° C.
[0049]
In the method for forming a multilayer coating film of the present invention, the intermediate coating film is preferably a gray or white intermediate coating film. By forming such an intermediate coating film, a desired spectral reflectance can be adjusted.
[0050]
In the method for forming a multilayer coating film according to the present invention, the spectral reflectance of the intermediate coating film in the reflection region within the wavelength range of 300 to 700 nm is the spectral reflectance of the base coating film in the reflection region within the wavelength range of 300 to 700 nm. Preferably, it is within a range of ± 15% of the ratio. By setting so as to be within such a range, a difference in hue (color difference) of the coating film in a thin portion of the base coating film or the like can be reduced, and the coating film has a uniform appearance as a whole. It can be a multilayer coating film. In the present invention, by adjusting the mixing ratio of the white paint and the black paint, an intermediate coating film and a base coating film having a spectral reflectance in the above range can be formed.
[0051]
The spectral reflectance of the intermediate coating film and the base coating film in the present invention is a spectral reflectance in a reflection region within a wavelength range of 300 to 700 nm. That is, the average value of the reflectance in the reflection region within the wavelength range of 300 to 700 nm. For example, when the reflection region in the wavelength range of 300 to 700 nm of the intermediate coating film exists at a wavelength of 400 to 700 nm, the average value of the spectral reflectance of the intermediate coating film at a wavelength of 400 to 700 nm is obtained. Similarly, when the reflection region within the wavelength range of 300 to 700 nm of the base coating film exists at a wavelength of 600 to 700 nm, the average value of the spectral reflectance at a wavelength of 600 to 700 nm of the base coating film is obtained.
[0052]
For the reflection area of the coating film, for example, the target paint is applied on a JIS concealing rate test paper at a film thickness that is incompletely concealed, and the spectral reflectance curves on a white background and a black background are measured, and the same wavelength Can be defined as a region where the difference in reflectance at 1% is 1% or more. In the case of a gray or white intermediate coating film, a wavelength of 400 to 700 nm is generally a reflection region. In the case of a red-based coating, 650 to 700 nm, in the case of an orange-based coating, 600 to 700 nm, in the case of a yellow-based coating, 550 to 700 nm, and in the case of a blue-based coating, 400 to 500 nm. Each area is generally a reflection area.
[0053]
In the present invention, it is preferable that the spectral reflectance of the intermediate coating film thus determined falls within a range of ± 15% of the spectral reflectance of the base coating film. The method for measuring the spectral reflectance is not particularly limited, and for example, can be measured using a spectrophotometer. Specifically, it can be determined by measuring the spectral reflectance of the coating film using an integrating sphere. As a sample coating film for measuring the spectral reflectance, a coating film formed by coating on a base material so as to have a sufficient film thickness not to be affected by the base is used. More preferably, it is within the range of 10%. By setting so as to be within such a range, the difference in hue (color difference) of the coating film in a thin portion of the base coating film or the like can be further reduced, and a more uniform coating appearance as a whole Can be obtained.
[0054]
When the above-mentioned spectral reflectance is within the range of ± 15%, even when the thickness of the base coating film has a variation within the range of ± 30% or more of the average film thickness, the color difference is visually recognized. The coating film appearance can be made uniform to such an extent that it is not felt.
[0055]
According to the method for forming a multilayer coating film of the present invention, a base coating material is applied on the intermediate coating film formed as described above to form a base coating film. The base paint provides aesthetics and protection to the object to be coated.
[0056]
The base paint may be either a color base paint or a glitter-containing base paint. When applying the base paint, the intermediate coating film may be in a cured state or an uncured state.
[0057]
Examples of the color pigments contained in the base paint include, for example, organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, Examples thereof include quinacridone pigments, isoindolinone pigments, and metal complex pigments. Inorganic pigments include yellow salts, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. As the extender, calcium carbonate, barium sulfate, clay, talc and the like are used.
[0058]
Examples of the brilliant contained when the base paint is a brilliant-containing base paint include, for example, brilliant pigments such as mica powder, interference mica powder, white mica powder, alumina flake, graphite, and flaky color pigment, aluminum And a brilliant material made of a metal or alloy such as copper, zinc, iron, nickel, and tin. The shape of these glittering materials is not particularly limited, but is preferably, for example, scaly, and particularly preferably one having an average particle size of 2 to 50 μm and a thickness of 0.1 to 3 μm.
