JPS6116129B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has heat resistance, nonflammability, and excellent electrical insulation and arc resistance, such as arc extinguishing plates for blowout type circuit breakers, insulating partition plates for vehicle controllers, and insulating seats for vehicle resistors. The present invention relates to a method for manufacturing an inorganic insulator that can be suitably used for such purposes. By the way, a method for manufacturing an insulating material by combining inorganic fibers and inorganic powder with a binder made of boric acid and zinc oxide or calcium oxide to create an insulating base material, and then molding it under heat and pressure is described in Japanese Patent Publication No. 1973-
This is already known from Publication No. 7359, etc. According to the methods disclosed in these, 130~
It is explained that an insulating base material is filled into a mold while the temperature is being raised to 200°C, and a molded product is obtained by applying a pressure of 100 to 300 kg/cm ² . In other words, the reinforcing material is melted by thermal change of boric acid, which is the main component of the binder, and zinc oxide, which is present as a component of the binder, binds the reinforcing material.
By forming a hydrated borate with calcium oxide, etc., we aim to improve water resistance by eliminating the reversibility of boric acid to withstand water after thermal change, and by forming a hydrated borate, for example, When it becomes boric anhydride as the final form of thermal change, it melts at a temperature of about 450°C, but in this case, it forms a hydrous borate that does not melt even at higher temperatures. It is also designed to improve heat resistance. Incidentally, in order to obtain a dense molded product and one with excellent water resistance and heat resistance, the thermal change of boric acid and the presence of decomposed water generated as a result of it are very important. In other words, if the molding is done in such a way that the decomposed water is not scattered from the inside of the molded product to the outside as much as possible, the deformation caused by the thermal change of boric acid will melt in the coexistence with water, exhibiting a binding effect, and preventing oxidation. It easily reacts with zinc and calcium oxide to form a hydrated borate, but on the other hand, it is difficult to exhibit sufficient binding effect in conditions where decomposed water during molding freely scatters to the outside from the molded product. Since it is difficult to form a hydrous borate, the obtained molded product may have poor water resistance and heat resistance. However, as a result of examining conventionally known manufacturing methods based on these facts, the present inventors found that the conventional manufacturing methods had problems. In conventional manufacturing methods, an insulating base material is filled into a heated mold or the like, and a molded article is obtained by applying pressure. In this method, boric acid as a binder starts to decompose from the moment the insulating base material is filled into a mold, and the decomposed water scatters out of the mold until pressurization is applied. (Orthoboric acid starts to change thermally at 90°C.) In the worst case, boric acid, which exerts a binding effect on the insulating base material in contact with the mold wall, finishes thermally changing and becomes less effective in binding. As soon as the temperature is high, pressure is applied, and the surface layer of the molded product naturally becomes less compact, and this tendency becomes more noticeable when the temperature is high or when trying to obtain a thick molded product. When the surface layer of a molded product is porous, it has poor properties such as strength and electrical insulation in a humid atmosphere, and is likely to have dimensional defects in terms of size and shape. In addition to being porous, boric acid and zinc oxide are difficult to react with, so hydrated borates are not formed, and they are easily hydrolyzed by moisture such as moisture, and have poor heat resistance. As mentioned above, in the conventional manufacturing method, there are defects on the outer periphery of the molded product, so the surface layer is polished by about 0.5 to 1.0 mm depending on the application. Processing may be complicated and manufacturing may be difficult. This invention was made as a result of intensive research to eliminate the defects associated with conventional products, and it is possible to uniformly compact down to the surface layer of molded products, and to obtain thick products with uneven shapes without any problems. The present invention relates to a manufacturing method for obtaining a stable molded product. In this invention, an insulating base material is pressurized at a temperature of 100 to 130°C to make a rough molded product, and this rough molded product is heated to a temperature of 160 to 250°C.
