JPH039052B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an enamel glaze composition that can be fired at a low temperature of 750°C or lower. Structure of conventional examples and their problems In general, the enameling treatment of iron plates involves adding clay as a suspending agent, colloidal silica, and NaNO ₂ , NaAlO ₂ , MgCO ₃ as a stopping agent to an enamel frit, which has a coefficient of thermal expansion slightly smaller than that of a steel plate. The resulting slip is mixed with an electrolyte such as, water as a solvent, and milled, and the resulting slip is pickled, glazed on a nickel-treated iron plate, and fired. Among the defects that appear on the surface of the enamel layer processed in this way, defects directly caused by the glaze include tearing, cracks, hair lines, bubbles, and copper heads. These defects are caused by boron and alkali eluted from the hollow frit. The occurrence of these defects is influenced by slip manufacturing conditions, slip storage conditions, enamel film thickness, film drying conditions, handling of dried utensils, firing conditions, etc. In particular, in the case of low-melting enamel that requires the addition of a large amount of B ₂ O ₃ or alkali components to the enamel frit, the above-mentioned defects tend to occur early. However, low-melting enamel saves resources and energy, and because it is not kept above the _A1 transformation point of steel, there is less deformation during firing and thin plates can be used.
Due to its high dimensional accuracy, it is possible to design complex shapes. It has many advantages such as less generation of carbon dioxide gas due to desorption of hydrogen gas adsorbed or occluded in the steel plate and reaction of carbon between the slip and the steel plate, and fewer defects such as nail skipping, bubbles, and pinholes. Therefore, many low-melting enamels have been developed so far. However, most of these are low softening point hollow frits with large amounts of PbO, Sb ₂ O ₃ and P ₂ O ₅ added, which poses problems of food hygiene, environmental pollution, and danger during frit manufacturing. Ta. Therefore, a low softening point frit containing no harmful substances was proposed in Japanese Patent Application No. 19243/1983. This low softening point frit contains at least SiO ₂ , B ₂ O ₃ ,
_{Na2O , K2O} , ZnO and _F2 , _Al2O3 , _ZrO2 ,
At least one intermediate oxide selected from the group of TiO ₂ and 31 to 39% by weight of SiO ₂ ,
_{B2O3 13-21} % by weight, _Na2O14-22 % by weight, _K2O1
~5 wt%, ZnO13~20 wt%, F2 ₂ ~10 wt%,
[Al ₂ O ₃ ] + [ZrO ₂ ] + [TiO ₂ ] = 2 to 9% by weight,
Al ₂ O ₃ ≦5% by weight, ZrO ₂ ≦5% by weight, TiO ₂ ≦5
% by weight of the hollow frit. This low softening point hollow frit is made of CdS-based red pigments and TiO ₂
It is well suited to pigments such as red, yellow, pink, green, blue, black, white, etc., and can be freely produced. However, when this low softening point enamel frit is baked on a steel plate with a general enamel glaze composition as shown below, the frit: 100 parts by weight Frog's eye clay 4 to 7 parts by weight Colloidal silica 0 to 1 part by weight Silica powder (325 Particle size that passes through a mesh sieve)
0 to 6 parts by weight NaNO ₂ 0 to 0.25 parts by weight Pigment 2 to 6 parts by weight Water 45 to 70 parts by volume If used for a short time after milling, the surface condition, gloss, and color of the enamel will be improved. In good condition. However, if the slip is exposed to high temperatures, such as 35℃ in summer,
When stored at temperatures around 50°C, serious defects such as increased slip viscosity, tearing, cracks, hair lines, crack heads, orange skin, bubbles, and changes in color were observed. In particular, tearing, cracking, and hairlines occurred after only a few hours of storage at high temperatures. In general, low-softening point hollow frits elute more boron, alkali, etc. than high-temperature types. It is thought that this eluted component impairs the wetting (compatibility) between the glaze and the steel plate, or that the eluted component forms crystalline substances such as borax between the frit particles, causing tearing, cracks, and hairlines. . In particular, the low softening point hollow frit of the above composition has excellent color development, but has the drawbacks of eluting a large amount of B and alkali during the slip, and of having a large surface tension when the frit melts. , it was very prone to tearing and cracking. Conventionally, as a method to prevent tearing and cracking, a small amount of urea was added to the slip after milling. However, when urea-added slips are stored at high temperatures, large bubbles form within a short period of time. This is thought to be because urea or urea decomposition products are adsorbed to clay or colloidal silica, and the adsorbed urea or urea decomposition products are desorbed at high temperatures near the firing temperature, resulting in large bubbles being generated on the enamel surface. In the case of low-melting enamel, adsorption of urea or urea decomposition products is promoted by the alkali etc. eluted from the frit, and foaming occurs quickly. When urea was added to a slip using the low softening