JPS6335911B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a powder vacuum insulation board. Traditionally, materials such as glass fiber and urethane foam have been used as insulation materials for keeping things warm and cold. Glass fibers have good heat resistance, but their thermal conductivity is
It is 0.03 to 0.05 Kcal/mh℃, and the insulation effect is not very good. In addition, heat insulating boards made by foaming hard polyurethane injected into the gaps between walls are commonly used as low-temperature cold insulation materials for refrigerators, etc., but the thermal conductivity of this hard polyurethane is 0.015 Kcal/mh°C.
has been achieved, but it is not easy to further improve the heat insulation properties. Furthermore, a method is known in which liquefied petroleum is used as a cold insulation board for tanks, freezers, etc. by constructing a double-walled tank container, filling the gap with foamed perlite powder, and vacuum sealing. Moderately,
It is also said that the better the degree of vacuum, the better the insulation effect. In this conventional method for manufacturing powder vacuum insulation boards, the commonly known pearlite powder has a small bulk specific gravity of about 0.08 g/ ^cm3 , and this light powder is spread between two walls. When filling a gap and evacuating the gap using a vacuum pump, light pearlite powder may be attracted to the vacuum pump and ejected, or the evacuation function of the vacuum pump may be degraded. It has the disadvantage of being extremely inefficient when manufactured industrially. Furthermore, since the container used to fill the powder is required to be made of a material with strong mechanical strength that can withstand high vacuum pressure, metal containers such as iron are generally used, which has the drawback of being extremely heavy. Furthermore, although it is necessary to maintain the container in a high vacuum, it is very disadvantageous from an industrial perspective, such as the high cost required to achieve perfect airtightness at the joints of the container components. The present invention eliminates the drawbacks of the conventional powder vacuum insulation board manufacturing method, and when the inside of the container is evacuated, the filled powder is sucked into the vacuum pump and discharged. It has the advantages of being extremely lightweight, without reducing the evacuation function of the vacuum pump, and making it possible to easily completely seal the container filled with powder, making it industrially advantageous. A method for manufacturing a powder vacuum insulation board is provided. A feature of the method of the present invention is that a film-like plastic bag filled with a finely powdered heat insulating material is placed in a vacuum container, and the inside of the film-like plastic bag and the vacuum container are made to have approximately the same degree of vacuum. The open part of the film-like plastic bag is sealed by heat sealing, and the inside of the vacuum container is returned to normal pressure.
The purpose of the present invention is to compress and mold the film-like plastic bag into the lightweight fine powder heat insulating material. There are no particular restrictions on the material of the film-like plastic container that can be used in the method of the present invention, but it should have low gas permeability, little vacuum leakage, high breaking strength, and easy thermal sealing. It is preferable to use a film bag. For example, polystyrene, polyvinyl alcohol, saponified polyvinyl alcohol, nylon, polyester,
Single-layer or laminated laminate films of two or more materials such as polypropylene, oriented film, aluminum foil, aluminum vapor-deposited film, and polyvinylidene chloride are effective, but in particular, by using laminate films for containers, even better results can be achieved. effect can be obtained. There are no particular restrictions on the material of the powder material, but hollow spherical shells such as foamed perlite and microballoons, porous powders with large specific surface areas such as silica, calcium silicate, and diatomaceous earth, or hydrated silicic acid and methylated hydrated silicic acid, etc. It is preferable to use fine powder with a small single particle size, as it can provide better heat insulation effects. The vacuum container must be made of a material with strong mechanical strength that can withstand high vacuum, such as iron, stainless steel, cast metal, or glass, and must be equipped with a heat sealing device inside the container. The heat sealing device is equipped with hot plates facing each other, a film is inserted between the hot plates, and the hot plate is heated while applying pressure to the hot plate to bond the film from both sides. A device is required to heat-seal the film, cool it and solidify it, and then bond the film. As a heating source for the hot plate, a normal heating method such as an impulse method or a resistance wire energization method, in which a large current is applied to a resistance wire for a short time to heat it, can be used. Hereinafter, the present invention will be explained in more detail with reference to Examples. In this example, thermal conductivity was measured at a temperature difference between 13°C and 34°C using a Dynatek K-Matic thermal conductivity measuring device in accordance with ASTM-C518. did. Example 1 Silica powder (bulk specific gravity 0.11g/cm ³ , powder diameter
0.02μm) 446g into a multilayer laminate film (total film thickness
120 μm) and filled into a film bag with a polyethylene layer on the inside. Next, a vacuum container (volume 20) equipped with an impulse type thermal sealing device
After placing the film bag filled with the powder so that the open part of the film bag is located between the two opposing heating plates in the bag, use a vacuum pump (evacuation capacity 800
/min) to reduce the inside of the vacuum container to approximately 1 Torr.
The vacuum level was evacuated. At this time, the inside of the film bag filled with powder is also evacuated through the open part of the film bag, and the vacuum level becomes the same as the inside of the vacuum container. In this way, while maintaining the vacuum inside the vacuum container and the inside of the film bag filled with powder, the two mutually opposing heating plates of the heat sealing device are pressed to the open part of the film bag, A large current was applied for about 1 second. At this time, the polyethylene on the inner surface of the film bag melts and adheres to each other. Then after cutting off the current,
After continuing to pressurize the hot plate for about 3 seconds to solidify the adhesive portion, the opposing hot plate was opened to completely seal the filled powder. Next, after introducing outside air into the vacuum container and returning it to atmospheric pressure (760 Torr), the film bag filled with powder was taken out and the width was 28 cm.
A powder vacuum insulation board with a vertical width of 28 cm and a thickness of 3 cm was obtained. In the method for manufacturing a powder vacuum insulation board as described above, it was never observed that the powder filled in the film bag was discharged to the outside of the film bag.
In addition, from the appearance, it was confirmed that the film bag was strongly attracted to the internally filled powder and adhered closely to the powder, and that the vacuum seal was complete. Furthermore, as a result of measuring the thermal conductivity, it was 0.005Kcal/mh℃, and even after being left for 10 days, the thermal conductivity was 0.005Kcal/mh℃.
There was no fluctuation at all, confirming that the vacuum seal was perfect. The specific gravity of the obtained powder vacuum insulation board was 0.19 g/cm ³ and was extremely lightweight. Further, the time required for the above manufacturing method is about 15 seconds, and the powder vacuum insulation board can be manufactured in a very short time. Example 2 Powders such as hydrated silicic acid, calcium silicate, diatomaceous earth, expanded perlite, silica microballoons, and methylated silicic acid, and multilayers made of polyethylene, polyvinyl alcohol, polyester, oriented polypropylene, polyvinylidene chloride, aluminum foil, aluminum vapor deposition, etc. Using a laminated bag, use the same method as in Example 1 to make a bag with a width of 28 cm and a height of 28 cm.
We prototyped each powder vacuum insulation board with a shape of 28 cm and a thickness of 3 cm. The following table shows the manufacturing process and the characteristics of the obtained powder vacuum insulation board for each case.

[Table] As is clear from the above table, no powder filled in the film bag was observed to be discharged outside for any of the samples. Also, from the outside, the film bag was strongly attracted to the powder packed inside and adhered tightly to the powder, making it completely vacuum-sealed. Furthermore, as a result of measuring the thermal conductivity immediately after sample preparation and 10 days later, almost no change over time was observed.
It was confirmed that the vacuum seal was complete. The specific gravity of the obtained powder vacuum insulation board is 1
g/cm ³ or less, and was extremely lightweight. Additionally, it took less than 60 seconds to vacuum-seal each heat insulating plate, making it possible to manufacture it in an extremely short time. As is clear from the above description, the present invention provides for placing the film-like plastic bag filled with the heat insulating material in a vacuum container, and maintaining the same degree of vacuum in the film-like plastic bag and the vacuum container. The open part of the film plastic bag is sealed by heat sealing, and the inside of the vacuum container is then returned to normal pressure to compress the film plastic bag into the fine powder heat insulating material. This is a method for producing a powder vacuum insulation board characterized by molding. (1) The use of fine powder reduces the contact area between powder particles, which reduces heat conduction due to contact between particles, and It is possible to obtain a heat insulating board with excellent efficiency. (2) Since there are few contact areas between powder particles, the air in the gaps between the powder particles can be evacuated to a predetermined degree of vacuum in a short time. (3) Generally, it is difficult to mold powder tightly and increase its strength, but since a deformable film-like plastic bag is used, the pressure difference between the inside and outside of the bag makes the bag strong and strong. Because it is compressed into the powder side, it is easy to compact the powder, maintain the external shape of the vacuum insulation board, and obtain strength. (4) As is clear from the fact that the specific gravity after molding is larger than before molding, the powder is compressed after molding and the voids between the powders become smaller, so the 1Torr
High thermal insulation performance can be obtained with a reduced pressure level of about 100 degrees. (5) During evacuation, the degree of vacuum inside and outside the bag is the same, so the powder will not be discharged to the vacuum pump side, and since there is no compression of the powder, the air in the gap will be short-circuited. Can be drained in time. It has the following effects and is an industrially very advantageous manufacturing method.

Claims (1)

[Scope of Claims] 1. A film-like plastic bag filled with at least one kind of fine powder heat insulating material selected from silica, hydrated silicic acid, diatomaceous earth, perlite, calcium silicate, and methyl silicic acid with an average particle size of 150 μm or less. is placed in a vacuum container, the inside of the film plastic bag and the vacuum container are evacuated to the same degree of vacuum, the open part of the film plastic bag is sealed by heat sealing, and then the vacuum container is A method for manufacturing a powder vacuum insulation board, which comprises returning the inside of the container to normal pressure and compressing the film-like plastic bag into the fine powder insulation material to form the bag. 2. The method for manufacturing a powder vacuum insulation board according to claim 1, wherein the film-like plastic bag is a film coated with at least aluminum vapor.