JPS6116127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for continuously producing inorganic insulators. More specifically, the present invention relates to a method for continuously producing an inorganic insulator that is heat resistant, nonflammable, and has excellent arc resistance and impact resistance.

Conventionally, inorganic fibers and powders such as asbestos fibers, glass fibers, mica powders, etc. are used as molding materials, and electrical insulators are made by bonding them together by heat-pressing molding using a mixture of boric acid and zinc oxide as a binder. The manufacturing method is described in Tokuko No. 54-7539 and Tokuko Sho.
This method is known from, for example, Japanese Patent No. 54-7360. According to the methods described in those specifications, molding material is filled into a mold heated to 130 to 200°C, and a pressure of 100°C is applied.
It is described that a molded product can be obtained by heat-pressing molding at ~300 Kg/cm ² .

In other words, boric acid, which is the main component of the binder, melts due to thermal changes to bind inorganic fibers or inorganic powder, forming zinc oxide and hydrated borate, which are present as components of the binder. It aims to improve water resistance, and at the same time, because it has a high melting point, it also improves heat resistance. However, whether or not the resulting molded product has excellent water resistance and heat resistance is closely related to whether or not a hydrous borate is formed.

Therefore, the present inventors investigated a method for forming a hydrous borate in a molded product, and found that it can be formed by simply heating and pressing a molding material containing boric acid mixed with zinc oxide and further adding inorganic fibers. It was found that the decomposition of boric acid due to thermal changes plays an important role in the formation of hydrated borate.

In other words, when molding a molding material under heat and pressure, if the decomposition water due to the thermal change of boric acid is allowed to freely escape to other than the molding material or molded product, for example,
2ZnO・3B ₂ O ₃・7H ₂ O, and even 2ZnO・3B ₂ O ₃・
Hydrous borates such as 3H ₂ O are difficult to form, and the resulting molded products are poor in not only water resistance but also heat resistance. On the other hand, if the decomposition water due to thermal changes in boric acid is retained in the molding material or molded product, the above-mentioned hydrated borate is formed,
It has been found that a molded product with excellent water resistance and heat resistance can be obtained.

As a result of examining the conventionally known manufacturing methods based on these revealed facts, it became clear that they included the following problems.

(1) When filling a molding material into a mold heated to 130-200°C, the boric acid contained in the molding material as a binder component is exposed to heat from the time of filling until it is pressurized. Starts changing ( _{H3BO3 at} 90℃
In particular, the boric acid in the molding material in contact with the mold changes heat in a short period of time, and the decomposition water of the boric acid due to the thermal change escapes outside the molding material and fills it. If the time is long, the boric acid will be pressurized in a state where the thermal change has progressed, making it difficult to form a hydrated boric acid salt, and the resulting molded product will have poor water resistance and heat resistance.

(2) Conventional manufacturing methods involve heating and pressurizing the molding material, then lowering the temperature of the hot platen or mold below the molding temperature while maintaining the pressure to remove the molded product. This method is used because if the molded product is removed from the mold without lowering its temperature below the temperature during molding, the molded product will swell or crack.

The molded product swells due to the temperature during molding, due to the binder,
In particular, this is because the heat-changeable product of boric acid is soft.
However, the phenomenon of blistering is likely to occur when hydrated borate is not formed, and is considered to be a manifestation of a defect in the conventional manufacturing method. In addition, cracks in molded products are often caused by the high amount and vapor pressure of free water in the molded product, and conventional manufacturing methods lower the vapor pressure of free water by lowering the temperature (here, The term "free water" refers to excess water contained in the molded product, other than the water necessary to form a hydrated borate, out of the water generated by decomposition during thermal change of boric acid). In other words, by reducing the amount of free water, boric acid and zinc oxide as a binder in the molded product form a hydrated borate, which becomes hard even at the molding temperature. It is possible to take out the molded product directly from the mold after heat-pressing molding without requiring such a cooling step.

However, conventional manufacturing methods require a cooling process as described above, so when molding a large number of molded products, the temperature of the heating platen or mold must be raised each time, reducing energy consumption and molding time. From this point of view, manufacturing costs are high.

As mentioned above, conventional manufacturing methods tend to have defects in characteristics such as water resistance and heat resistance, and at the same time, the manufacturing efficiency is significantly inferior. As a result of investigating excellent inorganic insulators, the following was discovered.

First, during molding, the decomposed water of boric acid is prevented from escaping to the outside of the molding material or molded material, and the material is heated and pressed to form a hydrated boric acid salt, thereby obtaining a molded product with excellent water resistance and heat resistance.

If it is possible to remove the molded product from the mold without cooling it after heating and pressing, there is no need to raise the temperature of the heating platen or the mold again in the next molding process, so the cycle of heating and pressing time Molded articles can be obtained continuously, and inexpensive inorganic insulators can be obtained.

As a result of intensive research to establish a method to make these points a reality, we developed a pressurizing device with a heating platen device that can heat up to 160-170℃, a mold, a device for transporting the mold, and a mold release device. The equipment consists of a cooling device, a device for cooling the molding material to below 90°C, and a device for filling the mold with the molding material. Immediately after filling a mold at a temperature of less than 90℃ with a molding material with a boric acid content within the range of 8.0 to 22.5% and inserting it between hot plates heated to 160 to 170℃, 50 kg/cm Pressurize with a pressure of ² or more, hold the pressure for at least 5 minutes after the temperature of the molding material reaches 155 to 165℃, and then repeat the process of taking out the molded product from the mold to continuously form an inorganic insulator. Discovered a continuous manufacturing method that allows molding
We have now completed the present invention.

Next, the manufacturing method of the present invention will be explained in detail.

First, in order to prevent decomposition water from escaping due to thermal changes in boric acid, it is preferable that the temperature of the mold be less than 90° C. when filling the mold with the molding material. If the temperature of the mold is 90° C. or higher, boric acid as a binder in the molding material exhibits thermal changes, which is not preferable. That is, at least when filling the mold with the molding material, it is necessary that the temperature is such that boric acid does not exhibit any thermal change. After filling the mold with molding material, 160 ~
Insert between heating plates that have been heated to 170℃ (the heating plates are attached to a pressurizing device), and immediately weigh 50 kg/
The temperature of the molding material is 155 cm by pressing with a pressure of more than ² cm.
After the temperature reaches ~165°C, heat and pressure is maintained for 5 minutes or more, and then the molded product is taken out from the mold. The temperature of the heating plate is preferably 160 to 170°C. If it is lower than 160°C, it will not be possible to form hydrated borate sufficiently, resulting in poor water resistance and heat resistance. If it is higher than 170°C, boric acid will deteriorate. Since the decomposed moisture generated by thermal changes actively moves out of the molded product, it is difficult to form a sufficient amount of hydrated borate, resulting in poor water resistance and poor heat resistance, both of which are undesirable.

In addition, the reason for holding heat and pressure for more than 5 minutes after the temperature reaches 155 to 165℃ is to ensure that boric acid is sufficiently thermally changed at a temperature of 155℃ or higher, and that zinc oxide (ZnO) is This ^{is because} hydrated borate is formed by the reaction of This is because acid salts cannot be formed sufficiently.

There is a method of cooling the temperature of the hot platen by flowing cooling water to lower the temperature of the mold (lowering the temperature of the molded product) and taking out the molded product, but in the present invention, the temperature of the hot platen remains the same and the molded product is removed. The molded product can be removed from the mold.

In other words, in order to take out the molded product without cracking or blistering at high temperatures as mentioned above, it is necessary to form a hydrated boric acid salt in the molded product and reduce the amount of free water generated from boric acid that does not contribute to the reaction. It needs to be regulated. By the way, the amount of free water that occupies a molded product is regulated in proportion to the content of boric acid in the molding material, so it is possible by adjusting the content of boric acid in all constituent materials of the molding material. Therefore, as mentioned above, the conventionally known boric acid-oxidation Zinc-based binders, such as H ₃ BO ₃ −ZnO-based, H ₃ BO ₃
-B ₂ O _{3 -} In a molding material using a ZnO-based composition in combination with inorganic fiber or inorganic powder
As a result of various studies on the content of H ₃ BO ₃ , it was found that the content of H ₃ BO ₃ in the molding material was within the range of 8.0 to 22.5%, particularly preferably within the range of 10.0 to 18.5%. It became clear that the requirements were met.

If the content of H ₃ BO ₃ in the molding material is lower than 8.0%, it is difficult to obtain a dense molded product even if high pressure (500 Kg/cm ² or more) is applied, and if it is higher than 22.5%, it is difficult to obtain a dense molded product. If the same cooling process as conventional methods is not used, cracks are likely to occur, which is not desirable.

Note that resin powder, glass powder, metal oxide, metal hydroxide, etc. may be added to the molding material used in the present invention and used in combination.

The inorganic insulator of the present invention obtained by the above-mentioned range of H ₃ BO ₃ content in the molding material and the above-mentioned production method should sufficiently recognize the formation of hydrated borate as judged from X-ray diffraction etc. molded products bound with mica powder have excellent heat-resistant, non-flammable properties that do not melt even when heated to over 700°C, and are also arc resistant and impact resistant. It is an excellent inorganic insulator.

Such inorganic insulators can be used as arc-extinguishing materials for blowout type circuit breakers, insulating materials for vehicle resistors, insulating washers for electric furnaces, and other equipment that particularly requires heat resistance and nonflammability. Next, the manufacturing method of the present invention will be explained based on the drawings.