[0059]
The content of the brilliant material is not particularly limited. For example, the lower limit is preferably 0.1% by mass and the upper limit is preferably 20% by mass in PWC. If the amount is less than 0.1% by mass, the imparting of design properties by the glittering material may be insufficient. If it exceeds 20% by mass, the appearance of the coating film tends to decrease. The lower limit is more preferably 0.5% by mass, and the upper limit is more preferably 18% by mass.
[0060]
The film-forming resin used in the base paint is not particularly limited, and a general thermosetting resin is used. For example, a film such as an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a urethane resin is used. A forming resin is used. These are used in combination with a curing agent such as an amino resin and / or a blocked isocyanate resin. From the viewpoint of pigment dispersibility and workability, a combination of an acrylic resin and / or a polyester resin with an amino resin is preferable.
[0061]
The mass ratio of the film-forming resin to the curing agent (the film-forming resin / curing agent) in the base paint is preferably 90/10 to 10/90, more preferably 80/20 to 50 /. 50. If the amount of the curing agent is too small, the curability tends to decrease. If the amount is too large, the coating film may be hard and brittle.
[0062]
When the base paint is a color base paint, the application amount of the color base paint is not particularly limited, and it is preferable to apply the base paint such that the dry thickness of the base coat is 10 μm at a lower limit and 30 μm at an upper limit. The lower limit is more preferably 15 μm, and the upper limit is more preferably 25 μm.
[0063]
When the base paint is a glitter-containing base paint, the glitter-containing base paint preferably contains a viscosity controlling agent. The viscosity controlling agent is used for favorably forming a coating film without unevenness and sagging, and generally, a material exhibiting thixotropic properties can be used.
[0064]
The viscosity control agent is not particularly limited, and examples thereof include a swelling dispersion of an aliphatic amide, an amide-based fatty acid, a polyamide-based viscosity control agent such as a long-chain polyaminoamide phosphate, and a colloidal swelling dispersion of polyethylene oxide. And a polyethylene-based viscosity control agent.
[0065]
Other viscosity control agents include organic acid smetite clay, organic bentonite-based viscosity control agents such as montmorillonite, inorganic pigments such as aluminum silicate and barium sulfate, and flat pigments whose viscosity is expressed by the shape of the pigment. Can be. These viscosity control agents are preferably those which do not affect the gloss and the color development when formed into a coating film.
[0066]
Further, as a preferable viscosity control agent used in the present invention, non-crosslinked or crosslinked resin particles utilizing the interaction of polar groups can be exemplified. As the crosslinked resin particles, crosslinked resin particles which are insoluble in the organic solvent used in the coating composition and have an average particle size of 0.02 to 0.5 μm are preferable. If the average particle size is too large, the dispersion stability of the crosslinked resin particles may decrease. As such crosslinked resin particles, a resin having an emulsifying ability such as an alkyd resin or a polyester resin synthesized with a monomer having a zwitterionic group in the molecule as one of the polyhydric alcohol components, and a polymerization initiator; Those obtained by subjecting an ethylenically unsaturated monomer to emulsion polymerization in an aqueous medium in the presence of are preferred.
[0067]
The monomer having the zwitterionic group in the molecule includes -N⁺-R-COO⁻Or -N⁺-R-SO₃ ⁻And those having two or more hydroxyl groups. As such a monomer, a hydroxyl group-containing aminosulfonic acid-type zwitterionic compound is preferable for synthesizing a resin, and specific examples thereof include bishydroxyethyltaurine.
[0068]
The resin having an emulsifying zwitterionic group in the molecule synthesized using the above monomer preferably has an acid value of a lower limit of 30 mgKOH / g and an upper limit of 150 mgKOH / g. The lower limit of the value is more preferably 40 mgKOH / g. As the resin having a zwitterionic group having an emulsifying ability in a molecule, it is preferable to use a polyester resin having a number average molecular weight of 500 as a lower limit and 5000 as an upper limit. The lower limit of the number average molecular weight is more preferably 700, and the upper limit is more preferably 3000. When the acid value and the number average molecular weight are less than the lower limits, a resin having an emulsifying ability may be desorbed when a coating film is formed, or the solvent resistance may be reduced. If the acid value and the number average molecular weight exceed the upper limits, the handleability of the resin may be reduced.
