JP2002256216A - Inter coating composition having high opacifying property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inter coating composition which can sufficiently covering surface defects of chipping primer including a dust part or an under coating film provide a coating film with high surface smoothness and can clearly reproduce color development of a top coating film. SOLUTION: This inter coating composition comprises (1) a thermosetting coating film-forming resin, (2) a curing agent and (3) a pigment obtained by combining (a) an organic and/or inorganic colored pigment with (b) an extender pigment and in the pigment (3), the amount of the organic and/or inorganic colored pigment (a) is at least 30 wt.% based on the total amount of the pigment (3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate coating composition used for coating an automobile body, and particularly to sufficiently cover a dust portion formed around a chipping primer, thereby obtaining a high composite coating film. The present invention relates to an intermediate coating composition capable of imparting surface smoothness.

[0002]

2. Description of the Related Art The surface of an automobile body is generally used for protecting a surface, improving designability and commercial value, for providing an undercoating film having anticorrosion performance, a rustproofing property, and for hiding defects on the surface of the undercoating film. Composite coatings have been formed that consist of an intermediate coating and a topcoat that provides a high aesthetic appearance. However, during running, such as a part of the car body, specifically the bonnet tip, around the tire house, the roof tip, pillars, etc. In places where rust may occur, a chipping primer is first formed on the undercoat, and then an intermediate coat is formed.

The chipping primer is locally formed with a dry film thickness of at least about 5 μm in the area where the pebbles collide, and the intermediate coating film is formed with a dry film thickness of about 40 μm on the entire vehicle body. You. As described above, the chipping primer is a very thin coating film as compared with the intermediate coating film, and can impart chipping resistance to the composite coating film. May cause defects.

[0004] Generally, the chipping primer is applied locally by a spray coating method or the like, but at the same time, the paint scatters around a portion where chipping resistance is required. When the scattered paint is dried and solidified, a so-called dust portion scattered discontinuously is formed. The dust provides an uneven coating surface. Therefore, when the intermediate coating is applied over the entire surface of the coating film including the dust portion and is baked and cured, a portion where the smoothness of the coating film surface is not achieved partially appears, and finally, the composite coating is applied. It may also reduce the appearance of the film.

In order to overcome the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. Hei 11-33478 discloses that a chipping-resistant primer and then an intermediate paint are applied on a bake-cured electrodeposition coating film on an object to be coated. A method of forming a chipping-resistant composite coating film, which comprises coating by a wet method and curing both at the same time, is disclosed. This means that in the dust area, the chipping primer is at least partially melted and integrated with the intermediate coating layer to eliminate the difference in color between the dust area and the rest of the coating film and enhance the surface smoothness. hand,
The purpose is to improve the appearance of the obtained composite coating film.

[0006] However, even if the coating film forming method described in the above-mentioned publication is applied, if an overcoating film having a high brightness (for example, pastel color) is formed, the unevenness of the underlying coating film cannot be completely hidden. In some cases, the surface smoothness of the composite coating film cannot be sufficiently obtained, and the appearance of the overcoat film may be hindered.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a base steel sheet, a base coat, and a base coat including a partially formed chipping primer even when a high-brightness top coat is applied. To provide an intermediate coating composition for forming an intermediate coating film capable of completely concealing defects of the above, ensuring sufficient surface smoothness of a subsequently formed top coating film and improving the appearance of the entire composite coating film. It is to be.

[0008]

Means for Solving the Problems Conventionally used intermediate coating materials include a thermosetting film-forming resin, a curing agent, a pigment,
And it contains a solvent and various additives. As the pigment, a combination of a coloring pigment and an extender is usually used. Here, the coloring pigment is excellent in dispersibility and exhibits black, white and other colors (green, blue, red, etc.), and is therefore used particularly for the purpose of toning an intermediate coating film.
On the other hand, extenders have low dispersibility, but usually exhibit an achromatic color, and are useful for imparting sharpness to a coating film. Most typically, titanium dioxide (white) as a color pigment
By combining carbon black (black) and barium sulfate as an extender, a gray or beige intermediate coating is prepared.

In order to solve the above-mentioned problems in the prior art, an intermediate coating film capable of exhibiting high surface smoothness and a base concealing property on a chipping primer containing a dust portion is required. Therefore, by paying attention to the mixing ratio between the extender pigment and the coloring pigment in the intermediate coating, the mixing amount of the coloring pigment in the total pigment content is made higher than before so that the intermediate coating film before curing has a higher flow property. Was found to be able to be imparted, and it was possible to coat the chipping primer containing the dust portion more smoothly due to the high flow property. Further, it has been found that by setting the blending ratio of the coloring pigment to at least 30% by weight of the total pigment content, the concealing property of the undercoat film is enhanced, and the appearance of the overcoat film formed thereafter is sufficiently reproduced.

