JPH0582002B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing an insulating heat-resistant material that maintains high static mechanical strength and excellent thermal and mechanical impact strength at high temperatures of 500 to 600°C. [Prior Art] Insulating heat-resistant materials that are used at temperatures of 300° C. or higher, have little aging, and maintain insulation and mechanical strength are generally limited to inorganic materials. When considering only static mechanical strength and insulation properties, porcelain materials have extremely favorable properties. However, in applications such as spacers that hold high-frequency coils, where temperatures rise and fall rapidly and are subject to large thermal shocks, or when assembling metal parts that become hot during use while maintaining precise spacing, dimensions, and insulation properties. Porcelain materials inherently have poor thermal and mechanical impact strength, so they cannot be used for applications that require high mechanical impact strength, such as wedge-shaped plates. There is a fatal flaw. In this regard, since glass-mica plastic bodies are inherently high in thermal and mechanical impact strength,
It is suitably used for the above purposes. A glass-mica plastic body is made from a mixed powder of glassy powder and mica powder crushed into flakes.This mixed powder is made into a material that can be made to flow by melting and softening the glassy powder and applying pressure. It is a composite material with high insulation properties that is obtained by heating it to a certain temperature and press-molding it in the heated state. The reason why this glass-mica plastic body maintains extremely excellent properties in terms of thermal and mechanical impact strength is due to the properties of the mica powder, which is the main raw material. In other words, mica powder is flaky as mentioned above, and the ratio of the surface area of the powder to the diameter and thickness is on average
The ratio is 30 to 50:1. This is because mica flakes are arranged in a layered manner in the molded product, so they are in a state completely different from that of porcelain and have elasticity. The thermal and mechanical impact strength essentially retained by the glass-mica plastic body is largely controlled by the particle size and content of the mica powder and the molding conditions, particularly the heating temperature during molding. First, we will use mica powder.There are two types of mica powder: natural and synthetic.Natural mica powder contains hydroxyl groups (OH) in its crystal structure, so when heated to high temperatures, hydroxyl groups (OH) are removed. OH) decomposes to generate H ₂ O, destroying the crystal structure. The temperature at which this decomposition occurs varies depending on the constituent components of mica, but this tendency is common to all types of natural mica. Note that when heated in the presence of glassy powder, a reaction occurs with the glassy powder, so the decomposition temperature becomes lower than when heated alone. On the other hand, synthetic products do not have hydroxyl groups (OH) in their crystal structure, so they will not split when heated alone, but if they are heated together with glassy powder, they will react with the glassy powder. It becomes eroded by As mentioned above, natural mica has a splitting phenomenon, so there are restrictions on the heating temperature, and it is difficult to use glassy powder with a high melting temperature, so the usable glassy powder is naturally limited. . Synthetic mica does not have the above restrictions, but the higher the temperature, the more likely it is to be eroded, so a lower heating temperature is preferable. Now, regarding the relationship between decomposition or erosion of mica, static mechanical strength, and thermal and mechanical impact strength, since mica powder is in the form of thin flakes as mentioned above, when splitting occurs, When delamination occurs and the thickness becomes thinner when subjected to erosion, the molded product has elasticity due to the properties mentioned above, i.e., the mica flakes are arranged in a layered manner, and therefore the static mechanical The characteristic of high strength naturally decreases rapidly. Next, regarding the relationship between the heat resistance temperature of the glass-mica plastic body and the raw glass, it is directly related to the characteristics of the raw glass, especially the temperature at which it melts and softens, and the higher the melting and softening temperature of the raw glass, the higher the heat resistance temperature. However, the heating temperature during molding also inevitably becomes high.
