JP2017000906A - Gas adsorbent, and vacuum heat insulation material prepared therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a gas adsorbent that is safe although it does not require activation at high temperature, and has excellent adsorptivity on a target gas even under a decompression environment.SOLUTION: A gas adsorbent has calcium oxide with an average primary particle size of 1 μm or less and a specific surface of less than 10 m/g, and palladium monoxide dispersed in the calcium oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas adsorbent and a vacuum heat insulating material using the same, and in particular, a gas adsorbent capable of adsorbing a target gas in a reduced pressure environment, and the gas adsorbent in a gas barrier resin film. It is related with the accommodated vacuum heat insulating material.

  Recently, a movement to promote energy saving has been activated, and a vacuum heat insulating material having an excellent heat insulating effect has been demanded for home appliances and equipment. As a vacuum heat insulating material, a core material having a fine void such as glass wool or silica powder is covered with an exterior material having a gas barrier property, and the inside of the exterior material is sealed under reduced pressure. In order to maintain the excellent thermal insulation effect of the vacuum insulation material over a long period of time, a gas adsorbent for removing gases such as water vapor, oxygen, and nitrogen that penetrates the vacuum insulation material is sealed together with the core material in a vacuum insulation material. Yes.

  As a gas adsorbent, a chemical adsorbent that irreversibly fixes and adsorbs moisture is known. Calcium oxide CaO is an example of this. On the other hand, moisture adsorbents such as calcium oxide do not have adsorbability with respect to oxygen and nitrogen in the air that permeate the vacuum insulation material. Therefore, an adsorbent for these gases is necessary to maintain a reduced pressure state in a vacuum insulation environment.

  Metal adsorbents made of barium getters or zirconium-vanadium-iron ternary alloys are known as materials that exhibit adsorption capacity for oxygen and nitrogen. Since the metal adsorbent needs to be activated at a high temperature of 400 ° C. or higher in a reduced pressure environment, a vacuum heat insulating material is often constructed using an exterior material in which a plastic film and a metal foil are multilayered. Then, since the exterior material melts and breaks, the metal adsorbent cannot be activated in the first place.

  On the other hand, as a gas adsorbing material that does not need to be activated in advance, for example, there is a nitrogen / oxygen adsorbing Ba—Li alloy. Patent Document 1 describes a vacuum heat insulating material using a Ba-Li alloy as a getter material for nitrogen and oxygen. In Patent Document 1, an attempt is made to lengthen the time during which the getter material can be left in the atmosphere by mixing a Ba—Li alloy and a moisture adsorbing material.

JP-A-1996-159377

  When used home appliances are crushed, the gas adsorbent is crushed together with the vacuum heat insulating material to expose the Ba-Li alloy. When water is sprayed to suppress the generation of dust during crushing, the Ba-Li alloy has a very high reactivity with water, so a large amount of hydrogen gas is generated at once. Therefore, the Ba—Li alloy has not come into wide use as one that can be put into practical use from the viewpoint of safety.

  Therefore, the problem of the present disclosure is to realize a gas adsorbent that is safe even though activation at a high temperature is unnecessary, and that has excellent adsorption performance for a target gas even under a reduced pressure environment, and a vacuum heat insulating material using the same. Is to be able to do it.

One aspect of the gas adsorbent of the present disclosure includes calcium oxide having an average primary particle diameter of 1 μm or less and a specific surface area of less than 10 m ² / g, and palladium monoxide dispersed in calcium oxide.

  In one embodiment of the gas adsorbent, the concentration of palladium monoxide with respect to the calcium oxide can be 0.001 wt% or more and 2.5 wt% or less.

One aspect of the vacuum heat insulating material of the present disclosure includes the gas adsorbing material of the present disclosure and an exterior material enclosing the gas adsorbing material and sealed in a vacuum, and the gas adsorbing material has an oxygen gas permeability of 16 g. / M ² · 24h · 1 atm or less.

  In one embodiment of the vacuum heat insulating material, the nonwoven fabric can be any one of polyethylene, polypropylene, and polyethylene terephthalate, or a combination thereof.

One aspect of the vacuum heat insulating material can satisfy the following formula 1.
(Kc ₃₀ / Kc ₁ −1) × 100 <3% 3 Formula 1
However, Kc ₁ is the thermal conductivity of the vacuum heat insulating material formed with the contact time between the gas adsorbent and the atmosphere being less than 1 minute, and Kc ₃₀ is the vacuum formed with the contact time between the gas adsorbent and the air being 30 minutes. This is the thermal conductivity of the heat insulating material.