Therefore, the present invention provides (1) a thermosetting film-forming resin, (2) a curing agent, and (3) (a) an organic and / or inorganic coloring pigment and (b) an extender pigment. An intermediate coating composition containing a pigment comprising a combination of, in the pigment (3), an organic and / or inorganic coloring pigment (a),
An intermediate coating composition comprising at least 30% by weight based on the total weight of the pigment (3).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The intermediate coating composition of the present invention comprises:
(1) a thermosetting film-forming resin, (2) a curing agent, and (3) (a)
It contains a pigment obtained by combining an organic and / or inorganic coloring pigment with the extender (b).

(1) Thermosetting film-forming resin

[0013] The thermosetting film-forming resin suitable for the intermediate coating is not particularly limited.
Acrylic resin, polyester resin, alkyd resin, epoxy resin, urethane resin and the like are used.

(2) Curing agent The curing agent (2) used in combination with the thermosetting film-forming resin (1) includes an amino resin and / or a blocked isocyanate resin.

Most preferred thermosetting film-forming resin (1)
The combination of and the curing agent (2) is a combination of an alkyd resin and / or a polyester resin and an amino resin from the viewpoint of pigment dispersibility or workability.

In the intermediate coating composition of the present invention, the thermosetting film-forming resin (1) is used in an amount of 5% based on the total resin solid content in the coating.
It is contained in an amount of 0 to 70% by weight, preferably 57 to 65% by weight, and the curing agent (2) is contained in an amount of 30 to 45%, preferably 35 to 43%, based on the content of the film-forming resin (1). Used in%.

(3) Pigment The pigment (3) includes a combination of (a) an organic and / or inorganic coloring pigment and (b) an extender pigment. Said
In (3-a), as an organic coloring pigment suitably used,
For example, azo chelate pigment, insoluble azo pigment, condensed azo pigment, benzimidazolone pigment, diketopyrrolopyrrole pigment, phthalocyanine pigment, indigo pigment, perinone pigment, perylene pigment, dioxane pigment, quinacridone Pigments, isoindolinone pigments, metal complex pigments, and the like; examples of inorganic color pigments include chrome yellow pigment, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide.

In the color pigment (3-a), depending on the color of the undercoat film to be concealed and the color of the overcoat film to be subsequently coated,
Inorganic color pigments and organic color pigments are appropriately used in combination, and it is particularly preferable to mix more inorganic color pigments than organic color pigments. As the inorganic color pigment, titanium oxide is most preferably used.

On the other hand, as the extender pigment (3-b), calcium carbonate, barium sulfate, clay, talc and the like are used.

In the present invention, the coloring pigment (3-a) and the extender (3-
b) is used in combination at a compounding ratio (% by weight) of 30:70 to 100: 0, more preferably 35:65 to 90:10. That is, at least 3 to the total weight of the pigment (3)
It is a feature of the present invention that 0% by weight is blended. By using the coloring pigment (a) in this range, the intermediate coating composition of the present invention, after coating, in the state of a coated film before curing, a higher flowability than before can be obtained, whereby the underlying coating film Concealment is improved.

In the intermediate coating composition of the present invention, all the pigments (3)
Has a pigment weight content (PWC) of 3
The range is from 0 to 45%, particularly preferably from 35 to 43%.

Here, the PWC (%) is represented by the following equation.

PWC = [Pigment (3) (g) / {Pigment (3) (g) + Total resin solids (g)}] × 100 The total resin solids in the formula is in the range of 50 to 70%. , Preferably 52 to 67%, more preferably 55 to 65%.

The intermediate coating composition of the present invention may further comprise, in addition to the above basic compositions (1) to (3), additives such as a viscosity control agent, an antisettling agent, a curing accelerator, a plasticizer, and an ultraviolet absorber. ,
You may mix | blend a pigment dispersing agent, a surface conditioner, etc. In the intermediate coating composition of the present invention, the additive is resin 100 in the coating.
Parts to 0.01 to 1.0 part, preferably 0.05 to 1.0 part
It is contained in 0.6 parts.

Solvents for dissolving or dispersing the above components include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, octane and mineral spirit; ethyl acetate, butyl acetate and the like. Esters: Organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone are used alone or in combination.

The intermediate coating composition of the present invention has a viscosity at room temperature (20 ° C.) of no.
4 to 19 to 30 seconds, preferably 20 to
It is adjusted to a range of 25 seconds, or after the preparation and before use, is diluted with a suitable diluent so that the viscosity at the time of coating falls within the above range.

The objects to which the intermediate coating composition of the present invention is applied include automobile bodies such as passenger cars, trucks, motorcycles and buses, and various parts used for assembling the same. Materials (eg, iron, copper, aluminum, tin, zinc, etc. and alloys containing these metals),
Plastics, foams and castings. The present invention is particularly useful when applied to a metal substrate requiring chipping resistance and the like. It is preferable that the object to be coated is subjected to a chemical conversion treatment with phosphoric acid, chromic acid or the like before applying the present invention.

Here, FIG. 1 is a cross-sectional view of a composite coating film (10) partially having chipping resistance, including an intermediate coating film (4) made of the intermediate coating composition of the present invention. . As shown in FIG. 1, the present invention is applied to, for example, the entire surface of an electrodeposition coating film (2) formed as an undercoat film on the above-mentioned coating object (1). In particular, in the part to be coated with the pebbles, the tipping primer paint is locally applied to a desired area on the electrodeposition coating film so that the dry film thickness is about 3 to about 20 μm (3). ), The intermediate coating composition of the present invention is applied thereon by a wet-on-wet method (4), and the two are simultaneously baked and cured to improve the chipping resistance of the resulting composite coating film (10). Can be done.

The intermediate coating composition of the present invention may be applied by a commonly used method such as spray coating, spray coating or roll coating. Intermediate paint, after painting, 100
It may be cured at a temperature in the range of -180C, preferably in the range of 120-160C to obtain a coating with a higher degree of crosslinking. If the curing temperature of the intermediate coating material exceeds 180 ° C, the resulting coating film becomes hard and brittle, and if it is less than 100 ° C, curing becomes insufficient. The curing time of the intermediate coating composition may vary depending on the curing temperature. For example, at a temperature of 120 to 160 ° C, 10 to 30 minutes is preferable.

The intermediate coating film 4 has a dry film thickness of 15 to 50 μm.
m, preferably 20 to 40 μm.
If the dry film thickness of the intermediate coating film exceeds 50 μm, the sharpness may deteriorate, or problems such as unevenness or flow may occur at the time of coating. Conversely, if it is less than 15 μm, the primary purpose of the present invention is to provide a base film. Concealment cannot be achieved.

In general, the intermediate coating film thus formed
(4) A base paint and a clear paint are sequentially applied on the entire upper surface, for example, as a top coat (5 and 6), and simultaneously baked to form a desired composite coating film (10) as shown in FIG. Is done.

[0031]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Preparation Example 1: Preparation of Dark Gray Intermediate Coating Composition A pigment and a solvent were added to a polyester resin having the composition shown in Table 1 below, and preliminarily mixed.
A glass bead medium was added in a G mill and dispersed at 30 ° C. or lower for 1 hour to obtain a pigment paste having a particle size of 10 μm or lower. By adding a melamine resin and an additive to this pigment paste so as to have the composition shown in Table 1, and mixing with a disper,
A dark gray intermediate coating composition of the present invention was prepared.

Preparation Examples 2 to 5: Preparation of various intermediate coating compositions
(1) Intermediate coating compositions were prepared in the same manner as in Preparation Example 1 except that the compositions and amounts shown in Table 1 below were used (Preparation Example 2: beige, 3: blue green). Color, 4: green, 5: semi-black).

[0033]

[Table 1] ¹⁾ : Nippon Paint Co., Ltd. (polyester resin varnish), hydroxyl value 93 mgKOH / g (solid content), acid value 7
mgKOH / g (solid content), number average molecular weight 3000, resin solid content 70% by weight) ²⁾ : manufactured by Mitsui Cytec, trade name Cymel 202
(Compound name: methyl / butyl mixed etherified melamine resin, resin solid content: 80% by weight) ³⁾ : trade name, carbon black MA-, manufactured by Mitsubishi Chemical Corporation
100, (Carbon Black) ⁴⁾ : Product name: Titanium R61N (titanium dioxide) manufactured by Sakai Chemical Co., Ltd. ⁵⁾ : Product name: Talox synthetic iron oxide LL-XLD (inorganic yellow iron oxide) ⁶⁾ : Dainippon Ingen Kagaku Kogyo Co., Ltd., product name First Gen Blue 5408 (organic coloring pigment blue) ⁷⁾ : BASF Co., Ltd., product name Heliogen Green L8
690 (organic coloring pigment green) ⁸⁾ : manufactured by Sakai Chemical Industry Co., Ltd., trade name Variace B34 (barium sulfate) ⁹⁾ : manufactured by Mitsui Petrochemical Co., Ltd., trade name Regimix RL-
4 (acrylic additive)

Preparation Examples 6 to 10: Various intermediate coating compositions
Preparation (2) Each of the intermediate coating compositions prepared in Preparation Examples 1 to 4 was mixed at a mixing ratio (weight ratio) shown in Table 2 to prepare various intermediate coating compositions. PW of color pigment in each paint
C is as follows; Preparation Example 6: Colored pigment (24
%), 7: coloring pigment (32%), 8: coloring pigment (39
%), 9: coloring pigment (30%), 10: coloring pigment (21
%).

