JPS5827214B2 - Clay-free enamel glaze - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an enamel sinter, and particularly to an enamel sinter suitable for obtaining an enamel having both a smooth enamel surface and high withstand voltage characteristics.

Natural mineral clay plays a very important role in the crawling industry.

This natural mineral clay is generally kaolin, hallosite,
It is obtained from serpentine, allophene stone, mica minerals, vermiculite, montmorillonite minerals, chlorite, mixed-layer clay minerals, etc. In particular, a clay called frog's eye clay is often used as a flotation agent in the enamel industry.

Hereinafter, clay as used in this application refers to natural mineral clays (belonging to the above-mentioned categories).

In the past, it was essential to include clay in the formulation of ``Hauro-shitagusuri''.

This is because it not only prevents sedimentation of the slurry slurry, but also acts as a regulator of the rheological properties of the slurry.

In addition, the present inventor found that the addition of clay develops a foam structure in the enamel, improving the mechanical properties of the enamel, but inhibiting the smoothness of the enamel surface and deteriorating the voltage resistance. It was.

However, simply reducing the amount of clay from the base mixer not only deteriorates the workability of the base mix as described above, but also increases the number of bubbles in the base mix even though they are smaller. This fact is acknowledged by the inventor and is also described in the literature.

(e.g. B., Walker & J., Campbell
, 1. V.E.

Bulletin, 18(12) 1967) On the other hand, Japanese Patent Publication No. 51-16451 can be mentioned as prior art related to the present invention.

However, in the above invention, instead of using clay, a water-soluble biopolymer composition called Polytranto FS containing polymer polysaccharide and scleroglucan is used, but this has the same effect as clay as a flotation agent. Therefore, even if clay is not used, the above object of the present invention cannot be achieved when using Polytranto FS.

This will be made clear by comparing the Examples and Comparative Examples described later.

Therefore, it has been the long-held desire of researchers to improve the quality and appearance of finished grains by removing clay from the base grain mixture and reducing the number of bubbles in the grain. In reality, it is extremely difficult to reduce the amount of clay, which is usually around 7%, to around 4% at the minimum.
The existence of ~2% has been considered unavoidable.

However, according to the research of the present inventor, a small amount of one or more of silica gel, alumina sol, and colloidal silica was blended into the frit without adding clay, and the particle size was reduced to a normal particle size (approximately 10 to 15 μm).
) The slurry obtained by wet milling to finer particles with an average particle size of 6.5 μm or less is dried and then fired. It was found that the smoothness of the enamel surface obtained by applying the glazing was dramatically improved, and at the same time, it had high electrical insulation properties.

The present invention does not contain clay as a floating agent, and contains silica gel,
This is an enameled slurry containing one or more of alumina sol and colloidal silica, which is obtained by wet grinding so that the average particle size of solid particles is 6.5 μm or less.

Silica gel, etc. mentioned above (hereinafter referred to as colloidal refractory material)
is a colloidal refractory material that does not melt at the firing temperature of wax, which forms a hydrophilic colloid and has the function of preventing settling of frit particles.

The appropriate content is about 1 to 7%. The pulverized particle size needs to be 6.5 μm or less, which is the value obtained by measuring the dry slurry with a Fisher set average particle size meter, and it is desirable to make it as small as possible from an industrial technical point of view. Sedimentation of the slurry is significant, making the scouring process difficult.

Although the significance of incorporating colloidal refractory materials in the present invention is not yet clear, the combination of these substances delays the melting of the underlayment at the initial stage of firing, and the formation of the refractory material due to shrinkage of the film before firing. It is presumed that the presence of micro-cracks promotes deaeration of the underfill, leading to a reduction in air bubbles.

As mentioned above, in the present invention, it is possible to obtain a smooth enamel surface that could not be obtained conventionally, and in contrast to the conventional undercutting which causes pinholes at about 1500V, in the present invention, a high level of at least 3000V can be obtained. Can withstand voltage.

Furthermore, by increasing the smoothness of the wafer surface, a secondary effect of improving its corrosion resistance can also be expected, which is of great practical significance in the warou industry.

The underglaze of the present invention is not limited to the base material to be glazed, and can be applied to all conventional glazing methods.

In addition, the glaze of the fly is generally composed of a bottom glaze and a finishing glaze applied thereon, and although the present invention relates to the bottom glaze, if interpreted in a broad sense, it does not necessarily have to be the same as the known glaze. It is not necessary to contain adhesion oxide, and directly 1
The hook may be a light-colored undercoat that lacks an adhesive on pretreated base metals.

Hereinafter, the implementation of the present invention will be specifically shown, and the effects of the present invention will be demonstrated by comparing it with a glaze made by conventional enamel technology.

Example 1 The average particle size of slurry was 6.0 to 6.5 with the mill formulation shown below.
A slurry for milling is obtained to obtain a slurry with a thickness of μm.

Mill blend #2232 (commercially available frit) 30 parts by weight #223
6(// ) 30 //=l=l=22
40 (// ) 40 // Silica gel
4 Sodium aluminate
Q, 3 tt water
45 This slurry was glazed by dipping into a pot having a diameter of 18 cm and a thickness of 1.0 mm, which had been pretreated by a known method, and after drying, it was fired at 850° C. for about 3 minutes.

When the obtained underglazing enamel was observed under a microscope under oblique light, the bubbles were very small and the number of them was small.

In addition, a pinhole test was conducted at 3000V (DC) using a THE-20A pinhole detector manufactured by Sancora Electronic Research Institute, but no pinholes were observed.

The foam structure of the obtained underglazing enamel layer is shown in FIG. 1 in a micrograph.

(Enlargement magnification: 75 times. The same applies hereinafter) Comparative Example 1 Milling was performed using the following conventional mill formulation for milling so that the average particle size of the slurry was 10 to 11 μm, and the resulting slurry was milled in the same manner as in Example 1. Glaze the pot and dry it at 850'C for 3
Bake for a minute.

Mill blend #2232 (commercially available frit) 30 parts by weight 1223
6(// ) 30 //#2240(/
/ ) 4Q // Frog-eye clay
7 parts by weight silica stone
5 Hydrous borax 0.5 Sodium nitrite 0.25 When the obtained sagging enamel (contains clay and has large particle size) was observed under a microscope under oblique light, it was found that there were many large bubbles between the small bubbles C. The number of pinholes was also very large, and when a pinhole test was conducted in the same manner as in Example 1 (at the same voltage as in Example 1), countless pinholes were drawn.

The foam structure of the obtained enamel layer is shown in FIG. 2 as a micrograph.

Comparative Example 2 The slurry was milled using the following mill formulation so that the average particle size was 6 to 7 μW, the resulting slurry was glazed in the same pot as in Example 1, and after drying it was glazed at 850°C for 3 minutes. .

Mill blend #2232 (commercially available frit) 30 parts by weight #223
6(// ) 30 //#2240(/
/ ) 4Q tt silica gel
3 Frog-eye clay
1 〃Hydrous borax 0.5〃Sodium aluminate 0.2〃Sodium nitrite
0.1 water
45 When the obtained underglaze enamel (containing clay) was observed under a microscope under oblique light, it was found that although the bubbles were smaller than those of Comparative Example 1, the number of bubbles was actually larger.

The foam structure of the obtained underglazing enamel layer is shown in FIG. 3 as a micrograph.

Example 2 The average particle size of the slurry was 5.8 to 6.0 with the mill formulation shown below.
The resulting slip was spray glazed onto a panel with a width of 300 mm and a length of 600 mm, which had been pretreated by a known method, and after drying was fired at 830° C. for 3.5 minutes.

Mill blend #2232 (commercially available frit) 30 parts by weight 1223
6(// ) 40 //-#2240(/
/ ) 40 〃Silicon stone
5 Alumina sol 1 part by weight Silica gel 3 Sodium nitrite 0.1 Water
40 When the bubble structure of the enamel layer of the obtained underglaze was observed under oblique lighting, it was confirmed that the bubbles were extremely small and the number thereof was small.

This micrograph is shown in FIG.

Furthermore, when the pinholes obtained were tested using the same pinhole detector as in Example 1, 3000
■ (DC) No pinholes were detected at all.

On the other hand, a conventionally known titanium milky white top glaze was spray glazed on top of the obtained bottom glaze enamel, and after drying it was heated to 800°C.
When fired for about 3 minutes, the enamel surface obtained was extremely smooth and had a so-called mirror-like finish.

Comparative Example 3 The average particle size of slurry was 4 to 4.5 μm with the mill formulation shown below.
The resulting slip was glazed on the same panel as in Example 2, dried and fired at 830° C. for about 3.5 minutes.

Mill blend #2232 (commercially available frit) 30 parts by weight #223
6(//) 30##2240(//
) 40 // Frog-eye clay
4 Alumina sol 1
〃Silicon stone 5〃Hydrous borax
0.5 Sodium nitrite
0.2 water
40 When the foam structure of the obtained sub-guzuri enamel layer was observed under a microscope under oblique illumination, it was found that although the size of the bubbles was relatively uniform, the number of bubbles was significantly large.

This micrograph is shown in FIG.

Furthermore, when a titanium opalescent glaze was applied on top of this glazed enamel in the same manner as in Example 2, and after drying, it was fired at 800°C for about 3 minutes. There was almost no difference from the upper enamel surface.

Example 3 The slurry was milled using the following mill formulation to have an average particle size of 5 to 6 μm, and the resulting slip was applied to a bathtub body pretreated by a known method to give an enamel thickness of 120 to 140 μm after firing.
It was glazed to give a thickness of μ, and after drying, it was fired at 850°C for about 6 minutes.

Mill blend #2232 (commercially available frit) 30 parts by weight #22
36(// ) 30 //#2240(
// ) 40 // Silica stone
15 Silica gel
5 Sodium aluminate 0.1
Sodium nitrite 0.1 When we cut out a part of the bottom of the obtained bathtub and examined the bubble structure using a microscope under oblique light, we found that the bubbles were very small and the number of bubbles was extremely small. .

This micrograph is shown in FIG. Further, a pinhole test was conducted on this bathtub body using the pinhole detector used in Example 1 at 4000V (DC), but no pinholes were detected.

Furthermore, this bathtub is glazed twice with a well-known titanium milky finish.
After repeated firing and finishing the final product, it was inspected with a THE-10A pinhole detector made by Sancola Electronics Laboratory.
A pinhole test was conducted at V (direct current), but no pinholes were detected.

Comparative Example 4 A slip milled using the same mill composition as in Example 3 so that the average diameter of the slurry was 8 μm caused severe sedimentation, and when the bathtub body was glazed, the glaze flowed by the time it dried, making it difficult to use. I couldn't.

Comparative Example 5 The slurry obtained by milling the slurry to an average particle size of 6 μm using the mill formulation specified in page 4, column 7, line 35 of Japanese Patent Publication No. 51-16451 was pretreated by a known method. 300imX 300mm (steel plate thickness 0.8ytw
) has a flat steel plate with an enamel thickness of 90 to 10 after firing.
It was spray glazed to a thickness of 0 μm, dried and then fired at 840°C for 3 minutes.

Mill blend #2232 (commercially available frit) 30 parts by weight #2236
(// ) 30 1/#2240(//
) 40 //Politrant F, S,
0.5 // Sodium nitrite
0.5 water
45 When the foam structure of the obtained underglazed enamel was observed under a microscope under oblique illumination, many large bubbles were observed and the surface of the enamel was extremely uneven.

This micrograph is shown in FIG.

Example 4 A frit having the formulation shown in Table 1 was melted at 13000G and rapidly cooled.

The oxide composition of the obtained frit is as shown in Table-2.

The three types of frits obtained were mixed with the following composition to achieve an average particle size of 3 to 3.
Milled to a thickness of 4 μm, the obtained slip was glazed to a thickness of 120 to 130 μm on a 20×20i enameling steel plate pretreated by a known method, and after drying,
C. for 3.5 minutes.

A pinhole test was performed on the obtained product using a pinhole detector at 5000 V (DC), but no pinholes were detected.

Mill compound frit 43 30 weight // /
I64 3Q //〃
/I6.5 40 〃Silica gel 2 〃Sodium nitrite
0.25 // water
45 In the above, substantially the same results were obtained even when colloidal silica was used instead of silica gel.

As is clear from the above-mentioned Examples and Comparative Examples, the enamel prepared by the underglazing of the present invention has a smooth enamel surface and high electrical insulation properties that cannot be obtained by conventional enamel technology.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing the foam structure of the enameled underglaze obtained in Example 1 of the present invention (magnification: 75 times; the same applies hereinafter). FIG. 2 is a microscopic photograph showing the foam structure of the enameled underglaze obtained in Comparative Example 1. FIG. 3 is a microscopic photograph showing the foam structure of the enameled underglaze obtained in Comparative Example 2. FIG. 4 is a micrograph showing the foam structure of the enameled underglaze obtained in Example 2 of the present invention. FIG. 5 is a microscopic photograph showing the foam structure of the enameled underglaze obtained in Comparative Example 3. FIG. 6 is a micrograph showing the foam structure of the enameled underglaze obtained in Example 3 of the present invention. FIG. 7 is a microscopic photograph showing the foam structure of the enameled underglaze obtained in Comparative Example 5.

Claims (1)

[Claims] 1 Contains frit that does not contain natural mineral clay as a flotation agent, contains one or more of silica gel, alumina sol, and colloidal silica, and is obtained by wet grinding so that the average particle size is 6.5 μm or less Enamel stain made of mud.