The main idea is to obtain a molded product with dense compaction down to the surface layer by pressurizing it at a temperature of °C, and eliminates all the defects of the conventional products. . As for the reason for making rough molded products, especially in the case of thick or large products, the conventional method of putting the insulating base material as it is into a heated mold takes a long time to fill, so of course it takes a long time to pressurize it. This is because the boric acid in the insulating base material undergoes thermal changes by then, and the defects are likely to appear. If a rough molded product is made, it can be inserted into the mold in a short time and pressurized, so the decomposition water due to the thermal change of boric acid is difficult to scatter to the outside, so it works effectively and reaches the outer periphery of the molded product. You can easily obtain detailed objects. The reason for pressurizing at a temperature of 100 to 130°C to obtain a rough molded product is that even if it is pressed at room temperature, it is difficult to handle and easily breaks its shape. Obtain something with easy strength. The reason for having strength is 100-130
By pressurizing at a temperature of ℃, some of the boric acid in the insulating base material is thermally changed and has a binding effect, giving it the strength to maintain the shape of the rough molded product, but most of it is It remains undecomposed. At temperatures below 100°C, the strength of the crude molded product is poor and handling is difficult. When the temperature exceeds 130℃, the thermal change of boric acid becomes active, and it hardens to form a partially hydrated borate, which causes poor flow in the next molding stage, making it difficult to eliminate the defects of conventional products. It is. As long as the pressing force is 100 kg/cm ² or more, a rough molded product can be obtained that has enough strength to handle without any problems. It is preferable to store this crude molded product in a place with low moisture content, such as in an air-conditioned room or in a silica gel chamber, until the next molding. By making rough molded products, the area required for storage can also be reduced. Next, the rough molded product
It is inserted into a mold heated to 160-250℃ and pressurized to obtain the desired molded product. Pressure is applied at the temperature at which boric acid undergoes the most active thermal change to obtain a dense molded product. Therefore, the above range is appropriate. In addition, it is necessary to pressurize the rough molded product immediately after inserting it into the mold, and even if the rough molded product is obtained by the present invention and the filling time is significantly shortened, if the time to pressurize the rough molded product is long, the temperature Due to the high temperature, the thermal change of boric acid progresses, and results are likely to be similar to those of conventional products. However, once the rough molded product is inserted into the mold, it must be pressurized within at least 5 to 10 seconds. By the way, when the temperature is less than 160°C, the crude molded product is in the process of being heated from room temperature, so a long pressurizing time is required, and it is difficult to obtain a molded product with good firmness. If the temperature exceeds 250°C, the thermal change of boric acid will proceed rapidly, so unless pressurization is applied very quickly after inserting the rough molded product into a mold, the product will not be much different from conventional products, which is not desirable. The above-mentioned temperature range is preferable for obtaining molded products that are easiest to operate and have uniform compactness. As the insulating base material used in the present invention, in addition to mica powder, glass fiber, and asbestos fiber, any insulating material that has a reinforcing effect such as ceramic fiber or rock wool can be used. In addition to reinforcing materials, electrically insulating metal oxides, their hydroxides, carbonates, etc. can be used in combination depending on the required performance. As a binder mainly composed of boric acid, a mixture of orthoboric acid, a mixture of orthoboric acid and metaboric acid, or a mixture of orthoboric acid and boric anhydride combined with zinc oxide or calcium oxide, etc. is used. Can be used. It is also possible to use an insulating base material made of the above materials to which thermosetting or thermoplastic resin powder is added. Next, the present invention will be explained in more detail using Examples and Comparative Examples. Example 1 Natural phlogopite powder (particle size 60-100 mesh) 350
g, orthoboric acid (particle size 40-60 mesh), 82.2 g, anhydrous boric acid (particle size 40-60 mesh) 78.5 g, and zinc oxide (particle size 300 mesh or less) 49.3 g were placed in an Ishikawa-type crusher and mixed for 10 minutes. An insulating base material was prepared. Next, a rough forming mold with a height of 100 mm, a width of 124.5 mm, and a length of 124.5 mm is heated to 120°C between the hot plates of a press, and the insulating base material is filled into the mold, and a pressing force of 200 kg/cm ² is applied. in
Pressure was applied for 10 minutes. Next, take it out from the mold to a thickness of approx.
A crude molded product measuring 15 mm, width 124.5 mm, and length 124.5 mm was obtained. On the other hand, a mold with a height of 50 mm, a width of 125 mm, a length of 125 mm, and a projection with a depth of 3 mm and an outer diameter of 50 mm in the center was heated to 185°C between the hot platens of a press, and Place the rough molded product directly into the
Pressure was applied at a pressure of Kg/cm ² . After applying pressure for 20 minutes, the mold was cooled to 80° C. or lower, then pressurization was applied, and the molded product was taken out. A molded article having a protrusion with a height of 3 mm and an outer diameter of 50 mm at the center of the flat plate was obtained.
In the same way, a total of 3 molded products were made and heated to 80°C.
The temperature was raised stepwise at 20°C intervals up to 200°C, and each
A product of the present invention was obtained by heat treatment for a certain period of time. Example 2 The insulating base material was prepared in the same manner as in Example 1. In order to obtain a rough molded product, the temperature of the rough molding mold was set to 100℃, and the pressure was applied for 10 minutes at a pressure of 300 kg/cm ² to a thickness of approximately 15 mm and a width.
A crude molded product with a length of 124.5 mm and a length of 124.5 mm was obtained. Thereafter, in the same manner as in Example 1, three molded products each having a protrusion with a height of 3 mm and an outer diameter of 50 mm in the center of a flat plate were prepared, and then heat treated in the same manner as in Example 1 to obtain a product of the present invention. Example 3 The insulating base material was prepared in the same manner as in Example 1. In order to obtain a rough molded product, the temperature of the rough molding mold was set to 130℃, and the pressure was applied for 5 minutes at a pressure of 200 kg/cm ² to a thickness of approximately 14 mm.
A rough molded product with a width of 124.5 mm and a length of 124.5 mm was obtained. Thereafter, in the same manner as in Example 1, a height of 3 mm was placed at the center of the flat plate.
Three molded products having protrusions with an outer diameter of 50 mm were made. Thereafter, the same heat treatment as in Example 1 was performed to obtain a product of the present invention. Example 4 After obtaining a rough molded product in the same manner as in Example 1, using the same molding mold as in Example 1, the mold temperature was set to 250°C, the rough molded product was put in, and the molding was carried out at a pressure of 300 kg/cm ² for 20 minutes. Then, in the same manner as in Example 1, three molded products having a protrusion with a height of 3 mm and an outer diameter of 50 mm in the center of a flat plate were prepared.
I created one. Thereafter, the same heat treatment as in Example 1 was performed to obtain a product of the present invention. Example 5 After obtaining a rough molded product in the same manner as in Example 1, using the same molding mold as in Example 1, the mold temperature was set to 160°C, the rough molded product was put in, and the molded product was heated at a pressure of 300 kg/cm ² for 20 minutes. After that, in the same manner as in Example 1, three molded products each having a protrusion with a height of 3 mm and an outer diameter of 50 mm in the center of a flat plate were created. Thereafter, the same heat treatment as in Example 1 was performed to obtain a product of the present invention. Example 6 Three pieces of products of the present invention were prepared in the same manner as in Example 1, except that asbestos fiber (Class 5 product manufactured by Johns Manville) was used instead of the natural phlogopite powder in Example 1. Example 7 Three products of the present invention were prepared in the same manner as in Example 1, except that glass fiber (manufactured by Asahi Fiber KK, fiber length: 3 mm) was used instead of the natural phlogopite powder in Example 1. Example 8 Natural phlogopite powder (particle size 60-100 mesh) 304.3
g, orthoboric acid (particle size: 40 to 60 mesh), 71.5 g, anhydrous boric acid (particle size: 40 to 60 mesh), 16.1 g, and zinc oxide (particle size: 300 mesh or less), 42.8 g were mixed for 10 minutes using an Ishikawa crusher. Next, add polyphenylene sulfide resin powder (particle size of 200 mesh or less).
65.0g was added and mixed for an additional 5 minutes to prepare an insulating base material. Next, using the rough forming mold used in Example 1, the mold was heated to 125°C between press heating plates, the insulating base material was filled into the mold, and the mold was pressurized at a pressure of 300 kg/cm ² for 10 minutes. . Next, take it out from the mold, about 15mm thick and wide.
A crude molded product with a length of 124.5 mm and a length of 124.5 mm was obtained. On the other hand, as a mold, the height is 50 mm, the width is 125 mm, and the length is
A mold with a diameter of 125 mm and a protrusion of 3 mm in depth and 50 mm in outer diameter at the center was heated to 200°C between hot platens of a press, the rough molded product was placed therein, and the mold was heated to 300 kg/cm.
After pressurizing at a pressure of cm ² for 20 minutes, the mold was cooled to 80° C. or below, pressurized, and the molded product was taken out.
A molded article having a protrusion with a height of 3 mm and an outer diameter of 50 mm at the center of the flat plate was obtained. A total of three molded products were prepared in the same manner, and the temperature was raised from 80° C. to 350° C. at a rate of 5° C./min, held for 5 hours, and then taken out from the electric furnace to obtain a product of the present invention. Comparative Example 1 After creating an insulating base material with the same composition as Example 1,
Without creating a rough molded product, the insulating base material was filled into a mold whose temperature had been raised to 185°C, and after directly pressurizing it at a pressure of 300 kg/cm ² for 20 minutes, the mold was heated to 80°C. After cooling to the following temperature, pressure was applied and the molded product was taken out. A molded article having a protrusion with a height of 3 mm and an outer diameter of 50 mm at the center of the flat plate was obtained. A total of three molded products were created in the same manner, and the same heat treatment as in Example 1 was performed to create a comparative product. Comparative Example 2 After creating an insulating base material with the same composition as Example 1,
The rough molding mold used in Example 1 was brought to room temperature, the insulating base material was filled into the mold, and a pressing force of 100 kg/cm ² was applied.
Pressure was applied for 10 minutes. The removal from the mold was done with particular care. Since it was difficult to maintain the shape of the rough molded product, it was handled by placing it on a stainless steel plate with a thickness of 1.5 mm. I did not measure the shape of the rough molded product because it would collapse if touched, but the width,
It had also grown in length. Thereafter, three comparative products were prepared in the same manner as in Example 1. Comparative Example 3 After creating an insulating base material with the same composition as Example 1,
The rough molding mold used in Example 1 was heated to 80°C, and the insulating base material was filled into the mold, and the mold was heated at a pressure of 100 kg/cm ² .
Pressure was applied for 10 minutes. The crude molded product was handled in the same manner as in Comparative Example 2. Thereafter, three comparative products were prepared in the same manner as in Example 1. Comparative Example 4 After creating an insulating base material with the same composition as Example 1,
The rough molding mold used in Example 1 was heated to 150°C, and the insulating base material was filled into the mold, and the pressing force was 100Kg/cm ²
Pressure was applied for 10 minutes. Rough molded product thickness 12mm, width
It had a shape of 124.5 mm and a length of 124.5 mm. Thereafter, three comparative products were prepared in the same manner as in Example 1. Table 1 shows the properties measured for those obtained in Examples and Comparative Examples.

【table】

[Table] The appearance of the crude molded product was judged by touching whether it was easy to handle or not. Those that did not change shape when touched with the hand were considered good. The appearance of the molded product was observed, especially the state of the protrusions. For characteristic tests, a protrusion with a thickness of 3 mm and an outer diameter of 50 mm was cut out, and the water absorption rate, change in appearance after immersion in water, bending strength, and insulation resistance were determined. The water absorption rate was measured by drying the sample with a thickness of 3 mm and outer diameter of 50 mm at 150° C. for 4 hours, and then measuring the weight. Next, after immersing it in pure water for 24 hours, the surface was wiped off with a cloth and the weight was measured. The increase in weight was defined as the amount of water absorbed, and was expressed as a ratio to the original weight, which was defined as the water absorption rate. At the same time, changes in the appearance of the samples were observed with the naked eye. The bending strength was measured at the position where the longest part could be taken from a shape with a thickness of 3 mm and an outer diameter of 50 mm, and with a width of 25 mm at the original thickness and a distance of 30 mm between supporting points. The insulation resistance is as follows from a shape with a thickness of 3 mm and an outer diameter of 50 mm, with an original thickness of 20 mm in width and 40 mm in length.
Measured with a 1000V portable megger according to JISK6911. Measurement conditions are 40℃ and 95% relative humidity.
Measurements were made on samples left in RH for 24 hours. According to the results shown in Table 1, according to the manufacturing method of the present invention, it is possible to obtain a product having a low water absorption rate and excellent water resistance and insulation resistance in a humid atmosphere. When the insulating base material is molded without making a rough molded product (Comparative Example 1) As it takes a long time to fill the mold, the boric acid in the insulating base material leaks from the part in contact with the mold, similar to the conventional product. A thermal change occurs, and the decomposed moisture freely scatters outside until it is pressurized, and even if it is pressurized in the next step, it has poor binding effect and does not react with zinc oxide or calcium oxide. Therefore, it is clear that only products with poor water resistance can be obtained. If the insulating base material is roughly molded in some way (Comparative Examples 2 and 3), it can be pressurized immediately after being inserted into the mold, so it is possible to obtain a molded product with relatively good properties. . However, when the size and shape of the molded product becomes thick or large, it becomes very difficult to handle the rough molded product, and when inserting it into the mold, the shape of the rough molded product collapses and uneven filling occurs. It is easy to cause At least, it is necessary that the rough molded product be easy to handle. This invention allows rough molded products to be easily handled,
It is possible to produce molded products with stable characteristics without any problems. That is, by pressurizing at a temperature of 100 to 130°C, the boric acid in the insulating base material is thermally changed by a small amount, and its binding effect is utilized, so that it does not interfere with the subsequent production of molded products. However, at temperatures exceeding 130°C, the thermal change of boric acid is active (Comparative Example 4), which causes problems such as non-flowing during the creation of molded products. As described above, according to the manufacturing method of the present invention, rough molded products can be stored in a place with low humidity and do not take up much space.Furthermore, for flat plate-shaped products, a spacer such as a steel plate is installed between the rough molded products. It is also effective in increasing manufacturing efficiency, such as by making it possible to obtain a plurality of molded products in one molding process.

Claims (1)

[Claims] 1. An inorganic insulator obtained by heating and press-molding an insulating base material containing at least one reinforcing material selected from mica powder, glass fiber, and asbestos fiber and a binder whose main component is boric acid. In the manufacturing method, the above-mentioned insulating base material is pressurized at a temperature of 100 to 130 °C to obtain a rough molded product in advance, and then this rough molded product is pressurized again at a temperature of 160 to 250 °C to obtain a molded product. A method for producing characteristic inorganic insulators.