Gas adsorbent, method for producing the same, and vacuum insulating material

Abstract

To provide a gas adsorbent capable of adsorbing argon from a gaseous mixture containing nitrogen, oxygen and argon under normal temperature, a method for producing the same, and a vacuum heat insulation material having the gas adsorbent.SOLUTION: A gas adsorbent adsorbs argon from a gaseous mixture containing nitrogen, oxygen and argon under normal temperature, and contains magnesium ion-changed A type zeolite which is represented by the following formula (1) and has a magnesium ion exchange rate R of 25 to 40%. (1) R(%)={(mol number of magnesium ions in magnesium ion-changed A type zeolite×2) / (total of value obtained by multiplying valence of respective cations by mol number of respective cations contained in magnesium-ion exchanged A type zeolite)}×100.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a gas adsorbent, a method for producing the same, and a vacuum heat insulating material including the gas adsorbent, and particularly relates to a gas adsorbent that adsorbs argon, a method for producing the same, and a vacuum heat insulating material including the gas adsorbent.

Background Art

[0002] In recent years, the movement to promote energy conservation has become active, and there is a demand for a vacuum heat insulating material (VIP) having an excellent heat insulating effect in home appliances and equipment. As a vacuum heat insulating material, a material in which a core material having fine voids such as glass wool or silica powder is covered with an outer covering material having a gas barrier property and the inside of the outer covering material is depressurized and sealed is known. The heat insulation principle of the vacuum heat insulating material is to exclude air that conducts heat as much as possible and reduce heat conduction by gas. Therefore, in order to improve the heat insulation performance of the vacuum heat insulating material, it is necessary to make the internal pressure as low as possible and suppress gas heat conduction due to molecular collisions. In addition, gas generated inside the vacuum heat insulating material and air components that permeate and infiltrate into the vacuum heat insulating material from the outside over time also cause deterioration of the heat insulating performance of the vacuum heat insulating material over time. Therefore, by adsorbing and removing these gases, that is, nitrogen, oxygen, moisture, hydrogen, etc. in the air, it is possible to improve the initial heat insulating performance and maintain the heat insulating performance over time.

[0003] Calcium oxide is known as a typical moisture adsorbent mounted on a vacuum heat insulating material. For example, Patent Document 1 describes a gas adsorbent in which palladium monoxide is dispersed in calcium oxide. Palladium monoxide converts hydrogen into water, and the calcium oxide adsorbs the water, so that it becomes an adsorbent that adsorbs not only moisture but also hydrogen. Patent Document 2 describes a gas adsorbent made of copper ion-exchanged ZSM-5 type zeolite, and it is described that not only the adsorption capacity for nitrogen is improved, but also oxygen, hydrogen, carbon monoxide, and carbon dioxide can be adsorbed. Patent Document 3 describes an adsorbent for hydrogen and carbon monoxide composed of a mixture of cerium oxide, copper oxide, and metallic palladium. In addition, lithium barium is known as a nitrogen adsorbent, and cobalt oxide is known as a hydrogen adsorbent. Thus, while the development of adsorbents for major gas species progresses, argon comes to account for a large proportion among the gas components present inside the vacuum insulation material, and argon adsorption is required for further performance improvement of the vacuum insulation material.

[0004] As adsorbents for argon, in addition to adsorbents that adsorb argon at extremely low temperatures, for example, Patent Document 4 describes silver ion-exchanged zeolite A.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the silver ion-exchanged zeolite A described in Patent Document 4, since silver ions are used as the ion-exchange species, it is necessary to use an expensive silver aqueous solution, which poses a problem in terms of cost. In addition, what is evaluated in the examples is only the adsorption amount of each single gas of oxygen, nitrogen, and argon, and the argon adsorption ability under a mixed gas has not been evaluated. Therefore, an object of the present invention is to provide a gas adsorbent capable of adsorbing argon at room temperature from a gaseous mixture containing nitrogen, oxygen, and argon, a method for producing the same, and a vacuum heat insulating material including the gas adsorbent. **Means for Solving the Problems**

[0007] As a result of intensive studies, the present inventors have found that the above problems can be solved by using a specific A-type zeolite ion-exchanged with magnesium ions at a specific ratio, and have completed the present invention.

