JPS61198502A - Making of inorganic insulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a method for producing an inorganic insulator that has excellent heat resistance, non-combustibility, and electrical insulation properties, and can be relatively easily manufactured into complex-shaped insulators. . More specifically, the present invention relates to a method for producing an inorganic insulator that can be used in electrical insulating parts that require heat resistance, nonflammability, and electrical insulation properties, such as insulators, insulating parts for resistors, and arc-extinguishing parts.

[Prior Art 1] Ceramic materials have been known as insulating materials with excellent heat resistance and nonflammability. The method for producing inorganic insulators made of ceramic materials is to use organic binders such as polyvinyl alcohol, glycerin, and nitrocellulose as a binder for ceramic raw materials, mold them into desired shapes by various methods, and then heat them to form organic binders. A common method is to decompose and remove banhgu, then heat and combust it at a high temperature.

[Problem to be solved by the invention 1 When organic banegu is used as in the conventional method, carbon content remains unless the organic banegu is completely decomposed and removed.
The reality is that heating conditions such as temperature, heating rate, atmosphere, etc. must be set very carefully because insulation properties may deteriorate. Furthermore, high temperatures are required during sintering.

The present invention has excellent electrical insulation properties and strength for use in electrical insulation parts with excellent heat resistance and nonflammability, such as insulators, insulation parts for resistors, arc extinguishing parts, etc. This was done for the purpose of manufacturing an inorganic insulator that can be easily obtained.

[Means for Solving the Problems 1] The present invention involves adding 1 to 5 parts of zinc oxide or calcium hydroxide to 100 parts (parts by weight, the same applies hereinafter) of ceramic raw materials, and adding a boric acid aqueous solution to form a slurry. By hardening the slurry by casting or compression molding, and heating and firing the resulting hardened product in a conventional manner, we manufacture inorganic insulators with excellent heat resistance, nonflammability, and electrical insulation properties. It's about how to do it.

[Example 1] The ceramic raw material used in the present invention itself has heat resistance,
An inorganic filler, preferably in powder form, made of a metal oxide or a composite system thereof, such as alumina, silica, magnesia, zircon, cordierite, alumina/titania, and willemite, which has excellent electrical insulation properties and is relatively inexpensive; It is made of glass powder such as lead-based low melting point glass or borosilicate-based alkali-free glass with a fusion temperature (temperature at which the viscosity becomes lower than 106 cP) of 380 to 1250'C, The ratio of inorganic filler and glass powder is 20/80 to 65/:
A preferred specific example is one having a composition of 'j5.

If the inorganic filler/glass powder content is less than 20,780, the properties of the glass powder will appear too strongly, and the strength will particularly tend to be insufficient. On the other hand, if the ratio exceeds 65,735, it is not preferable because it tends to become porous and tends to lack electrical insulation and strength.

Generally available commercially available inorganic fillers and glass powders, which are ceramic raw materials, may be used.
If the particle size is smaller than 149μ, it can be used without any problem. The smaller the particle size, the lower the sintering temperature and the higher the density, but it may also be more expensive or require less properties, so it may be selected depending on the application.

In the present invention, 1 to 5 parts of zinc oxide or calcium hydroxide are added to 100 parts of a ceramic raw material consisting of an inorganic filler and a glass powder to prepare a =4- mixture.

Zinc oxide or calcium hydroxide is added because they form a hydrated borate in the presence of boric acid and water, and because they react and harden when heated. By using these, it becomes easy to add a boric acid aqueous solution to the mixture and form it into a slurry into a desired shape.

For example, when zinc oxide and boric acid aqueous solution come into contact, 27n
o・3B203・311□0.2znO・3B203・
It is said to form and cure hydrated zinc borate salts such as 71120. Also, when calcium hydroxide and boric acid aqueous solution come into contact, 2CaQ, 77 [1203" 81120
, Ca0 ・3B203 ” 41120, CaO ・3
It is said to form and harden hydrated calcium borate salts such as B203.5 II 20.

