JPH091701A - Manufacture of vacuum heat insulator and honeycomb plate - Google Patents

Abstract

PURPOSE: To provide a low-cost vacuum heat insulator, which can obtain the vacuum state readily without providing a small hole in a cell bulkhead and has the excellent heat insulating property. CONSTITUTION: This is the vacuum heat insulator 10, wherein unit laminated bodies 3 formed by overlapping a plurality of honeycomb plates 2 are arranged in a vacuum container 5 that is an evacuated hollow structure. The neighboring honeycomb plates 2 are arranged so that the positions of cell bulkheads are arranged in an intersecting overlapped pattern to each other and in a mutually direct contact pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material used in refrigerators, freezers, warm storages and various other products.

[0002]

2. Description of the Related Art A vacuum heat insulating material whose inside is kept in a vacuum state has excellent heat insulating properties and is therefore used in various applications requiring heat insulation, heat insulation and the like. In addition, a vacuum heat insulating material using a honeycomb plate as an internal reinforcing material has been proposed in order to maintain excellent heat insulating properties and improve compressive strength.

As a conventional vacuum heat insulating material using a honeycomb plate, there is, for example, a vacuum heat insulating material disclosed in JP-A-57-187242. In this conventional vacuum heat insulating material, a honeycomb plate having a large number of cells and a plurality of metal films are alternately stacked and arranged in a hollow structure, and the inside of each cell is in a vacuum state. . Further, pores for leading out air are formed in all cell partition walls of each cell.

[0004]

However, the above conventional vacuum heat insulating material has the following problems. That is, the honeycomb plates and the metal films are alternately stacked. Therefore, the cells of the honeycomb plate are in a hermetically sealed state by the cell partition walls forming the cells and the upper and lower metal films. Therefore, in order to make the inside of the cells of the honeycomb plate arranged in the hollow structure a vacuum state, it is necessary to provide pores for leading out the internal air to the cell partition walls of all the cells. . The process of forming pores in the cell partition wall is very time-consuming and inevitably costly.

The present invention has been made in view of the above-mentioned conventional problems, and a vacuum state can be easily obtained without providing pores in the cell partition walls, excellent in heat insulating property, and inexpensive vacuum heat insulating material. Is to provide.

[0006]

According to the present invention, there is provided a vacuum heat insulating material provided in a hollow structure in which a unit laminated body formed by stacking a plurality of honeycomb plates is evacuated, and adjacent honeycomb plates in the unit laminated body are The vacuum heat insulating material is characterized in that the cell partition walls are arranged so as to overlap each other in a cross shape and are in direct contact with each other.

What is most noticeable in the present invention is that, in the above unit laminate, the adjacent honeycomb plates are arranged so that the cell partition positions thereof overlap each other and are in direct contact with each other. That is. That is, the adjacent honeycomb plates are positioned so that their cell partition walls are in point contact with each other, and no inclusion such as a metal film is interposed between the honeycomb plates.

Various materials can be used for the honeycomb plate. For example, metals such as aluminum and stainless steel, phenol resin-impregnated kraft paper, organic materials such as vinyl chloride and aromatic polyamide, and inorganic materials such as carbon fiber paper can be used.

The size of the cells in the honeycomb plate is
It is determined by the required compressive strength and heat insulation, and it is preferable to change it appropriately according to the application. That is, when the size of the cell is increased, the heat insulating effect is improved but the compressive strength is lowered, while when the size of the cell is decreased, the compressive strength is improved but the heat insulating effect is decreased.

Therefore, generally, according to each application,
It is preferable that the cell diameter is 300 mm to 0.001 mm, and the thickness of the cell partition wall is appropriately selected within the range of 1/10 to 1/10000 times the cell diameter. Further, the height of the cell partition wall, that is, the thickness of the honeycomb plate is 1/10 of the cell diameter.
It is preferable to select from the range of 0 to 100 times. This makes it possible to appropriately select a vacuum heat insulating material having properties of heat insulating effect and compressive strength according to each application. More preferably, the cell diameter is 100 mm to 0.01 mm, the cell partition wall thickness is preferably 1/10 to 1/200 times the cell diameter, and the cell partition wall height is preferably 1/10 to 10 times the cell diameter. .

