JPS61103089A - Vacuum heat-insulating structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a vacuum insulation structure that can be used for insulation walls of household refrigerators and the like.

[Prior art]

Rigid polyurethane foam has been widely used as insulation material for household refrigerators. Its insulation performance has been improved year by year, and its thermal conductivity has been reduced to approximately 0.015kcal/mh'c, which is almost the theoretical limit value. I'm here. However, from the viewpoint of energy saving and space saving, there is a demand for a heat insulating material with even better heat insulating performance.

By the way, as a very good insulation method! “It is known for its air insulation properties and is used in liquefied gas tanks, etc.
This is a container made of metal or the like filled with a heat insulating spacer material, evacuated to a high vacuum, and completely sealed. This is done by evacuation to a high vacuum, which lengthens the mean free path of the gas molecules in the heat insulating spacer material and prevents collisions between gas molecules, thereby hindering heat conduction.
A thermal conductivity of less than l/mh''C can be obtained. However, when using this vacuum insulation material for household refrigerators, etc., the insulation area is very small compared to liquefied gas tanks, etc., so the effect of surface heat conduction of the container is This will make the vacuum insulation method no longer effective.

Therefore, it is conceivable to form the vacuum container with a material other than metal that has low thermal conductivity, such as plastic.
Plastics have the drawback that gas permeation is large, and the degree of vacuum inside the container deteriorates due to air permeating from outside the container, which deteriorates its insulation performance. Another drawback is that plastic is weak in strength, and once a vacuum container is punctured by even a small scratch, the vacuum inside the container will be destroyed and the container will no longer function as a heat insulator.

One possible way to suppress this air permeation and increase the strength of the vacuum container is to embed the vacuum container in an organic foam insulation material, but even in this case, the foam of the organic foam insulation material contains chlorofluorocarbon gas, There are carbon dioxide gas produced by the reaction between the foaming aid water and incyanate, the raw material for the organic foam insulation material, as well as water vapor from unreacted water, which will diffuse through the organic foam insulation material over a long period of time. However, the problem remains that it gradually permeates into the vacuum container and deteriorates the degree of vacuum.

Normally, when vacuum insulation materials are used in liquefied gas tanks, etc., activated carbon is used as a so-called getter material that adsorbs gas molecules remaining in the vacuum container and maintains the degree of vacuum inside the vacuum container. Activated carbon is capable of adsorbing large quantities of all kinds of gases only after it is cooled to an extremely low temperature using liquefied gas, etc. When used in household refrigerators, etc., as in the present invention, it must be used at room temperature. Due to its inherent adsorption properties, although it was able to adsorb a considerable amount of organic gases such as chlorofluorocarbons, it was unable to adsorb most of the polar inorganic gases such as carbon dioxide and water vapor.

〔the purpose〕

In the present invention, by filling a plastic container with a silica-alumina adsorbent having a small pore diameter that performs adsorption as a getter material together with a heat insulating spacer material, the material diffuses through the organic foam heat insulating material and permeates through the plastic container. By capturing carbon dioxide gas and water vapor, the vacuum insulation inside the plastic container is prevented from deteriorating, and the insulation performance of the vacuum insulation material is maintained over a long period of time.

〔Example〕

The drawing is a sectional view showing the configuration of a vacuum insulation structure according to the present invention. In the figure, l is a plastic container and 2
is a heat insulating spacer material filled in the plastic container l. 3 is an organic foam heat insulating material in which the plastic container 1 is buried. 4 is the plastic container l
This is a silica-alumina-based adsorbent as a getter material that is filled together with the heat insulating spacer material 2 inside. The inside of the plastic container is evacuated to a high vacuum.

This plastic container l is for keeping the inside of the vacuum insulation material in a vacuum, and various thermosetting resins and thermoplastic resins can be used for the material, but it is easy to vacuum seal, and In order to suppress gas permeation through the vacuum container, a plastic laminate film having a metal foil or a metal vapor-deposited film is preferable.

In addition, the heat insulating subane material 2 is used to maintain the shape of the plastic container l against atmospheric pressure, and to divide the inside of the heat insulating space into smaller spaces to obtain a vacuum heat insulating effect even at a relatively low degree of vacuum. In terms of materials, inorganic powders such as perlite, calcium silicate, diatomaceous earth, and silica, fibers such as glass wool, ceramic wool, and rock wool, and organic foams such as foamed polyurethane and foamed urea resin can be used. .

Furthermore, the organic foam insulation material 3 is attached to the plastic container 1'5.
It works to reduce the amount of air (nitrogen, oxygen, water vapor, etc.) that permeates, and to increase the strength of the vacuum insulation material.

As this organic foam heat insulating material 3, commonly used rigid foam polyurethane or the like can be used. In the foaming material used for foaming this organic foam insulation material 30, chlorofluorocarbon gas is sometimes used alone, but in many cases water is also used as a foaming aid to lower the foaming pressure and increase the strength of the foam produced. They are added at the same time and used. This foaming aid water reacts with incyanate, which is a raw material for the organic foam insulation material, to completely generate carbon dioxide gas, and a foam is formed by this carbon dioxide gas and vaporized fluorocarbon gas.

The silica alumina adsorbent 4 is the organic foam heat insulating material 3
It is a getter material for adsorbing carbon dioxide gas and water (steam) that diffuse through the plastic container 1'z and gradually enter and permeate, and the pore size for adsorption is carbon dioxide gas or water vapor molecules. All containers having a diameter larger than that of the fluorocarbon gas and smaller than the molecular diameter of the fluorocarbon gas are used, thereby making it possible to maintain the plastic container 1 in a high vacuum.

By the way, among silica-alumina-based adsorbents, molecular sieve (synthetic zeolite) has a uniform pore diameter of A unit due to its crystal structure, and only molecules smaller than the pore diameter are adsorbed. Large molecules do not adsorb.

In other words, it has a so-called "molecular sieve" effect that separates and selects adsorbed molecules based on their pore diameters.

There are many types of molecular sieves depending on their chemical composition. For example, 3A, 4A, 5A.

There are 10X, +3X, etc., each with a pore diameter of 3A.

4A, 5A, 9A, IOA. The molecular diameter of carbon dioxide gas is approximately 3.5A, the molecular diameter of water vapor is approximately 28λ, and the molecular diameter of fluorocarbon gas is 5A or more, so if you use the 4A type molecular sieve, the molecular sieve will no longer adsorb fluorocarbon gas. Carbon dioxide gas and water vapor that cannot be adsorbed by activated carbon can be selectively adsorbed by molecular sieves, and the adsorption capacity of molecular sieves can be improved by using activated carbon, which is relatively inexpensive and has an excellent adsorption capacity for 7 ton gas, to adsorb the remaining fluorocarbon gases. Since it is possible to prevent the amount from decreasing due to adsorption of other gases, carbon dioxide and water vapor can be adsorbed more efficiently.

The method for encapsulating the silica-alumina-based adsorbent 4 as a getter material may be by mixing it with the heat-insulating spacer material 2 as in this embodiment, or by packaging only the silica-alumina-based adsorbent 4 in split pieces and encapsulating it. Needless to say, it's a good thing.

〔effect〕

As described above, according to the present invention, carbon dioxide gas and water vapor that permeate into the inside of a plastic container can be removed using a silica-alumina adsorbent with a small pore diameter. can be maintained,
It is possible to obtain a vacuum insulation structure having high insulation performance with stable quality over a long period of time.

A cross-sectional view showing Ruru.

1...Plastic container, 2...Insulating spacer material, 3...Organic foam insulation material, 4...Silica-alumina-based adsorbent.

Claims (1)

[Claims] 1. In the plastic container, together with a heat insulating spacer material, a silica-alumina adsorbent is used as a getter material, the pore diameter of which adsorbs is larger than the molecular diameter of carbon dioxide or water vapor and smaller than the molecular diameter of fluorocarbon gas. A vacuum insulation structure characterized in that a vacuum insulation material filled and vacuum-sealed inside the plastic container is embedded in an organic foam insulation material. 2. Cover the plastic container with plastic film.
The vacuum heat insulating structure according to claim 1, characterized in that it is constructed of a laminate film made of metal foil, metal vapor deposited film, etc. 3. As the heat insulating spacer material, an inorganic powder such as perlite or calcium silicate, a fibrous material such as glass wool or ceramic wool, or an organic foam such as foamed polyurethane is used. The vacuum insulation structure according to item 2. 4. Claim 1, 2 or 3, characterized in that a molecular sieve (synthetic zeolite) is used as the silica-alumina adsorbent.
Vacuum insulation structure described in Section 1.