JPH06102178B2 - Manufacturing method of precoated steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoated steel sheet having a low gloss and a soft velvety touch, and a method for producing a precoated steel sheet having a low gloss and a soft and metallic feeling by adding a metal or the like. .

[0002]

2. Description of the Related Art Conventionally, a coated steel sheet having a matte appearance and a velvety appearance has been obtained by coating a coating composition containing 40 to 60 μm colored particles and a binder on the steel sheet. In this method, flow coating and spray coating are used as a coating method, and a 2-coat 2-bake method is usually adopted. That is, after coating a rust preventive primer containing a rust preventive pigment as a base coat and baking it to form a base coat of 3 to 10 μm, a top coat containing 150 to 200 parts by weight of colored particles with respect to 100 parts by weight of a binder. Is coated and baked to form a top coat film of 30 to 50 μm. On the other hand, in the above method,
When an anticorrosive primer containing a large amount of coloring pigment is used, the surface smoothness of the undercoating film is lowered and the adhesion to the topcoating film is lowered. In addition, workability, corrosion resistance, and the like also decrease with the decrease in adhesion to the top coating film. Therefore, in order to secure the adhesiveness with the top coating film, it is necessary to minimize the content of the color pigment in the primer and to develop the makeup color of the steel sheet by the colored particles in the top coating material.

However, the colored particles in the top coating are
Since the particle size is large and the coloring power is small, the hiding power of the top coating film is small. Therefore, in order to increase the hiding power,
(1) A method of setting the film thickness of the overcoat coating film to, for example, 30 μm or more, and (2) a method of mixing an ordinary color pigment into the overcoat coating material. However, in the above method (1), since a thick film is formed, not only the coated steel plate becomes extremely expensive, but also the coating film foams during baking and pinholes easily occur. Further, in order to suppress the foaming phenomenon, skill in the coating technique is required and productivity is reduced. On the other hand, in the method (2), for example, the hiding power can be increased with a top coating film of about 20 μm. However,
In this method, since the color pigment adheres to and agglomerates around the colored particles in the coating film, the function of the colored particles, that is, the function of expressing a soft velvety with low gloss is significantly impaired.

[0004]

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide a coating film having a small thickness, yet having a low gloss, a soft velvety touch and metallic feel , and an appearance, a hiding property, An object of the present invention is to provide a method for producing a precoated steel sheet which is excellent in workability and corrosion resistance.

[0005]

According to the present invention, there is provided a paint 10 containing a rust preventive pigment and a coloring pigment on at least one surface of a steel sheet.
The same undercoat paint as 100 parts by weight of the binder was prepared by applying an undercoat paint containing 1 to 20 parts by weight of a vinyl copolymer to 0 part by weight and baking it to form an undercoat paint film of 3 to 10 μm. Colored particles having an average particle diameter of 1 to 80 μm of systematic color are used in an amount of 150 to 200 parts by weight and a meta particle having a diameter of 5 to 250 μm.
Provided is a method for producing a precoated steel sheet, which comprises applying an overcoat paint containing 0.1 to 10 parts by weight of a lick-like substance and baking it to form an overcoat film of 12 to 25 μm.

In the present specification, "same system color" means
It means that the colors to be compared are almost the same color visually.

The "colored particles" have an average particle size of 1-80.
As long as it is μm and is colored, colored polymer particles, particles coated with a coloring pigment with a resin, and the like are also included.

[0008]

The steel sheet used in the present invention is not particularly limited, and examples thereof include galvanized steel sheet, stainless steel sheet, zinc-aluminum plated steel sheet, cold rolled steel sheet and the like.

The rust preventive pigment contained in the undercoat paint is
Examples thereof include zinc chromate, strontium chromate, lead chromate, aluminum dihydrogen tripolyphosphate, barium metaborate, barium borate, zinc borate, and calcium molybdate. At least one of these rust preventive pigments is contained.

The color pigment may be either an inorganic or organic pigment, such as titanium oxide, chrome yellow,
Inorganic pigments such as cadmium yellow, nickel titanium yellow, red iron oxide, cadmium red, molybdenum orange, milori blue, ultramarine blue and carbon black; azo pigments, triphenylmethane pigments, quinacridone pigments, slene pigments, pyrene pigments, Examples of organic pigments include phthalocyanine pigments and isoindolinone pigments. Further, the color pigments include extender pigments such as talc, barium sulfate and calcium carbonate. At least one kind of these color pigments is used, and two or more kinds of color pigments having different hues may be used for toning.

