JPH09303945A - Vacuum heat insulating member and heat insulating box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a light weight, low cost and high performance member by a method wherein a core material composed of an organic powder and a non-organic powder is filled in an outer cover member and a particle size distribution of a specified particle diameter in the organic powder filled in it is set to a specified volumetric rate. SOLUTION: After a core material attained by mixing an organic powder having a particle size distribution of 10% or more to 30% or less of volumetric ratio less than particle diameter of 200μm or less with a wet type silica powder is filled in an outer cover member 3 formed by a metal-plastic laminated film, its inner side is reduced in pressure to have a pressure value of 0.1μmHg and discharged so as to attain a vacuum heat insulating member. The vacuum heat insulating material in this way is made such that contact areas of powders themselves are reduced, resulting in that a solid thermal conductivity can be reduced, even if the material is used in a refrigerator for a long period of time, a rapid deterioration of the thermal conductivity of the vacuum heat insulating member is not produced and a high performance of the device can be attained.

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, research on a heat insulating agent using a new foaming agent has been conducted, 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. As described above, the current refrigerators have the contradictory problems of lowering heat insulation performance due to CFC compatibility and improving heat insulation performance to achieve energy saving.

As a means for solving such conflicting problems, a vacuum heat insulator using an inorganic powder has been devised, and the contents thereof are described in JP-A-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.

[0007]

The adiabatic principle of a vacuum insulation is to eliminate the heat-conducting air. However, the practical degree of vacuum is 0.1 to 10 mmHg. 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, when a powder having a fine particle diameter such as silica powder is used, the voids become fine and the 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 problem 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, rigid urethane foam used as a heat insulating material for refrigerators has been difficult to recycle due to its material properties.

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

[0012]

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,
The particle size distribution of the organic powder having a particle size of 200 μm or less is limited to 10% or more and 30% or less by volume ratio.

Therefore, the solid thermal conductivity can be reduced, and a vacuum heat insulator having excellent heat insulating performance can be obtained.

The vacuum heat insulator of the present invention has a particle size of 200.
20% or more by volume ratio of particle size distribution in μm or less 20
% Of the organic powder and the inorganic powder, and the aspect ratio of the organic powder is limited to 2 or more and 3 or less. Therefore, the steric hindrance effect of the organic powder is enhanced, and the thermal conductivity can be reduced by reducing the density.

Further, the vacuum heat insulator of the present invention uses hard urethane foam powder as the organic powder. Therefore, it becomes possible to recycle the rigid urethane foam used as the heat insulating material of the refrigerator and solve the waste problem. Also, since the organic powder is a hard urethane foam, the resin thermal conductivity of the organic powder is low,
When applied to a vacuum heat insulator, the thermal conductivity can be reduced.

In the vacuum heat insulator of the present invention, silica powder which has been subjected to a grinding treatment is applied as the inorganic powder material. Since the surface roughness of the silica powder is improved by the grinding treatment,
In the surface modification action by mixing with the organic powder,
The contact area between the powders can be reduced, and the solid thermal conductivity can be reduced.

Further, 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 foamed heat insulating material. On the inner surface, a particle size distribution of less than 200 μm in volume ratio is 10
A vacuum heat insulating body is provided in which a core material made of an organic powder and an inorganic powder of not less than 30% and not more than 30% is filled in an outer covering material.

Therefore, since the vacuum heat insulator according to the present invention has a short air gap distance formed by the powder, the change of the thermal conductivity is small even when the degree of vacuum becomes close to the atmospheric pressure. In this case, even if it is used for a long time, the thermal conductivity of the vacuum heat insulator does not suddenly deteriorate.

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.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 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 a jacket material, and the particle diameter of the organic powder is 200 μm or less. The particle size distribution is limited to 10% to 30% by volume.

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 vacuum degree 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 the gas molecules, so that the contribution of the gas thermal conductivity is small. Therefore, how to reduce the solid thermal conductivity is important.

