JPS6257081B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing a voltage nonlinear low antibody. More specifically, we will introduce a voltage non-linear product mainly composed of zinc oxide used in non-gap lightning arresters that have a high resistance layer formed on the side of the element to prevent external flashover of the element when lightning impulses strike. This invention relates to a method for producing a low antibody. As a functional element of a lightning arrester, the conventional combination of silicon carbide and an air gap has been replaced by a non-linear voltage suppressor mainly composed of zinc oxide, which has recently become mainstream as a non-gap lightning arrester. This low antibody has zinc oxide as its main component and also contains several metal oxides such as bismuth oxide, antimony oxide, and cobalt oxide, and its excellent voltage nonlinearity eliminates the need for a gap. ,
In other words, it has the advantage of solving the problems of follow-on current interruption, gap adjustment, and discharge stability due to the use of a gap. On the other hand, the main function of lightning arresters is to absorb large current surges. At this time, if the surface condition of the side surface of the element is unstable and its resistance value is relatively lower than the internal resistance, external flash short may occur, element destruction, and increase in leakage current due to the formation of electrical circuits may occur, causing the arrester itself to deteriorate. There is a problem that can damage the lifespan of the machine. Prior to the use of silicon carbide, inorganic viscous materials were placed on the sides of the device and used to protect it. In the case of low voltage non-linear low voltage antibodies for low power applications, a resin layer such as epoxy resin is formed on the side surface of the device and has been used to prevent external flashover. Typical examples of side treatment methods for devices containing zinc oxide as the main component for normal power use include bismuth oxide,
Apply silicon oxide and antimony oxide to the sides.
A method is used in which a high-resistance layer is formed by firing at 800-1500°C and reacting with the element body. It can be seen, for example, from the description in JP-A-50-150896 that the high resistance layer on the side surface formed in this manner is useful for the stability of the element itself and for preventing external flashover. The composition of the ternary metal oxide of bismuth oxide, antimony oxide, and silicon oxide, which is considered desirable for ordinary electric power use, is conventionally composed of 0 to 20% mole of bismuth oxide (Bi ₂ O ₃ ), antimony oxide ( Sb ₂ O ₃ ) 5 to 50 mol%, silicon oxide (SiO ₂ ) 5
However, it has been found that the high resistance layer formed by coating and baking such a composition also has the following problems. That is, (1) There is a considerable density difference between each powder component, making uniform mixing difficult (d=8.9g/
cm ³ , d for silicon oxide = 2.3 g/cm ³ , d for antimony oxide = 5.2 g/cm ³ ), (2) There is also a large density difference between the mixed powder and the organic solvent, and if left in a paste state, the liquid-powder (3) After applying the paste, there is a large amount of sagging during drying.
Due to problems such as the inability to obtain a high-resistance layer of sufficient height, it is difficult to make the coating material uniform, resulting in extremely uneven coating, and the thickness is not sufficient. It has also been found that external flash flashing due to impulses is likely to occur due to the above-mentioned factors, leading to a decrease in yield. The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, the high-resistance layer forming materials provided on the side surfaces of the device include bismuth oxide 0-10 mol%, antimony oxide 55-90 mol%, silicon oxide 0- We have discovered a method for producing a voltage nonlinear low antibody characterized by firing a molded article coated with a composition consisting of 45 mol% while immersed in a substance containing zinc oxide as a main component, and have accomplished the present invention. It was about to be completed. To explain the present invention in detail, a high resistance layer is formed by a ternary composition consisting of bismuth oxide, antimony oxide, and silicon oxide because silicon oxide and antimony oxide react with zinc oxide, resulting in a highly insulating layer. This is because Zn ₂ SiO ₄ and Zn ₇ Sb ₂ O ₁₂ are generated, and bismuth oxide mainly plays a role as a flux and does not essentially constitute a component in the product. On the other hand, regarding the relationship between the amount of paste material of the same composition applied and the impulse withstand capacity, it has been found that a certain thickness or more is required to prevent flashover. Since the amount applied cannot be increased significantly above a certain value, if the amount of bismuth oxide is increased to more than 10 mol%, the amount of antimony oxide and silicon oxide will be relatively reduced, and the amount of antimony oxide and silicon oxide will be reacted and produced. This is disadvantageous for increasing the thickness of highly insulating materials. The amount of antimony oxide is less than 55 mol%,
If the amount of silicon oxide is more than 45 mol %, it is not preferable because it becomes difficult to obtain a homogeneous mixture or it becomes impossible to obtain an appropriate thickness of the reaction product. In addition, since bismuth oxide is more expensive than other metal oxides, it would be more preferable if a high resistance layer useful for impulse discharge resistance could be obtained without adding bismuth oxide. As mentioned above, the present invention reduces the amount of bismuth oxide to 0.
~10 mol% of a ternary or binary composition with a composition that is not used substantially is applied as a paste with an appropriate organic binder, and a molded article is embedded in a substance whose main component is zinc oxide. We succeeded in obtaining an excellent non-linear voltage-low antibody by calcination at a normal temperature. The present invention
A major feature is that the molded product coated with the above-mentioned specific composition is fired in zinc oxide, but even if zinc oxide contains trace amounts of other oxides, if the main component is zinc oxide, There is nothing wrong with that. Here, FIG. 1 shows the configuration of a non-linear element for a lightning arrester. In FIG. 1, reference numeral 1 indicates a high-resistance layer on the side surface of an element formed by the conventional method or the method of the present invention, 2 an electrode, and 3 an element body whose main component is silicon carbide or zinc oxide. Next, the method for producing a voltage nonlinear low antibody according to the present invention will be explained in detail with reference to Examples. Example 1 A composition consisting of 90 mol% antimony oxide and 10 mol% silicon oxide was applied to the side surface of a molded body obtained by a conventional ceramic manufacturing method using an isoamyl acetate solution containing 2% nitrocellulose as a suitable organic binder. The paste was made into a paste and applied at a concentration of 40 to 50 mg/cm ² , then embedded in a substance containing zinc oxide as a main component, and fired at a normal firing temperature of 1200°C for 5 hours. At this time, it is preferable for the work to pre-calcine the substance whose main component is zinc oxide and allow the grains to grow appropriately to form coarse grains of 28 meshes or more. The fired material was then polished and electroded, and its impulse discharge resistance was examined. The results are shown in Table 2. 〇 in Table 2 means that no external flash flash occurred, ×
indicates external flash or destruction. Examples 2 to 4 Examples except that instead of the composition consisting of 90 mol% antimony oxide and 10 mol% silicon oxide, a binary composition containing antimony oxide and silicon oxide in the proportions shown in Table 1 was used. The experiment was conducted under the same conditions as in Example 1. The results are shown in Table 2. Example 5 and Comparative Examples 1 to 5 Examples were carried out except that antimony oxide, silicon oxide, and bismuth oxide were used in the proportions shown in Table 1 instead of the composition consisting of 90 mol% antimony oxide and 10 mol% silicon oxide. The experiment was conducted under the same conditions as in Example 1. The results are shown in Table 2. In Comparative Examples 3 to 5, it was not easy to uniformly mix antimony oxide, silicon oxide, and bismuth oxide to form a homogeneous coating film. Comparative Example 6 An experiment was conducted under the same conditions as in Example 1, except that the material was fired in the air without being buried in a substance containing zinc oxide as a main component. The results are shown in Table 2. Comparative Example 7 A binary composition consisting of antimony oxide and zinc oxide was used instead of a composition consisting of 90 mol% antimony oxide and 10 mol% silicon oxide, and the composition was not buried in a substance whose main component was zinc oxide. The experiment was conducted under the same conditions as in Example 1 except that the firing was performed in the atmosphere. The results are shown in Table 2.

