WO1998020984A1

WO1998020984A1 - Method of forming multiple-layered coating film

Info

Publication number: WO1998020984A1
Application number: PCT/JP1996/003278
Authority: WO
Inventors: Shigeru Nakamura; Naruhito Ueno
Original assignee: Kansai Paint Co., Ltd.
Priority date: 1996-11-08
Filing date: 1996-11-08
Publication date: 1998-05-22
Also published as: KR20000053036A; GB2334222B; WO1998020984A9; CA2277830C; KR100435941B1; GB2334222A; GB9910128D0; CA2277830A1

Abstract

A method of forming a multiple-layered coating film by successively applying an undercoat (A), intermediate coat (B) and a top coat (C), wherein: (1) the intermediate coat (B) uses a liquid thermosetting resin paint which contains aluminum powder (0.1 to 30 parts weight) and titanium oxide pigment (1 to 200 parts weight) per a thermosetting resin composition (100 parts weight) and which has a concealing film thickness of 25 νm, (2) the top coat (C) uses a solid color paint, a metallic paint or a paint of interference pattern, and (3) the top coat (C) is applied after a film of the intermediate coat (B) is heated to be cured. According to the method, a film of the intermediate coat can be made thin and a multiple-layered coating film having a good smoothness can be formed.

Description

Description Method for forming multilayer coating film

Technical field

In the present invention, when a base coat, an intermediate coat, and a top coat are sequentially applied to form a multi-layered coat, an intermediate coat with a specific pigment composition is used, and after the coat is cured, the top coat is applied. Accordingly, the present invention relates to a method for forming a multi-layer coating film which can make the intermediate coating film thinner without deteriorating the coating film performance and has excellent smoothness.

Background art

A method for forming a multilayer coating film by sequentially applying a base coat (such as an electrodeposition paint), an intermediate coat, and a top coat is known. However, with regard to the intermediate coating, it is usually necessary to apply it to a thick film of 30 m or more (as a cured coating) in order to hide the lower layer and maintain the coating performance. Therefore, there is a demand for reducing the coating cost of the multilayer coating film by reducing the thickness of the intermediate coating film without lowering the concealability and the coating film performance.

The present inventors have conducted intensive studies to solve these problems, and as a result, in the step of sequentially applying a base coat, an intermediate coat, and a top coat, both components of aluminum powder and titanium oxide pigment were used as the intermediate coat. If a thermosetting paint is used and the topcoat is applied after the middlecoat has been cured, the basecoat concealment of the middlecoat is improved and the chipping resistance is also improved. It has been found that it is possible to reduce the film thickness, and it is also found that the smoothness of the overcoated surface is improved, thereby completing the present invention.

Disclosure of the invention Thus, the present invention provides a method for forming a multilayer coating film by sequentially applying a base coat (A), an intermediate coat (B) and a top coat (C) on a substrate,

(1) The intermediate coating material (B) contains 0.1 to 30 parts by weight of aluminum powder and 100 to 200 parts by weight of a titanium oxide pigment per 100 parts by weight of the thermosetting resin composition. Is less than 25 zm.

(2) A solid color paint, a metallic paint or an interference pattern paint is used as the top coat (C), and

(3) After heat-curing the coating of the intermediate coating (B), apply the top coating (C).

It is another object of the present invention to provide a method for forming a multilayer coating film.

Hereinafter, the method for forming a multilayer coating film of the present invention (hereinafter, referred to as “the present method”) will be described in more detail.

Undercoat paint (A):

The undercoat paint (A) is used to directly apply to a substrate made of metal, plastic, or the like, that is, an article to be coated, and to provide protection, adhesion, and the like. There is no particular limitation as long as it meets the requirements, and any usual primer can be used. As an object to which the undercoat can be applied, an automobile outer panel is particularly suitable. In general, it is desirable that the object to be coated is appropriately subjected to pre-removal, cleaning, chemical conversion treatment, and the like. When the object to be coated has a conductive metal back or surface, a cationic electrodeposition coating is suitable as the undercoat. Cationic electrodeposition paints can be crosslinked as needed with aqueous solutions or dispersions of salts of cationic polymer compounds. Known per se, in which an agent, a pigment and various additives are blended, can be used, and the type thereof is not particularly limited. Examples of the cationic polymer compound include compounds obtained by introducing a cationic group such as an amino group into an acrylic resin or an epoxy resin having a crosslinkable functional group, which is neutralized with an organic acid or an inorganic acid. By doing so, it can be made water-soluble or water-dispersible. As a cross-linking agent for curing these polymer compounds, block polyisocyanate compounds, alicyclic epoxy resins, and the like can be suitably used.

