JPH10263388A - Gaseous carbon dioxide adsorbent, foamed heat insulator and heat insulating box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gaseous CO2 adsorbent not deteriorating its gaseous CO2 adsorbing effect with the lapse of time by coating the surface of powder of at least one of an alkali metal hydroxide and an alkaline earth metal hydroxide with a coating film contg. water absorbing powder dispersed in a thermoplastic resin. SOLUTION: The surface of an alkali metal hydroxide 2 is coated with a thermoplastic resin coating film 4 contg. dispersed water absorbing powder 3 to obtain the objective gaseous CO2 adsorbent. The hydroxide 2 reacts with gaseous CO2 in an atmosphere, adsorbs and removes the CO2 . It is, e.g. NaOH but hydroxide of other alkali metal or an alkaline earth metal has the same effect. The adsorbent maintains its effect even after the lapse of a certain period of time after production because moisture in the air passing through the coating film 4 is captured by the water absorbing powder 3 and the hydroxide 2 is not leached.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide adsorbent for use in refrigerators and freezers, a foamed heat insulating material, and a heat insulating box filled with the foamed heat insulating material.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of energy saving, there has been a need to reduce the thermal conductivity of a foamed heat insulating material and improve the heat insulating property.
C), and furthermore, ozone layer destruction by hydrochlorofluorocarbon (hereinafter, referred to as HCFC) and environmental problems such as global warming are attracting attention, and solving these is an extremely important theme.

[0003] Therefore, in the production of rigid urethane foam, which is a typical foamed heat insulating material, CFC and H
For the purpose of reducing the use of CFCs, various efforts have been made for foaming with pentane and cyclopentane, which are hydrocarbons (hereinafter referred to as HC) that have no effect on ozone depletion and have no effect on global warming. Are being considered.

[0004] Basically, in order to improve the heat insulation performance of rigid urethane foam, it is important to reduce the gas thermal conductivity of the gas component in the foam cell. Has been considered an effective means.

[0005] On the other hand, on the other hand, for the purpose of reducing the amount of the foaming agent used, the problem of compatibility between the foaming agent and the raw material components, and the improvement of various physical properties of the foam, etc. Gas must be used as the blowing agent component.

However, in such a configuration, since the carbon dioxide gas having a high gas thermal conductivity remains in the cells of the foamed heat insulating material, the heat insulating performance of the foamed heat insulating material becomes poor.

As an approach for solving such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-49628, a method of removing carbon dioxide gas components in bubbles using a carbon dioxide adsorbent such as zeolite, As disclosed in JP-A-322166, a method of removing a carbon dioxide component in bubbles by using a hydroxide such as an alkali metal has been proposed.

That is, a carbon dioxide adsorbent made of zeolite or the like is previously added to and mixed with the raw material, and the generated carbon dioxide gas is physically adsorbed by the adsorbent, or a hydroxide such as an alkali metal is previously added to the raw material. It is characterized in that carbon dioxide gas generated by addition and mixing is removed by a chemical reaction, and that the heat insulation performance is improved by filling the inside of the bubble with a foaming agent gas.

[0009]

SUMMARY OF THE INVENTION Cyclopentane, which is a hydrocarbon which is indispensable to ozone layer depletion and extremely low in global warming and is indispensable for protection of the global environment, is used as a foam material for foam insulation. In this case, cyclopentane, which is a blowing agent component, has poor compatibility with polyether polyol, which is a raw material for general-purpose rigid urethane foam, and the number of parts added to the premix is limited.

The boiling point of cyclopentane is 49.3 ° C.
And CFC11 which is a room-temperature boiling point blowing agent conventionally used
Compared with 23.8 ° C of HCFC141b and 32.0 ° C of HCFC141b. In order to improve foam foaming efficiency, it is necessary to increase the amount of water added compared to the case where conventional CFC11 or HCFC141b is used as a foaming agent. It is essential.