[0069]
In the synthesis of the crosslinked resin particles, it is preferable that a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule is contained as the ethylenically unsaturated monomer to be emulsion-polymerized. Such a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule is preferably contained in the range of 0.1 to 10% by mass of all monomers. By including such a monomer, it is possible to impart sufficient cross-linking that does not dissolve in an organic solvent to the cross-linked resin particles to be synthesized.
[0070]
The crosslinked resin particles do not contain a low-molecular emulsifier and a protective colloid that deteriorate the performance of the coating film when formed, and are appropriately crosslinked. By blending in the coating composition, the water resistance, solvent resistance, gloss and the like of the coating film can be enhanced.
[0071]
The addition amount of the above-mentioned viscosity control agent is preferably 0.01 parts by mass as the lower limit and 5 parts by mass as the upper limit with respect to 100 parts by mass of the resin solid content of the coating composition. If the amount is less than 0.01 part by mass, the viscosity control effect cannot be obtained, and there is a possibility that the multilayer coating film may be used between the layers or may be inverted between the layers. If it exceeds 5 parts by mass, the appearance of the coating film may be deteriorated. The lower limit is more preferably 0.1 part by mass, and even more preferably 0.2 part by mass. The upper limit is more preferably 12 parts by mass, and even more preferably 9 parts by mass.
[0072]
In the brilliant-containing base paint, a curing catalyst, an ultraviolet absorber, an antioxidant, a surface conditioner, and the like can be used, if necessary, in addition to the above components.
[0073]
The thickness of the glittering material-containing base paint at the time of application is appropriately selected depending on the application of the multilayer coating film and the like, and is not particularly limited, but is generally 5 to 35 μm. If the thickness is less than 5 μm, if the film thickness is too thin, the base cannot be concealed and the film may be cut off. If it exceeds 35 μm, the sharpness of the coating film may be reduced, or defects such as unevenness and flow may occur during coating.
[0074]
In general, a solution type paint is preferably used as the above-mentioned brilliant material-containing base paint, and if it is a solution type, any of an organic solvent type, an aqueous type (water-soluble, water-dispersible, emulsion), and a non-aqueous type can be used. Can be preferably used.
[0075]
When the brilliant-containing base paint is an aqueous paint, a thermosetting film-forming resin specifically described in US Pat. Nos. 5,151,125 and 5,183,504 is used as a film-forming resin. Resin can be used. Particularly, a thermosetting film-forming resin obtained by combining an acrylamide group-containing hydroxyl resin and an acid group-containing melamine resin described in US Pat. No. 5,183,504 can be used favorably in terms of finish and appearance performance. .
[0076]
When the glittering material-containing base paint is an aqueous type paint, in order to obtain a good finished coating film, the glittering material-containing base coating film is previously heated at 60 to 100 ° C. for 2 to 10 minutes before applying the clear paint. It is desirable to keep.
[0077]
It is preferable that the glitter-containing base paint is applied by a coating method such as electrostatic coating or air spray. In order to suppress unevenness in glitter, it is preferable to apply the paint in two stages rather than in one stage.
[0078]
In the method for forming a multilayer coating film of the present invention, a clear coating is formed on the base coating film formed as described above to form a clear coating film. When using a brilliant-containing base paint containing a brilliant material as the base paint, it is formed to smooth the unevenness and shine of the base coating film caused by the brilliant material and also to protect the base coating film. is there.
[0079]
The film-forming resin of the clear paint used in the present invention is not particularly limited, and for example, a thermosetting film-forming resin can be used. For example, a film-forming resin such as an acrylic resin, a polyester resin, an epoxy resin, or a urethane resin can be used, and these are used in combination with a curing agent such as an amino resin and / or a blocked isocyanate resin. From the viewpoints of transparency and acid etching resistance, a combination of an acrylic resin and / or a polyester resin and an amino resin, or an acrylic resin and / or a polyester resin having a carboxylic acid / epoxy curing system can be used.