[0008] That is, the present invention is as follows. [1] A gas adsorbent for adsorbing argon at room temperature from a gaseous mixture containing nitrogen, oxygen, and argon, including A-type zeolite ion-exchanged with magnesium ions, wherein the magnesium ion-exchanged A-type zeolite has a magnesium ion exchange rate R represented by the following formula (1) of 25 to 40% The gas adsorbent is characterized by the above. Magnesium ion exchange rate R (%) = {(number of moles of magnesium ions contained in the magnesium ion-exchanged A-type zeolite × 2) / (sum of values obtained by multiplying the number of moles of each cation contained in the magnesium ion-exchanged A-type zeolite by the valence of each cation)} × 100 ··· (1) [2] The gas adsorbent according to [1], wherein the magnesium ion-exchanged A-type zeolite contains sodium ions or calcium ions. [3] The gas adsorbent according to [1] or [2], wherein the magnesium ion-exchanged A-type zeolite is in the form of powder, pellets, or tablets. [4] The gas adsorbent according to any one of [1] to [3], further including a moisture adsorbent component and / or another gas adsorbent component other than the magnesium ion-exchanged A-type zeolite. [5] The gas adsorbent according to [4], wherein the moisture adsorbent component and / or the other gas adsorbent component covers the periphery of the magnesium ion-exchanged type A zeolite. [6] A method for producing a gas adsorbent according to any one of [1] to [5], characterized by performing magnesium ion exchange including the following steps (a) to (d). (a) A step of mixing type A zeolite with an aqueous magnesium solution having a predetermined concentration to obtain a mixed solution, (b) A step of refluxing the mixed solution obtained in step (a) at 30 to 99 ° C for 1 to 8 hours in the dark to obtain a residue, and repeating this 1 to 4 times to obtain a residue, (c) After filtering the residue obtained in step (b), a step of washing with water until no magnesium ions remain, and (d) A step of drying the residue washed with water in step (c) at 30 to 120 ° C in air to obtain magnesium ion-exchanged type A zeolite. [7] A vacuum heat insulating material comprising a gas adsorbent according to any one of [1] to [5], a core material, and an outer covering material having gas barrier properties, wherein the gas adsorbent and the core material are covered with the outer covering material, and the inside of the outer covering material is depressurized. [8] The vacuum heat insulating material according to [7], further comprising a moisture adsorbent and / or another gas adsorbent other than the gas adsorbent. [9] The vacuum heat insulating material according to [8], wherein the moisture adsorbent adsorbs moisture faster than the gas adsorbent. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a gas adsorbent capable of adsorbing argon at room temperature from a gaseous mixture containing nitrogen, oxygen and argon, a method for producing the same, and a vacuum heat insulating material including the gas adsorbent. [Brief Description of the Drawings]

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist.

[0012] 〈Gas Adsorbent〉 The gas adsorbent of the present embodiment contains magnesium ion-exchanged A-type zeolite. The magnesium ion-exchanged A-type zeolite has a magnesium ion exchange rate R represented by the following formula (1) of 25 to 40%. Magnesium ion exchange rate R (%) = {(number of moles of magnesium ions contained in magnesium ion-exchanged A-type zeolite × 2) / (sum of values obtained by multiplying the number of moles of each cation contained in magnesium ion-exchanged A-type zeolite by the valence of each cation)} × 100 ··· (1) By containing the above-mentioned magnesium ion-exchanged A-type zeolite, the gas adsorbent of the present embodiment can selectively adsorb more argon than nitrogen and oxygen from a gaseous mixture containing nitrogen, oxygen and argon at normal temperature. As a result, for example, in a vacuum insulation material provided with the gas adsorbent of the present embodiment, it is possible to adsorb argon gas that has permeated and infiltrated as an air component inside the vacuum insulation material and the argon gas initially encapsulated, so that the vacuum retention of the vacuum insulation material can be improved and the long-term performance can be improved. Note that "at normal temperature" means an environment of 20 to 30 °C.

