JPH09303676A - Vacuum heat insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To light weight, reduce cost, improve performance, and recycle urethane foam by using powder granulated by highmolecular coagulant organic powder, in a vacuum heat insulator filled core material formed of at least organic powder and inorganic powder in an outer covered material. SOLUTION: A vacuum heat insulator 1 used as the heat insulating material such as a refrigerator is manufactured in such a way that pressure is reduced and exhaust is carried out so as to suppress pressure of an inner part to about 0.1mmHg after a core material formed by mixing urethane powder granulated by highmolecular coagulant and wet silica powder with each other is filled in an outer covered material. In this case, ethyl cellulose is used as the highmolecular coagulant, the adding rate of the ethyl cellulose is set to be within 1weight% or more to 30weight% and less. Granulation is carried out by the highmolecular coagulant, and thereby, the particle diameter of organic powder is regulated optionally. It is thus possible to reduce a solid heat conductivity by contact of excessive small diameter particle, and it is also possible to reduce a heat conductivity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vacuum heat insulator which can be used as a heat insulator for a refrigerator or the like.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protecting the global environment, ozone layer depletion by CFC11 used as a foaming agent for a heat insulating material of a refrigerator has been attracting attention on a global scale.

From such a background, a heat insulating material using a new foaming agent has been studied, and HCFC is used as an alternative CFC.
141b, cyclopentane and the like are being selected as candidates in the non-fluorocarbon system.

However, each of these new foaming agents has a gas thermal conductivity higher than that of CFC11, and the insulation performance of the refrigerator is unavoidably deteriorated. On the other hand, energy saving of refrigerators is an unavoidable problem with respect to future energy regulations, and improving the heat insulation performance is a major issue to be achieved.

[0005] As described above, the current refrigerator has the contradictory issues of lowering the heat insulation performance due to the use of CFCs and improving the heat insulation performance to achieve energy saving.

As one means for solving such conflicting problems, a vacuum heat insulator using inorganic powder has been devised, and the contents thereof are described in Japanese Patent Application Laid-Open No. 57-173689.
The content is that a film-shaped plastic container is filled with powder having a single particle diameter of 1 μm or less, and the inside thereof is depressurized and then sealed to obtain a vacuum insulator.

The effect is 0.1 to 1 m, which is easy to industrialize.
It can be manufactured at a vacuum degree of mHg, and since the silica particles are fine powder, it has been found that, when the vacuum degree is the same, the heat insulating performance of the vacuum heat insulator is further improved.

[0008]

The adiabatic principle of a vacuum insulation is to eliminate the heat-conducting air. However, it is practically achievable, but the degree of vacuum is 0.1-10 mmHg
It is. Therefore, the desired heat insulation performance must be obtained at this degree of vacuum.

Mean free path is a physical property that affects the heat insulation performance when heat conduction is performed by the presence of air. The mean free path is the distance traveled by one of the molecules that make up the air until it collides with another molecule.If the formed void is larger than the mean free path, the molecules collide with each other in the void. Since heat conduction occurs due to air, the heat conductivity of the vacuum heat insulator increases. On the contrary, when the air gap is smaller than the mean free path, the heat conduction of the vacuum heat insulator becomes small. This is because there is almost no heat conduction due to the collision of air.

Therefore, if a powder having a fine particle size such as a silica powder is used, the gap becomes small, and heat conduction due to the collision of air is almost eliminated. As a result, the heat insulation performance of the vacuum heat insulator is improved. However, since the silica powder is used in the conventional structure, the vacuum heat insulator has a heavy weight and a high cost.

On the other hand, there is a waste problem as a new issue in the global environment problem. The issue of waste disposal is no exception for home appliances such as refrigerators, and how to recycle is a major issue. In particular, the rigid urethane foam used as a heat insulating material for refrigerators has been difficult to recycle because of its special material.

In view of the above, the present invention intends to reduce the weight, cost and performance of the powder vacuum heat insulator, and to recycle urethane foam.

[0013]

In order to solve the above-mentioned problems, a vacuum heat insulator of the present invention is a vacuum heat insulator in which a core material made of at least an organic powder and an inorganic powder is filled in an outer covering material,
As the organic powder, a powder granulated with a polymer coagulant is used. Therefore, since the particle size can be arbitrarily adjusted by granulation, it is easy to reduce the thermal conductivity, and since the polymer coagulant is used, the cohesive force of the granulated product is strong and the cohesive morphology collapses after granulation. there is no problem.

