JPS6233684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a heat-resistant insulating material. More specifically, the present invention is capable of supporting a product without damaging and/or staining the product during a heat treatment process for glass products, etc., which is carried out continuously or repeatedly in an atmosphere at a temperature of 500°C or higher, and that the product itself is As a heat-resistant support with excellent wear resistance,
The present invention also relates to a method for manufacturing a heat-resistant insulating material used as an insulator having the necessary electrical insulation properties when used in products to which high voltage is applied, such as cathode ray tubes. As conventional heat-resistant insulating materials, asbestos tapes, asbestos cement boards, asbestos calcium silicate boards, boron titanide materials, and various porcelain products have been used. Asbestos tapes are used to maintain their strength by wrapping them around metal, but when asbestos is used at temperatures above 400°C, it gradually begins to lose crystallization water, which contains 12 to 14% by weight.
If the temperature is higher than ℃, it will turn light brown and become brittle, so long-term stable use cannot be expected. Asbestos cement board is made by bonding asbestos with a cement material such as Portland cement, but it does not have sufficient electrical insulation, and since it is a relatively hard material, there is a risk of damaging glass products, etc. For the same reasons as asbestos tapes, long-term stable use cannot be expected. Asbestos calcium silicate board is a porous, lightweight, and soft material, so there is little risk of damage to the product, but it is easily worn out and requires complicated replacement work. Asbestos is a hazardous substance designated as a specified chemical substance, so the above-mentioned asbestos-based materials also pose hygiene problems. Boron titanide material itself has excellent wear resistance and can be used stably for a long time compared to asbestos, but it is very expensive and is used only in special cases. Porcelain products are materials with excellent heat resistance and electrical insulation properties, but they are hard and brittle.
It has the drawback of easily damaging glass products and the like, and being easily damaged by vibrations during transportation. A composite material that can eliminate the drawbacks of the conventional heat-resistant insulating materials mentioned above was published in 1974.
It is disclosed in Publication No. 7359 and Japanese Patent Publication No. 54-7360. The composite material is formed by molding inorganic fibers, inorganic powder, inorganic layered materials, etc. using a binder mainly composed of boric acid and zinc oxide at a temperature of 160 to 200°C and a pressure of 100 to 300 kg/ ^cm2 . It is manufactured by further heat-treating the obtained molded body at 200 to 250°C. To explain the manufacturing method of this composite material in more detail, first, during heating and pressure molding, boric acid melts and binds inorganic fibers, etc. At the same time, it is used as a binder.
It chemically reacts with zinc oxide, which is the main component, to form hydrated zinc borate, and then heat treatment at 200 to 250°C promotes the formation of hydrated zinc borate, creating an insulation with excellent water resistance and heat resistance. You can heal your body. Further, the type and amount of the inorganic fiber, inorganic powder, inorganic layered material, etc. to be used are appropriately selected depending on the purpose of use of the composite material to be obtained. However, the composite material obtained by this method is
When exposed to an atmosphere with a temperature of 500℃ or higher, crystallization water is released from the hydrated zinc borate in the material, staining glass products, and in the worst case, the insulator may break due to a sudden temperature rise. There are still many issues that need to be resolved, such as the dangers that arise. As a result of intensive research to solve the problems of such composite materials, the present inventors further heat-treated the composite materials at approximately 350 to 450°C to replace the hydrated zinc borate in the composite materials with anhydrous boric acid. It was discovered that by converting zinc into zinc, it can be made into a heat-resistant insulating material with almost no change in shape even in an atmosphere with a temperature of 500°C or higher, excellent electrical insulation properties, and good machinability.
