JPH11106539A - Getter for vacuum heat insulator and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a getter excellent in carbon dioxide absorption at even a vacuum of 0.005-5 Torr for preventing the lowering of heat insulation mainly by carbon dioxide for a vacuum heat insulator to seal a vacuum vessel after a core material made of urethane foam is inserted and evacuated. SOLUTION: A getter which is at least one of an oxide of an alkaline earth metal or a hydroxide of an alkaline earth metal manufactured by grinding to not greater than 150 μm average diameter under a low carbon dioxide concentration, or after grinding to not greater than 150 μm calcined at a temperature higher than its carbonate's decomposition temperature, and cooled in an atmosphere of low carbon dioxide concentration is contained in a vacuum heat insulation for sealing a vacuum vessel after a core material made of urethane foam is inserted and evacuated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a getter used under vacuum. For example, the present invention relates to a vacuum heat insulating material getter used for a vacuum heat insulating material used for refrigerators, thermos bottles, building materials, and the like.

[0002]

2. Description of the Related Art A vacuum heat insulating material in which a core material is inserted into an airtight container, the inside of which is evacuated, and then sealed is generally used. In order to remove the coming gas, a gas absorbent called a getter is used.

[0003] In a vacuum insulating material using open-cell urethane foam as a core material, unreacted isocyanate groups (-NC
O) reacts with a small amount of water such as the water used for foaming or the water that has permeated to generate carbon dioxide gas. The generation of carbon dioxide gas has been the main cause of lowering the heat insulating performance of the vacuum heat insulating material. As a carbon dioxide adsorbent, Japanese Patent Publication No. 6-105151 discloses the use of soda ash. JP-A-8-338683 discloses an alkali metal or alkaline earth metal oxide as an acid gas absorbent.
It has been proposed to use chemically reactive carbon dioxide absorbents such as hydroxides, organic acid salts and organic amines. However, among these chemically reactive carbon dioxide absorbents, the reaction between the solid reactive carbon dioxide absorbent and carbon dioxide is caused by the dissolution of carbon dioxide in the moisture in the presence of moisture and the reaction as carbonate ions. Therefore, it is not an exaggeration to say that under vacuum where almost no water is present, the absorption reaction amount is very small and practically no absorption occurs. For this reason, pulverization was performed in an attempt to increase the amount of carbon dioxide absorbed, but in pulverization in the air and subsequent storage in the air, the carbon dioxide in the air was immediately absorbed and sufficient Carbon dioxide absorption performance could not be shown. Also,
Under high vacuum, liquid carbon dioxide gas absorbent volatilizes the absorbent itself and volatilizes a small amount of low-boiling substances present as impurities, resulting in an increase in the pressure of the vacuum insulation and an increase in the thermal conductivity. Could not be used.

Further, Japanese Patent Publication No. 7-94950 discloses that as a carbon dioxide adsorbent of a closed-cell urethane heat insulator, a synthetic zeolite, activated carbon, and silica gel, which are physical adsorption type carbon dioxide gas absorbents, are not vacuum heat insulators. Are listed. However, these synthetic zeolites, activated carbon and physical adsorbents such as silica gel can absorb carbon dioxide even in the absence of moisture, but their absorption is significantly reduced under vacuum, and they must absorb carbon dioxide for a long period of time. However, in order to prevent this, a large amount of physical adsorbent was required, and the practicality was poor.

[0005] On the other hand, Japanese Patent Application Laid-Open No. 8-320179 proposes a measure of treating open-celled urethane foam with high temperature and high humidity to reduce unreacted isocyanate groups and suppress the generation of carbon dioxide gas. And the number of processes for the process increased, and the cost was severe.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a vacuum heat insulating material in which a urethane foam core material is inserted into an airtight container, the inside of which is evacuated, and then sealed. To provide a getter excellent in carbon dioxide gas absorbing ability even under a vacuum of 0.005 to 5 Torr.

[0007]