Further, the vacuum heat insulator of the present invention uses ethyl cellulose as a polymer flocculant. Since ethyl cellulose does not generate gas as compared with other polymer flocculants, the problem that the degree of vacuum is deteriorated and the thermal conductivity is increased due to gas generation after granulation is solved.

In the vacuum heat insulator of the present invention, the amount of ethyl cellulose added is limited to 1% by weight or more and 30% by weight or less. When a polymer flocculant such as ethyl cellulose is used, the granulation strength varies depending on the amount added, and if the amount added is too small, the granulated product will collapse due to external impact, etc.If the amount added is too large, the entire powder will become a lump. Will end up. Since the addition amount is limited in the present invention, the addition amount of ethyl cellulose in the granulation is optimized, and the above problems are solved.

Further, the heat-insulating box body of the present invention is the heat-insulating box body in which a space formed by the outer box, the inner box, the outer box and the inner box is filled with a foam insulation material, and the inner surface of the outer box or the inner box. In addition, a vacuum heat insulating body is provided in which an outer coating material is filled with at least an organic powder granulated with a polymer coagulant and a core material made of an inorganic powder.

Therefore, the particle size of the organic powder can be adjusted arbitrarily, and the thermal conductivity changes even when the degree of vacuum approaches atmospheric pressure by shortening the gap distance formed by the powder. Is small. Therefore, when applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even if it is used for a long time.

As a result, the operating rate of the compressor becomes excessive due to the rapid deterioration of the thermal conductivity of the vacuum heat insulator.
The problem that the reliability of the refrigerator is reduced is solved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The invention described in claim 1 of the present invention uses an organic powder granulated with a polymer flocculant as the organic powder. Since the organic powder is produced by granulation, the particle size can be adjusted as desired, and the thermal conductivity can be easily reduced due to the reduction of the contact area between the powders. Further, a polymer coagulant is used as the coagulant. An electrolyte such as an inorganic salt generally uses a surfactant as a coagulant, but these have a weak cohesive force and the granulated product is easily broken due to external obstacles.

The present invention has found that a polymer coagulant is the most suitable as a result of various investigations so as to enhance the cohesive force and apply it to a vacuum heat insulator. By applying a polymer coagulant as the coagulant, the coagulation mechanism is fundamentally different from conventional electrolytes and surfactants, and polymer coagulation is formed, so that the cohesive force is remarkably improved.

According to the second aspect of the present invention, ethyl cellulose is applied as the polymer flocculant.
When a polymer coagulant is applied, gas generation after granulation becomes a problem.

Generally, polyamine, polyacrylamide, polyacrylic acid and the like are applied. However, although all of them have high cohesive force, gas generation is remarkable in a reduced pressure atmosphere. In the present invention, in view of such problems,
The inventors have found that ethyl cellulose is excellent as a polymer flocculant that does not generate gas in a reduced pressure atmosphere and has a high cohesive force. This is probably because ethyl cellulose itself has low hygroscopicity.

According to the third aspect of the present invention, the amount of ethyl cellulose used as the polymer flocculant is limited to 1% by weight or more and 30% by weight or less. When a polymer coagulant is applied, it is very important to determine the amount added, and if the amount added is too small, a normal granulated product cannot be obtained, and if it is too large, it becomes a paste.

In view of the above problems, the present invention has found that an optimum floc granulated product can be obtained by adding ethyl cellulose in an amount of 1% by weight or more and 30% by weight or less.

On the other hand, the heat-insulating box body according to claim 4 of the present invention is the heat-insulating box body in which a foam insulation material is filled in a space formed by the outer box, the inner box, the outer box and the inner box. The inner surface of the box or the inner box is provided with a vacuum heat insulator in which a core material made of granulated organic powder and inorganic powder is filled in an outer covering material.

Therefore, the particle size of the organic powder can be adjusted arbitrarily, and the gap distance formed by the powder can be shortened. As a result, the change in thermal conductivity is small even when the degree of vacuum approaches atmospheric pressure. Therefore, when applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even if it is used for a long time.

As a result, the operating rate of the compressor becomes excessive due to the rapid deterioration of the thermal conductivity of the vacuum heat insulator,
The problem that the reliability of the refrigerator is reduced is solved.