This means that the static mechanical strength and the thermal and mechanical impact strength of mica are necessarily lower. In other words, the heating temperature during molding is closely related to the melting and softening temperature of the vitreous powder used, and when the melting and softening temperature is low, a product with high thermal and mechanical impact strength can be obtained, but the heat resistance temperature is low. I can only change things. Conversely, when the melting and softening temperature is high, a material with a high heat resistance temperature can be obtained, but the thermal and mechanical impact strength tends to decrease. The above relationship is thought to be due to the reaction between the glassy powder and the mica powder, which causes the mica powder to be decomposed and eroded. [Problems to be solved by the invention] In glass-mica plastic bodies manufactured by conventional manufacturing methods, static mechanical strength and thermal and mechanical impact strength inevitably decrease as the heat resistance temperature increases. There is an unavoidable fatal flaw. The present invention aims to eliminate the above-mentioned fatal defects and to obtain a glass-mica molded body that has a high heat resistance temperature and high static mechanical strength and thermal and mechanical impact strength that are of practical value. The purpose was to establish a method of molding by lowering the heating temperature during molding. [Means for Solving the Problems] The present invention uses, as a glass raw material, a vitreous powder in which a part of the vitreous powder with a high glass transition temperature is replaced with a vitreous powder with a low glass transition temperature, and uses mica powder as a glass raw material. A process of preparing a raw material powder by mixing the raw material powder, a process of creating a preformed body by cold pressing the raw material powder, a process of heating the preformed body to a temperature at which the vitreous powder flows under pressure, a process of heating the preformed body The process of loading the preform into a mold that has been heated in advance to a temperature between 50°C and 550°C higher than the glass transition temperature of glass, which has a low glass transition temperature, and pressurizing it, and after cooling, the mold is disassembled. The present invention relates to a method for manufacturing an insulating heat-resistant material, which comprises a step of taking out a molded body. [Example] Glassy powders with a high glass transition temperature used in the present invention include powders with a glass transition temperature of 400 to 700°C,
Preferably, a material having a temperature of about 500 to 600°C and a particle size of 200 mesh or less is used, and there are no particular limitations on the material, and general commercially available products can be used. In a glass-mica plastic body, the raw material powder is heated to a temperature at which the vitreous powder contained therein melts and its viscosity decreases, and when pressure is applied in the heated state, the molten vitreous powder flows and forms a thin film. It forms a shape on the surface of the mica flakes and acts as an adhesive. However, when the temperature of the molded product increases, this glass softens and no longer functions as an adhesive. Therefore, in order to obtain a molded product with a high heat resistance temperature, it is necessary to use a material with a high glass transition temperature and a high softening temperature. The glassy powder with a low glass transition temperature used in the present invention has a glass transition temperature of 290 to 400°C,
Preferably, it is a vitreous powder of 200 mesh or less at a temperature of 300 to 400°C, and any glass with a low melting point such as lead borate glass or lead borosilicate glass is sufficient.There are no particular compositional limitations, and commercially available Even if the product meets the above conditions, it can be used. When a high melting point glass and a low melting point glass are mixed and heated to raise the temperature, the low melting point glass melts first, and the viscosity decreases as the temperature rises. The viscosity of high-melting glass also decreases when the temperature is higher than the glass transition temperature, but in order to make it fluid and form a film by heating, and exhibit adhesive properties, it must be heated to an extremely high temperature.
However, when mixed with low melting point glass and heated, the particles become deformable under pressure even at temperatures where high melting point glass does not exhibit adhesive properties. When pressure molded at this temperature, the high melting point glass deforms into flakes (it has no adhesive properties), and the low melting point glass, whose viscosity has been sufficiently reduced, flows and adheres to the mica flakes. As a result, a molded product with high density can be obtained. In addition, the heat-resistant temperature of the molded product obtained in this way is that the low melting point glass exists as an extremely thin film, so it will not swell even when the temperature rises; This is when the high melting point glass is deformed. The amount of the vitreous powder with a high glass transition temperature to be replaced by the vitreous powder with a low glass transition temperature is 3% in the vitreous powder with a high glass transition temperature.
~20% (volume %, same below), preferably 4~15
%. The mica powder used in the present invention is limited to synthetic mica. Among synthetic mica, fluorine-containing gold mica is preferred. The larger the size of the mica powder, the more desirable it is.
If the powder is too coarse, the mica powder tends to be poorly attached to each other. The size of mica powder is preferably 50 to 200 mesh;
~100 meshes is more preferred. The higher the content of mica powder, the more the thermal and mechanical impact strength tends to increase, but the static mechanical strength tends to decrease.
~65% is overall preferred. Raw material powder is prepared by mixing a vitreous powder with a high glass transition temperature, a vitreous powder with a low glass transition temperature, and mica powder in any order, but there are no particular restrictions on the mixing method, and it is commonly used. mixed by appropriate mixing means. A preform is produced from the raw material powder thus prepared by cold pressing. Next, the preform is heated to 400°C at a temperature higher than the glass transition temperature of the glass material, which has a high glass transition temperature.
The preform was held in an electric furnace for about 40 minutes at a temperature that was set to rise in 25°C increments starting from .
It is loaded into a mold that has been heated in advance to a temperature 50°C higher than the glass transition temperature of glass with a low glass transition temperature (however, the maximum temperature is 550°C), and is pressurized at a total pressure of about 38.5 tons to reach the glass transition temperature. The material is cooled while continuing to be pressurized to a temperature that is about 20°C lower than the glass transition temperature of the glassy material. In this way, an insulating heat-resistant material is produced by the method of the present invention. Next, the method of the present invention will be explained based on examples. Examples 1 to 4 and Comparative Examples 1 to 7 Glassy powder shown in Table 1 pulverized to 200 meshes and synthetic fluorine-containing gold mica having a particle size of 50 to 200 meshes were blended in the proportions shown in Table 2. Then, 5% water was added to the mixture to make it wet, and a disk was formed by cold pressing using a disk molding die with a diameter of 68 mm. Thereafter, it was dried to remove moisture, and a disc-shaped preform was produced. The obtained preforms were heated at a temperature higher than the glass transition temperature of the glassy material having a high glass transition temperature in Examples 1 to 4, and at a temperature higher than the glass transition temperature of the glassy material used in Comparative Examples 1 to 7. 400 at temperature
After being held in an electric furnace for 40 minutes at the heating temperature shown in Table 2, which was set at 25 degrees Celsius as a starting point,
It was loaded into a mold and molded under a total pressure of 38.5 tons. In addition, as a molding mold, a mold consisting of a wall part of a divided structure with an inner diameter of 70 mm, a frame for tightening the wall part, a receiving metal fitting to the wall part, and a pressurizing metal was used.
In Examples 1 to 4, when the glass transition temperature of the vitreous powder used in Comparative Examples 1 to 7 was 500°C or lower, At a temperature 50 °C higher than the glass transition temperature of the glassy powder with a low glass transition temperature, and at a temperature 50 °C higher than the glass transition temperature of the glassy powder used in Comparative Examples 1 to 7,
However, in all cases, the maximum temperature was limited to 550°C, and the preform was loaded when heating was completed. Molding was carried out at a temperature 20°C lower than the glass transition temperature of each glassy powder with a low glass transition temperature in Examples 1 to 4, and at a temperature 20°C lower than the glass transition temperature of the glassy powder used in Comparative Examples 1 to 7. After cooling, a plate with a diameter of 70 mm and a thickness of 14 mm was formed. After polishing the top and bottom surfaces of the resulting molded plate by 2 mm each to make a 10 mm thick plate, a 15 x 30 mm plate with a thickness of 10 mm was taken out from the center and any cracks in the metal were removed.
A color check was conducted to check for cracks, pores, etc. in the molded product, and the lowest temperature at which color did not occur was determined as the heating temperature. The plate whose heating temperature was measured was used as a sample, and it was placed in an electric furnace set at a temperature of 15°C higher starting at 310°C.
The thickness was measured at room temperature after cooling, and the maximum temperature at which the thickness of 10 mm did not change was determined as the heat resistance temperature. In these results and Examples 1 to 4, the glass transition temperature of the glass with a high glass transition temperature, the difference between the glass transition temperature of the glass used in Comparative Examples 1 to 7 and the heating temperature, and the difference between the glass transition temperature and the heating temperature in Examples 1 to 4. Table 2 shows the glass transition temperature of glassy materials having high glass transition temperatures, and the difference between the glass transition temperature and the heat resistance temperature of the glassy materials used in Comparative Examples 1 to 7. Also, Example 1~
Regarding No. 4, the reduction in heating temperature due to the use of glass with a low glass transition temperature is also considered as a second factor.
Shown in the table.

【table】

【table】

[Table] As shown in Table 2, in the case of comparison column 1, the glass transition temperature is 304℃, and the heating temperature is 450℃, and the difference is 146℃, but in comparative example 2, the difference is 146℃.
205°C, and 316°C in Comparative Example 3, and the difference becomes larger as the glass transition temperature increases. However, in Comparative Examples 4 to 7, the glass transition temperature is as high as 483 to 582°C, but the difference is between 337 to 343°C, and there is no linear increase in the difference in Comparative Examples 1 to 7. Next is the heat resistance temperature, which is 340℃ in Comparative Example 1.
The glass transition temperature is 36°C higher than the glass transition temperature of 304°C, but in Comparative Example 6, the heat resistance temperature is 595°C, which is 32°C higher.
In Comparative Example 7, the temperature was 28°C higher at 610°C, and the difference was the smallest.
In Comparative Example 2, the difference is the largest at 43°C, but no large fluctuations are shown. The differences between the glass transition temperature of the glasses used in Comparative Examples 1 to 7 and the heating temperature and heat resistance temperature vary, but this is due to the viscosity characteristics of each glass with respect to temperature, as well as the heating temperature of 25°C. Regarding the heat resistance temperature, it is thought that the setting of the temperature increase condition of 15°C had an effect. Regarding the relationship between the heat-resistant temperature and the heating temperature in Comparative Examples 1 to 7, in order to obtain a heat-resistant temperature of 610°C, it is necessary to use glass with a glass transition temperature of about 580°C and set the heating temperature to about 925°C. There is. However, when the heating temperature reaches approximately 900°C, the reaction between the synthetic mica powder and the glass begins to proceed rapidly, and the synthetic mica powder undergoes significant erosion. As a result, the static mechanical strength and thermal and mechanical impact strength are extremely reduced, and the characteristics of the glass-mica plastic body almost disappear. This means that it is not possible to obtain a material with a high heat resistance that maintains mechanical strength that is useful, which is a fatal flaw. In the case of Example 1, the heating temperature was 650°C,
Compared to Comparative Example 3, the temperature is lowered by 75°C.
In the case of Example 2, the heating temperature was 775°C, and in the case of Example 3
800℃ in the case of Example 4, 825℃ in the case of Example 4
, and each heating temperature is lowered by 100°C compared to Comparative Examples 5 to 7. In addition, the heat resistance temperature is 445℃ in Example 1, and 445℃ in Example 4.
The temperature was 610°C, and both exhibited heat resistance properties equivalent to those of Comparative Examples 3 and 7, which did not use Glass No. 1, which has a low glass transition temperature. For example, the composition of Comparative Example 7 was heated to
When molded at 825°C, it was molded to a thickness of approximately 14 mm, and although it can be seen that the glassy material was deformed, a color check showed that it was completely colored and pores remained. This heating temperature of 825°C is 242°C higher than the glass transition temperature of the glass used, and when glass powder alone is applied onto an iron plate and held in an electric furnace at 825°C for 40 minutes, the surface becomes glossy and smooth. Although it forms a surface and melts, the viscosity has not decreased sufficiently and it is not in a state where it flows under pressure and completely adheres the mica flakes. On the other hand, the reason why the molded product heated at a heating temperature of 925° C. is not colored at all by color check is thought to be because the viscosity of the glass has decreased and the mica flakes are completely adhered. However, if the glass content is less than 30%, the heating temperature should be increased to 925℃.
However, it is colored by color check. In addition, when the heating temperature is 825℃, the glass content is
Even at 70°C, it is colored by color check, and the relationship between the viscosity of the glass itself is clearly visible. In Example 4 according to the method of the present invention, the heating temperature
By molding at 825°C, a molded product with no coloration was obtained by color check, but this is because glass No. 1, whose viscosity has greatly decreased, is separated by mica flakes and between glass No. 7, which has been deformed by pressure, and mica flakes. It is thought that the materials were completely adhered to each other, making it impossible for air bubbles to exist. In Example 4, 20% of Glass No. 7, which has a high glass transition temperature, is replaced with Glass No. 1, which has a low glass transition temperature, so that Glass No. 1 is present at 8% of the total. As a result of repeated experiments, it has become clear that what is directly related to the reduction in heating temperature is not the content in the total amount of glass, but the content of low glass transition temperature glass in the raw material powder. 3% glass with low glass transition temperature
The effect can be obtained by the presence of the above.
When the content ratio increases to 20%, it is effective in lowering the heating temperature, but the heat resistance temperature begins to be affected. Next is the relationship between the content ratio of glass with a low glass transition temperature and the heat resistance temperature.
In the following cases, a molded product molded at a low heating temperature maintains the same heat resistance temperature as a molded product molded at a high temperature without containing this glass with a low glass transition temperature. Although the present invention has been explained with reference to plate materials, this glass-mica plastic body is also widely used in structural insulators with embedded metal bodies, such as heat-resistant airtight terminals. It can be effectively used for such purposes. [Effects of the Invention] In the manufacturing method of the present invention, glass with a high glass transition temperature is partially replaced with glass with a low glass transition temperature as the raw material glass, and this and mica powder are mixed to form the raw material glass. Since it can be prepared by the same process as the conventional molding method, the heating temperature of the raw material is lowered, and a product with the same heat resistance temperature can be obtained. Since the heating temperature of the raw material is lowered, the mica powder is less likely to be eroded into a glassy state, and the static mechanical strength and thermal and mechanical impact strength are less likely to deteriorate. As a result, a material that maintains high mechanical strength while maintaining high heat resistance properties is obtained, and the fatal defect of the conventional method that mechanical strength inevitably decreases as the heat resistance temperature increases is eliminated. Therefore, it is an excellent static material that can be effectively used for spacers that hold the high-frequency coils mentioned above, and wedge materials used when assembling high-temperature metal parts while maintaining precise spacing and insulation. An insulating heat-resistant material that maintains mechanical strength and thermal and mechanical impact strength can now be obtained, and its practical and technical effects are extremely large. Furthermore, lowering the heating temperature not only extends the life of the heating equipment but also directly leads to lower production costs, and has significant secondary effects.

Claims (1)

[Claims] 1 A step of preparing a raw material powder by mixing a glassy powder with a glassy powder with a low glass transition temperature with a mica powder as a glass raw material, in which a part of the glassy powder with a high glass transition temperature is replaced with a glassy powder with a low glass transition temperature, a raw material powder A process of preparing a preform by cold pressing, a process of heating the preform to a temperature at which the vitreous powder flows under pressure, and a process of heating the preform to a temperature at which the vitreous powder flows under pressure. The process of charging an insulating heat-resistant material into a mold heated to 50°C to 550°C higher than the glass transition temperature and pressurizing it, followed by the step of disassembling the mold and taking out the molded product after cooling. Production method.