If the amount of zinc oxide or calcium hydroxide added is less than 1 part, the cured product tends to be easily broken unless handled with care, which is undesirable. Furthermore, if the amount added exceeds 5 parts, the properties of the glass powder may change during the heating and sintering process, raising or lowering the sintering temperature, which tends to complicate the sintering process. It is not desirable because it is located in

In the present invention, a boric acid aqueous solution is added to the mixture to form a slurry. Preparing a slurry using an aqueous boric acid solution is as follows: (1) The slurry made with an aqueous boric acid solution is dried and the hardened product is changed. If the heating process to decompose and remove them is not strictly controlled, carbon will remain and deteriorate the properties, but in the case of hydrated borates, they combine with ceramic raw materials during the heating process and form a strong matrix. Uru (, 1) This is because the process of obtaining a cured product is simple and the raw materials are inexpensive.

A common method for preparing an aqueous boric acid solution is to add water to a hydrate of orthoboric acid, anhydrous boric acid, or metaboric acid to dissolve it.

Since the solubility of boric acid varies depending on the temperature, the concentration of the boric acid aqueous solution can be changed by adjusting the temperature of the water that is the solvent. In this case, 3 to 15% (weight %, hereinafter the same) is preferable. When the concentration is less than 3%, the bonding strength upon curing becomes weak, while when it exceeds 15%, a supersaturated state is likely to occur due to temperature changes, and solids are likely to precipitate.

By the way, when adding a boric acid aqueous solution and a mixture containing ceramic raw materials, if the temperature of the mixture containing ceramic raw materials is low due to the solder, boric acid will precipitate and it will not be possible to mix uniformly (( Therefore, it is desirable that the temperature of the mixture containing the ceramic raw material be much higher than the temperature of the boric acid aqueous solution.

Next, a method for preparing the slurry will be explained.

The slurry can be changed by stirring the mixture while adding the boric acid aqueous solution while heating the mixture to a temperature equal to or higher than that of the boric acid aqueous solution, but the amount added depends on compression molding and casting molding. It's different depending on the person.

In the case of compression molding, 5 to 100 parts of the mixture
It is preferable to add 15 parts. If the amount added is less than 5 parts, it is difficult to form a uniform molded product, and the strength of the cured product tends to vary widely; if it exceeds 15 parts, for example, 5 to 10
When compression molding is performed by applying pressure for a minute, slurry tends to flow out of the mold during pressurization, making it difficult to form a uniform molded product. The pressure during compression molding is 30 kg7.
If the pressure is less than cm2, it is difficult to obtain a uniform molded product, and even if the pressure exceeds 300ky/c shoulder2, the effect of pressurization will not appear. Further, if the pressing time is less than 5 minutes, it is difficult to obtain a uniform molded product, and if the pressing time is applied for more than 10 minutes, the effect will not be obtained.

Next, regarding the case of casting, the mixture 10
It is preferable to add 25 to 35 parts of boric acid aqueous solution to 0 parts. When the weight is less than 25 parts, the fluidity of the slurry decreases, making it difficult to cast into molds with complex shapes.When the weight exceeds 35 parts, the fluidity of the slurry becomes good, making casting difficult. Although it is easier, the boric acid aqueous solution becomes excessive, and the excess liquid accumulates in the upper layer of the mold, which requires an operation to remove it, which tends to complicate the work.

After compression molding or cast molding, the product is left in the mold and left undisturbed, but it can be converted into a hardened product by heating at a temperature of up to 200'C. This is thought to be because the added zinc oxide or calcium hydroxide and boric acid first react in the presence of water to form a hydrated borate as described above, and then the reaction progresses by heating and hardens. Details are unknown.

Note that although a boric acid aqueous solution alone exhibits a hardening phenomenon of the ceramic raw material, a hardened product containing zinc oxide or calcium hydroxide has even better strength and is easier to handle.

Next, the cured body is heated and sintered to convert it into an inorganic insulator, but this is done by heating it to a temperature at which the glass powder constituting the ceramic raw material fuses.

When the glass powder constituting the ceramic raw material is a lead-based low melting point glass, it can be heated and sintered at a low temperature around 380°C. On the other hand, in the case of borosilicate-based high melting point glass, it is necessary to heat and sinter it at a relatively high temperature around 1250'C. These heating and sintering conditions are determined by the fusion temperature of the selected glass powder. Therefore, high melting point glass may be used for applications that require high heat resistance, and low melting point glass may be used for applications that do not require high heat resistance.

Many glass powders such as those described above are commercially available, and many with various fusion temperatures are commercially available, so that they can be used without particular limitations as long as they have excellent electrical insulation properties. However, since a low melting point glass with a fusing temperature of 380° C. is not yet commercially available, a glass made by the present inventors is used.