In the present invention, the particle size is taken as the cause of contact between the powders and the honey, and the relationship between the volume ratio and the thermal conductivity in the particle size of 200 μm or less was evaluated. As a result, they have found that the volume ratio in the particle size of 200 μm or less needs to be 10% or more and 30% or less in order to reduce the thermal conductivity.

The invention according to claim 2 of the present invention limits the actpest ratio of the organic powder used for the vacuum heat insulator to 2 or more and 3 or less. In general, spherical powders have a dense packing form, which leads to an increase in density and an increase in solid thermal conductivity. Therefore, it is important to quantitatively limit the powder shape.

In the present invention, the Acupest ratio is taken as a quantitative index, and it has been found that the thermal conductivity can be reduced by setting the aspect ratio to 2 or more and 3 or less. By setting the Axpest ratio to 2 or more and 3 or less, the steric hindrance effect of the powder becomes large, and the packing form of the powders changes from the close packing, so that the density can be reduced, and as a result, the thermal conductivity can be reduced.

According to the third aspect of the present invention, a hard urethane foam powder is used as the organic powder. Therefore, it becomes possible to recycle the rigid urethane foam used as the heat insulating material of the refrigerator and solve the waste problem. Moreover, since the organic powder is a hard urethane foam, the resin thermal conductivity of the organic powder is low, and the thermal conductivity can be reduced when applied to a vacuum heat insulator. This is because the urethane bond has a double bond, so that the thermal vibration energy is high, and as a result, the solid thermal conductivity is reduced.

The invention according to claim 4 of the present invention is
As the inorganic powder material used for the vacuum heat insulator, silica powder subjected to grinding treatment is applied. Although silica powder is generally spherical, a new surface appears because the silica powder is crushed by the grinding treatment, and the surface becomes extremely uneven. Since this uses a grinding method such as a ball mill,
This is because the collision energy when pulverizing the silica powder is large. As a result, it becomes possible to reduce the contact area between the powders by the surface modification action mixed with the organic powder, and to reduce the solid thermal conductivity.

On the other hand, the heat-insulating box body according to claim 5 of the present invention is the heat-insulating box body in which the space formed by the outer box, the inner box, the outer box and the inner box is filled with foamed heat insulating material. On the inner surface of the box or the inner box, a vacuum heat insulator having a core material made of organic powder and inorganic powder having a particle size distribution of 200 μm or less in a volume ratio of 10% or more and 30% or less is provided.

Therefore, since the vacuum insulating body has a short air gap distance, the change in thermal conductivity is small even when the degree of vacuum approaches atmospheric pressure. Therefore, when it is applied to a refrigerator, it is used for a long time. Even if it does, the thermal conductivity of the vacuum insulator does not suddenly deteriorate.

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, which is a mixture of organic powder having a particle size distribution of 10% or more and 30% or less with a particle size of 200 μm or less and wet silica powder (average particle size 5 μm). The core material 2 obtained as described above is filled in an outer covering material 3 made of a metal-plastic laminate film, and then vacuum-exhausted so that the inside becomes 0.1 mmHg.

In the case of the powder vacuum heat insulator, the gap distance formed by the agglomeration and entanglement of the powder particles is small. Since the vacuum degree 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 the gas molecules, so the contribution of the gas thermal conductivity is small. Therefore, it is important to reduce the solid thermal conductivity.

In the present invention, the particle size is taken up as the cause of the powder particles coming into close contact with each other, and the relationship between the volume ratio and the thermal conductivity in the particle size of 200 μm or less was evaluated. As a result, they have found that the volume ratio in the particle size of 200 μm or less needs to be 10% or more and 30% or less in order to reduce the thermal conductivity.

In the vacuum heat insulator thus obtained, the volume ratio of particles having a particle size of 200 μm or less is 10% or more and 30% or less, so that the contact area between the powder particles is reduced, and as a result, the solid thermal conductivity is reduced. It is possible to achieve high performance.

