JPH09145241A - Vacuum heat-insulating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily make the inner part of a container vacuum, lower a heat conductivity and stabilize the heat conductivity for a long period by sealing a porous forming member having a specific density and including inorganic fibers and a thermoplastic resin as main components in a container with a gas barrier characteristic. SOLUTION: A porous forming member having a density of 100 to 700kg/m<3> and including inorganic fibers and a thermoplastic resin as main components is sealed in a container having a gas barrier characteristic. Preferably, a heat insulating core material is sealed and packed under a pressure reduced state by the coimtainer with the gas barrier characteristic and flexibility. Such a vacuum heat insulating material is obtained by arranging the heat insulating core material in the container, exhausting air in a vacuum packer and sealing the container when a prescribed degree of vacuum is obtained. Therefore, the forming member which is easily handled is used as the heat insulating core material, so that the container can be easily made vacuum, a heat conductivity can be lowered and the heat conductivity can be stabilized for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material used for home appliances such as refrigerators and rice cookers, and building materials such as outer and inner walls of buildings.

[0002]

2. Description of the Related Art Conventionally, an inorganic fine powder such as silica, an inorganic fiber such as glass fiber, and an insulating core material such as an organic molding such as a continuous urethane foam are contained in a container (bag) having a gas barrier property. Then, in the case of a refrigerator, a vacuum heat insulator manufactured by sealing the interior of the refrigerator with reduced pressure is placed between the inner box and the outer box and used as a heat insulating material.

[0003]

When inorganic fine powder is used as the heat insulating core material, in order to prevent the powder from scattering during the production of the vacuum heat insulating material and improve the smoothness of the surface of the heat insulating material, first, A vacuum heat insulating material was manufactured by filling an air-permeable inner bag with an inorganic fine powder, press-molding it into a flat plate shape, and further vacuum packaging. As described above, when the inorganic fine powder is used, the production of the heat insulating material is complicated, and since the fine powder is used,
There is a problem that it cannot be easily evacuated.

Also, when the inorganic fiber is used, it is necessary to fill it in the air-permeable inner bag. If the fiber diameter is not less than 2 μm, the smoothness of the obtained vacuum heat insulating material cannot be obtained and the thermal conductivity is also high. It is said that the temperature will not drop below 0.01 Kcal / m · hr · ° C. (JP-A-7-139691) Furthermore, an organic molded article such as a continuous-type urethane foam is easier to handle than powders and fibers, but closed cells tend to remain, and a volatile component derived from the foaming agent or raw material used. Therefore, it is difficult to maintain the initial degree of vacuum, and there is a problem that the thermal conductivity increases.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention provide a vacuum heat insulating material which can easily evacuate the inside of a container, has a low thermal conductivity and a long-term stability of the thermal conductivity.

[0006]

Means for Solving the Problems The present invention has been intensively studied in view of the above problems, and as a result, a core having a low density and using an inorganic fiber and a thermoplastic resin as a main component as a heat-insulating core material is obtained. The inventors have found that a vacuum heat insulating material can be obtained that is easy to handle, has a low thermal conductivity, and a small rate of change in thermal conductivity. That is, the gist of the present invention is to provide a container having gas barrier properties with an inorganic fiber and a thermoplastic resin as main components and a density of 100 to 700 kg.
/ M is ³ a porous compact consists in the vacuum heat insulating material formed by sealing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The basic structure of the vacuum heat insulating material of the present invention is that the heat insulating core material is closely packed in a reduced pressure state in a container having a gas barrier property, preferably a gas barrier property and flexibility like a known vacuum heat insulating material. . Such a vacuum heat insulating material can be obtained by arranging a heat insulating core material in a container, performing an exhaust process in a vacuum packaging machine, and sealing the container when a predetermined vacuum degree is reached.