The reason why ceramic raw materials such as an inorganic filler and glass powder are used is that the sintered body can be changed at a relatively low temperature, so that the manufacturing cost is low.

Next, the manufacturing method of the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples.

Example l Pb0 75.48%, 8IF 311.36%, B
20. , 7.06%, 5i026.10% l'I ratio of raw materials were mixed at a temperature of 900 to 1000°C for 60 to 60 minutes.
The melted material was heated and melted for 90 minutes and poured onto a stainless steel plate-L, and the resulting block was ground to an average particle size of 44 μm using a ball mill.

Average coefficient of thermal expansion of the obtained lead-based glass (40-250℃)
is 12. At OX 10-6/'C, the transition point is 300℃,
The fusion temperature was 380°C.

50 parts of alumina powder (^1203, average particle size 10 μl), 50 parts of the above lead-based glass, and 5 parts of zinc oxide (ZnO1 average particle size 1 μl) were mixed in a ball mill for 3 hours.

Next, prepare an aqueous solution with a boric acid concentration of 10%, add 10 parts to 200 parts of the mixture, mix for 10 minutes with a crusher,
I got slurry.

The resulting slurry is 30Mx high, 1251RIN inside,
Using a mold with a length of 1251'lI, an applied pressure of 200k
l? /cm2 for 5 minutes, the mold was gradually heated from room temperature to 200°C, heated at that temperature for 3 hours, slowly cooled, and demolded to obtain a cured product with a thickness of 5 to 6 txx. . Next, this cured product is placed in an electric furnace and heated from room temperature to 380°C.
The mixture was heated at a temperature rate of 3° C./min until the temperature reached 3° C., held for 3 hours, and then slowly cooled to a temperature of 100° C. or less to obtain an inorganic insulator.

The obtained inorganic insulator was extremely dense and shiny, and emitted a metallic sound. Using the insulator, electrical insulation resistance and bending strength were measured by the following methods.

The results are shown in Table 1.

(Electrical insulation resistance) The width of the inorganic insulator is 20 degrees, up to the original thickness. 4
0zj! 1. :Cut and test in normal condition and at 25°C at 90% R1 using a 500mm Porta Pull Megger manufactured by Yokogawa Electric Corporation in accordance with JTS K 6911 (Thermosetting Plastic X+Tsuku General Test Method) Section 5.12. The evaluation was made after being left for Dangetsu OO time.

(Bending strength) The inorganic insulator was cut into medium 2 (1 +

121 Example 2 50 parts of magnesia powder (HgO1 average particle size 74 μm),
50 parts of the same lead-based glass used in Example 1 and calcium hydroxide (Ca(Oll)2, average particle size 10μ)
1 part was mixed.

Next, an aqueous solution having a boric acid concentration of 10% was prepared, and 30 parts was added to 200 parts of the mixture, and an inorganic insulator was prepared and evaluated in the same manner as in Example 1.

The results are shown in Table 1.

Example 3 An inorganic insulator was prepared and evaluated in the same manner as in Example 1, except that zircon powder (ZrO□.SiO2, average particle size 30 μJl) was used instead of the alumina powder used in Example 1. The results are shown in Table 1.

Example 4 Cordierite powder (2Mg0.2^1203.5SiO□, average particle size 74) was used instead of the alumina powder in Example 1.
A heat-resistant electrical insulator was prepared and evaluated in the same manner as in Example 1, except that the heat-resistant electrical insulator was used. The results are shown in Table 1.

Example 5 30 parts of alumina powder (A1203, average particle size 30 μm), zircon powder (Zr02.5i02, average particle size 74 μm)
M) 35 parts, No. 1 + 21Mff lath (manufactured by Japan 7 Erow Co., Ltd., fusion temperature 680°C, average particle size 74 μR) 3
5 parts and 3 parts of zinc oxide (ZnO1 average particle size 1 μm) were combined in a ball mill for 3 hours. A slurry was prepared by adding 60 parts of an aqueous solution with a boric acid concentration of 3% to 200 parts of the resulting mixture, and the slurry was heated to a height of 30i+x, Ill 12
It was cast into a plastic container with a size of 5.5 oz and a length of 125 +++ a+, and left to stand for 3 days under normal conditions to obtain a cured product.

The cured product could be easily removed from the container.

