JP2000017205A - Paint composition, forming of coating film and painted item - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition capable of forming a coating film which maintains concealment with keeping chromaticness by making the composition contain a vehicle, a bright pigment and/or an aluminum flake having an average diameter of not more than a specific value and relative surface area of not less than a specific value. SOLUTION: A paint composition contains a vehicle which comprises 90-50 wt.% of a film forming resin and 10-50 wt.% of a crosslinking agent, 0.01-10 wt.%, per 100 pts.wt. of a solid of the paint, of a bright pigment and/or a coloring agent, a concealing agent such as a fine aluminum flake having an average diameter of not more than 6 μm and BET relative surface area of not less than 52,000 cm2/g and if necessary an extender filler, a precipitation preventing agent, a catalyst for hardening, an ultraviolet absorber, an antioxidant and the like. The film forming resin to be used includes an acrylic resin having a number average molecular weight of 1,800-100,000, a polyester resin having a number average molecular weight of 200-10,000 and the crosslinking agent includes an amino resin such as an alkyletherified melamine resin and the like, a blocked isocyanate compound and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition used for a coating applied to an automobile body, a method of forming a coating, and a coated article. In particular, it relates to the improvement of the concealing property of a coating film.

[0002]

2. Description of the Related Art A coating applied to a car body or the like of an automobile is composed of three layers of an electrodeposition coating film, an intermediate coating film and a top coating film, or a laminate comprising two layers of an electrodeposition coating film and a top coating film. Consisting of a coating film,
As the overcoat, a glitter coating containing a glitter pigment such as an aluminum pigment is used. Glitter coatings consist of a base coat coating containing a glitter pigment and a transparent clear top coat coating.After applying these coatings, for example, by so-called wet-on-wet, baking both coatings at once It is formed by curing. Further, a solid coating film containing no brilliant pigment may be used as the top coating film.

[0003]

When the above-mentioned coating film is formed, the concealing property is poor with a high chroma coating color, and the base cannot be sufficiently concealed, which often hinders the introduction of lines. For this reason, in order to improve the hiding power, carbon black has conventionally been added to the coating composition. But,
When carbon black is added, there is a problem that the saturation is reduced.

[0004] The present invention has been made in view of the above problems, and a coating composition capable of obtaining a coating film having high concealing property while maintaining chroma, and a coating composition using the same. An object of the present invention is to provide a method for forming a film and a coated object.

[0005]

The invention according to claim 1 of the present application provides a coating composition comprising the following (1) to (3). (1) Vehicle (2) Brilliant pigment and / or coloring pigment (3) Hiding agent comprising aluminum flake having an average particle diameter of 6 μm or less and a specific surface area of 52000 cm ² / g or more by a BET method.

The invention according to claim 2 of the present application is the invention according to claim 1, wherein the concealing agent has an average particle diameter of 3 to 6 μm and a particle size of B
The specific surface area by the ET method is 52000 to 60000 cm ²
/ G of aluminum flakes.

According to a third aspect of the present invention, in the first or second aspect, the content of the concealing agent is 0.01 to 10 parts by weight based on 100 parts by weight of the solid content of the paint. A coating composition is provided.

According to a fourth aspect of the present invention, there is provided a coating composition according to any one of the first to third aspects, wherein the glittering pigment is a mica pigment.

According to a fifth aspect of the present invention, a clear top coat film is formed after forming a base coat film by using the coating composition according to any one of the first to fourth aspects. And a method for forming a coating film characterized by the following.

According to a sixth aspect of the present invention, there is provided a coating film forming method comprising forming a top-coating solid coating film using the coating composition according to any one of the first to fourth aspects. provide.

According to a seventh aspect of the present invention, there is provided a coated article formed by a method according to the fifth or sixth aspect.

According to the present invention, the saturation is maintained by using fine aluminum flakes alone as a hiding agent or in combination with carbon black instead of carbon black which has been conventionally used as a hiding agent. This makes it possible to secure high concealment properties while expanding the range of color design and color gamut. That is, it contributes to expansion of the color gamut.