The electrodeposition coating is performed by immersing a metal coating object such as a car outer part or a bumper as a cathode in the bath of the cationic electrodeposition coating material, and passing an electric current between the anode and the anode under ordinary conditions to form the coating. It can be carried out by depositing a paint on the coating. The thickness of the formed electrodeposition coating film is usually preferably in the range of 10 to 40 m, based on the cured coating film, and the coating film is formed at a temperature of about 140 to about 220 ° C at about 1 ° C. Crosslinking and curing can be performed by heating from 0 to about 40 minutes. In this method, it is preferable to apply the intermediate coating after curing the electrodeposition coating film. However, in some cases, the intermediate coating may be applied in an uncured state.

Intermediate paint (B):

In the present method, the intermediate coating (B) contains 0.1 to 30 parts by weight of aluminum powder and 1 to 200 parts by weight of titanium oxide pigment per 100 parts by weight of the thermosetting resin composition. Use a liquid thermosetting paint with a film concealment thickness of 25 // m or less.

By using aluminum powder and titanium oxide pigment together in the intermediate coating (B), the hiding power of the coating film is increased, and the cured coating film has a thickness of 25 // m or less, especially a thin film of 10 to 25 m. Even if there is enough, conceal the base material (prime-coated surface) This makes it possible to achieve a thinner intermediate coating film.

The thermosetting resin composition used as a vehicle component in the intermediate coating composition (B) basically comprises a base resin and a cross-linking agent or a self-cross-linking curable resin. Examples include an acrylic resin, a polyester resin, and an alkyd resin having two or more crosslinkable functional groups such as a hydroxyl group, an epoxy group, an isocyanate group, and a carboxyl group in one molecule. For example, an amino resin such as a melamine resin or a urea resin, a polyisocyanate compound which may be blocked, or a carboxyl group-containing compound may be used. Examples of the self-crosslinking curing resin include a resin containing two or more alkoxysilane groups in one molecule, a resin containing a carboxyl group and a hydroxyl group in one molecule, and a resin containing a hydroxyl group in one molecule. And a resin containing an isocyanate group which may be used. These resins are based on, for example, a vinyl resin, an acrylic resin, a polyester resin, a urethane resin and the like.

As the aluminum powder to be blended in the intermediate coating (B), aluminum powder having an average particle size of generally 40 // m or less, preferably 10 z ^ rn or less, more preferably 3 to 7 zm is preferred. When a fine powder having an average particle diameter of 10 m or less is used, the formed intermediate coating film itself has no glitter (brightness). Here, the “average particle size” refers to the median size measured by a laser diffraction scattering method (LA-500). The main component of this aluminum powder is metallic aluminum, but its surface may be treated with a silane coupling agent or the like. Further, as the titanium oxide pigment to be blended in the intermediate coating (B) according to the present method, a pigment known per se as a coating pigment can be used, and its average particle size is usually preferably 5 im or less. . Further, the surface of the titanium oxide pigment may be treated with alumina-silica force or the like. The amount of the aluminum powder and the titanium oxide pigment is 0.1 to 30 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 100 to 100 parts by weight (as solid content) of the thermosetting resin composition. The amount can be in the range of 1 to 7 parts by weight, and the titanium oxide pigment can be in the range of 1 to 200 parts by weight, preferably 40 to 160 parts by weight, more preferably 80 to 120 parts by weight. Further, it is preferable that the aluminum powder is used in an amount of 1 to 15 parts by weight, preferably 1.5 to 10 parts by weight, more preferably 2 to 7 parts by weight, per 100 parts by weight of the titanium oxide pigment.

