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Title:
VACUUM HEAT INSULATOR, AND REFRIGERATOR, CAR, AND BUILDING USING VACUUM HEAT INSULATOR
Document Type and Number:
WIPO Patent Application WO/2007/041821
Kind Code:
A1
Abstract:
The object of the present invention is to provide a vacuum heat insulator using a core member formed without any binder. The vacuum heat insulator is constructed by enclosing the core material with an enveloping material which is formed by a rigid or flexible plastic sheet, a film to which a metal foil or a metal coating is deposited, or the like. The core material is formed by fiberizing a glass material with a melting centrifugal method, applying water by spraying on glass wool which has just been fiberized, cutting both ends of the glass wool aggregated on a conveyor so as to prepare a glass wool chip, laminating the glass wool chips and compressing so as to form a glass wool mat, and conducting heating press forming to the glass wool mat.

Inventors:
GARNER GRAHAM CLIFFORD (CA)
Application Number:
PCT/CA2005/001533
Publication Date:
April 19, 2007
Filing Date:
October 07, 2005
Export Citation:
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Assignee:
GARNER GRAHAM CLIFFORD (CA)
International Classes:
F16L59/05; C03C13/06; F16L59/02; F16L59/065
Foreign References:
US4726974A1988-02-23
US5826780A1998-10-27
US6938968B22005-09-06
Attorney, Agent or Firm:
MITCHELL, Richard, J. et al. (P.O. Box 957 Station B, Ottawa Ontario K1P 5S7, CA)
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Claims:

CLAIMS

1. A heat insulator comprising: an airtight envelope member defining a reduced pressure space; and a core material filling the reduced pressure space so as to maintain the shape of the envelope member; and wherein the core material comprises a glass wool formed body in which glass wool is bonded together at contact points with sodium silicate.

2. A heat insulator according to claim 1, wherein the glass wool has a density of 150-300 kg/m 3 .

3. A heat insulator according claim 1, wherein said reduced pressure space is maintained in a vacuum.

4. A heat insulator according to any one of claims 1 to 4, wherein the diameter of the glass wool lies in the range 2 - 8 μm.

5. A heat insulator according to any one of claims 1 to 4, wherein glass wool formed body has a density of about 125 kg/m 3 and a thickness of 20mm.

6. A refrigerator comprising an outer pane and an inner panel of a storage portion, and a heat insulator according to any one of claims 1 to 5 interposed therebetween.

7. A roof panel for a car comprising a heat insulator according to any one of claims I to 7.

8. A building comprising a heat insulator according to any one of claims 1 to 5 provided in a wall member, a floor portion, or a roof portion thereof.

9. A method of making a core material for use in heat insulator having an envelope filled with the core material, the method comprising: preparing a glass wool; forming the glass wool into a mat; bringing the glass wool mat into contact with water; eluting sodium hydroxide from the glass wool mat; and

\ - y - reacting the eluted sodium hydroxide with silicon oxide from the glass wool mat to produce sodium silicate that bonds the glass wool mat together at contact points.

10. A method according to claim 9, wherein water is supplied to the glass mat such that the water content of the glass wool mat is 0.1 - 10.0 mass %, and the glass wool mat is press formed while maintaining the temperature between 200 and 500 0 C.

11. A method according to claim 10, wherein the glass wool mat is press formed while maintaining the temperature between 300 and 400 °C.

12. A method according to any one of claims 9 to 11, wherein the glass wool is prepared by fiberizing molten glass material.

13. A method according to any one of claims 9 to 12, wherein the diameter of the glass wool fiber is in the range 2 - 8 μm.

14. A method according to any one of claims 9 to 13, wherein the glass wool mat is heated at about 350 0 C for about 10 minutes.

Description:

DESCRIPTION

VACUUM HEAT INSULATOR, AND REFRIGERATOR, CAR, AND BUILDING USING VACUUM HEAT INSULATOR

Technical Field

The present invention relates to a vacuum heat insulator in which a glass wool formed body is used as a core material, and a refrigerator, a car, and a building in which the vacuum heat insulator is partly installed.

Background Art

Conventionally, a heat insulating board has been used in order to thermally block two spaces. However, the weight of the heat insulating board is too large, and the thickness thereof needs to be increased in order to block heat in an ensured manner.

As shown in FIG. 6, if two spaces are divided with a vacuum wall which does not transmit light, it is theoretically possible to block heat transmission from one space to the other space. However, when the inside of a flat and hollow wall member is vacuumed, the v wall member is deformed, and the left and right wall surfaces stick to each other as shown in

FIG. 7. Consequently, a vacuum space cannot be achieved. The wall member will not be deformed if a case of high strength is used. However, the weight becomes larger, and the cost becomes high.

