JP2000084473A - Method for forming and repairing laminated coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the hue difference of a coating film in a thin part or a repaired part by setting up a spectroscopic reflectance in a reflective area within a specified wavelength range of an intermediate coating film to be within a specified range of a spectroscopic reflectance in a reflective area within a specified wavelength range of a color base coating film. SOLUTION: An electrodeposition coating film 2 is formed on a base material 1 such as a lead phosphate-treated dull steel plate, and an intermediate coating film 3 is formed on the coating film 2. On the coating film 3 is formed a laminated coating film 7 comprising a color base coating film 4 formed by a three coat one bake method, a mica powder-containing base coating film 5, and a clear coating film 6. A spectroscopic reflectance in a reflective area 300-700 nm in wavelength of the coating film 3 is set up to be within ±15%, more preferably within ±10%, of the spectroscopic reflectance in a reflective area 300-700 nm in wavelength of the coating film 4. In this way, in the whole, a uniform coating film appearance can be developed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-coating method in which an intermediate coating film is formed on a surface of an object to be coated, and then a color base coating, a base coating containing a glitter material, and a clear coating are sequentially applied by a wet-on-wet method. The present invention relates to a method for forming a multilayer coating film by a bake method and a method for repairing the multilayer coating film.

[0002]

2. Description of the Related Art Hitherto, as a top coat for an automobile body or the like, a coating using a glittering material such as aluminum flake or mica powder has been known. In a top coat containing such a brilliant material, generally, a base paint containing a brilliant material and a color pigment is applied, and a clear paint is applied thereon by a wet-on-wet method, followed by a baking treatment. A two-coat one-bake coating film forming method of simultaneously curing the coating film is employed.

However, in such a method, since the glittering material and the coloring pigment are both contained in the same coating film, the glittering effect of the glittering material may not be sufficiently exhibited. In such a case, first, a color base paint containing a coloring pigment is applied, and then a baking process is performed and then dried, and a glitter material-containing base paint containing a glitter material is applied thereon, and a wet paint is applied thereon. In some cases, a three-coat two-bake coating film forming method of applying a clear paint by an on-wet method is employed. In such a laminated coating film, since the glittering material-containing base layer containing the glittering material is formed on the color base layer containing the coloring pigment, the glittering feeling of the glittering material is sufficiently exhibited, and excellent design properties are exhibited. It is possible to form a laminated coating film having

[0004] However, in the three-coat two-bake method, two baking treatments are required in the overcoating, which complicates the painting process and requires a long time in the painting process. Therefore, recently, three coats 1 in which a color base paint, a glitter-containing base paint, and a clear paint are all applied by a wet-on-wet method and then a baking treatment is performed.
A bake scheme has been proposed.

[0005] When the above-mentioned laminated coating film is formed by coating on a surface of an object having a relatively complicated shape such as an automobile body, the thickness of the laminated coating film becomes uneven. In some cases, the hue of a portion having a small film thickness is different from the hue of another portion.

In the case where the above-mentioned laminated coating film is formed on an object to be coated such as an automobile body, if an abnormality is found in the appearance of the coating film of the laminated coating film due to contamination of foreign matters, etc., Repairs are generally performed. In repairing such a laminated coating film, usually, the portion to be repaired is sanded and removed with a sandpaper or the like until the intermediate coating layer is reached, and then a color base paint, a bright material-containing base paint, and a clear paint are applied to the repaired portion in this order. Painted and repaired. When the repaired portion is painted, each paint is usually applied also to a peripheral region of the sharpened portion. Therefore, in the peripheral region of the repaired portion, a region in which the repaired laminated coating is formed on the previously formed laminated coating is generated. For this reason, the hue of the coating film is shifted between the portion where the multilayer coating film is overcoated and the other portion, and the appearance of the coating film may be uneven.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems, to reduce the difference in the color hue of the color base coating film between the thinned portion and the repaired portion, and to develop a uniform coating appearance. It is an object of the present invention to provide a method for forming a laminated coating film and a method for repairing the same.

[0008]

According to the method of forming a laminated coating film of the present invention, an intermediate coating film is formed on the surface of an object to be coated, and then a color base paint containing a coloring pigment and a glittering material containing a glittering material. This is a method of forming a multilayer coating film in which a base coating material and a clear coating material are sequentially applied by a wet-on-wet method, and each coating film is cured by a three-coat one-bake method. The wavelength of the intermediate coating film is within a range of 300 nm to 700 nm. The spectral reflectance in the reflection area is 300 nm at the wavelength of the color base coating film.
It is characterized in that it is set so as to be within a range of ± 15% of a spectral reflectance in a reflection region within a range of m to 700 nm.

[0009] The spectral reflectance of the intermediate coating film and the color base coating film specified in the present invention is 300 nm to 70 nm.
It is a spectral reflectance in a reflection region within a range of 0 nm.
That is, it is the average value of the reflectance in the reflection region within the wavelength range of 300 nm to 700 nm. For example, when the reflection region in the wavelength range of 300 nm to 700 nm of the intermediate coating film exists at a wavelength of 400 nm to 700 nm, the average value of the spectral reflectance of the intermediate coating film at a wavelength of 400 nm to 700 nm is obtained. Similarly, when the reflection region in the wavelength range of 300 nm to 700 nm of the color base coating exists at a wavelength of 600 nm to 700 nm,
It is the average value of the spectral reflectance at a wavelength of 600 nm to 700 nm of the color base coating film.

