WO1998020984A9

WO1998020984A9 - Method of forming multiple-layered coating film

Info

Publication number: WO1998020984A9
Application number: PCT/JP1996/003278
Authority: WO
Inventors: Shigeru Nakamura; Naruhito Ueno
Original assignee: Kansai Paint Co Ltd; Shigeru Nakamura; Naruhito Ueno
Priority date: 1996-11-08
Filing date: 1996-11-08
Publication date: 1999-07-22
Also published as: GB2334222B; WO1998020984A1; CA2277830A1; GB2334222A; KR20000053036A; GB9910128D0; KR100435941B1; CA2277830C

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 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 entire 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, a middle coat and a top coat, both components of aluminum powder and titanium oxide pigment were used as the middle 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 resistance to chipping is also improved, resulting in an improved middlecoat. It has been found that it is possible to reduce the film thickness, and it is also found that the smoothness of the top coat is improved, and the present invention has been completed.

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) As the intermediate coating (B), 0.1 to 30 parts by weight of aluminum powder and titanium oxide pigment per 100 parts by weight of the thermosetting resin composition

Use a liquid thermosetting paint containing 1 to 200 parts by weight and having a coating thickness of 25 / m or less,

(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 those 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. Thus, it can be made water-soluble or water-dispersed. As a cross-linking agent for curing these polymer compounds, block polyisocyanate compounds, alicyclic epoxy resins, and the like can be suitably used.

In electrodeposition coating, a metal object to be coated such as an automobile outer panel or a bumper is immersed in a bath of the cationic electrodeposition coating material as a cathode, and electricity is passed between the anode and an anode under ordinary conditions to perform 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 about 140 to about 220 ° C. Crosslinking and curing can be achieved by heating for about 10 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 this 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 the aluminum powder and the 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 10 to 25. Enough to conceal the substrate (prime-coated surface) This makes it possible to reduce the thickness of the 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 of the crosslinking resin include an acrylic resin, a polyester resin, and an alkyd resin having at least two crosslinkable functional groups such as a hydroxyl group, an epoxy group, an isocyanate group, and a carboxyl group in one molecule. Amino resins such as melamine resin and urea resin, polysocyanate compounds which may be blocked, and carboxyl group-containing compounds are used. 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 in one molecule. And the like. These resins include an isocyanate group which may be used, and these resins are based on, for example, vinyl resin, acrylic resin, polyester resin, urethane resin and the like.

As the aluminum powder to be blended with the intermediate coating (B), an aluminum powder having an average particle size of generally 40 μm or less, preferably 10 μm or less, more preferably 3 to 7 m is suitable. In particular, when a fine powder having an average particle size of 10 m or less is used, the formed intermediate coating film itself has no glitter (brightness). Here, “average particle size” refers to the median diameter measured by the laser diffraction / diffraction 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 into the intermediate coating composition (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 m or less. . Further, the surface of the titanium oxide pigment may be treated with alumina-silica force or the like. The mixing 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, per 100 parts by weight (as a solid content) of the thermosetting resin composition. Parts by weight, more preferably in the range of 1 to 7 parts by weight, and the titanium oxide pigment is 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. It can be in the range of parts by weight. Further, the aluminum powder is preferably 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.

The intermediate coating (B) used in the present method must contain both the aluminum powder and the titanium oxide pigment, and the total amount of these pigments is determined 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, both the aluminum powder and the titanium oxide pigment are combined with the intermediate coating (B) in a specific amount, so that the concealed film thickness of the coating film can be reduced to 25 / m or less. It is now possible. In other words, it is possible to sufficiently hide the color of the substrate even with a thin film of 25 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 each of the above-mentioned thermosetting resin composition, aluminum powder, and titanium oxide pigment in an organic solvent and a solvent such as water 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 (B) is applied to a cured or uncured undercoat surface by a method such as electrostatic coating, air spray, airless spray, etc., based on the cured coating film, to a thickness of 25 μm or less, especially 10 to 2 μm. It is preferred 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 an interference pattern paint is provided 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-1) is preferably a liquid thermosetting paint mainly composed of a thermosetting resin composition and a coloring pigment, and is substantially a metallic pigment or an interference. Those containing no color 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, an alkyd resin, and the like. Examples of the agent 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 those containing an isocyanate group which may be cured. These resins are based on, for example, vinyl resins, acrylic resins, polyester resins, urethane resins and the like.

The coloring pigments that can be blended with the solid color paint (C-11) are substantially free of metallic pigments and interference pigments and can be used for solid toning in the multilayer coating film formed by the method of the present invention. And an organic or inorganic coloring pigment for ordinary paints. Specifically, for example, inorganic pigments such as titanium oxide, zinc oxide, carbon black, cadmium red, molybdenum red, chrome yellow, chromium oxide, Prussian blue, Cono-Cult blue; azo pigments, phthalocyanine pigments, quinacridones Organic pigments such as 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 m or less in the cured coating film.

The solid color paint (C-11) can be prepared by mixing and dispersing the above-mentioned components with an organic solvent and a solvent such as water or water. An antisettling agent and the like can be appropriately added.

As the metallic paint (C-12), preferably, a liquid thermosetting resin mainly composed of a thermosetting resin composition and a metallic pigment as described above for the solid color paint (C-11) Paint can be used. Metallic pigments to be blended into the metallic paint are scaly metal or metal oxide particle pigments having a glittering glitter. Specifically, for example, aluminum flake, mica-like _c these scaly pigment particles such as iron oxide is generally 10 / m or more, Rukoto preferably. 10 to 50 ^ m. more preferably that having a mean particle size in the range of. 15 to 40 m it can. The amount of these metallic pigments is generally in the range of 0.1 to 20 parts by weight, preferably 3 to 10 parts by weight, per 100 parts by weight of the thermosetting resin composition. Of the cured coating film can be 50 zm or less, particularly 30 m or less. The metallic paint (C-12) can be prepared by mixing and dispersing the above components with a solvent such as an organic solvent and / or water. The paint may include an extender pigment and a coloring pigment as necessary. An anti-settling 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 paint film itself of the metallic paint exhibits a glittering glitter. As the pattern paint (C-3), preferably, a liquid thermosetting paint mainly composed of the thermosetting resin composition and the interference pigment as described above for the solid color paint (C-11) is used. be able to. 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 pigment may have an average particle size of usually at least 10 m, preferably 10 to 50 m, more preferably 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 Z 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 middle coat surface by electrostatic coating, air spray, airless spray, etc., based on the cured coating film, and the coating is 10-60 / m, especially 20-35. It is preferable to apply a coating having a thickness in the range of / 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 coating (D) preferably contains a thermosetting resin composition and a solvent as main components, and further, if necessary, a coloring pigment, a metallic pigment, or the like, to such an extent that the transparency of the coating film is not impaired. A liquid paint containing an interference pigment, an ultraviolet absorber, and other additives for coating 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 resin, polyester resin, alkyd resin, urethane resin and the like having two or more crosslinkable functional groups in one molecule, such as a carboxylic acid group, are exemplified.Examples of the crosslinking agent include melamine resin and urea. Examples thereof include resins, polyisocyanate compounds which may be blocked, and carboxyl group-containing compounds. 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 coating (D) can be applied to the uncured or hardened top coating (C) formed as described above by a method such as electrostatic coating, air spray, or airless spray. The thickness is preferably in the range of 10 to 60 m, especially 20 to 50 m, based on the cured coating film. The coating film of the clear coating material (D) 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 (less than 25 / m, preferably 10 to 20 zm) than before (usually 30 / m or more). 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 has excellent base concealment properties, 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. fiA fee

(1) Cationic electrodeposition paint (A)

"Electron 9400HBJ (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): Phthalic anhydride / hexahydro phthalic anhydride polyester tree (number average molecular weight: about 4000, hydroxyl value: 82, acid value: 7).

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

(* 3): K-9800 (trade name, manufactured by Asahi Kasei), average particle size 5-6 nm (* 4): Titanium JR701 (trade name, manufactured by Teikoku Chemical), average particle size 0.3-

0.6 // m

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

0.5 im (red solid color pigment)

(* 6): The minimum film thickness (/ m) 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 methyl methacrylate 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 DEGU SSA, trade name)

(* 11): Exterior Highlight Blue (made by Marl, trade name, average particle size 14 ~; L8 / m)

(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 the performance test of the multilayer coating film.o

Table 3

Cathode electrodeposition paint (A) is electrodeposited on a degreased and zinc phosphate treated steel sheet to a film thickness of 20 zm using a conventional method, and heated at 170 ° C for 30 minutes. To cure the coating. The intermediate coatings (B-1) to (B-5) were applied to the electrodeposition coated surface so as to have a film thickness of 25 m. In Examples 1 to 3 and Comparative Examples 1 and 2, heating was performed at 140 ° C for 30 minutes. 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-13) was applied to the intermediate coated surface using a mini-bell type rotary electrostatic coating machine, discharge rate 150 cc, rotation speed 50000 rpm, shaving pressure 1 kgcm ² , gun distance 30 cm. Painted at a booth temperature of 20 ° C and a booth humidity of 75%. The coating thickness was 15 to 25 m. The top coat 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 top coat (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 coater, and the discharge rate was 300 cc and the number of revolutions was 40,000. r pm, shaving pressure 5 kgcm ² , gun distance 30 cm, booth temperature 20 ° C, paint humidity 75%. The coating thickness was 45-50 m. After coating, leave it at room temperature for 3 minutes, and then heat it at 140 ° C for 30 minutes in a hot air circulating drying oven to form a two-layer coating consisting of the above top coat (C) and clear paint (D). It was cured at the same time.

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: Visually evaluated for metallic unevenness.良好 is good, △ is slightly good, X is bad.

Chipping resistance: Use a grabber meter meter (Q panel) as a testing machine. Then, 500 g of No. 7 crushed stone is sprayed at an angle of 45 ° with respect to the coating surface and an air pressure of S kgZcm ² at 20 ° C to give an impact to the coating 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

20

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

(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 zm or less.

5. The method according to claim 1, wherein the intermediate coating composition (B) contains 1 to 7 parts by weight of aluminum 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 titanium oxide pigment.

7. The method according to claim 1, wherein the concealed film thickness of the coating film of the intermediate coating material (B) is 10 to 25 m or less.

8. The method according to claim 1, wherein the intermediate coating (B) is applied to a thickness of 10 to 25 m based on the cured coating film.

9. The method of claim 1 wherein the coating of the intermediate coating (B) is cured by heating to a temperature of about 140 to about 200 ° C.

10. The method according to claim 1, wherein the top coat (C) is applied to a thickness of 10 to 60 m based on the cured coating film.

1 1. The method of claim 1 wherein the topcoat (C) coating is cured by heating to a temperature of about 120 to about 180 ° C.

12. The method according to claim 1, wherein the undercoat paint (A) is a cationic electrodeposition paint.

13. The method according to claim 1, wherein the clear paint (D) is further applied on the coated surface of the top coat (C).