An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) In FIG. 1, reference numeral 1 denotes a vacuum heat insulator, and a core material 2 obtained by mixing urethane powder having a particle size of 200 μm granulated with a polymer coagulant and wet silica powder (average particle size 5 μm). It was obtained by filling the outer covering material 3 made of a metal-plastic laminated film and then evacuating it under reduced pressure so that the inside became 0.1 mmHg.

In the case of the powder vacuum heat insulating material, the gap distance formed by agglomeration and entanglement of the powder particles is small. Since the degree of vacuum in the production of the vacuum heat insulator is 0.1 mmHg, most of the void distance of the powder is shorter than the mean free path of gas molecules, and therefore the contribution of gas thermal conductivity is small. Therefore, how to reduce the solid thermal conductivity is important.

In the present invention, the particle size of the organic powder can be arbitrarily adjusted because the particles are granulated by the polymer coagulant, and the solid thermal conductivity due to the contact of the excessively small particles can be reduced. Therefore, the thermal conductivity of the vacuum heat insulator can be reduced. Also, because a polymer flocculant is applied,
The aggregation mechanism is fundamentally different from that of conventional electrolytes and surfactants, and because it forms polymer crosslinks, it has a strong aggregation force. As a result, it becomes possible to endure atmospheric compression, and the problem that the granulated product collapses when the vacuum heat insulator is applied is solved.

(Embodiment 2) Ethyl cellulose is applied as a polymer flocculant used for the core material 2. When a polymer crosslinking agent is applied, gas generation after granulation becomes a problem.

Generally, polyamine, polyacrylamide, polyacrylic acid, etc. are applied. However, although the cohesive force is high in all of these, gas generation is remarkable in a reduced pressure atmosphere. In view of such a problem, the present invention has found that ethyl cellulose is excellent as a polymer flocculant having no gas generation in a reduced pressure atmosphere and having a strong cohesive force. When ethyl cellulose is applied, the cause of less gas generation is not clearly known, but it is considered that ethyl cellulose itself has low hygroscopicity.

(Embodiment 3) The amount of ethyl cellulose used for the polymer flocculant of the core material 2 is limited to 1% by weight or more and 30% by weight or less. When applying a polymer flocculant, it is very important to determine the amount added, and if the amount added is too small, it will not be possible to obtain a normal granulated product. I will end up.

In view of the above problems, the present invention has found that an optimum floc-like granulated product can be obtained by adding ethyl cellulose in an amount of 1% by weight or more and 30% by weight or less.

(Embodiment 4) In FIG. 4, reference numeral 4 denotes a heat insulating box body constituted by a vacuum heat insulating body 1, a foam insulating material 5 made of hard foam urethane foam, an outer case 6 and an inner case 7. The vacuum heat insulator 1 is attached to the inner surface of the outer box 6, but may be the inner surface of the inner box 7. Also, the vacuum insulator 1
Has a size of 0.5 m × 0.5 m × 0.02 m.

Since the organic powder of the vacuum heat insulator 1 is a granulated product, the particle size of the organic powder can be adjusted arbitrarily.
The void distance formed by the powder can be shortened. As a result, the change in thermal conductivity is small even when the degree of vacuum approaches atmospheric pressure.

Therefore, when applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even if it is used for a long time. As a result, the problem that the operating rate of the compressor becomes excessive due to the rapid deterioration of the thermal conductivity of the vacuum insulator and the reliability of the refrigerator is reduced is solved.

[0038]

【Example】

(Example 1) (Table 1) shows, as an example, what was granulated using a polymer flocculant, and as a comparative example, an electrolyte substance, a surfactant, and a non-granulated product as coagulants. It is an evaluation result about the high density, the thermal conductivity of the vacuum heat insulator, and the disintegration property of the granulated product under atmospheric compression.

The thermal conductivity is AUT manufactured by Eiko Seiki Co., Ltd.
The measurement was performed at an average temperature of 24 ° C. by using a thermal conductivity measuring device of O-Λ HC-07. Further, in order to remove influences other than the aggregating agent, urethane powder having an average particle diameter of 200 μm was used as the organic powder.

