JP7192497B2 - Insulating material and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat insulating material and its manufacturing method.

A heat insulating material is used for the purpose of improving heat insulating performance, and a foam such as urethane foam is used as a heat insulating material for refrigerators, freezers, building materials, and the like. In recent years, in order to further improve heat insulation, a vacuum heat insulating material is used in which urethane foam or glass fiber having a continuous hollow structure is used as a core material and these core materials are vacuum-packaged in a gas barrier packaging material (for example, Patent Document 1, See Patent Document 2). A vacuum chamber is also used to manufacture such vacuum insulation.

As a manufacturing technology for vacuum insulation materials that do not use a vacuum chamber, after mixing a gas absorbent with a foaming resin composition that serves as a core material, carbon dioxide gas is foamed while the gas absorbent is removed to create a vacuum. A method of creating conditions to improve heat insulation performance has been proposed (see, for example, Patent Document 3).

In addition, instead of mixing the gas absorbent with the resin composition, there is a method of placing a small bag-shaped gas absorbent on the outside of the urethane foam with a communicating hollow structure to absorb the carbon dioxide inside (for example, patent Reference 4) has also been proposed.

JP-A-7-234067 JP-A-9-138058 JP-A-1995-053769 JP-A-1999-334764

However, a high vacuum of 10 Pa or less is generally required in order to achieve high heat insulating performance in vacuum packaging, and even a slight deterioration in the degree of vacuum results in a rapid drop in performance. Moreover, in the manufacturing process, it is necessary to use a vacuum chamber and maintain a high vacuum state for a long time, which causes a decrease in productivity.

In addition, in the conventional method as described in Patent Document 3, it is difficult to adjust the balance between foaming and gas absorption, and addition of a gas absorbent to the core material increases the thermal conductivity. Therefore, it is difficult to achieve sufficient heat insulation. In addition, the method described in Patent Document 4 has problems such as a long time required to remove the gas due to localized gas absorption and a decrease in physical strength due to the communicating hollow structure. be.

An object of the present invention is to provide a heat insulating material having high heat insulating performance without using a vacuum chamber.

As a result of intensive studies on the above problems, the present inventors found that a core layer (A) having a fine hollow structure, at least a part of which is located outside the core layer (A), and a gas absorbing layer (B) capable of absorbing gas. ), and a heat insulating material having a gas blocking layer (C) located outside the gas absorbing layer (B) and capable of blocking gas, the above problem can be solved.
That is, the present invention is as follows.
[1]
a core layer (A) having a fine hollow structure,
a gas-absorbing layer (B) at least partially located outside the core layer (A) and containing a carbon dioxide absorbent and a water vapor absorbent, and capable of absorbing gas;
Having a gas blocking layer (C) located outside the gas absorbing layer (B) and capable of blocking gas,
The core layer (A) has a fine hollow structure with an independent hollow body ratio of 50% or more,
The gas absorption layer (B) directly or indirectly covers 80% or more of the surface area of the core layer (A),
The gas absorption layer (B) and the gas barrier layer (C) form a multilayer film,
Insulation.
[2]
The heat insulating material according to [1], wherein the core layer (A) has a porosity in the range of 90 to 99%.
[3]
The heat insulating material according to [1] or [2], wherein the average hollow diameter of the fine hollow structure of the core layer (A) is in the range of 1 to 500 μm.
[4]
The heat insulating material according to any one of [1] to [3], wherein the pressure of the fine hollow structure of the core layer (A) is in the range of 10 to 10000Pa.
[5]
The heat insulating material according to any one of [1] to [4], wherein the thickness of the core layer (A) is in the range of 0.5 to 40 mm.
[6]
The heat insulating material according to any one of [1] to [5], wherein the gas absorption layer (B) completely encloses the core layer (A).
[7]
The heat insulating material according to any one of [1] to [6], wherein the gas absorption layer (B) can further absorb oxygen.
[8]
The heat insulating material according to any one of [1] to [7], wherein the gas absorbing layer (B) is a layer in which a resin base material contains a gas absorbing agent.
[9]
The heat insulating material according to [8], wherein the resin contains polyethylene resin.
[10]
A method for producing a heat insulating material according to any one of [1] to [9], which includes the following steps.
(1) A step of foaming a resin to obtain a core layer (A) having a fine hollow structure
(2) The gas absorption layer (B), which is at least partially located outside the core layer (A) and capable of absorbing gas, is allowed to absorb the gas inside the core layer (A), and the hollow of the core layer is process of depressurizing a part
[11]
The method for producing a heat insulating material according to [10], wherein an extrusion foaming method is used in the step of obtaining the core layer (A).