[0010] For the reflection area of the coating film, for example, a target coating film is applied on a JIS concealing rate test paper with a film thickness that causes incomplete concealment, and the spectral reflectance curves on a white background and a black background are measured. However, it can be defined as a region where the difference in reflectance at the same wavelength is 1% or more. In the case of a gray or white intermediate coating film, a wavelength of 400 nm to 700 nm is generally a reflection region. In the case of a red coating film, 650 nm to 7
00 nm, 600 nm to 7 in the case of an orange type coating film
00 nm, in the case of a yellow-based coating film, 550 nm to 700
nm, in the case of a blue coating film, 400 nm to 500 n
Each region of m is generally a reflection region.

In the present invention, the spectral reflectance of the intermediate coating film thus determined is set so as to be within ± 15% of the spectral reflectance of the color base coating film.
The method for measuring the spectral reflectance is not particularly limited, but can be generally measured using a spectrophotometer.
For example, 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.

In the present invention, the spectral reflectance of the intermediate coating film is ± 15 of the spectral reflectance of the color base coating film.
%, More preferably ± 10%. By setting the thickness within such a range, it is possible to reduce the difference in the hue (color difference) of the coating film in the portion where the film thickness of the color base coating film is thin or in the repaired portion, and the overall appearance of the coating film is uniform. Can be obtained.

According to the present invention, even when the thickness of the color base coating film varies within a range of ± 30% or more of the average film thickness, the coating film is uniform so that the color difference is not visually perceived. Film appearance can be obtained.

The laminated coating film of the present invention is a laminated coating film formed by the above-mentioned forming method of the present invention. In one embodiment of the multilayer coating film of the present invention, the multilayer coating film has a repaired portion, and the multilayer coating film is overcoated in an area around the repaired portion. According to the present invention,
Thus, even in the case where the multilayer coating film is overcoated in the peripheral area of the repaired portion, it is possible to prevent a sense of color difference between the coating films, and to form a multilayer coating film having a uniform hue. it can.

An article of the present invention is characterized by being an article having the above-mentioned laminated coating film of the present invention. The method for repairing a laminated coating film of the present invention is a method for forming a laminated coating film in which a color base coating film containing a coloring pigment, a brilliant-containing base coating film containing a brilliant material, and a clear coating film are sequentially formed on the intermediate coating film. It is a method of repairing the film, after sharpening and removing the repaired portion of the laminated coating until it reaches the intermediate coating film, apply a color base paint, a glitter-containing base paint, and a clear paint on the sharpened portion and its surrounding area. A repair method for forming a laminated coating film for repair by coating sequentially, wherein the wavelength of the intermediate coating film is 300 n
The spectral reflectance in the reflection region in the range of m to 700 nm is within ± 15%, preferably ± 10% of the spectral reflectance in the reflection region in the wavelength range of 300 nm to 700 nm of the color base coating film. It is characterized in that it is set so that

The spectral reflectance in the repair method of the present invention is:
This is the same as the spectral reflectance in the above-described forming method of the present invention. Hereinafter, the method for forming a multilayer coating film, the multilayer coating film, the article, and the method for repairing the multilayer coating film of the present invention will be described in more detail.

Intermediate coating film In the present invention, the intermediate coating film can be formed by applying an intermediate coating material on the surface of the object to be coated and baking it. As described below, after forming an undercoating film on the surface of the article to be coated, an intermediate coating film may be formed thereon. 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 generally contains various organic and inorganic color pigments, extender pigments, and the like.

Examples of the color pigments contained in the intermediate coating composition include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, and dioxane pigments. Pigments, quinacridone-based pigments, isoindolinone-based pigments, metal complex pigments, and the like, and inorganic salts 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.
As a standard, a gray or white intermediate paint having carbon black and titanium dioxide as main pigments is used. In a special case, a so-called color intermediate coating material in which various coloring pigments are combined can be used.

In the present invention, as described above, the spectral reflectance of the intermediate coating film in the reflection region within the wavelength range of 300 nm to 700 nm is equal to the wavelength of the color base coating film of 300 nm.
It is set so as to be within a range of ± 15% of the spectral reflectance in the reflection region within the range of nm to 700 nm. Therefore, in the present invention, by adjusting the kind and content of these coloring pigments, an intermediate coating film is formed using an intermediate coating material adjusted to have a spectral reflectance within the above range.

The film-forming resin used in the intermediate coating composition is not particularly limited, and a thermosetting resin is generally used. These resins include acrylic resin, polyester resin, alkyd resin, epoxy resin,
A film-forming resin such as a urethane resin can be 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 alkyd resin and / or a polyester resin with an amino resin is preferable.