Further, the larger the number of laminated honeycomb plates constituting the unit laminated body having the same thickness, the more advantageous the heat insulating property. That is, in a unit laminate having the same thickness, a large number of thin honeycomb plates stacked has more point contact portions of cell partition walls than a small number of thick honeycomb plates stacked. Therefore, when heat is conducted through the cell partition wall, the effect of blocking the heat is high and the thermal resistance can be increased.

The cells in the honeycomb plate are penetrating cells formed by the cell partition walls, and the shapes thereof are hexagonal, quadrangular, other polygonal, cylindrical, etc.
It can have various shapes.

As the hollow structure, various structures can be used as long as the internal vacuum can be maintained. For example, there are metals such as aluminum and stainless steel, and plastic films having a barrier property. Further, it is preferable to attach a suction pipe for vacuuming to the hollow structure. Thus, the inside of the hollow structure can be easily sealed by closing the suction pipe after vacuuming the inside of the hollow structure. Here, the evacuation is a concept that includes not only a vacuum but also a depressurized state of a necessary degree.

Further, it is preferable that the cell diameters of the cells in the adjacent honeycomb plates are different from each other and that the ratio of the two is not an integer ratio. This gives
When the unit laminate body is manufactured, the cell partition walls do not overlap each other without positioning adjacent honeycomb plates.

The unit laminate may be formed by stacking a plurality of the laminates, and a support having pores may be interposed between the unit laminates. This gives
It is possible to improve the compressive strength in the lateral direction of the unit laminate and to provide a shield effect against radiant heat.

As the material of the support, various materials can be used, but those having appropriate rigidity and heat ray shielding effect are preferable. For example, metals such as aluminum and stainless steel, phenol resin-impregnated kraft paper, organic materials such as vinyl chloride and aromatic polyamide, and inorganic materials such as carbon fiber paper can be used. The support is usually plate-shaped or film-shaped. The thickness of the support is not particularly limited, but if it is too thin,
May cause strength problems.

The pores in the above-mentioned support are for providing communication between the honeycomb plates. Therefore, if at least one fine hole is provided in one support, that function can be fulfilled. However, in order to improve the suction speed during evacuation, it is preferable to provide two or more. Further, the diameter of the pores may be appropriately determined in consideration of the evacuation speed and the material strength.

Further, the number of the above-mentioned supports is determined by the required compressive strength and the heat ray shielding effect, and it is preferable to appropriately change the number according to the application. Specifically, it is preferable to interpose one support for every 2 to 100 honeycomb plates. Needless to say, the support may not be used if the compressive strength and the heat ray shielding effect are not required.

When the above support is used, it is more preferable that the support and the honeycomb plate be fixed by an adhesive or welding. This can improve the compressive strength of the unit laminate. When it is not necessary to improve the compressive strength and only the heat ray shielding effect is improved, the support and the honeycomb plate may be simply laminated without being fixed by an adhesive or the like.

Further, in the cells of the honeycomb plate,
It is more preferable that the open cell body is incorporated. As a result, a more efficient vacuum heat insulating effect can be obtained even in a state of a relatively low degree of vacuum. The open-cell body is an open-cell structure having cells communicating in the thickness direction or the width direction of the cell plate, and if the cell size is fine and the thermal conductivity is small, various types are available. Can be used.

That is, the above-mentioned open-cell body needs to have an open-cell structure in order to enable the discharge of air during evacuation. And, the finer the bubbles, the more the vacuum adiabatic effect can be exhibited even at a relatively low degree of vacuum. Specifically, depending on the cell diameter, 100 μm
The following is preferred. If it exceeds 100 μm, there is a problem that the heat insulating property is poor in a low vacuum. Therefore, the thickness is more preferably 1 μm or less, further preferably 0.1 μm or less.

The open-cell body is preferably made of a material having a low thermal conductivity such as an organic material.
In addition, since the above-mentioned open-cell body has a lower thermal conductivity, it is preferable that the density thereof be smaller, and generally 200 kg / m ³
The following is preferred.

As the material of the open-cell body, for example, so-called foamed polymer such as polyurethane, polystyrene, polypropylene, polyester and polyamide can be used. In addition, various materials can be used as long as they satisfy the above conditions.