[0080]
At the time of preparation, the solid content in the clear paint is preferably 20% by mass as a lower limit and 60% by mass as an upper limit, more preferably 35% by mass as the lower limit, and 55% by mass as the upper limit. % Is more preferable. The solid content at the time of application is preferably 10% by mass as the lower limit and 50% by mass as the upper limit, and more preferably 20% by mass as the lower limit.
[0081]
The clear coating may be applied on a cured base coating film, or may be applied on an uncured base coating film by a wet-on-wet method. Above all, from the viewpoint of shortening the process, in the method for forming a multilayer coating film of the present invention, the base coating film and the clear coating film are obtained by applying a glitter-containing base coating material and a clear coating material by a wet-on-wet method and curing at the same time. It is preferable that the coating film is formed by the above. In the case of coating by a wet-on-wet method, it is preferable that the above-mentioned viscosity control agent is contained. As the viscosity control agent, the same viscosity control agent as described for the glitter material-containing base paint can be used.
[0082]
The amount of the viscosity control agent to be added to the clear coating is preferably 0.01 parts by weight and 10 parts by weight with respect to 100 parts by weight of the resin solid content of the coating composition. If the amount is less than 0.01 part by mass, the effect of controlling the viscosity cannot be obtained, so that adaptation or inversion may occur between the layers of the multilayer coating film. If it exceeds 10 parts by mass, the appearance of the coating film may decrease. The lower limit is more preferably 0.02 parts by mass, and still more preferably 0.03 parts by mass. The upper limit is more preferably 8 parts by mass, and still more preferably 6 parts by mass.
[0083]
The clear coating is preferably applied by a method such as electrostatic coating or air spray. Generally, the dry film thickness of the clear coating film preferably has a lower limit of 10 μm and an upper limit of 60 μm. If the film thickness is too thick, problems such as splashes and sagging may occur at the time of coating. If the film thickness is too thin, irregularities and the like on the base may not be concealed. The lower limit is more preferably 20 μm, and the upper limit is more preferably 50 μm.
[0084]
The coating form of the clear coating may be any of an organic solvent type, an aqueous type (water-soluble, water-dispersible, emulsion), a non-aqueous dispersion type, and a powder type. If necessary, a curing catalyst, a surface conditioner and the like may be contained.
[0085]
In the method for forming a multilayer coating film of the present invention, as described above, it is possible to form a multilayer coating film by simultaneously heating and curing the formed uncured base coating film and the uncured clear coating film. it can.
[0086]
The temperature for the heat curing is preferably a lower limit of 110 ° C. and an upper limit of 180 ° C. Thereby, a cured coating film having a high degree of crosslinking can be obtained. If the temperature is lower than 110 ° C., the curing will be insufficient, and if it exceeds 180 ° C., the resulting coating film may be hard and brittle. The lower limit is more preferably 120 ° C., and the upper limit is more preferably 160 ° C. The time for heating and curing can be appropriately set according to the above temperature. When the temperature is 120 to 160 ° C., the time is, for example, 10 to 60 minutes.
[0087]
After the base coating film is cured, a clear paint may be applied to cure the uncured clear coating film.
[0088]
The dry film thickness of the multilayer coating film formed by the multilayer coating film forming method of the present invention is usually preferably lower limit 30 μm and upper limit 300 μm. If the thickness is less than 30 μm, the film strength of the obtained multilayer coating film may decrease. If the thickness exceeds 300 μm, the physical properties of the film may deteriorate or the performance of the coating film may be impaired. The lower limit is more preferably 50 μm, and the upper limit is more preferably 250 μm.
[0089]
The multilayer coating film formed by the above-described multilayer coating film forming method is an intermediate coating film having a uniform spectral reflectance. Such a multilayer coating film is also one of the present invention. Further, an article having the multilayer coating film is also one of the present invention.
[0090]
The method of forming a multilayer coating film of the present invention is a method using a specific intermediate coating apparatus and using a white paint and a black paint in which the pigment concentration, the non-volatile content and the paint viscosity are specified in specific ranges. As a result, the white paint and the black paint can be uniformly mixed in this apparatus, and as a result, an intermediate coating film having a uniform spectral reflectance can be formed. Therefore, the method for forming a multilayer coating film is a method capable of forming an excellent multilayer coating film, and can be suitably applied to an automobile body and parts.
