JPH1112538A - Formation of metallic coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a metallic coating film good in interlayer adhesion, reduced in a glaring metallic appearance, having a moist metallic finished appearance and excellent in weather resistance. SOLUTION: This method for forming a metallic coating film comprises coating a base coating comprising (d) a polyvalent isocyanate compound and a metallic base resin comprising (a) a hydroxyl group-containing fluorocopolymer comprising tetrafluoroethylene and vinylic monomers containing at least a vinyl group-containing ester not containing a hydroxyl group and a hydroxyl group-containing vinylic monomer, (b) a hydroxyl group-containing acrylic resin polymer and (c) scaly metal powder, and subsequently coating a clear coating comprising the components (a), (b) and (d) on the base coating film. The clear coating film comprising the components (a), (b) and (d) preferably has a haze of 5-80%.

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 coating film having a metallic appearance with a moist feeling and having excellent corrosion resistance and weather resistance.

[0002]

2. Description of the Related Art Paints containing flaky metal powder have been widely used for heavy corrosion-resistant land structures such as tanks, plants, and steel towers, and for automotive topcoats since they have excellent corrosion resistance and appearance. These paints are generally paints based on resins having excellent weather resistance and corrosion resistance, such as silicone resin, acrylic resin, and urethane resin. In general, when coating an object to be coated, a flaky metal powder-containing coating is applied, and a clear coating is applied thereon. However, these conventional flake-like metal powder-containing coatings have long-term exposure, so that ultraviolet rays pass through the clear top coating and reach the undercoat, causing delamination between the undercoat and the topcoat. It could be awake or cracked. For this reason, attempts have been made to prevent the defects by blending additives such as an ultraviolet absorber, a light stabilizer and an antioxidant, but this is not sufficient. In addition, the use of a fluorine-based resin paint with good weather resistance as a clear top coat will cause problems such as delamination in a short period of time.
It is also described in JP-17113.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for forming a coating having good weather resistance and a moist metallic finish, which has good interlayer adhesion and suppresses a glaring metallic feeling. .

[0004]

SUMMARY OF THE INVENTION The present invention relates to (a) a vinyl group-containing ester containing no hydroxyl group and a vinyl monomer containing at least a hydroxyl group-containing vinyl monomer, and a hydroxyl group-containing vinyl monomer containing tetrafluoroethylene. A fluorine copolymer, (b) a hydroxyl group-containing acrylic resin polymer and (c)
After applying a base coat paint containing a metallic base resin consisting of scaly metal powder and a polyvalent isocyanate compound (d), a clear paint consisting of the above (a), (b) and (d) is overcoated and applied. The present invention relates to a method for forming a coating film. In addition, the present invention provides (a) a hydroxyl group-containing fluorinated copolymer comprising a vinyl monomer containing at least a hydroxyl group-free ester and a hydroxyl group-containing vinyl monomer and tetrafluoroethylene, (b) The present invention relates to the above-mentioned method for forming a coating film, wherein the clear coating film comprising a hydroxyl group-containing acrylic resin polymer and (d) a polyvalent isocyanate compound has a haze value (haze value) of 5 to 80%.

[0005] The feature of the present invention is that both (a) and (b)
Is to use a base resin containing The clear coating film obtained by mixing the polyvalent isocyanate (d) with the base resin intentionally lowers its transparency, and has a haze value of 5 to 80.
%, Preferably adjusted to 5 to 60%, so that a metallic finish with a moist feeling can be obtained when a flaky metal powder is blended with this and used as a metallic paint.
In addition, a coating film having weather resistance over a long period of time can be obtained. In addition, since the same type of base resin is used for the base coat and the clear coat, the stability of interlayer adhesion is improved, and the interlayer deterioration of the coating film is prevented for a long time.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The undercoating film used in the present invention is a base resin component capable of uniformly dispersing the flaky metal powder to be compounded. The base resin is formed by a crosslinking reaction with a curing agent at room temperature. It contains a hydroxyl-containing fluorine-containing copolymer and a hydroxyl-containing acrylic resin copolymer so that a cured coating film can be obtained.

As the copolymerizable fluorine-containing monomer constituting the hydroxyl-containing fluorine-containing copolymer, tetrafluoroethylene is used. As the fluorine-containing monomer, in addition to tetrafluoroethylene, there are chlorotrifluoroethylene, perhaloolefin, and the like. It is limited to tetrafluoroethylene.

The vinyl monomer which forms a hydroxyl group-containing fluorine-containing copolymer (a) by copolymerization with tetrafluoroethylene contains at least a vinyl group-containing ester having no hydroxyl group and a vinyl monomer having a hydroxyl group. . The vinyl monomer may further contain another vinyl monomer containing no hydroxyl group. It has been discovered that the hydroxyl group-containing fluorinated copolymer (a) having such a configuration increases the haze value (haze value) of the resulting coating film by mixing with the hydroxyl group-containing acrylic resin copolymer described below. . In particular, JP-A-4-
The hydroxyl group-containing fluorinated copolymer described in 279612 or a mixture thereof is mixed with the hydroxyl group-containing acrylic resin copolymer described below to give a moist metallic finish and excellent corrosion protection. To give a coated film.

The copolymer (a) preferred in the present invention
Are 20 to 60% by weight of tetrafluoroethylene, 5 to 40% by weight of a vinyl group-containing ester containing no hydroxyl group, and 1 to 45% of another vinyl monomer containing a hydroxyl group.
5% by weight of other vinyl monomer containing no hydroxyl group
４５45% by weight. Particularly preferably, 35 to 55% by weight of tetrafluoroethylene, 10 to 25% by weight of a vinyl-containing ester containing no hydroxyl group, and 5 to 20% of another vinyl monomer containing a hydroxyl group.
5% by weight of other vinyl monomer containing no hydroxyl group
-30% by weight. When the amount of tetrafluoroethylene is less than 20% by weight, the weather resistance is poor, and
If the amount is more than 10% by weight, the dissolving power in a solvent is poor. When the amount of the vinyl group-containing ester containing no hydroxyl group is less than 5% by weight, the compatibility with the hydroxyl group-containing acrylic resin copolymer is improved, the haze value (haze value) of the coating film is reduced, and 40% by weight is reduced. If it exceeds, there are problems such as poor weather resistance. If the amount of the hydroxyl group-containing vinyl monomer is less than 1% by weight, the curability is inferior. If the amount exceeds 45% by weight, gelation tends to occur and storage stability is inferior. If the content of the other vinyl monomer containing no hydroxyl group is less than 5% by weight, the weather resistance is inferior.
If the content is more than 10% by weight, the synthesis of the copolymer becomes difficult and gelation is liable to occur.

The vinyl group-containing ester containing no hydroxyl group, which constitutes the base resin (a), has the formula CHR ¹¹ ＣＨCHR ¹²
(.R ¹² wherein, R ¹¹ is represents a hydrogen atom or COOR ¹³
Represents COOR ¹³ or OCOR ¹³ . R ¹³ may be substituted with an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 8 carbon atoms. Represents a phenyl group. When R ¹² is OCOR ¹³ , R ¹¹ is a hydrogen atom). More specifically, the formula CH ₂ = CH
(OCOR ¹³ ) a carboxylic acid vinyl ester represented by the formula:
Maleic diester or fumaric diester represented by the formula (R ¹³ OOC) CHＣCH (COOR ¹³ ) is exemplified.

The above-mentioned vinyl carboxylate is not particularly restricted but includes, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl persatic acid, vinyl laurate, stearic acid. Vinyl and vinyl salicylate can be exemplified. The maleic acid diester or fumaric acid diester is not particularly limited, and examples thereof include dimethyl maleate, diethyl maleate, dibutyl maleate, dihexafluoropropylene maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, and fumarate. And ditrityl acid.

As the vinyl monomer containing a hydroxyl group,
Formula CH ₂ ＣＨCHR wherein R is OR ³¹ or CH ₂ OR ³¹
(R ³¹ represents a hydroxyalkyl group having 1 to 8 carbon atoms)
Represents hydroxyalkyl vinyl ether or hydroxyalkyl allyl ether, for example, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxy-2-
Methyl propyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxybutyl allyl ether, glycerol monoallyl ether and the like can be mentioned.

The vinyl monomer having no hydroxyl group is represented by the formula CH ₂ ＣＲCR ²¹ (CH ₃ ) (wherein R ²¹ represents an alkyl group having 1 to 8 carbon atoms). Such is not particularly limited, for example, isobutylene,
2-methyl-1-butene, 2-methyl-1-pentene,
2-methyl-1-hexene and the like can be mentioned.

The hydroxyl group-containing acrylic resin polymer used in the present invention is preferably a (meth) acrylate copolymer having a curable functional group in a side chain and / or a main chain. The curable functional group is a hydroxyl group, but may contain an amino group, a carboxy group, or an epoxy group together with the hydroxyl group. Examples of the acrylic polymer include "Hitaloid 3004", "Hitaroid 3018" (manufactured by Hitachi Chemical Co., Ltd.), "Acrydec A810-45", "Acrydec A814" (manufactured by Dainippon Ink and Chemicals, Inc.), and "Dianal LR-62".
0, "Dianal SS-1084" and "Dianal SS-792" (manufactured by Mitsubishi Rayon Co., Ltd.). However, if necessary, a homopolymer or copolymer of an alkyl ester of (meth) acrylic acid having 1 to 10 carbon atoms, for example, "Hitaloid 1" which is a commercially available product
005 "," Hitaroid 1206 "," Hitaloid 40 "
01 "(manufactured by Hitachi Chemical Co., Ltd.)," Dianal LR10
69, "Dianal LR-90" (manufactured by Mitsubishi Rayon Co., Ltd.), "Paraloid B-44", "Paraloid A-2"
1 "(manufactured by Rohm & Haas Chemical Industries) and the like.

The mixture of (a) a hydroxyl group-containing fluorine-containing copolymer and (b) a hydroxyl group-containing acrylic resin polymer constituting a base resin has a haze value (haze value) of 5 to 80 in a coating film in which both are mixed. %, From the viewpoint that a metallic finish with a moist feeling can be obtained, dispersibility with the pigment, weather resistance of the coating film, etc., the mixing ratio (weight ratio) of both is 95: 5 to 50:
50, particularly preferably 90:10 to 70:30. If the content of the fluorinated copolymer is more than 95% by weight, dispersibility with a pigment such as metal powder and a metallic finish as a coating film deteriorate. Conversely, if the amount is too small, the weather resistance and corrosion resistance tend to decrease.

In the present invention, the base resin is cured,
In order to exhibit mechanically and optically excellent coating film performance, a polyvalent isocyanate compound is used as a curing agent component of the base resin. Examples of the polyvalent isocyanate compound include 2,4 tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, trimers of these, adducts and burettes thereof, and polymers of these. Those having two or more isocyanate groups, and further blocked isocyanates are exemplified.

These polyvalent isocyanate compounds are mixed at a predetermined ratio with a hydroxyl group-containing component comprising the hydroxyl group-containing fluorine-containing copolymer and the hydroxyl group-containing acrylic resin copolymer at room temperature or, if necessary, by forced heating. It becomes a two-pack type paint that can be cured. Further, when the blocked isocyanates are used, a one-pack paint that can be baked and cured by mixing with the polyol component at a predetermined ratio is obtained.

As the scaly metal powder used in the above-mentioned scaly metal powder-containing paint, scaly aluminum powder and scaly stainless steel powder are particularly suitable, and the particle size of these metal powders is generally the average particle size. Is 10 to 60μ, preferably 20
Those having a size of 30 μm are suitable, and these metal powders can be mixed and used. The content of these flaky metal powders is from 40 to 40% of the flaky metal powder with respect to the paint spreader (the total of the hydroxyl group-containing fluorinated copolymer, the hydroxyl group-containing acrylic resin polymer and the curing agent) constituting the paint. 3% by weight, preferably 30-5% by weight, is suitable.

The scaly metal powder-containing paint used in the present invention may further contain, if necessary, organic or inorganic pigments such as ordinary phthalocyanine blue, carbon black and titanium oxide, dispersants, thickeners, Various additives such as a regulator and an ultraviolet absorber can be added.
Further, water or a solvent can be blended in the paint at an arbitrary ratio as a dispersion medium. As the organic solvent, those commonly used in paints, such as aromatic hydrocarbons, esters, and ketones, can be appropriately selected and used.

The clear paint used in the present invention may be a resin comprising the above-mentioned (a) a hydroxyl group-containing fluorinated copolymer, (b) a hydroxyl group-containing acrylic resin polymer and (d) a polyvalent isocyanate, or if necessary. The composition further contains various additives such as an ultraviolet absorber and a light stabilizer. The resin component of the clear paint is preferably as close as possible to the base coat paint, and most preferably the same resin component is used.

The paint thus obtained is mortar,
It can be applied to inorganic materials such as concrete, various metal materials such as steel plate, stainless steel plate and aluminum plate. As a coating method, an air spray, an airless spray, an electrostatic spray, etc., which are usually used for coating a paint, are sufficient, and a coating film is formed by factory coating or on-site coating.

[0022]

The present invention will be described in more detail with reference to the following examples. Note that all numerical values such as “parts” in the examples are based on weight. Preparation of Hydroxyl-Containing Fluorinated Copolymer (a) (A) Fluorinated Copolymer-Varnish of the Present Invention 48% Tetrafluoroethylene, Vinyl Vivalate 14
%, Isobutylene 7%, cyclohexyl vinyl ether 20%, and 4-hydroxybutyl vinyl ether 11% according to the method described in JP-A-4-279612. ) Was prepared. (B) Fluorine-containing copolymer-Comparative A monomer mixture consisting of 47% of tetrafluoroethylene, 30% of cyclohexyl vinyl ether, 8% of ethyl vinyl ether and 15% of hydroxybutyl vinyl ether is polymerized in the same manner to obtain a fluorine-containing copolymer. Coalescence (solid content hydroxyl value 4
4) A 50-butyl acetate solution was prepared. (C) Fluorine-containing copolymer-for comparison chlorotrifluoroethylene 48%, vinyl bivalate 13%, isobutyl 5%, cyclohexyl vinyl ether 23%, 4-hydroxybutyl vinyl ether 12%
Was polymerized in the same manner to prepare a 50% butyl acetate solution of a fluorine-containing copolymer (solid content hydroxyl value: 57).

Haze value of clear coating film The clear coating materials (A-1) to (I) are prepared by using the above fluorinated copolymers (a-1), (a-2) and (a-3).
1) was prepared. Table 1 shows the formulation of the clear paint and the haze value (haze value) of this coating film.

[0024]

[Table 1]

The haze was measured as follows. A clear paint is applied on a polypropylene sheet with a dry film thickness of 20.
and dried at room temperature for 72 hours.
The coating film is peeled from the polypropylene sheet, and the coating film is read directly by a haze computer measuring device (Suga Test Instruments Co., Ltd.)
Was used to measure the haze value (haze value).

Preparation of paint for base coat The above-mentioned clear paint is further blended with flaky metal powder and additives as shown in Table 2, and the paint for base coat (A
-2) to (I-2) were prepared.

[Table 2]

Preparation of clear paint Clear paints (A-3) to (I-3) used as topcoat paints
-3) was prepared according to the formulation shown in Table 3.

[0028]

[Table 3]

Examples 1 to 5 and Comparative Examples 1 to 4 A two-pack impregnated primer (manufactured by Daido Paint) was applied to a slate plate so as to have a dry film thickness of 30 μm. An intermediate mold coating (manufactured by Daido Paint) was applied to a dry film thickness of 30 μm, and dried at room temperature for 16 hours to prepare a coating substrate. Metallic coating was performed on this substrate using a combination of a base coat paint (a paint containing flaky metal powder) shown in Table 4 and a clear paint. The coating was performed by coating a flaky metal powder-containing coating material to a dry film thickness of 30 μm, and after drying for 16 hours, a clear coating material was similarly applied to a dry film thickness of 20 μm to obtain various test plates. It was left at room temperature for 7 days from the final coating to the start of the test. In addition, all three paintings were made by air spray.

As can be seen from the test results in Table 4, the coating films prepared by the method of the present invention (Examples 1 to 5) had good moist metallic appearance even after the accelerated weathering test, and had good gloss retention. It had excellent coating performance without degradation of secondary adhesion. However, in Comparative Examples 2 and 3, the gloss retention after the accelerated weathering test was good, but the interlayer adhesion was poor. In Comparative Examples 1 and 4, the interlayer adhesion after the accelerated weathering test was good. In Comparative Example 1, discoloration occurred and the metallic feeling was poor, and in Comparative Example 4, there was no discoloration, but the metallic feeling was poor.

[0031]

[Table 4]

The evaluation methods and evaluation items of the evaluation items in Table 4 are as follows. Metallic appearance: Evaluated by the naked eye (moist metallic appearance) ：: Very good ○: Good △: Somewhat poor ×: Poor gloss: 60-degree specular reflectance The gloss after 1500 hours and 3000 hours of weather ometer treatment is as follows: The gloss was expressed as the retention. Primary adhesion: 100 squares are made by cutting the coating film at intervals of 1 cm in length and width with a cutter, and after pressing cellophane tape on the coating film, it is pulled up vigorously, and the ratio of the number of squares not peeled off It was expressed by. Secondary adhesion: The coating test piece was immersed in warm water at 40 ° C. for 14 days, taken out, and 16 hours later, the above-mentioned adhesion test was performed.

[0033]

According to the present invention, the scaly metal powder-containing paint of the present invention and the clear paint of the present invention containing no metal powder are applied in combination to have a moist metallic tone, and have a clear undercoat film. A metallic coating film having excellent adhesion stability of the coating film and excellent long-term weather resistance can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 127/00 C09D 127/00 133/14 133/14 // C08G 18/62 C08G 18/62

Claims (2)

[Claims] 1. A hydroxyl group-containing fluorinated copolymer comprising a vinyl monomer containing at least a hydroxyl group-free ester and a hydroxyl group-containing vinyl monomer and tetrafluoroethylene, and (b) After applying a base coat paint containing a metallic base resin consisting of a hydroxyl group-containing acrylic resin polymer and (c) flaky metal powder and (d) a polyvalent isocyanate compound, the above (a), (b) and (d) ), A method for forming a metallic coating film in which a clear paint comprising: 2. (a) a hydroxyl group-containing fluorine-containing copolymer comprising a vinyl monomer containing at least a hydroxyl group-free ester and a hydroxyl group-containing vinyl monomer and tetrafluoroethylene, (b) The haze value (haze value) of a clear coating film comprising a hydroxyl group-containing acrylic resin polymer and (d) a polyvalent isocyanate compound is 5 to 80.
%.