After the intermediate coating is applied to the surface of the object to be coated,
It is cured by heating, but the temperature at this time is 10
The temperature is generally about 0 to 180 ° C, more preferably 1 to 180 ° C.
It is about 20 to 160 ° C. If the heating temperature is too high, the coating film tends to be hard, and if the heating temperature is too low, curing may be insufficient. The curing time varies depending on the curing temperature, but is generally 10 to 120 ° C to 160 ° C.
A curing time of about 30 minutes is appropriate. The thickness of the intermediate coating film is not particularly limited, but is 20 to
It is preferably about 60 μm, more preferably 30 to 40.
It is about μm.

Color base paint In the present invention, after the above-mentioned intermediate coating film is formed, a color base paint containing a color pigment is applied thereon. During this coating, the intermediate coating film may be in a cured state or in an uncured state.

As the color pigments to be contained in the color base paint, similar to the above-mentioned intermediate paints, for example, organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments Pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments and the like can be mentioned. Inorganic pigments include yellow salts, yellow iron oxide, red iron oxide, carbon black, titanium dioxide and the like. As the extender, calcium carbonate, barium sulfate, clay, talc and the like are used.

The film-forming resin in the color base paint is not particularly limited, and a general film-forming thermosetting resin is used, and specific examples thereof include an acrylic resin, a polyester resin, and an alkyd resin. ,Epoxy resin,
A film-forming resin such as a urethane resin is used, and 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.

The application amount of the color base paint is not particularly limited, but it is preferable to apply the color base paint so that the dried film thickness is about 10 to 30 μm, more preferably 15 to 25 μm. It is about.

[0026] In the glittering material-containing base coating present invention, after coating the color base paint, glittering material-containing base coating wet-on-wet method is painted.

The brilliant contained in the brilliant-containing base paint includes, for example, brilliant pigments such as mica powder, interference mica powder, white mica powder, alumina flake, graphite, flaky color pigment, and the like, aluminum, copper, zinc ,
A brilliant material composed of a metal or alloy such as iron, nickel, and tin can be used. The shape of these brilliant materials is not particularly limited, but is preferably, for example, scaly,
Those having an average particle size of 2 to 50 μm and a thickness of 0.1 to 3 μm are particularly preferred.

The glittering material-containing base coating material of the present invention may contain a coloring pigment. Examples of such color pigments include the same color pigments as described in the intermediate coating and the color base paint.

The content of the glittering material is not particularly limited, but is generally about 0.1% to 20% by PWC, preferably 0.5% to 18%, more preferably 1%.
% To 15%. If the content of the glittering material is too large, the appearance of the coating film tends to decrease. On the other hand, if the content is too small, the imparting of design properties by the glitter material may be insufficient.

The film-forming resin contained in the glittering material-containing base paint is not particularly limited, and a thermoplastic resin having general film-forming properties is used. Specifically, at least one thermosetting resin having a hydroxyl group or the like selected from the group consisting of an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin and the like can be used, and these are amino resins and / or block resins. It can be used in combination with a curing agent such as an isocyanate resin. In particular, a combination of an acrylic resin having a hydroxyl group and an amino resin is preferable from the viewpoint of weather resistance, pigment dispersibility, and coating workability.

The weight ratio of the film-forming resin to the curing agent in the glitter-containing base paint (film-forming resin / curing agent)
Is preferably from 90/10 to 10/90, more preferably from 80/20 to 50/50. If the amount of the curing agent is too small, the curability tends to decrease, and if it is too large, the coating film may be hard and brittle.

It is preferable that a viscosity controlling agent is contained in the bright material-containing base paint. 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.

Examples of such a material include a swelling dispersion of an aliphatic amide, a amide-based fatty acid, and a polyamide-based viscosity control agent such as a long-chain polyaminoamide phosphate.
And a polyethylene-based viscosity controlling agent such as a colloidal swelling dispersion of polyethylene oxide.

Other viscosity control agents include organic bentonite-based viscosity control agents such as organic acid smetite clay and montmorillonite, inorganic pigments such as aluminum silicate and barium sulfate, and flat pigments which exhibit viscosity depending on the shape of the pigment. Can be mentioned. It is preferable that these viscosity control agents do not affect the gloss and the color development when formed into a coating film.

Further, as a preferable viscosity controlling agent used in the present invention, non-crosslinked or crosslinked resin particles utilizing the interaction of polar groups can be mentioned. As the crosslinked resin particles, crosslinked resin particles that are insoluble in the organic solvent used in the coating composition and have an average particle diameter 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. Such crosslinked resin particles include 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. Is preferably obtained by emulsion-polymerizing an ethylenically unsaturated monomer in an aqueous medium in the presence of a.

The monomer having a zwitterionic group in the molecule includes -N ⁺ -R-COO ^- or -N ⁺ -R-
Those represented as SO ₃ ^— and having two or more hydroxyl groups are included. 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.