It is essential that the intermediate coating (B) used in the present method contains both aluminum powder and a titanium oxide pigment, and the total amount of both pigments is formed using the coating (B). The amount can be set so that the concealed film thickness of the coating film is 25 / m or less—in particular, 10 to 25 m or less (as a cured coating film). Here, the “concealment film thickness” is the minimum film thickness at which the color of the substrate (surface to be coated) cannot be recognized through the coating film, and specifically, on a black-and-white checkered plate. This is the minimum film thickness that makes it impossible for the naked eye to distinguish between black and white through a painted film. In this method, by combining both the aluminum powder and the titanium oxide pigment with the intermediate coating (B) in a specific amount, the coating thickness of the coating film can be reduced to 25 / m or less. Noh. In other words, it is possible to sufficiently cover the color of the substrate even with a thin film of 25 / m or less. A thin film that lacks either of these components Is difficult to conceal.

The intermediate coating (B) can be prepared by mixing and dispersing the thermosetting resin composition, aluminum powder, and titanium oxide pigment components in a solvent such as an organic solvent and / or water. If necessary, a coloring pigment other than the aluminum powder and the titanium oxide pigment, an extender pigment, an anti-settling agent, and the like can be appropriately blended.

The intermediate coating material (B) is applied to the cured or uncured undercoat surface by a method such as electrostatic coating, air spray, or airless spray. It is preferable to paint with a film thickness in the range of 5 // m.

In this method, the coating of the intermediate coating (B) is heated and cured, and then the top coating (C) described below is applied. The heat curing of the coating film of the intermediate coating material (B) can be performed, for example, by heating the coating film at a temperature of about 140 to about 200 ° C. for about 10 to about 40 minutes. .

Top coating (C):

According to the present invention, as a top coat, a solid color (colored) paint (C-1), a metallic paint (C-12), or a chitarashi pattern paint is applied on the cured coating surface of the intermediate coat (B). (C-13) is painted. It is desirable that all of these top coatings are of the thermosetting type.

First, the solid color paint (C-11) is preferably a liquid thermosetting paint mainly composed of a thermosetting resin composition and a coloring pigment-substantially a metallic pigment or an interference color. Those containing no pigment are used. The thermosetting resin composition used in the coloring paint (C-11) basically comprises a base resin and a crosslinking agent or a self-crosslinking curable resin. Examples of the fat include an acryl resin having two or more crosslinkable functional groups such as a hydroxyl group, an epoxy group, an isocyanate group, and a carboxyl group in one molecule, a polyester resin, and an alkyd resin. Examples thereof include amino resins such as melamine resins and urea resins, polyisocyanate compounds which may be blocked, and carboxyl group-containing compounds. Examples of the self-crosslinking curable resin include a resin containing two or more alkoxysilane groups in one molecule, a resin containing a carboxyl group and a hydroxyl group in one molecule, and a resin containing a hydroxyl group and a hydroxyl group in one molecule. And the like. These resins include a resin containing an isocyanate group which may be treated, and these resins are based on, for example, a vinyl resin, an acrylic resin, a polyester resin, a urethane resin and the like.

Coloring pigments that can be incorporated into the solid color paint (C-11) are substantially free of meso pigments and interference pigments and can be added to the multi-layer coating film formed by the method of the present invention. It is a component for imparting toning, and may be an ordinary organic or inorganic coloring pigment for paint. Specifically, for example, inorganic pigments such as titanium oxide, zinc oxide, carbon black, cadmium red, molybdenum red, chrome yellow, chromium oxide, Prussian blue, and cobalt blue; azo pigments, phthalocyanine pigments, quinacrine Organic pigments such as don pigments, isoindolin pigments, sullen pigments, and perylene pigments are exemplified. Generally, it is desirable that these pigments have an average particle size of 5 m or less.

The blending amount of these coloring pigments can be arbitrarily selected depending on the coloring power of the pigment itself and the purpose, but is generally 0.5 to 200 parts by weight, preferably 100 to 100 parts by weight of the thermosetting resin composition. Is within the range of 1 to 150 parts by weight and The amount can be set so that the concealed film thickness of the formed coating film is 50 zm or less, particularly 40 zm or less in the cured coating film.