Fig. 1 is a plan view of the pressurizing device for continuously obtaining molded products, Fig. 2 is a cross-sectional view of the state in which the molding material is filled and conveyed into the mold, and Fig. 3 is the state of heating and pressure molding. 4 is a sectional view showing the mold release state, FIG. 5 is a sectional view showing the mold cleaning state,
FIG. 6 is a cross-sectional view of the mold being cooled, and FIG. 7 is a cross-sectional view of the mold filled with molding material from the filling material.

In FIG. 1, molding material 12 is stored in a filling device 7, and when a mold 3 is conveyed downward by an endless belt 8 made of stainless steel, a predetermined amount of molding material 12 is filled from the filling device 7. Thereafter, it is transported to a vibration device 9, and the molding material 12 in the mold 3 is leveled. Mold 3 is endless belt 8
It is fixed on the top and conveyed by the movement of the endless belt 8. The money mold 3 is composed of a frame 3a and a bottom plate 3b, and a Teflon-treated part 3c is provided on the surface in contact with the molding material 12 to facilitate mold release. The endless belt 8 is moved in the direction of the arrow in a predetermined cycle by a carrier roller 10 driven by a motor 14. The endless belt 8 in contact with the mold 3 is provided with a through hole 8a through which the head of the air cylinder 5c can pass during mold release in FIG.

In FIG. 2, the molding material 12 is
After being smoothed out, it is transported to the pressurizing device 1. At this time, a plurality of shallow grooves 10a are provided on the surface of the carrier roller 10 to prevent the endless belt 8 from slipping.

FIG. 3 shows a state in which heating and pressure forming is carried out by the pressurizing device 1 integrated with the hot platen device 2. The temperature is raised to 160-170℃ using an electric heater or steam. The heating platen device 2 located at the upper part serves as the presser of the mold 3, and as soon as it is conveyed into the pressurizing device 1, it is pressurized by the pressurizing device 1 with a pressure of 50 kg/cm ² or more, It is heated by the heating plate device 2. After the temperature of the molding material 12 in the mold 3 reaches 155 to 165°C, it is maintained for 5 minutes or more. The endless belt 8 is also heated and pressurized at the same time. After being held under heat and pressure, the pressure is released and the heating platen device 2 is separated from the mold 3, and the mold 3 is conveyed to the mold release device 4, held by the mold holding frame 4a, and placed in the air cylinder box. The bottom plate 3b of the mold 3 is pushed up through the through hole 8a of the endless belt by the air cylinder 4c inside the air cylinder 4b, and the molded product 13 is placed on the frame 3a.
When the molded product 13 is pushed up, the molded product 13 is thrown into the storage container 11 by the air cylinder 4d.

Next, the air cylinder 4c moves into the air cylinder box 4b, and at the same time is conveyed by the endless belt 8 to the cleaning device 5 shown in FIG. and the deposits are blown away. Note that the cleaning device 5 is provided within the local drainage equipment 5b.

After the cleaning of the mold 3 is completed, the mold 3 is transported by an endless belt 8 to a cooling device 6 shown in FIG. 6 and cooled between water cooling plates 6b. A water cooling pipe 6a is inserted into the water cooling plate 6b. The mold 3 is thereby cooled to a temperature below 90 DEG C. and transported to the filling device 7 in FIG. Thereafter, by repeating this operation, molded products 13 can be obtained continuously.
14 is a driving source.

The mold 3 is placed on an endless belt 8 so that it is always in one of the devices, and its cycle is determined by the heating and pressure molding time.

Next, the manufacturing method of the present invention will be explained with reference to Examples.

First, a molding material was prepared as follows. i.e. H ₃ BO ₃ (particle size 40-100 mesh)
A binder was prepared by mixing 3,287 g of ZnO, 740 g of B ₂ O ₃ (particle size: 40-100 mesh) and 1,973 g of ZnO (particle size: 1-10 μm) for 30 minutes in an Ishikawa crusher. Next, phlogopite powder (particle size 60 to 100) is added as an inorganic powder to the binder.
mesh) 6000g and MgO (electrofused magnesia, particle size 60-100 mesh) 6000g, Al ₂ O ₃ (α
2000 g of alumina (particle size 100-300 mesh) was further added and mixed for 10 minutes to prepare 20 kg of molding material 12.

The prepared molding material 12 was put into the hopper of the filling device 7, and the mold 3 was filled with about 200 g of the molding material 12. The mold 3 has a depth (height) of 50 mm and an inner diameter of 141 mm, and has a frame 3a and a bottom plate 3.
The one composed of b was used. Also, the molding material 12
The surface in contact with is a Teflon-treated portion 3c, which facilitates mold release of the molded product 13. Next, the endless belt 8 moves the molding material 12 to a vibrating device 9.
The molding material 12 was conveyed to vibrate the mold 3 to level the molding material 12. The molding material 12 was again conveyed by the endless belt 8 between the hot platens 2 attached to the pressurizing device 1, and then immediately pressurized by the pressurizing device 1. At that time, the temperature of the heating platen device 2 was raised to 165±5° C., and the pressing force was 300 Kg/cm ² . The temperature of the molding material 12 reached 155° C. 7 minutes after the molding material 12 was conveyed to the heating platen device 2, and was then held under heat and pressure for 5 minutes. When the temperature of the molded product 13 was measured, it was 163°C. Next, the pressure of the pressurizing device is released, the heating platen device 2 is released from the mold 3 and conveyed to the mold release device 4 by the endless belt 8, and the mold 3 is removed by the air cylinder 5c.
The molded product 13 was taken out. After that, molded product 13
was stored in the storage container 11.

On the other hand, the mold 3 from which the molded product 13 has been removed is conveyed to the cleaning device 5 by the endless belt 8, the deposits are removed by compressed air from the rotating brush 5a and the air nozzle 5c, and the endless belt 8 is again used to cool the cooling device 6 with water. It was cooled to a temperature of less than 90° C. between the plates 6b.

By repeating the above steps, it was possible to continuously mold a molded product, that is, an inorganic insulator. In the embodiment of the present invention, such a molded product is 12
Approximately 5.5mm thick, outer diameter
100 pieces of 141mm shape were created. All cracked,
There were no defects such as swelling or chipping.

By the way, in the example, the case where the boric acid content in the molding material was 16.43% was shown, but if the boric acid content was
In the case of 8.0%, out of 100 molded products, 5 to 8 have poor tightness and 3 to 4 have poor water resistance (24% in pure water).
After being immersed for a period of time, a molded product whose shape changed) was generated. On the other hand, if the boric acid content is 22.5%, the molded product
Out of 100 pieces, 12 to 15 pieces had curved wrinkles and cracks. From this result, the boric acid content is
When the ratio is out of the range of 8.0 to 22.5%, defects begin to occur in the molded products, and defects mainly caused by tightness and cracks increase significantly.

Comparing the manufacturing method of the present invention with the conventional manufacturing method, the time required to manufacture one molded article was 12 minutes as mentioned above in the manufacturing method of the present invention, but in the conventional manufacturing method. 60 as it includes the time to raise the temperature of the heating platen device 2 and the time to cool it down.
It took minutes.

Furthermore, in the conventional manufacturing method, the loss of thermal energy associated with raising and lowering the temperature of the heating platen device is large, resulting in extremely high manufacturing costs, and the resulting inorganic insulator is also expensive. In comparison, according to the manufacturing method of the present invention, it is possible to obtain a molded product by a continuous molding method, so the molding time is significantly shortened, the manufacturing cost is low, and the inorganic insulating material obtained is also inexpensive. In addition, the inorganic insulating material has particularly excellent heat resistance and other properties that are comparable to those of conventional products, so it can be applied to a variety of uses as described above.

As described above, the continuous production method of inorganic insulators of the present invention has extremely large practical effects compared to conventional production methods.

[Brief explanation of the drawing]

Figure 1 is a plan view of a pressurizing device for continuously obtaining molded products, Figure 2 is a cross-sectional view of the state in which the molding material is filled and conveyed into the mold, and Figure 3 is the state of heating and pressure molding. 4 is a sectional view showing the mold release state, FIG. 5 is a sectional view showing the mold cleaning state,
FIG. 6 is a sectional view of the mold being cooled, and FIG. 7 is a sectional view of the mold being filled with molding material from the filling device. Main symbols in the drawings: 1: Pressure device, 2: Heat plate device, 3: Mold, 4: Mold release device, 6: Cooling device,
7: Filling device, 8: Endless belt, 10: Carrier roller, 12: Molding material, 13: Molded product.

Claims (1)

[Claims] 1 Equipped with a pressurizing device and a mold that have a heating platen device that can heat up to 160-170℃, a device for conveying the mold, a mold release device, a device for cooling it to below 90℃, and a mold for filling the mold with molding material. Using equipment consisting of a device and a composition consisting of inorganic fiber or inorganic powder, boric acid and zinc oxide as a molding material,
Fill a mold with a boric acid content in the range of 8.0 to 22.5% into a mold at a temperature of less than 90℃.
Immediately after inserting the molding material between hot platens whose temperature has risen to 160-170°C, pressurize it with a pressure of 50 kg/cm ² or more, and after the temperature of the molding material reaches 155-165°C, hold the pressure for at least 5 minutes. A continuous manufacturing method for an inorganic insulator, characterized in that the inorganic insulator can be continuously molded by repeating the process of taking out a molded product from a mold.