The granulation was carried out by wet granulation, the solvent used was a mixture of toluene and ethyl alcohol at a ratio of 80:20, and the coagulant was added in an amount of 15% by weight. Wet silica powder having an average particle size of 5 μm was used as the inorganic powder, and 5% by weight was added for surface modification. The core material thus obtained is filled in an outer covering material and the inside is filled with 0.1
The pressure was reduced to a vacuum degree of mmHg to produce a vacuum heat insulator.

[0041]

[Table 1]

From Table 1, this example shows the lowest thermal conductivity. It is considered that this is because the particle size is increased due to the granulation, so that the density of the powder is reduced, and as a result, the contact area between the powders is reduced and the solid thermal conductivity is reduced.

Comparing the comparative example with this example, the high density is halved in comparison with the non-granulated product.

However, in each of the comparative examples, the granulated product collapsed due to atmospheric compression. As a result, it is considered that the density became higher and the thermal conductivity became higher when the vacuum heat insulator was completed.

From the above, by granulating with the polymer flocculant of the present invention, the particle size of the organic powder can be arbitrarily adjusted. Therefore, it is possible to reduce the solid thermal conductivity due to the contact of excessive small-diameter particles, and it is possible to reduce the thermal conductivity of the vacuum heat insulator.

Since a polymer flocculant is applied,
The aggregation mechanism is fundamentally different from that of conventional electrolytes and surfactants, and because it forms polymer crosslinks, it has a strong aggregation force. As a result, it becomes possible to endure atmospheric compression, and the problem that the granulated product collapses when the vacuum heat insulator is applied is solved.

(Example 2) Table 2 shows the degree of vacuum in the vacuum heat insulator when ethyl cellulose was used in Examples as a polymer flocculant for organic powder and polyamine, polyacrylamide and polyacrylic acid were used in Comparative Examples. It is the result of evaluating the change over time.

In order to eliminate influences other than the polymer flocculant, urethane powder having an average particle diameter of 200 μm was used as the organic powder. The granulation was carried out by wet granulation, the solvent used was a mixture of toluene and ethyl alcohol in a ratio of 80:20, and the coagulant was added in an amount of 15% by weight.

As the inorganic powder, a formula wet silica powder having an average particle size of 5 μm was used, and 5% by weight was added for surface modification. The core material thus obtained was filled in an outer covering material, and the inside was depressurized to a vacuum degree of 0.1 mmHg to produce a vacuum heat insulator.

The vacuum heat insulator thus obtained is
The sample was left in a room at ℃ and the vacuum degree of the vacuum heat insulator was measured by the differential pressure method.

[0051]

[Table 2]

From the results of (Table 2), it can be seen that no change in the degree of vacuum was observed and no gas was generated in this example. On the other hand, in the comparative examples polyamine, polyacrylamide and polyacrylic acid, the degree of vacuum changes drastically with time, and gas is generated from the polymer coagulant. As a result of analyzing the generated gas of the vacuum heat insulating material in the comparative example, it was found that most of it was water.

As described above, by using the ethyl cellulose of the present invention as a coagulant, it is possible to maintain the degree of vacuum for a long time without generating gas such as water inside the vacuum heat insulator.

(Example 3) Table 3 shows the amount of ethyl cellulose as a polymer coagulant, the high density, the granulated product shape, and the thermal conductivity evaluation results. As an example, the addition amount of ethyl cellulose was 0.1, 10, 20,
Four kinds of 30% by weight, and 0, 0.05 as a comparative example,
40 and 60% by weight were used. Granulation is performed by wet granulation, and toluene and ethyl alcohol are used as solvents.
A mixture of 0 to 20 was used. In order to eliminate effects other than the addition amount of ethyl cellulose, urethane powder having an average particle size of 200 μm is used as the organic powder, wet silica powder having an average particle size of 5 μm is used as the inorganic powder, and 5% by weight is added to the surface. It was modified.

The density of the core material thus obtained was measured, and then the shape was observed with an electron microscope. Also,
The thermal conductivity was measured by filling the outer material with a core material
The pressure was reduced to a vacuum degree of mmHg to produce a vacuum heat insulator, and the heat conductivity was measured at an average temperature of 24 ° C. using a thermal conductivity measuring device of AUTO-ΛHC-07 manufactured by Eiko Seiki Co., Ltd.

