JPH0310584B2 - - 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) There are many advantages such as less generation of carbon dioxide gas due to desorption of hydrogen gas adsorbed or occluded in the steel and reaction between the slip and carbon of the steel plate, and fewer defects such as nail skipping, bubbles, and pinholes. be. 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 such as food hygiene, environmental pollution, and dangers in 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 ,}
At least one intermediate oxide selected from the group of _TiO2 , _SiO2 31-39% by weight (hereinafter simply expressed as %), _{B2O3 13-21} %, _Na2O14-
22%, _K2O1 ~5%, ZnO13~20%, _F22 ~10%,
[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 ₃ ≦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, frit 100 parts by weight frog's eye clay 4-7 colloidal silica 0-1 silica powder (325 parts by weight) passed through a sieve)
0-6 〃 NaNO ₂ 0-0.25 〃 Pigment 2-6 〃 Water 45-70 parts by volume If used for a short time after milling, the surface condition, gloss, and color tone of the enamel will be good. . However, if the slip is heated to a high temperature, for example 35℃ in summer,
If stored at
The occurrence of serious defects such as orange peel, bubbles, and changes in color tone was 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 slip, and the drawback of high surface tension when the frit is melted. , it was very prone to tearing and cracking. Traditionally, 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, 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 contains low softening point enamel frit as a main component, and contains 2MgO, 6SiO ₂ ,
It basically contains a layered adsorbent represented by XH ₂ O as a tearing and crack preventing agent. The amount of the layered adsorbent represented by the above formula is 0.2 to 3 parts by weight per 100 parts by weight of the low softening point hollow frit.
Parts by weight are preferred. Furthermore, it is highly effective against low softening point hollow frits with the following composition, and the pot life of the slip can be extended by the layered 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 with _Al2O3 , _{ZrO2 ,}
At least one intermediate oxide selected from the group of TiO ₂ , SiO ₂ 31-39%, B ₂ O ₃ 13
~21%, _Na2O14 ~21%, K2O1 _~ 5%, ZnO13~
20%, _F2 2-10%, [ _{Al2O3 ]} + [ _ZrO2 ] + [ _TiO2 ] = 2-9% by weight,
Al ₂ O ₃ ≦5% by weight, ZrO ₂ ≦5% by weight, TiO ₂ ≦5
Weight%. The layered adsorbent represented by the formula 2MgO, 6SiO ₂ , or XH ₂ O adsorbs or ion-exchanges boron and alkali components eluted from the hollow frit.
It seems to strengthen the dry film to prevent tearing and cracking. This layered adsorbent is fritted
If the content exceeds 3 parts by weight per 100 parts by weight, the working temperature will rise, bubbles will occur, and the gloss will deteriorate. In addition, if the amount is less than 0.2 parts by weight, there is almost no effect on preventing tearing or cracking, and if a frit is used in the summer, which causes a large amount of alkali to be eluted,
Especially when the glaze is thick (approximately 200 μm or more), tearing, cracking, and hair lines are likely to occur. As for the method of adding the layered adsorbent into the glaze composition, mill addition is preferable. However, even in this case, it is desirable to shorten the milling time (within 1 hour) so that the temperature in the mill does not exceed 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 parts by weight, 3 to 9 parts by weight of frog's eye clay, colloidal silica, etc. as a suspending agent, up to 3 parts by weight of sodium nitrite, sodium aluminate, magnesium carbonate, etc. as a stopping agent, and up to 10 parts by weight of pigment, etc. Add 40 to 70 parts by volume of water to silica powder and hydrated borax, and grind and mix with a ball mill or the like. At this time, 0.2 to 3 parts by weight of an adsorbent represented by the formula 2MgO, 6SiO ₂ or XH ₂ O is added at the same time. here,
By controlling the temperature inside the mill to be as low as 30°C or less, the pot life of the slip after being taken out of the mill will be extended. 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 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, mill additives shown in Table 3 were added in the proportions shown in the 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.

[Table] 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, pre-treatment: Pickling weight loss value 400
~500mg/dm ² Nickel deposition amount 14~20mg/d
^m2 Glazing: Spray method Enamel film thickness: 150-180μm Drying method: Far infrared drying Firing conditions: Firing time is 3 minutes 40 seconds, firing temperature is shown in Table 4 The results of checking the pot life under the above conditions are as follows. It is shown in Table 4.

[Table] 2MgO, 6SiO ₂ for frit G-1,
The effectiveness of the XH ₂ O adsorbent was compared to that of tearing, no crack inhibitor added, and 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 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, layered adsorbents represented by the above formula (for example, Kyoward 600 Kyowa Chemical Industry Co., Ltd.
By adding urea (manufactured by Co., Ltd.), the occurrence of tearing and cracking is delayed, and the generation of large bubbles is also considerably slower than that of urea. can be obtained. 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 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, the use of the adsorbent is better than urea because it takes a longer time to generate bubbles. Effects of the invention As described above, 2MgO, 6SiO ₂ ,
A low-melting enamel glaze composition containing a layered adsorbent represented by XH ₂ O is resistant to tearing and cracking, as well as large bubbles. In particular, even when using a low softening point enamel frit which has poor fluidity and wettability with a steel plate and which 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.
Although it has features such as energy saving, the pot life of the slip is short due to the large amount of B ₂ O ₃ and alkaline components eluted from the frit, which poses a major problem in 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 2MgO.6SiO ₂ .XH ₂ O as a tearing and cracking 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.