[0035]

[Table 2] ^* : Unit = second / Ford Cup No. 4.20 ° C

Examples 1 to 10 Laminated coating films containing the intermediate coating compositions obtained in Preparation Examples 1 to 10 were prepared by the following procedure. Dull steel plate treated with zinc phosphate (thickness 0.8mm x 30cm x 10c)
m) A cationic electrodeposition paint (trade name “Power Top V20” manufactured by Nippon Paint Co., Ltd.) was electrodeposited on the surface so as to have a dry film thickness of 20 μm.
By baking for minutes, an electrodeposition coating film was formed. A chipping primer paint (trade name “Olga TO CP101” manufactured by Nippon Paint Co., Ltd.)
Kai) was applied using an air spray so as to form a dust with a dry film thickness, and allowed to stand at room temperature for 10 minutes. Then, each of the intermediate coating compositions obtained in Preparation Examples 1 to 10 was dried. Each was spray-coated so as to have a film thickness of 15, 20 or 25 μm, set at room temperature for 10 minutes, and baked at 140 ° C. for 30 minutes. Next, the base paint (Nippon Paint Co., Ltd., trade name "Olga
TO H300 Champagne Silver ")
After coating at 5 μm and setting at room temperature for 10 minutes, a clear paint (trade name “Olga TO 563 Clear” manufactured by Nippon Paint Co., Ltd.) was further applied at a dry film thickness of 35 μm. After setting for 10 minutes, the base coat and clear coat are cured at 140 ° C for 30 minutes,
1, a composite coating 10 consisting of an electrodeposition coating 2, a chipping primer 3, an intermediate coating 4, a base coating 5, and a clear coating 6.
Was formed (see FIG. 1).

Each steel sheet sample including the laminated coating film 10 was visually evaluated for the finished appearance in accordance with the following evaluation criteria. Evaluation criteria: ：: Finished skin is smooth and glossy and very good. ：: Finished skin and gloss are at no problem level. Matte results are summarized in Table 3.

[0038]

[Table 3]

According to the results shown in Table 3, the intermediate coating composition of the present invention (Examples 1, 2, 7, 8 and 9) containing at least 30% by weight of the coloring pigment in all the pigments was dried on the chipping primer. It can be seen that by coating with a film thickness of at least 15 μm, the base concealment property is improved and a good finished appearance is obtained.

[0040]

According to the intermediate coating composition of the present invention, the coloring pigment is blended in a larger proportion than in the prior art in the blending ratio of the extender pigment contained as the pigment and the coloring pigment, so that after the coating, Higher flowability can be given to the previous coating,
Due to this high flow property, the background concealing property is improved. In particular, the present invention can effectively cover the surface defects of the chipping primer including the dust portion even when the chipping primer is partially formed on the base coating film. Further, the present invention provides a high level of concealing property even when a high-brightness (light-colored) top coat is applied thereon by setting the mixing ratio of the color pigment to at least 30% by weight of the total pigment content. The color development of the coating film can be sufficiently reproduced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a composite coating film partially having chipping resistance, including an intermediate coating film formed from the intermediate coating composition of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steel plate, 2 ... Cathodic electrodeposition coating, 3 ... Chipping primer, 4 ... Intercoat coating consisting of the intermediate coating composition of the present invention, 5 ... Base coating, 6 ... Clear coating, 7 ... Top coating Film, 10 ... composite coating

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 CG001 DA112 DB001 DD001 DD121 DD231 DG001 HA216 JB18 KA03 KA08 KA20 NA01 PB07 PC02

Claims (3)

[Claims] 1. A composition comprising (1) a thermosetting film-forming resin, (2) a curing agent, and (3) a combination of (a) an organic and / or inorganic coloring pigment and (b) an extender pigment. An intermediate coating composition containing a pigment, wherein in the pigment (3), at least 30% by weight of an organic and / or inorganic coloring pigment (a) is blended with respect to the total weight of the pigment (3). An intermediate coating composition, comprising: 2. The intermediate coating composition according to claim 1, wherein the amount of the inorganic coloring pigment in the pigment (3) is larger than that of the organic coloring pigment. 3. The intermediate coating composition according to claim 1, wherein titanium dioxide is contained as an inorganic color pigment.