JP2000064064A - Enameled sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an enameled sheet having high lightness and high glossiness and excellent in post-bendability. SOLUTION: This enameled sheet is the one in which at least either face of a base substrate has an enameling layer contg. 10 to 25 wt.% pigment of 0.2 to 0.26 μm average particle size and 20 to 50 μm film thickness. As the pigment, a white pigment is preferable and white titanium oxide pigment is more preferable. Moreover, as a glaze used at the time of forming the enameling layer, the one essentially consisting of P2O5 is preferable.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an enamel plate having high brightness, high gloss, and excellent post-bending workability. 2. Description of the Related Art Enamel products are provided with a vitreous (glaze) enamel layer on the surface of a metal substrate serving as a base.
It has corrosion resistance, weather resistance and chemical resistance. Since this enamel product often requires a design, high brightness, that is, the enamel layer is sufficiently colored, and in addition to excellent shielding properties such that the underlying metal substrate cannot be seen through, high gloss is required. Often. In addition, workability is required, which does not impair the appearance due to cracking, peeling, or the like even when bending. [0003] Of these, it is generally known that the above requirements can be satisfied by including a color pigment in the enamel layer and increasing the film thickness of the enamel layer. For example, Japanese Patent Publication No. 6-43256 discloses that, on an aluminum-plated steel sheet, titanium oxide as a white pigment is mixed in a proportion of 50 parts by weight or more with respect to 100 parts by weight of a transparent frit of glaze mainly composed of P ₂ O _5. A high brightness enamel product provided with an enamel layer included therein is disclosed. However, according to the study of the present inventor, when a large amount of pigment is added to the transparent glaze to such an extent that the substrate metal is not transparent as described above, a high brightness (shielding property) can be obtained, but the enamel surface is severe. It turned out that unevenness was produced and high gloss could not be obtained. Further, it is difficult to remove the dirt substance that has entered the concave portions on the uneven surface by washing with a detergent such as a solvent, so that not only the surface dirt remains but also the gloss is reduced due to dirt. [0005] The enamel layer is usually thickened to about 100 µm because the thicker the film, the higher the brightness can be obtained. However, when the enamel plate is bent (post-bending), if the enamel layer containing a large amount of pigment has a large film thickness as described above, for example, about 70 μm as shown in the examples of the publication, Cracks are noticeable and a product with poor appearance is obtained. As described above, an enamel plate satisfying all of brightness, gloss, and post-bending workability has not yet been obtained.
In addition, when providing an enamel layer using only a transparent frit of glaze mainly composed of P ₂ O ₅ on an aluminum plated steel sheet,
It is known that when the film thickness is 10 to 50 μm, an enamel product having excellent workability can be obtained (Japanese Patent Publication No. 6-43257). I can't get it. Further, even if an enamel layer containing 50 parts by weight or more of a normal pigment with respect to 100 parts by weight of the transparent frit is provided in a thickness of 10 to 50 μm, the problem of poor gloss is still solved. Not done. SUMMARY OF THE INVENTION An object of the present invention is to provide an enamel plate having high brightness, high gloss, and excellent post-bending workability. SUMMARY OF THE INVENTION The present inventor has found that when an enamel layer is formed by adding a pigment to a glaze, a pigment having an average particle size in a very limited range is used. It was found that an unexpected effect of obtaining high brightness and high gloss even when the addition amount of the enamel layer was small and the thickness of the enamel layer was small was obtained. Furthermore, even if this enamel plate is subjected to post-bending processing, cracks are not noticeable, and the appearance is good. That is, the enamel plate according to the present invention has an average particle size of 0.2 to 0.2 on at least one surface of the base substrate.
6 to 10% by weight of a pigment having a thickness of 20 to
It is characterized by having an enamel layer of 50 μm.