ADVANTAGE OF THE INVENTION By this invention, it is possible to provide the heat insulating material which has high heat insulating performance, without using a vacuum chamber.

1 is a schematic diagram showing one embodiment of a heat insulating material using the foamed composite of the present invention. FIG. FIG. 4 is a schematic diagram showing another form of a heat insulating material using the foamed composite of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following embodiments. The present invention can be appropriately modified and implemented within the scope of the gist thereof.

[Insulation]
The heat insulating material of the present embodiment includes a core layer (A) having a fine hollow structure (hereinafter also simply referred to as "core layer (A)"), at least a part of which is located outside the core layer (A), A gas absorption layer (B) capable of absorbing gas (hereinafter also simply referred to as "gas absorption layer (B)"), and a gas barrier layer positioned outside the gas absorption layer (B) and capable of blocking gas (C) (hereinafter also simply referred to as "gas blocking layer (C)"). The core layer (A), gas absorption layer (B), and gas barrier layer (C) are described in detail below.

[Core layer (A)]
The core layer (A), as in the example shown in FIG. Also referred to as "structure"). Since the core layer (A) has a fine hollow structure, the heat insulating performance of the heat insulating material in this embodiment is greatly improved.

The fine hollow structure means a structure in which the average diameter of the fine hollow structure (hereinafter also referred to as “average hollow diameter”) in the present embodiment is in the range of 500 μm or less.
The average hollow diameter is preferably 1 to 300 μm, more preferably 1 to 100 μm, still more preferably 1 to 50 μm. When the average hollow diameter is 500 μm or less, the thermal conductivity tends to decrease when the pressure inside the hollow body is reduced, and a good heat insulating material tends to be obtained. On the other hand, when the average hollow diameter is 1 μm or more, the porosity tends to be less likely to decrease. In order to obtain a fine hollow structure with an average hollow diameter within the above range, for example, in the case of a foam, the type and amount of a gas or nucleating agent that contributes to foaming, and the resin characteristics such as the melt tension value of the base resin , the temperature and pressure at the time of molding, the shape of the molding machine, etc. are optimized. The average hollow diameter of the fine hollow structure can be measured by the method described in Examples below.

The porosity of the core layer (A) having a fine hollow structure is preferably 90.0 to 99.0%, more preferably 93.0 to 98.5%, still more preferably 95.0% to 98%. .0%. Since the thermal conductivity of the substrate portion is high, there is a tendency that the thermal conductivity and the strength can be set within the preferable range by being in such a range. In order to obtain a core layer (A) having a porosity within the above range, for example, in the case of a foam, the amount of gas that contributes to foaming should be increased. The porosity of the core layer (A) can be measured by the method described in Examples below.

Percentage of independent hollows in the fine hollow structure (in this specification, the percentage of independent hollows refers to the percentage of all the fine hollow structures in the core layer (A) that do not lead to the outside of the core layer (A). means a ratio) is preferably 50% or more, more preferably 70% or more, and still more preferably 80% or more in order to develop practical strength and heat insulating performance. The independent hollow body ratio of the fine hollow structure can be measured by the method described in Examples below.

The core layer (A) having a fine hollow structure can improve heat insulating performance by lowering the pressure in the hollow portion. The pressure of the hollow microstructure is preferably 10-10000 Pa, more preferably 15-5000 Pa, still more preferably 20-1000 Pa. When the pressure is 10 Pa or more, the influence of gas leakage is relatively small, and the pressure tends to be maintained. easy to get In order to obtain a fine hollow structure with a pressure within the above range, for example, a gas absorption layer (B) capable of absorbing a large amount of gas contained in the core layer (A) may be used. The pressure of the fine hollow structure can be measured by the method described in Examples below.

The thickness of the core layer (A) having a fine hollow structure is preferably 0.5 to 40 mm, more preferably 1 to 25 mm, still more preferably 2 to 20 mm. When the thickness is 0.5 mm or more, the heat insulation performance as a heat insulating material can be maintained, and when the thickness is 40 mm or less, the gas absorption layer (B) absorbs gas inside the core layer (A). becomes easy and tends to be excellent in heat insulation performance.

The method for producing the core layer (A) having a fine hollow structure is not particularly limited. A method of including a fibrous material having a hollow structure in the base material, and the like can be mentioned. Among them, considering the ease of production and gas permeability, a method of incorporating a foaming agent into the base material and creating a fine hollow structure by an extrusion foaming method or a bead foaming method is preferable, and the extrusion foaming method is more preferable.

The resin used as the base material is not particularly limited, but for example polyurethane, polyvinyl chloride, polycarbonate, polystyrene, polytetrafluoroethylene, polyolefin, ionomer, polysulfone, cellulose acetate and its analogues, ethyl cellulose, polydimethylsiloxane, silicone resin, and chlorosulfonated polyethylene. From the viewpoint of gas permeability and strength, preferred are polyurethane, polyvinyl chloride, polycarbonate, polystyrene, polyolefin, cellulose acetate and their analogs, and silicone resins, and more preferred are polystyrene and polyolefin. These can be used in combination of one or more. In addition, these are readily available as commercial products and can be preferably used.

A foaming agent is used to expand a base material such as rubber or plastic to form a hollow microstructure, and is mainly classified into chemical foaming agents and physical foaming agents.

A chemical foaming agent is a substance that generates gases such as nitrogen, ammonia gas, hydrogen, carbon dioxide, water vapor, and oxygen by thermal decomposition or chemical reaction.
Examples of chemical foaming agents include azo, nitroso, hydrazide, semicarbazide, azide, triazole, tetrazole, isocyanate, bicarbonate, carbonate, nitrite, hydride, sodium bicarbonate and acid. combinations, hydrogen peroxide and yeast, and metal powders and acids, with carbon dioxide-generating carbonates and bicarbonates being preferred as they can generate high-purity gas. These can be used in combination of one or more. In addition, these are readily available as commercial products and can be suitably used.

A physical foaming agent is a substance that foams by physical change such as pressure release or vaporization of compressed gas. Specific examples include inert gases such as nitrogen, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, water, and carbon dioxide, and carbon dioxide and water are preferred from the viewpoint of safety, environmental compatibility, and gas absorption. These can be used in combination of one or more. In addition, these are readily available as commercial products and can be suitably used.

The amount of foaming agent to be added cannot be uniquely determined because the optimum amount varies depending on the type of base material and the type of foaming agent.

The method of producing a fine hollow structure using a foaming agent is carried out by foaming in a base material containing the foaming agent, and the foaming method is variously determined according to the type and amount of the foaming agent. As an example, when carbon dioxide gas is used as a physical blowing agent, it can be suitably carried out according to the method described in JP-A-2010-173263 as a known method.

[Gas absorption layer (B)]
The gas absorption layer (B) is positioned outside the core layer (A) of the heat insulating material in this embodiment, as in the example shown in FIG. ) is a layer that can absorb gas in the In the example shown in FIG. 1, the gas absorption layer (B) completely encloses the core layer (A). , as in another example shown in FIG. 2, the gas absorption layer (B) may not include a part of the core layer (A), but may include portions other than the ends of the core layer (A). . As the gas absorption layer (B) absorbs the gas, the pressure in the hollow portion of the core layer (A) decreases, thereby improving the heat insulation performance.

The gas absorption layer (B) is a layer capable of absorbing gas by containing, for example, a gas absorbent. Specific examples of a mode in which a gas absorbent is contained include a layer using a gas absorbent alone or a layer containing a gas absorbent in a base material. As the base material, in addition to base materials similar to those used for the core layer (A), rubbers such as natural rubber, butadiene rubber, and silicone rubber, vinyl acetate emulsion adhesives, rubber-based adhesives, and starch-based adhesives. Adhesives and pressure-sensitive adhesives, such as, can be suitably used.

The gas absorbent is a substance capable of absorbing gas, and the type of gas to be absorbed is not particularly limited, but examples thereof include carbon dioxide, water vapor, and oxygen.
Examples of gas absorbents include alkali metal hydroxides, alkaline earth metal hydroxides, amine compounds, epoxy compounds, alkali metals, alkaline earth metals, alkali metal hydrides, alkaline earth metal hydrides, Lithium aluminum hydride, metal sulfates, calcium chloride, activated alumina, silica gel, molecular sieves, alkali metal carbonates, calcium oxide, sulfuric acid, phosphorus oxide, iron, sulfites, ascorbic acid, glycerin, MXD6 nylon, ethylenic Examples include saturated hydrocarbons, polymers having cyclohexene groups, oxygen atom-deficient structures of metal oxides such as titanium and cerium, alkali metal hydroxides, alkaline earth metal hydroxides, metal sulfates, chlorides. Calcium, activated alumina, silica gel, molecular sieves, alkali metal carbonates, calcium oxide, iron, and sulfites are preferable because they are inexpensive and hardly generate inert gas during gas absorption. These can be used in combination of one or more. In addition, these are readily available as commercial products and can be suitably used.

When a layer containing a gas absorbent in a base material is used as the gas absorbing layer (B), the amount of the gas absorbent added is preferably in the range of 5 to 99 parts by mass with respect to 100 parts by mass of the base material. It is more preferably 10 to 99 parts by mass in order to increase the absorption amount and rate of .
The gas absorption layer (B) may have a multilayer structure or a single layer structure, and a layer other than the gas absorption layer may be provided between the gas absorption layer (B) and the core layer (A).
Layers other than the gas-absorbing layer include, for example, an adhesive layer that bonds the core layer (A) and the gas-absorbing layer (B) together, and a buffer layer that prevents the components of the gas-absorbing layer from migrating to the core layer (A). be done.

In order to increase the rate at which the gas absorption layer (B) absorbs and removes the gas inside the core layer (A), the gas absorption layer (B) should directly or indirectly cover 40% or more of the surface area of the core layer (A). preferably 75% or more, more preferably 80% or more.

The thickness of the gas absorption layer (B) is preferably 10 to 500 μm, and this range tends to allow both gas absorption performance and heat insulation performance to be achieved. When the thickness is 10 μm or more, it is easy to obtain the performance of the gas absorbent that contributes, and when the thickness is 500 μm or less, the ratio of the gas absorption layer (B) in the heat insulating material does not become too large, and the thermal conductivity is improved. aggravation can be suppressed.
The gas absorption layer (B) can be produced, for example, by melt-kneading a gas absorbent into a resin to produce resin pellets, followed by film molding. Alternatively, the core layer (A) or film can be coated after the gas absorbent is kneaded with the adhesive described above.

[Gas barrier layer (C)]
As in the example shown in FIG. 1, the gas blocking layer (C) is positioned outside the gas absorbing layer (B) in this embodiment and is a layer capable of blocking gas from the outside.
The gas barrier layer (C) is not particularly limited as long as it is a layer capable of preventing air from entering the core layer (A). , a multilayer body having at least one selected from the group consisting of a metal thin film is preferable because it has excellent gas barrier properties. These are commercially available and can be preferably used. These can be used in combination of one or more.
The gas blocking layer (C) may have a multi-layer structure or a single layer structure. may be provided with a layer of
Layers other than the gas blocking layer include, for example, a sealant resin layer for heat sealing and a protective layer for preventing pinholes in the gas blocking layer (C).

The thickness of the gas barrier layer (C) is preferably 1 μm to 500 μm, and this range tends to allow both gas barrier performance and heat insulation performance to be achieved.

[Method for producing heat insulating material]
The method for manufacturing the heat insulating material of the present embodiment is not particularly limited as long as the heat insulating material of the present embodiment can be obtained, but has, for example, the following steps.
(1) A step of foaming a resin to obtain a core layer (A) having a fine hollow structure (2) A step of allowing a gas absorbing layer (B) capable of absorbing gas to absorb the gas inside the core layer (A)

The step (1) for obtaining the core layer is not particularly limited, but includes the same as the above-described “Method for producing core layer (A)”. In addition, the step (2) for absorbing gas is not particularly limited, but for example, by combining a core layer (A) having a fine hollow structure with a gas absorption layer (B) and a gas barrier layer (C), It can be carried out. As a method of compositing, for example, the gas absorption layer (B) and the gas barrier layer (C) are adhered by conventional dry lamination, and the gas absorption layer (B) and the gas barrier layer (C) are combined. A method of applying an adhesive to the layer and adhering it to the core layer (A) may be used. As another form, the core layer (A) and the gas absorption layer (B) are adhered by conventional dry lamination or heat lamination, and the composite of the core layer (A) and the gas absorption layer (B) is formed. A method of covering without adhering with the gas barrier layer (C) may also be used. Moreover, when using a heat insulating material, it is preferable to hermetically seal the ends thereof.

In the step (1) of obtaining the core layer, it is preferable to use the extrusion foaming method among the above-described "methods for producing the core layer (A)".

EXAMPLES Hereinafter, the present embodiment will be specifically described with reference to Examples, but the present embodiment is not limited to these.

[Average Hollow Diameter of Fine Hollow Structure]
The average hollow diameter of the fine hollow structure was calculated by the following method. Specifically, first, the core layer (A) is cut along an arbitrary X direction orthogonal to the thickness direction and along the Y direction orthogonal to the thickness direction and the X direction, and the center portion of each cut surface is Photographs were taken with a scanning electron microscope (trade name “JSM-6460LA” manufactured by JEOL Ltd.) at a magnification of 20 to 100 times.
Next, the photographed image was printed on A4 paper, and a straight line with a length of 60 mm was drawn on the image. Here, a straight line was drawn parallel to the X direction for the cut surface cut in the X direction, and parallel to the Y direction for the cut surface cut in the Y direction. Calculate the average chord length (t) of the hollow from the number of hollows existing on each straight line (including point contact) by the following formula, tY direction).
Average chord length (t) = 60 (mm) / (number of hollows x magnification of photo)
Furthermore, in both the enlarged photograph of the cut surface cut along the X direction and the enlarged photograph of the cut surface cut along the direction perpendicular to the Y direction, the Z direction (thickness direction) perpendicular to the X direction and the Y direction Draw a straight line with a length of 60 mm parallel to each, count the number of hollows existing on these straight lines, calculate the average chord length (t) in the thickness direction for each cut surface, and calculate these average chord lengths The arithmetic mean value of (t) was calculated, and this arithmetic mean value was defined as the average chord length in the thickness direction (tZ direction).
Then, based on the calculated average chord length (t) in each direction, the average hollow diameter of the fine hollow structure was calculated by the following formula.
Average hollow diameter (mm) = (tX direction + tY direction + tZ direction)/3

[Porosity]
The porosity of the core layer (A) was obtained from the density of the base material, which is the base of the core layer (A), and the density of the core layer (A), using the following formula.
Porosity (%) = (base material density - density of core layer (A)) / (density of base material) x 100

[Independent Hollow Body Ratio of Fine Hollow Structure]
After cutting the core layer (A) into a rectangular parallelepiped with a length of 25 mm, a width of 25 mm, and a thickness of 20 mm (if the thickness is insufficient, the cut test pieces are overlapped to form the rectangular parallelepiped ), and the test piece was allowed to stand for one day in a thermostatic chamber under the conditions of atmospheric pressure, relative humidity of 50%, and temperature of 23°C.
Next, the accurate apparent volume value Va of this test piece was measured. Then, after sufficiently drying the test piece, according to procedure C described in ASTM-D2856-70, the volume value Vx was measured with an air comparison type hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. Based on these volume value Va and volume value Vx, the independent hollow body ratio of the fine hollow structure was calculated from the following formula. In addition, each measurement and each calculation were performed on five different test pieces, and the average value was obtained. This average value was taken as the independent hollow body ratio.
Percentage of independent hollow bodies (%) = (Vx-W/ρ) x 100/(Va-W/ρ)
Vx: the sum of the volume of the resin constituting the fine hollow structure and the total hollow volume of the independent hollow portion in the foamed resin molding (cm ³ )
Va: Geometrically calculated apparent volume (cm ³ )
W: Mass (g) of foamed resin molded product
ρ: Density of base material constituting core layer (A) (g/cm ³ )

[Pressure of fine hollow structure]
<Method 1>
An absolute pressure sensor (Optex FA Co.: FHAV-050KP) welded to an injection needle with an inner diameter of 1.2 mm was prepared. Subsequently, this injection needle with an absolute pressure sensor and the prepared heat insulating material were placed in a glove box, and the inside of the glove box was replaced with carbon dioxide. After that, pierce the core layer (A) of the prepared heat insulating material so that the tip of the injection needle with the absolute pressure sensor reaches the center part, and epoxy adhesive (Nichiban Co.: Araldite AR-R30) is applied to the part where the injection needle is pointed. was applied to prevent gas from entering from the outside. After 7 days the pressure of the hollow microstructure was measured. It should be noted that the piercing of the injection needle was carried out within 1 hour after the preparation of the heat insulating material. In addition, since the thermal conductivity, which will be described later, cannot be measured with the heat insulating material for which the pressure was measured, another heat insulating material having the same structure was produced and measured for the thermal conductivity.
<Method 2>
A heat insulating material in which the gas barrier layer (C) is not integrated with the core layer (A) with an adhesive or the like was measured by the following method, which is easier to measure.
An acrylic vacuum chamber was prepared and equipped with a high-precision vacuum gauge (M-342DG manufactured by Canon Anelva). Subsequently, after placing the heat insulating material two weeks after its preparation in the chamber, a displacement sensor (manufactured by Omron: ZX2) capable of accurately measuring distance was installed outside the chamber, and this displacement sensor and the chamber were placed together. It is possible to measure the distance to the surface of the heat insulating material. After that, when the inside of the chamber is slowly evacuated, the gas barrier layer (C) moves when the pressure inside the chamber becomes lower than the pressure of the core layer (A). The pressure of the core layer (A) was measured.

[thickness]
The thickness of the core layer (A) was measured in increments of 0.1 mm using vernier calipers.
The thicknesses of the gas absorption layer (B) and the gas barrier layer (C) were measured in units of 1 micrometer by observing the cross-section of each layer with a scanning electron microscope (manufactured by JEOL Ltd., JSM-6460LA).
The thickness of the test samples of insulation was simultaneously measured by thermal conductivity measurements with the HFM436 described above.

[Thermal conductivity]
Based on the HFM method described in JIS A1412, the thermal conductivity of the heat insulating material was measured at 25 degrees using a thermal conductivity measuring device HFM436 manufactured by Netchi Japan Co., Ltd.
thermal conductivity is
0.020 W / mK or less is evaluated as A,
B evaluation for 0.021 to 0.025 W / mK,
C evaluation for 0.026 to 0.030 W / mK,
A value of 0.031 W/mK or more was evaluated as D.
Those rated as D are rejected.

[Example 1]
<Preparation of Gas Absorption Layer (B1) and Composite with Gas Barrier Layer (C)>
The gas absorption layer (B1) was produced using a polyethylene resin (ELITE5220G manufactured by Dow Chemical Co.) as a base material, calcium hydroxide as a carbon dioxide absorbent, and calcium oxide as a water vapor absorbent.
First, the resin pellets (b1-1) for forming the gas absorption layer (B) were produced by melt-kneading the polyethylene resin/calcium hydroxide at a ratio of 51 parts by mass/49 parts by mass. Similarly, the resin pellets (b1-2) for forming the gas absorption layer (B) were produced by melt-kneading at a ratio of polyethylene resin/calcium oxide=60 parts by mass/40 parts by mass.
Subsequently, the resin pellets (b1-1) and (b1-2) were used at a ratio of 1:1 to form a two-layer film to obtain a gas absorption layer (B1) having a thickness of 100 μm.
Subsequently, on the (b1-1) layer side of the gas absorption layer (B1) prepared, a dry lamination adhesive TM250HV manufactured by Toyo-Morton Co., Ltd. and a curing agent CAT-RT86L-60 were diluted two-fold with ethyl acetate. was applied with a bar coater and dried, and then a commercially available gas barrier film having a layer structure of PET/DL/Al/LDPE/LLDPE as the gas barrier layer (C) (San A Kaken: for retort pouches, PET: polyethylene terephthalate, DL: adhesive, Al: aluminum foil, LDPE: low-density polyethylene, LLDPE: linear short-chain branched polyethylene) is bonded by dry lamination on the LLDPE side to form a composite, and the gas absorption layer (B1) and the gas barrier layer ( A multilayer film consisting of C) was obtained.