[Table] The composition range and composition point of each Example and Comparative Example are shown in FIG. That is, FIG. 2 is a triangular graph showing the effective composition range of the composition forming the high-resistance layer in the present invention. represents the range of compositions used as high-resistance layer forming materials.

【table】

[Table] As shown in Table 1, Table 2, and Figure 2, there are two parts of the effective blending composition for impulse discharge capacity, shown by Area A and Area B in Figure 2. . Furthermore, Table 1 and 2
From the table, it can be seen that bismuth oxide acts more effectively as a flux, and that better results are obtained when a binary composition consisting of antimony oxide and silicon oxide is buried in a substance whose main component is zinc oxide and fired. I understand. Comparing the characteristics of the low antibody obtained in the Examples with the characteristics of the low antibody obtained in the Comparative Examples, it is found that, for example, in the area A of the formulation composition of the present invention, which contains a large amount of antimony oxide.
In this case, zinc oxide is not only supplied from inside the element body, but also effectively diffused and supplied from the buried outer peripheral surface, so that Zn ₇ Sb ₂ O ₁₂ with sufficient thickness is generated, so that the desired thickness can be achieved. It is thought that the characteristics can be obtained.
When observed under a microscope, the thickness is approximately 100 μm.
This is also supported by the fact that a layer of Zn ₇ Sb ₂ O ₁₂ of about 1.0 m thick is formed. However, in the case of a material that is not buried in a substance whose main component is zinc oxide and is fired in the air as it is (in the case of Comparative Example 6), the thickness of the above layer is 50 mm.
It is less than μm. This is thought to be due to the antimony oxide dissipating into the surroundings due to evaporation, metamorphosis, etc., and naturally the impulse discharge capacity in this case is small. Furthermore, when a binary composition of antimony oxide and zinc oxide is prepared in advance and then applied (as in Comparative Example 7), the effective thickness of the high-resistance layer must be increased unless the amount of application is significantly increased. It is thought that this is why the impulse discharge withstand capacity was as small as 60kA. As described above, according to the manufacturing method of the present invention, it is possible to reduce the types of components in the composition for forming the high-resistance layer on the side surface of the element, and to reduce the number of components in the composition, and to reduce the number of components in the composition by embedding it in a material containing zinc oxide as the main component. By firing,
A high resistance layer with sufficient thickness can be obtained,
Moreover, the method of the present invention is an inexpensive processing method with improved impulse discharge capability, and can produce a voltage nonlinear low voltage antibody that makes an important contribution to improving the performance of lightning arresters.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a non-linear element for a lightning arrester, and FIG. 2 is a triangular graph showing the effective composition range of the composition forming the high resistance layer in the present invention. (Symbols in the figure), 1: High resistance layer, 2: Electrode, 3:
Element body.

Claims (1)

[Scope of Claims] 1. A molded body coated with a composition consisting of bismuth oxide 0 to 10 mol%, antimony oxide 55 to 90 mol%, and silicon oxide 0 to 45 mol% as a high-resistance layer forming substance provided on the side surface of the element, A method for manufacturing a voltage nonlinear resistor, which comprises firing the voltage nonlinear resistor while immersed in a substance containing zinc oxide as a main component.