In the vacuum heat insulating material of the present invention, the inside of the container is
It is usually desirable to evacuate to less than 1 Torr. If the degree of vacuum is higher than 1 Torr, the heat conductivity of the air existing inside the container is large and the heat insulating performance is lowered, which is not preferable. In the present invention, a known film can be used as the constituent material of the container as long as it has gas barrier properties. Specifically, a composite film obtained by laminating a metal foil on a plastic film or vapor-depositing a metal or a metal oxide, a film having gas barrier property itself, and a flexible film, and the like can be mentioned. .

As the plastic film, polyester film, polypropylene film and the like can be preferably used. Further, films having a gas barrier property such as vinylidene chloride resin film, vinylidene chloride resin coat film, polyvinyl alcohol film and the like are also suitable. The metal foil is typically aluminum, copper, iron, or the like, and the metal or metal oxide for vapor deposition is typically aluminum,
Examples thereof include silicon oxide and magnesium oxide. When forming a composite film by depositing a metal oxide,
A polyvinyl alcohol film is preferably used.

The layer structure of the composite film may be two layers, but a layer structure of three layers or more in which one or more plastic films are provided on both sides of the metal layer or the metal oxide layer is preferable. In a composite film with three or more layers,
A film having excellent scratch resistance (eg, polyester film) is used as the outermost layer film, and a film having excellent heat-sealing property is used as the innermost layer film (eg, polyolefin film such as polyethylene and polypropylene, polyamide resin such as nylon 6 and nylon 66). A film, an acrylonitrile / butadiene / styrene copolymer, an acrylonitrile copolymer film such as an acrylonitrile / styrene copolymer, a polyacrylate film such as polymethylmethacrylate, preferably a polyolefin film) is used. These resins may be used alone,
They may be copolymerized or mixed and used. The shape of the container is conveniently a tubular body with both ends open.

In the present invention, a porous molded body is used as the heat insulating core material. The porous molded article used in the present invention contains an inorganic fiber and a thermoplastic resin as main components. The main component is 80% by weight or more, preferably 9% by weight of the inorganic fiber and the thermoplastic resin, with respect to the weight of the porous molded body.
It shows that it is 5% by weight or more. The density of the porous molded body is 100 to 700 kg / m ³ , preferably 100 to 6
00 kg / m ³ , more preferably 100 to 500 kg /
m is ^3. When the density of the porous molded body exceeds 700 kg / m ³ , the ratio of the space portion (porosity) of the porous molded body is small, and even if the vacuum degree is increased, the thermal conductivity of the vacuum heat insulating plate becomes solid heat transfer. It does not decrease because it is dominated, and 100 kg / m
^When it is less than ³ , the strength of the porous molded article becomes weak, which is not preferable.

In the present invention, it is preferable that the porous molded body contains a radiant heat shielding material having an effect of shielding radiant heat, because the thermal conductivity is further reduced. The radiant heat shielding material usually includes metal oxides, metal hydroxides, carbides, etc., preferably metal oxides such as Si, Ti, Al, etc., metal hydroxides, carbides, graphite, particularly preferably silicon carbide. , Titanium oxide, etc. are used. The radiant heat shielding material is usually used as fine particles of 0.5 to 30 μm. The ratio of the radiation heat shielding material contained in the porous molded body is usually 1 to 20% by weight, preferably 5 to 15% by weight.

The inorganic fibers constituting the porous molded article include glass fibers, ceramic fibers made of alumina, silica-alumina, silicon nitride, silicon carbide, carbon fibers,
Examples thereof include metal fibers, slag wool fibers and rock wool, and preferably glass fibers, ceramic fibers, slag wool fibers, rock wool and the like. The fiber diameter of the inorganic fiber is usually 3μ from the viewpoint of good handling and economical efficiency.
m or more, preferably 6 μm or more, and usually 30 μm or less, preferably 20 μm in order to develop sufficient strength.
It is preferable to set the following. The fiber length is usually 3 mm or more, preferably 6 mm or more from the viewpoint of strength development, and is usually 50 mm or less, preferably 25 mm or less from the viewpoint that uniform dispersion is possible.