[0091]
【Example】
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 the examples, “parts” means “parts by mass” unless otherwise specified.
[0092]
Production Example 1 (Preparation of white paint 1)
The white paint prepared with the following amounts was adjusted with xylene so that the time was 40 seconds with a # 4 Ford cup.
Titanium R-61 (Titanium dioxide manufactured by Sakai Chemical Industry Co., Ltd.) 50 parts
B-34 (Sakai Chemical Industry Co., Ltd. barium sulfate) 10 parts
Thermosetting polyester resin (manufactured by Nippon Paint Co., Ltd., acid value 20, hydroxyl value 100, min.
(2000 parts, solid content 60%) 100 parts
20 parts of Uban 20N-60 (butylated melamine manufactured by Mitsui Toatsu Co., solid content 60%)
10 parts of crosslinked resin particles (Nippon Paint Co., Ltd. structural viscosity imparting agent, solid content 20%)
Xylol 40 parts
230 copies in total
The obtained white paint 1 had a PWC of 45% by mass, a nonvolatile content of 50% by mass, and a paint viscosity of 0.14 Pa · s.
[0093]
Production Example 2 (Preparation of white paint 2)
The white paint prepared in Production Example 1 was adjusted with xylene so that the time was 30 seconds with a # 4 Ford cup.
The obtained white paint 2 had a PWC of 45% by mass, a nonvolatile content of 48% by mass, and a paint viscosity of 0.1 Pa · s.
[0094]
Production Example 3 (Preparation of white paint 3)
The white paint prepared in Production Example 1 was adjusted with xylene so that the coating time was 20 seconds with a # 4 Ford cup.
The obtained white paint 3 had a PWC of 45% by mass, a nonvolatile content of 44% by mass, and a paint viscosity of 0.07 Pa · s.
[0095]
Production Example 4 (Preparation of white paint 4)
The white paint prepared in Production Example 1 was adjusted with xylene so that the time was 50 seconds with a # 4 Ford cup.
The obtained white paint 4 had a PWC of 45% by mass, a nonvolatile content of 53% by mass, and a paint viscosity of 0.17 Pa · s.
[0096]
Production Example 5 (Preparation of black paint 1)
The black paint prepared with the following amounts was adjusted with xylene so that the time was 40 seconds with a # 4 Ford cup.
MA-100 (Mitsubishi Carbon carbon black) 7 parts
Thermosetting polyester resin (manufactured by Nippon Paint Co., Ltd., acid value 20, hydroxyl value 100, min.
(2000 parts, solid content 60%) 100 parts
20 parts of Uban 20N-60 (butylated melamine manufactured by Mitsui Toatsu Co., solid content 60%)
10 parts of crosslinked resin particles (Nippon Paint Co., Ltd. structural viscosity imparting agent, solid content 20%)
Xylol 30 parts
167 copies in total
The obtained black paint 1 had a PWC of 8.9% by mass, a nonvolatile content of 47% by mass, and a paint viscosity of 0.14 Pa · s.
[0097]
Production Example 6 (Preparation of black paint 2)
The black paint prepared in Production Example 5 was adjusted with xylene so that the time was 30 seconds with a # 4 Ford cup.
The obtained black paint 2 had a PWC of 8.9% by mass, a nonvolatile content of 42% by mass, and a paint viscosity of 0.1 Pa · s.
[0098]
Production Example 7 (Preparation of black paint 3)
The black paint prepared in Production Example 5 was adjusted with xylene so that the time was 20 seconds with a # 4 Ford cup.
The resulting black paint 3 had a PWC of 8.9% by mass, a nonvolatile content of 38% by mass, and a paint viscosity of 0.07 Pa · s.
[0099]
Production Example 8 (Preparation of black paint 4)
The black paint prepared in Production Example 5 was adjusted with xylene so that the time was 50 seconds with a # 4 Ford cup.
The obtained black paint 4 had a PWC of 8.9% by mass, a nonvolatile content of 51% by mass, and a paint viscosity of 0.17 Pa · s.
[0100]
Production Example 9 (Preparation of white paint 5)
The white paint prepared in Production Example 1 was adjusted with xylene so that the time was 13 seconds with a # 4 Ford cup.
The obtained white paint 5 had a PWC of 45% by mass, a nonvolatile content of 41% by mass, and a paint viscosity of 0.02 Pa · s.
[0101]
Production Example 10 (Preparation of white paint 6)
The white paint prepared in Production Example 1 was adjusted with xylene so that the coating time was 85 seconds with a # 4 Ford cup.
The obtained white paint 6 had a PWC of 45% by mass, a nonvolatile content of 56% by mass, and a paint viscosity of 0.33 Pa · s.
[0102]
Production Example 11 (Preparation of black paint 5)
The black paint prepared in Production Example 5 was adjusted with xylene so that the time was 13 seconds with a # 4 Ford cup.
The obtained black paint 5 had a PWC of 8.9% by mass, a nonvolatile content of 35% by mass, and a paint viscosity of 0.02 Pa · s.
[0103]
Production Example 12 (Preparation of black paint 6)
The black paint prepared in Production Example 5 was adjusted with xylene so that a # 4 Ford cup was used for 85 seconds.
The obtained black paint 6 had a PWC of 8.9% by mass, a nonvolatile content of 54% by mass, and a paint viscosity of 0.33 Pa · s.
[0104]
Examples 1 to 8, Comparative Examples 1 to 4
(Method of forming multilayer coating film)
A 150 × 70 × 0.7 mm dull steel plate treated with zinc phosphate is electrodeposited with Power Top U-50 (trade name, Nippon Paint Co., Ltd., cationic electrodeposition paint) so as to have a dry film thickness of 20 μm. It was baked and cured at 30 ° C. for 30 minutes to obtain an electrodeposited substrate.
[0105]
On the electrodeposited substrate, each of the white paint and the black paint obtained in the production example was dried with a static mixer (manufactured by ABB) so as to have a mass ratio shown in Table 1. The coating was applied to a film thickness of 30 μm and baked and cured at 160 ° C. for 30 minutes to form an intermediate coating film.
[0106]
Further, on the formed intermediate coating film, Table 2 of AR-2000 [trade name, Nippon Paint Co., Ltd. aqueous base paint, coating color (A: white color base, B: silver metallic, C: black metallic)] Is spray-coated on two stages so as to have a dry film thickness of 15 μm, followed by a preheating step at 80 ° C. for 5 minutes, and then cooled to room temperature, and MacFlow O-1801w (trade name, Japan) (Paint Co., Ltd. organic solvent type clear paint) was spray-coated so as to have a dry film thickness of 35 μm, and was baked and cured at 140 ° C. for 30 minutes to obtain a multilayer coating film.
[0107]
The intermediate coating film formed as described above was evaluated as follows.
(N-coating N value)
The gray scale of the formed intermediate coating film was measured according to JIS Z-8721. The results are shown in Table 1.
(Coating uniformity)
The formed intermediate coating film was visually evaluated based on the following criteria. The results are shown in Table 1.
：: The formed film has a uniform hue.
Δ: The formed film is slightly non-uniform.
X: The formed film is mottled and non-uniform.
[0108]
(Manufacture of test plate for measuring spectral reflectance)
AR-2000 (trade name, Nippon Paint Co., Ltd., water-based base paint, coating color (A: white color base, B: silver metallic, C: black metallic)) was applied to the above-mentioned electrodeposited substrate so as to have a dry film thickness of 25 μm. After a preheating step at 80 ° C. for 5 minutes, the film was baked and cured at 160 ° C. for 30 minutes to form a base coating film.
[0109]
The base plate was prepared by producing the test plate (without the base coating film and the clear coating film) formed with the intermediate coating film by the above-mentioned multilayer coating film forming method and the test plate for measuring the spectral reflectance described above. The spectral reflectance of the test plate on which the film was formed (the intermediate coating film and the clear coating film were not formed) was measured as follows.
[0110]
(Measurement of spectral reflectance)
About the obtained coating film, an apparatus for attaching an integrating sphere was attached to a spectrophotometer (U-3200, manufactured by Hitachi, Ltd.), and the reflectance of the coating film was measured. The spectral reflectance spectra of each coating film are shown in FIGS. Since the reflection area of each of the coating films was about 400 to 700 nm, the average value of the reflectance at 400 to 700 nm was obtained and defined as the spectral reflectance. Table 2 shows the spectral reflectance of the intermediate coating film, the spectral reflectance of the base coating film, and the difference between the spectral reflectances of the intermediate coating film and the base coating film.