  According to the present disclosure, it is possible to realize a gas adsorbent that is safe even if activation at a high temperature is unnecessary, and that has excellent adsorption performance for a target gas even under a reduced pressure environment, and a vacuum heat insulating material using the same.

It is a schematic cross section which shows an example of the vacuum heat insulating material of this invention. It is a graph which shows the relationship between the dispersion concentration of palladium monoxide, and thermal conductivity. It is a graph which shows the relationship between the specific surface area of calcium oxide, and the change rate of thermal conductivity. It is a graph which shows the relationship between the specific surface area of a calcium oxide, and the hydrogen partial pressure after an acceleration test.

  The gas adsorption material of this indication can be used for a vacuum heat insulating material. A vacuum heat insulating material can cover the core material which has fine voids, such as glass wool or a silica powder, for example with the exterior material which has gas barrier property, and the inside of an exterior material can be sealed under reduced pressure. A vacuum heat insulating material can be used for a refrigerator, a freezer, a hot water supply container, a heat insulating material for cars, a heat insulating material for buildings, a vending machine, a cold box, a heat insulating box, a cold car, and the like.

  FIG. 1 is a schematic cross-sectional view showing an example of the vacuum heat insulating material 1. As shown in FIG. 1, the vacuum heat insulating material 1 according to the present invention is configured so as to be enclosed and sealed so that a core material 6 and an adsorbent material 7 are sandwiched between two exterior materials.

  The vacuum heat insulating material 1 can be manufactured as follows, for example. First, the periphery of the two exterior materials 2 is sealed (for example, heat-sealed), leaving an open end, and is formed into a bag-like form as a whole. After the core material 6 and the adsorbent material 7 are accommodated inside the bag-shaped exterior material 2, the inside is decompressed to seal the opening (for example, heat seal). In FIG. 1, a portion indicated by reference numeral 8 is a joint where the opening is sealed.

The adsorbent 7 can be a gas adsorbent housed in a bag made of nonwoven fabric or the like. The gas adsorbent has calcium oxide (CaO) having an average primary particle diameter of 1 μm or less and a specific surface area of less than 10 m ² / g, and palladium monoxide (PdO) dispersed in calcium oxide.
As a result of intensive studies by the present inventors, it has been found that main gases remaining in the vacuum heat insulating material containing only the moisture adsorbing material are nitrogen, hydrogen, oxygen, and carbon dioxide. Hydrogen is a gas having a higher thermal conductivity than nitrogen, oxygen, and water, and greatly affects the deterioration of thermal conductivity by being present in the vacuum heat insulating material. Therefore, the performance improvement of a vacuum heat insulating material can be expected by removing hydrogen with an adsorbent.

  Palladium monoxide converts hydrogen to water. For this reason, it is expected that an adsorbent capable of removing not only moisture but also hydrogen can be obtained by combining the moisture adsorbent and palladium monoxide into a gas adsorbent.

  Even if palladium monoxide is accommodated in the vacuum heat insulating material separately from the moisture adsorbing material, hydrogen can be converted into water and adsorbed on the moisture adsorbing material. However, it is preferable that the moisture adsorbing material surrounds the palladium monoxide because moisture converted from hydrogen by the palladium monoxide can be absorbed quickly. In particular, it is preferable that palladium monoxide particles are dispersed in the moisture adsorbent particles because the contact between palladium monoxide and hydrogen is likely to occur and the generated water is easily adsorbed.

  Although palladium monoxide is not particularly limited, palladium monoxide having an average particle diameter of about 0.1 μm to 100 μm is preferable from the viewpoint of increasing the contact area with hydrogen.

The moisture adsorbent is preferably an alkaline earth oxide which is a chemical moisture adsorbent, and calcium oxide is particularly preferred in terms of cost. Calcium oxide is expected to adsorb moisture more easily when the specific surface area is larger. However, as a result of studies by the present inventors, it has been clarified that the specific surface area should be small to some extent when hydrogen is also removed in combination with palladium monoxide. Specifically, by making the specific surface area of calcium oxide less than 10 m ² / g, the hydrogen concentration inside the vacuum heat insulating material can be greatly reduced as compared with the case of using calcium oxide having a large specific surface area. The specific surface area of calcium oxide can be measured by the BET method. In order to obtain calcium oxide having such a specific surface area, the average primary particle diameter of calcium oxide is preferably 1 μm or less. Moreover, it is preferable that an average secondary particle diameter is 100 micrometers or less.