The reason why an efficient vacuum heat insulating effect can be obtained even in a relatively low degree of vacuum by using the open-cell body is considered as follows. That is, the inside of the cells of the honeycomb plate is divided into finer spaces by incorporating the above-mentioned open-cell body, and has a fine cell structure. Therefore, even when the degree of vacuum is relatively low, the gap between the structural walls with respect to the mean free path of the air remaining in the hollow structure can be reduced. Therefore, mutual collisions between air molecules that try to conduct heat are suppressed, and a more efficient vacuum adiabatic effect can be provided.

Particularly when the honeycomb plate is made of an organic material such as phenol resin-impregnated kraft paper, vinyl chloride, and aromatic polyamide, it is effective to keep the adiabatic effect in the cell in order to maintain the heat insulating effect. Is. That is, in the case of the above organic material, it is difficult to eliminate the components that volatilize under vacuum. Therefore, it is relatively difficult to maintain a high vacuum state of 10 ⁻³ Torr or less for a long period of time, and the degree of vacuum gradually decreases. Therefore, it is effective to incorporate the above-mentioned open-cell body in a honeycomb plate using such an organic material.

Next, as a method for manufacturing a honeycomb plate having the above-mentioned open-cell body built therein, there is the following method. That is, it is characterized by comprising an injection step of injecting a resin composition for forming an open cell structure in the cells of the honeycomb plate and a bubble forming step of forming an open cell structure by the resin composition in the cells. There is a method for manufacturing a honeycomb plate containing the open-cell body.

Specific examples of the above method include a foaming method and a freeze-drying method. The foaming method includes an injection step of injecting a basic raw material mixed with a foaming raw material, a main foaming material, a foaming auxiliary agent, a silicone foam stabilizer, and a catalyst into cells of a honeycomb plate, and heating the basic raw material Is formed in the cell. And after foaming,
By cutting the portion of the honeycomb plate that overflows from the cells and drying it in a vacuum atmosphere, it is possible to incorporate the open-cell body in the cells of the honeycomb plate.

As the above-mentioned basic raw material, for example, polyether polyol (molecular weight, 30
00) and isocyanate TDI-80 each 10
It is possible to use 0 parts by weight, 3 parts by weight of water as a main foaming agent, 0.3 parts by weight of a silicone foam stabilizer, and 2.5 parts by weight of each of a tertiary amine catalyst and an organic tin catalyst. .

The freeze-drying method includes, for example, an injection step of injecting a cyclohexane solution of polystyrene resin (3% concentration) into the cells so that the honeycomb plate made of phenol-impregnated kraft paper is filled, and a vacuum atmosphere after the injection. It comprises a foaming step of obtaining an open cell structure by cooling to below freezing and vacuum freeze-drying. According to this, it is possible to incorporate the open-celled body having the open-celled structure of about several tens of μm or less into the honeycomb plate.

As another method, a method of burying amorphous organic ultrafine particles or porous particles in a honeycomb to form a structure of open cells can be adopted.

[0031]

[Operation and effect] In the vacuum heat insulating material of the present invention, the adjacent honeycomb plates constituting the unit laminate are arranged so that the cell partition walls do not overlap each other without any interposition therebetween. There is. Therefore, the cells in the honeycomb plate are in conduction with not only the upper and lower cells but also all the cells.

Therefore, even if pores are not provided in all cell partition walls as in the conventional case, it is possible to easily bring all cells into a vacuum state by sucking air from a part of the hollow structure. . Further, this makes it possible to eliminate the step of forming the pores in the cell partition walls, and to significantly reduce the cost.

Further, the cell partition walls of the adjacent honeycomb plates are in point contact with each other. Therefore, even when heat is conducted through the cell partition wall, the point contact portion becomes a thermal resistance and the heat conduction can be suppressed. Therefore, an excellent heat insulating effect can be obtained. Therefore, according to the present invention, a vacuum state can be easily obtained without providing pores in the cell partition walls, and it is possible to provide an inexpensive vacuum heat insulating material having excellent heat insulating properties.

[0034]

【Example】

Example 1 A vacuum heat insulating material according to an example of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 1, the vacuum heat insulating material 10 of this example is a vacuum heat insulating material in which a unit laminate body 3 formed by stacking two honeycomb plates 2 is arranged in a vacuum container 5 which is a hollow structure. Then, as shown in FIGS. 3 and 4, the two honeycomb plates 2 constituting the unit laminate 3 are arranged so that the cell partition walls 21 of the two honeycomb plates 2 overlap each other, and between the two, They are in direct contact with each other without any intervention.