The solid color paint (C-11) can be prepared by mixing and dispersing the above components with a solvent such as an organic solvent and / or water. The paint may contain an extender pigment, if necessary. An antisettling agent and the like can be appropriately added.

As the metallic paint (C-12), preferably, a thermosetting resin composition as described above for the solid color paint (C-11) and a liquid thermosetting paint mainly containing a metallic pigment are used. Can be used. Metallic pigments to be added to the metallic paint are flake-like metal or metal oxide particle pigments having a glittering glitter. Specifically, for example, aluminum flake, mica-like Rukoto _c these scaly pigment particles such as iron oxide is generally 1 0 / m or more, preferably. 10 to 50 / m, more preferably having a mean particle size in the range of. 15 to 40 m Can be. The amount of these metallic pigments is generally in the range of 0.1 to 20 parts by weight, preferably in the range of 3 to 10 parts by weight, per 100 parts by weight of the thermosetting resin composition. The amount can be set so that the concealed film thickness of the coating film is 50 m or less, particularly 30 // m or less in the cured coating film. Metallic paint (C-12) can be prepared by mixing and dispersing the above components with an organic solvent and a solvent such as Z or water. The paint may contain an extender pigment, a coloring pigment, An antisettling agent and the like can be appropriately combined. Since the metallic paint (C-12) contains a metallic pigment having a relatively large particle size, the coating film itself of the metallic paint exhibits a glittering glitter. As the interference pattern paint (C-13), it is preferable to use the liquid thermosetting paint mainly containing the thermosetting resin composition and the interference pigment as described above for the solid color paint (C-11). Can be. As an interference pigment to be blended in the interference pattern paint, scaly mica whose surface is coated with a metal oxide such as titanium oxide or iron oxide, so-called interference force is particularly preferable. The coating thickness of the metal oxide at this interference force is preferably at least 200 nm based on the optical thickness and at least 80 nm based on the geometric thickness. If the thickness is smaller than this, the interference effect due to light generally decreases, which is not preferable. The interference pigments can have an average particle size of usually at least 10 zm, preferably from 10 to 50 m, more preferably from 15 to 40 m.

The compounding amount of the interference pigment can be generally 1 to 100 parts by weight, preferably 5 to 50 parts by weight, per 100 parts by weight of the thermosetting resin composition.

The interference pattern paint (C-13) can be prepared by mixing and dispersing the above components with an organic solvent and a solvent such as water or water. If necessary, the paint may contain a coloring pigment, a metallic paint, or the like. Pigments, extenders, anti-settling agents, and the like can be appropriately compounded.

The above-mentioned top coat (C) is applied to the heat-cured intermediate coating surface by electrostatic coating. Air spray, airless spray, etc., based on the cured coating film, 10-60 / zm, especially 20- It is preferable to paint with a film thickness in the range of 35 // m.

The coating film of the top coat (C) can be cured, for example, by heating at a temperature of about 120 to about 180 ° C for about 10 to 40 minutes. Clear paint (D):

In the present method, a clear paint (D) may be applied on the coated surface of the overcoat paint (C) formed as described above, if necessary. The clear paint (D) can be applied on the coated surface of the cured or uncured top coat (C) formed as described above.

The clear paint (D) preferably contains a thermosetting resin composition and a solvent as main components, and, if necessary, a color pigment or a metallic pigment to such an extent that the transparency of the coating film is not impaired. Liquid paints containing an interference pigment, an ultraviolet absorber, and other paint additives can be used.

The thermosetting resin composition basically comprises a base resin and a crosslinking agent, or a self-crosslinking curable resin, wherein the base resin includes, for example, a hydroxyl group, an epoxy group, an isocyanate group, and a carboxyl group. Acrylic resins, polyester resins, alkyd resins, urethane resins and the like having two or more crosslinkable functional groups in one molecule such as a group are exemplified. Resins, urea resins, polyiso- nate compounds which may be blocked, carboxyl group-containing compounds, and the like. Further, examples of the self-crosslinking curable resin include a resin containing two or more alkoxysilane groups in one molecule, a resin containing a carboxyl group and a hydroxyl group in one molecule, and a resin blocked with a hydroxyl group in one molecule. And a resin containing an isocyanate group which may be included. These resins are based on, for example, vinyl resin, acrylic resin, polyester resin, urethane resin and the like. As the solvent, an organic solvent and z or water can be used, and the above-mentioned thermosetting resin composition and other components are dissolved or dispersed in these solvents to prepare a clear paint (D). be able to.

The clear paint (D) can be applied to the uncured or hardened top coat (C) formed as described above by a method such as electrostatic coating, air spray, or airless spray. The film thickness is preferably in the range of 10 to 60 / m, particularly 20 to 50m, based on the cured coating film. The clear paint (D) coating film itself can be crosslinked and cured at a temperature of about 120 to about 180 ° C for about 10 to 40 minutes.

According to the multilayer coating film forming method of the present invention described above, for example, the following effects can be obtained.

(1) The thickness of the intermediate coating film can be made thinner than usual (normally 30 m or more) (25 m or less, preferably 10 to 20 m), so that the cost of the entire multilayer coating film can be reduced. it can.

(2) Since the top coat is applied after the middle coat is cured by heating, the top coat has excellent smoothness.

(3) The middle coat paint is excellent in concealment of the base, so even when applied with a thin film. The color stability of the top coat is good, and the color design of the top coat can be freely changed according to the purpose. be able to.

(4) The formed multi-layer coating film has excellent resistance to chipping.

Example

Hereinafter, the method of the present invention will be described more specifically with reference to Examples and Comparative Examples.

I. Sample

(1) Cationic electrodeposition paint (A)

“Electron 9400 HBJ (manufactured by Kansai Paint Co., Ltd. POXY resin polyamine · block polyisocyanate compound)

(2) Intermediate coating (B)

An organic solvent-type paint comprising a polyester resin, a melamine resin, a fine aluminum powder and a titanium oxide pigment in the proportions shown in Table 1 below. The amounts of each component shown in Table 1 are weight solids ratios.

table 1

(* 1): Polyester resin based on phthalic anhydride / hexahydrophthalic anhydride (number average molecular weight: about 400, hydroxyl value: 82, acid value: 7).

(* 2) _: Uban 2 8—60 (Mitsui Toatsu Chemicals, trade name)

(* 3): K-980 (made by Asahi Kasei, trade name), average particle size 5-6 τ (* 4) _: Titanium JR701 (made by Teikoku Chemical Co., trade name), average particle size: 0. 3 ~

0.6 m

(* 5): KNO-W iron oxide (trade name, manufactured by Toda Kogyo Co.), average particle size 0.2 ~

0.5〃m (red solid color pigment)

(* 6): The minimum film thickness (im) at which black-and-white discrimination was impossible with the naked eye was measured through a coating film coated on a checkered black-and-white plate. (3) Top coat (C)

An organic solvent-type paint comprising an acryl resin, a melamine resin and a coloring pigment or a metallic pigment in a ratio shown in Table 2 below. The amount of each component shown in Table 2 is a weight solids ratio.

Table 2

(* 7): A methylmethacrylate acrylic resin with a number average molecular weight of about 20

00, hydroxyl value 70, acid value 8

(* 8): Uban 28-60 (Mitsui Toatsu Chemicals, trade name)

(* 9): Titanium CR 93 (made by Ishihara Sangyo, trade name)

(* 10): Carbon FW200 (made by DE GU SSA, trade name)

(* 11): Nexter Highlight Blue (manufactured by Marl, trade name, average particle size 14 ~; L 8 zm)

(5) Clear paint (D)

"Magiclon Clear" (manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / melamine resin, organic solvent type).

Π. Examples and Comparative Examples Using the above sample, coating was performed according to the coating process shown in Table 3, and the coating was heated and cured to form a multilayer coating film. Table 3 also shows the results of performance tests of the multilayer coating film.