The proportion of the inorganic fiber contained in the porous molded body is usually 10 to 90% by weight, preferably 50 to 90% by weight. If the content of the inorganic fiber is less than 10% by weight, stable expansion due to springback of the fiber does not occur, and if it exceeds 90% by weight, the adhesion between the inorganic fiber and the thermoplastic resin becomes difficult and the porous molding is performed. The strength of the body becomes insufficient.

The inorganic fiber may be subjected to a surface treatment with a water-soluble polymer in order to improve hydrophilicity for the purpose of good dispersion in water, to improve adhesiveness with a thermoplastic resin, and to improve strength. You may perform surface treatment with a silane coupling agent etc. for the purpose of expression. The thermoplastic resin constituting the porous molded body, polypropylene, polyethylene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polysulfone, Examples thereof include polyphenylene sulfide. These can also be used as a mixture or modification of two or more kinds. Further, a plasticizer, a heat stabilizer, a light stabilizer, a filler, a dye / pigment, an impact resistant material, an extender material, a core material, a processing aid and the like which are generally used may be mixed and used. Among these thermoplastic resins, from the viewpoint of strength, durability, and rigidity, it is preferable to use a crystalline resin such as polypropylene, polyamide, polyester (polyethylene terephthalate, polybutylene terephthalate). Among them, molding is preferable. sex,
It is particularly preferable to use polypropylene from the viewpoint of the balance of physical properties and economy.

The proportion of the thermoplastic resin contained in the porous molded body is usually 10 to 70% by weight, preferably 10 to 40% by weight. If the proportion of the thermoplastic resin is less than 10% by weight, the strength of the obtained porous molded article is insufficient, while if it exceeds 70% by weight, the density becomes too high and sufficient thermal conductivity is obtained. I can't. The porous molded body composed of the inorganic fiber and the thermoplastic resin can be manufactured by heating a sheet-shaped molding material to spring back the fiber, and then molding and cooling.

The porous molded body composed of the inorganic fiber and the thermoplastic resin can be obtained by a conventionally known method. For example, as a method for producing a sheet-shaped molding material, a method in which a mat made of inorganic fibers is impregnated with a molten thermoplastic resin, heated and cooled to form a sheet-shaped molding material (laminating method),
A method in which a thermoplastic resin powder and a fixed length of inorganic fiber are dry mixed and dispersed, and then the mixture is made into a web shape, and heated, pressed and cooled to form a sheet-shaped molding material (dry dispersion method). ), A thermoplastic resin powder and inorganic fibers of a certain length are dispersed and mixed in water or water bubbles, and then formed into a web by papermaking, and heated, pressed and cooled to form a sheet-shaped molding material. A method (wet dispersion method) and the like can be mentioned. In the present invention, the method for producing the sheet-shaped molding material may be any of the above, but it is preferable to use a dispersion method, particularly a wet dispersion method, in which the inorganic fibers are uniformly dispersed and stable physical properties are obtained.

The porous molded body can be manufactured by utilizing the expansion of the sheet-shaped molding material. Specifically, the sheet-shaped molding material is preheated to a temperature exceeding the melting point or softening point of the thermoplastic resin in a far infrared heating furnace or the like. As a result, the binding force of the thermoplastic resin to the inorganic fibers is weakened, the residual stress of the inorganic fibers is released, and the thickness of the sheet-shaped molding material is preheated due to springback to return to the original state of the inorganic fibers. It expands to about 10 times the previous thickness.

The porous molded body is molded by utilizing the expansion of the sheet-shaped molding material. By inserting this expanded sheet-shaped molding material into a molding die, a porous molding having a desired shape and density can be produced (Japanese Patent Publication No. 52-1).
2283, JP-B-55-9119, JP-A-5-16277, JP-A-6-134876, etc.).