Further, as shown in FIG. 1, three unit laminates 3 are arranged in a stack in a vacuum container 5, and pores 61 are provided between and above and below the unit laminates 3. The support 6 is interposed. In FIG. 1, the unit laminate body 3 and the support body 6 and the support body 6 and the vacuum container 5 are illustrated separately for the sake of easy understanding of the configuration, but they are actually in contact with each other.

As shown in FIGS. 3 and 4, the honeycomb plate 2 is made of phenolic resin-impregnated kraft paper, has a hexagonal cell shape, a cell partition wall thickness of 0.10 mm, a cell partition wall height of 3 mm, A cell having a cell diameter (FIG. 4, symbol D) of 3 mm and a plate size of 100 mm × 100 mm was used. As shown in FIGS. 3 and 4, the honeycomb plate 2 is
One unit laminate is made up of one sheet, and each cell wall 2
The 1s are stacked directly so that they do not overlap.

As the support 6, as shown in FIGS. 1 and 2, phenol resin-impregnated kraft paper 100 mm × 1
00 mm was used. In addition, the pores 61 provided in the support 6
As shown in FIGS. 1 and 2, the holes are holes having a diameter of 1 mm, and about 500 holes are provided per 1 m ² .

As the vacuum container 5, as shown in FIGS. 1 and 2, a multilayer film for a vacuum pack having a suction pipe 58 for vacuuming is used.

Next, in manufacturing the vacuum heat insulating material 10 of this example, as shown in FIG.
The unit laminate body 3 and the support body 6 are alternately arranged, and they are joined by an adhesive. Next, the air in the vacuum vessel 5 is sucked through the suction pipe 58 to about 10 ^-5 Tor.
Vacuum to r. After the vacuum state, the vacuum container 5
The suction pipe 58 is closed off to obtain the vacuum heat insulating material 10.

Next, the function and effect of this example will be described. In the vacuum heat insulating material 10 of the present example, the adjacent honeycomb plates 2 forming the unit laminate body 3 are arranged so that the cell partition walls 21 do not overlap each other without any interposition therebetween. is there. Therefore, as shown in FIG. 5, the cells 20 in the honeycomb plate 2 are in conduction with not only the upper and lower cells 20 but all the cells 20.

Therefore, as in the conventional case, all cell partition walls 21 are
Even if no pores are provided in all the cells 20, it is possible to easily bring all the cells 20 into a vacuum state by sucking air from the suction pipe 58. Further, by doing so, the step of forming the pores in the cell partition wall 21 can be omitted, and the cost can be significantly reduced.

Further, the cell partition walls 21 of the adjacent honeycomb plates 2 are in point contact with each other. Therefore, heat is generated by the cell partition wall 2.
Even when 1 is conducted, the point contact portion becomes a thermal resistance and the thermal conduction can be suppressed. Therefore, an excellent heat insulating effect can be obtained.

Further, in the present example, the support 6 is interposed above and below the unit laminate 3. Therefore, the compressive strength of the unit laminate body 3 in the lateral direction can be improved, a shield effect against radiant heat can be provided, and the vacuum heat insulating effect can be further enhanced. Also,
The support body 6 is provided with the pores 61. Therefore, the efficiency of evacuation work is not reduced.

Therefore, according to this example, it is possible to easily obtain a vacuum state without providing pores in the cell partition walls, to obtain an inexpensive vacuum heat insulating material having excellent heat insulating properties.

Example 2 In this example, using the vacuum heat insulating material 10 of Example 1,
The amount of deformation (change in thickness of the vacuum heat insulating material) with respect to the compressive stress generated from the internal vacuum state was investigated. As the investigation method, the thickness change was measured by leaving it in the room for 4 days. FIG. 6 shows the result. In FIG. 6, the horizontal axis represents time (logt).
Min), and the vertical axis represents the ratio of the thickness after t minutes to the initial thickness of the vacuum heat insulating material.

As is known from FIG. 6, one week later (lo
When gt = 3.8), the ratio of the thickness to the initial thickness was about 98.8%, which was a reduction rate of about 1.2%. Ten years later (logt =
The deformation amount of 6.7) was estimated. As a result, it was found that the amount of deformation was suppressed to only about 2% after 10 years, and the sample had sufficient compressive strength. In the present example, the first embodiment
As described above, the phenolic resin-impregnated kraft paper of the above size was used as the honeycomb plate, but the compressive strength can be further improved by changing the material and size.

