JP7590773B2 - Thermal insulation composition, thermal insulation article, and method for producing thermal insulation material - Google Patents

Description

The present invention relates to a heat insulating composition, a heat insulating article, and a method for producing a heat insulating material using the heat insulating composition.

To prevent deterioration of quality during transportation, refrigerated and frozen products such as medicines and food are usually transported in insulated containers, such as polystyrene foam containers or cardboard boxes with insulating materials such as urethane foam, when not in refrigerated or frozen conditions (see, for example, Patent Document 1).

Such insulated containers are bulky compared to the products they contain, which increases the cost of transporting the products. In addition, it is necessary to prepare an insulated container separate from the product itself and store and pack the product in it, which makes the transport process complicated.

On the other hand, there are many situations where a container that can keep a product at a high temperature for a relatively long period of time is required. Usually, such containers are required not to become hot on the outside during use, and at the same time, in many cases, the container must be able to be touched by the user with bare hands. To provide heat retention, containers made of bulky materials such as polystyrene foam, and paper containers with laminated side walls are used. Paper containers with laminated side walls are known to have an air layer inside the laminated side walls, as in Patent Document 2, for example. In either case, the overall container is bulky compared to the internal volume, and the container itself requires a large amount of space when transporting and storing.

In other fields, in the field of facilities (buildings, plants, car bodies, etc.), a technique is known in which an insulating layer such as a thermally foamable polymer is provided on the back side of the substrate that constitutes the inner wall to improve the thermal insulation inside the substrate (e.g., Patent Document 3). However, conventional insulating layers need to be thicker than a certain thickness to provide a higher insulating effect, which causes problems such as limited internal volume and increased costs for transporting the substrate.

As mentioned above, most conventional insulation materials in various fields are bulky, which reduces transport and storage efficiency. In addition, the materials used are limited to glass wool, insulation boards, urethane foam, polystyrene foam, etc., and due to their thickness and structural fragility, they are difficult to process and mold finely, so their applications are limited to box-shaped insulation containers and relatively large base materials.

In response to these problems, the inventors have provided a heat insulating paint containing a low-density powder material and a water-soluble polymer solution in a specific ratio as a heat insulating material that is less bulky than conventional materials, has excellent processability, and can be applied to fine structures, as well as a heat insulating method and heat insulating sheet material that use the heat insulating paint (see, for example, Patent Document 4).

Japanese Patent Application Publication No. 11-147577 JP 2000-247377 A Japanese Patent Application Publication No. 7-48881 JP 2013-100406 A

As mentioned above, various excellent insulating materials are known, but if there were insulating materials made from materials other than the known materials mentioned above and with good insulating properties, this would be preferable as it would allow for a wider variety of products to be available.

Therefore, the present invention aims to provide an insulating material that is easy to process and can be applied to microstructures, and has good insulating performance.

After extensive research, the inventors discovered that a heat insulating material with good thermal insulation properties can be obtained by using a composition in which a water-soluble polymer solution, which is mainly used as a water-soluble adhesive, is mixed with a low-density powder material in a specified ratio, and thus completed the present invention.

That is, the heat insulating composition of the present invention comprises a low-density powder material including at least one of a porous powder and a hollow powder, and a water-soluble polymer solution, and the mixing ratio of the low-density powder material to the water-soluble polymer solution is Va:Vb=1:2 to 1:5, where Va is the volume of the water-soluble polymer solution and Vb is the volume of the low-density powder material.
The thermal insulation article of the present invention comprises a freeze-dried product of the above-mentioned thermal insulation composition.

The method for producing a heat insulating material of the present invention includes a molding step of applying the heat insulating composition to the surface of a substrate or pouring the composition into a mold, a freezing step of freezing the heat insulating composition obtained by the molding step, and a vacuum drying step of vacuum drying the frozen heat insulating composition obtained by the freezing step.

The heat insulating composition and the method for producing a heat insulating material according to the present embodiment can provide a heat insulating material that is easy to process and has good heat insulating performance. It is also possible to produce a heat insulating material with a reduced thickness, in which case a heat insulating material that is low in bulk but has good heat insulating properties can be provided.

The insulating article of this embodiment has good insulating performance because it contains the insulating material of this embodiment.