(Embodiment 2) The aspect ratio of the organic powder used for the core material 2 is limited to 2 or more and 3 or less. In general, spherical powders have a finely packed form and thus have a high density, leading to an increase in solid thermal conductivity. Therefore, it is important to quantitatively limit the powder shape.

In the present invention, the aspect ratio is taken as a quantitative index, and it has been found that the thermal conductivity can be reduced by setting the aspect ratio to 2 or more and 3 or less.

By setting the aspect ratio to 2 or more and 3 or less, the steric hindrance effect of the powder becomes large, and the packing form of the powders changes from fine packing, so that the density can be reduced, and as a result, the thermal conductivity body can be reduced.

(Embodiment 3) Hard urethane foam powder is used as the organic powder for the core material 2. Therefore, it becomes possible to recycle the rigid urethane foam used as the heat insulating material of the refrigerator and solve the waste problem.

Further, since the organic powder is a hard urethane foam, the resin thermal conductivity of the organic powder is low, and the thermal conductivity can be reduced when applied to a vacuum heat insulator. This is because the urethane bond has a double bond, so that the thermal vibration energy is high, and as a result, the solid thermal conductivity is reduced.

(Embodiment 4) As the inorganic powder used for the core material 2, silica powder subjected to grinding treatment is applied. Although silica powder is generally spherical, a new surface appears because the silica powder is crushed by the grinding treatment, and the surface becomes extremely uneven.

This is because the collision energy when pulverizing the silica powder is large because a grinding method such as a ball mill is used.

As a result, it becomes possible to reduce the contact area between the powders in the surface modification action by mixing with the organic powder, and to reduce the solid thermal conductivity.

(Embodiment 5) In FIG. 4, reference numeral 4 denotes a heat insulating box body constituted by a vacuum heat insulating material 1, a foam heat insulating material 5 made of hard urethane foam, an outer case 6 and an inner case 7. The vacuum heat insulating material 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.

In the heat insulating box having the above-described structure, since the gap distance formed by the powder is short, the change in thermal conductivity is small even when the degree of vacuum approaches atmospheric pressure. When applied to a refrigerator, the vacuum thermal insulator does not suddenly deteriorate in thermal conductivity even after being 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 thermal conductivity of the vacuum heat insulator is solved.

[0044]

【Example】

(Example 1) FIG. 3 shows the relationship between the thermal conductivity and the volume ratio of 200 μm or less in particle diameter, using urethane powder as the organic powder. In order to make the other conditions the same, wet silica powder (particle size 5 μm) is used as the inorganic powder,
The amount added was 5% by weight.

[0045]

FIG. 3 (FIG. 3) shows that there is a correlation between the volume ratio of particles having a particle size of 200 μm or less and the thermal conductivity of the vacuum heat insulator, and the thermal conductivity changes with the volume ratio of 20% as the minimum point. I understand. This is because the thermal conductivity of the vacuum insulator is clearly 2
It is shown that the volume ratio of 00 μm or less is affected, which supports the validity of the present invention.

In general, when a hard urethane foam as a heat insulating material and a vacuum heat insulating material are used in multiple layers, the heat conductivity of the vacuum heat insulating material is 0.0050 kcal / because the heat conductivity of the hard urethane foam is large. Those of mh ° C. or lower are required. Considering this situation, the particle size is 2
It is necessary to set the volume ratio of 00 μm or less to 10% or more and 30% or less.

When the volume ratio of particles having a particle diameter of 200 μm or less is 20% or less, the thermal conductivity of the vacuum heat insulating material increases. This is because the relative proportion of coarse particles is increased by decreasing the proportion of small-diameter particles, and as a result, there are more voids longer than the mean free path of air at a vacuum degree of 0.1 mmHg, increasing the gas thermal conductivity. Causes the thermal conductivity to deteriorate.

