JP3132139B2 - Insulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulator for use in refrigerators, freezers, prefabricated freezers, and the like.

[0002]

2. Description of the Related Art In recent years, as a part of energy saving, higher performance of a heat insulating material has been achieved. Taking a refrigerator as an example,
In order to improve the heat insulating performance of the heat insulator, a heat insulator whose internal pressure is reduced (called a vacuum heat insulator) is used. FIG. 6 shows a cross-sectional view of this heat insulator. 1 is a laminate film composed of three layers of polyester (hereinafter referred to as PET) -aluminum foil-heat fusion layer. 2 is a foam made of rigid urethane foam having open cells, for example. As the adsorbent, one in which an adsorbent such as zeolite is filled in a permeable package 8 is used.

[0003] Among them, the characteristics required for the laminated film 1 include low permeability of gas and liquid and low heat conductivity. Therefore, conventionally, a laminated film having a structure as shown in FIG. 7 has been used. In this conventional laminated film, a heat sealing layer 6 made of, for example, high-density polyethylene is bonded to a gas barrier layer made of a PET film 4 on which an aluminum film 5 is deposited by using an adhesive 7. The gas barrier layer prevents gas from permeating into the heat insulating material, thereby preventing heat insulation from deteriorating. In addition, since the aluminum film 5 has a small thickness of about 0.5 μm, the heat leak through the aluminum film 5 is small, so that the aluminum film 5 has high heat insulation performance.

[0004]

However, in the heat insulator using the PET film 4 on which the aluminum film 5 is deposited, the density of the aluminum layer is low due to the deposition film, and the gas barrier property is lacking. At the beginning of use, gases, liquids and the like that have penetrated through the laminated film 1 are adsorbed by the adsorbent 3, so that the heat insulating property does not deteriorate.
However, when the adsorbent 3 is saturated with a gas, a liquid, or the like due to long-term use, the gas, a liquid, or the like is filled in the foam, and heat insulation is impaired.

Therefore, instead of using a vapor-deposited film for the aluminum film 5, an attempt was made to bond an aluminum foil to the PET film 4 using an adhesive 7 as shown in FIG.
When the aluminum foil 5 is used, since the gas barrier property is good, the heat insulating property does not deteriorate even after long-term use.
However, the thickness of the aluminum foil 5 is at least 7
μm or more was required, so that the heat leak along the aluminum foil 5 was large, and sufficient heat insulation performance could not be obtained. This is because P and P
The heat rays absorbed by the ET film 4 travel through the aluminum foil 5 and reach the heat-sealed portion of the laminated film. Since the heat-sealed portion has a structure as shown in FIG. 7, since the thickness of the heat-sealing layer is as thin as 50 to 100 μm, heat easily moves to the laminate film on the opposite side. For this reason, the heat insulation of the heat insulator deteriorated.

[0006] The present invention is to solve the above problems,
It is an object of the present invention to provide a heat insulator having excellent heat insulation properties and little deterioration with time of heat insulation properties.

[0007]

According to the present invention, in order to solve the above-mentioned problems, at least one of the two laminated films does not have a metal foil layer in the heat seal portion.

[0008]

According to the present invention, the heat ray absorbed by the PET film among the conduction heat and the radiant heat by the above construction is transmitted to the aluminum foil but is not transmitted to the other aluminum foil at the heat sealing portion, so that the heat leak is greatly reduced. be able to.

[0009]

EXAMPLES First, a laminated film of this example will be described. The performance required as the exterior of the heat insulator is that air and moisture are hardly permeated, vacuum retention is good, thermal conductivity is small, mechanical strength to withstand external pressure, and vacuum sealing is easy. And light weight. As a material satisfying these conditions, a laminate film having a three-layer structure of a protective layer, a gas barrier layer, and a heat sealing layer is suitable.

Next, the gas barrier layer will be described. In a vacuum insulator such as this embodiment, the higher the degree of vacuum, the smaller the number of heat carriers. Therefore, the laminated film needs gas barrier properties to maintain the degree of vacuum. The gas barrier layer is for preventing moisture, organic gas, carbon dioxide gas and the like from entering the heat insulator. Therefore, a substance having a dense molecular structure is required for the gas barrier layer. For this, metal foil is preferable to plastic film. Among them, aluminum foil was selected from the viewpoint of workability and cost. Furthermore, since aluminum has a dense structure, it has a high gas barrier property and a high far-infrared reflection characteristic. Due to this high gas barrier property,
It is possible to maintain the degree of vacuum of the vacuum heat insulating material for a long period of time, and also to prevent heat leakage due to radiant heat transfer due to high far-infrared reflection characteristics.