[0056]

[Table 3]

From the results of (Table 3), all the floc powders were obtained with the addition amount in this example, and the high density was also very low. As a result, it is considered that the solid thermal conductivity is reduced due to the decrease in the contact area between the powders, and the thermal conductivity as the vacuum heat insulator is also reduced. On the other hand, when looking at Comparative Examples, the granulated product was in a paste form at all addition amounts, which was caused by the addition amount of ethyl cellulose being too large. As a result, it is considered that the high density increases the contact area between the powders and the solid thermal conductivity increases, which increases the thermal conductivity of the vacuum heat insulator.

From the above, in the present invention, since the amount of ethyl cellulose added is limited to 1% by weight or more and 30% by weight or less, a good floc-like granulated product can be obtained, and the solid thermal conductivity is reduced, so that the vacuum heat insulator The thermal conductivity of can be reduced.

(Embodiment 4) Next, regarding the heat insulating box, since the organic powder of the vacuum heat insulating body 1 is a granulated product, it is possible to arbitrarily adjust the particle size of the organic powder, and it is formed by the powder. It is possible to shorten the air gap distance. As a result,
Even when the degree of vacuum approaches atmospheric pressure, the change in thermal conductivity is small.

Therefore, when applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even if it is used for a long time. As a result, the problem that the reliability of the refrigerator is lowered due to the excessive operating rate of the compressor due to the rapid deterioration of the heat insulation rate of the vacuum heat insulator is solved.

[0061]

As described above, the vacuum heat insulator of the present invention is
In a vacuum heat insulator in which a core material made of at least an organic powder and an inorganic powder is filled in a jacket material, a powder granulated with a polymer coagulant is used as the organic powder. Therefore, since the particle size can be arbitrarily adjusted by granulation, it is easy to reduce the thermal conductivity, and since the polymer coagulant is used, the cohesive force of the granulated product is strong and the cohesive morphology collapses after granulation. there is no problem.

Further, the vacuum heat insulator of the present invention uses ethyl cellulose as a polymer flocculant. Since ethyl cellulose does not generate gas as compared with other polymer flocculants, the problem that the degree of vacuum is deteriorated and the thermal conductivity is increased due to gas generation after granulation is solved.

In the vacuum heat insulator of the present invention, the amount of ethyl cellulose added is limited to 1% by weight or more and 30% by weight or less. When a polymer flocculant such as ethyl cellulose is used, the granulation strength varies depending on the amount added, and if the amount added is too small, the granulated product will collapse due to external impact, etc.If the amount added is too large, the entire powder will become a lump. Will end up. Since the addition amount is limited in the present invention, the addition amount of ethyl cellulose in the granulation is optimized, and the above problems are solved.

The heat-insulating box body of the present invention is a heat-insulating box body in which a space formed by the outer box, the inner box, the outer box and the inner box is filled with a foam insulation material. The inner surface is provided with a vacuum heat insulating material in which an outer coating material is filled with at least an organic powder granulated with a polymer coagulant and a core material made of an inorganic powder.

Therefore, the particle diameter of the organic powder can be adjusted arbitrarily, and the thermal conductivity changes even when the degree of vacuum approaches atmospheric pressure by shortening the gap distance formed by the powder. Is small. Therefore, when applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even if it is used for a long time.

As a result, the operating rate of the compressor becomes excessive due to the rapid deterioration of the thermal conductivity of the vacuum insulator,
The problem that the reliability of the refrigerator is reduced is solved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a vacuum insulator according to an embodiment of the present invention.

FIG. 2 is a sectional view of a heat insulating box according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum heat insulator 2 Core material 3 Jacket material

Claims (4)

[Claims] 1. A vacuum heat insulator in which a core material made of at least an organic powder and an inorganic powder is filled in a jacket material, wherein the organic powder is a powder granulated with a polymer coagulant. 2. The vacuum heat insulator according to claim 1, wherein the polymer flocculant is ethyl cellulose. 3. Ethyl cellulose is used as a polymer flocculant, and the addition amount of said ethyl cellulose is 1% by weight or more and 3
The vacuum heat insulator according to claim 1, which is 0% by weight or less. 4. A heat-insulating box body having an outer box, an inner box, a space formed by the outer box and the inner box filled with a foaming heat insulating material, the inner box of the outer box or the inner box being made of a polymer coagulant. A heat insulation box body provided with a vacuum heat insulation body in which a core material made of granulated organic powder and inorganic powder is filled in an outer covering material.