The absorption reaction of carbon dioxide gas on alkaline earth metal oxides and hydroxides under a vacuum in which almost no water is present has been found to occur because the absorption amount is very small. Although it was thought that the absorption did not take place, the present inventors found that the absorption reaction of carbon dioxide gas was caused by the adsorption of these absorbents to the surface layer, and when the surface layer was covered, the subsequent reaction proceeded to the surface layer. The diffusion rate of carbon dioxide from the inside to the inside becomes rate-limiting, and the absorption rate is significantly reduced. However, it has been found that the carbon dioxide can be effectively absorbed by increasing the surface area. Further, the present inventors have found that it is essential to prevent the absorption of carbon dioxide gas in the air at the time of pulverization and after the pulverization in order to sufficiently exhibit the carbon dioxide absorption performance, and have reached the present invention. That is, according to the present invention, a getter to be inserted into a vacuum heat insulating material for sealing after inserting a core material of urethane foam into an airtight container, evacuating the inside,
Or less, more preferably 100 μm or less of alkaline earth metal oxides and alkaline earth metal hydroxides.
It consists of more than one kind of vacuum heat insulating material getter. In addition, the present invention provides a vacuum heat insulating material having at least one of calcium oxide, calcium hydroxide, and barium oxide as a getter to be put into the vacuum heat insulating material, thereby improving the performance of the vacuum heat insulating material for a long time. To maintain. Furthermore,
These getters are a production method characterized in that an alkaline earth metal oxide or an alkaline earth metal hydroxide is pulverized in an atmosphere of a low carbon dioxide gas concentration. This production method is characterized in that after a hydroxide of an earth metal has been pulverized in advance, a carbonate present in a surface layer is removed or chemically changed into an oxide or a hydroxide.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The alkaline earth metal oxides and hydroxides of the present invention include calcium oxide, barium oxide, calcium hydroxide, barium hydroxide and the like. In particular, calcium oxide and barium oxide contain carbon dioxide gas. It is preferable because it has high absorption performance and releases less moisture under vacuum. These alkaline earth metal oxides and hydroxides may be used alone or as a mixture.

In the present invention, the absorption of carbon dioxide into alkaline earth metal oxides and hydroxides in a vacuum in which almost no water is present is carried out by adsorption to these surface layers. It is effective to increase the surface area, and the average particle size is preferably 150 μm or less, more preferably 100 μm or less.

The alkaline earth metal oxides and hydroxides used in the present invention are preferably supported on a carrier to increase the surface area, since a sufficient reaction rate under vacuum can be expected. As the carrier, silica gel, silica, alumina, activated carbon, synthetic zeolites such as molecular sieves, mordenite, natural zeolites such as erionite,
Clay minerals such as perlite, sepiolite, diatomaceous earth, and activated clay are listed. Among them, zeolite, activated carbon and silica are particularly preferred. Average particle size 150 used in the present invention
The getter for vacuum heat insulating materials having a size of μm or less is characterized in that a granular alkaline earth metal oxide or alkaline earth metal hydroxide is pulverized at a carbon dioxide gas concentration of 1 ppm or less, preferably 0.1 ppm or less. Is the way. In the present invention, replacement with an inert gas such as nitrogen gas or argon gas is generally used to create an atmosphere having a low carbon dioxide concentration from a carbon dioxide concentration of about 330 ppm existing in the air. The pulverization method used here is not particularly limited, and pulverization is performed by a known pulverizer such as a vibration mill, a ball mill, and a disk mill. Another method of obtaining the vacuum heat insulating material getter according to the present invention is as follows: an alkaline earth metal oxide, an alkaline earth metal hydroxide, are preliminarily pulverized in the atmosphere using a known pulverizer, and then the surface is pulverized. The carbonate present in the layer is converted to a carbonate decomposition temperature of 898 ° C. (dissociation pressure 1).
Atm) or more is calcined to form oxides or hydroxides by firing, and then cooled in an atmosphere having a carbon dioxide gas concentration of 1 ppm or less, preferably 0.1 ppm or less. In addition, the getter for vacuum heat insulating material obtained here is a bag using a film having a high gas barrier property such as an aluminum foil laminated film, a polyvinylidene chloride film, an aluminum vapor-deposited polyethylene terephthalate film, and a carbon container such as a metal container and a glass container. It is preferable to store in an atmosphere that is difficult to penetrate.

The getter for vacuum of the present invention may be used in combination with a dehumidifier, a deoxidizer, and an organic gas absorbent depending on the substance, application, use atmosphere and the like coexisting in the vacuum system. It is also a practical usage to select a vacuum getter that has both the function of a carbon dioxide gas absorbent and the functions of a dehumidifier, an organic gas absorbent, and the like.

Examples of the dehumidifier include synthetic zeolites typified by silica gel, aluminum oxide and molecular sieves, natural zeolites such as mordenite and erionite, perlite, clay minerals such as acid clay and activated clay, porous glass, magnesium silicate , Aluminum silicate, polymer adsorbent, activated carbon, activated carbon fiber, molecular sieving carbon, bone charcoal, calcium oxide, barium oxide, calcium chloride, barium bromide, calcium bromide,
Zinc bromide, calcium sulfate, magnesium chloride, magnesium oxide, magnesium sulfate, aluminum sulfate, sodium sulfate, sodium carbonate, potassium carbonate, zinc chloride, magnesium perchlorate, barium perchlorate, lithium perchlorate, sodium hydroxide, Potassium hydroxide and the like are exemplified. Among them, zeolite (natural zeolite, synthetic zeolite), calcium oxide, barium oxide, calcium chloride, magnesium chloride or calcium sulfate having a relatively high drying ability is preferable. As the oxygen scavenger,
Those which do not require moisture for oxygen absorption are preferable, and unsaturated organic compounds such as unsaturated fatty acid compounds and chain hydrocarbon polymers having unsaturated groups, and thermoplastic polymers such as polyamides and polyolefins as main components, and Oxygen absorbents containing an oxygen absorption promoting substance such as a metal salt are exemplified, and in particular, an oxygen absorbing substance containing an unsaturated fatty acid compound and / or a chain hydrocarbon polymer having an unsaturated group as a main component and containing an oxygen absorption promoting substance is exemplified. Agents are preferred. Examples of the organic gas absorbent include activated carbon, synthetic zeolites such as molecular sieves, and natural zeolites such as mordenite and erionite.

[0013] The getter for vacuum heat insulating material of the present invention, a dehumidifier,
The oxygen scavenger and the organic gas absorbent may be used as a mixture, or may be used separately in different states. These are, as appropriate,
It is used in the form of powder, granules, tablets, sheets and the like.
Although they may be used without being wrapped in a packaging material, they are usually used as a package packaged with a breathable packaging material for easy handling. The form of the package is not particularly limited, but depending on the purpose,
A pouch, sheet, or blister-packed form is selected.

[0014]

The present invention will be described below in more detail with reference to specific examples of the present invention. The present invention is not limited to the embodiments. The thermal conductivity was measured using an HC-070 type thermal conductivity meter manufactured by Eiko Seiki Co., Ltd.

Example 1 In a glove box in which calcium oxide as a reagent was replaced with nitrogen to a carbon dioxide gas concentration of 0.1 ppm or less using a mortar, pulverized, and sieved using a 120-mesh and a 200-mesh sieve. 100 μm diameter calcium oxide was obtained. Here, the average value of the openings of the sieved screen was defined as the average particle size. 5 g of calcium oxide having an average particle diameter of 100 μm was placed in a packaging bag (PET 12 μm
/ PE 30 μm, inner size: 5 cm × 5 cm, air permeability of densometer 20 seconds) and heat-sealed to obtain a small bag package. Foamed polyurethane (200 × 200 × 20t) consisting of this small bag package and open cells dried at 120 ° C. for 2 hours
mm) was converted to aluminum-deposited polyethylene terephthalate / aluminum foil / polyethylene (12 μm / 12 μm).
m / 80 μm), and in a vacuum packaging apparatus equipped with a heat-sealing apparatus, while evacuating to a vacuum of 0.01 Torr, open the opening of the gas barrier container for vacuum heat insulating material. Heat sealing was carried out to obtain a vacuum heat insulating material of 200 × 200 × 20 tmm. This vacuum insulating material is placed in an atmosphere of 40 ° C. and 90% RH for 9 hours.
Table 1 shows the results of measuring the thermal conductivity after leaving for 0 days.

Example 2 Barium oxide as a reagent was ground in the same manner as in Example 1 to obtain barium oxide having an average particle diameter of 100 μm. Example 1 was replaced with 5 g of barium oxide having an average particle size of 100 μm in place of 5 g of calcium oxide having an average particle size of 100 μm.
In the same manner as in Example 1, a small bag package was produced, and further, a vacuum heat insulating material was produced using the same, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Example 3 In place of 5 g of calcium oxide having an average particle diameter of 100 μm in Example 1, calcium oxide 4 having an average particle diameter of 100 μm was used.
g and calcium hydroxide as a reagent were pulverized in the same manner as in Example 1, and 1 g of calcium hydroxide having an average particle diameter of 100 μm was mixed and used. Example 1 was prepared by using a vacuum heat insulating material.
The same measurement was performed. Table 1 shows the results.

EXAMPLE 4 10 parts by weight of molecular sieves 13X in a mixture of 3 parts by weight of soybean oil as a main component of an oxygen absorbent that does not require moisture for oxygen absorption and 0.06 parts by weight of cobalt naphthenate as an oxygen absorption promoting substance In addition, after mixing with a blender, the mixture was allowed to stand at 25 ° C. for 10 minutes to obtain a fluid granular material. After mixing 2 g of the oxygen absorbent powder A with 5 g of calcium oxide having an average particle size of 100 μm, a packaging bag having fine vents (PET 12 μm / PE 30 μm, inner size: 5 cm × 5 c)
m, densometer air permeability: 20 seconds) and heat-sealed to obtain a small bag package. Using this small bag package instead of the small bag package of Example 1, a vacuum heat insulating material was produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Example 5 Using a ball mill (HM type) manufactured by Miki Seisakusho Co., Ltd., 50 kg of granular calcium oxide was charged, and the concentration of carbon dioxide was reduced to 0.1 ppm or less by flowing nitrogen, and then the average particle diameter was reduced to 100 μm. Grinding was performed. Instead of 5 g of calcium oxide having an average particle diameter of 100 μm in Example 1, 5 g of the pulverized calcium oxide was used to prepare a small bag packaging bag in exactly the same manner as in Example 1, and further used for vacuum insulation. And the same measurement as in Example 1 was performed. Table 1 shows the results.

Comparative Example 1 A small bag package was produced in the same manner as in Example 1 except that 5 g of calcium oxide having an average particle diameter of 100 μm was not used, and a vacuum heat insulating material was produced using the same. The same measurement as in Example 1 was performed. Table 1 shows the results.

Comparative Example 2 5 g of calcium oxide having an average particle size of 100 μm of Example 1 was sieved through 20 mesh and 40 mesh to obtain an average particle size of 6 μm.
A small bag package was produced exactly in the same manner as in Example 1 except that calcium oxide of 00 μm was used, and a vacuum heat insulating material was produced using the same, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Comparative Example 3 5 g of calcium oxide having an average particle diameter of 100 μm of Example 1 was sieved through 20 mesh and 40 mesh, and the average particle diameter was 6
Example 1 except that 5 g of 00 μm calcium hydroxide was used.
In the same manner as in Example 1, a small bag package was produced, and further, a vacuum heat insulating material was produced using the same, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Comparative Example 4 A small bag package was prepared in exactly the same manner as in Example 1 except that 5 g of calcium oxide having an average particle diameter of 100 μm in Example 1 was replaced with molecular sieves 13X and 5 g as reagents. To produce a vacuum heat insulating material, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Comparative Example 5 Example 1 was repeated except that the pulverization of calcium oxide in Example 1 was performed in the air instead of pulverization in a glove box.
In the same manner as in Example 1, a small bag packaging bag was produced, and further, a vacuum heat insulating material was produced therefrom, and the same measurement as in Example 1 was performed. Table 1 shows the results.

Example 6 Calcium oxide having an average particle size of 100 μm produced in Comparative Example 5 was heated at 1000 ° C. in an electric furnace, and then allowed to cool to room temperature under a nitrogen stream. This fired average particle size of 100μ
A small pouch packaging bag was produced in exactly the same manner as in Example 1 using 5 g of calcium oxide m, and a vacuum heat insulating material was produced using the same, and the same measurement as in Example 1 was performed. Table 1 shows the results.

[0026]

[Table 1]

[0027]

According to the present invention, the getter for vacuum heat insulating material is pulverized to an average particle size of 150 μm or less in a low carbon dioxide concentration atmosphere or pulverized to a particle size of 150 μm or less, and then fired at a temperature or higher at which carbonates are decomposed. By using alkali metal hydroxide and alkaline earth metal oxide and hydroxide, which are manufactured by cooling in a carbon dioxide concentration atmosphere, carbon dioxide gas, which is the main cause of lowering the degree of vacuum, is efficiently absorbed. However, this makes it possible to maintain the vacuum insulating material at a low pressure for a long period of time, and its practical effect is extremely large.

Claims (4)

[Claims] 1. A getter for inserting a urethane foam core material into an airtight container, applying a high vacuum to the inside, and then placing the getter in a vacuum heat insulating material for sealing, comprising: an oxide of an alkaline earth metal having an average particle size of 150 μm or less; A getter for a vacuum heat insulating material, wherein the getter is any one or more of hydroxides of alkaline earth metals. 2. The getter for a vacuum heat insulating material according to claim 1, wherein the getter to be put into the vacuum heat insulating material is at least one of calcium oxide, calcium hydroxide and barium oxide. 3. The vacuum heat insulating material according to claim 1, wherein the alkaline earth metal oxide or the alkaline earth metal hydroxide is crushed in an atmosphere having a low carbon dioxide gas concentration. Getter manufacturing method. 4. The method according to claim 1, wherein after the alkaline earth metal oxide or the alkaline earth metal hydroxide is crushed in advance, the carbonate present in the surface layer is removed or chemically changed to an oxide or a hydroxide. The method for manufacturing a getter for a vacuum heat insulating material according to claim 1 or 2, wherein