point hollow frit and stored at 35°C, foaming occurred within several hours. Therefore, in the case of low-melting enamel, whether urea is added during milling or after milling, it is important to keep the milling and slip storage temperatures below 30°C in the summer to avoid high temperatures. The disadvantage was that it had to be managed. OBJECTS OF THE INVENTION An object of the present invention is to provide a low-melting enamel glaze composition that can be fired at a temperature of 750° C. or lower and can be stored for a long period of time. Structure of the Invention The low melting enamel glaze composition of the present _invention has _a low softening point enamel frit as _a main component _, and a layered adsorbent represented by the formula _Mg Basically, it is contained as an inhibitor. In addition, 2X+4=
Y, X>0. The layered adsorbent represented by Mg _x Al ₂ (OH) _y CO ₃・zH ₂ O is a hollow frit with a low softening point.
It is preferably 0.2 to 3 parts by weight per 100 parts by weight. Furthermore, the pot life of the slip of the low softening point hollow frit with the following composition is Mg _x Al ₂ (OH) _y CO ₃ .
By being able to lengthen the zH ₂ O adsorbent,
This brings us closer to practical use of low-melting enamel that can be applied once and has excellent color development. The composition of the low softening point hollow frit is at least SiO ₂ , B ₂ O ₃ ,
_{Na2O , K2O} , ZnO and _F2 , _Al2O3 , _ZrO2 ,
At least one intermediate oxide selected from the group of TiO ₂ and 31 to 39% by weight of SiO ₂ ,
_{B2O3 13-21} % by weight, _Na2O14-22 % by weight, _K2O1
~5 wt%, ZnO13~20 wt%, F2 ₂ ~10 wt%,
[Al ₂ O ₃ ] + [ZrO ₂ ] + [TiO ₂ ] = 2 to 9% by weight,
Al ₂ O ₃ ≦5% by weight, ZrO ₂ ≦5% by weight, TiO ₂ ≦5
Weight%. The layered adsorbent with the formula Mg _x Al ₂ (OH) _y CO ₃ zH ₂ O seems to adsorb or ion-exchange B and alkali components eluted from the hollow frit, thereby preventing tearing and cracking. . If the adsorbent is contained in an amount exceeding 3 parts by weight per 100 parts by weight of the enamel frit, the working temperature will rise, bubbles will occur, and the gloss will deteriorate. Furthermore, if the amount is less than 0.2 parts by weight, there will be little effect on preventing tearing or cracking, and if a frit is used in the summer where a large amount of alkali elutes, especially when the glaze thickness is thick (approximately 200 μm or more), tearing or cracking may occur.
Cracks and hairlines are likely to occur. As for the method of adding the adsorbent represented by the above formula into the glaze composition, mill addition is preferable. but,
Even in this case, it is desirable to keep the milling time short (within 1 hour) and to prevent the temperature in the mill from exceeding 30°C. Description of Examples To obtain the low melting enamel glaze composition of the present invention,
First, make a low softening point enamel frit. The order is that the raw materials for each component are mixed according to the desired frit composition. After thorough dry mixing, 1100~1300
Melt by heating at °C. Since the melting temperature and time change the composition ratio of the final frit, it is necessary to carefully control the melting temperature and time. It is important to allow vitrification to proceed for 20 to 40 minutes after dissolving the raw materials, stirring as necessary. If the temperature is maintained at the melting temperature for too long, the alkali components and _F2 components will sublimate, so avoid keeping it too long. After melting, the glass is placed in water and rapidly cooled. When this is dried, a low softening point hollow frit is obtained. Enamel frit 100 obtained in this way
3 to 9 parts by weight of clay, colloidal silica, etc. as a suspending agent, sodium nitrite (NaNO ₂ ), sodium aluminate (NaAlO ₂ ) as a stopping agent,
1 part by weight or less of magnesium carbonate (MgCO ₃ ), etc.
Further, 40 to 70 parts by volume of water are added to 10 parts by weight or less of the pigment, silica powder, and hydrated borax, and the mixture is ground and mixed using a ball mill or the like. At this time, at the same time, the adsorbent represented by the above formula is
Add 0.2 to 3 parts by weight. Here, if the temperature inside the mill is controlled to be as low as 30°C or lower, the pot life of the slip after being taken out of the mill will be longer. Regarding the particle size of the slip, the 200 mesh (74 μm) residue in 50 ml of the slip is 1 to 7 g when spray glazed, and 15 g or less when dip glazed, and the coarser the 200 mesh (74 μm) residue, the better the coarser the 200 mesh (74 μm) residue is, as this will reduce the elution of the frit components. . The enamel glaze composition thus obtained is sprayed or dip-glazed onto pickled and electroless nickel-plated steel utensils, dried, and fired (for example, at 690° C. or higher for 4 minutes) to form an enamel film. Next, examples will be described together with comparative examples.
(Manufacture of low softening point hollow frit) First, the raw materials shown in Table 1 below were blended in the proportions shown in the same table to prepare formulations 1 and 2 for low softening point hollow frit.

【table】

【table】

[Table] Then, this mixture was mixed and put into an alumina crucible, and after melting and clarifying at 1100 to 1300°C, it was put into water and cooled. As a result, low softening point hollow frits G-1 and G-2 shown in Table 2 were obtained. Both hollow frits G-1 and G-2 are low softening point frits that can be fired at temperatures below 750°C, but G-
In case of No. 1, the wetting of the frit and the steel plate is poorer, and the amount of alkali eluted into the slip is also greater. The evaluation method in Table 2 was as follows. (1) Tablet test (fluidity of the frit) The fluidity of the glass frit was tested by taking 2 g of the frit with a particle size that would pass through a 200-mesh sieve.
The sample is placed in a mold and press-molded at a pressure of 1 ton/cm ² to form a tablet with a diameter of 12.7 mm.
Then, the sample was placed on a steel plate that had been pickled and electroless nickel plated, heated at 690°C for 5 minutes, and the flow diameter of the sample was measured with calipers. This value is an evaluation that combines the hardness and wettability of the frit. (2) Amount of frit dissolved in hot water 5 g of frit with a particle size that passes through a 200 mesh sieve but not a 300 mesh sieve.
After immersing in 100 c.c. of distilled water and boiling for 1 hour, remove the supernatant liquid and use a methyl orange indicator to remove the eluted alkaline components by 0.1N−H ₂ SO ₄
The amount consumed was used as a measure of the amount of alkali eluted. (Manufacture of enamel frits) After drying and coarsely pulverizing the low softening point enamel frits G-1 and G-2 obtained as described above, the mill additives shown in Table 3 below were added to the same table. They were mixed in the proportions shown.

[Table] Next, add 3 kg of frits of the formulation shown in Table 3.
The mixture was placed in a No. 10 pot mill and mixed and pulverized at about 75 rpm for 1 hour. At this time, the milling temperature is below 30℃, and the slip particle size (50c.c. 200 mesh residue)
was adjusted to be 1 to 7 g. The condition of the enamel coating on the slips was checked immediately after being taken out of the mill, and the slips were stored in a constant temperature bath or constant temperature water bath at the storage temperature shown in Table 3, and the condition of the enamel coating was checked periodically. Enamel processing was performed under the following conditions. Base material: Steel type SPP material Dimensions Size 100mm x 100mm, thickness 0.6mm Pretreatment Pickling weight loss 400-500mg/dm ^2Nickel adhesion amount 14-20mg/dm ^2Glazing : Spray method Enamel film thickness: 150-180μm Drying Method: Far-infrared drying firing conditions: Firing time was 3 minutes and 40 seconds, and the firing temperature is shown in Table 4. Table 4 shows the results of checking the pot life under the above conditions.

【table】

[Table] Mg _x Al ₂ (OH) _y CO ₃ for Fritz G-1
The effect of zH ₂ O was compared to that of urea without the addition of anti-tearing agent. As shown in Table 4, when the slip is refrigerated, there is no practical problem even if no inhibitor is added. However, at room temperature around 35℃, for example in summer,
When storing one frit of slip, the slip becomes unusable in about 4 hours unless a tearing/cracking inhibitor is added. When urea was tried as an inhibitor, large bubbles were generated within 6 hours. Therefore, these inhibitors are also not practical. In comparison to these, layered adsorbents, e.g.
Adding Mg _4.5 Al ₂ (OH) ₁₃ CO ₃・3.5H ₂ O, Mg ₆ Al ₂ (OH) ₁₆ CO ₃・4H ₂ O not only delays tearing and cracking, but also prevents the formation of large bubbles. It is considerably slower than
In the summer, it is possible to obtain products that can be used for 1 to 2 days without refrigeration. In Example 6 and Comparative Examples 6 and 7, the pot life characteristics of the slip of Frit G-2 were shown. As shown in Table 4, even low softening point hollow frits have good fluidity and are sufficiently usable for practical use without the addition of tearing/crack preventive agents. However, even in Frit G-2, an inhibitor is added if there is a risk of tearing or cracking occurring due to impact during handling of the utensil. In this case as well, it is better to use the adsorbent represented by the above formula than urea because it takes a longer time to generate bubbles. Effects of the Invention As described above, the low melting enamel glaze composition of the present invention is resistant to tearing, cracking, and large bubbles. In particular, even when using a low softening point enamel frit which has poor fluidity as a frit, poor wettability with a steel plate, and a large amount of alkali elution, it is possible to provide a low melting enamel glaze composition that can be satisfactorily used even in summer. Conventional low-melting enamel has minimal deformation, strength deterioration, pinholes, and nail skipping, and is resource-saving.
While having many features such as energy saving,
Because a large amount of B ₂ O ₃ and alkaline components were leached from the frit, the pot life of the slip was short, which greatly hindered its practical application. However, the present invention can greatly bring it closer to practical application.

Claims (1)

[Claims] 1. Main component is low softening point hollow frit,
A low-melting enamel glaze composition that can be fired at 750°C or lower and contains a layered adsorbent represented by the formula Mg _x Al ₂ (OH) _y CO ₃ zH ₂ O as a tearing and crack preventive agent. . 2. The low melting enamel glaze composition according to claim 1, wherein the adsorbent is contained in an amount of 0.2 to 3 parts by weight based on 100 parts by weight of the enamel frit. 3 The low softening point hollow frit is at least
_SiO2 , _B2O3 , _Na2O , _K2O , _ZnO and _F2 ,
At least one intermediate oxide selected from the group of Al ₂ O ₃ , ZrO ₂ and TiO ₂ , and SiO ₂
31-39 wt%, _13-21 wt% _B2O3 , 14 wt% _Na2O
~22 wt%, _K2O 1-5 wt%, ZnO 13-20
Claim 1, which is a hollow frit containing 2 to 10% by weight of _F2 and 5 to 9% by weight of one type of intermediate oxide, and 2 to 9% by weight in total. The low melting enamel glaze composition according to item 1 or 2.