[0013]

Embodiments of the present invention will be described below. The coating composition of the present invention comprises the following (1) to
(3) is contained as an essential component.

(1) Vehicle The vehicle (1) used in the present invention contains a brilliant pigment / colored pigment (2), a concealing agent (3), etc. And a crosslinking agent.

Examples of the resin for forming a coating film constituting the vehicle include an acrylic resin, a polyester resin, an alkyd resin, a fluororesin, and the like. In particular, an acrylic resin and a polyester resin are preferably used. In addition, a thermoplastic resin such as a thermoplastic acrylic resin, a two-component urethane resin, or a silicone resin that can be cured by drying at room temperature can also be used. Hereinafter, the resin for forming a coating film and the crosslinking agent will be described.

<Resin for Forming Coating Film> (A) Acrylic resin The acrylic resin is a hydroxyl group such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, N-methylolacrylamide, etc. Containing (meth) acrylate monomer, (meth) acrylic acid, crotonic acid, itaconic acid,
Ethylenically unsaturated monomers having a carboxyl group such as fumaric acid and maleic acid, and methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl acrylate, and acrylic acid 2- It can be obtained by polymerizing at least one kind of an alkyl (meth) acrylate monomer such as ethylhexyl, n-octyl acrylate, n-dodecyl acrylate, etc. by a usual method. In addition, (meth) acrylic acid means acrylic acid or methacrylic acid. Further, copolymerizable (meth) acrylonitrile, styrene, (meth) acrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, n-butoxymethylacrylamide and the like may be blended. The number average molecular weight of the acrylic resin is preferably from 1,800 to 100,000, more preferably from 5,000 to 20,000.

(B) Polyester resin The polyester resin is obtained by polycondensing (esterifying) a polyhydric alcohol with a polybasic acid or its anhydride.

Examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, glycerin, trimethylolethane, and trimethylol. Methylolpropane, pentaerythritol, dipentaerythritol and the like can be mentioned, and these polyhydric alcohols can be used alone or in combination of two or more.

The polybasic acid or anhydride thereof includes phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride. Acids, maleic anhydride, fumaric acid, itaconic acid, trimellitic anhydride and the like can be mentioned, and these can be used alone or in combination of two or more.

The number average molecular weight of the polyester resin is 200
Preferably from 10,000 to 300,000 to 300,000.
0 is more preferred.

<Cross-Linking Agent> Examples of the cross-linking agent include amino resins such as melamine resins, and blocked polyisocyanate compounds. Further, a two-component polyurethane resin, a silicone resin, or the like that can be cured by drying at room temperature can also be used.

(A) Amino resin As the amino resin, for example, a condensate obtained by reacting one or a mixture of two or more amino compounds such as melamine, urea, and benzoguanamine with formaldehyde, and a condensate thereof, such as methanol, butanol, etc. And an alkyl etherified melamine resin reacted with a lower alcohol. The number average molecular weight of such an alkyl etherified melamine resin is preferably from 400 to 1,200.

In particular, an average of 0 to 0 per triazine ring
An amino resin having one imino group is preferred, and an amino resin having an average of 0 to 0.2 imino groups is preferred. The portion other than the imino group is bonded to an alkyl ether group or the like. The average number of imino groups per triazine ring was determined by the weight ratio of carbon, hydrogen and nitrogen determined by elemental analysis and NH / -NC determined by ¹ H-NMR.
It is calculated from the molar ratio of H ₂ OR.

(B) Block Polyisocyanate Compound Block polyisocyanate compounds include aliphatic polyfunctional isocyanates such as hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPD).
A) alicyclic polyfunctional isocyanates such as I), diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated M;
Examples thereof include those in which a functional group of a polyisocyanate compound such as DI is partially or completely blocked by a blocking agent.

