Stock material or miscellaneous articles – Sheet including cover or casing – Filled with gas other than air; or under vacuum
Patent
1997-06-12
1999-02-02
Thomas, Alexander
Stock material or miscellaneous articles
Sheet including cover or casing
Filled with gas other than air; or under vacuum
428 76, B32B 106
Patent
active
058662286
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a vacuum heat-insulator, and more in particular, it relates to a vacuum heat-insulator improved so as to display an excellent heat-insulating performance by using a specified calcium silicate shaped product as a heat-insulating core material.
BACKGROUND ART
Freon-polyurethane foam heat-insulator utilizes low heat conductivity of Freon and has been used generally as an excellent heat-insulator. Since the use of Freon has been restricted in recent years, a heat-insulator capable of exhibiting an excellent heat-insulating performance without using Freon has been demanded.
The preparation of a heat-insulator has recently been provided, prepared by incorporating fine inorganic particles such as silica powder as a heat-insulating core material into a flexible container (bag) having gas barrier property, then evacuating the inside of the container to a reduced pressure state, thereby closely adhering the fine inorganic particles to the container, and sealing the container.
For example, in the case where such a vacuum heat-insulator is used in a refrigerator or device for cool storage or for cold preserving storage, it is preferred that the thermal conductivity at 20.degree. C. of the vacuum heat-insulator be 0.005 to 0.008 Kcal/m.multidot.hr.multidot..degree.C. When the thermal conductivity is more than 0.008 Kcal/m.multidot.hr.multidot..degree.C., excess electric power and current is required for maintaining the cold storage temperature. If a vacuum heat-insulator having a larger thermal conductivity is used, a much more thicker heat-insulator must necessarily be used, undesirably reducing the size of the storage area.
However, the vacuum heat-insulator described above involves a problem of emitting powdery dusts upon discarding to bring about an environmental problem. The present invention has been accomplished in view of the foregoing situations and an object thereof is to provide a novel vacuum heat-insulator bringing about no environmental problem caused by dusting upon discarding and capable of exhibiting an excellent heat-insulating performance without using Froen, as well as a method of preparing the same .
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory cross sectional view illustrating an example of a vacuum heat-insulator according to the present invention;
FIG. 2 is an explanatory cross sectional view illustrating another example of a vacuum heat insulator according to the present invention;
FIG. 3 is an explanatory cross sectional view illustrating an example of a method of preparing a vacuum heat insulator according to the present invention, in which are shown a calcium silicate shaped product (1), a plastic film layer (2) constituting a container, a metal layer (3) constituting the container, a plastic film layer (4) constituting the container, a sealed portion (5) of the container, a vacuum insulator (6), a polyurethane foam molded product (7), an inner wall (8) and an outer wall (9);
FIG. 4 shows a photograph at 1,000.times.magnification of calcium silicate crystals obtained in Example 1;
DISCLOSURE OF THE INVENTION
For attaining the foregoing object, while studying the performance of the vacuum heat-insulator, it was discovered that selection of a heat-insulating core material enabling easy evacuation and capable of attaining highly reduced pressure state is essential. Then, as a result of a further study on the basis of such a finding, it has been discovered that a specified calcium silicate shaped product among inorganic shaped products, is excellent as the heat-insulating core material and the present invention has been accomplished.
The present invention has been accomplished on the basis of the above-mentioned finding, and in accordance with a first aspect of the present invention, there is provided a vacuum heat-insulator formed by tightly packaging a shaped product comprising acicular crystals of calcium silicate entangled in a three dimensional manner in a reduced pressure state in a container composed of a composite f
REFERENCES:
patent: 4162924 (1979-07-01), Kubo et al.
patent: 4269323 (1981-05-01), Ito et al.
patent: 4492725 (1985-01-01), Ishihara et al.
patent: 4529638 (1985-07-01), Yamamoto et al.
patent: 4669632 (1987-06-01), Kawasaki et al.
Mitsubishi Chemical Corporation
Thomas Alexander
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