JPH0532932A - Topcoat paint and coating film forming method - Google Patents

Abstract

(57) [Summary] [Structure] An acrylic melamine-based curable coating material containing a pigment, wherein the pigment is dispersed in a vinyl resin having a hydroxyl group, a basic group and an acid group. [Effect] The obtained top coat film has excellent effects on appearance and performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top coating composition and a coating film forming method.

[0002]

2. Description of the Related Art Conventionally, acrylic melamine-based curable paints have been blended with pigments such as coloring pigments and extender pigments according to the application, and when the pigments are blended, the pigments are generally dispersed in advance with a pigment-dispersing resin. A pigment paste is used. The pigment-dispersed resin is difficult to disperse the pigment at the time of production, aggregates / precipitates the pigment during storage, reduces gloss of the coating film resulting therefrom, color separation, floating, and coating performance (weather resistance, acid resistance, etc.). It is added to prevent defects such as deterioration. As such a dispersion resin, usually, nonionic, anionic,
Cationic surfactants and aliphatic carboxylic acids are known. However, with these dispersed resins,
For example, if a nonionic or anionic one is used, the finish (gloss etc.) of the coating film will not be sufficient, and if a cationic one is used, the curability of the coating film will decrease and the curability and coating performance will decrease. There was a drawback that it was inferior to.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors in order to solve the above problems, the conventional acrylic melamine-based curable coating composition has a pigment containing a hydroxyl group, a basic group and an acid group. It was found that the use of a pigment paste dispersed with the vinyl resin has a coating film having excellent coating film performance and coating finish, and has completed the present invention. That is, the present invention relates to an acrylic melamine-based curable coating material containing a pigment, wherein the pigment is dispersed in a vinyl resin having a hydroxyl group, a basic group and an acid group, and a colored base coat and a clear base coating material and a material. Top coat is formed sequentially and 2 coats 1
In a coating film forming method for finishing by a baking method, the coating film forming method is characterized in that the coating material forming the colored base coat is the above-mentioned top coating material.

First, the coating material of the present invention will be described. In the coating composition of the present invention, the acrylic melamine-based curable coating composition in which a pigment is blended is an organic solvent-based, non-aqueous dispersion-type coating composition in which a conventionally known acrylic resin is used as a base resin and a melamine resin is used as a crosslinking agent. it can. The acrylic resin is an acrylic resin containing a hydroxyl group as an essential functional group component, and if necessary, a carboxyl group in the resin,
It may contain an amino group.

The vinyl resin used for dispersing the pigment contains a hydroxyl group, a basic group and an acid group as essential components. If even one kind of these groups is lacking, the finish of the coating film and the coating film performance are deteriorated, so that the inclusion of these groups is an important essential element in the present invention. Examples of the vinyl-based resin include copolymers obtained by radical polymerization of hydroxyl group-containing vinyl monomers, nitrogen-containing vinyl monomers, acid group-containing vinyl monomers and, if necessary, other vinyl monomers. Can be used.

Examples of the hydroxyl group-containing vinyl monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, (poly) alkylene glycol mono (meth) acrylate and the like. Adducts with lactones (eg, ε-caprolactone, etc.) and the like are included.

As the nitrogen-containing vinyl monomer, for example,
N, N-dimethylaminoethyl (meth) acrylate,
N-tert-butylaminoethyl (meth) acrylate, vinylpyrrolidone, N-butoxymethyl (meth) acrylate and the like are included. Examples of the acid group-containing vinyl monomer include (meth) acrylic acid, (anhydrous) maleic acid, and 2-carboxyethyl (meth) acrylate.

Other vinyl monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic. Butyl acid (n
-, I-, t-), hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Stearyl acid, cyclohexyl (meth) acrylate, styrene and the like are included.

The blending ratio of the above-mentioned vinyl monomer is such that the total amount of the vinyl monomer is about 0.1 to about 0.1.
60 parts by weight, preferably about 5-30 parts by weight, about 0.1-20 parts by weight of nitrogen-containing vinyl monomer, preferably about 0.5-
10 parts by weight, about 0.1 to 20 parts by weight of acid group-containing vinyl monomer, preferably about 0.5 to 10 parts by weight and about 0 to 99.7 parts by weight of other vinyl monomer, preferably about 40. ~ 9
4 parts by weight is good.

The radical polymerization of the above monomers is carried out by a conventionally known method, for example, in the presence of a radical polymerization initiator (eg, azobisvaleronitrile, perbutyl oxide, etc.), an inert organic solvent (eg, alcohol type, ester type). ,
(Ketone-based, ether-based, etc.) at a reaction temperature of about 80 to 220 ° C. The obtained copolymer has an average molecular weight of about 1,000 to 100,000, preferably about 3,0.
It can have a range of 00-80,000.

The pigment used in the paint of the present invention may be a coloring or transparent pigment of inorganic and organic pigments which are generally used in the field of paints and inks. Examples of the inorganic pigment include (1) oxides. System (zinc white, titanium dioxide, silica white, red iron oxide, chromium oxide, cobalt blue, iron black, etc.); (2) hydroxide system (alumina white,
(Yellow iron oxide, etc.); (3) Sulfides, selenides (zinc sulfide, vermilion, cadmium yellow, cadmium red, etc .;
(4) Phthalocyanide compounds (dark blue, etc.); (5) Chromate compounds (yellow lead, zinc chromate, molybdenum red, etc.); (6) Sulfate compounds (precipitable barium sulfate, etc.);
(7) Carbonate type (precipitating calcium carbonate etc.); (8) Silicate type (hydrous silicate, clay, ultramarine etc.); (9) Phosphate type (manganese violet etc.); (10) Carbon type (Carbon black, etc.) and the like. Examples of the organic pigment include (1) nitroso pigment type (naphthol green B
Etc.); (2) Nitro pigment system (Naphthol Yellow S etc.);
(3) Azo pigment type (resole red, lake red C,
Fast Yellow, Naphthol Red, Red etc.);
(4) Dyeed lake pigment system (alkali blue lake, rhodamine lake, etc.); (5) Phthalocyanine pigment system (phthalocyanine blue, fast sky blue, etc.); (6)
Condensed polycyclic pigment systems (perylene red, quinacridone red, dioxazine violet, isoindolinone yellow, etc.) are included.

In the coating composition of the present invention, a pigment and a dispersing resin are mixed and dispersed in advance to obtain a pigment organic dispersion (pigment paste), which is then mixed with an organic solution of an acrylic melamine type curable resin. The mixing ratio of the dispersing resin and the pigment varies depending on the kind of the pigment, but the dispersing resin (solid content) is usually about 0.1 to 1.0 with respect to 100 parts by weight of the pigment.
00 parts by weight, preferably about 0.5 to 500 parts by weight is desirable. The mixing and dispersion can be carried out by a conventionally known method, for example, a means such as pebble mill dispersion, sand mill dispersion, roll mill dispersion, shaker dispersion or the like. In addition to the above, the coating composition of the present invention may contain a curing catalyst, an ultraviolet absorber, polymer fine particles, metal powder, mica powder, a fluidity modifier, a diluent and the like, if necessary.

Next, the coating film forming method of the present invention will be described. In the method of the present invention, a colored base coat paint is applied to a material to form a colored base coat coating film, and then a clear paint is applied to the surface of the colored base coat coating film to form a clear top coat coating film, followed by heating. This can be done by simultaneously curing both coating films.

The base coat paint for forming the colored base coat used in the method of the present invention is an acrylic melamine type curable paint containing a color pigment and a metal powder (and / or mica powder), and the color pigment is a hydroxyl group. , A vinyl resin having a basic group and an acid group. As the coloring pigment, the metal powder, the mica powder, the acrylic melamine-based curable coating material in which the pigment is mixed, and the vinyl-based resin, the same ones as described above can be used.

As a material for applying the above base coat paint, preferably a chemical conversion treated steel plate is applied with an electrodeposition coating, and an intermediate paint (which may be omitted) is applied to various paints and various plastic materials. It is preferable to use a coating film, etc., which is coated with a suitable primer and coated with an intermediate coating (which may be omitted) as a material. As a method for forming a base coat coating film on a material, a base coat coating material is applied by a usual coating means, for example, electrostatic coating or non-electrostatic coating machine so that a dry film thickness is about 10 to 50 μm, Then leave it at room temperature for a few minutes or about 50-8
It can be carried out by preheating at 0 ° C. for several minutes.

As a method for forming a clear coating film on the base coat film, the above-mentioned clear paint is applied in the same manner as described above, for example, by using an electrostatic coating or a non-electrostatic coating machine so that the dry film thickness becomes about 15 to 50 μm. It can be carried out by coating the composition on the surface of the sheet, leaving it at room temperature if necessary, and then heating at about 100 to 180 ° C., preferably about 120 to 160 ° C. for about 20 to 60 minutes, preferably about 20 to 40 minutes.

The clear coating material may be appropriately selected from conventional ones without particular limitation, and is preferably an acrylic melamine-based curable clear coating material. The clear paint may contain no color pigment or may be mixed with a color pigment to such an extent that the base coat film is not hidden. Further, the clear paint may contain, for example, a transparent pigment, an ultraviolet absorber, polymer fine particles, and other additives for various paints. As the type of paint, it is desirable to use an organic solvent type or a non-aqueous dispersion type.

[0018]

As described above, in the conventional acrylic melamine-based curable paint, if an acidic or basic pigment dispersion resin is used, the curing of acrylic melamine will be accelerated or the curing will be inhibited. However, there is a drawback that the finished appearance or coating performance may be deteriorated due to the adverse effect such as that, and the dispersion resin itself, the dispersibility with respect to acidic and basic pigments, and the dispersion stability are not sufficient, so that the appearance and performance are excellent. It was difficult to form a coating film, but since the dispersion resin used in the present invention has an acid group, a basic group and a hydroxyl group, it itself has excellent dispersibility for various pigments and stability and is a substrate. It is presumed that a coating film excellent in finishability and performance could be formed because the acrylic melamine which is a resin has little influence on the curing.

[0019]

The present invention will be described in detail below with reference to examples. Material Dal steel sheet (chemical conversion treatment) is coated with an epoxy resin-based cationic electrodeposition coating (25 μm) and cured by heating at 170 ° C. for 30 minutes, and then as an intermediate coating, Rugabak AM (trademark, manufactured by Kansai Paint Co., Ltd., polyester) Resin / melamine resin-based automotive paint) was applied so that the dry film thickness was 30 μm, and baked at 140 ° C. for 30 minutes. Next, the coated surface was water-polished with # 400 sandpaper, drained and dried, and the coated surface was wiped with petroleum benzine, which was used as a material.

Paint 1 Acrylic resin A (styrene / methyl methacrylate /
Ethyl acrylate / n-butyl acrylate / 2-hydroxyethyl acrylate / dimethylaminoethyl methacrylate / acrylic acid = 5/44/20/10/1
7/2/2 "weight ratio" Average molecular weight of about 20,000) 140 parts by weight of 50% by weight xylene solution was mixed with 31.5 parts by weight of Perind Maroon R6434 (trade name, Bayer product, perylene pigment). After dispersion with a sand mill disperser, 30 parts by weight (solid content) of U-Van 28-60 (trade name, product of Mitsui Toatsu Chemicals, Inc., melamine resin) was added to this product to obtain coating 1.

Paint 2 In Paint 1, 31.% of Perind Maroon R6434.
Instead of 5 parts by weight, Paloma Blue B-4806 (trade name,
Bayer product, copper phthalocyanine pigment) 24.5
A coating material 2 was prepared in the same manner as the coating material 1 except that the weight part was used.

Paint 3 In Paint 1, instead of acrylic resin A, acrylic resin B (styrene / methyl methacrylate / ethyl acrylate / n-butyl acrylate / 2-hydroxyethyl acrylate / dimethylaminoethyl methacrylate = 5/46/20 Paint 3 was obtained in the same manner as Paint 1, except that the weight average molecular weight was about 20,000.

Paint 4 In Paint 3 Perrind Maroon R6434 31.5
A coating material 4 was obtained in the same manner as the coating material 3 except that 24.5 parts by weight of Paloma Blue B-4806 was used instead of the weight portion.

Paint 5 In Paint 1, instead of acrylic resin A, acrylic resin C (styrene / methyl methacrylate / ethyl acrylate / n-butyl acrylate / 2-hydroxyethyl acrylate / acrylic acid = 5/46/20/10
/ 17/2 "weight ratio" average molecular weight of about 20,000) was used to prepare Paint 5 by the same procedure as Paint 1.

Paint 6 In paint 5 31.5 of Perind Maroon R6434
A coating material 6 was obtained in the same manner as the coating material 5 except that 24.5 parts by weight of Paloma Blue B-4806 was used instead of the weight portion.

Paint 7 In Paint 1, in place of acrylic resin A, acrylic resin D (styrene / methyl methacrylate / ethyl acrylate / n-butyl acrylate / 2-hydroxyethyl acrylate = 5/46/20/10/17 " Paint 1 except that a weight ratio "average molecular weight of about 20,000" was used
A paint 7 was obtained by carrying out the same production as described above.

Paint 8 In Paint 7, 31.% of Perind Maroon R6434.
24.5 parts of Paloma Blue B-4806 instead of 5 parts by weight
A coating material 8 was obtained in the same manner as the coating material 5 except that the weight part was used.

Examples 1 and 2 Paints 1 and 2 were diluted to a spray viscosity and spray-coated on the above material so that the dry film thickness was about 40 μm.
A coating film was prepared by baking at 40 ° C. for 30 minutes. Comparative Examples 1 to 6 Coatings 3 to 8 were formed in the same manner as in Example 1 to form coating films.

Example 3 Aluminum paste and aluminum paste 7680NS for paint 1
(Trade name, manufactured by Toyo Aluminum Co., Ltd.) 7 parts by weight of a base coat paint mixed and dispersed is diluted to a spray viscosity and spray-coated on the above material so that the dry film thickness is about 40 μm, and then Magicron TC-71 (trade name, Kansai Paint Co., Ltd., acrylic / melamine resin-based clear paint for automobiles) was applied and baked at 140 ° C. for 30 minutes to 2
A coating film was prepared by the coat 1 bake method.

The coating film test results of the examples and comparative examples are summarized in Table 1.

[Table 1]

Coating film test method Coating surface smoothness: Smoothness of coating film surface (Yuzu layer, dust layer, etc.)
Was visually observed. The evaluation was performed based on the following criteria. ◯ is good, ◯ ⁻ is slightly inferior, Δ is inferior, and x is significantly inferior. Coating gloss: 60 ° specular reflectance was measured. Workability: Tested using the JIS5400 Erichsen test. The numerical value shows the limit extrusion mm number of cracks and peeling of the coating film.

Claims (2)

[Claims] 1. An acrylic melamine-based curable coating material containing a pigment, wherein the pigment is dispersed in a vinyl resin having a hydroxyl group, a basic group and an acid group. 2. In the method for forming a coating film in which a colored base coat and a clear top coat are sequentially formed on a material and finished by a two-coat one-bake system, the paint forming the colored base coat is the top coat paint according to claim 1. A characteristic method of forming a coating film.