JP2002143756A - Method for forming double-layer coating film and substrate coated thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coating a substrate by a wet-on-wet coating system wherein the intermingling of the coating film on the lower side and that on the upper side can be reduced without markedly changing coating conditions and to provide a substrate coated thereby. SOLUTION: A substrate is coated with a plurality of coating films by a wet-on-wet coating system. The lower layer is first formed from a coating material containing polyethylene wax, and a recoating film is formed on the lower wet film, and the lower wet film and the recoated wet film are simultaneously baked. The lower wet film is at least one except the uppermost layer in double coating films such as (1) a double coating film prepared by forming a topcoating solid coating film on an intermediate coating film and (2) a double coating film prepared by forming an intermediate coating film on a chipping primer and forming a topcoating solid coating film on the intermediate coating film. A coated substrate is obtained by coating a substrate by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multi-layer coating film in which a plurality of coating films are applied in a wet-on-wet manner, and a coated article coated by the method for forming a multi-layer coating film.

[0002]

2. Description of the Related Art As a method of coating the outer surface of an automobile body, a method of applying a clear top coat paint by a wet-on-wet method on a base coat formed using a base coat paint and simultaneously baking the same is widely used. This coating method has excellent finish appearance, high durability,
As a method for efficiently obtaining a high quality coating film such as high solvent resistance and high weather resistance, it is particularly suitable for line painting of automobiles.

In order to obtain high appearance quality by this coating method, a combination of a base coat paint and a clear top coat paint is important. That is, if the formed base coat and the clear top coat are mixed, the arrangement of the pigment particles in the base coat is disturbed or the gloss is reduced, so that the finished appearance is deteriorated.

[0004] Here, a large degree of mixing of the base coat and the clear top coat is referred to as having high miscibility.

[0005] In order to prevent the deterioration of the finished appearance, conventionally, the molecular weight of the resin of the base coat paint has been increased.

[0006] Also, different kinds of resins are used for the base coat paint and the top coat paint. For example, when an acrylic resin is used as the resin for the top coat paint, without using an acrylic resin as the resin for the base coat paint, a polyester resin or a cellulose acetate butyrate resin is used, or these polyester resins are used as the acrylic resin. A method of blending a cellulose acetate butyrate resin to reduce the miscibility between the base coat and the top coat has been adopted.

Further, as another method of reducing the miscibility by changing the coating conditions, the interval of the wet-on-wet recoating time between the base coat paint and the top coat paint is increased, or the viscosity of the base coat paint is increased. Methods have been adopted.

Japanese Patent Application Laid-Open No. Hei 10-277478 discloses a three-coat, one-bake coating film forming method having excellent surface smoothness and good coating film appearance. After applying a color base paint containing a color pigment, a bright material-containing base paint containing a bright material, and a clear paint sequentially on the surface by a wet-on-wet method, a baking treatment is performed to cure each coating film. In the method of forming a coating film of the coat 1 baking method, the viscosity rise start time T1 in the curing process of the color base paint, the viscosity rise start time T2 in the cure process of the bright material-containing base paint, and the viscosity rise in the cure process of the clear paint. A coating film forming method is described in which each of the coating materials is prepared so that the starting time T3 satisfies the relationship of T1≤T2≤T3.

[0009]

However, the above-mentioned conventional method for forming a multilayer coating film in which a plurality of coating films are applied on a wet-on-wet basis changes the coating conditions of adjacent upper and lower coating films. The number of operation steps increases or the operation is complicated.