FIG. 2 is a side cross-sectional view showing a schematic configuration of a heat-insulating container used in the examples. 1A and 1B are a side cross-sectional view and a plan view showing a schematic configuration of another heat-insulating container used in the examples. FIG. 2 is a diagram showing a state in which a temperature measuring device for high temperature testing is housed in the thermal insulation container of FIG. 1 . 1 is a graph showing changes in measurement temperature in Example 2 and Comparative Example 1. FIG. 3 is a diagram showing a state in which a temperature measuring device for low-temperature testing is housed in the thermal insulation container of FIG. 2 . 1 is a graph showing changes in measurement temperature in Example 2 and Comparative Example 2. 1 is a graph showing changes in measurement temperature in Example 1 and Comparative Example 3.

The heat insulating composition, heat insulating article, and method for producing a heat insulating material using the heat insulating composition of the present invention will be described in detail below with reference to one embodiment of each.

<Thermal insulation composition>
The heat insulating composition of the present embodiment is a heat insulating composition comprising a low-density powder material containing at least one of a porous powder and a hollow powder, and a water-soluble polymer solution. Each component will be described below.

(Water-soluble polymer solution)
In the present embodiment, the water-soluble polymer solution used is a solution in which purified water or the like is used as a solvent and a water-soluble polymer is dissolved in the solvent as a solute. This differs from the conventional method of dissolving polymer compounds in organic solvents.

When silica, such as methyl silicate or critical drying gel, is added to purified water or an aqueous solution of polyvinyl alcohol (PVA) dissolved in purified water, the silica remains above the liquid surface and this state is maintained for more than one week. Therefore, low-density powder materials are unlikely to dissolve or be suspended in a water-soluble polymer solution. Therefore, by using a water-soluble polymer, the reduction in the insulating effect due to the collapse of the three-dimensional structure of the low-density powder material is suppressed.

In contrast, when a porous or hollow low-density powder material described below is mixed with an organic solvent, depending on the type of low-density powder material, the presence of the powder such as methyl silicate or silica such as critical drying gel cannot be visually confirmed in the solvent (it becomes in a dissolved state (transparent)), and the inventors have already confirmed that a paint produced by suspending the low-density powder material in an organic solvent does not have a sufficient heat insulating effect (see Patent Document 4 above).

It has also been confirmed that when zeolite or calcium carbonate is used as a low-density powder and mixed with an organic solvent, the solvent easily penetrates into the powder, and in order to prepare a heat insulating composition, the powder content must be reduced. The reason for this is unclear, but it is presumed that this is because the solvent easily penetrates into the pores of the powder due to factors such as low surface tension. If the amount of low-density particles in the heat insulating composition is reduced, it becomes difficult to fully achieve the heat insulating effect.

On the other hand, this phenomenon is not observed in aqueous PVA solutions (5-20% by mass), and it is possible to mix it with a sufficient amount of zeolite or calcium carbonate, which can provide sufficient insulating effect.

In view of the above, it has already been found that in order to fully utilize the performance of a heat insulating composition containing a low-density powder, it is particularly suitable to use an aqueous solution (particularly the water-soluble polymer solution described below) rather than an organic solvent. In this embodiment, however, a heat insulating composition that can form a good heat insulating material in other forms has been found.

Examples of water-soluble polymers that can be used in this embodiment include polyvinyl alcohol (PVA), polyvinyl acetate, starch, and water-based urethane. In particular, polyvinyl alcohol is suitable for use because it has a wide and high affinity for sheet materials such as paper, cloth, and nonwoven fabric, which will be described later, is easy to apply, and has a relatively short drying time after application.

When using polyvinyl alcohol as the water-soluble polymer, it is preferable to use one with a molecular weight of 10,000 to 200,000, especially 50,000 to 150,000. If the molecular weight is too low, it is difficult to form a stable coating film, and if the molecular weight is too high, it is difficult to prepare the desired aqueous solution.

The concentration of the water-soluble polymer in the water-soluble polymer solution is preferably 0.5 to 50% by mass, more preferably 0.5 to 10% by mass, and even more preferably 0.5 to 5% by mass.

(Low density powder material)
The low-density powder material used in this embodiment includes at least one of a porous powder and a hollow powder, and this low-density powder material is a main material for exerting the heat insulating effect of the heat insulating material. In this specification, the "low-density powder" refers to a powder having a density of less than 0.5 g/ ^cm3 , particularly less than 0.15 g/ ^cm3 , under conditions of 25°C and 1 atmospheric pressure.