  The moisture adsorbing material may be used by mixing calcium oxide with other materials. For example, an alkaline earth oxide other than calcium oxide may be mixed. As an alkaline earth oxide other than calcium oxide, for example, at least one of magnesium oxide, strontium oxide, barium oxide, and the like can be used.

  A physical moisture adsorbent can also be mixed. As the physical moisture adsorbing material, for example, at least one of zeolite, alumina, silica gel and the like can be used, and among them, zeolite is preferable. The zeolite is not particularly limited, but is a hydrophobic zeolite, which is composed of a porous crystalline aluminosilicate, and the silica to alumina ratio (Si / Al) in the zeolite framework is 1-1500, preferably 5-1000, more preferably Can use what is 5.5-500.

  The dispersion concentration of palladium monoxide with respect to calcium oxide is not particularly limited, but from the viewpoint of improving the thermal conductivity by reducing the hydrogen concentration in the vacuum heat insulating material, 0.001 wt% or more is preferable, and 0.01 wt% or more is preferable. More preferred is 0.05 wt% or more. Moreover, 2.5 wt% or less is preferable from a viewpoint of cost, and 1 wt% or less is more preferable. FIG. 2 shows the relationship between the dispersion concentration of palladium monoxide with respect to calcium oxide and the thermal conductivity immediately after forming the vacuum heat insulating material. In FIG. 2, the vertical axis indicates the thermal conductivity normalized by assuming that the thermal conductivity is 1 when an adsorbent not containing palladium monoxide is used. Even when the dispersion concentration is 0.001 wt%, the thermal conductivity is sufficiently lowered as compared with the case of only calcium oxide.

The gas adsorbent in which palladium monoxide is dispersed in calcium oxide is preferably housed in a bag-like container made of a resin nonwoven fabric from the viewpoint of efficiently adsorbing gas. The nonwoven fabric preferably has an oxygen gas permeability of 16 g / m ² · 24 h · 1 atm or less. By using a nonwoven fabric having such characteristics, the gas adsorbent can be made difficult to come into contact with oxygen, and the gas adsorbent can be hardly deteriorated by oxygen. The nonwoven fabric having such characteristics can be formed of, for example, one kind of polyethylene, polypropylene, polyethylene terephthalate, or a mixture thereof.

Depending on the components of the gas adsorbent, there is a risk that it will rapidly deteriorate due to various components in the atmosphere. However, a gas adsorbent in which palladium monoxide is dispersed in calcium oxide is unlikely to rapidly deteriorate in the atmosphere. Specifically, when the gas adsorbent with a contact time with the atmosphere of less than 1 minute is disposed in the vacuum heat insulating material, and when the gas adsorbent in contact with the air for 30 minutes is disposed in the vacuum heat insulating material The rate of change in thermal conductivity R _kc = (Kc ₃₀ / Kc ₁ −1) × 100 is less than 3%. However, Kc ₁ is the thermal conductivity when a gas adsorbent with a contact time with the atmosphere of less than 1 minute is placed in the vacuum heat insulating material, and Kc ₃₀ is a vacuum for the gas adsorbent that has been in contact with the atmosphere for 30 minutes. It is a heat conductivity at the time of arrange | positioning in a heat insulating material.

  By maintaining the vacuum heat insulating material in a reduced pressure state, nitrogen may permeate the exterior material. In addition, the exterior material may release nitrogen. In order to reduce the influence of such nitrogen, the gas adsorbent further includes a nitrogen adsorbent such as a copper ion-exchanged zeolite, a lithium-barium getter, or a metal adsorbent made of zirconium-vanadium-iron ternary alloy. It can also be set as a structure.

  As the exterior material 2, various materials and composite materials that have gas barrier properties and can suppress gas intrusion can be used. Generally, the exterior material 2 can be made by laminating a thermoplastic resin film and a metal foil to give a barrier property, and plays a role of isolating the core material 6 from air and moisture.

  FIG. 1 shows an exterior material 2 in which a heat melting layer (thermal welding film) 5, a gas barrier layer (gas barrier film) 4, and a surface protective layer (surface protective film) 3 are sequentially laminated.

  The heat-welded film 5 is a solidified material after the heat-welded layer of the exterior material 2 is melted by heat and pressure, and plays a role of holding the exterior material 2 in a predetermined shape. Also, it plays a role of suppressing the gas from entering the vacuum heat insulating material 1 from the end of the exterior material 2.

  The heat welding film 5 is not particularly limited as long as it can be bonded by a normal sealing method (for example, heat sealing). Examples of the material constituting the heat welding film include polyolefins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and polypropylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, and ethylene. -Acrylic ester copolymer, ethylene-acrylic ester copolymer, and thermoplastic resins such as polyacrylonitrile. In addition, the said material can be used individually or can be used in mixture of 2 or more types. Moreover, the heat welding film 5 can be made into a single layer, or can be made into the laminated body of two or more layers. When it is set as a laminated body, each layer can be set as the structure which has the same composition, and can also be set as the structure which has a different composition.

  The thickness of the heat welding film 5 is preferably 10 μm or more from the viewpoint of obtaining sufficient adhesion strength during heat sealing, and is preferably 100 μm or less from the viewpoint of workability such as flexibility. However, there is no particular limitation as long as the exterior material 2 can be welded. In addition, when the heat welding film 5 has a laminated structure, the thickness of the heat welding film 5 is a total thickness. Moreover, when the heat welding film 5 has a laminated structure, the thickness of each layer can be made all the same, or at least one can be made different. It can be a single layer or a laminate of two or more layers.

  The gas barrier film 4 is not particularly limited as long as it has a required gas barrier property, and various types can be used. For example, a metal foil such as an aluminum foil or a copper foil, a polyethylene terephthalate film or a film obtained by vapor-depositing a metal material such as aluminum or copper or a metal oxide material such as alumina or silica on an ethylene-vinyl alcohol copolymer is used. be able to. The thickness of the gas barrier film is not particularly limited. The gas barrier film 4 can be a single layer or a laminate of two or more layers.

  The surface protective film 3 is not particularly limited, and the surface protective film 3 that is usually used as a surface protective film for an exterior material can be used. Examples of the material constituting the surface protective film include polyamide (PA) such as nylon-6 or nylon-66, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyester such as polybutylene terephthalate (PBT). Polyolefin such as polyethylene (PE), polypropylene (PP) or polystyrene (PS), polyimide, polyacrylate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), ethylene vinyl alcohol copolymer (EVOH), polyvinyl Examples include alcohol resin (PVA), polycarbonate (PC), polyether sulfone (PES), polymethyl methacrylate (PMMA), and polyacrylonitrile resin (PAN).

  The thickness of the surface protective film 3 is preferably 10 μm or more from the viewpoint of protection of the gas barrier film 4, and is preferably 100 μm or less from the viewpoint of workability such as flexibility. However, the thickness of the surface protective film 3 is not particularly limited. In addition, when the surface protection film 3 has a laminated structure of two or more layers, the surface protection film 3 thickness is a total thickness. Moreover, when the surface protection film 3 has a laminated structure, the thickness of each layer can be made all the same, or at least one can be made different. Each layer may have the same composition or different compositions. Further, the surface protective film 3 may contain at least one of various additives and stabilizers such as an antistatic agent, an ultraviolet ray preventing agent, a plasticizer, and a lubricant.

  The thickness of the exterior material 2 is not particularly limited, but is preferably 1 μm or more and 100 μm or less. With such a thickness, it can be expected that the heat bridge is more effectively suppressed and prevented and the heat insulation performance is improved. Moreover, improvement of gas barrier property and workability can also be expected.

  Moreover, the exterior material 2 made of a gas barrier film can be composed of at least two surfaces: a surface made of a laminate film on which a metal foil is laminated and a surface made of a laminate film on which no metal foil is laminated. In this case, a film layer made of an ethylene-vinyl alcohol copolymer resin composition in which at least the inner layer side is subjected to aluminum vapor deposition, or a polyethylene terephthalate in which aluminum vapor deposition is performed on the inner layer side is a surface made of a laminate film on which no metal foil is laminated. Any one of the film layers made of the resin composition can be provided.

  Moreover, the exterior material 2 may not be a laminate film as described above, and may be, for example, a metal container, a glass container, or a gas barrier container in which a resin and a metal are laminated. As such a plastic laminate film container, a container obtained by laminating one type or two or more types of films such as polyvinylidene chloride, polyvinyl alcohol, polyester, polypropylene, polyamide, polyethylene, and a metal vapor deposition film can be used.

  As shown in FIG. 1, the core material 6 is disposed inside the exterior material. The core material 6 becomes a skeleton of the vacuum heat insulating material 1 and forms a vacuum space. The core material 6 is not specifically limited, A well-known material can be used. Specifically, inorganic fibers such as glass wool, rock wool, alumina fibers, or metal fibers made of metal with low thermal conductivity; manufactured from synthetic fibers such as polyester, polyamide, acrylic, polyolefin, or aramid, and wood pulp Organic fibers such as natural fibers such as cellulose, cotton, hemp, wool or silk, regenerated fibers such as rayon, or semi-synthetic fibers such as acetate can be used. The said core material can be used individually or can be used in mixture of 2 or more types. Among these, glass wool is preferred because the elasticity of the fiber itself is high, the thermal conductivity of the fiber itself is low, and it is industrially inexpensive.

  Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are merely examples and do not limit the present invention.

-Formation of vacuum insulation-
As the exterior material 2, a laminated film obtained by dry-laminating stretched nylon (25 μm), a polyethylene terephthalate film (12 μm), an aluminum foil (7 μm), and a high-density polyethylene film (50 μm) was used. As the core material 6, a laminate of short fiber glass wool having an average fiber diameter of about 4 μm was used. The adsorbent 7 was formed by storing a gas adsorbent prepared by mixing calcium oxide and palladium oxide in a breathable nonwoven fabric (70 mm × 70 mm, manufactured by Yamanaka Sangyo) and sealing in four directions. The adsorbent 7 was prepared in an argon or nitrogen atmosphere having an oxygen concentration of 1 ppm or less. The exterior material 2 containing the core material 6 and the adsorbent 7 was sealed in a vacuum state to form the vacuum heat insulating material 1. The time from when the adsorbent 7 was exposed to the atmosphere until the exterior material 2 was vacuumed was less than 1 minute or 30 minutes. The size of the vacuum heat insulating material 1 was 290 mm × 410 mm × 12 mm. The void space volume of the vacuum heat insulating material 1 was about 1.284L. The void space volume was the product of the vacuum heat insulating material volume and the porosity of the core material.

-Measurement of thermal conductivity-
The thermal conductivity of the vacuum heat insulating material was measured before and after the acceleration test. The thermal conductivity was measured using a heat flow meter (HFM436, manufactured by Netch Japan).

-Evaluation of rate of change of thermal conductivity due to contact with air-
The heat conductivity Kc ₁ of the vacuum heat insulating material manufactured so that the contact time between the prepared gas adsorbent and the atmosphere is less than 1 minute, and the contact time between the gas adsorbent and the atmosphere is 30 minutes. The thermal conductivity Kc ₃₀ of the manufactured vacuum heat insulating material was measured, and the change rate R _Kc (%) of the thermal conductivity was determined by the following formula. R _kc = (Kc ₃₀ / Kc ₁ −1) × 100
-Acceleration test-
The prepared vacuum heat insulating material was placed in an environment that periodically changed from low temperature and low humidity to high temperature and high humidity conditions for one month, and an acceleration test was performed. After the acceleration test, the hydrogen partial pressure of the gas remaining in the vacuum heat insulating material was measured. The hydrogen partial pressure was measured by Q-MS after opening the vacuum heat insulating material in a vacuum chamber.

Example 1
A gas adsorbent was formed by mixing 4.0 g of calcium oxide (manufactured by Yoshizawa Lime) with a BET specific surface area of 2 m ² / g and 1 mg of palladium monoxide (Wako Pure Chemical Industries).

The thermal conductivity Kc ₁ immediately after the formation of the vacuum heat insulating material with the contact time between the gas adsorbent and the atmosphere being less than 1 minute was 2.10 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.11mW / m · K. The change rate R _Kc of the thermal conductivity caused by bringing the gas adsorbent into contact with the atmosphere was 0.5%.

(Example 2)
The same procedure as in Example 1 was performed except that calcium oxide having a BET specific surface area of 4 m ² / g (manufactured by Yoshizawa Lime) was used.

The thermal conductivity Kc ₁ immediately after the formation of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 2.08 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.12mW / m · K. The change rate R _Kc of the thermal conductivity due to the contact of the gas adsorbent with the atmosphere was 1.9%.

  The hydrogen partial pressure after the acceleration test of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 2.9 Pa.

(Example 3)
The same procedure as in Example 1 was performed except that calcium oxide having a BET specific surface area of 5 m ² / g (made by Yoshizawa Lime) was used. The thermal conductivity Kc ₁ immediately after the formation of the vacuum heat insulating material with the contact time between the gas adsorbent and the atmosphere being less than 1 minute was 2.06 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.10mW / m · K. The change rate R _Kc of the thermal conductivity due to the contact of the gas adsorbent with the atmosphere was 1.9%.

  The hydrogen partial pressure after the acceleration test of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 3.1 Pa.

Example 4
The same procedure as in Example 1 was performed except that calcium oxide having a BET specific surface area of 8 m ² / g (manufactured by Yoshizawa Lime) was used. The thermal conductivity Kc ₁ immediately after formation of the vacuum heat insulating material with the contact time between the gas adsorbent and the atmosphere being less than 1 minute was 2.05 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.11mW / m · K. The change rate R _Kc of the thermal conductivity caused by bringing the gas adsorbent into contact with the atmosphere was 2.9%.

  The hydrogen partial pressure after the acceleration test of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 3.3 Pa.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that calcium oxide having a BET specific surface area of 10 m ² / g (manufactured by Yoshizawa Lime) was used. The thermal conductivity Kc ₁ immediately after the formation of the vacuum heat insulating material with the contact time between the gas adsorbent and the atmosphere being less than 1 minute was 2.04 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.26mW / m · K. The change rate R _Kc of the thermal conductivity caused by bringing the gas adsorbent into contact with the atmosphere was 10.8%.

  The hydrogen partial pressure after the acceleration test of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 5.8 Pa.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that calcium oxide having a BET specific surface area of 20 m ² / g (manufactured by Yoshizawa Lime) was used. The thermal conductivity Kc ₁ immediately after the formation of the vacuum heat insulating material with the contact time between the gas adsorbent and the atmosphere being less than 1 minute was 1.98 mW / m · K. Thermal conductivity Kc ₃₀ immediately after the formation of the vacuum heat insulating material having a contact time between the gas adsorbent with the atmosphere and 30 minutes was 2.34mW / m · K. The change rate R _Kc of the thermal conductivity caused by bringing the gas adsorbent into contact with the atmosphere was 18.2%.

  The hydrogen partial pressure after the acceleration test of the vacuum heat insulating material in which the contact time between the gas adsorbent and the atmosphere was less than 1 minute was 5.9 Pa.

  The results of Examples 1 to 4 and Comparative Examples 1 and 2 are collectively shown in Table 1, FIG. 2 and FIG.

DESCRIPTION OF SYMBOLS 1 Vacuum heat insulating material 2 Exterior material 3 Surface protection film 4 Gas barrier film 5 Heat welding film 6 Core material 7 Adsorbent

Claims (5)

Calcium oxide having an average primary particle size of 1 μm or less and a specific surface area of less than 10 m ² / g;
A gas adsorbent comprising palladium monoxide dispersed in the calcium oxide.   The gas adsorbent according to claim 1, wherein a concentration of the palladium monoxide with respect to the calcium oxide is 0.001 wt% or more and 2.5 wt% or less. The gas adsorbent according to claim 1 or 2,
Including the gas adsorbent, and an exterior material hermetically sealed with a vacuum inside,
The gas adsorbent is a vacuum heat insulating material housed in a resin nonwoven fabric having an oxygen gas permeability of 16 g / m ² · 24 h · 1 atm or less.   The vacuum heat insulating material according to claim 3, wherein the resin is any one of polyethylene, polypropylene, and polyethylene terephthalate, or a combination thereof. The vacuum heat insulating material of Claim 3 or 4 which satisfy | fills the following formula | equation 1.
(Kc ₃₀ / Kc ₁ −1) × 100 <3% 3 Formula 1
However, Kc ₁ is the thermal conductivity of the vacuum heat insulating material formed with the contact time between the gas adsorbent and the atmosphere being less than 1 minute, and Kc ₃₀ is the vacuum formed with the contact time between the gas adsorbent and the air being 30 minutes. This is the thermal conductivity of the heat insulating material.