The resin having an emulsifying zwitterionic group in the molecule, which is synthesized using the above monomer, has an acid value of 30 to 150 mgKOH / g, preferably 4 to 150 mgKOH / g.
0 to 150 mgKOH / g and a number average molecular weight of 50
It is preferable to use a polyester resin having 0 to 5000, preferably 700 to 3000. If the acid value and the number average molecular weight are too large, the handleability of the resin is reduced, and if the acid value and the number average molecular weight are too small, the resin having emulsifying ability is desorbed when a coating film is formed, Solvent resistance may be reduced.

In the synthesis of the crosslinked resin particles, it is preferable to include a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule 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 weight of all the 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.

The crosslinked resin particles do not contain a low-molecular emulsifier and a protective colloid which lower the performance of the coating film when formed, and are appropriately crosslinked. By blending the resin particles in the coating composition, the water resistance, solvent resistance, gloss, and the like of the coating film can be improved.

The addition amount of the viscosity controlling agent is preferably 0.01 to 15 parts by weight, more preferably 0.1 to 12 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the resin solid content of the coating composition. It is 2 to 9 parts by weight. If the added amount of the viscosity controlling agent is too large, the appearance of the coating film tends to decrease.If the added amount of the viscosity controlling agent is too small, the viscosity controlling effect cannot be obtained, and the adhesion between the layers in the laminated coating film occurs. Or inversion between layers may occur.

In the glittering material-containing base coating material of the present invention, in addition to the above components, a curing catalyst, an ultraviolet absorber, an antioxidant, a surface conditioner, and the like can be used, if necessary.

The total solid content of the brilliant material-containing base coating material in the present invention is preferably 20 to 70% by weight, more preferably 30 to 50% by weight at the time of preparation. Outside of these ranges, paint stability tends to decrease. Further, the total solid content at the time of coating is preferably 10 to 60% by weight, more preferably 20 to 50% by weight. If the content is higher than these ranges, the viscosity may become too high and the appearance of the coating film may deteriorate. On the other hand, when the ratio is lower than these ranges, the viscosity becomes too low, and appearance defects such as adaptation and unevenness between layers of the laminated coating film may occur.

The thickness of the glitter material-containing base paint at the time of coating is
It is appropriately selected depending on the use of the laminated coating film and the like, and is not particularly limited.
m, more preferably about 7 to 25 μm. If the film thickness is too large, the sharpness of the coating film may be reduced, or defects such as unevenness or flow may occur during coating. Also,
If the film thickness is too small, the underlayer cannot be concealed and the film may be cut.

As the glitter-containing base coating material used in the present invention, a solution-type base coating material is generally preferably used.
Emulsion) and non-aqueous dispersion type can be preferably used.

When the luster-containing base coating is an aqueous coating, US Pat.
Thermosetting film-forming resins specifically described in JP-A Nos. 1,125 and 5,183,504 can be used. In particular, a thermosetting film-forming resin obtained by combining an acrylic resin having an acrylamide group, a hydroxyl group and an acid group described in US Pat. No. 5,183,504 with a melamine resin is preferably used in terms of finish and appearance performance. be able to.

When the glittering material-containing base paint is an aqueous type paint, the glittering material-containing base coating film should be coated before coating the clear paint in order to obtain a good finished coating film.
It is desirable to heat at 2C for 2 to 10 minutes.

When the laminated coating film of the present invention is formed by coating an object such as an automobile body, the glitter-containing base coating material is preferably applied by a coating method such as electrostatic coating or air spraying. In order to suppress uneven brightness, it is preferable to apply the paint in two stages rather than one stage.

[0048] As the film-forming resin of the clear paint used in the clear coating composition present invention is not limited in particular, it is possible to use a thermosetting film-forming resin. Specifically, 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 is used.

The solid content in the clear paint is preferably 20 to 60% by weight, more preferably 35 to 55% by weight at the time of preparation. The solid content at the time of coating is preferably from 10 to 50% by weight, and more preferably from 20 to 50% by weight.

The clear paint is preferably applied on the uncured brilliant-containing base coating film by a method such as electrostatic coating or air spraying. The dry film thickness of the clear coating film is generally preferably about 10 to 60 μm, more preferably 2 to 60 μm.
It is about 0 to 50 μm. If the film thickness is too thick, problems such as splashes and sagging may occur at the time of coating, and if the film thickness is too thin, irregularities on the base may not be concealed.

Since the clear paint is applied on the glitter-containing base coating film by a wet-on-wet method, it is preferable that the above-mentioned viscosity controlling agent is contained. As the viscosity control agent, the same viscosity control agent as described for the glittering material-containing base paint can be used. The amount of the viscosity control agent added to the clear paint is determined based on the resin solid content of the paint composition.
0.01 to 10 parts by weight with respect to 00 parts by weight is preferable,
The content is more preferably 0.02 to 8 parts by weight, and even more preferably 0.03 to 6 parts by weight. If the added amount of the viscosity controlling agent is too large, the appearance of the coating film may be deteriorated, and if the added amount is too small, the effect of controlling the viscosity cannot be obtained, and adaptation or inversion between the layers of the laminated coating film occurs. There are cases.

The form of the clear paint may be any of an organic solvent type, an aqueous type (water-soluble, water-dispersible, emulsion), a non-aqueous type, and a powder type. If necessary, a curing catalyst, a surface conditioner and the like may be contained.

[0053] In the undercoating film present invention, after forming the undercoating film a coating object surface, form an intermediate coating film thereon may be formed multilayer coating film of the present invention thereon . When an undercoat film is formed on a conductive substrate such as a steel plate, the undercoat film can be formed using an electrodeposition paint. The electrodeposition paint used in this case may be either a cationic type or an anion type. However, since the cationic type electrodeposition paint is excellent in anticorrosion properties, it is used to form a laminated coating film having excellent anticorrosion properties. can do.

[0054] In the multilayer coating films present invention, as described above, color base coating film,
A laminated coating film is formed by laminating a glitter-containing base coating film and a clear coating film. The thickness of the entire laminated coating film is appropriately selected depending on the use in which the laminated coating film is used, and is not particularly limited, but is generally in the range of 30 to 300 μm, and preferably in the range of 50 to 250 μm. If the film thickness is too large, the film physical properties such as a thermal cycle may be reduced, and if the film thickness is too small, the strength of the film itself may be reduced.

Coating object The coating object on which the laminated coating film is formed after forming the intermediate coating film in the present invention is not particularly limited. Examples thereof include wood, metal, glass, cloth, and plastic. , Foams and the like. In particular, the present invention can be advantageously applied to metal substrates and castings, and can be particularly advantageously used for metal products that can be subjected to cationic electrodeposition coating.

As such a metal product, for example,
Substrates made of iron, copper, aluminum, tin, zinc, and the like, and alloys containing these metals are included. Specific examples include a car body such as a car, a truck, a motorcycle, and a bus and parts thereof. It is particularly preferable that these metal products have been previously subjected to a chemical conversion treatment with a phosphate or a chromate.

Repair method The repair method of the present invention is a method capable of repairing the above-mentioned laminated coating film of the present invention. In the case where abnormalities in the appearance of the coating film such as bumps are observed in the laminated coating film formed according to the forming method of the present invention, this portion can be repaired according to the repair method of the present invention. According to the repair method of the present invention, after the repaired portion of the laminated coating film is polished and removed until reaching the intermediate coating film, a color base paint, a glitter-containing base paint, and a clear paint are formed on the polished portion and its peripheral area. The paint can be applied sequentially and repaired. Each paint used at the time of this repair may be the same paint as the paint used at the time of forming the multilayer coating film, or any paint that can express the appearance of the coating film such as hue in almost the same manner. And paints having different compositions.

The repairing portion is sharpened by, for example, sharpening a defective portion with a rough paper of sandpaper # 400 or so, sharpening the defective portion with fine sandpaper of about # 1000, and arranging the base.

After the repaired portion has been sharpened, the above-mentioned paints are applied to the sharpened portion and its peripheral area to form a repaired coating film. The method of applying the repair paint is not particularly limited, but is generally performed by spray coating such as hand blowing or air spray. After coating, the coating film is usually cured by baking.

According to the repair method of the present invention, a repair coating film is formed on the sharpened portion and its peripheral region.
In the peripheral area, the repaired multilayer coating is overcoated on the multilayer coating. According to the repair method of the present invention, it is possible to reduce the difference in hue from other portions even in such a portion that has been overcoated, thereby causing a difference in the appearance of the coating film between the repaired portion and the non-repaired portion. It can be repaired without.

[0061]

According to the present invention, it is possible to reduce the difference in the hue of a coating film between a thin portion and a repaired portion of a color base coating film, and to form a laminated coating film having a uniform coating appearance as a whole. Can be.

In the coating of an automobile body or the like, it is necessary to form a top coat having various hues. According to the present invention, the spectral reflectance of the intermediate coat is determined by changing the spectral reflectance of the color base coat. Since the spectral reflectance may be set to be within a predetermined range, one intermediate coating film can correspond to a plurality of types of overcoat laminated coating films, which is efficient and economical.

Also, in the case of repairing a top-coated laminated coating film, the repair method of the present invention can reduce the difference in the hue of the coating film in the repaired portion, and can repair efficiently and economically.

[0064]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to specific examples. Parts and% mean parts by weight and% by weight, respectively, unless otherwise specified.

Preparation of Crosslinked Resin Particles In a reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube, a cooling tube and a decanter, 213 parts of bishydroxyethyltaurine, 208 parts of neopentyl glycol, 296 parts of phthalic anhydride, azeline 376 parts of acid and xylene 3
0 parts were charged and heated. Water generated by the reaction was removed by azeotropic distillation with xylene. The reaction solution temperature was set at 210 ° C. over about 3 hours from the start of reflux, and the acid value equivalent to carboxylic acid was 13
Stirring and dehydration were continued until 5 mgKOH / g. After cooling the liquid temperature to 140 ° C., 500 parts of “Kajura E10” (trade name: glycidyl versatate ester manufactured by Shell) was dropped in 30 minutes, and then stirring was continued for 2 hours to terminate the reaction. . Acid value 55m
An amphoteric ionic group-containing polyester resin having a gKOH / g, a hydroxyl value of 91 mgKOH / g and a number average molecular weight of 1250 was obtained.

This zwitterionic group-containing polyester resin 1
0 parts, 140 parts of deionized water, 1 part of dimethylethanolamine, 50 parts of styrene and 50 parts of ethylene glycol dimethacrylate were vigorously stirred in a stainless steel beaker to prepare a monomer suspension. Also, an aqueous initiator solution was prepared by mixing 0.5 parts of azobiscyanovaleric acid, 40 parts of deionized water and 0.32 parts of dimethylethanolamine.

A reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube and a cooling tube was charged with 5 parts of the amphoteric group-containing polyester resin, 280 parts of deionized water and 0.5 part of dimethylethanolamine. The temperature rose. Here, 251 parts of the monomer suspension and 40.82 of the aqueous initiator solution were added.
Was added dropwise over 60 minutes at the same time, and the reaction was continued for another 60 minutes, and then the reaction was terminated.

A crosslinked resin particle emulsion having a particle diameter of 55 nm as measured by the dynamic light scattering method was obtained. Xylene was added to the crosslinked resin particle emulsion, water was removed by azeotropic distillation under reduced pressure, and the medium was replaced with xylene to obtain a xylene solution of crosslinked resin particles having a solid content of 20% by weight.

Preparation of Coating Compositions The coating compositions used in Examples and Comparative Examples were prepared according to the following coating formulations A to F.

Paint formulation A: Ultra light brown color base paint TYPEK R-820 (white pigment manufactured by Ishihara Sangyo Co., Ltd.) 30.0 Tarox LLX-LO (tea pigment manufactured by Titanium Co., Ltd.) 0.2 Degussa Carbon FW200P (made by Degussa, black pigment) 0.11 Thermosetting acrylic resin 40.6 (20.3) (manufactured by Nippon Int. Co., Ltd., hydroxyl group 45, acid value 15, number average molecular weight 21,000, solid content 50%) Uban 20N60 14.5 (8.7) (Mitsui Toatsu Butylated melamine Resin, solid content 60%) Acrylic surface conditioner 0.2 Crosslinked resin particles 7.5 (1.5) (Synthesis example, solid content 20%) n-butanol 2.0 butyl acetate 3.6 toluene 1.3 total 100.01 ・ Painting mixture B: Base coating containing mica powder Pearl Grace SME-90-9 3.0 (Mica powder made by Nippon Koken Co., Ltd.) Thermosetting acrylic resin 38.4 (23.0) (Nippon Paint Co., Ltd., hydroxyl value 5 , Acid number 15, number average molecular weight 15000, solid content 60%) Uban 20N60 25.3 (15.2) (butylated melamine resin manufactured by Mitsui Toatsu Co., solid content 60%) Liponox NC-60 (manufactured by Lion Oil & Fat Co., surface adjustment) 0.2) Crosslinked resin particles 12.5 (2.5) (Synthesis example, solid content 20%) n-butanol 3.0 butyl acetate 3.0 xylol 8.4 toluene 6.2 total 100.0 ・ Clear paint formulation C: “Superlac O-150 Clear (manufactured by Nippon Paint Co., Ltd. Acrylic / melamine resin paint) "-Paint composition D: Gray intermediate paint" Olga P-Gray (Nippon Paint Co., Ltd., polyester / melamine resin paint) "-Paint composition E: Light gray intermediate paint Paint composition D / Painting composition F = 1/2 mixture ・ Painting composition F: Ultralight gray intermediate coating paint Taipaque R-820 (Ishihara Sangyo Co., Ltd., white Pigment) 30.0 Carbon black MA100 (Mitsubishi Carbon, black pigment) 0.001 Thermosetting polyester resin 30.0 (21.0) (Nippon Paint Co., Ltd., hydroxyl value 90, acid value 8, number average molecular weight 1,800, solid content 70%) Uban 128 15.0 (9.0) (Butylated melamine resin, solid content 60%, manufactured by Mitsui Cytec Co., Ltd.) Crosslinked resin particles 12.5 (2.5) (synthesis example, solid content 20%) Resimix RL-4 (manufactured by Mitsui Toatsu Co., surface conditioning) 0.1 n-butanol 4.0 Solvesso 100 8.4 Subtotal 100.001 Measurement of spectral reflectance Color base paint (paint formulation A), gray intermediate paint (paint D), light gray intermediate paint (paint) The spectral reflectances of the coating films obtained from the formulation E) and the superlight gray intermediate coating (paint formulation F) were measured as follows.

0.8 mm thick treated with zinc phosphate, 10 mm thick
On a dull steel sheet of cm × 30 cm, a cationic electrodeposition paint “Power Top U-50” (trade name, manufactured by Nippon Paint Co., Ltd., cationic electrodeposition paint) is electrodeposited so as to have a dry film thickness of 20 μm. Bake at 160 ° C. for 30 minutes. Next, on the obtained electrodeposition coating film, each of the above coating materials was dried to a film thickness of 45 μm.
m and baked at 140 ° C. for 20 minutes.

With respect to the obtained sample 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. FIGS. 2 to 5 show the spectral reflectance spectra of the respective coating films. 2 shows a color base coating film, FIG. 3 shows a super light gray intermediate coating film, FIG. 4 shows a light gray intermediate coating film, and FIG. 5 shows a gray intermediate coating film. In any of the coating films shown in FIGS. 2 to 5, the reflection region was about 400 nm to 700 nm. Therefore, as shown in FIGS. 2 to 5, the average value of the reflectance at 400 nm to 700 nm was obtained. The spectral reflectance was used.
The spectral reflectance of the color base coating shown in FIG. 2 is 69%, the spectral reflectance of the super light gray intermediate coating shown in FIG. 3 is 70%, and the light gray intermediate coating shown in FIG. Was 60%, and the spectral reflectance of the gray intermediate coating film shown in FIG. 5 was 29%.

Next, for each sample coating film, the hue of the coating film was measured using a color difference meter (CR-200 manufactured by Minolta Co., Ltd.). Table 1 shows the L value, a value, and b value of each coating film.
Table 1 shows the difference in spectral reflectance from the color base coating film.

[0074]

[Table 1]

As is clear from Table 1, the reflectance of the super light gray intermediate coating film and the light gray intermediate coating film is within ± 15% of the reflectance of the color base coating film. On the other hand, it is understood that the film is an intermediate coating film according to the present invention.

Evaluation of sensation of color difference depending on film thickness In the same manner as above, a cationic electrodeposition coating film was formed on a dull steel plate, and each of the above intermediate coatings (coating formulation D to coating formulation F) was formed on this cationic electrodeposition coating film. ) Has a dry film thickness of 35 μm
After spray-coating so as to obtain, it was baked at 140 ° C. for 20 minutes. Next, a color base paint (paint formulation A) was spray-coated on each intermediate coat so that a concentration gradient of 5 to 30 μm was formed in a dry film thickness.

The hue of each sample coating film was measured at a portion where the thickness of the color base coating film was different, and the difference ΔE from the hue at a portion where the thickness of the color base coating film was 30 μm was measured. FIG. 1 is a diagram showing the relationship between the thickness of the color base coating film and ΔE. In FIG. 1, Example 1 shows a super light gray intermediate coating film, Example 2 shows a light gray intermediate coating film, and Comparative Example 1 shows a gray intermediate coating film. The value of the color difference ΔE at which the user does not feel the color difference feeling visually is 0.
5 was selected, and the film thickness at which ΔE was 0.5 or less was determined. As a result, the film thickness was 11 μm in Example 1, and 1 μm in Example 2.
It was 5 μm, and in the case of Comparative Example 1, it was 20 μm. Therefore, it can be seen that the use of the intermediate coating film of Example 1 and Example 2 does not cause a significant difference in hue even in a portion where the color base coating film is considerably thin.

Evaluation of the feeling of color difference in the repaired part : zinc phosphate treated thickness 0.8 mm, 10 cm × 30 c
m on a dull steel plate with a cationic electrodeposition paint (trade name “Power Top U-50”, manufactured by Nippon Paint Co., Ltd., cationic electrodeposition paint) so that the dry film thickness becomes 20 μm.
Bake at 160 ° C. for 30 minutes. Next, on the obtained electrodeposition coating film, a gray intermediate paint (paint formulation D), a light gray intermediate paint (paint formulation E), and a super light gray intermediate paint (paint formulation F) Each of the intermediate paints is spray-coated so that the dry film thickness becomes 30 μm.
Baking was performed at 40 ° C. for 20 minutes to form three types of intermediate coating films.

Next, for Ford Cup # 4, 18 seconds (20
C)), a color base paint (paint formulation A) diluted on the surface of the obtained intermediate coating film was subjected to auto REA in two stages so that the dry film thickness became 20 μm.
(Ransburg air electrostatic coating machine). After an interval of 5 minutes, the mica powder-containing base paint (paint blend B) diluted to a viscosity of 15 seconds (20 ° C.) with a Ford cup # 4 in a wet-on-wet manner to a dry film thickness of 15 μm. As described above, painting was performed using the auto REA in two stages. Further, after an interval of 5 minutes, the clear paint (paint C) diluted beforehand with a Ford cup # 4 to a viscosity of 20 seconds (20 ° C.) in a wet-on-wet manner has a dry film thickness of 30 μm.
After spray coating so as to obtain, three types of sample coating films were baked at 140 ° C. for 20 minutes.

FIG. 6 is a diagram showing the sectional structure of the coating film obtained as described above. An electrodeposition coating film 2 is formed on a base material 1 which is a dull steel sheet treated with zinc phosphate.
An intermediate coating film 3 is formed on the electrodeposition coating film 2. On the intermediate coating film 3, a laminated coating film 7 including a color base coating film 4, a mica powder-containing base coating film 5, and a clear coating film 6 formed by a three-coat one-bake method is formed.

Next, assuming that a portion up to 10 cm from the end of the painted steel plate is a repaired portion, water-sanding is performed using sandpaper (# 400) to reach the intermediate coating film 3. The repaired part was sharpened and removed. Thereafter, the sharpened portion and its peripheral region were hand-blown wet-on-wet and baked using the same color base paint, mica powder-containing base paint, and clear paint as described above, so as to have the same film thickness. .

FIG. 7 is a sectional view showing the state of the coating film after such repair. As shown in FIG. 7, in the sharpened portion, the laminated coating film 7 is removed until reaching the intermediate coating film 3. After sharpening and removing the repaired portion of the laminated coating film 7, a repaired laminated coating film 11 composed of the color base coating film 8, the mica powder-containing base coating film 9, and the clear coating film 10 is formed on the sharpened portion and the surrounding area. Have been. As shown in FIG. 7, in the peripheral region of the sharpened portion, a repair coating film 11 is formed on the multilayer coating film 7, and there is an overcoat region where the multilayer coating film is overcoated. .

Next, the coating film appearance of the repaired sample coating film was evaluated. The coating appearance is
The skin and design of the coating film were evaluated according to the following criteria.
Table 2 shows the evaluation results.

5: Excellent. 4: Excellent. 3: Normal.

2: Slightly inferior. 1: considerably poor. The sense of color difference between the sharpened portion and the overcoated region shown in FIG. 7 was evaluated based on the following criteria, and the hue of each portion was measured to calculate the color difference ΔE. Table 2 shows the measurement results.

5: No change is observed at all. 4: A slight change is observed. 3: A slight change is observed depending on the site.

2: There is considerable variation depending on the site. 1: The color has changed considerably.

[0088]

[Table 2]

As is evident from the results in Table 2, the ultra-light gray intermediate coating in which the spectral reflectance of the intermediate coating at a wavelength of 300 nm to 700 nm is within ± 15% of the spectral reflectance of the color base coating. The sample coating films of Examples 3 and 4 using the light gray intermediate coating as the intermediate coating and the sample coating of Comparative Example 2 using the gray intermediate coating falling outside the scope of the present invention. In addition to showing a good appearance of the coating film, the color difference between the overcoated area and the other area in the repaired part is extremely low. Therefore, the appearance of the coating film in the repaired portion can be made uniform, the occurrence of unevenness in the appearance of the coating film due to the repair can be prevented, and efficient and economical repair can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a film thickness of a color base coating film and a color difference ΔE.

FIG. 2 is a view showing a spectral reflectance spectrum of a color base coating film.

FIG. 3 is a view showing a spectral reflectance spectrum of a super light gray intermediate coating film.

FIG. 4 is a view showing a spectral reflectance spectrum of a light gray intermediate coating film.

FIG. 5 is a view showing a spectral reflectance spectrum of a gray intermediate coating film.

FIG. 6 is a sectional view showing an example of a laminated coating film formed on the intermediate coating film.

FIG. 7 is a cross-sectional view showing a peripheral region of a repaired portion of the laminated coating film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Electrodeposited coating film 3 ... Intermediate coating film 4 ... Color base coating film 5 ... Mica powder containing base coating film 6 ... Clear coating film 7 ... Laminated coating film 8 ... Color base coating film for repair 9 ... Repair Mica powder-containing base coating film for repair 10 ... Clear coating film for repair 11 ... Laminated coating film for repair

Claims (7)

[Claims] After forming an intermediate coating film on the surface of an object to be coated,
A method of forming a laminated coating film in which a color base paint containing a color pigment, a glitter-containing base paint containing a glitter, and a clear paint are sequentially coated by a wet-on-wet method, and each coating is cured by a 3-coat 1-bake method. In the above, the spectral reflectance in the reflection region within the wavelength range of 300 nm to 700 nm of the intermediate coating film is within ± 15% of the spectral reflectance in the reflection region within the wavelength range of 300 nm to 700 nm of the color base coating film. A method for forming a laminated coating film, wherein the method is set so that 2. The method according to claim 1, wherein the intermediate coating film is a gray or white intermediate coating film. 3. After forming an undercoating film on the surface of the object to be coated,
The method according to claim 1, wherein the intermediate coating film is formed thereon. 4. A laminated coating film formed by the method according to claim 1. 5. The laminated coating film has a repaired portion,
The multilayer coating film according to claim 4, wherein a multilayer coating film is overcoated in a peripheral region of the repaired portion. 6. An article having the laminated coating film according to claim 4. 7. A method for repairing a laminated coating film in which a color base coating film containing a coloring pigment, a brilliant-containing base coating film containing a brilliant material, and a clear coating film are sequentially formed on the intermediate coating film. Yes, after sharpening and removing the repaired part of the laminated coating until it reaches the intermediate coating, a color base paint, a bright material-containing base paint on the sharpened part and its surrounding area,
And a method for repairing a laminated coating film in which a clear paint is sequentially applied to form a laminated coating film for repair, wherein the spectral reflectance in a reflection region within a wavelength range of 300 nm to 700 nm of the intermediate coating film is the color base coating. A method for repairing a laminated coating film, wherein the film is set to have a spectral reflectance within a range of ± 15% in a reflection region within a wavelength range of 300 nm to 700 nm.