<Blending ratio> The blending ratio of the coating film forming resin and the crosslinking agent is 90 to 90% in terms of solid content.
It is 50% by weight, preferably 85-60% by weight, and the crosslinking agent is 10-50% by weight, preferably 15-40% by weight. If the crosslinking agent is less than 10% by weight (the resin for forming a coating film exceeds 90% by weight), the crosslinking in the coating film is not sufficient.
On the other hand, if the cross-linking agent exceeds 50% by weight (the resin for forming a coating film is less than 50% by weight), the storage stability of the coating composition is reduced and the curing speed is increased.

(2) Bright pigment / color pigment <Glitter pigment (2-A)> As the glitter pigment (2-A) used in the present invention, those conventionally used for paints are conventionally used. For example, mica pigments such as titanium dioxide-coated mica, colored mica, metal-plated mica, leafing type aluminum pigment, non-leafing type aluminum pigment, metal titanium flake, stainless flake, plate-like iron oxide, phthalocyanine flake, graphite, metal-plated glass flake And the like, and mica pigments are particularly preferred.

<Coloring Pigment (2-B)> As the coloring pigment (2-B) used in the present invention, an organic or inorganic pigment conventionally used for paints is conventionally used.
For example, azo lake pigments, phthalocyanine pigments, indico pigments, berylen pigments, quinophthalone pigments,
Dioxazine pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments and the like, and as the inorganic pigments, for example, graphite, yellow iron oxide, red iron oxide,
Titanium dioxide and the like can be mentioned. The amount of the coloring pigment to be added can be arbitrarily set according to the hue as long as the coating film retains the glitter.

(3) Hiding Agent The hiding agent (3) used in the present invention has an average particle diameter of 6
μm or less, specific surface area by BET method is 52000 cm
² / g or more of aluminum flakes.

The average particle size of the aluminum flake used as the hiding agent (3) is 6 μm or less, preferably 3 μm or less.
６6 μm. When the average particle size exceeds 6 μm, the chroma is extremely reduced.

The specific surface area of the aluminum flake used as the hiding agent (3) by the BET method is 52000 cm ² /
g or more, preferably 52000 to 60000 cm
² / g. If the specific surface area is less than 52000 cm ² / g, sufficient hiding properties cannot be obtained. The specific surface area is defined as the total surface area (cm ² / g) per 1 g of the pigment, and each pigment manufacturer reports the specific surface area. B
The adsorption isotherm of nitrogen gas can be measured and calculated by the ET method.

Table 1 shows fine aluminum flakes (3-A) suitable for use in the present invention and comparative aluminum flakes (3-A) whose average particle diameter and specific surface area do not satisfy the conditions of the present invention.
The results of comparison of the concealability when B) was used in combination with carbon black (3-C), which has been conventionally used as a concealing agent, or when carbon black (3-C) was used alone. The concealing property is evaluated by a dry film thickness (μm) at which the black-and-white opaque paper cannot be visually judged after coating and baking with varying thickness of the black-and-white concealing paper. The smaller the value, the better the concealing property.

[0032]

[Table 1]

"Other additives" The coating composition of the present invention comprises, in addition to the above essential components, an extender pigment, an antisettling agent,
A curing catalyst, an ultraviolet absorber, an antioxidant, a surface conditioner such as silicone or an organic polymer, a sagging agent, a thickener, a crosslinkable polymer particle (microgel), or the like can be appropriately added. The performance of paints and coatings can be improved by blending these additives at a ratio of 5 parts by weight or less based on 100 parts by weight of the vehicle (based on solid content).

"Substrate to be Coated" The coating composition and the method for forming a coating film of the present invention can be applied to a substrate such as wood, metal, glass, cloth, plastic and foam. For example,
Metals such as iron, aluminum, copper or their alloys,
Inorganic materials such as glass, cement, concrete, etc., resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyamide, acrylic resin, vinylidene chloride resin, polycarbonate, polyurethane, epoxy resin, and various plastic materials such as FRP, Examples include natural materials such as wood and fiber materials.