USP 6,938,968 has proposed a technique. According to this technique, a core material is inserted into an airtight enveloping member, and thereafter the air inside the enveloping member is removed so as to produce a vacuum heat insulator.

According to this prior art material, power consumption can be saved by 15 % or

more by inserting the above-described vacuum heat insulator in a door or a wall of a refrigerator.

In order to obtain a glass wool formed body, a binder is sprayed on glass wool which has just been fiberized, and press forming is performed thereto. An organic binder and an inorganic binder can be used as a binder. An example of the organic binder includes an epoxy resin and an acrylic resin. An example of the inorganic binder includes sodium silicate (liquid glass), boric acid, colloidal silica, or the like.

In manufacturing a vacuum heat insulator, the handling properties (e.g. insertion into an enveloping material) of a glass wool formed body as a core material can be improved by adding a binder. However, the use of a binder requires an additional cost for a binder raw material and an additional process for manufacturing a binder, which increases a capital investment cost and energy consumption causing an increase in a manufacturing cost. Also, as for a vacuum heat insulator, when an organic binder is used, the vacuum level is deteriorated due to its volatile component. When boric acid, which is an inorganic binder, is used, the vacuum level is deteriorated due to the volatilization of bound water, and the heat insulating performance cannot be maintained.

In addition, the binder needs to be placed only in the area where the fibers contact with each other in order to join the glass wool with each other. However, when the binder is sprayed by using a sprayer, the binder will be applied to an unwanted surface of the fibers which does not involve j oining.

Thus, pressure forming may be performed without any binder at a temperature higher than the temperature where glass wool is deformed so as to form an aggregate of glass fibers by plastic deformation. However, when the glass wool is heated at a temperature higher than the temperature where it is deformed, tensile stress of the fiber surface is relieved, and the strength of the fiber is significantly deteriorated, which results in powdering the glass wool. Consequently, it is expected that the handling properties in the manufacturing process and the environmental conditions will be deteriorated. Also, various problems might occur due to scattering of fiber powders when the vacuum heat insulator is recycled.

Disclosure of the Invention

In order to solve the above-mentioned problems, according to the present invention, there is provided a vacuum heat insulator comprising an airtight enveloping member, and a core material which is filled into a reduced pressure space enclosed by the enveloping member so as to maintain the shape, wherein the core material is made of a glass wool formed body in which glass wool is joined with each other by using sodium silicate, and the sodium silicate is produced by reacting sodium hydroxide eluted from the glass wool into water which is added to a surface of the glass wool and silicon oxide which is a component of the glass wool at a heated condition.

The vacuum heat insulator can be incorporated into various products. In a case of a refrigerator, the vacuum heat insulator is interposed between an outer panel and an inner panel of a storage portion. In a case of a car, the vacuum heat insulator is provided in a roof panel on the indoor side. In a case of a building, the vacuum heat insulator is provided in a wall member, a floor portion, or a roof portion.

Brief Description of the Drawings

FIG. 1 is a sectional view of the main part of a refrigerator in which the vacuum heat insulator according to the present invention is used;

FIG. 2 is a sectional view of the vacuum heat insulator according to the present invention;

FIG. 3 is an enlarged view of the core material which constructs the vacuum heat insulator;

FIG. 4 is a sectional view of the main part of a car in which the vacuum heat insulator according to the present invention is used;

FIG. 5 is a sectional view of the main part of a building in which the vacuum heat

insulator according to the present invention is used;

FIG. 6 explains blocking heat by a vacuum wall; and

FIG. 7 explains the drawback of the vacuum wall shown in FIG. 6.

Best Mode for Carrying Out the Invention

Hereinafter, embodiments according to the present invention will be explained with reference to the attached drawings. FIG. 1 is a "sectional view of the main part of a refrigerator in which the vacuum heat insulator according to the present invention is used, FIG. 2 is a sectional view of the vacuum heat insulator according to the present invention, and FIG. 3 is an enlarged view of the core material which constructs the vacuum heat insulator.

A refrigerator 10 has an outer panel 11 and an inner panel 12, and a vacuum heat insulator 1 according to the present invention is interposed between the outer panel 11 and the inner panel 12. Incidentally, another member may be interposed between the outer panel 11 and the inner panel 12 in addition to the vacuum heat insulator 1.