Table 3

The degreased and zinc phosphate treated steel sheet was coated with a cationic electrodeposition paint (A) by a conventional method so as to have a thickness of 20 m. 30 minutes heating at C To cure the coating. The intermediate coatings (B-1) to (B-5) were coated on the electrodeposition coated surface so as to have a film thickness of 25 μη, and were heated at 140 ° C for 30 minutes in Examples 1 to 3 and Comparative Examples 1 and 2. Then, the intermediate coating film was cured, while Comparative Example 3 was left at room temperature for 5 minutes. Next, the top coat (C-1) to (C-3) was applied to the intermediate coat using a mini-bell type rotary electrostatic coater, with a discharge rate of 150 cc, a rotation speed of 50,000 rpm, and a shedding pressure of 1 kgcm. ^{2. The} paint was applied at a gun distance of 30 cm, a booth temperature of 20 ° C, and a bus humidity of 75%. The coating thickness was 15-25 / m. The overcoat film was left in the booth for 5 minutes, and then heated in Example 1 and Comparative Examples 1 and 3 at 140 ° C. for 30 minutes to cure the overcoat (C). On the other hand, in Examples 2 and 3 and Comparative Example 2, the clear paint (D) was applied to the surface of the uncured top coat (C) using a mini-bell type rotary electrostatic coating machine, and the discharge rate was 300 cc and the rotation speed was The paint was applied at 40000 rpm, shaving pressure 5 kg / cm ² , gun distance 30 cm, booth temperature 20 ° C, and bus humidity 75%. The coating thickness was 45-50 / zm. After coating, leave it at room temperature for 3 minutes, then heat it in a hot air circulating drying oven at 140 ° C for 30 minutes to obtain a two-layer coating consisting of the above top coat (C) and clear paint (D). Were simultaneously cured.

The coating film performance test method and evaluation criteria are as follows.

Smoothness: Visual evaluation. 〇: good, △: slight skin blemishes, X: marked skin blemishes Finish appearance: color unevenness, concealability were visually evaluated.良好 is good, △ is slightly good,

X is bad.

Metallic feeling: Visual evaluation for metallic unevenness.良好 is good, △ is slightly good, X is bad.

Chipping resistance: A grabber meter (manufactured by Q Panel) is used as a testing machine. Then, 500 g of No. 7 crushed stone is sprayed at an angle of 45 ° with respect to the coated surface at 20 ° C with an air pressure of 3 kg / cm ² to impact the coated film. Next, an adhesive tape is applied to the coated surface, and after the tape is rapidly peeled, the state of peeling of the coating film around the wound due to the impact is examined.

：: No or almost no peeling of the coating film around the wound was observed.

Δ: Peeling of the coating film is clearly observed around the wound,

X: The coating film peeling is remarkably observed around the wound.

Ten

Fifteen

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Claims

The scope of the claims

1. A method of forming a multilayer coating film by sequentially applying a base coat (A), a middle coat (B) and a top coat (C) on a substrate,

(1) The intermediate coating (B) contains 0.1 to 30 parts by weight of aluminum powder and 1 to 200 parts by weight of titanium oxide pigment per 100 parts by weight of the thermosetting resin composition, and conceals the coating film. Use a liquid thermosetting paint with a thickness of 25 m or less,

(2) Solid paint, metallic paint or interference paint is used as the top coat (C), and

A method for forming a multilayer coating film, comprising:

2. The method according to claim 1, wherein the aluminum powder contained in the intermediate coating (B) has an average particle size of 40 zm or less.

3. The method according to claim 2, wherein the aluminum powder has an average particle size of 10 / m or less.

4. The method according to claim 1, wherein the titanium oxide pigment contained in the intermediate coating composition (B) has an average particle size of 5 / m or less.

5. The method according to claim 1, wherein the intermediate coating composition (B) contains 1 to 7 parts by weight of luminium powder and 80 to 120 parts by weight of a titanium oxide pigment per 100 parts by weight of the thermosetting resin composition.

6. The method according to claim 1, wherein the intermediate coating (B) contains 1 to 15 parts by weight of aluminum powder per 100 parts by weight of the titanium oxide pigment.