<Preparation of core layer (A1) and composite with multilayer film>
A tandem extruder was prepared by connecting a first extruder and a second extruder. 100 parts by mass of polystyrene resin (G9305 manufactured by PS Japan Co., Ltd.) is supplied to the first extruder of the tandem extruder and melt-kneaded, and carbon dioxide as a foaming agent is introduced from the middle of the flow path of the first extruder. was injected to uniformly mix and knead the molten polystyrene resin and carbon dioxide, and then the polystyrene resin was continuously supplied to the second extruder and cooled to a temperature suitable for foaming while being melt-kneaded. After that, the polystyrene resin is extruded and foamed from a circular mold attached to the tip of the second extruder, and the obtained cylindrical foamed molded product is placed on a mandrel and cooled. was cut to form a core layer (A1) having a thickness of 5 mm and having a fine hollow structure. Table 1 shows the average hollow diameter, porosity and independent hollow body ratio of the core layer (A1).
Subsequently, the gas barrier layer (C) is provided on the (b1-2) layer side of the gas absorption layer (B1) of the multilayer film having the gas absorption layer (B1) and the gas barrier layer (C) prepared by the above method. The core layer (A) was adhered using an adhesive in the same manner as the adhesion method. Then, the terminal portion was sealed with a heat seal (manufactured by Fuji Impulse Co., Ltd.) within a width of 20 mm. After 7 days, the thermal conductivity and pressure (Method 1) of this core layer (A1)-gas absorption layer (B1)-gas blocking layer (C) composite (insulating material) were measured. Table 1 shows the results.

[Example 2]
<Production of gas absorption layer (B2)>
The gas absorption layer (B2) was produced using a polyethylene resin (ELITE5220G manufactured by Dow Chemical Co.) as a base material, calcium hydroxide as a carbon dioxide absorbent, and calcium oxide as a water vapor absorbent.
First, the resin pellets (b2-1) for forming the gas absorption layer (B) were produced by melt-kneading the polyethylene resin/calcium hydroxide at a ratio of 50 parts by mass/50 parts by mass. Similarly, the resin pellets (b2-2) for forming the gas absorption layer (B) were produced by melt-kneading at a ratio of polyethylene resin/calcium oxide=50 parts by mass/50 parts by mass.
Subsequently, the resin pellets (b2-1) and (b2-2) were used at a ratio of 1.4:1 to form a two-layer film to obtain a gas absorption layer (B2) with a thickness of 120 μm.

<Preparation of Core Layer (A2) and Composite with Gas Absorption Layer (B2)>
A core layer (A) was produced in the same manner as in Example 1, except that carbon dioxide and water were used as blowing agents. Table 1 shows the average hollow diameter, porosity, and independent hollow body ratio of the core layer (A2) produced.
Subsequently, the (b2-1) layer side of the gas absorption layer (B2) was adhered to the core layer (A2) produced by the above method to produce a composite. This step was performed under a carbon dioxide atmosphere.

<Composite Composite of Core Layer (A2) Gas Absorption Layer (B2) and Gas Barrier Layer (C)>
The composite of the core layer (A2) and the gas absorption layer (B2) prepared above is completely covered with the gas barrier layer (C) described in Example 1, and the gap between the composite and the gas barrier layer (C) is After removing the gas as much as possible, the end portion was sealed with a heat seal within a width of 10 mm. This step was performed under a carbon dioxide atmosphere. Two weeks later, the thermal conductivity and pressure (Method 2) of this core layer (A2)-gas absorption layer (B2)-gas blocking layer (C) composite (insulating material) were measured. Table 1 shows the results.

[Example 3]
A composite (heat insulating material) was produced in the same manner as in Example 2, except that the core layer (A3) having the average hollow diameter, porosity, and independent hollow body ratio shown in Table 1 was used as the core layer (A). Then the thermal conductivity and pressure (Method 2) were measured. Table 1 shows the results.

[Example 4]
A core layer (A2) was obtained in the same manner as in Example 2. Subsequently, ⅓ of the surface of the core layer (A2) was adhered to the gas absorption layer (B2), and the whole was covered with the gas barrier layer (C). After removing the gas between the gas barrier layer (C) as much as possible, the end portion was hermetically sealed with a width of 10 mm using a heat seal. This step was performed under a carbon dioxide atmosphere. Two weeks later, the thermal conductivity and pressure (Method 2) of this core layer (A2)-gas absorption layer (B2)-gas blocking layer (C) composite (insulating material) were measured. Table 1 shows the results.

[Comparative Example 1]
The thermal conductivity was measured using a conventional polystyrene foam, the product name Cellboard of Iwakura Kagaku Kogyo Co., Ltd., as a heat insulating material, but the results were inferior to those of the examples (Table 1). Table 1 shows the results of other measurements and evaluations.

[Comparative Example 2]
Only the core layer (A1) obtained in the same manner as in Example 1 was prepared without using the gas absorption layer (B1) and the gas barrier layer (C), and the thermal conductivity was measured using it as a heat insulating material. Since the pressure of the fine hollow bodies did not decrease, the thermal conductivity was inferior to the examples (Table 1). Table 1 shows the results of other measurements and evaluations.

[Comparative Example 3]
Only the core layer (A2) obtained in the same manner as in Example 2 was prepared without using the gas absorption layer (B2) and the gas barrier layer (C), and the thermal conductivity was measured using it as a heat insulating material. Since the pressure of the fine hollow bodies did not decrease, the thermal conductivity was inferior to the examples (Table 1). Table 1 shows the results of other measurements and evaluations.

[Reference example 1]
The calcium hydroxide and calcium oxide powders used in producing the gas-absorbing layer pellets of Example 1 were placed in an air-permeable sachet to produce a gas-absorbing sachet. Subsequently, after obtaining a core layer (A1) in the same manner as in Example 1, a gas-absorbing sachet was placed on the core layer (A1). The core layer (A1) and the gas-absorbing sachet were completely covered with the gas barrier layer (C), and after removing as much gas as possible between the gas barrier layer (C), the ends were heat-sealed within a width of 10 mm. It was sealed using This step was performed under a carbon dioxide atmosphere. After two weeks, the pressure (method 2) and thermal conductivity of this composite were measured. However, since the bag-shaped gas-absorbing sachet was used instead of the gas-absorbing layer (B), the decrease in pressure was small. In addition, since the small bag protruded from the surface of the heat insulating material, the thermal conductivity could not be measured accurately.

This application is based on a Japanese patent application (Japanese Patent Application No. 2016-136563) filed with the Japan Patent Office on July 11, 2016, the contents of which are incorporated herein by reference.

Claims (11)

a core layer (A) having a fine hollow structure,
a gas-absorbing layer (B) at least partially located outside the core layer (A) and containing a carbon dioxide absorbent and a water vapor absorbent, and capable of absorbing gas; has a gas blocking layer (C) that is located and can block gas,
The core layer (A) has a fine hollow structure with an independent hollow body ratio of 50% or more,
The gas absorption layer (B) directly or indirectly covers 80% or more of the surface area of the core layer (A),
The gas absorption layer (B) and the gas barrier layer (C) form a multilayer film,
Insulation. The heat insulating material according to claim 1, wherein the core layer (A) has a porosity in the range of 90 to 99%. 3. The heat insulating material according to claim 1, wherein the average hollow diameter of the fine hollow structure of the core layer (A) is in the range of 1 to 500 μm. The heat insulating material according to any one of claims 1 to 3, wherein the core layer (A) has a fine hollow structure with a pressure of 10 to 10,000 Pa. The heat insulating material according to any one of claims 1 to 4, wherein the core layer (A) has a thickness in the range of 0.5 to 40 mm. The heat insulating material according to any one of claims 1 to 5, wherein the gas absorption layer (B) completely encloses the core layer (A). The heat insulating material according to any one of claims 1 to 6, wherein the gas absorption layer (B) can further absorb oxygen. The heat insulating material according to any one of claims 1 to 7, wherein the gas absorption layer (B) is a layer in which a gas absorbent is contained in a resin base material. 9. The insulation of claim 8, wherein said resin comprises polyethylene resin. A method for manufacturing a heat insulating material according to any one of claims 1 to 9, comprising the following steps.
(1) step of foaming a resin to obtain a core layer (A) having a fine hollow structure; A step of causing B) to absorb the gas inside the core layer (A) and lowering the pressure in the hollow portion of the core layer. The method for producing a heat insulating material according to claim 10, wherein an extrusion foaming method is used in the step of obtaining the core layer (A).

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