We have now completed the present invention. That is, the present invention comprises: (a) mixing a binder made of boric acid and zinc oxide with an inorganic layered material; (b) heating the resulting mixture at a temperature of 130 to 200°C;
(c) heat-treating ^the resulting molded product by a method of gradually sublimating it from room temperature to about 250°C to form a product made of boric acid and zinc oxide; A method for producing a heat-resistant insulating material, comprising the steps of using hydrated zinc borate as a binder, and (d) further treating at about 350 to 450°C to remove crystallization water from the hydrated zinc borate. . Examples of the inorganic layered material used in the present invention include mica powder, talc, and silicon oxide, with mica powder being particularly preferred. A heat-resistant insulating support obtained by using mica powder does not damage glass products, has excellent machinability, and has good heat resistance and electrical insulation. Among the various known mica powders, phlogopite powder with a high decomposition temperature (decomposition temperature: 800℃ or higher, composition: KMg ₃ (AlSi ₃ O ₁₀ ) (OH ₂ )), synthetic fluorine phlogopite powder (decomposition temperature: :1100℃ or higher, composition:
KMg ₃ (AlSi ₃ O ₁₀ )F ₂ ) or a mixture thereof is also preferred. As the boric acid, orthoboric acid (H ₃ BO ₃ ), boric anhydride or a mixture thereof is preferred. These boric acids are mixed with zinc oxide (ZnO) and used as a binder, but preferred binders include 3 to 7 mole parts of orthoboric acid, 1 mole part of boric anhydride, and 2.5 to 4.5 mole parts of zinc oxide. A mixture of: The inorganic layered material and the binder are used by mixing 60 to 75% by weight of the former and 40 to 25% by weight of the latter using a mixer. This mixture is filled into a mold such as a metal mold, then inserted between hot plates preheated to 160-200°C, and heated and pressure-molded at a pressure of 100-300 kg/cm ² to form the desired shape. molded products can be obtained. This molded article is further heat-treated by gradually increasing the temperature from room temperature to about 250° C. to complete the formation of hydrated zinc borate in the molded article. The operations up to this point are the aforementioned Tokuko No. 54-7359 and Tokuko No. 54-7360.
The process is carried out in exactly the same manner as or almost the same as the method disclosed in each publication of the above. By further heat-treating at approximately 350 to 450°C without cooling, crystallization water of hydrated zinc borate is released and converted to anhydrous zinc borate, making it possible to produce glass products even when used at temperatures above 500°C. It can be made into a heat-resistant insulating material without the risk of contaminating or breaking itself. In addition, when the materials of the hydrated zinc borate and anhydrous zinc borate in the above composite material were analyzed by X-ray diffraction, the hydrated zinc borate was found to be 2ZnO・3B ₂ O ₃・
The anhydrous zinc borate was mainly composed of 3H ₂ O, and the anhydrous zinc borate was mainly composed of βZnO.B ₂ O ₃ . Therefore, the changes in materials in the manufacturing method of the present invention are briefly shown as follows.

[Table] ↓
Inorganic layered material + anhydrous zinc borate (βZnO〓B ₂ O ₃ )
Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples. Example 1 Phlogopite powder (particle size 100~
200 mesh), 845 g of orthoboric acid (particle size 40 to 80 mesh), 47.8 g of boric anhydride (particle size 40 to 80 mesh), and zinc oxide (particle size 1 to 10μ)
m) 195.3g was added as a binder and mixed for 10 minutes using an Ishikawa-type crusher. 1300g of the resulting mixture was placed into a container with a height of 100mm and a width of 200mm.
The mixture was filled into a mold with a length of 200 mm, then inserted between heating plates whose temperature had been raised to 170 to 180°C, and immediately pressurized to 150 kg/cm ² . The mold is about 10
The temperature reaches 160°C after a minute, but from that point onwards it reaches 160°C.
Heat and pressure were maintained for minutes. After that, the heating was released, and after cooling to 150℃, the pressure was released and the thickness was measured.
A molded product of 14 mm, width 200 mm, and length 200 mm was obtained. Next, this molded product is heated at 80℃ to 200℃ in an electric furnace.
Heat treatment was carried out by increasing the temperature at 20°C intervals up to 350°C, and then increasing the temperature stepwise up to 450°C at 20°C intervals. Note that the heating time at each temperature was 3 hours. After the heat treatment, the desired heat-resistant insulating material was obtained by allowing it to cool to room temperature. The thus obtained heat-resistant insulating material was tested for the following items to examine its properties. (a) Bending strength Measured at a thickness of 14 mm, width of 10 mm, and fulcrum distance of 100 mm. (b) Shalpey impact strength A test piece with a thickness of 14 mm, a width of 10 mm, and a length of 90 mm was used for measurement without a notch. (c) Translaminar breakdown voltage A test was conducted on a 2 mm thick sample with a polished surface at room temperature and pressure. (d) Water absorption rate A test piece with a thickness of 14 mm, width of 50 mm, and length of 50 mm was heated at 150°C.
After drying it for 4 hours, measure its weight, then immerse it in 200 ml of pure water for 23 to 25 hours, then remove it from the pure water, wipe the surface with gauze, measure its weight, and calculate its weight increase rate. was taken as the water absorption rate. (e) Dissolution rate After measuring the water absorption rate, the test piece was dried again at 150° C. for 4 hours and its weight was measured, and the weight loss rate with respect to the weight before immersion in pure water was defined as the dissolution rate. (F) Heat deformation temperature Using a test piece with a thickness of 14 mm, width of 15 mm, and length of 200 mm, both ends of the specimen are supported by firebricks at 5 mm, and the change in surface shape due to temperature changes from 700°C to 1000°C is measured at a magnification of 20 times. The temperature at which the shape changes was investigated by observing it with microscopic photographs. (g) Volume resistivity Measured according to the method of JIS K6911. (H) Surface specific resistance Measured according to the method of JIS K6911. (li) Main components of the material The main components in the material were confirmed using an X-ray diffraction device. (N) Thermal shock resistance A test piece with a thickness of 14 mm, a width of 15 mm, and a length of 200 mm was used. After measuring its weight, it was placed in an electric furnace heated to 700°C, and the test piece was left for 60 minutes. Deformation (blister, crack, discoloration) was observed with the naked eye, and then the weight was measured to calculate the heating loss rate. (l) Arc resistance Measured at room temperature and pressure according to the step method according to JIS K6911. (2) Machinability The obtained heat-resistant insulating support was processed into a round bar, hole-bored, and cut, and judged based on the ease of processing. Next, test results for characteristics (a) to (w) are shown. (a) Bending strength: 400 to 600Kg/cm ² (b) Shalpy impact strength: 3 to 5Kg-cm/cm ² (c) Translayer breakdown voltage: 7 to 9kV/mm (d) Water absorption rate: 2 ~4% (E) Dissolution rate: 0.2% or less (F) Heat deformation temperature: 900℃ or higher (At this temperature, the shape of the phlogopite powder changed and became porcelain.) (G) Volume resistivity: 1.0×10 ¹⁴ Ω or more (chi) Surface specific resistance: 1.0×10 ¹¹ ohm or more (ri) Material main components: phlogopite and βZnO・B ₂ O ₃ (nu) Thermal shock resistance: Shape changes such as blisters, cracks, and discoloration (l) Arc resistance: 300 seconds or more (w) Machinability: Very good Example 2 Synthetic fluorine gold cloud powder (100 s) as an inorganic layered material
A heat-resistant insulating material was obtained by carrying out an experiment in the same manner as in Example 1, except that 200 mesh) was used. The obtained heat-resistant insulating material was tested on the same items as in Example 1 to examine its characteristics. As a result, almost all the items showed almost the same characteristics as Example 1. Although the heat distortion temperature was 900°C or higher, the change in shape of the synthetic fluorine phlogopite powder was smaller than that of the phlogopite powder (however, porcelain formation was the same). Comparative Example 1 The pre-heat-treated molded product obtained by the method of Example 1 was heat-treated at 200° C. for 3 hours to obtain a heat-resistant insulating material. When the thermal shock resistance of the resulting heat-resistant insulating material was examined, microscopic cracks were observed within the layer in approximately 35% of the test specimens. Moreover, the heating loss rate was 4 to 6%. As described above, the heat-resistant insulating material obtained by the present invention has excellent thermal shock resistance, electrical insulation properties, and machinability, and can be used as a support during heat treatment of glass products. Yes, it is fully practical. Furthermore, the heat-resistant insulating material obtained by the present invention is not limited to the above-mentioned purposes, but can also be suitably used as heat-resistant and non-combustible insulators for electrical equipment used at high temperatures, such as insulating support frames and spacers. I can do it. In addition, since no harmful materials such as asbestos are used, it has great hygienic effects during manufacturing and use.

Claims (1)

[Claims] 1 (a) A step of mixing a binder consisting of boric acid and zinc oxide with an inorganic layered material, (b) A step of heating the resulting mixture at a temperature of 160 to 200°C and
(c) heat-treating ^the resulting molded product by gradually raising the temperature from room temperature to about 250°C to remove boric acid and zinc oxide; and (d) further heat-treating at about 350 to 450°C to remove crystallization water of the hydrated zinc borate. Law. 2. The manufacturing method according to claim 1, wherein the boric acid is orthoboric acid, boric anhydride, or a mixture thereof. 3. The manufacturing method according to claim 1 or 2, wherein the inorganic layered material is phlogopite, synthetic fluorine phlogopite, or a mixture thereof.