The low-density powder material used in this embodiment may be, for example, a porous or hollow powder made of a known material such as silica, methyl silicate, alumina, silica-alumina, ceramic, zeolite, calcium carbonate, or zirconia.

In particular, aerogels made by drying methyl silicate monomer at normal pressure or critical drying are suitable for use because they are easy to manufacture at low density, can relatively easily form porous or hollow structures at the nano level, and are not easily disintegrated in aqueous solutions.

Regardless of the degree of porosity, it is preferable to use a low-density powder material whose thermal conductivity is 0.15 W/(m·K) or less, particularly 0.1 W/(m·K) or less, and even more preferably 0.06 to 0.018 W/(m·K).

When using a porous low-density powder as the low-density powder material, it is preferable that the porosity is 50.0 to 99.8%, particularly 70 to 99.8%, and even more preferably 86 to 99.8%.

Regardless of the structure of the low-density powder material, it is preferable that its average particle size is 2 to 25 μm, particularly 5 to 23 μm, and even more preferably 8 to 17 μm. If the particle size of the low-density powder material contained in the composition is 25 μm or more, the dispersion state of the low-density powder material may not be maintained well when forming the insulation material, and if it is 2 μm or more, the amount of air contained in the insulation material may be reduced, and sufficient insulation effect may not be obtained.

It is preferable to use a low-density powder material with a specific surface area of 400 m ² /g or more, particularly 500 to 1000 m ² /g, and more preferably 600 to 1000 m ² /g. By increasing the specific surface area, it is possible to increase the porosity when using porous powder, and to increase the amount of air contained within the particles when using hollow particles. In addition, by using a low-density powder material with a large specific surface area, it is possible to reduce the mass of the entire insulation material.

The heat insulating composition of this embodiment can be produced by mixing the water-soluble polymer solution and the low-density powder material in a volume ratio of 1:2 to 1:5, preferably 1:3 to 1:4. If the amount of low-density powder is too high, the fluidity will be poor and it will be difficult to form the heat insulating material by coating or pouring, and if the amount is too low, the heat insulating effect that is the objective of this embodiment will not be fully achieved.

(Textile materials)
In this embodiment, a fiber material may also be used. This fiber material is an optional component.

The fiber material is not particularly limited as long as it functions as a structural reinforcement for the resulting insulation material, and both inorganic and organic fibers can be used. Examples of inorganic fibers include glass fibers, alumina fibers, ceramic fibers, and carbon fibers. Examples of organic fibers include resin fibers such as polyimide fibers and polyamide fibers. By including such fiber materials, the strength of the resulting insulation material can be improved.

For example, the fiber material used here preferably has a fiber diameter of 1 to 5 μm, more preferably 3 to 5 μm. The fiber length is preferably 1 to 5 mm, more preferably 3 to 5 mm. Note that the diameter and length of the fiber here are the arithmetic average values of the fibers contained in the fiber material.

If the fiber diameter is too small, it will be prone to aggregation, which may increase the viscosity of the insulating composition and reduce film-forming properties. If the diameter is too large, the reinforcing effect will be reduced, reducing film-forming properties and heat resistance, or a heat transfer path will be formed, increasing thermal conductivity and reducing insulating properties.

Furthermore, if the fibers are too short, the reinforcing effect will be small, and film-forming properties and heat resistance may decrease. If the fibers are too long, they will be more likely to aggregate, which may increase the viscosity of the insulating composition and decrease film-forming properties. In addition, a heat transfer path may be formed, increasing thermal conductivity and decreasing insulating properties.

The content of this fiber material is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the low-density powder. If it exceeds 10 parts by mass, it will be more likely to aggregate, which may increase the viscosity of the insulation composition and reduce film-forming properties, or a heat transfer path will be formed, increasing thermal conductivity and reducing insulation properties. If it is less than 1 part by mass, the reinforcing effect may not be fully exerted.

As described above, the heat insulating composition in this embodiment can be obtained by mixing the low-density powder material and the water-soluble polymer solution in a predetermined ratio and adding a fiber component as necessary. This heat insulating composition is used to form a heat insulating material by the method described below, and is usually prepared as a liquid composition.

The insulating composition obtained as a liquid composition can be used to form an insulating material, for example, by applying it to a substrate or pouring it into a mold, as described below.

The viscosity of the heat insulating composition is not particularly limited as long as it allows the heat insulating material to be formed into the desired shape. For example, when the heat insulating composition is used as a paint, the viscosity is preferably 500 to 100,000 mPa·s, and the drying time when naturally drying at room temperature when the coating film has a thickness of 10 μm is preferably 2 hours or less. With this configuration, the paint can also be used as an adhesive. Note that all "viscosity" in this specification refers to the viscosity at 25°C.

When the heat insulating composition of this embodiment is used as a paint, it is preferable to apply it to the target article so that the paint layer is 2 to 200 μm thick. Since this paint is a liquid aqueous solution, it can be easily applied even to target objects with fine structures, and can provide a heat insulating effect. In this case, when the paint is applied to a sheet material so that the paint layer is 2 to 200 μm thick, a heat insulating sheet material can be formed. This heat insulating sheet material can be used as a packaging material or attached to the target article, and can provide a heat insulating effect to the target article.

The heat insulating composition of this embodiment contains at least one of a porous powder and a hollow powder as the low-density powder material described above. By including such a powder in the heat insulating composition, air can be contained in the insulating material formed, and this internal air can provide an insulating effect.

In addition, by using such a low-density powder, the heat insulating composition of this embodiment can also reduce the overall mass of the paint. From this perspective, when using a porous powder, it is preferable to use particles with higher porosity, and it is preferable to use particles with a higher specific surface area.

In addition to the performance aspects described above, the heat insulating composition of this embodiment can be obtained without using organic solvents, so there is no concern about its effects on the human body, and it can be used for packaging food and medicine, and as a building material for housing. Furthermore, the paint of this embodiment can provide good heat insulating effects even when applied to resin products, etc., without corroding the products. In other words, the heat insulating composition of this embodiment is a composition that is advantageous in terms of both safety and the environment.

<Method of manufacturing the heat insulating material>
Next, a method for producing a thermal insulating material using the above-mentioned heat insulating composition will be described.

First, the heat insulating composition is applied to the surface of the substrate to which heat insulating properties are to be imparted, or poured into a mold for forming the heat insulating material, to give the heat insulating composition a shape for the heat insulating material (molding process).

In this molding process, the thickness of the coating film applied to the substrate is not particularly limited, but is preferably 2 to 200 μm, more preferably 5 to 50 μm, and even more preferably 5 to 25 μm.

Specifically, the viscosity of the heat insulating composition is preferably 500 to 100,000 mPa·s, and more preferably 10,000 to 30,000 mPa·s. If the viscosity is too high or too low, it will be difficult to form a paint layer of the above thickness.

When pouring into a mold, the mold to be used is not particularly limited as long as it can be molded into the desired shape. In this case, the viscosity of the heat insulating composition should be such that it can be sufficiently filled into the mold.

The above-mentioned base and mold are directly subjected to the freeze-drying process described below, so they are preferably made of a material that will not cause problems during freezing. For example, bases and molds made of metal, resin, wood, etc. can be used.

Then, the insulating composition that has been applied or poured into the shape of an insulating material is frozen by cooling (freezing step). This freezing is performed by cooling to a temperature at which the solvent of the water-soluble polymer solution freezes. The solvent is usually water, and it is preferable to cool to, for example, -5 to -80°C. At this time, it is preferable to cool rapidly, for example, to pass the maximum ice crystal formation zone (-5°C to -1°C) within 30 minutes. By freezing rapidly in this way, the low-density powder material can be maintained in a dispersed state, and the manufacturing efficiency of the insulating material can be improved.

The above cooling causes ice crystals to form in the solvent. The ice crystals are obtained by first forming crystal nuclei, which then grow. At this time, it is preferable for the low-density powder material to be frozen in a uniformly dispersed state.

The frozen insulating composition is then dried (vacuum dried) under reduced pressure (drying process). In this drying process, the frozen solvent (moisture) in the insulating composition sublimes and is removed from the insulating composition, and the low-density powder materials are bonded and joined together by the water-soluble polymer. Then, spaces remain in the areas where the removed solvent (moisture) was present, resulting in an insulating material (freeze-dried body) with porous spaces between the low-density powder materials.

The drying process can be carried out under known conditions, and the frozen heat insulating composition is usually dried under reduced pressure at room temperature or with heating. For example, the temperature is set to room temperature to 60°C under reduced pressure conditions of 4 to 100 Pa. The drying time can be adjusted appropriately depending on the surface area of the heat insulating composition and the size of the structure, and may be set so as to achieve the desired dry state; for example, 1 minute to 48 hours is preferred, 4 hours to 36 hours is more preferred, and 18 hours to 30 hours is even more preferred.

The insulating material obtained in this way has extremely good insulating properties because both the low-density powder material itself and the porous spaces corresponding to the moisture removed as described above contribute to the insulating properties.

The heat insulating composition and the method for manufacturing a heat insulating material according to this embodiment can be applied to articles having fine structures and articles with low solvent resistance, and can provide heat insulating effects to these articles as well.

<Thermal insulation products>
The heat insulating article of the present embodiment includes a heat insulating material (freeze-dried body) obtained by freeze-drying the heat insulating composition described above as described above.

The insulating material obtained in this manner has, as described above, low-density powder material bound by a water-soluble polymer, a porous structure that corresponds to the moisture removed, and has good insulating properties.

The insulating article may be entirely or partially composed of the insulating material. In general, the insulating material (freeze-dried body) is included as part of the insulating article by packaging or attaching it to the desired article.

Examples of such insulating articles include an insulating container in which an insulating material is formed on the inner or outer periphery of the container, an insulating container consisting of an inner container and an outer container with the insulating material between the inner container and the outer container, and an insulating sheet having a laminated structure in which an insulating material of a predetermined thickness is formed on a sheet material. It is preferable that the insulating material is provided so as not to come into contact with the external atmosphere.

For example, this insulating article can provide insulation to refrigerated or frozen products that have traditionally been stored and transported in separate insulated containers. Even when storing refrigerated or frozen products in an insulated container, it is possible to reduce the bulk of the container, improving transportation efficiency.

In addition, it is possible to manufacture a thermal insulation packaging container that is less bulky than conventional containers compared to the volume of the contents.

In addition, for example, by applying the heat insulating composition of this embodiment to the back surface of wallpaper for residential use, a low-bulk insulating material can be provided on the back surface, providing heat insulation to the wall.

The heat insulating composition of this embodiment will be described in detail below with reference to examples. It goes without saying that the present invention is not limited to the description of these examples.

Example 1
100 mL of 1% by mass polyvinyl alcohol (PVA) aqueous solution and 22.5 g (300 mL) of aerogel as low-density powder were uniformly mixed using a mixer to prepare heat insulating composition 1 (mixing ratio (volume ratio) was water-soluble polymer solution: low-density powder = 1:3). Here, the low-density powder was silica powder (manufactured by Yingde City Elite Asia-Pacific Electronics Co., Ltd., product name: aerogel, density 0.0125-0.018 g/cm ³ , average particle size 5 μm, specific surface area 650 m ² /g), and the PVA was JC33 (manufactured by Nippon Vinyl Acetate Popal Co., Ltd., product name). The viscosity of the prepared heat insulating composition 1 was 10,000 mPa·s.

This heat insulating composition 1 was poured into the inner wall and inner bottom of a cylindrical container with a diameter of 5 cm, and into the inside of the lid of the cylindrical container, with a mold placed so that the thickness was 1 cm, to form a cylindrical container equipped with the heat insulating composition.

This was cooled in a freezer at -15°C for two days to freeze the heat insulating composition. It was then vacuum dried for one week at -0.1 MPa (gauge pressure) and room temperature to produce the heat insulating container 1A with heat insulating material. Figure 1 shows a side cross-sectional view showing the schematic configuration of this heat insulating container.

Here, the insulated container 1A is composed of a cylindrical container 3 with insulating material 2 formed therein and its lid 3a. When the lid is closed, the inside of the insulated container 1A becomes a space surrounded by the insulating material 2.

The heat insulating composition 1 was then placed in a mold with inner dimensions of 100 mm x 100 mm x 100 mm, and a cylinder with a diameter of 65 mm was inserted into the center from above to a depth of 75 mm.

This was cooled in a freezer at -15°C for two days to freeze the heat insulating composition. It was then vacuum dried for one week at -0.1 MPa (gauge pressure) and room temperature, and the resulting freeze-dried product was removed from the mold, and the cylindrical body was removed to produce an insulating container 1B consisting only of the insulating material with a cylindrical container section.

Here, as shown in FIG. 2, the insulated container 1B is made only of the insulating material 2 and has an opening in the center of the top.

Example 2
As in Example 1, 100 mL of a 1% by mass polyvinyl alcohol (PVA) aqueous solution was mixed with 22.5 g (300 mL) of aerogel as a low-density powder, and 1 g of polyimide fiber was added. The mixture was mixed uniformly using a mixer to prepare a heat insulating composition 2 (the mixing ratio (volume ratio) was water-soluble polymer solution: low-density powder = 1:3).
The polyimide fibers used herein had an average fiber length of 1 cm and an average fiber diameter of 12 μm.

This heat insulating composition 2 was poured into the inner wall and inner bottom of a cylindrical container with a diameter of 5 cm, and into the inside of the lid of the cylindrical container, with a mold placed so that the thickness was 2 cm, to form a cylindrical container of the same shape as Example 1, equipped with the heat insulating composition.

This was cooled in a freezer at -15°C for two days to freeze the heat insulating composition. It was then vacuum dried for one week at -0.1 MPa (gauge pressure) and room temperature to produce the heat insulating container 2A with heat insulating material. Figure 1 shows a side cross-sectional view showing the schematic configuration of this heat insulating container.

The heat insulating composition 2 was then placed in a container with inner dimensions of 100 mm x 100 mm x 100 mm, and a cylinder with a diameter of 65 mm was placed in the center from above to a depth of 75 mm.

This was cooled in a freezer at -15°C for two days to freeze the heat insulating composition. It was then vacuum dried for one week at -0.1 MPa (gauge pressure) and room temperature, and the resulting freeze-dried material was removed from the container, and the cylindrical body was removed to produce the heat insulating container 2B, which consists only of the heat insulating material and has a cylindrical container section.

Here, as shown in FIG. 2, the insulated container 2B is formed only from the insulating material 2 and has a storage section that opens in the center of the top.

Comparative Example 1
As Comparative Example 1, a container C1 was prepared in which the insulating material of the above-mentioned insulated container 2A was not provided.

Comparative Example 2
As a comparative example 2, an insulated container C2B made of style foam (expanded polysteel) having the same shape as the insulated container 2B was prepared as a heat insulating material.

Comparative Example 3
As Comparative Example 3, a heat insulating composition C3 was prepared in the same manner as in Example 1, except that the compounding ratio (volume ratio) of the polyvinyl alcohol (PVA) aqueous solution to the low-density powder was changed to water-soluble polymer solution:low-density powder = 1:1.

Furthermore, an insulated container C3B consisting only of an insulating material with a cylindrical container portion was manufactured by the same procedure as in the manufacture of the insulated container 2B, except that the insulating composition C3 was used.

<Test Example>
[High temperature side test]
A thermometer 51 was placed inside the insulated container 2A manufactured in Example 2, and the inside was sealed with a lid. The thermometer 51 was fixed to a base 52 so that the temperature of the internal atmosphere of the insulated container 2B could be measured (see FIG. 3).

This was heated from room temperature (23°C) to 136°C over 20 minutes using an autoclave (manufactured by Toho Giken Co., Ltd., product name: SUN-1500), and the heated state at 136°C was maintained for 20 minutes. After that, the heated state was raised to just over 100°C, which was maintained for 20 minutes, and then it was cooled to room temperature and the temperature change was measured.

The results of the temperature change of the thermometer in the above test are shown in Figure 4. In Figure 4, the dashed line shows Comparative Example 1, and the solid line shows Example 2.

As can be seen from the results in Figure 4, in Comparative Example 1, the temperature fluctuated in accordance with the heating temperature of the autoclave, whereas when the insulating material of Example 2 was used, the temperature fluctuated more slowly in response to the heating temperature of the autoclave, and even when the material was returned to room temperature after being heated once, the heated state was maintained. From these results, it was found that the insulating material obtained using the insulating material composition of this embodiment had good insulating performance.

[Low temperature side test 1]
A test frozen body with the periphery of the thermometer frozen was placed inside the insulated container 2B produced in Example 2 (see FIG. 5), which was then placed in a cooler box and the inside was sealed with a lid. FIG. 5 is a schematic diagram showing the state in which the test frozen body is placed inside the insulated container 2B. Here, a can container was used as the test frozen body, and water was poured into the can container, and frozen with a thermometer 51 placed in the center, forming ice 53 around the thermometer 51. This test frozen body was cylindrical with a diameter of 65 mm and a height of 75 mm.
This was left at room temperature (23° C.) and the temperature change was measured.

The results of the temperature change of the thermometer in the above test are shown in Figure 6. In Figure 6, the dashed line shows Comparative Example 2, and the solid line shows Example 2.

As can be seen from the results in Figure 6, in Comparative Example 2, it took about 22:29 for the ice to melt and about 46 hours and 22 minutes for the temperature to reach room temperature, whereas in Example 2, it took about 31 hours and 22 minutes for the ice to melt and about 50 hours and 22 minutes for the temperature to reach room temperature. Between Example 2 and Comparative Example 2, the difference in time until the ice melted was about 8 hours and 53 minutes, and the difference in time until the temperature reached room temperature was about 4 hours, demonstrating that the insulation material of this example has better insulation performance than conventionally known insulation materials.

[Low temperature side test 2]
As in the above-mentioned low-temperature side test 1, a test frozen body was placed in the center of each of the insulated containers C3B obtained in Comparative Example 3 and the insulated container 1B, which were then placed in a cooler box and the inside was sealed with a lid.

This was left at room temperature (23°C) and the temperature change was measured. The results are shown in Figure 7. In Figure 7, the dashed line shows Comparative Example 3 and the solid line shows Example 1.

As can be seen from the results in Figure 7, in Comparative Example 3, it took about 29 hours and 20 minutes for the ice to melt, whereas in Example 1, it took about 30 hours and 48 minutes for the ice to melt. The difference in time it took for the ice to melt between Example 1 and Comparative Example 3 was about 1 hour and 28 minutes, demonstrating that the insulation material of this example has better insulation performance than the insulation material of the comparative example.

In Comparative Example 3, the proportion of PVA was relatively high, so the fluidity of the resin composition was good, but the processability of the freeze-dried product was inferior to that of Example 1. On the other hand, the insulated container of Example 1 had good processability and high insulation performance.

From the above, it has been found that the insulating article using the insulating composition shown in this embodiment has extremely good insulating performance, is easy to manufacture, and is excellent.

The invention made by the inventor has been specifically described above based on the embodiment and examples, but it goes without saying that the present invention is not limited to the above embodiment or examples, and various modifications are possible without departing from the gist of the invention.

The heat insulating composition, heat insulating article, and heat insulating material manufacturing method according to this embodiment can be applied to a wide range of fields, such as temperature control in fields requiring safety and environmental considerations, such as pharmaceuticals (including vaccines), food, and construction, and heat countermeasures for electrical components, such as electronic circuit boards, infrared sensors, and magnetic sensors.

1A, 1B...insulating container, 2...insulating material, 3...container, 3a...lid, 51...thermometer, 52...base, 53...ice

Claims (8)

A low-density powder material including at least one of a porous powder and a hollow powder, and a water-soluble polymer solution,
a mixing ratio of the low-density powder material to the water-soluble polymer solution is Va:Vb=1:2 to 1:5, where Va is the volume of the water-soluble polymer solution and Vb is the volume of the low-density powder material;
The low-density powder material has an average particle size of 2 to 25 μm and a specific surface area of 400 m ² /g or more;
Here, the low density powder is a powder having a density of less than 0.5 g/ ^cm3 under conditions of 25°C and 1 atmospheric pressure. The heat insulating composition according to claim 1, wherein the water-soluble polymer solution contains at least one water-soluble polymer selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, starch, and aqueous urethane, and the concentration of the water-soluble polymer is 0.5 to 50 mass %. 3. The heat insulating composition according to claim 1, having a viscosity at 25° C. of 500 to 100,000 mPa·s. The heat insulating composition according to any one of claims 1 to 3 , further comprising a fibrous material. 5. The heat insulating composition according to claim 4, wherein the fibrous material is at least one of glass fiber, alumina fiber, ceramic fiber, carbon fiber, polyimide fiber, and polyamide fiber. 6. The heat insulating composition according to claim 4 , wherein the fiber material is contained in an amount of 1 to 10 parts by mass per 100 parts by mass of the low-density powder material. A heat insulating article comprising a freeze-dried product of the heat insulating composition according to any one of claims 1 to 6. A molding step of applying the heat insulating composition according to any one of claims 1 to 6 onto a surface of a substrate or pouring the composition into a mold;
a freezing step of freezing the heat insulating composition obtained by the molding step;
a vacuum drying step of vacuum drying the frozen heat insulating composition obtained by the freezing step;
A method for producing a heat insulating material having the above structure.

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