On the other hand, the volume ratio of particles having a particle size of 200 μm or less is 2
When the content is 0% or more, the number of contact points between the powders increases due to the increase in the small-diameter particles, and as a result, the solid thermal conductivity increases and the thermal conductivity deteriorates. Therefore, the particle size is 200 μm
It is important to limit the volume ratio below, and the volume ratio of the particle size of 200 μm or less is 10% to 30% as in the present invention.
A vacuum heat insulating material having a desired thermal conductivity can be obtained by controlling the content to be not more than%.

(Embodiment 2) FIG. 4 shows the relationship between the aspect ratio and the thermal conductivity when urethane powder is used as the organic powder. In order to make the other conditions the same, a wet silica powder (particle size 5 μm) was used as the inorganic powder, and the addition amount was 5% by weight.

[0050]

FIG. 4 shows that there is a correlation between the volume ratio of particles having a particle diameter of 200 μm or less and the thermal conductivity of the vacuum heat insulator, and the thermal conductivity changes with the aspect ratio of 2.5 as the minimum point. I understand. This indicates that the thermal conductivity of the vacuum heat insulator is clearly affected by the aspect ratio, which supports the validity of the present invention.

When the aspect ratio is 2.5 or less, the heat conductor of the vacuum heat insulator deteriorates. This is because the powder has a more spherical shape due to the smaller aspect ratio and takes a close-packed form.

As a result, the powder packing density becomes high, and the solid thermal conductivity increases due to the contact between the powders. On the other hand, when the aspect ratio is 2.5 or more, the powder has a non-spherical shape, so that the powder cannot take a close packing form due to steric hindrance.

Therefore, the powders have a coarse agglomerate form, and as a result, the voids formed by the agglomeration also become large, so that the air gap distance longer than the mean free path of air increases.

Therefore, the thermal conductivity of the gas increases due to the collision of the gas molecules, and the thermal conductivity of the vacuum heat insulating material deteriorates.

From the above, it is important to limit the aspect ratio. In the present invention, the aspect ratio is set to 2 or more and 3 or less in order to set the thermal conductivity of the vacuum heat insulator to 0.0050 kcal / mh ° C. or less. There is. As a result, a sufficient effect can be obtained even when it is laminated with urethane foam.

Example 3 Table 1 shows the relationship between the type of organic powder used for the core material 1 and the thermal conductivity of the vacuum heat insulating material. In order to eliminate influences other than the organic powder used for the core material, the average particle size of the organic powder was unified to 300 μm, the mixed inorganic powder was wet silica powder (particle size 5 μm), and the addition amount was 5% by weight.

[0057]

[Table 1]

From the results shown in Table 1, it can be seen that the one using the urethane powder according to the example of the present invention has the lowest thermal conductivity. The urethane bond has a double bond and high thermal vibration energy. As a result, the thermal conductivity of the vacuum heat insulator decreases because the solid thermal conductivity can be reduced.

Therefore, the organic powder used for the core material cannot be randomly selected, and must be limited to a specific material. In the present invention, the organic powder is limited to the urethane powder in view of the above-mentioned embodiment, so that the vacuum heat insulator having a particularly low thermal conductivity can be obtained.

Further, as an effect to be provided, since urethane foam used as a heat insulating material in a refrigerator or the like can be used, it is also useful for solving a recycling problem in the refrigerator.

Example 4 Table 2 shows the relationship between the type of inorganic powder used in the core material 1 and the thermal conductivity of the vacuum heat insulating material. In order to eliminate effects other than the type of inorganic powder used for the core material, the average particle size of the inorganic powder is 5 μm, and the addition amount is 5
It was made into the weight%. The organic powder used has an average particle size of 30.
Unified to 0 μm urethane powder.

[0062]

[Table 2]

From the results of (Table 2), even if the same silica powder is used, the milled silica powder of the example of the present invention shows the lowest thermal conductivity. Although silica powder is generally spherical, a new surface appears because the silica powder is crushed by the grinding treatment, and the surface becomes extremely uneven. This is because the collision energy when pulverizing the silica powder is large because a grinding method such as a ball mill is used.

As a result, it is possible to reduce the contact area between the powders by the surface modification action by mixing with the organic powder, and it is possible to obtain a vacuum heat insulating material having a low thermal conductivity due to the reduction of the solid thermal conductivity. . The grinding method is not limited to the ball mill, and the same effect can be obtained if a general grinding method such as a hammer mill is used.

(Embodiment 5) Next, in the case of a heat insulating box, the vacuum heat insulating body 1 to be applied has a short air gap distance formed by powder, so that the vacuum degree becomes close to the 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 thermal conductivity of the vacuum heat insulator is solved.

[0066]

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 an outer covering material, a particle size distribution of the organic powder having a particle diameter of 200 μm or less is 10% or more by volume ratio 3
It is limited to 0% or less. Therefore, the solid thermal conductivity can be reduced, and a vacuum heat insulator having excellent heat insulating performance can be obtained.

The vacuum heat insulator of the present invention has a particle size of 200
20% or more by volume ratio of particle size distribution in μm or less 20
% Of the organic powder and the inorganic powder, and the aspect ratio of the organic powder is limited to 2 or more. Therefore, the steric hindrance effect of the organic powder is enhanced, and the thermal conductivity can be reduced by reducing the density.

The vacuum heat insulator of the present invention uses hard urethane foam powder as the organic powder. Therefore, it becomes possible to recycle the rigid urethane foam used as the heat insulating material of the refrigerator and solve the waste problem. Also, since the organic powder is a hard urethane foam, the resin thermal conductivity of the organic powder is low,
When applied to a vacuum heat insulator, the thermal conductivity can be reduced.

In the vacuum heat insulator of the present invention, silica powder which has been subjected to a grinding treatment is applied as the inorganic powder material. Since the surface roughness of the silica powder is improved by the grinding treatment,
In the surface modification action by mixing with the organic powder,
The contact area between the powders can be reduced, and the solid thermal conductivity can be reduced.

The heat-insulating box body of the present invention is a heat-insulating dental 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 foamed heat insulating material. The inner surface has a particle size distribution of 200 μm or less in a volume ratio of 1
A vacuum heat insulator is provided in which a core material made up of 0% or more and 30% or less of an organic powder and an inorganic powder is filled in an outer covering material.

Therefore, since the vacuum insulating body has a short air gap distance, the change in thermal conductivity is small even when the degree of vacuum approaches atmospheric pressure. Therefore, when applied to a refrigerator, it is used for a long time. Even if it does, the thermal conductivity of the vacuum insulator does not suddenly deteriorate.

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.

[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.

FIG. 3 is a characteristic diagram showing the relationship between the volume ratio and the thermal conductivity of organic powder having a particle size of 200 μm or less in one embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the aspect ratio and the thermal conductivity of organic powder in an example of the present invention.

[Explanation of symbols]

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

Claims (5)

[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, and the organic powder has a particle size distribution with a particle size of 200 μm or less in a volume ratio of 10% or more and 30% or less. Insulation. 2. The vacuum heat insulator according to claim 1, wherein the organic powder has an Apgest ratio of 2 or more and 3 or less. 3. The vacuum heat insulator according to claim 1, wherein the organic powder is a hard urethane foam powder. 4. The vacuum heat insulator according to claim 1, wherein the inorganic powder is silica powder which has been subjected to a grinding treatment. 5. An insulating box body in which an outer box, an inner box, a space formed by the outer box and the inner box is filled with a foamed heat insulating material, and a vacuum heat insulator is provided on an inner surface of the outer box or the inner box. In the above-mentioned vacuum heat insulator, the outer cover material is filled with a core material composed of at least organic powder and inorganic powder, and the particle size distribution of the organic powder having a particle size of 200 μm or less is 10% or more and 30% or less by volume ratio. Insulation box that is.