The pigment is preferably a white pigment, and more preferably a white titanium oxide pigment. The glaze used for forming the enamel layer preferably has P ₂ O ₅ as a main component. DETAILED DESCRIPTION OF THE INVENTION The term "enamel" refers to a vitreous coating obtained by applying (glazing) an inorganic glass powder as a glaze on the surface of a substrate such as a metal and baking it. The enamel plate according to the present invention includes an enamel layer having a pigment having an average particle size of 0.2 to 0.26 μm on at least one surface of a base substrate at 10 to 25% by weight and a film thickness of 20 to 50 μm. have. Hereinafter, the present invention having such a configuration will be specifically described. The base substrate is usually a metal plate such as an iron plate, a steel plate, or an aluminum plate. These metal plates are subjected to a plating treatment such as zinc plating, aluminum plating, aluminum zinc alloy plating, iron zinc alloy plating, a chemical conversion treatment, and a chromate treatment. A metal plate subjected to a surface treatment such as a treatment is used. The base substrate may be made of a material other than a metal plate as long as the material can withstand the enamel firing temperature. Among these, it is particularly preferable to use a metal plate that has been subjected to surface treatment such as plating and has corrosion resistance, weather resistance, and the like. In the present invention, an enamel layer containing a pigment having a specific particle size in a specific amount is provided on at least one surface of the substrate. The enamel layer containing a pigment as described above is usually formed by firing an enamel glaze obtained by adding a pigment to a vitreous glaze as a base material, and specifically, a specific pigment as described below is applied to the vitreous glaze. Is added to prepare a mixture slurry (enamel glaze), and then the slurry is glazed on a substrate and fired. [0013] The glaze to be glaze base material, can be used widely known glaze, for _{example, Ti O 2, Si O 2} , Zr O
R ₂ such as RO ₂ compounds such as P ₂ O ₅ and V ₂ O _5
2 O _{5 compound, Sb 2 O 3, Al 2} O 3, B 2 O 3 R 2 O 3 based compounds such _{as, Na 2 O, K 2 O} , R 2 , such as Li ₂ O
O-based compound, Zn O, Ba O, RO-based compounds such as Ca O, can be used glaze obtained from mineral raw materials such as fluoride-based compounds such as ZrF _4, AlF _3. A glaze may be prepared by combining these. Among them, as described later, in order to prevent a decrease in the hiding power or discoloration of the pigment, a glaze having a low firing temperature is preferable, and an R ₂ O ₅ glaze is particularly preferable, and P ₂ O ₅ is mainly used. Glazes included as components are preferred. Here, the main component is a component contained in the glaze at a rate of 50% by weight or more. The glaze is melted by firing to form a film, and usually does not become a particle-shaped pigment in the formed enamel layer. In the present invention, the pigment has an average particle size of 0.20 to 0.26 in the enamel layer.
μm, preferably in the range of 0.21 to 0.25 μm. The particle size of pigments generally used in the past has a wide range from about 0.1 μm to about 0.3 μm, but in the present invention, the pigment used is contained in the enamel layer with substantially the same particle size. Therefore, the average particle size is 0.20 to 0.26 μm, preferably 0.21 to
A pigment of 0.25 μm is used. If a pigment having an average particle diameter within the above range is used, two or more kinds of pigments having different particle diameters can be used in combination. Further, it is preferable that the average particle diameter is within the above range, the particle diameter is small, and the particle diameters are uniform. Here, the average particle diameter refers to a particle 1000 measured using an electron microscope or the like.
It means the average value of the particle size of the individual pieces. The pigment having the above average particle size can be obtained by dry and / or wet pulverization, and then classification by sedimentation, wind power, or the like. In the present invention, the average particle size is in the above range,
Known pigments can be widely used as long as they do not melt even at the firing temperature. Specifically, white pigments such as titanium oxide and zinc oxide, and non-white pigments such as iron oxide and chromium oxide can be used. Different kinds of pigments may be used in combination. Among these, a white pigment excellent in concealing property of the underlying substrate is preferable, and among the white pigments, titanium oxide particularly excellent in concealing property is preferable. Titanium oxide has two types of crystal phases, a rutile type and an anatase type. Either type may be used.
A rutile type having a high ability to absorb and block a wavelength in a visible light region is preferable. In addition, in titanium oxide, the transformation of the crystal phase from rutile type to anatase type occurs at 600 ° C. or higher,
When firing at a high temperature, problems such as a decrease in hiding power and discoloration are likely to occur. Therefore, in order to obtain a high-brightness enamel using rutile-type titanium oxide as a pigment, the firing temperature is preferably 550 ° C. or lower. In the present invention, the shape of the pigment is not particularly limited, such as a granular shape, a spherical shape, and a flaky shape, but a granular shape or a spherical shape is preferable in order to improve the dispersibility of the mixture slurry. When the pigment having the above-mentioned average particle size is contained in the enamel layer, the pigment sufficiently absorbs visible light, the shielding property is improved, and a high brightness can be obtained. Low, high gloss is obtained. The average particle size is 0.20μ
If it is less than m, the pigment cannot absorb and block the visible light, resulting in insufficient lightness. On the other hand, if it exceeds 0.26 μm, the surface will have many irregularities and the gloss will be insufficient. This will be described more specifically. For example, titanium oxide, which is a white pigment, can absorb and block wavelengths in the visible light region if the average particle size is 0.2 to 0.3 μm.
However, the particle size of the pigment affects the unevenness of the enamel surface. The larger the particle size of the pigment, the larger the unevenness of the enamel surface, and the smaller the particle size, the smaller the unevenness of the enamel surface.
Specifically, when a titanium oxide pigment having a so-called “large particle size” having an average particle size exceeding 0.26 μm is used, irregularities on the surface of the enamel become large and high gloss cannot be obtained. Further, the average particle size is 0.
When a titanium oxide pigment having a so-called “small particle size” of less than 20 μm is used, the pigment cannot absorb or block a wavelength in a visible light range, and high brightness cannot be obtained. As described above, 0.2-0.26 μm
When a pigment having a specific average particle size of m is included, the effect of lightness is significantly larger than when a pigment having a particle size of about 0.1 μm to about 0.3 μm, which is generally used, is included. The finding that high brightness and high luminosity can be obtained even with a small pigment content has been found by the present inventors. In the present invention, the above pigment is contained in the enamel layer finally fired and formed in an amount of 10 to 25% by weight, preferably 15 to 23% by weight. The remaining component forming the enamel layer is usually the glaze, but may contain other components as long as the object of the present invention is not impaired. The pigment content is 10% by weight.
If less than, the lightness is insufficient, if more than 25% by weight,
Surface irregularities increase, resulting in insufficient gloss. The thickness of the enamel layer is 20 to 50 μm. When the film thickness is less than 20 μm, gloss and lightness are reduced,
On the other hand, if it exceeds 50 μm, the appearance of the post-bent portion tends to be impaired. The film thickness is preferably 25 to 45 μm, more preferably 25 to 40 μm, and particularly preferably 25 to 37 μm.
m. In the present invention, the thickness of the enamel layer is 20 to 50 μm
Although it is thinner than a conventional general thickness, high brightness is exhibited even with such a film thickness. This is probably because a pigment having an average particle diameter in a specific range was used. Specifically, the lightness (L) measured according to JISZ-8729
Value) is usually 86 or more, preferably 88 or more, particularly preferably 90 or more.
The gloss measured at 5 ° is usually at least 70%, preferably at least 75%. Further, the enamel plate having the enamel layer as described above is also excellent in bending workability (post-bending workability), hardly peels off even when the enamel plate is bent, and has an appearance without generating cracks on the surface. Excellent enamel products can be obtained. Next, an example of a method for producing an enamel plate according to the present invention will be described. The above-mentioned enamel plate is obtained by glazing a slurry (enamel glaze) containing a glaze and a specific pigment on at least one surface of the base substrate and firing the slurry to form an enamel layer. The glaze is RO ₂ type mentioned above,
A mineral raw material such as R ₂ O ₅ is crushed and mixed, heated and melted, and then rapidly cooled to obtain a glassy material. Then
A slurry is prepared from the glaze and the pigment. The slurry may contain a dispersant and the like in addition to the glaze, pigment, and water. Usually, a slurry is prepared by mixing and pulverizing a glaze to which a pigment, water, a dispersant and the like have been added using a ball mill, a mortar, a grinder or the like. The obtained slurry is applied (glazed) on the substrate surface in such an amount that the thickness of the finally obtained enamel layer falls within the above range. At this time, it is preferable that the surface of the substrate is degreased, washed, and if necessary, plated, and then the slurry is glazed. Glazing may be performed by any of a coating method using a brush, a roller, or the like, a spraying method using a spray, an electrostatic coating, a roll coater method, a transfer paper method, and the like.
Whether the surface to be glazed is one side or both sides of the substrate may be selected as necessary. The substrate to be glazed may be not only a flat substrate but also a bent substrate. The glazed substrate is kept at a high temperature in an electric furnace, a gas furnace, a tunnel furnace, a batch furnace or the like, and the slurry on the substrate is fired to form an enamel layer. The firing temperature may be a temperature at which the glaze melts and a temperature at which the pigment does not melt, but is preferably a temperature at which crystal transformation of the pigment does not occur as described above. EXAMPLES In the following Examples or Comparative Examples, the composition of glaze (frit) used for glazing the underlying substrate is shown in Table 1.
Shown in Example 1 The following enamel glaze (slurry) was prepared such that the content of titanium oxide in the enamel layer was 20% by weight. To 100 parts by weight of glaze A having the composition shown in Table 1, 25 parts by weight of titanium oxide having an average particle size of 0.2 μm as a pigment, 35 parts by weight of water, and 0.5 part by weight of a dispersant (sodium pyrophosphate) were added. , And pulverized and mixed to prepare a slurry. This slurry was glazed on the surface of the alloy-treated hot-dip galvanized steel sheet and fired at 530 ° C. to form an enamel layer, thereby obtaining an enamel plate (sample). The obtained sample was evaluated for glossiness, lightness, enamel film thickness, and appearance of a bent enamel product. Table 2 shows the results. (Lightness) Lightness (L value) was measured using a color difference meter in accordance with JISZ-8729 "Display method of object color". The L value is an index indicating the concealability of the substrate. If the L value is 86 or more, the underlying metal substrate (steel plate) cannot be seen through. (Glossiness) The opening angle was set to 4 by a photometer.
The gloss was measured at 5 °. If the glossiness is 70% or more, the glossiness is high. (Appearance after bending) A 90 ° bending operation was performed, and the appearance of the bent portion was visually observed to check for peeling of the enamel and cracks on the surface. Those with no peeling of the enamel and no surface cracks were evaluated as good. (Enamel Thickness) The enamel thickness was measured by observing the cross section of the enamel with an electron microscope. (Examples 2 to 10) As shown in Table 2, except that the pigment content, the pigment particle size, the film thickness, the glaze, and the like were changed, a sample was made in the same manner as in Example 1 and a sample was produced. The same evaluation was performed. Table 2 shows the results. (Comparative Examples 1 to 6) As shown in Table 2, except that the pigment content, pigment particle size, film thickness, glaze, etc. were changed,
A sample was prototyped in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 2 shows the results. [Table 1] [Table 2] According to the present invention, an enamel plate having high brightness, high gloss, and excellent post-bending workability is provided.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Masato Kumagai             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba             Iron Research Institute (72) Inventor Kyoko Hamahara             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba             Iron Research Institute (72) Inventor Toshihide Suzuki             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba             Iron Research Institute (72) Inventor Koji Watanabe             2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture             Kawasaki Construction Materials Co., Ltd. (72) Inventor Hiroshi Nagaishi             2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture             Kawasaki Construction Materials Co., Ltd. (72) Inventor Fumio Togashi             2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture             Kawasaki Construction Materials Co., Ltd.

Claims (1)

Claims: 1. A pigment having an average particle size of 0.2 to 0.26 μm is coated on at least one surface of a base substrate in an amount of 10 to 25% by weight.
An enamel plate comprising an enamel layer having a thickness of 20 to 50 μm.