Example 3 In this example, instead of the honeycomb plate 2 of Example 1, an aluminum honeycomb plate was used. This honeycomb plate made of aluminum has a cell partition wall thickness of 0.05 mm, a cell partition wall height of 3 mm, a cell shape of hexagon, and a cell diameter of 3 mm. Others were the same as in Example 1. In this example, a vacuum heat insulating material having higher compressive strength can be obtained. In addition, the same effect as that of the first embodiment can be obtained.

Example 4 In this example, based on the vacuum heat insulating material 10 of Example 1, the thermal conductivity in the solid due to the difference in the number of laminated honeycomb plates 2 in the unit laminate 3, that is, the honeycomb partition wall The transferred thermal conductivity was evaluated by simulation.

As an evaluation method, as shown in FIGS. 7 to 9, when one unit laminate has a thickness of A mm, it is constituted by two honeycomb plates 422 having a thickness T2 = A / 2 mm (see FIGS. 8), several types of models (FIG. 9) configured by n honeycomb plates 423 having a thickness T3 = A / nmm were prepared, and the thermal conductivity of each model was measured. Also, for comparison, a unit laminate (FIG. 7) constituted by one honeycomb plate 421 having a thickness T1 = Amm was prepared, and the thermal conductivity was calculated in the same manner.

The calculation results are shown in FIG. In FIG. 10, the horizontal axis represents the relative number of honeycomb plates, and the vertical axis represents the relative ratio when the thermal conductivity is 1 when the number of honeycomb plates is 2. As is known from FIG. 10, the larger the number of laminated honeycomb plates constituting the unit laminated body is, the lower the thermal conductivity in the solid is and the better the result becomes. In particular, when the number of laminated sheets is about 18, It can be seen that the thermal conductivity is about 1/10 of that in the case.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a vacuum heat insulating material of Example 1.

FIG. 2 is a partially cutaway perspective view of the vacuum heat insulating material of the first embodiment.

FIG. 3 is an explanatory view showing a stacked state of honeycomb plates in Example 1.

FIG. 4 is an explanatory view showing a stacked state of honeycomb plates in Example 1.

FIG. 5 is an explanatory diagram showing a conducting state of cells of the honeycomb plate in Example 1.

FIG. 6 is an explanatory diagram showing the change over time in the thickness of the vacuum heat insulating material in the second embodiment.

FIG. 7 is an explanatory diagram showing a unit laminate body as a comparative product in Example 4.

FIG. 8 is an explanatory diagram showing a unit laminate body including two honeycomb plates in Example 4.

FIG. 9 is an explanatory diagram showing a unit laminate body including n honeycomb plates in Example 4.

FIG. 10 is an explanatory diagram showing the relationship between the number of stacked honeycomb plates and heat conduction in a solid in Example 4.

[Explanation of symbols]

 10. . . Vacuum insulation, 2. . . Honeycomb plate, 20. . . Cell, 21. . . Cell partition wall, 3. . . Unit laminate, 5. . . Vacuum container (hollow structure), 6. . . Support, 61. . . pore,

Claims (6)

[Claims] 1. A vacuum heat insulating material disposed in a hollow structure in which a unit laminate body made by stacking a plurality of honeycomb plates is evacuated, wherein adjacent honeycomb plates in the unit laminate body have cell partition walls thereof. The vacuum heat insulating material is characterized in that the positions of are overlapped with each other in a cross shape and are in direct contact with each other. 2. The vacuum heat insulating material according to claim 1, wherein the cell diameters of the cells in the adjacent honeycomb plates are different from each other. 3. The vacuum heat insulating material according to claim 2, wherein the cell diameters of the cells of the adjacent honeycomb plates are not an integer ratio. 4. The method according to claim 1, wherein:
A vacuum heat insulating material comprising a plurality of the above-mentioned unit laminates, and a support having pores interposed between the unit laminates. 5. The method according to claim 1, wherein:
A vacuum heat insulating material, characterized in that an open-cell body is built in the cells of the honeycomb plate. 6. An injection step of injecting a resin composition for forming an open cell structure into cells of a honeycomb plate, and a bubble forming step of forming an open cell structure with the resin composition in the cells. A method for manufacturing a honeycomb plate containing an open-cell body, comprising: