JP2003221688A - Process for manufacturing porcelain enamel steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for manufacturing a porcelain enamel steel sheet having a porcelain enamel surface sufficiently smooth for practical use at a low cost, without deteriorating the original characteristics of porcelain enamel having excellent properties such as hardness, weather resistance, restorability by washing, heat resistance and non-combustibility. <P>SOLUTION: The process for manufacturing the porcelain enamel steel sheet includes a step wherein a slurry for porcelain enameling is sprayed onto the surface of a substrate for glazing and subsequently baked. Here, the slurry has a static surface tension of ≤50 dyne/cm and an apparent viscosity, measured by an E-type viscometer, of ≤500 mPas (rotation speed: 100 rpm). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an enameled steel sheet, and in particular, it is suitable for a marker board, a blackboard, a tunnel interior material, an interior / exterior material for construction, etc. due to its excellent surface smoothness. The present invention relates to a method for manufacturing a steel plate.

[0002]

2. Description of the Related Art Painted steel sheets and enameled steel sheets are used as steel sheets having functions such as corrosion resistance, chemical resistance, weather resistance, and designability to improve the life of base steel sheets. Enameled steel sheets have superior properties in comparison with coated steel sheets in terms of hardness, weather resistance, wash recovery, heat resistance, nonflammability, etc.
The enamel surface is not smooth, so-called "orange peel" is formed, and the surface may be inferior in smoothness.

The surface smoothness of the enameled steel sheet used for marker boards and the like is emphasized, and in that case, the "orange peel" of the enameled surface is higher than that of the painted steel sheet.
The presence of is often detrimental to the evaluation of enameled steel sheets. However, heretofore, there has been no knowledge of a technique for improving the problem that "orange peel" is formed on the surface of an enameled steel sheet.

[0004]

Therefore, the object of the present invention is to put the enamel into practical use without impairing the original properties of enamel, which have excellent properties such as hardness, weather resistance, washing recovery, heat resistance, and incombustibility. An object of the present invention is to provide a method capable of manufacturing an enameled steel sheet having a sufficiently smooth enameled surface at a low cost.

[0005]

Therefore, as a result of intensive studies, the present inventors have found that when a enamel slurry is glazed on the surface of a base material, the surface of the enamel surface is excellent in smoothness if it is not already in a smooth coating state. It has been found that a enamel steel sheet having the above can not be obtained. As a result of further investigation, it was found that the use of enamel slurry with a low static surface tension increases the wettability between the slurry and the base material and is effective for smoothing the slurry in the initial coating state during glaze application. It was It was also found that the use of a low-viscosity slurry increases the wettability between the slurry and the base material, and is effective in smoothing the slurry due to the leveling property after glazing.

Based on the above findings, the present invention has a static surface tension of 50 dyne / cm or less and an apparent viscosity of 500 mPa.s (rotation speed: 100 r by an E-type viscometer).
Provided is a method for producing an enameled steel sheet, which comprises a step of spraying a enamel slurry having a particle diameter of pm) or less onto a surface of a base material, applying glaze, and then firing.

The static surface tension can be adjusted by adding a surfactant to the enamel slurry. Furthermore, it is preferable that the specific gravity of the enamel slurry is 1.3 or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing an enameled steel sheet of the present invention (hereinafter referred to as the "method of the present invention") will be described in more detail below. The method of the present invention is a method of producing a enamel steel sheet having an enamel layer by glazeing and baking a enamel slurry on the surface of a base material which is a base material.

In the method of the present invention, the base material which is a base material for forming an enamel layer on the surface by glaze is not particularly limited, and ordinary steel plates such as SPP, SPCC, SPHC and SS,
Stainless steel sheets such as ferrite type stainless steel sheet (SUS430 series), austenite type stainless steel sheet (SUS304 series), ferrite heat resistant steel sheet (SUH409)
Uncoated metal plate such as aluminum plate, aluminum plate, etc., and plated steel plate such as aluminum plated steel plate, aluminum zinc alloy plated steel plate, zinc iron alloy plated steel plate, or enamel steel plate thereof.

The base material does not particularly require pretreatment, but degreasing treatment is effective for improving the wettability of the enamel slurry. Further, in order to improve the adhesion between the steel plate as the base material and the enamel layer, surface treatment such as plating treatment may be performed. For example, chromate treatment, phosphate treatment,
Surface treatment such as plating treatment with nickel, cobalt, molybdenum, manganese or the like, alkali etching treatment or the like may be performed. In particular, when the adhesion between the base steel sheet and the enamel layer is insufficient, nickel plating treatment or alkali etching treatment promotes the reaction between the base steel sheet and the enamel layer to improve the adhesion. ,It is valid.

In the present invention, the enamel slurry to be glazed on the surface of the base material is a frit made of feldspar, soda ash, boric acid, silica sand or the like, colored with titanium oxide, zinc oxide, iron oxide, cobalt oxide or the like. Add pigments, gairome clay, which is added to improve dispersibility, or additives such as potassium chloride and nitrite, if necessary, and mix them with a dispersion medium such as water. And then dispersed.

This enamel slurry enhances the wettability between the slurry and the base material, contributes to smoothing of the slurry in the initial state of application during glaze, and is effective in forming an enamel surface having excellent smoothness. And the static surface tension is 50 dyne /
cm or less, preferably 35 dyne / cm or less is used. The static surface tension of the enamel slurry is 50
When it exceeds dyne / cm, the wettability deteriorates and the droplets independently exist. As a result, unevenness occurs on the surface even in a wet state, and smoothness cannot be obtained.

A method for adjusting the static surface tension of the enamel slurry to lower it to 50 dyne / cm or less is to add a surfactant. The method of adding a surfactant for adjustment is effective because once added, it can stably maintain a low surface tension and has little change over time.

The surfactant used is not particularly limited and may be an anionic, cationic or amphoteric surfactant, or a nonionic surfactant, and is appropriately selected as necessary. The amount of surfactant added is
The amount is 0.01 part by weight or more, preferably 0.1 part by weight, based on 100 parts by weight of the liquid content and the solid content of the enamel slurry. Since surfactants are generally organic substances, if a large amount is added, the enamel color turns black, so 10
A proportion of less than or equal to parts by weight is preferred.

In addition, the enamel slurry has high wettability between the enamel and the enamel steel sheet, contributes to smoothing of the slurry due to the leveling property after glazing, and is effective in forming an enamel surface having excellent smoothness. , E-type viscometer indicates that the conical rotor has a rotational speed of 100 r.p.m. p. m. The apparent viscosity (hereinafter, simply referred to as "viscosity") measured at 500 is 500 mPa · s or less, preferably 100 mP.
It is adjusted so that it is not more than a · s. In the present invention,
The E-type viscometer is a cone-plate type (cone-plate type) rotary viscometer.

Adjust the viscosity of the enamel slurry to 50
Examples of the method for reducing the viscosity to 0 mPa · s or less include a method of adding an inorganic substance such as clay, silica powder, and nitrite, and a method of adding water, and the method of adding water is sufficient. However, if a large amount of water is added to reduce the specific gravity of the slurry, solid-liquid separation may occur during leveling, which may cause "runoff" or "unevenness" on the enamel surface. Therefore, when water is added to reduce the viscosity of the slurry, the specific gravity of the slurry is required to be 1.3 or more in order to prevent "flowing out" and "unevenness" on the surface of the enamel.

The enamel slurry can be produced according to a conventional method, and the method is not particularly limited. For example, a slurry can be prepared by adding an additive such as gairome clay, a color pigment, and water to a frit and crushing and mixing by, for example, ball milling.

A spraying method is preferable as a method of glazeing the enamel slurry on the substrate in view of workability and cost. The spray method is preferably a spray method, a rotary atomization method, or the like.
Further, like electrostatic coating, a static voltage may be applied to the slurry during spraying, and the base material may be grounded to attract more of the slurry to the base material by an electrostatic force to improve the slurry yield. In the spraying method, the spraying pressure is preferably 0.1 MPa or more and less than 1.0 MPa.

The glazed substrate can be fired to bake an enamel layer on the surface of the substrate. The firing temperature is preferably 650 ° C to 950 ° C, particularly preferably 700 to 8
The temperature is 50 ° C., and the firing time is preferably 0.5 minutes to 30 minutes.
It's a minute. At the time of this baking, the base material may not be sufficiently dried or may be in a state of containing water.

In the method of the present invention, the formation of the enamel layer by glazing and firing the enamel slurry may be repeated once or plural times. For example, the undercoating enamel slurry is glazed on the surface of the base material and baked to form an undercoating enamel layer, and further the finishing enamel slurry is applied on the undercoating enamel layer and baked to form a finishing enamel layer. Two enamel layers may be formed by the step of forming. When forming two enamel layers,
The undercoat enamel layer and the finishing enamel layer may be composed of the same enamel component or different enamel components.

The method of the present invention is not limited to the case where a metal plate is coated with the enamel slurry to produce a enamel steel plate, and the enamel slurry of the present invention is applied to a substrate made of a material other than the metal plate. Needless to say, it can be applied to the production of enamel products by coating.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically by way of Examples and Comparative Examples of the present invention.

(Examples 1 to 9) The amount of nickel plating adhered on both surfaces of a normal steel plate having a plate thickness of 0.6 mm was 100 on both surfaces.
A nickel-plated steel sheet having a mg / m ² nickel-plated layer was prepared, and degreased and alkali-etched.

Next, the undercoating slurry having the composition shown in Table 1 was sprayed on the nickel-plated steel plate so that the wet film thickness became about 50 μm, and then baked at 810 ° C. for 2 minutes in an electric furnace to prepare the undercoating enamel. A steel plate was obtained.

The finishing slurry having the composition shown in Table 2 was added to Table 3
Surfactant shown in (Surfinol 4 manufactured by Nisshin Chemical Industry Co., Ltd.
65 ") and water for adjusting specific gravity were added to prepare a slurry for glaze having the static surface tension and the apparent viscosity shown in Table 3. This glazed slurry was glazed by spraying on an undercoated enamel steel plate so that the wet film thickness was about 120 μm.

(Comparative Examples 1 and 2) To the finishing slurry having the composition shown in Table 2, the surfactant shown in Table 3 and water for adjusting the specific gravity were added, and the static surface tension and apparent viscosity shown in Table 3 were obtained. A slurry for glazing having was prepared. This slurry for glazing was glazed on an undercoated enamel steel plate by spraying so that the wet film thickness was about 120 μm.

Here, Examples 1 to 9 and Comparative Example 1
In 2 and 2, the static surface tension was measured using a Kyowa CBVP type surface tension meter A3-SOL manufactured by Kyowa Scientific Co., Ltd.
The apparent viscosity is E type viscometer (VISCO made by Tokyo Keiki Co., Ltd.)
The apparent viscosity at a rotation speed of 100 rpm was measured by a NIC ED type).

Next, the enamel steel sheets glazed with the finishing glazing slurry obtained in Examples 1 to 9 and Comparative Examples 1 and 2 were fired in an electric furnace at 790 ° C. for 2 minutes to obtain finished enamel steel sheets. Obtained.

The smoothness of the obtained finished enameled steel sheet is
BYK Gardner Wave-Scan DOI
It evaluated based on the Wd value measured by (orange peel measuring device). The lower the Wd value, the higher the smoothness. The results are shown in Table 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

According to the method of the present invention, it is possible to produce an enameled steel sheet having no "orange peel" and excellent in the smoothness of the enamel surface. The obtained enameled steel sheet can be suitably used as a marker board, a blackboard, and a tunnel interior material, and can be used as an interior / exterior material for construction to improve the aesthetics of the interior and exterior walls of the building.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasumasa Fukushima             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. (72) Inventor Masato Takagi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. (72) Inventor Kazuhiro Hayashi             2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture             Narashino Factory of Kawatetsu Construction Materials Co., Ltd. (72) Inventor Masao Taguchi             2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture             Narashino Factory of Kawatetsu Construction Materials Co., Ltd. (72) Inventor Shinichi Noma             390 Osato, Koshigaya, Saitama Japan Fellows Co., Ltd.             Company Tokyo Sales Office

Claims (3)

[Claims] 1. A static surface tension of 50 dyne / cm or less and an apparent viscosity of 500 mPa measured by an E-type viscometer.
A method for producing an enameled steel sheet, which comprises a step of spraying a enamel slurry having a s (rotational speed: 100 rpm) or less on the surface of a base material, applying glaze, and then firing. 2. The enamel slurry has a static surface tension adjusted by the addition of a surfactant.
A method for manufacturing an enameled steel sheet according to. 3. The method for producing enamel steel sheet according to claim 1, wherein the specific gravity of the enamel slurry is 1.3 or more.