[0111]
[Table 1]

[0112]
[Table 2]

[0113]
In Examples, an intermediate coating film having each color of N-1 to N-9 and excellent in coating film uniformity was able to be obtained. Thereby, it became clear to perform any set gray intermediate coating. In addition, it is also clear that a coating film having a small difference in spectral reflectance between the intermediate coating film and the base coating film can be obtained. Could be obtained. On the other hand, when the paint viscosity difference between the white paint and the black paint is greater than 0.03 Pa · s (Comparative Examples 1 and 2), when the respective paint viscosities are less than 0.03 Pa · s and more than 0.3 Pa · s (Comparative Examples 3 and 4) resulted in an intermediate coating film having poor coating film uniformity.
[0114]
【The invention's effect】
Since the method for forming a multilayer coating film of the present invention has the above-described structure, the white coating material and the black coating material are uniformly mixed, and an intermediate coating film having a uniform spectral reflectance can be formed. is there. Therefore, it can be suitably applied to automobiles and parts.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the entire configuration of an intermediate coating apparatus according to the present invention.
FIG. 2 is a longitudinal sectional view of a rotary atomizing type coating gun according to the present invention.
FIG. 3 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 1.
FIG. 4 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 2.
FIG. 5 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 3.
FIG. 6 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 4.
FIG. 7 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 5.
FIG. 8 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 6.
FIG. 9 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 7.
FIG. 10 is a view showing a spectral reflectance spectrum of an intermediate coating film of Example 8.
11 is a view showing a spectral reflectance spectrum of an intermediate coating film of Comparative Example 1. FIG.
FIG. 12 is a view showing a spectral reflectance spectrum of an intermediate coating film of Comparative Example 2.
FIG. 13 is a view showing a spectral reflectance spectrum of an intermediate coating film of Comparative Example 3.
FIG. 14 is a view showing a spectral reflectance spectrum of an intermediate coating film of Comparative Example 4.
[Explanation of symbols]
1 White paint supply means
2 Black paint supply means
3 Rotary atomizing paint gun
4,7 Storage tank
5, 8 pipeline
6, 9 Variable displacement pump
11 Gun body
12 Air motor
13 Casing
14 sleeve
15 Rotation axis
16 Outflow hole
17 disk board
18 cups
19 Screw member
20 White paint supply path
21, 23 Paint spray nozzle
22 Black paint supply path

Claims (6)

On a substrate on which an undercoat coating is formed, an intermediate coating, a base coating and a clear coating, a multilayer coating forming method for sequentially forming,
The intermediate coating film includes a white paint supply unit that supplies a white paint with a variable supply amount, and a black paint supply unit that supplies a black paint with a variable supply amount. Means and the black paint supply means are formed independently using an intermediate coating apparatus connected to a rotary atomizing coating gun,
The white paint and the black paint have a pigment concentration (PWC) of 2 to 60% by mass, a nonvolatile content of 35 to 60% by mass, and a paint viscosity of 0.03 to 0.3 Pa · s,
The white paint and the black paint, the difference in the paint viscosity is 0.03 Pa · s or less,
The intermediate paint obtained by mixing the white paint and the black paint has a pigment concentration (PWC) of 2 to 60% by mass, a non-volatile content of 35 to 60% by mass, and a paint viscosity of 0.03 to 0.3 Pa. A method for forming a multilayer coating film, wherein The method according to claim 1, wherein the intermediate coating film is a gray or white intermediate coating film. The spectral reflectance in the reflection region within the wavelength range of 300 to 700 nm of the intermediate coating film is within ± 15% of the spectral reflectance of the base coating film in the reflection region within the wavelength range of 300 to 700 nm. 3. The method for forming a multilayer coating film according to 1 or 2. The multi-layer coating according to claim 1, 2 or 3, wherein the base coating and the clear coating are formed by applying a glitter-containing base coating and a clear coating by a wet-on-wet method and simultaneously curing the coating. Film formation method. A multilayer coating film formed by the multilayer coating film forming method according to claim 1. An article comprising the multilayer coating film according to claim 5.

Images