According to the present invention, in the wet-on-wet coating method, coating conditions are largely changed, for example, by using the same type of resin as the resin for the paint for forming the lower coating film and the paint for forming the overcoat film. It is an object of the present invention to provide a method for forming a multilayer coating film and a coated article which can reduce the miscibility between the lower coating film and the overcoated coating film without any problem.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have reached the following present invention. 1. In the method of forming a multi-layer coating film in which a plurality of coating films are applied on a substrate to be coated in a wet-on-wet manner, a lower-layer coating film is formed with a paint containing polyethylene wax, and then the lower-layer coating film is coated. A method for forming a multilayer coating film, comprising forming a multilayer coating film, and simultaneously baking and curing the lower coating film and the coated multilayer coating film. 2. The above polyethylene wax is coated with the lower coating film 10
The method for forming a multilayer coating film as described above, wherein 0.5 to 20 parts by mass is added to 0 parts by mass. 3. The above-described method for forming a multilayer coating film, wherein the polyethylene wax has a 95% volume particle diameter of 30 μm or less. 4. The lower layer side coating film is (1) a multi-layer coating film in which a top coating solid film is formed on the intermediate coating film, (2) an intermediate coating film is formed on the chipping primer, and (3) Multi-layer coating film in which a top-coating base coating film is formed on the intermediate coating film, and a top-coating top clear coating film is formed on the top-coating base coating film. Or (4) an intermediate coating film formed on the chipping primer, a top coating base film formed on the intermediate coating film, and a top clear coating film formed on the top coating film. The method for forming a multilayer coating film according to any one of claims 1 to 3, wherein the coating film is at least one layer other than the uppermost layer in any one of the multilayer coating films.

[0012] In the following description of the present specification, for convenience of explanation, the constitution of the above-mentioned multilayer coating film is defined as (1) an intermediate coating film + a top coating solid coating, and (2) a chipping primer + an intermediate coating film. + Topcoat solid coating, (3) Intercoat coating + Topcoat basecoat + Topcoat top clear coating, or (4) Chipping primer + Intercoat coating + Topcoat basecoat + Topcoat topclear coating I do. 5. The above method for forming a multilayer coating film, wherein the top clear coating material used for forming the top clear coating film contains a carboxyl group-containing polymer and an epoxy group-containing polymer. 6. A coated article to be coated by the above-described method for forming a multilayer coating film.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail.

[0014]Composite coating method  The method for forming a composite coating film of the present invention comprises the steps of:
In the method of painting wet on wet,
Forming the lower coating film with paint containing Tylene wax
Then, to form a re-coating film on the lower coating film,
Simultaneously bake and cure the lower coating and the overcoat
Things.

[0015] Preferably, the lower layer side coating film is
(1) Intermediate coating film + top coating solid coating film, (2) Chipping primer + intermediate coating film + top coating solid coating film,
(3) at least one layer other than the top layer in (3) an intermediate coating film + a top coating base film + a top coating clear film, or (4) a tipping primer + a middle coating film + a top coating base coating film + a top coating clear coating film. It is a coating film.

The substrate to be coated is not limited, and metals such as iron, aluminum, copper or alloys thereof; polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, Acrylic resin, vinylidene chloride resin, polycarbonate resin,
Resins such as polyurethane resin and epoxy resin and various F
A material obtained by conducting a conductive treatment on a plastic material such as RP may be used.

In the method for forming a multi-layer coating film of the present invention, the coated product obtained by applying the above-mentioned base material by the method for forming a multi-layer coating film of the present invention is, for example, an automobile body and an automobile part.

In this case, a degreasing treatment, a chemical conversion treatment or the like is performed in advance, an electrodeposition coating film is formed by a cationic electrodeposition coating material, baked and cured, and an intermediate coating film is formed thereon by an intermediate coating material. preferable. When chipping resistance is required, it is preferable to use a chipping primer instead of the intermediate coating film, or to use a chipping primer in a lower layer of the intermediate coating film.

Here, the term "chipping" means that delamination occurs between the electrodeposition coating film and the intermediate coating film when a bonnet, a roof or the like of an automobile is damaged by stone bounce.

As the electrodeposition paint for forming the electrodeposition coating film, a cationic electrodeposition paint or an anion electrodeposition paint can be used. In this case, it is preferable to use a cationic electrodeposition paint from the viewpoint of corrosion resistance. As the cationic electrodeposition paint, a modified epoxy resin into which an amino group has been introduced and a blocked isocyanate-curable amino-modified epoxy resin-based cationic electrodeposition paint using a blocked polyisocyanate curing agent are used.

