JPS616147A - Glaze composition for porcelain enamel having low melting point - Google Patents

Abstract

PURPOSE:To prevent generation of tearing and cracks, etc. and to permit storage of slip for a long period by mixing zeolite to a glaze compsn. for porcelain enamel calcinable at low temp. consisting essentially of porcelain enamel frit having low softening temp. CONSTITUTION:A porcelain emamel frit having low softening point is prepd. consisting of 31-39wt% SiO2, 13-21wt% B2O3, 14-22wt% Na2O, 1-5wt% K2O, 13-20wt% ZnO, and 2-10wt% F, and contg. 2-9wt% intermediate oxide selected from Al2O3, ZrO2, and TiO2. Further, 0.2-3pts.wt. zeolite as a tearing and crack inhibitor is added to 100pts.wt. porcelain enamel glaze compsn. consisting essentially of the porcelain enamel frit and being capable of calcination at <=750 deg.C to obtain an aimed compsn. usable without refrigeration even in summer season.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an enamel glaze composition that can be fired at a low temperature of 750° C. or lower.

Conventional structure and its problems Generally, the enameling process for steel machinery uses enamel frit, which has a coefficient of thermal expansion slightly smaller than that of steel machinery, and a suspending agent of frog's eye clay.
Colloidal silica, NaNO2, N as a stopping agent
Electrolytes such as aAlO2, MgCO3, and water as a solvent are mixed 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 processed in this way, defects directly caused by the glaze include tearing, cracks, hair lines, bubbles, and conover heads. These defects are caused by boron and alkali dissolved from the enamel frit. The occurrence of these defects is determined by the slip manufacturing conditions, slip storage conditions, enamel film thickness, film drying conditions, handling of dried utensils, etc.
It is affected by l+j2 depending on the firing conditions, etc.

Particularly in the case of low-melting enamel, in which a large amount of B2O3 or alkali components needs to be added to the enamel frit, the above-mentioned defects occur early.

However, low-melting enamel saves resources and energy, and because it cannot be kept above the A1 transformation point of steel,
) There is little deformation during firing, allowing for thin handling; (2) High dimensional accuracy allows for the design of complex shapes; (3) Desorption of hydrogen gas adsorbed or occluded in steel sheets, and prevention of slip and steel sheets. Less carbon dioxide gas is generated due to carbon reactions,
It has many advantages such as fewer defects such as nail skipping, bubbles, and pinholes.

Therefore, many low-melting enamels have been developed so far. However, many of these have low softening point enamel frits with large amounts of pbo%5b203 and P2O5 added, which pose problems in food hygiene, environmental pollution, or danger during frit production.

Therefore, a low softening point frit that does not contain harmful substances was proposed in JP-A-58-1403427.

This low softening point frit is at least 51o2, B2O
5, Na 20, F20, ZnO and F2 and Ae2
o6, ZrO2, and at least one intermediate oxide selected from the group of TiO□, and 5i0231 to 39% by weight (hereinafter simply expressed as %)
0313-21% N&2014-22% 201-5% ZnO13-20% F2 2-10% [A1206] + [ZrO2] + [TlO2] = 2-9
wt% Al2O, 55 wt%, Zr0256 wt%, 1
3. This low softening enamel frit contains CdS-based red pigment and TlO.
Compatible with 2-based pigments, including red, yellow, pink,
You can freely create colors such as green, blue, brown, black, and white.

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/Lica 0 to 1 part by weight Silica powder (326 Passed through the second sieve) 0 to 6 parts by weight NaNO2' O-0.25 parts by weight Pigment
2 to 6 parts by weight Water 45-b If used for a short time after milling, the surface condition, gloss, and color tone of the hoe will be good. but,
When slips are stored at high temperatures, for example around 35° C. in the summer, serious defects such as increased slip viscosity, tearing, cracks, hair lines, conoper heads, orange skin, bubbles and color changes occur. In particular, tearing, cracking, and hairlines occurred after only a few hours of storage at high temperatures.

In general, low softening (enamel frits) elute more boron, alkali, etc. than high-temperature types. These eluted components may impair the wetting (compatibility) between the glaze and the steel plate, or the eluted components may be present between the frit particles. It is believed that crystalline substances such as borax may form, resulting in tearing, cracking and hairlines.

In particular, the low softening point enamel frit with the above composition has excellent color development, but it has the drawbacks of eluting a large amount of boron and alkali during slipping, and that the surface tension of the frit is high when melted. Therefore, tearing and cracking were extremely likely to occur.

Conventionally, as a force method to prevent tearing and cracking, a small amount of urea was added to the slip after milling. However, when urea-doped slips are stored at high temperatures, 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/lica, 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. Adding urea to the slip using the low softening point enamel frit,
When stored at 36°C, foaming occurred within a few hours.

Shidaka-C, for low-melting polyurethane, when adding urea during milling, it is necessary to pour it so that the mill temperature does not become high. Even when adding urea after milling, it is necessary to 1. The slip storage temperature must be controlled to avoid high temperatures (below 30°C). There was a drawback that it was dull.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a low-melting glaze composition which can be fired at a temperature of 750 DEG C. or lower and can be stored as a slip for a period of one year.

Structure of the Invention The low melting enamel glaze composition of the present invention is based on a low softening point enamel frit as a main component and zeolite as a tearing and crack preventing agent.

It is preferable that 2 to 3 parts by weight of zeolite be added to 100 parts by weight of the low softening point enamel frit, and it is also highly effective for the low softening point enamel frit with the following composition, and improves the slip resistance and life. zeolite adsorbs harmful ions (1) and strengthens the drying film (1), which makes it possible to extend the drying film length.Thus, it is possible to bring one-shot low-melting enamel with excellent color development closer to practical use. The composition of is at least 51o2, B2
O3, Na2O, F20. ZnC) Oyobi F2 and Al
2O2, ZrO2, and at least one intermediate oxide selected from the Ti020 group, Si0□ 31-39% by weight, B2O3 13-21% by weight, Ha20 14-21 1% by weight, and 20 1-5% by weight. ZnO 13-20% by weight F2 2-10% by weight [Ag2O,] + [ZrO2] + [T1o2] -2-9
Reprint% Al2O3≦6%, 210255% by weight
, 710256% 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 excess of 3 parts by weight per 100 parts of frit, the working temperature will rise.
If the amount is less than 0.2 parts by weight, there will be almost no effect on preventing tearing or cracking, and if a frit with a very large amount of tW such as alkali is used in the summer, the glazed film will be damaged. When it is thick (approximately 200 μm or more), deering, cracks, and hair lines are likely to occur.

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 keep the temperature in the mill from exceeding 30°C.

Description of Examples In order to obtain the low melting enamel glaze composition of the present invention, first a low softening point enamel frit is prepared.

The raw material of each component is prepared in accordance with the desired frit composition. After thorough dry mixing, 1100~13oo℃
Heat for 7 hours to melt. Since the melting temperature and time change the final composition ratio of the frit, it is necessary to carefully control the melting temperature and time. It is important to allow the vitrification to proceed for 20 to 40 minutes after 7'6 decomposition of the rough stone, and to stir it every 1.1 seconds as necessary. If R1: Melting temperature 1 is maintained for too long, the alkali components and F2 components will sublimate, so do not keep it too long.
People and quench. Dry and rub this for 6 inches to obtain a low softening point enamel frit.

To the thus obtained Ho (1-Fri 100 Jushabu), add 1f of Frog's eye viscosity, colloidal/Suroku, etc. as a suspending agent.
~9 parts by weight, 1 part by weight or less as a stop adjustment agent, sodium aluminate, magnesium carbonate/rum, etc., 1 part by weight or less of pigment, and 40 parts by weight of other silica powder, hydrated borax, and water. To the amount of water is added, and the mixture is ground and mixed using a ball mill or the like.

At this time, 11 parts of zeolite is added at the same time. Here, if the mill temperature is controlled to <30''C or less, the bot life of the slip after being removed from the mill will be extended.

The particle size of the slip is 200 meth/slip csoml.
(approximately 74μ residual liquid, 1 to 7 if spray glazing)
), when applying the glaze by dipping, it is preferable that the glaze is 169 or less, and as coarse as possible, the elution of frit components will be reduced.

The enamel glaze composition obtained in this way is pickled,
Glaze the steel utensils that have been electrolessly treated with spray glaze C1 dip, dry, and then fire (for example, 6
90°C or higher for 4 minutes) to form an enamel film.

Next, examples will be explained with reference to comparative examples and examples. .

[Production of low softening point enamel frit 11] First, the raw materials shown in Table 1 were blended in the proportions shown in the same table to prepare formulations 1 and 2 for low softening point enamel frit.

Table 2 (unit weight %) Then, mix this mixture and put it in an aluminum pot,
After melting and clarifying at 1100°C to 1300°C, it was poured into water and cooled.

As a result, the low softening point hollow loaf IJ7)G in Table 2
-1 and G-2 were obtained.

Hollow frit G-1. Although both G-2 and G-2 have a low softening point frit that can be fired at 750'', G-1 has poorer wetting with the steel plate and a larger amount of alkali is eluted during slipping.

The evaluation method in Table 2 was as follows.

(1) Tablet test (frit fluidity PC) The fluidity of glass frit is determined by the particle size that passes through a 200-horn sieve. /C4 pressure to form a tufflet with a target diameter of 12.7 mar.

Then, the sample was placed on a steel plate that had been pickled and treated with electroless nickel, 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) Hot water bath for frits 5g of frits with a weight of 20 to 300 menonyu to 10
After immersing in 0CG distilled water and boiling for 1 hour, take the -1 clear solution and drop it using a menalore/no indicator.
The alkaline component was 0. Titration of 1N-H2SO4-C was carried out, and the amount consumed was calculated as one unit of eluted alkaline gas.

[Manufacture of pouro slip]

Low softening point Borlauf') obtained as described above (4)
After drying and coarsely pulverizing G-1 and G-2, mill additives shown in Table 3 were added in small proportions.

(Hereinafter in the margin) Next, add 9 minutes to frit 3 of the formulation shown in Table 3,
Approximately 75 r, p, m by putting it in the bot mill of e.

The mixture was mixed and ground for 1 hour. At this time, the mill temperature is 30°
(: Below, the particle size of the slip (50 cc of 200 ml of residual liquid) was adjusted to be 1 to 71.

The state of the enamel film on the slip was checked immediately after being taken out of the mill, and the slip was stored in a constant temperature bath or a constant temperature water bath at the storage temperature shown in Table 3, and the state of the enamel film was periodically checked.

The enamel treatment was carried out under the following conditions.

Profiteering; ■Kogami: SPP material, ■Size/1. :Size 100K
Mx'+oo, thickness 0.6ff ■Preface]! f! , : Pickling weight loss value 400~soo#+9
．． / dnf nickel adhesion meter 14-20urg 7 mountain No. 1
2 Glazing, spray method Enamel film thickness: 150-1807+ m Drying method, far infrared drying Firing conditions: Firing time was 3 minutes and 40 seconds, firing temperature is shown in Table 4.

Table 4 shows the results of checking potripes under the conditions described in 1-.

Table 4 The effect of zeolite on Frit G-1 was compared to the effect of no anti-tearing agent and to the effect of urea.

As shown in Table 4, if the slip is refrigerated, there is no problem even if no inhibitor is added. but,
When G-1 frit slips are stored at room temperature near 35°C, for example in the summer, the slips become unusable in about 4 hours unless a tearing/cracking inhibitor is added.

Therefore, 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 (eg, "Hitachange" manufactured by Wako Tsumugi Kogyo Co., Ltd., Permutit Go).

(Palm Chit, made in the United States) delays the formation of tear links and cracks, and also significantly slows the formation of large bubbles compared to urea, so it can be used for 1 to 2 days in the summer without refrigeration. You can get something that will last.

Example 4 and Comparative Examples 6 and 7 show the pot life characteristics of the G-2 slip/,-0 As shown in Table 4, even a low softening point enamel frit has good fluidity and has good fluidity and no dissolution. In the case of a frit with a small amount of alkali-11, the level of 11 is sufficient for practical use without adding tearing/crack prevention LL cutting. .

However, Frit G-2 also suffers from tearing and cracking due to the impact of handling the utensils.1. If there is a risk of L-, add an inhibitor. 1. In this case, it is also better to use decaolide than urea, as it takes a longer time to generate and break up foam. 3. 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, as a frit, it has poor fluidity and wettability fl with the steel plate.
Even when a low softening point enamel frit with a large amount of alkali elution is used, a low melting enamel glaze composition that can be satisfactorily used even in summer can be provided.

Conventional low-melting enamels have many features such as less deformation, strength deterioration, pinholes and porosity, and are resource- and energy-saving.
Since a large amount of 2 and alkali components were eluted, the pot life of the slip was short, which was a major hindrance to its practical use. But 1
, the present invention can greatly bring the technology closer to practical application.

Claims (3)

[Claims] (1) Main component is low softening point enamel frit, 750
A low-melting enamel glaze composition which can be fired at temperatures below 0.degree. C. 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 enamel frit is at least SiO_2
, B_2O_3, Na_2O, K_2O, ZnO and F_2, and at least one intermediate oxide selected from the group of Al_2O_3, ZrO_2, TiO_2, containing 31 to 39% by weight of SiO_2, B_2O_3
13 to 21% by weight, 14 to 22% by weight of Na_2O,
1 to 5% by weight of K_2O, 13 to 20% by weight of ZnO,
Claim 1 or 2, 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. The low melting enamel glaze composition described in Section 1.