There are two types of aluminum films used for the heat-insulating laminate film: a vapor-deposited film and an aluminum foil. Of these, the aluminum vapor-deposited film has a small thickness of about 0.5 μm, and thus has a small heat leak through the aluminum film, but is inferior in gas barrier properties as compared with the aluminum foil. Therefore, using an aluminum foil makes it possible to obtain a heat insulator having good vacuum retention.
Aluminum foils of various thicknesses from 7 μm to 100 μm in thickness are generally produced. The thinner the aluminum foil, the easier it is to form pinholes. Although the pinhole-less aluminum foil has a thickness of 15 μm or more, in reality, even a 7 μm-thick aluminum foil has sufficient airtightness. Therefore, the thickness of the aluminum foil needs to be determined by comparing the change in the degree of vacuum with time and the cost. But,
If the plate thickness exceeds 20 μm, the rigidity of the aluminum foil increases, and the laminated film springs back during heat fusion to reduce the fusion strength, or the laminate film may be wrinkled and deteriorate the vacuum retention. ,
The plate thickness of the aluminum foil is desirably 20 μm or less.

Next, the protective layer of this embodiment will be described. If the aluminum layer is exposed on the surface of the laminate film, there is a possibility that the gas barrier property may be impaired due to damage due to a certain beat or oxidation due to long-term use. Therefore, it is advisable to provide a protective layer of a plastic film on the surface. Properties required for the protective layer include being hard and not easily damaged, and having a certain degree of gas barrier properties. Polyester (PET), polypropylene, and the like are given as those having these characteristics. Among them, polyester has a high gas barrier property and is most suitable for the heat insulator of this embodiment. It is sufficient if the thickness of the protective layer is 12 μm or more. However, if the thickness is too large, heat is generated by absorption of far-infrared rays and the thermal conductivity is increased.

Next, the heat-sealing layer of this embodiment will be described. For this purpose, it is necessary to have a moderately low melting point in order to enhance the heat fusibility and to have a somewhat high gas barrier property in order to prevent gas from entering the heat fusible layer.
Those satisfying these two conditions include polyethylene, modified acryl and the like. Among these, when polyethylene is used, the higher the crystallinity of polyethylene, the more excellent the chlorofluorocarbon resistance. If modified acrylic is used, the chlorofluorocarbon resistance is satisfactory. The thickness of the heat sealing layer is
If the thickness is too small, the fusion strength decreases, so that it is preferably 30 μm or more. It does not matter if the thickness is large, but 30 to 70 μm is appropriate in consideration of cost.

The above three layers are adhered to each other by, for example, a polyester adhesive or the like to form a laminate film.

The laminated film is heat-sealed after covering the rigid urethane foam and the adsorbent. When the heat seal portion has a conventional cross section as shown in FIG. 7, heat transmitted from the high temperature portion through the aluminum foil transfers to the other aluminum foil through the heat sealing layer. In the case of the conventional configuration, the thickness of the aluminum foil and the thermal conductivity of the heat insulator had a relationship as shown in (Table 1).

[0016]

[Table 1]

From the results shown in Table 1, it can be seen that the influence of the aluminum foil on the heat leak is very large. Therefore,
If one of the two heat-sealed portions of the laminated film is free of aluminum foil, the cross-section of the heat-sealed portion becomes as shown in FIG. 1, so there is almost no heat leak through the aluminum foil and the thermal conductivity is reduced. It is possible to

Several methods are conceivable as a method for eliminating the aluminum foil in one of the heat-sealed portions of the two laminated films. For example, there is a method in which one of the aluminum foils is peeled off together with the protective layer after the heat bonding, and a method in which the aluminum foil and the heat bonding layer are peeled off in advance. However, it has been difficult to actually commercialize them because of the cost and lack of mass productivity. Therefore, we found two structures to realize it.

The first method is to make one of the two laminated films into a partially laminated film as shown in FIG. That is, a structure in which the heat seal portion has no aluminum foil in advance. However, the method of attaching the aluminum foils 5 one by one lacks mass productivity. Therefore, a partial laminate film may be prepared by the following method. First, after applying the adhesive 7 to the PET film 4, the aluminum foil 5 is attached. Next, an etching resist is applied on the upper surface of the aluminum foil 5 by printing or the like on a portion where the aluminum foil 5 is to be left, and is cured. Next, the unnecessary portion is dissolved by dipping in an acid or an alkali. Next, after applying the adhesive 7 again from above, the fusion layer 6 made of high-density polyethylene is adhered. The partially laminated film thus obtained is excellent in mass productivity, can be supplied at relatively low cost, and can be partially laminated with high precision (hereinafter, referred to as a partially laminated film (Part 1)).

In the second method, the two laminated films are partially laminated films having no metal foil layer only at portions corresponding to the heat-sealed portions along two opposing sides as shown in FIG. When two heat-sealed parts have a metal foil layer, the two laminated films are rotated by 90 degrees so that the other heat-sealed part does not have a metal foil layer. With this method, it is only necessary to use an aluminum foil having a width smaller than that of the conventional aluminum foil at the time of producing a laminate film, and the etching step can be omitted,
It is possible to supply a partially laminated film that is more excellent in mass productivity, inexpensive and highly accurate than the first method (hereinafter referred to as a partially laminated film (Part 2)).

Next, the rigid urethane foam of this embodiment will be described. Rigid urethane foam has been used frequently as a heat insulating material since it contains a large amount of pores and has excellent heat insulating properties. This is, for example, by foaming with a urethane high-pressure foaming machine using the raw materials and the number of parts shown in (Table 2), aging at room temperature with a hardened urethane foam, and cutting into a predetermined size except for a skin layer. Things.

[0022]

[Table 2]

In Table 2, the polyol is a polyether polyol having a hydroxyl value of 442 mgKOH / g obtained by addition polymerization of propion oxide using an aromatic diamine as an initiator. The foam stabilizer is Shin-Etsu Chemical
Co., Ltd. silicone surfactant F-318, foaming agent,
CFC R-11 manufactured by Showa Denko KK The catalyst is dibutyltin dilaurate. The bubble communicating agent is calcium stearate manufactured by NOF Corporation. The organic polyisocyanate is a polyisocyanate having an amine equivalent of 150 obtained by reacting toluylene diisocyanate with trimethylpropane and diethylene glycol.

Next, the adsorbent of this embodiment will be described. Conventionally, the thermal conductivity has been reduced by the pores of the rigid polyurethane foam, but this has a limitation. The reason is that the gas in the pores becomes a heat carrier. The adsorbent is for preventing gas from remaining in the heat insulating agent during vacuum processing. The gas remaining in the insulation is
It is mainly carbon dioxide gas, organic gas such as amine gas and Freon R-11 as catalyst, and moisture. Although a porous substance such as perlite or zeolite is effective, it is preferable to use a gas adsorbent specific to each gas. For example, when calcium chloride is used as a moisture adsorbing substance, calcium hydroxide is used as a carbon dioxide adsorbing substance, and activated carbon is used as an organic gas adsorbing substance, residual gas is removed by the following mechanism. First, the remaining water is adsorbed by the calcium chloride. Using the adsorbed water as an initiator, the adjacent calcium hydroxide reacts with CO ₂ and adsorbs as shown in the following formula.

[0025]

Embedded image

The water generated by this reaction is again adsorbed as calcium chloride crystal water. Organic gas such as amine gas of catalyst and R-11 of foaming agent is adsorbed by activated carbon.

The adsorbent powder is also required to have low thermal conductivity. For that purpose, it is necessary to reduce the heat transfer between the adsorbents, as well as the thermal conductivity of the adsorbents themselves. Therefore, selection of the material and particle size of the adsorbent is important.

Next, a detailed embodiment of the present invention will be described with reference to the drawings. First, as shown in (Table 2), raw materials were blended, and a rigid urethane foam was foamed with a urethane high-pressure foaming machine.
It is cut into a size of 20 cm × 20 cm × 2 cm, and then heated at 140 ° C. for about 1 hour to evaporate the adsorbed water and evaporate a part of the gas swelling in the resin skeleton to form the foam 2. As the adsorbent 3, powders of calcium hydroxide, calcium chloride, and activated carbon were uniformly mixed, and the resultant was integrally molded into a granule and filled in a package 8 having air permeability.

As shown in FIG. 4, a package 8 filled with the foam 2 and the powders of calcium hydroxide, calcium chloride and activated carbon as the adsorbent 3 and uniformly molded into a granulated form is filled in as shown in FIG. Laminated film consisting of a transparent PET film-aluminum foil-heat sealing layer (part 1)
No. 9 and a laminated film film 1 composed of the same plastic film-aluminum foil-heat sealing layer as in the prior art
After depressing the inside, depressurize the inside to 0.05 mmHg and seal
A heat insulator having the same structure as that of the conventional example shown in FIG. 6 was obtained. This is referred to as (Example 1).

A package 8 filled with the foam 2 and the powder of calcium hydroxide, calcium chloride and activated carbon as the adsorbent 3 and uniformly molded into granules is packed in After sandwiching between two partial laminated films (part 2) 10 composed of a plastic film, an aluminum foil, and a heat-sealing layer as shown in FIG. 5 shifted by 90 degrees, the inside is evacuated to 0.05 mmHg, and the inside is closed and the appearance is reduced. To
Obtained a heat insulator having a structure similar to that of the conventional example shown in FIG . This is referred to as (Example 2).

The initial thermal conductivity and the thermal conductivity after 30 days of the obtained heat insulator were measured at an average temperature of 25 using K-Matic manufactured by Vacuum Riko Co., Ltd.
C. and the results are shown in (Table 3). The comparative example shows a heat insulator using the conventional laminated film 1. The above three examples are all PET films having a thickness of 2
The aluminum foil having a thickness of 5 μm, the aluminum foil having a thickness of 9 μm, and the high-density polyethylene having a thickness of 50 μm as a heat-sealing layer were bonded to each other using a polyester-based adhesive.

[0032]

[Table 3]

As shown in Table 2, in the heat insulator according to the embodiment of the present invention, the heat insulation properties of both (Example 1) and (Example 2) were improved by about 20% as compared with the conventional heat insulator. This is 2
This is because at least one of the heat-sealed portions of the laminated films did not have the aluminum foil layer, so that heat conduction through the aluminum foil could be reduced. In addition, (Example 1) and (Example 2) showed almost the same effect.

The material and thickness of each layer used in the embodiment of the present invention are not particularly limited.
In particular, since the aluminum foil does not exist in the heat-sealed portion of the partially laminated film shown in FIG. 4, it is possible to use a thick aluminum foil of 20 μm or more to further improve the airtightness.

[0035]

As is apparent from the above description, according to the present invention, at least one of the two laminated films covering the foam and the adsorbent has a structure in which the heat seal portion has no aluminum foil. Therefore, among the conduction heat and the radiation heat, the heat ray absorbed by the PET film is transmitted to the aluminum foil, but is not transmitted to the other aluminum foil at the heat sealing portion, so that the heat insulating property of the heat insulator can be improved.

Further, the introduction of the partial laminate film makes it possible to supply the above-mentioned heat insulator at low cost and easily.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heat seal according to the present invention .

FIG. 2 is a sectional view of a laminate film of the present invention.

FIG. 3 is an enlarged view of a heat seal portion of the heat insulator according to one embodiment of the present invention.

FIG. 4 is a view showing an existing portion of an aluminum foil of a partially laminated film (part 1) according to another embodiment of the present invention.

FIG. 5 is a view showing an existing portion of an aluminum foil of a partially laminated film (part 2) according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional heat insulator.

FIG. 7 is a cross-sectional view of a conventional heat insulator (the two upper and lower laminated films are rotated by 90 degrees with respect to each other).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated film 2 Foam 3 Adsorbent 4 PET film 5 Aluminum film (foil or vapor-deposited film) 6 Thermal fusion layer 7 Adhesive 8 Package 9 Partial laminate film (part 1) 10 Partial laminate film (part 2)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16L 59/06-59/08 B32B 3/02 B65D 81/38 F25D 23/06

Claims (6)

(57) [Claims] 1. A laminated film composed of at least three layers of a plastic film layer, a metal foil layer, and a heat-sealing film layer. A heat insulator , wherein at least one of the two laminated films is
The other is a partial lamination that does not have a metal foil layer
A heat insulator, wherein the metal foil layers of the two laminated films are not brought into contact with each other in the heat-sealed portion. 2. A partial laminate film is heat insulation body according to claim 1, wherein the wherein the is obtained by etching the unnecessary parts of the metal foil layer. 3. A laminated film having a peripheral portion divided into a plurality of portions and a heat-sealed portion along two opposing edges thereof having no metal foil layer, and When one of the heat-sealed portions has a metal foil layer, the heat-sealed portion of the other laminated film has a structure without a metal foil layer.
2. The heat insulator according to 1 . 4. The method of claim 1, 2 or 3, characterized in that it comprises in addition to the gas adsorbent of the heat insulating member inside the foamed plastic
A heat insulator as described. 5. The heat insulator according to claim 4 , wherein the gas adsorbent comprises at least one of an organic gas adsorbent, a carbon dioxide adsorbent, and a water vapor adsorbent. 6. A heat insulating body according to claim 1, wherein the plastic film is characterized by comprising a polyester.