[Coating Film Forming Method] Next, in the coating film forming method of the present invention, after forming a base coat coating film using the above-mentioned coating composition, a clear top coat coating film is formed to form a glittering coating film. It is a method of forming or a method of forming a top-coated solid coating film using the above-mentioned coating composition.

<Base Coat Coating> After forming an electrodeposition coating or an intermediate coating on an object to be coated, the above coating composition containing the glitter pigment and the color pigment of the component (2) is used. A base coat film is formed by applying a wet-on-wet method or a bake-on-wet method on a base coat such as an electrodeposited coat or an electrodeposition and intermediate coating. In the wet-on-wet method, after applying a paint for a base coat on an object to be coated, drying it by air drying or the like, and then applying a paint for a base coat coat while the base coat is in an uncured state or a semi-cured state. Is a method of baking and curing at once. The bake-on-wet method is a method in which a base coat is baked and cured, then a paint for a base coat is applied and baked again to cure. The coating method is not particularly limited, but a spray method, a roll coater method and the like are preferable. The thickness of the base coat film is not particularly limited, but the dry film thickness is preferably 5 to 50 μm, more preferably 10 to 30 μm.

<Clear Top Coat Coating> A clear coating is applied on the base coat coating to form at least one clear top coat coating. When there are many glittering pigments in the base coat film, applying two or more layers of clear paint improves the glitter on the surface. The clear coating may be any of those commonly used for topcoats. The base coat film and the clear top coat film can be formed by a wet-on-wet method. In the case where a clear coating is applied a plurality of times by a wet-on-wet method to form a base coat film, baking may be performed after the final clear coating is applied. The baking temperature after application of the clear paint is preferably from 120 to 160 ° C. The thickness of the clear top coat film is not particularly limited, but the dry film thickness is 10
-80 μm is preferable, and 20-50 μm is more preferable.

As the clear paint, acrylic resin,
A mixture of at least one thermosetting resin selected from a polyester resin, a fluororesin, a modified resin thereof, and the like and a cross-linking agent described above; and a vehicle comprising a carboxyl group-containing polymer and an epoxy group-containing polymer. Can be used.

<Top Coated Solid Coating> In the same manner as the base coat coated film, the top coated solid coating film is formed by forming an electrodeposition coating film or an intermediate coating film on an object to be coated and then applying the above-mentioned coating composition to (2) )), Paint only those containing colored pigments, and apply a top-coating solid coating by wet-on-wet method or bake-on-wet method on the base coat such as electrodeposition coating or electrodeposition and intermediate coating. Form.

[0040]

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 weight part unless there is particular notice.

"Preparation of substrate to be coated" Dull steel plate (length 300
mm, a width of 100 mm and a thickness of 0.8 mm) using a zinc phosphate treating agent (trade name "Surfdine SD2000", manufactured by Nippon Paint Co., Ltd.), and then a cationic electrodeposition paint (trade name "Power Top") U-50 "(manufactured by Nippon Paint Co., Ltd.) so as to have a dry film thickness of 25 μm. Then, after baking at 160 ° C. for 30 minutes, an intermediate coating (trade name “Olga S-90 Sealer Gray (N-
6) ", manufactured by Nippon Paint Co., Ltd.) was applied by air spraying so as to have a dry film thickness of 40 μm, and baked at 140 ° C. for 30 minutes to form an intermediate coating film.

"Formation of glitter coating film (Examples 1 to 14, Comparative Examples 1 to 3)"<Preparation of glitter coating composition> Acrylic resin (styrene /
A copolymer of methyl methacrylate / ethyl methacrylate / hydroxyethyl methacrylate / methacrylic acid,
Number average molecular weight about 20,000, hydroxyl value 45, acid value 1
5, solid content 50% by weight) and melamine resin (trade name “Uban 20SE”, manufactured by Mitsui Chemicals, solid content 60% by weight)
And (2-A) a brilliant pigment, (2-B) a color pigment,
(C) The concealing property imparting agents were blended in the types and ratios corresponding to Examples 1 to 14 and Comparative Examples 1 to 3 shown in Table 2, respectively. Next, the mixture was stirred and mixed with an organic solvent (weight ratio of toluene / xylene / ethyl acetate / butyl acetate = 70/15/10/5) by a dissolver so as to obtain an appropriate coating viscosity, thereby preparing a glittering coating composition.

The glitter pigment (2-A) was prepared in Example 1
-9 and 13 and Comparative Examples 1 and 2, mica pigment (trade name "Exterior Bright Silver" manufactured by Marl), and Examples 10-12, 14 and Comparative Example 3 with aluminum paste (trade name "Al Paste"). 91-05
62 ", manufactured by Toyo Aluminum Co., Ltd.).

Examples of the coloring pigment (2-B) include Examples 1 to
9 and 13 and Comparative Examples 1 and 2 are trade names “Fast Gen Green S” (manufactured by Dainippon Ink and Chemicals, Inc.).
For Examples 10 to 12, 14 and Comparative Example 3, the trade name "Syanin Blue MR-3" (manufactured by Toyo Ink Mfg. Co., Ltd.), and for Examples 15 to 17 and Comparative Example 4, the trade name "Taipe CR-97" (Ishihara Sangyo Co., Ltd.).

Examples 1 to 3 of the hiding agent (3)
For 5, 10, 11, 13 to 16, fine aluminum flakes having an average particle diameter and a specific surface area shown in Table 1 (3-
A) and carbon black (3-C) having a specific surface area shown in Table 1 (trade name “FW-200P”, manufactured by Degussa Corporation)
The fine aluminum flakes (3-A) were used alone in Examples 6 to 9, 12, and 17. Further, for Comparative Example 1, comparative aluminum flake (3-B) (trade name “Alpaste 92-0592”, manufactured by Toyo Aluminum Co., Ltd.) having the average particle diameter and specific surface area shown in Table 1 and the above carbon black (3-B) C) together with Comparative Examples 2 to
As for No. 4, the above carbon black (3-C) was used alone.

The amounts of the above components shown in Table 2 are as follows:
The solid content is 100 parts by weight of the solid content.

<Formation of Glittering Coating Film> On the surface to be coated of the base material, the above-mentioned glittering coating composition was applied to a dry film thickness of 15 μm to form a base coat coating film. The coating was performed using an electrostatic coating machine (trade name “Auto REA”, manufactured by Ransberg Gemma) at an atomization pressure of 2.8 kg / cm ² . The atmosphere in the booth during coating was maintained at a temperature of 25 ° C. and a humidity of 75%. After the coating, the coating was set for 3 minutes, and the clear coating was applied so that the dry film thickness became 35 μm to form a clear top coat coating film. Set at room temperature for 10 minutes,
Bake at 140 ° C. for 30 minutes.

The clear paint was an acrylic / melamine resin clear paint (trade name “Super Lac O-130 Clear”, manufactured by Nippon Paint Co., Ltd.) for Examples 1 to 12 and Comparative Examples 1 to 3. For No. 14, a clear paint (trade name "Macflow O-520 Clear", manufactured by Nippon Paint Co., Ltd.) composed of a blend of a carboxyl group-containing polymer and an epoxy group-containing polymer was used.

[Formation of Top Coated Solid Coating (Example 15)
-17, Comparative Example 4) <Preparation of solid coating composition> Polyester resin (number average molecular weight: about 3000, hydroxyl value: 80, acid value: 5, solid content: 6)
0% by weight) and melamine resin (trade name "Uban 20S")
E ", manufactured by Mitsui Chemicals, Inc., solid content 60% by weight) and 80: 2
The coloring pigment (2-B) and the concealing agent (3) were added to the vehicle obtained by blending at a solid content weight ratio of 0, and the corresponding types of Examples 15 to 17 and Comparative Example 4 shown in Table 2 were used. And in proportions. Subsequently, an organic solvent (weight ratio of toluene / xylene / ethyl acetate / butyl acetate = 70/15/1)
0/5) together with a dissolver to stir and mix to obtain a coating proper viscosity to prepare a solid coating composition.

As the coloring pigment (2-B), Example 15
17 to 17 and Comparative Example 4
R-97 "(manufactured by Ishihara Sangyo Co., Ltd.).

Examples of the concealing agent (3) are described in Example 1.
About 5 and 16, the said minute aluminum flake (3-A)
And carbon black (3-C) (trade name "FW-20
0P ", manufactured by Degussa Corporation), and in Example 17, the fine aluminum flakes (3-A) were used alone. In Comparative Example 4, the carbon black (3-
C) was used alone.

<Formation of Solid Coating Film>
The solid coating composition was applied so that the dry film thickness became 40 μm. The coating is performed by an electrostatic coating machine (trade name "Auto
REA ", manufactured by Ransberg Gemma Co.)
The test was performed at 8 kg / cm ² . The atmosphere in the booth during coating was maintained at a temperature of 25 ° C. and a humidity of 75%. After painting, 10 at room temperature
Minutes and baked at 140 ° C. for 30 minutes.

The hiding power and chroma of each coating film of Examples and Comparative Examples were evaluated by the following evaluation methods and evaluation criteria. Table 3 shows the results. In Table 3, solid parts by weight of the glitter pigment (2-A) in the paints of the examples and the comparative examples with respect to the solid content of the paint, and the glitter pigment (2-A) and the coloring pigment (2
Also shown are the solid content parts by weight based on the total paint solid content of -B) and the concealing agent (3), and the type of clear paint used.

<Evaluation Method and Evaluation Criteria> (Concealment) After coating and baking on black-and-white concealing paper with different film thickness, the dry film thickness (μ
m). (Saturation) Visual judgment was made based on the following criteria. ○… Saturated ○ − や… Slightly colored △… Normal △ − ×… Slightly cloudy ×… Slightly cloudy

[0055]

[Table 2]

FIG.

[0056]

[Table 3]

[0057]

As described above, according to the present invention, high opacity is maintained while maintaining chroma by using fine aluminum as a concealing agent in place of carbon black conventionally used. This contributes to color design and widening of the color gamut, that is, expansion of the color gamut.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (reference) C09D 5/38 C09D 5/38 201/00 201/00 F term (reference) 4D075 AE06 CB07 CB13 DB02 DC12 EA43 EC02 EC04 EC11 EC23 EC53 EC54 4J038 CG141 CG151 CG171 CJ031 CJ131 CJ141 DA142 DA162 DD071 DD081 DG302 HA066 HA436 KA08 KA12 KA20 PB07 PC02

Claims (7)

[Claims] 1. A coating composition comprising the following (1) to (3). (1) Vehicle (2) Brilliant pigment and / or coloring pigment (3) Hiding agent comprising aluminum flake having an average particle diameter of 6 μm or less and a specific surface area of 52000 cm ² / g or more by a BET method. 2. The opacity imparting agent has an average particle size of 3 to 6 μm.
m and the specific surface area by the BET method is 52000 to 60000
The coating composition according to claim 1, characterized in that the aluminum flakes cm 2 / ^g. 3. The method according to claim 1, wherein the content of the hiding agent is 1% of the solid content of the paint.
3. The coating composition according to claim 1, wherein the amount is 0.01 to 10 parts by weight based on 00 parts by weight. 4. The coating composition according to claim 1, wherein the glitter pigment is a mica pigment. 5. A method for forming a coating film, comprising: forming a base coating film using the coating composition according to claim 1; and then forming a clear top coating film. . 6. A method for forming a coating film, comprising forming a top-coating solid coating film using the coating composition according to any one of claims 1 to 4. 7. A coated article formed by a method according to claim 5 or 6.