The electrodeposition conditions are preferably from 200 to 300
Energize with V for 90-300s, dry film thickness 10-30μm
Set to be.

The film-forming resin constituting the intermediate coating used to form the intermediate coating (lower coating) on the electrodeposition coating is (a) an acrylic resin;
(B) polyester resin, (c) alkyd resin,
(D) a fluorine resin, (e) an epoxy resin, (f) a polyurethane resin, (g) a polyether resin, etc., of which an acrylic resin or a polyester resin is more preferable. These resins can be used alone or in combination of two or more. These resins are also used as a film-forming resin constituting a top coat described later.

The intermediate coating composition contains, in addition to the above-mentioned film-forming resin, a pigment and a solvent, which will be described later for the top coating resin, and various additives as required.

In the method for forming a composite coating film of the present invention, a polyethylene wax is blended with the above intermediate coating material and used.

The above polyethylene wax is 95%
Those having a volume particle diameter of 30 μm or less are preferred. Thereby, the miscibility is improved, and a good coating film appearance is obtained.

Polyethylene wax is supplied by several manufacturers, among which micro-powder type polyethylene wax sold by Clariant under the trade name of Ceridust, especially Seridust 3620
(95% volume particle diameter 14 μm), Seridust 9612A
(95% volume particle diameter 9 μm), Seridust 9610F
(95% volume particle diameter 14 μm), Seridust 9630F
(95% volume particle diameter 14 μm), Ceridust 9202F
(95% volume particle diameter 11 μm), Ceridust 9205F
(95% volume particle diameter of 14 μm) can be suitably used. The compounding amount (addition amount) is 0.5 to 20 parts by mass with respect to 100 parts by mass of the intermediate coating film. If the amount is too small, the miscibility increases, and the incorporation of the overcoat paint described below cannot be prevented. On the other hand, if the amount is too large, the appearance deteriorates.
Here, the “95% volume particle diameter” refers to the particle diameter when the amount of particles in the volume-based particle diameter distribution of the polyethylene wax reaches 95% as calculated cumulatively from the small particle diameter side.

In the present specification, the blending amounts, blending ratios and addition amounts of each component and agent are shown in terms of solid content and ratio unless otherwise specified.

The formation of the intermediate coating film is performed by spray coating,
It is performed by roll painting. When the formed intermediate coating film is baked and dried, 120 to 180 ° C., 20 to 40 m
Perform under the condition of in.

The dry film thickness of the intermediate coating film is 10 to 10
0 μm, more preferably 10 to 50 μm. If the dry film thickness is less than 10 μm, it is difficult to hide the underlayer, while if the dry film thickness exceeds 100 μm, the appearance of the coating film may be poor.

When the above-mentioned chipping primer coating film is formed on the above-mentioned electrodeposition coating film before forming the above-mentioned intermediate coating film, a conventional chipping primer coating material can be used as the chipping primer coating material. This tipping primer paint has high flexibility of the paint film, so it absorbs the impact of stone splash etc. from outside more reliably than the one that only forms the intermediate paint film without forming the chipping primer paint film. can do.

The formation of the above-mentioned chipping primer coating film is as follows.
It can be carried out in the same manner as for the intermediate coating film. When baking and drying the formed chipping primer coating film, the coating is performed at 120 to 180 ° C. for 20 to 40 min.

The dry film thickness of the above-mentioned chipping primer coating is 3 to 30 μm, more preferably 5 to 20 μm. If the dry film thickness is less than 3 μm, it is difficult to obtain chipping resistance. On the other hand, if the dry film thickness exceeds 30 μm, the appearance of the coating film may be poor.

As the overcoat paint for forming the overcoat film, an overcoat solid paint containing a color pigment is used, or an overcoat base paint containing at least one of a glitter pigment or a color pigment and this overcoat paint An overcoated top clear paint having transparency formed on a coating film formed by the base paint is used.

The overcoat paint contains a film-forming resin described below, a pigment and a solvent, and, if necessary, various additives.

Among the topcoat paints, the topcoat clear paint is a paint containing a carboxyl group-containing polymer and an epoxy group-containing polymer described in JP-B-8-19315. It is preferably used from the viewpoint of not disturbing the orientation of the glitter pigment when applied to the top coat base coat containing the glitter pigment on-wet.

The resin for forming a coating film constituting each of the above paints is
In the case of a type having curability, it is used by mixing with a cross-linking agent such as an amino resin, a (block) polyisocyanate compound, an amine-based, a polyamide-based, imidazoles, imidazolines, and a polyvalent carboxylic acid, and is heated or cooled to room temperature. Allows the curing reaction to proceed. It is also possible to use a lacquer type coating film forming resin having no curability and a curable type coating film forming resin in combination.

When the coating film forming resin contains a crosslinking agent,
As the ratio of the coating film forming resin and the crosslinking agent, the coating film forming resin is 90 to 50% by mass, the crosslinking agent is 10 to 50% by mass, and preferably the film forming resin is 85 to 60% by mass. And the cross-linking agent is 15 to 40% by mass. 10 crosslinkers
If the amount is less than 90% by mass, in other words, if the amount of the resin for forming a coating film exceeds 90% by mass, crosslinking in the coating film is not sufficient. On the other hand, when the cross-linking agent exceeds 50% by mass, in other words, when the film-forming resin is less than 50% by mass, the storage stability of the coating material decreases and the curing speed increases, so that the coating film appearance deteriorates. .

As the above-mentioned pigment, at least one of a brilliant pigment and a coloring pigment, and if necessary, an extender pigment can be used.

As the above-mentioned brilliant pigment, preferably, aluminum flake pigment, metal oxide-coated aluminum flake pigment, metal oxide-coated alumina flake pigment, metal oxide-coated silica flake pigment, graphite pigment,
Examples include interference mica pigments, colored mica pigments, metal titanium flake pigments, stainless flake pigments, plate-like iron oxide pigments, phthalocyanine flake pigments, metal-plated glass flake pigments, metal oxide-coated glass flake pigments, and hologram pigments.

As the above-mentioned coloring pigments, organic pigments include azo lake pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, phthalone pigments, and dioxazine pigments. Pigments, quinacridone-based pigments, isoindolinone-based pigments, metal complex pigments, and the like can be mentioned. Inorganic-based pigments include, for example, graphite, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. Examples of the extender include talc, calcium carbonate, precipitated barium sulfate, and silica.

Each coating composition constituting the above top coat, intermediate coat or chipping primer is usually provided in a form in which the components of the above film forming resin or pigment are dissolved or dispersed in a solvent. Any solvent may be used as long as it dissolves or disperses the components, and either or both of an organic solvent and water may be used.

As the organic solvent, those usually used in the field of paints can be mentioned. Examples thereof include hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, cellosolve acetate and butyl cellosolve, and alcohols. When the use of an organic solvent is regulated from the viewpoint of the environment, it is preferable to use water. In this case, an appropriate amount of a hydrophilic organic solvent may be contained.

Each of the paints constituting the top coat, the intermediate coat or the chipping primer is mainly composed of a polyamide wax or polyethylene oxide, which is a lubricating dispersion of an aliphatic amide, in addition to the components described above. Polyethylene wax as a colloidal dispersion, anti-settling agent,
Curing catalyst, ultraviolet absorber, antioxidant, leveling agent,
Surface conditioning agents such as silicone and organic polymers, anti-sagging agents,
Additives such as a thickener, an antifoaming agent, a lubricant, and a crosslinkable polymer particle (microgel) may be appropriately added and contained.

The formation of a coating film using the above-mentioned top coat is carried out by spray coating, roll coating or the like. When the formed top coat is baked and dried, 120 to 180 ° C.
Performed under the conditions of 20 to 40 min.

The dry film thickness of the above-mentioned solid top coating film is 2
0-100 μm is preferred. Further, the dry film thickness of the above-mentioned base coating film is preferably 10 to 100 μm. Also,
The dry film thickness of the above top clear coating film is 20 to 1
00 μm is preferred. If it is less than 10 or 20 μm below the lower limit of the above preferred range of each coating film, it is difficult to hide the base, while if it exceeds 100 μm which is the upper limit of the above preferred range of each coating film, the appearance of the coating film may be poor. is there.