However, in the conventional configuration, when a physical carbon dioxide adsorbent such as zeolite is applied, the amount of carbon dioxide adsorbed is small, the necessary adsorbent is large, and the water content in the raw material is simultaneously reduced with the premix addition and mixing. When cyclopentane or the like is applied as a foaming agent because of dehydration removal, there has been a problem that the foam foaming efficiency is greatly reduced, and a reduction in the density of the foam cannot be achieved. When an alkali metal hydroxide is used, the amount of carbon dioxide adsorbed is large, and the required amount of alkali metal hydroxide can be reduced, but the foaming efficiency is also large because it reacts with isocyanate as a raw material component. There is a problem that the density of the foam decreases and the density of the foam cannot be reduced.

[0012] To solve these problems, Japanese Patent Application No. Hei.
Although it is conceivable to form a coating on the surface of a hydroxide such as an alkali metal as proposed in Japanese Patent Application Publication No. 009074, in this case, although the problem of a reduction in foaming efficiency can be solved, it is not possible to form a coating film in the atmosphere after coating. The exposure causes a problem that moisture in the atmosphere passes through the coating, alkali metal is eluted by the moisture, and the effective amount of carbon dioxide adsorbent decreases.

Therefore, even when cyclopentane or the like is used as a foaming agent, there has been a problem of developing a high-quality foam heat insulating material having excellent foam heat insulating performance while securing the same foam foaming efficiency as before. .

[0014] In view of the above problems, the present invention provides a carbon dioxide adsorbent whose carbon dioxide adsorption effect does not decrease with time even after a certain period of time has elapsed after the production of the carbon dioxide gas adsorbent, and which has improved foam heat insulation performance. With excellent high quality foam insulation,
An object of the present invention is to provide a heat insulating box body filled with the foam heat insulating material.

[0015]

According to the carbon dioxide adsorbent of the present invention, the surface of a powder composed of at least one of an alkali metal hydroxide and an alkaline earth metal hydroxide is treated with a thermoplastic resin. The resin is coated with a coating layer in which a water-absorbing powder is dispersed.

[0016] Further, the fact that a part of the hydroxide of the alkali metal and / or the hydroxide of the alkaline earth metal contained in the carbon dioxide adsorbent has been changed to the alkali metal carbonate and / or the alkaline earth metal carbonate. It is a feature.

Further, the foamed heat insulating material of the present invention comprises a foamed polyurethane resin composition having closed cells filled with a volatile foaming agent, and comprises one of an alkali metal hydroxide and an alkaline earth metal hydroxide. A part or all of the surface of the powder converted into alkali metal carbonate or alkaline earth metal carbonate is covered with a carbon dioxide adsorbent in which a water-absorbing powder is dispersed inside a thermoplastic resin. It is characterized by being performed.

The heat-insulating box of the present invention comprises an outer box, an inner box,
The space formed by the outer box and the inner box is filled with a foamed polyurethane resin composition having closed cells filled with a volatile foaming agent, and an alkali metal hydroxide or an alkaline earth metal in the resin composition. The surface of the powder in which part or all of the hydroxide has been changed to an alkali metal carbonate or an alkaline earth metal carbonate is coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin. A gas adsorbent is included.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon dioxide adsorbent according to claim 1 of the present invention has a surface of a powder comprising at least one of an alkali metal hydroxide or an alkaline earth metal hydroxide. Is coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin, and the carbon dioxide adsorbent according to claim 2 of the present invention is the carbon dioxide adsorbent according to claim 1. 2. The carbon dioxide adsorbent according to claim 1, wherein a part of the alkali metal hydroxide or alkaline earth metal hydroxide contained in the adsorbent has been changed to an alkali metal carbonate or an alkaline earth metal carbonate. .

Therefore, even if alkali metal hydroxide or the like having a high capacity is used as the carbon dioxide adsorbent, even if the water absorbing powder contained in the coating layer is stored for a long period of time, the infiltrated moisture in the atmosphere is reduced. , Captured by the water-absorbing powder,
Elution of alkali metal hydroxide and the like can be reduced. In addition, by using a thermoplastic resin for the coating layer, a coating powder of a thermoplastic resin powder and a water-absorbing powder can be directly sprayed onto the heated alkali metal hydroxide or alkaline earth metal to form a coating layer.

That is, since the coating can be performed without using a solvent such as water or a solvent, the water-absorbing powder is not adversely affected during the manufacturing process. Therefore, even when applied to a heat insulating material, an excellent carbon dioxide adsorbent which does not affect the foaming efficiency and foam properties can be obtained.

The foamed heat insulating material according to the third aspect of the present invention comprises:
A foamed polyurethane resin composition having closed cells filled with a volatile foaming agent, wherein part or all of an alkali metal hydroxide or an alkaline earth metal hydroxide is an alkali metal carbonate or an alkaline earth metal. This is a foamed heat insulating material containing a carbon dioxide adsorbent in which the surface of the powder converted into a carbonate is covered with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin.

A carbon dioxide adsorbent containing a hydroxide of an alkali metal or a hydroxide of an alkaline earth metal as a main component adsorbs and removes a carbon dioxide gas having a high thermal conductivity generated in bubbles due to a reaction between isocyanate and moisture. By doing so, it is converted into an alkali metal or alkaline earth metal carbonate, and the inside of the bubble is filled with a volatile blowing agent having a relatively low gas thermal conductivity. As a result, a foamed heat insulating material having excellent heat insulating performance is obtained.

Since the carbon dioxide adsorbent is coated with a thermoplastic resin in which water-absorbing powder is dispersed, a certain period of time has passed since the production of the carbon dioxide adsorbent. When carbon dioxide is applied, the carbon dioxide gas adsorption effect is hardly reduced. Further, the highly active alkali metal hydroxide or the like does not react with isocyanate or water in the raw material, and there is no adverse effect such as a decrease in the foaming efficiency in the foaming process.

According to a fourth aspect of the present invention, there is provided a heat insulating box having an outer box, an inner box, and closed cells filled with a volatile foaming agent in a space formed by the outer box and the inner box. A powder in which the foamed polyurethane resin composition is filled, and a part or all of an alkali metal hydroxide or an alkaline earth metal hydroxide is changed into an alkali metal carbonate or an alkaline earth metal carbonate in the resin composition. The present invention is characterized in that the surface of the body contains a carbon dioxide adsorbent coated with a carbon dioxide adsorbent coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin.

A carbon dioxide adsorbent containing a hydroxide of an alkali metal and a hydroxide of an alkaline earth metal as main components adsorbs and removes a carbon dioxide gas having a high thermal conductivity generated in bubbles due to a reaction between isocyanate and moisture. By doing so, it is converted to an alkali metal or alkaline earth metal carbonate, which is filled with a volatile blowing agent having a relatively low thermal conductivity. As a result, a heat insulating box filled with a foam heat insulating material having excellent heat insulating performance is obtained.

Since the carbon dioxide adsorbent is provided with a coating in which a water-absorbing powder is dispersed inside a thermoplastic resin, the carbon dioxide adsorbent which has passed a certain period after the production of the carbon dioxide adsorbent is applied. In this case, the carbon dioxide adsorption effect does not decrease much, and the highly active alkali metal hydroxide as the carbon dioxide adsorbent does not react with the isocyanate or water in the raw material. This results in a heat-insulating box filled with a heat-insulating material having excellent performance without adverse effects such as a decrease in the temperature.

(Embodiment 1) FIG. 1 is a cross-sectional view of a carbon dioxide adsorbent 1 according to an embodiment of the present invention. The coating of the plastic resin film 4 is provided. The alkali metal hydroxide 2 reacts with carbon dioxide in the atmosphere to perform adsorption and removal of carbon dioxide, and is made of sodium hydroxide. In addition, hydroxides of alkali metals such as potassium hydroxide and hydroxides of alkaline earth metals such as calcium hydroxide and barium hydroxide have the same effect.

Further, a mixture of an alkali metal hydroxide 2 and an alkaline earth metal hydroxide or an alkali metal hydroxide 2
The same effect is obtained even when a part of the hydroxide of the alkaline earth metal is changed to a carbonate.

Further, since the surface is coated with a thermoplastic resin having a water-absorbing powder dispersed therein, even after a certain period of time has elapsed after the production of the carbon dioxide adsorbent, the surface of the air has passed through the coating. Is trapped in the water-absorbing powder inside the coating layer, so that the alkali metal hydroxide 2 or the hydroxide of the alkaline earth metal, which is the main component of the carbon dioxide adsorbent, is not eluted by the water. It serves to suppress the effect of the gas adsorbent from being reduced.

Further, by forming the coating layer as the thermoplastic resin coating 4, a mixed powder of the thermoplastic resin powder and the water absorbing powder 3 is directly sprayed on the heated alkali metal hydroxide 2 to form the coating layer. In other words, since the coating can be performed without using a solvent such as water or a solvent, the water-absorbing powder 3 does not adsorb the solvent during the manufacturing process, and does not adversely affect the water-absorbing performance.

As the material of the thermoplastic resin film 4, any resin can be used as long as it has thermoplasticity. However, from the viewpoint of workability, polymethyl methacrylate, polyethylene, polypropylene and the like having a relatively low melting point, natural or Synthetic wax and the like are desirable. The water-absorbing powder 2 dispersed in the thermoplastic resin coating 3 can be any powder as long as it has a water-absorbing property. For example, organic substances such as polyacrylate, ion-exchange resin, and graft starch can be used. Further, inorganic substances such as silica gel and zeolite can be applied.

(Embodiment 2) FIG. 2 is an enlarged sectional view of a foamed heat insulating material according to an embodiment of the present invention, and FIG. 3 is a perspective view of a heat insulating box. The foamed heat insulating material 5 is composed of bubbles 6 and cell walls 7, and the carbon dioxide adsorbent 8 described in the first embodiment is dispersed therein. Immediately after the production of the foamed heat insulating material 5, the bubbles 6 are filled with a gaseous mixture of a volatile foaming agent and carbon dioxide having a high thermal conductivity generated by a reaction between the isocyanate and moisture in the raw material.

Thereafter, the carbon dioxide gas that has passed through the coating of the carbon dioxide adsorbent 8 reacts with the alkali metal hydroxide or the alkaline earth metal hydroxide in the carbon dioxide adsorbent 8 to form a carbonate. Therefore, by removing the carbon dioxide gas in the bubbles 6, the heat insulating performance of the foam heat insulating material 5 can be improved.

Further, since the carbon dioxide adsorbent 8 is coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin, highly active alkali metal hydroxide or the like is used in the isocyanate or water in the raw material. Etc., and there is no adverse effect such as a decrease in foaming efficiency in the foaming process.

Even when a carbon dioxide adsorbent has been used for a certain period of time after the production of the carbon dioxide adsorbent, moisture in the air that has passed through the coating is trapped by the water-absorbing powder inside the coating layer. Alkali metal hydroxides or alkaline earth metal hydroxides, which are the main components of the gas adsorbent, are not eluted by moisture, preventing the effect of the carbon dioxide adsorbent from decreasing, and as a carbon dioxide adsorbent. Excellent performance without decreasing the effect can be provided.

The space 11 formed by the inner box 9 and the outer box 10 is filled with the foamed heat insulating material to form a heat insulating box material having excellent heat insulating performance.

Hereinafter, the foam insulation of the present invention will be described with reference to examples. (Example 1) (Table 1) shows the raw material disposal of Example 1.

[0039]

[Table 1]

The polyol is a mixture of an aromatic amine-based polyether polyol and an ethylenediamine-based polyether polyol, and has a total hydroxyl value of 460 mgKOH /
g, the foaming agent was F335 manufactured by Shin-Etsu Chemical Co., Ltd., and the catalyst was Kaolyzer No. manufactured by Kao Corporation. 31, the main blowing agent is cyclopentane.

As the carbon dioxide adsorbent, sodium hydroxide manufactured by Kanto Denka Co., Ltd. having an average particle diameter of 500 μm was used as an alkali metal hydroxide powder. The film was formed by a method using a tumbling fluid type coating apparatus, in which sodium hydroxide previously charged was heated to about 120 ° C., and a mixed powder of a thermoplastic resin powder and a water-absorbing powder was injected.

As a thermoplastic powder, an average particle size of about 1 having a melting point 30 to 40 degrees higher than the heating temperature of sodium hydroxide is used.
5 μm polymethacrylmethyl powder, using a polyacrylate powder having an average particle size of about 30 μm as a water-absorbing powder,
The mixing ratio was 2: 1 and the amount of the mixed powder added was 10 parts by weight based on sodium hydroxide. The carbon dioxide adsorbing material thus prepared was referred to as Example 1.

The above raw materials are blended in a predetermined blending number to constitute a premix component. On the other hand, the isocyanate component is an organic polyisocyanate composed of polymeric MDI having an amine equivalent of 135.

The premix component thus prepared and the isocyanate component are mixed and stirred in a predetermined number of parts, foamed by a high-pressure foaming machine, and filled into a box formed of an inner box and an outer box. Obtained.

Table 1 shows the measurement results of the density, thermal conductivity, and the amount of carbon dioxide in the bubbles of the rigid urethane foam cut out from the heat insulating box obtained in Example 1 above. The thermal conductivity was measured by AUTO-λ manufactured by Eiko Seiki Co., Ltd. still,
One week after the preparation, the carbon dioxide adsorbent was applied to the foam insulation. The foam properties were measured three days after foaming.

At the same time, as a comparative example, a case where no carbon dioxide adsorbent was used (Comparative Example 1) and a case where a carbon dioxide adsorbent coated with only a methacrylate ester-based coating agent was used (Comparative Example 2) Are also shown in (Table 1).

As is clear from the results shown in Table 1, in Example 1, a significant reduction in the thermal conductivity, that is, improvement in the heat insulation performance, was recognized as compared with Comparative Example 1. This is considered to be due to the decrease in carbon dioxide gas, as can be seen from the measurement result of the gas in the bubble. The increase in foam density is considered to be due only to the effect of the addition of the carbon dioxide adsorbent, and there is no decrease in foaming efficiency, and there is no problem in the foaming process.

Further, in Example 1, a reduction in the thermal conductivity was recognized as compared with Comparative Example 2. In Comparative Example 2, there was no problem in the foaming process, the carbon dioxide gas in the bubbles was reduced, and the effect of reducing the thermal conductivity was also obtained. However, the effect was less than that in this example. This is because the moisture in the atmosphere permeates into the film by leaving the carbon dioxide adsorbent for a certain period of time after the preparation, but in Example 1, the water is absorbed by the water-absorbing powder inside the coating layer. In contrast, in Comparative Example 2, water passed through the coating layer, and sodium hydroxide, which was the main component of the carbon dioxide adsorbent, was eluted, so that an effective amount of carbon dioxide adsorbent could not be secured. .

As described above, the foamed heat insulating material of this embodiment is composed of the foamed polyurethane resin composition having closed cells filled with the volatile foaming agent, and the surface of the hydroxide powder of the alkali metal hydroxide is Foam insulation material containing a carbon dioxide adsorbent covered with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin, and does not adsorb moisture in the premix, thus lowering foam foaming efficiency In addition, the problem of a decrease in the amount of the effective carbon dioxide adsorbent due to elution of the hydroxide of the alkali metal in the carbon dioxide adsorbent even after standing for a certain period of time is solved.

Therefore, the gas in the foam bubbles is purified without impairing the physical properties of the foam, thereby improving the foam heat insulation performance.

As a result, the ozone depletion potential of 0, which is indispensable for protecting the global environment, and synchropentane, which is one of the hydrocarbons having almost no effect on global warming, have problems in foam properties as a foaming agent for urethane foam. It is possible to provide a high-quality foam insulation material having high heat insulation performance without any problem, and a high-quality heat insulation box body obtained by foam-filling the foam heat insulation material.

[0052]

As described above, the present invention provides a powder composed of at least one of an alkali metal hydroxide and an alkaline earth metal hydroxide, or a powder of the alkali metal hydroxide, A carbon dioxide adsorbent in which the surface of a powder in which a part of the hydroxide of an alkaline earth metal is changed to a carbonate is coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin, and a foamed polyurethane resin It is a heat insulating box in which a foamed heat insulating material containing the carbon dioxide adsorbent and a foam heat insulating material containing the carbon dioxide adsorbent are filled in a composition. Since the carbon dioxide adsorbent has a coating layer in which the water-absorbing powder is dispersed inside the thermoplastic resin, it does not adsorb moisture in the premix of the heat insulating material, so that a problem such as a decrease in foam foaming efficiency occurs. do not do.

Further, the amount of the effective carbon dioxide adsorbent does not decrease due to the elution of the hydroxide of the alkali metal in the carbon dioxide adsorbent even after being left for a certain period due to the effect of the water absorbing powder inside the coating layer.

Therefore, the gas in the foam bubbles is purified without impairing the various physical properties of the foam, and the heat insulation performance of the foam is improved.

As a result, an ozone depletion potential of 0, which is indispensable for protecting the global environment, and cyclopentane, which is one of hydrocarbons having almost no effect on global warming, is used as a foaming agent for urethane foam to improve various physical properties of the foam. It is possible to provide a high-quality foamed heat insulating material having a high heat-insulating performance without any problem, and a high-quality heat-insulated box in which the foamed heat-insulating material is foam-filled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a carbon dioxide adsorbent according to a first embodiment.

FIG. 2 is an enlarged sectional view of a foamed heat insulating material according to a second embodiment.

FIG. 3 is a perspective view of a heat insulating box according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide adsorbent 2 Alkali metal hydroxide 3 Water-absorbing powder 4 Thermoplastic resin coating 5 Foam insulation 6 Bubbles 7 Bubble wall 8 Carbon dioxide adsorbent 9 Inner box 10 Outer box 11 Space

Claims (4)

[Claims] The surface of a powder composed of at least one of an alkali metal hydroxide and an alkaline earth metal hydroxide is coated with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin. Coated carbon dioxide adsorbent. 2. The carbon dioxide gas according to claim 1, wherein a part of the alkali metal hydroxide or alkaline earth metal hydroxide contained in the carbon dioxide adsorbent has been changed to an alkali metal or alkaline earth metal carbonate. Sorbent. 3. A foamed polyurethane resin composition having closed cells filled with a volatile foaming agent, wherein part or all of an alkali metal hydroxide or an alkaline earth metal hydroxide is an alkali metal carbonate. A foam heat insulating material comprising a carbon dioxide adsorbent in which the surface of a powder converted into a salt is covered with a coating layer in which a water-absorbing powder is dispersed inside a thermoplastic resin. 4. A foamed polyurethane resin composition having closed cells filled with a volatile foaming agent is filled in a space formed by an outer case, an inner case, and the outer case and the inner case. The surface of the powder in which part or all of the alkali metal hydroxide or alkaline earth metal hydroxide has been changed to alkali metal carbonate or alkaline earth metal carbonate is absorbed into the thermoplastic resin. A heat-insulating box comprising a carbon dioxide adsorbent covered with a coating layer in which powder is dispersed.