[0013] 〈〈Magnesium Ion-Exchanged Type A Zeolite〉〉 Type A zeolite generally has a chemical composition represented by M 2 / n O·Al2O3·2SiO2·mH2O (M: alkali metal or alkaline earth metal, n: charge of M, m: number of moles of water molecules), and is a porous crystal having a network structure in which SiO4 tetrahedra and AlO4 tetrahedra are three-dimensionally bonded. The charge deficiency of the AlO4 tetrahedron is stabilized by the compensation of alkali metal ions or alkaline earth metal ions. The magnesium ion-exchanged type A zeolite of the present embodiment is a type A zeolite in which part of the alkali metal ions or alkaline earth metal ions encapsulated in the type A zeolite are exchanged with magnesium ions (Mg 2+ ). Examples of the alkali metal ions or alkaline earth metal ions contained in the type A zeolite (part of which are exchanged with magnesium ions) include sodium ions (Na + ), potassium ions (K + ), calcium ions (Ca 2+ ), etc.

[0014] The magnesium ion-exchanged type A zeolite of the present embodiment has a magnesium ion exchange rate R represented by the following formula (1) of 25 to 40%, preferably 28 to 40%, more preferably 30 to 40%. Magnesium ion exchange rate R (%) = {(number of moles of magnesium ions contained in the magnesium ion-exchanged type A zeolite × 2) / (sum of the values obtained by multiplying the number of moles of each cation contained in the magnesium ion-exchanged type A zeolite by the valence of each cation)} × 100 ··· (1) When the magnesium ion exchange rate R is within the above range, the adsorption amount of argon is large, and argon can be selectively adsorbed from a gaseous mixture containing nitrogen, oxygen, and argon at room temperature. Note that the magnesium ion exchange rate R assumes that all the cations before being exchanged with magnesium ions are monovalent cations, and one magnesium ion (Mg 2+) is a calculated value on the premise that it is exchanged. The number of moles of magnesium ions and all cations contained in the magnesium ion-exchanged zeolite A can be determined by X-ray fluorescence analysis, and specifically, it can be determined by the method described in the examples below. The magnesium ion exchange rate R can be adjusted, for example, by adjusting the temperature, time, and number of refluxes in step (b) of the production method described below. If the temperature and time are the same, the magnesium ion exchange rate R increases as the number of refluxes increases.

[0015] The form of the magnesium ion-exchanged zeolite A is not particularly limited, and may be, for example, powder, pellet, or tablet.

[0016] The content of the magnesium ion-exchanged zeolite A in the gas adsorbent of the present embodiment may be, for example, 1 to 100% by mass, 1 to 50% by mass, or 3 to 20% by mass.

[0017] The gas adsorbent of the present embodiment may further contain a moisture adsorbent component and / or other gas adsorbent components other than the above-mentioned magnesium ion-exchanged zeolite A. The moisture adsorbent component is not particularly limited, and examples thereof include calcium oxide, calcium chloride, aluminum oxide, silica gel, molecular sieves, zeolites, etc. Among them, it is particularly preferable that the moisture adsorbent component (such as calcium oxide and zeolite) adsorbs moisture faster (has high moisture adsorption performance) than the magnesium ion-exchanged zeolite A. Although the magnesium ion-exchanged zeolite A adsorbs a certain amount of moisture, when a moisture adsorbent component that adsorbs moisture faster is contained, the amount of moisture adsorbed by the magnesium ion-exchanged zeolite A is reduced, and there is a tendency to adsorb more argon efficiently. The other gas adsorbent components are not particularly limited, and examples thereof include lithium barium, cobalt oxide, Cu-ZSM5 zeolite, etc. The above moisture adsorbent component and other gas adsorbent components may each be a single type or a combination of two or more types.

[0018] When the gas adsorbent of this embodiment contains a moisture adsorbent component and / or other gas adsorbent components, it may be a mixture containing the moisture adsorbent component and / or other gas adsorbent components. Also, for example, it may be in a state where part or all of the periphery of the A-type zeolite ion-exchanged with magnesium ions by the moisture adsorbent component and / or other gas adsorbent components is covered. When part or all of the periphery of the A-type zeolite ion-exchanged with magnesium ions by the moisture adsorbent component and / or other gas adsorbent components is covered, gases other than moisture and argon are adsorbed first, and the A-type zeolite ion-exchanged with magnesium ions tends to adsorb more argon more efficiently. The content of the moisture adsorbent component in the gas adsorbent of this embodiment may be, for example, 30 to 95% by mass, 40 to 90% by mass, or 50 to 80% by mass. Also, the content of the other gas adsorbent component in the gas adsorbent of this embodiment may be, for example, 1 to 50% by mass, 2 to 40% by mass, or 3 to 30% by mass.

[0019] The gas adsorbent of this embodiment may contain additives such as a binder, alumina, and calcium phosphate for shaping and processing as needed. The content of the additive in the gas adsorbent of this embodiment may be, for example, 40% by mass or less, 35% by mass or less, or 30% by mass or less.

[0020] The form of the gas adsorbent of this embodiment is not particularly limited, and may be, for example, powder, pellet, or tablet. When the gas adsorbent of the present embodiment contains the above-described moisture adsorbent component and / or another gas adsorbent component, it may be in the form of a powder, pellet, or tablet of a mixture containing the moisture adsorbent component and / or another gas adsorbent component. Further, for example, after covering a part or all of the periphery of magnesium ion-exchanged type A zeolite with the moisture adsorbent component and / or another gas adsorbent component, it may be pelletized or tableted (for example, a pellet or tablet having a structure in which a layer of the moisture adsorbent component surrounds magnesium ion-exchanged type A zeolite as a core).

[0021] <Manufacturing Method of Gas Adsorbent> The gas adsorbent of the present embodiment can be manufactured, for example, by a manufacturing method characterized by performing magnesium ion exchange including the following steps (a) to (d). (a) A step of mixing type A zeolite with an aqueous magnesium solution having a predetermined concentration to obtain a mixed solution (b) A step of refluxing the mixed solution obtained in step (a) at 30 to 99 ° C for 1 to 8 hours in the dark to obtain a residue, and performing this 1 to 4 times to obtain a residue (c) A step of filtering the residue obtained in step (b) and then washing with water until no magnesium ions remain, and (d) A step of drying the residue washed with water in step (c) at 30 to 120 ° C in air to obtain magnesium ion-exchanged type A zeolite

[0022] In step (a), type A zeolite is mixed with an aqueous magnesium solution having a predetermined concentration to obtain a mixed solution. As the raw materials before exchange with magnesium ions, type A zeolite and an aqueous magnesium solution having a predetermined concentration can be commercially available products. The aqueous magnesium solution is not particularly limited, and examples thereof include aqueous solutions of magnesium compounds such as magnesium nitrate, magnesium acetate, and magnesium chloride. The molar ratio of zeolite A to magnesium (zeolite A:magnesium) is preferably from 1:1 to 1:10, more preferably from 1:3 to 1:10, and even more preferably from 1:3 to 1:5. The "predetermined concentration" of the aqueous magnesium solution may be appropriately determined according to the desired magnesium ion exchange rate R and the reflux conditions in step (b), but is preferably from 0.001 to 0.01 M, more preferably from 0.002 to 0.008 M, and even more preferably from 0.003 to 0.005 M.

[0023] In step (b), the residue is obtained by refluxing the mixture obtained in step (a) at 30 to 99°C for 1 to 8 hours in the dark 1 to 4 times. The reflux temperature and time are more preferably from 60 to 99°C for 4 to 8 hours, and even more preferably 95°C for 6 hours. By adjusting the reflux temperature, time, and number of times, the magnesium ion exchange rate R can be adjusted. At the same reflux temperature and time, the higher the number of refluxes, the higher the magnesium ion exchange rate R. The dark place means a place where the external light is shielded by a shielding object or the like and the illuminance is relatively low, and it does not have to be completely shielded as long as it can block direct sunlight.

[0024] In step (c), after filtering the residue obtained in step (b), it is washed with water until there is no magnesium ion. The filtration method is not particularly limited, and a conventionally known method can be used. It is preferable to use distilled water for the water washing. The state where there is no magnesium ion means the state where it becomes 0 mg / L when inspected by the titanium yellow colorimetric method.

[0025] In step (d), the residue washed with water in step (c) is dried in air at 30 to 120°C. Thereby, magnesium ion-exchanged zeolite A is obtained. The drying temperature is more preferably 50 to 110°C, even more preferably 80 to 100°C. The drying time is not particularly limited.

[0026] The magnesium ion-exchanged A-type zeolite obtained in step (d) is formed into an easily handleable shape such as powdering, pelletizing, or tabletizing under high vacuum or in an inert gas atmosphere without being exposed to nitrogen, water, oxygen, or argon gas, and may be used as it is as the gas adsorbent of the present embodiment. At that time, a binder or the like for molding and processing may be used as necessary. Also, the magnesium ion-exchanged A-type zeolite obtained in step (d) is mixed with the above-described moisture adsorbent component and / or other gas adsorbent components under high vacuum or in an inert gas atmosphere without being exposed to nitrogen, water, oxygen, or argon gas, or a part or all of the periphery of the magnesium ion-exchanged A-type zeolite is covered with the moisture adsorbent component and / or other gas adsorbent components, and then formed into an easily handleable shape such as powdering, pelletizing, or tabletizing, and may be used as the gas adsorbent of the present embodiment. At that time, a binder or the like for molding and processing may be used as necessary. It is desirable to enclose the obtained gas adsorbent in a gas-impermeable container filled with an inert gas and store it until use.

[0027] 〈Vacuum Insulating Material〉 The vacuum insulating material of the present embodiment includes the gas adsorbent of the present embodiment described above, a core material, and an outer covering material having gas barrier properties. The gas adsorbent and the core material are covered with the outer covering material, and the inside of the outer covering material is depressurized. The vacuum insulation material of this embodiment has a reduced-pressure internal space of the gas barrier material having gas barrier properties due to the vacuum evacuation means during manufacturing and the action of the gas adsorbent of this embodiment, and is in a vacuum state (1 to 10 Pa). By including the gas adsorbent of this embodiment, the vacuum insulation material of this embodiment can adsorb argon gas that has flowed into the interior as an atmospheric component and argon gas initially encapsulated therein, thereby improving the vacuum retention property and resulting in a vacuum insulation material with improved long-term performance. The gas adsorbent of this embodiment has provided a way to adsorb all the main gas components that lead to the deterioration of the vacuum insulation material, and by loading an appropriate amount of adsorbent for each gas component, a vacuum insulation material that theoretically does not deteriorate in performance has become achievable.

[0028] 〈〈Core material〉〉 The core material forms the framework of the vacuum insulation material and creates a vacuum space. Examples of the core material include open-cell foams of polymer materials such as polystyrene and polyurethane, open-cell foams of inorganic materials, powders of inorganic and organic compounds (such as silica), inorganic and organic fiber materials (such as glass wool, rock wool, and alumina fiber), and mixtures thereof. Among these, glass wool is preferred because the fiber itself has high elasticity, low thermal conductivity of the fiber itself, and is industrially inexpensive. The above core material may be a single type or a combination of two or more types.

[0029] When the core material is an inorganic and organic fiber material, from the perspective of non-uniform density of the core material, the basis weight is preferably 600 to 10000 g / m 2 and more preferably 1000 to 6000 g / m 2 is. Also, from the perspective of heat insulation performance, the average fiber diameter of the inorganic and organic fiber material is preferably 3 to 12 μm, and more preferably 3 to 4 μm. The inorganic and organic fiber material may contain a binder or the like for forming and processing.

[0030] 〈〈Outer covering material〉〉 The outer covering material serves to isolate the core material from air, moisture, etc. The outer covering material is not particularly limited as long as it has gas barrier properties. For example, metal foils such as aluminum foil and copper foil, films having gas barrier properties (such as films including a metal vapor deposition layer and a transparent silica vapor deposition layer), metal containers, glass containers, gas barrier containers in which a resin and a metal are laminated, and various materials and composite materials capable of inhibiting the intrusion of gas can be mentioned. The outer covering material may be a single type or a combination of two or more types.

[0031] The thickness of the outer covering material (the total thickness in the case of laminating a plurality of materials) is not particularly limited, but from the viewpoints of gas barrier properties and processability, it is preferably 10 μm or more.

[0032] The vacuum insulation material of the present embodiment may further include a moisture adsorbent and / or another gas adsorbent other than the gas adsorbent of the present embodiment. The moisture adsorbent is not particularly limited, and examples thereof include calcium oxide, calcium chloride, aluminum oxide, silica gel, molecular sieves, zeolite, and the like. Among them, a moisture adsorbent (such as calcium oxide and zeolite) that adsorbs moisture faster (has high moisture adsorption performance) than the gas adsorbent of the present embodiment is particularly preferable. Although the gas adsorbent of the present embodiment also adsorbs a certain amount of moisture, if a moisture adsorbent that adsorbs moisture faster is provided, the amount of moisture adsorbed by the gas adsorbent of the present embodiment is reduced, and argon gas can be adsorbed more efficiently. The other gas adsorbent is not particularly limited, and examples thereof include lithium barium, cobalt oxide, Cu-ZSM5 zeolite, and the like. The above moisture adsorbent and other gas adsorbents may be a single type or a combination of two or more types.

[0033] In the vacuum insulation material of the present embodiment, from the viewpoint of efficiently performing gas adsorption, the gas adsorbent, moisture adsorbent, and other gas adsorbents of the above-described present embodiment are preferably each housed in a breathable package. The gas adsorbent, moisture adsorbent, and other gas adsorbents of the present embodiment contained in the package may be only one or a plurality of each.

[0034] The size of the vacuum insulation material of the present embodiment is not particularly limited and may be appropriately set according to the purpose.

[0035] 〈Method for manufacturing vacuum insulation material〉 The vacuum insulation material of the present embodiment can be manufactured, for example, by the following method. The gas adsorbent of the present embodiment and, if necessary, the moisture adsorbent and other gas adsorbents are each stored in a breathable package. Next, the core material and each adsorbent are stored in an outer covering material, and the inside of the outer covering material is decompressed and sealed to obtain a vacuum insulation material. The inside of the outer covering material is preferably decompressed to an ultra-high vacuum state (1 to 2 Pa) by a vacuum chamber or the like. Also, the time from when each gas adsorbent is exposed to the atmosphere until the inside of the outer covering material is made into a vacuum state is preferably within 15 minutes.

Examples

[0036] Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0037] The measurement and evaluation methods used in the examples and comparative examples are as follows.

[0038] [Argon adsorption amount] Using a volumetric adsorption apparatus, the adsorption amount (mL / g) of argon to the gas adsorbent at 30 °C was measured.

[0039] [Accelerated evaluation (thermal conductivity)] The vacuum insulation material was placed in a 90 °C atmosphere for 2 months to conduct an accelerated test. Using a heat flow meter (“HC-074” manufactured by Eihong Seiki Co., Ltd.), the change in the thermal conductivity (mW / m·K) of the vacuum insulation material was measured.

[0040] [Internal gas analysis (argon amount)] The vacuum insulation material was placed in a 90°C atmosphere for 7 days, and an accelerated test was carried out. After the accelerated test, a hole was made in the vacuum insulation material in a sealed system at 23°C to suck out the gas inside the vacuum insulation material, and the amount of argon was measured using a gas chromatograph mass spectrometer ("Gulee" manufactured by ULVAC, Inc.).

[0041] [Example A1] 10 g of synthetic type A zeolite ("A-4" manufactured by FUJIFILM Wako Pure Chemical Corporation) was mixed with 500 mL of a 0.003 M aqueous solution of Mg(NO3)2·6H2O (99%, manufactured by FUJIFILM Wako Pure Chemical Corporation) to obtain a mixed solution. The obtained mixed solution was refluxed in the dark at 95°C for 6 hours to obtain a residue. This reflux was carried out once. After filtering the obtained residue, it was washed with distilled water until the magnesium ions disappeared. The disappearance of magnesium ions was judged by inspection with the titanium yellow colorimetric method and the fact that no detection was made. The washed residue was dried in air at 90°C to obtain 10 g of powdery magnesium ion-exchanged type A zeolite. The obtained magnesium ion-exchanged type A zeolite was used as a gas adsorbent as it was. The magnesium ion exchange rate R of the magnesium ion-exchanged type A zeolite is shown in Table 1. Also, the measurement results of the argon adsorption amount of the gas adsorbent are shown in Figure 1.

[0042] [Examples A2, A3, Comparative Examples A1 to A3] Magnesium ion-exchanged type A zeolite was produced and used as a gas adsorbent in the same manner as in Example A1 except that the reflux conditions were changed as shown in Table 1. For each example, the magnesium ion exchange rate R of the magnesium ion-exchanged type A zeolite is shown in Table 1. Also, the measurement results of the argon adsorption amount of the gas adsorbent are shown in Figure 1.

[0043]

Table 1

[0044] From the measurement results of the argon adsorption amount of the gas adsorbent shown in Fig. 1, it can be seen that the argon adsorption amount of Example A1 with a magnesium ion exchange rate R of 34% is extremely high. This suggests that the pore volume of the type A zeolite when the magnesium ion exchange rate R is around 34% is optimal for argon adsorption.

[0045] [Example B1] The following vacuum insulation material (180 mm × 180 mm × thickness 18 mm, density: 210 kg / m 3 ) was manufactured, which includes an adsorbent, a core material, and an outer covering material having gas barrier properties. (Adsorbent) · 1 g of the gas adsorbent obtained in Example A1 · 10 g of a moisture adsorbent (calcium oxide) · 1 nitrogen gas adsorbent (「COMB3」manufactured by SAES Getters, Φ30 mm) (Core material) · An aggregate of short fiber glass wool (180 mm × 180 mm × thickness, basis weight: 1590 g / m 2 laminated in two layers, average fiber diameter: 4 μm) (Outer covering material having gas barrier properties) · Aluminum foil film (180 mm × 180 mm × thickness 94 μm): A laminated film obtained by laminating a surface protection layer (stretched nylon, thickness 25 μm), a base material (polyethylene terephthalate film, thickness 12 μm), a gas barrier layer (aluminum foil, thickness 7 μm), and a heat seal layer (polyethylene film, thickness 50 μm) in this order and dry laminating and bonding them. · Aluminum vapor-deposited film (180 mm × 180 mm × thickness 99 μm): A laminated film obtained by laminating a surface protection layer (stretched nylon, thickness 25 μm), a gas barrier layer (silica alumina vapor-deposited polyethylene terephthalate film, thickness 12 μm), a gas barrier layer (aluminum vapor-deposited ethylene-vinyl alcohol copolymer (EVOH) film, thickness 12 μm), and a heat seal layer (polyethylene film, thickness 50 μm) in this order and dry laminating and bonding them. First, the gas adsorbent, moisture adsorbent, and nitrogen gas adsorbent obtained in Example A1 were separately stored in a breathable package. Next, after placing an aluminum vapor-deposited film with the surface protection layer on the bottom surface, glass wool was placed in the center of the aluminum vapor-deposited film, and each adsorbent (arranged so that the adsorbents do not overlap), and an aluminum foil film with the surface protection layer on the top surface were laminated in this order to obtain a laminate. Subsequently, the laminate was placed in a vacuum chamber, the four sides of the aluminum vapor-deposited film (the parts where the glass wool, each adsorbent, and the aluminum foil film were not laminated) were bent upward and overlapped on the aluminum foil film, and the overlapped part was heat-sealed and then taken out from the vacuum chamber to obtain a vacuum insulation material in which the glass wool and each adsorbent were enclosed by the aluminum vapor-deposited film and the aluminum foil film. Note that the time from exposing each adsorbent to the atmosphere until it was in a vacuum state inside the outer material was within 15 minutes. The measurement results of the thermal conductivity during the acceleration test are shown in FIG. 2, and the measurement results of the amount of argon contained inside the vacuum insulation material are shown in FIG. 3.

[0046] [Comparative Example B1] A vacuum insulation material was manufactured in the same manner as in Example B1 except that the gas adsorbent obtained in Example A1 was not mounted. The measurement results of the thermal conductivity during the acceleration test are shown in FIG. 2, and the measurement results of the amount of argon contained inside the vacuum insulation material are shown in FIG. 3.

[0047] From the measurement results of the thermal conductivity during the acceleration test of the vacuum insulation material shown in FIG. 2, Example B1 equipped with the gas adsorbent obtained in Example A1 has a smaller acceleration (increase in thermal conductivity) slope compared to Comparative Example B1 not equipped with the same gas adsorbent. It can be seen that the pressure rise inside the vacuum insulation material is gentle and the durability is improved. Also, from the measurement results of the amount of argon contained inside the vacuum insulation material shown in FIG. 3, in Example B1 equipped with the gas adsorbent obtained in Example A1, the amount of argon inside the vacuum insulation material is less compared to Comparative Example B1 not equipped with the same gas adsorbent, and it was confirmed that argon was adsorbed by the gas adsorbent obtained in Example A1.

Industrial Applicability

[0048] Since the gas adsorbent of the present invention can adsorb argon at room temperature from a gaseous mixture containing nitrogen, oxygen, and argon, it can be suitably used for a vacuum insulation material. Further, the vacuum insulation material of the present invention can be applied to all heat insulation applications such as refrigerators, freezers, water heaters, automotive heat insulation materials, building heat insulation materials, vending machines, cold storage boxes, cold storage rooms, refrigerated trucks, etc.

Claims

1. A gas adsorbent that adsorbs argon at room temperature from a gaseous mixture containing nitrogen, oxygen, and argon, including magnesium ion-exchanged A-type zeolite, wherein the magnesium ion-exchanged A-type zeolite has a magnesium ion exchange rate R represented by the following formula (1) of 25 to 40% characterized by being a gas adsorbent. Magnesium ion exchange rate R (%) = { (number of moles of magnesium ions contained in the magnesium ion-exchanged A-type zeolite × 2) / (sum of values obtained by multiplying the number of moles of each cation contained in the magnesium ion-exchanged A-type zeolite by the valence of each cation)} × 100... (1)

2. The gas adsorbent according to claim 1, wherein the magnesium ion-exchanged A-type zeolite contains sodium ions or calcium ions.

3. The gas adsorbent according to claim 1, wherein the magnesium ion-exchanged A-type zeolite is in the form of powder, pellets, or tablets.

4. The gas adsorbent according to claim 1, further comprising a moisture adsorbent component and / or another gas adsorbent component other than the magnesium ion-exchanged A-type zeolite.

5. The gas adsorbent according to claim 4, wherein the moisture adsorbent component and / or the other gas adsorbent component covers the periphery of the magnesium ion-exchanged A-type zeolite.

6. A method for producing the gas adsorbent according to any one of claims 1 to 5, characterized by performing magnesium ion exchange including the following steps (a) to (d). (a) A step of mixing A-type zeolite with an aqueous magnesium solution having a predetermined concentration to obtain a mixed solution, (b) A step of refluxing the mixed solution obtained in step (a) at 30 to 99 °C for 1 to 8 hours in the dark 1 to 4 times to obtain a residue, (c) A step of filtering the residue obtained in step (b) and then washing with water until no magnesium ions remain, and (d) A step of drying the residue washed with water in step (c) in air at 30 to 120 °C to obtain magnesium ion-exchanged A-type zeolite.

7. A vacuum insulation material comprising the gas adsorbent according to any one of claims 1 to 5, a core material, and an outer covering material having gas barrier properties, wherein the gas adsorbent and the core material are covered with the outer covering material, and the inside of the outer covering material is depressurized.

8. The vacuum insulation material according to claim 7, further comprising a moisture adsorbent and / or another gas adsorbent other than the gas adsorbent.

9. The vacuum insulation material according to claim 8, wherein the moisture adsorbent adsorbs moisture faster than the gas adsorbent.

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