[0046]Painted object  The coated product of the present invention is obtained by the method for forming a multilayer coating film.
Polyethylene wet in the lower wet coating.
The inclusion of water makes the miscibility low
Can prevent the upper coating film from being mixed.
it can. Therefore, the appearance of the formed multilayer coating film is
improves.

[0047]

EXAMPLES Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the compounding amount represents a mass part unless there is particular notice.

[0048]Preparation of substrate to be coated  Dull steel plate (length 300 mm, width 100)
mm and thickness 0.8 mm), and then treated with zinc phosphate
("Surf Dine SD2000", manufactured by Nippon Paint Co., Ltd.)
After a chemical conversion treatment using a cation electrodeposition paint ("Power
-Top U-50 ", manufactured by Nippon Paint Co., Ltd.)
Electrodeposition coating was performed to a thickness of 25 μm.

Next, this dull steel plate coated with electrodeposition was
Baking was performed at 0 ° C. for 30 minutes. Then, in each of the following paints,
The polyethylene wax shown in Table 1 was added to the intermediate coating of each example and to the chipping primers of some Examples and Comparative Examples in an amount shown in Table 1 with respect to 100 parts by weight of the coating film of each coating. Then use glass beads (Toshiba glass beads GB5
03M, manufactured by Toshiba Baroty Co., Ltd.) so that the volume ratio of the paint to the glass beads was approximately 1: 1 and the mixture was stirred by a disper until the polyethylene wax was uniformly dispersed. Thereafter, the glass beads and the paint were separated by a 50-mesh filtration net to obtain a test paint, which was applied in the combinations shown in Table 1. The obtained Examples 1 to 15 and Comparative Examples 1 to
Table 1 shows the appearance of the coating film of each coated product of No. 3.

[0050]

[Table 1] Intermediate paint: Intermediate paint containing organic solvent type acrylic polyester resin and melamine resin ("Olga P-5 Sealer Gray", dry film thickness: 40 μm, manufactured by Nippon Paint Co.) Chipping primer paint: Organic solvent type polyester resin and block poly Intermediate coating chipping paint containing isocyanate (“CP-250”, dry film thickness 10 μm, manufactured by Nippon Paint Co.) Top coat solid paint: Organic solvent type top coat solid paint (“Olga S-61 White”, dry film thickness 40 μm, Nippon Paint) Topcoat base paint: Topcoat glittering paint containing organic solvent type acrylic resin and melamine resin
-95 Silver ", dry film thickness 15 m, manufactured by Nippon Paint Co., Ltd. Top clear paint 1: Clear paint containing acrylic resin and melamine resin (" Superlac O-1 "
30 clear, dry film thickness 35 μm, manufactured by Nippon Paint Co., Ltd. Top clear paint 2: clear paint containing carboxyl group-containing polymer and epoxy group-containing polymer (“Macflow O-520 Clear”, dry film thickness 3)
5 μm, manufactured by Nippon Paint Co., Ltd.) In Table 1, Examples 1 to 15 show the presence or absence of a chipping primer, the presence or absence and amount of polyethylene wax in the used chipping primer, and the amount of polyethylene wax in the intermediate coating. , And the combination conditions are changed for each item of the type of overcoat paint. Further, Comparative Examples 1 to 3 are examples in which polyethylene wax is not blended in the intermediate coating, and further, whether or not a chipping primer not blending polyethylene wax is used or the type of the top coating is combined The conditions were changed.

In Table 1, "0", "1", "5", "15", and "25" in the section of polyethylene wax indicate that the polyethylene compounded as an external number of 100 parts by mass of each paint. Indicates the number of parts by mass of wax. Further, in the item of "drying", what is indicated by W / W means that the coating is performed by wet-on-wet, and the numerical value indicates that the lower layer is formed without coating the upper layer with wet-on-wet. It shows the drying conditions for baking as it is, with the upper row indicating the drying temperature and the lower row indicating the drying time.
"Dry" is the drying condition when the intermediate coating is applied over the tipping primer, and "Dry" is the drying condition when the top coating solid coating or the top coating is applied over the intermediate coating. Is the drying condition of the top-coated base paint, "dry" is the drying condition when the top-coated top clear paint is applied over the top-coated base paint, and "dry" is the drying condition of the top-coated top clear paint.

[0052]Evaluation method  The appearance of the paint film, which is an evaluation item, is based on the finish appearance of the multilayer paint film.
It was visually evaluated in the following three stages.

3: Both the finished coating skin and the coating gloss are good. 2 ... Either the finished coating skin or the coating gloss is poor. 1. Both the finished coating skin and the coating gloss are poor. As described above, in Examples 1 to 15 which were coated products obtained by the method for forming a multilayer coating film of the present invention, the finished appearance of the multilayer coating film was good. However, the intermediate paint 100
In Examples 13 to 15 in which 25 parts by mass of polyethylene wax were blended in parts by mass, the blending amount of polyethylene wax was 1 to
The finished appearance of the multilayer coating film was slightly insufficient as compared with Examples 1 to 12 in which the amount was 15 parts by mass. On the other hand, Comparative Examples 1 to
In No. 3, the finished appearance was not sufficient.

[0054]

In the present invention, since polyethylene wax is contained in the lower wet coating film, the polyethylene wax is unevenly distributed near the surface of the lower coating film during setting, and the upper coating film becomes lower coating film. Prevents the phenomenon of mixing into the film. That is, since the miscibility can be reduced, the appearance of the formed multilayer coating film is improved. In addition, since the coating film obtained by the present invention has the above-mentioned good finished appearance, it is required to have a high finish such as an outer plate or a part of a vehicle such as an automobile and a motorcycle, or an outer surface of a container, a coil coating, and a home appliance industry. It is preferably used in certain fields.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 201/06 201/06 201/08 201/08 F-term (Reference) 4D075 AE12 BB26Z CA04 CA32 CA44 CA48 CB04 CB06 DA06 DB02 DB06 DB07 DB36 DB38 DB40 DB43 DB47 DB48 DB50 DB53 DB61 DC10 DC12 DC13 DC18 DC41 EA07 EA43 EB16 EB22 EB32 EB33 EB35 EB36 EB37 EB38 EB39 EB45 DD07 001 DD02 GA07 KA20 MA14 NA23 NA24 PA12 PA19 PB07 PC02 PC08

Claims (6)

[Claims] 1. A method for forming a multi-layer coating film on a substrate to be coated, wherein a plurality of coating films are coated on a wet basis by wet-on-wet forming a lower coating film using a coating material containing polyethylene wax.
Next, a multi-layer coating film is formed on the lower layer coating film, and the lower layer coating film and the multi-layer coating film are simultaneously baked and cured. 2. The method according to claim 1, wherein the polyethylene wax is blended in an amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the lower layer side coating film. 3. The method according to claim 1, wherein the polyethylene wax has a 95% volume particle diameter of 30 μm or less. 4. The lower-layer-side coating film comprises: (1) a multilayer coating film having an overcoated solid coating film formed on the intermediate coating film; and (2) an intermediate coating film formed on the chipping primer. A multilayer coating film in which a top coating solid coating film is formed on the intermediate coating film,
(3) a multi-layer coating film in which a top coating film is formed on the intermediate coating film and a top clear coating film is further formed on the top coating film, or (4) an intermediate coating film on the chipping primer. To form a top coat base coat on the intermediate coat, and further a top coat clear coat formed on the top coat base coat. The coating film according to claim 1, wherein the coating film is at least one layer other than the uppermost layer.
The method for forming a multilayer coating film according to the above item. 5. The method according to claim 4, wherein the top clear coating composition used for forming the top clear coating film contains a carboxyl group-containing polymer and an epoxy group-containing polymer. Layer coating method. 6. A coated article coated by the method for forming a multilayer coating film according to claim 1. Description: