JPH039054B2 - - 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 steel plates involves using an enamel frit with a coefficient of thermal expansion slightly smaller than that of the steel plate, suspending agents such as frog's eye clay, colloidal silica, and stopping control agents such as NaNO ₂ , NaAlO ₂ , It is made by mixing an electrolyte such as MgCO ₃ with water as a solvent, milling it, pickling the resulting slip, glazing it on a nickel-treated iron plate, and firing it. 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 does not maintain the temperature above the _A1 transformation point of steel, it has (1) less deformation during firing, allowing the use of thin plates, and (2) high dimensional accuracy, making it possible to design complex shapes. It is possible,
(3) 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 between the slip and carbon of 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 JP-A-58-140342. This low softening point frit contains at least SiO ₂ , B ₂ O ₃ ,
_Na2O , _K2O , ZnO and _F2 with _Al2O3 , _{ZrO2 ,}
and at least one intermediate oxide selected from the group of TiO ₂ , SiO ₂ 31 to 39% by weight (hereinafter simply expressed as %) B ₂ O ₃ 13 to 21% Na ₂ O 14 to 22% K ₂ O 1-5% ZnO 13-20% F ₂ 2-10% [Al ₂ O ₃ ] + [ZrO ₂ ] + [TiO ₂ ] = 2-9 wt% Al ₂ O ₃ ≦5 wt%, ZrO ₂ ≦5% by weight, TiO ₂ ≦
It is a hollow frit with a content of 5% by weight. This low-softening 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 passed through the 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. Good, but slips at high temperatures, for example 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 boron and alkali during the slip, and of having a large surface tension when the frit melts. , it was very prone to tearing and cracking. Traditionally, as a method to prevent tearing and cracking,
After milling, a small amount of urea was added to the slip. 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, when adding urea to low-melting enamel during milling, care must be taken to ensure that the mill temperature does not become too high. The disadvantage was that it had to be controlled so that it did not reach high temperatures (below 30℃). 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 basically contains a low-softening point enamel frit as a main component and zeolite as a tearing and cracking preventive agent. The amount of zeolite is preferably 0.2 to 3 parts by weight per 100 parts by weight of the low softening point hollow frit. Furthermore, it is highly effective for low softening point hollow frits having the following composition, and the pot life of the slip can be extended by the action of adsorbing harmful ions and the action of strengthening the dry film of zeolite. As a result, it is possible to bring one-time, low-melting enamel with excellent color development closer to practical use. The composition of the low softening point hollow frit is at least SiO ₂ , B ₂ O ₃ , Na ₂ O,
Composed of K ₂ O, ZnO and F ₂ and at least one intermediate oxide selected from the group of Al ₂ O ₃ , ZrO ₂ and TiO ₂ , SiO 31-39% by weight B ₂ O ₃ 13-21 Weight% Na ₂ O 14-21% by weight K ₂ O 1-5% by weight ZnO 13-20% by weight F ₂ 2-10% by weight [Al ₂ O ₃ ] + [ZrO ₂ ] + [TiO ₂ ] = 2- 9% by weight Al ₂ O ₃ ≦5% by weight, ZrO ₂ ≦5% by weight, TiO ₂ ≦
It is 5% by weight. It is thought that zeolite adsorbs or ion-exchanges boron and alkali components eluted from the hollow frit, and also strengthens the dry film to prevent tearing and cracking. If zeolite is contained in an amount exceeding 3 parts by weight per 100 parts by weight of the frit, the working temperature will rise, bubbles will be generated, and the gloss will deteriorate; if it is less than 0.2 parts by weight, the tearing and crack prevention effect will be poor. When using a frit that has very little elution of alkaline substances during the summer, tearing, cracking, and hair lines are likely to occur, especially when the glaze thickness is thick (approximately 200 μm or more). As for the method of adding zeolite into the glaze composition, mill addition is preferable. However, 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
To the parts by weight, 3 to 9 parts by weight of frog's eye clay, colloidal silica, etc. as a suspending agent, 1% by weight or less of sodium nitrite, sodium aluminate, magnesium carbonate, etc. as a stopping agent, and 10 parts by weight or less of a pigment. In addition, 40 to 70 parts by volume of water is added to silica powder and hydrated borax, and the mixture is ground and mixed using a ball mill or the like. At this time, 0.2 to 3 parts by weight of zeolite is added at the same time. 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 steel utensils that have been pickled and electroless nickel-plated, dried, and then 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 were blended in the proportions shown in the same table to form Low Softening Point Enamel Frit Compounds 1 and 2.
I made it.

【table】

【table】

[Manufacture of hollow slips]

After drying and coarsely pulverizing the low softening point hollow frits G-1 and G-2 obtained as described above, the mill additives shown in Table 3 were added in the proportions shown in the table.

[Table] Zeolite; Vitachienji manufactured by Wako Pure Chemical Industries, Ltd.
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 deposit 14-20mg/dm ^2Glazing : Spray method Enamel film thickness: 150-180μm Drying method: Far infrared drying Firing conditions: Firing time The 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] The effect of zeolite on Fritz G-1,
If no tearing/crack preventive agent is added,
and compared with the effect of urea. 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 the summer, G-1
When storing frit slips, unless tearing and cracking are added, the slips become unusable after about 4 hours. When urea was tried as an inhibitor, large bubbles were generated within 6 hours. Therefore, these inhibitors are also not practical. Compared to these, zeolites (e.g. "Vitachienji" manufactured by Wako Pure Chemical Industries, Ltd., Permutit Co.
By adding ``Palm Chit'' (manufactured in the United States), it delays the occurrence of tearing and cracking, and the generation of large bubbles is also much slower than with urea, so it can be used without refrigeration for 1 to 2 days in the summer. You can get what you deserve. In Example 4 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 have a low amount of eluted alkali, so they can be put to practical use without the addition of tearing/cracking inhibitors. However, even in Fritt G-2, an inhibitor is added if there is a possibility that tearing or cracking may occur due to impact during handling. In this case as well, it is better to use zeolite than urea because it takes a longer time to generate bubbles. Effects of the Invention As described above, the low-melting enamel glaze composition containing the zeolite of the present invention is resistant to tearing, cracking, and large bubbles. In particular, even when using a low softening point enamel frit that has poor fluidity and wettability with a steel plate and has a large amount of alkali elution, it is possible to provide a low melting enamel glaze composition that can be used satisfactorily 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,
Since 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 use. However, the present invention can greatly bring the technology closer to practical application.

Claims (1)

[Claims] 1. Main component is low softening point hollow frit,
A low-melting enamel glaze composition which can be fired at 750°C or lower and which contains zeolite as a tearing and cracking preventive agent. 2. The low-melting enamel glaze composition according to claim 1, wherein the zeolite 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 hollow frit contains at least SiO ₂ ,
B ₂ O ₃ , Na ₂ O, K ₂ O, ZnO and F ₂ and Al ₂ O ₃ ,
It is composed of at least one intermediate oxide selected from the group of ZrO ₂ and TiO ₂ , and contains 31 to 39% by weight of SiO ₂ , 13 to 21% by weight of B ₂ O ₃ , and 14 to 22% of Na ₂ O % by weight, 1 to 5% by weight of K ₂ O, 13 to 20% by weight of ZnO,
Claim 1, which is a hollow frit containing 2 to 10% by weight of F ₂ and 5% by weight or less of the intermediate oxide in a total amount of 2 to 9% by weight; or 2. The low melting enamel glaze composition according to item 2.