A binder is contained in the undercoat paint containing the rust preventive pigment and the color pigment. This binder is
It suffices if it can be baked, for example, polyester resin,
Examples thereof include acrylic resin, fluororesin, silicone polyester resin, alkyd resin, and epoxy resin. These binders can be used alone or in combination of two or more. The undercoat paint is a curing agent corresponding to the above binder,
For example, it may contain amino resins such as methylated melamine and butylated melamine, blocked isocyanates, and the like. Further, in order to accelerate the bake hardening, for example, an acid catalyst may be contained.

Then, with respect to 100 parts by weight of the undercoat paint,
1 to 20 parts by weight of vinyl copolymer, preferably 1 to 10
It is contained in parts by weight. When the amount of the vinyl copolymer is less than 1 part by weight, not only the surface smoothness is impaired, but also
The adhesion with the steel sheet is impaired. Therefore, it is difficult to continuously and efficiently manufacture the precoated steel sheet particularly in the two-coat, two-bake method in which the material is baked at a high temperature and a high speed using a roll coater. If it exceeds 20 parts by weight, the weather resistance may decrease. The undercoating paint containing the vinyl copolymer in the above range is remarkably excellent in adhesion to a steel plate and is also excellent in dispersibility in rust preventive pigments and color pigments. Therefore, a large amount of a rust preventive pigment and a coloring pigment can be contained to increase the hiding power, and a base coat film having excellent surface smoothness can be formed, and the adhesion with the top coat film is also excellent. As the vinyl copolymer, a copolymer containing a vinyl-based monomer unit such as vinyl chloride or vinyl acetate, particularly a copolymer containing a vinyl chloride unit is preferable. Examples of such a vinyl copolymer include, for example, Vinylite VMC manufactured by Union Carbide Co., Ltd.
H, Nippon Zeon Co., Ltd. under the trade name of Zeon (Geon) 4
00 × 110A, Goodrich Chemical Co., Ltd., trade name Zeon (Geon) 400 × 110, and the like.

The content of the rust preventive pigment may be in the range where the rust preventive property can be secured.

The undercoat paint usually contains an organic solvent such as water, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, esters, ketones and ethers.

The above undercoat paint is applied to the steel sheet and baked to form an undercoat film of 3 to 10 μm, preferably 4 to 7.5 μm. When the film thickness of the undercoating film is less than 3 μm, the hiding property is usually insufficient, and when it exceeds 10 μm, the film thickness of the entire coating film including the overcoating film becomes large.

The topcoat paint contains colored particles of the same system color as the color pigment of the basecoat paint. The average particle diameter of the colored particles is 1 to 80 μm, preferably 20 to 50 μm.
When the average particle diameter of the colored particles is out of the above range, it is difficult to form a top coating film having a low gloss and a soft velvety touch.

Examples of the colored particles include colored polymer particles or particles obtained by coating an inorganic or organic pigment with a polymer such as polyester, polyamide, acrylic resin and other modified polymers. In particular, spherical particles made of colored elastic polymer and spherical particles obtained by coating an inorganic or organic pigment with an elastic polymer are preferable. The elastic polymer preferably has an elongation of 10 to 1000%. When the elongation is less than 10%, the soft feeling of the coating film is small, and when it exceeds 1000%, the coating film is likely to be scratched. The elastic spherical particles improve the velvety feel.

Further, the polymer of the colored particles is preferably a polymer which does not change its color by baking, particularly an acrylic resin. More specifically, when a white paint and a black paint using colored particles coated with polyurethane or acrylic resin are baked under high temperature and high speed conditions, the discoloration degree of each coating film is measured by the Hunter's Lab (ΔE) method. Then, the results shown in Table 1 are obtained. The baking conditions are as follows: baking time 2 minutes, baking temperature 200 ° C, 260 ° C
And the case of a baking temperature of 180 ° C. was used as a reference.

[0019]

[Table 1]

From Table 1, when the polymer of the colored particles is an acrylic resin, the discoloration is small, and it is particularly useful for high speed baking at high temperature for coating.

The colored particles preferably have an oil absorption of 40 to 130% and a hiding power of 30 to 200 g / m ² . Oil absorption is 4
Colored particles of less than 0% are generally difficult to produce, and colored particles having an oil absorption of more than 130% have poor dispersibility. Further, when the hiding power is less than 30 g / m ² , the hiding power of the top coating film is small, and when it exceeds 200 g / m ² , the touch feeling is deteriorated.

Such colored particles can be obtained by using a Uethicon (Ue
Tikon) as the respective colors of the product name Deco Silk, from Sekisui Kasei Co., Ltd. under the product name Tekmer MB10X-20-B
6. Available from Dainichiseika Kogyo Co., Ltd. under the trade name Love Koror, and from Toyobo Co., Ltd. under the trade name Toughtic. Among these colored particles, each color of the trade name Labcoroll with an acrylic resin as a coating polymer is preferable because the degree of discoloration is extremely small even at high temperature baking.

At least one kind of colored particles is used, and two or more kinds of colored particles having different hues may be used for toning.

The content of the colored particles is 150 to 200 parts by weight with respect to 100 parts by weight of the binder of the top coating composition. When the content of the colored particles is less than 150 parts by weight, the soft feel and the velvety feel are reduced, and 2
If the amount exceeds 00 parts by weight, the cost of the top coating composition becomes extremely high.

Furthermore, by adding metallic powder or mica powder, which is a metallic substance, to the top coat, it is possible to add metallic feeling and toning. The particle size of the metallic substance is about 5 to 250 μm, preferably about 10 to 50 μm. Further, the amount of the metallic substance added is 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder of the top coating,
It is preferably about 0.5 to 1.5 parts by weight. When the addition amount of the metallic substance is less than 0.1 part by weight,
When no metallic appearance is exhibited and the amount exceeds 10 parts by weight, the velvety tone disappears.

As the binder contained in the top coating,
The binder of the undercoat paint can be used. The binder of the topcoat paint is preferably a binder of the same type as that of the binder of the undercoat paint because it enhances the adhesion to the undercoat paint film. For example, if the binder of the base coat is polyester,
The binder of the topcoat is preferably polyester.

Further, the topcoat paint usually contains a curing agent, water, an organic solvent and the like, like the undercoat paint.

By applying the above-mentioned top coating composition to a base coating film and baking it to form a top coating film of 12 to 25 μm, preferably 15 to 22 μm, a low gloss, a soft feeling and a velvety touch feeling are excellent. A precoated steel sheet is obtained.
Also, by adding a metallic substance to the top coating,
Pre-coated steel sheet with low gloss, soft feel, and velvety texture and excellent metallic appearance can be obtained.

In addition, in applying the undercoat paint and the topcoat paint,
Conventional coating means, such as spray coating, can be adopted, but it is preferable to perform roll coating continuously and efficiently at high speed. The undercoat paint and the topcoat paint may be applied to at least one surface of the steel sheet.

The baking conditions can be appropriately selected. In the case of spray coating, the baking can be usually carried out at a temperature of 150 ° C. for 20 minutes, and in the case of roll coating, high-temperature and high-speed conditions than spray coating. , For example, a temperature of 200 to 2
It can be performed under baking conditions of 60 ° C. and 50 to 120 seconds.

In the method of the present invention, after forming an undercoating film excellent in surface smoothness, hiding power and adhesion to a steel plate,
In low gloss, soft feeling, metallic appearance with a touch feeling of the bi load adjustment, because it forms an excellent top coat in adhesion to the undercoat paint film, two-coat two-bake method in which baking using a roll coater, in particular It is particularly useful for continuously and efficiently producing precoated steel sheets by baking at high temperature and high speed.

[0032]

EXAMPLES The present invention will be described in more detail based on the following examples.

Preparation of Undercoat Paint Base (1) Acrylic resin (Mitsui Toatsu Chemicals, Inc., trade name 7
48-5M, solid content 55% by weight) 100 parts by weight, amino resin (manufactured by Mitsui Toatsu Chemicals, Inc., trade name 10S-60, solid content 60% by weight) 20 parts by weight, strontium chromate 5 parts by weight, and 4 parts by weight of carbon black are mixed and dispersed by an attritor for 5 hours to prepare a base for undercoat paint (1)
Was prepared.

(2) Polyester (Mitsui Toatsu Chemicals, Inc.)
Manufactured by P-646, solid content 60% by weight, 100 parts by weight, amino resin (manufactured by Mitsui Toatsu Chemicals, Inc., trade name 10S)
-60) 20 parts by weight, K-White (Teikoku Kako Co., Ltd.)
10 parts by weight) and 20 parts by weight of titanium oxide were mixed and dispersed by an attritor for 5 hours to prepare a base (2) for undercoat paint.

(3) High molecular weight polyester (manufactured by Mitsui Toatsu Chemicals, Inc., trade name HMP-25, solid content 50% by weight) 1
00 parts by weight, melamine resin (manufactured by Mitsui Toatsu Chemicals, Inc., trade name Cymel 303, solid content 98 to 100% by weight) 15
Parts by weight, 0.15 parts by weight of p-toluenesulfonic acid, 10 parts by weight of zinc chromate, and 4 parts by weight of phthalocyanine blue were mixed and dispersed by an attritor for 5 hours to prepare a base (3) for undercoat paint.

Preparation of Top Coat (a) Acrylic resin (Mitsui Toatsu Chemical Co., Ltd., trade name 7
48-5M,) 20 parts by weight of amino resin (manufactured by Mitsui Toatsu Chemicals, Inc., trade name: 10S-60), colored particles (manufactured by Toyobo Co., Ltd., trade name: Tough C)
B-107) 108 parts by weight and aluminum powder 0.5 parts by weight were added and mixed with a paint conditioner for 1 hour to prepare a top coating composition (a). The content of the colored particles is the same as that of the acrylic resin and amino resin binder 10.
It is 161 parts by weight with respect to 0 parts by weight. The content of the aluminum powder is 0.
7 parts by weight.

( B ) 100 parts by weight of high-molecular polyester (manufactured by Mitsui Toatsu Chemicals, Inc., trade name: HMP-25) and 15 parts of melamine resin (manufactured by Mitsui Toatsu Chemicals, trade name: Cymel 303) Parts by weight, p-toluenesulfonic acid 0.
15 parts by weight, 130 parts by weight of colored particles (manufactured by Dainichiseika Kogyo KK, trade name Lovecorol 060 Blue) and 1.0 part by weight of mica powder were added and mixed with a paint conditioner for 1 hour, and the topcoat paint ( b ) Was prepared. The content of the colored particles is 200 parts by weight based on 100 parts by weight of the binder of polyester and melamine resin. The content of the mica powder is 1.5 parts by weight with respect to 100 parts by weight of the binder.

(C) Polyester (Mitsui Toatsu Chemicals, Inc.)
Made, trade name P-646) 100 parts by weight of amino
Resin (Mitsui Toatsu Chemical Co., Ltd., trade name 10S-60) 2
0 parts by weight, colored particles (Uetikon)
Company, product name Deco Silk White NY) 130 parts by weight
Add and mix with paint conditioner for 1 hour,
A topcoat paint (c) was prepared. The content of colored particles
Is a 100-ply binder of polyester and amino resin
181 parts by weight with respect to parts by weight.

[0039]

Example 1 1 part by weight of a vinyl copolymer (trade name: Vinylite VMCH manufactured by Union Carbide Co., Ltd.) was added to 100 parts by weight of the base material for undercoat paint (1), and the mixture was stirred with a tesol bar for 30 minutes. I got a base coat.

The obtained undercoat paint was applied to a stainless steel plate using a roll coater and baked at a high temperature and a high speed, that is, at a temperature of 220 to 250 ° C. for 50 to 90 seconds to form an undercoat film having a thickness of 10 μm. .

Then, the above-mentioned topcoat paint (a) was applied to the undercoat paint using a roll coater, and baked under the same conditions as the above-mentioned undercoat paint to form a topcoat paint film having a thickness of 18 μm.

[0042]

[Example 2] 100 parts by weight of the base (3) for the undercoat paint was mixed with a vinyl copolymer (manufactured by Nippon Zeon Co., Ltd., trade name Zeo ).
Down the (Geon) 400 × 110A) was added 10 parts by weight, and stirred for 30 minutes by Tezoruba. The obtained undercoat paint was applied to a galvanized steel sheet using a roll coater and baked under the same high temperature and high speed as in Example 1 to obtain a film thickness of 4 μm.
m undercoat coating film was formed.

Then, the above-mentioned top coating composition ( b ) was applied to the bottom coating film by using a roll coater, and baked under the same conditions as the above-mentioned bottom coating film to form a top coating film having a thickness of 22 μm.

[0044]

Comparative Examples 1 and 2 30 parts by weight of a vinyl copolymer (manufactured by Nippon Zeon Co., Ltd., trade name: ZEON 400 × 110A) per 100 parts by weight of the base material (3) for undercoat paint (Comparative Example 1), 0.5 part by weight (Comparative Example 2) was added, and the mixture was stirred with a Tesor bar for 30 minutes. The obtained undercoat paint was applied to a galvanized steel sheet using a roll coater and baked under the same high temperature and high speed as in Example 1 to form an undercoat film with a film thickness of 4 μm.

Then, the above-mentioned topcoat paint ( b ) was applied to the undercoat paint using a roll coater and baked under the same conditions as the above-mentioned bottom paint to form a topcoat paint film having a thickness of 22 μm.

[0046]

[Comparative Example 3] A primer containing a rust preventive pigment (Nippon Yushi Co., Ltd., trade name Precolor Primer LP-2) was used.
It was applied to a galvanized steel sheet using a roll coater and baked under the same high temperature and high speed as in Example 1 to form an undercoat film having a film thickness of 5 μm.

High molecular polyester (Mitsui Toatsu Chemicals, Inc.)
Manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name 10S-60) to 100 parts by weight of manufactured product, trade name HMP-25).
20 parts by weight, 3 parts by weight of carbon black, colored particles (manufactured by Toyobo Co., Ltd., trade name Toughtic CB-107) 10
Add 8 parts by weight, and add 5 parts by paint conditioner.
The mixture was dispersed for a period of time to obtain a top coating composition.

Next, this overcoat paint was applied to the undercoat paint using a roll coater, and baked under the same conditions as the above-mentioned undercoat paint to form an overcoat paint film having a thickness of 20 μm.

[0049]

Comparative Example 4 A wash primer was applied to a galvanized steel sheet by spraying and baked at 80 ° C. for 20 minutes to form an undercoat coating film having a film thickness of 5 μm. Then, before Symbol topcoat paint (c) spray by applying the primer coating film by baking at 0.99 ° C. 20 minutes to form a topcoat coating film having a thickness of 40 [mu] m.

The design properties of the precoated steel sheets obtained in each of the examples and comparative examples, that is, the soft feel, the velvety feel to the touch, the appearance, and the low glossiness were evaluated based on the criteria of excellent and unfavorable. The metallic feeling of the precoated steel sheets obtained in Examples 1 and 2 was evaluated according to the same criteria as above.

The anticorrosion property is based on JIS K-5400, and the surface condition after 500 hours is visually inspected.
Evaluation was carried out using the same criteria as above.

The workability conforms to JIS G3312,
Evaluation was carried out using the same criteria as above.

The weather resistance was evaluated according to JIS K-5400, and the surface condition after 1000 hours was visually evaluated by the same criteria as above.

Regarding the hiding property, those in which the color of the primer could not be visually observed were excellent, and those in which the color was visible were unacceptable.

The heat resistance was evaluated as good when there was almost no discoloration of the coating film baked at 200 ° C. for 2 minutes and at 260 ° C. for 2 minutes, and good when there was some.

The results are shown in Table 2.

[0057]

[Table 2]

From Table 2, Comparative Examples 1 and 2 in which the content of the vinyl-based copolymer is out of the range of the present invention are inferior in workability or corrosion resistance. Further, in Comparative Example 3 in which the top coat contains colored particles and color pigments, the design of the coating film was poor, and in Comparative Example 4 in which the top coating film was thick, not only the cost of the precoated steel sheet was high, but also the coating film had a pin. A hole has occurred. On the other hand, the precoated steel sheets obtained in Examples 1 and 2 were excellent in designability, inexpensive, and simultaneously satisfying various characteristics.

The precoated steel sheets of Examples 1 and 2 were
It had a good metallic feel.

[0060]

EFFECTS OF THE INVENTION (1) According to the present invention, the film thickness of the coating film is small, and the touch feeling is soft and velvety with a low gloss, and at the same time, the appearance, concealability, processability and corrosion resistance are excellent. An excellent pre-coated steel sheet can be manufactured at low cost with high productivity. (2) A velvety precoated steel sheet having a metallic feel is obtained. (3) Since a metallic substance such as metal powder is added to the topcoat paint, a precoated steel sheet having a concealing property, a thin film thickness, and excellent workability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Okamoto 4271-12 Fujisawa, Fujisawa City, Kanagawa Prefecture (56) References Japanese Patent Publication No. 1-23188 (JP, B2) Toyohiko Yoshida et al. "Encyclopedia of Painting" ( A55-4-30) Asakura Shoten Co., Ltd. 303 to P. 330 (especially P. 307)

Claims (1)

[Claims] 1. An undercoat paint containing 1 to 20 parts by weight of a vinyl copolymer is applied to at least one surface of a steel sheet, and then baked with respect to 100 parts by weight of a paint containing an anticorrosive pigment and a coloring pigment. after forming the undercoat paint film of 10 .mu.m, with respect to 100 parts by weight of the binder, primer coating of the same system color average particle diameter 1~80μm colored particles 150 to 200 parts by weight 及 of
0.1 to 1 with a metallic substance having a particle size of 5 to 250 μm
Apply topcoat paint containing 0 parts by weight and bake, 12-25μ
m top coat film is formed, The manufacturing method of the precoat steel plate characterized by the above-mentioned.