The vacuum heat insulator 1 is constructed by enclosing a core material 3 with an enveloping material 2 which is formed of a rigid or flexible plastic sheet, a film to which a metal foil or a metal coating is deposited, or the like. A preferable example of the core material 3 includes a glass wool formed body having a density of 150 - 300 kg/m 3 . The inside of the enveloping material 2 is maintained to be in- a vacuum state or a highly reduced state by producing the vacuum heat insulator 1 in a reduced atmosphere or reducing the pressure after forming.

An example of the method for forming the core material 3 comprises the steps of fiberizing a glass material by a melting centrifugal method, applying water by spraying on glass wool which has just been fϊberized, cutting both ends of the glass wool aggregated on a conveyor so as to prepare a glass wool chip, laminating the glass wool chips and compressing so as to form a glass wool mat, conducting heating press forming to the glass

wool mat at a temperature of 350 9 C for 10 minutes, and cooling after removing pressure so as to prepare a glass wool formed body. The density of the glass wool formed body is 125 kg/m 3 , and the thickness is 20 mm.

As shown in FIG. 3, glass wool fibers 4 of the core material 3 entwine with each other, and the contact point of the fibers 4 is joined by sodium silicate 5 which is fed from the fibers themselves.

FIG. 4 is a sectional view of the main part of a car in which the vacuum heat insulator according to the present invention is used. In this embodiment, the vacuum heat insulator 1 according to the present invention is provided in a roof panel 21 of a car 20 on the interior side.

FIG. 5 is a sectional view of the main part of a building in which the vacuum heat insulator according to the present invention is used. In this embodiment, the vacuum heat insulator 1 according to the present invention is provided in a wall member 31, a floor portion 32, or a roof portion 33 of a building 30.

The use of the vacuum heat insulator 1 according to the present invention is not limited to the above. The vacuum heat insulator 1 can also be applied to a wall surface of an aircraft, a cool box, a case for a computer, or the like.

A method for producing the core material of the vacuum heat insulator according to the present invention comprises the steps of preparing glass wool by fϊberizing a molten glass material, aggregating the glass wool to be a glass wool mat, supplying water such that the water content of the glass wool mat is 0.1 - 10.0 mass % (preferably 2.0 -5.0 mass %) before press forming of the glass wool mat, and performing the press forming while keeping the temperature at 200 - 500 °C (preferably 300 - 400 0 C). The water supplying step may be performed just after preparing the glass wool or before performing the press forming. Also, the water supplying step may be performed twice just after preparing the glass wool and before performing the press forming.

If the water content of the glass wool mat is less than 0.1 mass %, the amount of the

produced sodium silicate is small, and a good product cannot be obtained. If the water content of the glass wool mat is more than 10.0 mass %, the water moves in the mat so as to be mal-distributed. Consequently, a board-shaped product having a stable quality cannot be obtained, and additional energy is needed to evaporate a great amount of moisture.

As for the heating temperature, the productivity is deteriorated at a temperature less than 200 °C because it takes a lot of time to react the water and the glass wool surface. On the other hand, although the formability is good at a temperature more than 500 °C, the handling properties are deteriorated because the stress of the glass wool is relieved so as to make the board fragile.

The diameter of the glass wool fiber is preferably 2 - 8 μm. If the diameter is less than 2 μm, the energy consumption rate required for fiberization is too much. If the diameter exceeds 8 μm, the thermal conductivity is deteriorated, and thereby the heat insulating performance becomes poor.

The mechanism of the present invention can be explained as follows:

When water comes into contact with a surface of the glass wool, sodium oxide is eluted from the glass wool. The eluted sodium oxide is dissolved into the surrounding water so as to produce sodium hydroxide. The sodium hydroxide is easily reacted with silicon oxide which is a main component of the glass wool so as to produce sodium silicate. The sodium silicate is liquid glass which is well-known as an inorganic binder. By allowing part of the glass wool itself to serve as a binder, the fibers can be joined with each other without any binder. Consequently, the glass wool formed body as a core material can maintain its shape for a long period of time.

According to the present invention, since the glass wool formed body as a core material is formed by joining the fibers without any binder, good handling properties can be achieved. Also, when it is used as a core material of a vacuum heat insulator, the vacuum level can be maintained because gas is not generated, which will be generated from a binder in a case of using a binder.

Industrial Applicability

As is explained in the above, since the vacuum heat insulator according to the present invention has good heat insulating properties, sound insulating properties, sound absorbing properties and shape-maintaining properties, it is possible to widely utilize it as a heat insulator for a freezer, a heat insulator for a building, a heat insulator for a car, or the like.