゛Then, the cured product is placed in an electric furnace and heated from room temperature to 680℃.
The sample was heated at a temperature increase rate of 3° C./min to 100° C., maintained at this temperature for 3 hours, and then slowly cooled to a temperature of 100° C. or lower to produce an inorganic insulator. The electrical insulation resistance and bending strength of the obtained insulator were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 6 20 parts of alumina powder (A1203, average particle size 74 μz), 10 parts of alumina titania powder (A120.・TiO□, average particle size 40 μz), willemite powder (Zn2
sio, average particle size 40 μm) 20 parts, FA-809 (
50 parts of glass powder with a fusion temperature of 950'C and an average particle size of 74 μm (manufactured by Nippon 7 Erow Co., Ltd.) and 3 parts of calcium hydroxide (Ca(011)2, average particle size of 10 μm) were mixed and milled in a ball mill. We met for 3 hours.

Add 5% of an aqueous solution of boric acid at a concentration of 15% to 200 parts of the resulting mixture.
After adding 0 parts to prepare a slurry, it was cast into a plastic container in the same manner as in Example 5, and was left at 70° C. for 24 hours to be demolded to produce a cured product.

The resulting cured product was placed in an electric furnace and heated from room temperature to 950°C at a temperature increase rate of 3°C/ll1in, held for 3 hours, and slowly cooled to below 100°C to produce an inorganic insulator and evaluated. did. The results are shown in Table 1.

Example 7 20 parts of silica powder (melting 5in2, average particle size 74μ5), No. 7540 (manufactured by Iwaki Glass Co., Ltd., fusion temperature 125)
At 0° C., 80 parts of yellow glass powder with an average particle size of 74 μm) and 3 parts of zinc oxide were mixed together in a ball mill for 3 hours.

70 parts of an aqueous solution with a boric acid concentration of 8% was added to 200 parts of the resulting mixture.
A slurry was prepared.

The obtained slurry was strained in the same manner as in Example 6 to obtain a cured product, and then the obtained cured product was placed in an electric furnace and heated from room temperature to 1250°C at a temperature increase rate of 5°C/min. After holding at temperature for 3 hours, slowly cooling to below 100℃,
Inorganic insulators were fabricated and evaluated.

The results are shown in Table 1.

Comparative Example 1 A slurry was prepared in the same manner as in Example 7 except that zinc oxide was not used and water was used instead of the boric acid aqueous solution, and an attempt was made to obtain a cured product, but when removing the mold from the plastic container, Damaged.

Comparative Example 2 An inorganic insulator was produced and evaluated in the same manner as in Example 6 except that calcium hydroxide was not used. Conclusion 161 [Effect of the Invention 1 The filtration insulator of the present invention has extraordinary bending strength and excellent electrical insulation properties, and is of course nonflammable, making it suitable for use in insulators, arc-extinguishing parts, and resistors. It can be suitably used for applications such as insulating parts for frames.

In addition, the inorganic insulator of the present invention does not use an organic binder during manufacturing, so there is no need to worry about residual carbon, and it can be easily manufactured by sintering at low temperatures, resulting in a low cost F. The effect is inhuman.

Claims (6)

[Claims] (1) Add 1 to 5 parts by weight of zinc oxide or calcium hydroxide to 100 parts by weight of the ceramic raw material, make a slurry using an aqueous boric acid solution, cast or compression mold, and then sinter the resulting hardened body. A method for producing an inorganic insulator characterized by: (2) The ceramic raw material is an inorganic filler made of a metal oxide or its composite system and a fusion temperature of 380 to 125
The manufacturing method according to claim 1, wherein the manufacturing method is made of glass powder at 0°C, and the weight ratio of the inorganic filler and the glass powder is 20/80 to 65/35. (3) The metal oxide is alumina, silica, magnesia, zircon, cordierite, alumina titania, or willemite, and the glass powder with a fusion temperature of 380 to 1250°C is a lead-based low-melting glass powder or a borosilicate-based alkali-free glass powder. The manufacturing method according to claim (2), which is a glass powder. (4) The method according to claim (1), wherein the boric acid aqueous solution is an aqueous solution having a boric acid concentration of 3 to 15% by weight. (5) Add 5 to 5 parts of a boric acid aqueous solution to 100 parts by weight of a mixture of ceramic raw materials and zinc oxide or calcium hydroxide.
The manufacturing method according to claim (1), wherein 35 parts by weight is added to form a slurry. (6) The manufacturing method according to claim (1), in which the slurry is molded, cured at room temperature to 200°C, and then demolded to obtain a cured product.