[0020]

EFFECTS OF THE INVENTION The vacuum heat insulating material of the present invention uses a molded body which is easy to handle as a heat insulating core material, so that it can be easily evacuated and has a low thermal conductivity and does not contain a volatile substance. Therefore, the long-term stability of the thermal conductivity is good without damaging the container.

[0021]

EXAMPLES The vacuum heat insulator of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. Example 1 A glass fiber having a diameter of 10 μm and a length of 13 mm as an inorganic fiber, and a spherical pellet having a diameter of 3 μm as a thermoplastic resin were mechanically crushed, and polypropylene powder classified from 70 mesh to 10 mesh by sieving the crushed product was used. A non-woven material having a composition with a glass fiber content of 60% by weight and a polypropylene resin of 40% by weight was produced by the papermaking method.
This non-woven fabric is preheated to 200 ° C. with a hot press to melt polypropylene and once cooled with a cooling press to 3 kgf / cm.
^After the polypropylene and the glass fiber are well blended by applying the pressure of ² , the gap between the cooling presses is expanded while the polypropylene is still in a molten state, and the glass fiber is springed back to cool the plate to a density of 5 mm. 360
A molded plate of kg / m ³ was obtained.

The obtained molded body was cut into 20 cm square pieces, and the laminated film container (outermost layer 15 μm polyethylene terephthalate / 9 μm Al foil / innermost layer 12 μm)
Nylon) and sealed in a vacuum packaging machine at a vacuum degree of 0.1 torr to obtain a vacuum panel. Compared to silica and the like, an inner bag is not required and it can be handled directly by hand. The obtained vacuum heat insulating material has a smooth surface and no cracks. The time required to reach a vacuum degree of 0.1 Torr was 30 minutes. When the thermal conductivity of the obtained vacuum heat insulating material was measured by a thermal conductivity meter manufactured by Eiko Instruments Co., Ltd., it was 0.0070 Kcal / m · hr ·
The temperature was 0 ° C, and there was no change in the thermal conductivity after one year.

Example 2 A non-woven material was produced in the same manner as in Example 1 except that the content of glass fiber was 70% by weight and the content of polypropylene resin was 30% by weight. By heating, pressurizing and cooling in the same manner as in Example 1, a molded plate having a plate thickness of 5 mm and a density of 340 kg / m ³ was obtained. The obtained molded body was cut into 20 cm square pieces, placed in the same laminated film container as in Example 1, and sealed in a vacuum packaging machine at a vacuum degree of 0.1 Torr to obtain a vacuum heat insulating material. The obtained vacuum heat insulating material had a smooth surface and had no cracks or the like. The time required to reach a vacuum degree of 0.1 Torr was 30 minutes. The thermal conductivity of the obtained vacuum heat insulating material was measured with a thermal conductivity meter manufactured by Eiko Seiki Co., Ltd.
It was 44 Kcal / m · hr · ° C, and there was no change in thermal conductivity even after 1 year.

Example 3 A non-woven material was produced in the same manner as in Example 1 except that the glass fiber content was 85% by weight and the polypropylene resin content was 15% by weight. By heating, pressurizing and cooling in the same manner as in Example 1, a nonwoven material having a plate thickness of 5 mm and a density of 600 g / m ³ was produced. The obtained molded body is cut into 20 cm squares,
It was put in the same laminated film container as in Example 1 as it was, and sealed in a vacuum packaging machine at a vacuum degree of 0.1 Torr to obtain a vacuum heat insulating material. The obtained vacuum heat insulating material had a smooth surface and had no cracks or the like. The time required to reach a vacuum degree of 0.1 Torr was 30 minutes. When the thermal conductivity of the obtained vacuum heat insulating material was measured by a thermal conductivity meter manufactured by Eiko Instruments Co., Ltd., it was 0.0
It was 044 Kcal / m · hr · ° C, and there was no change in the thermal conductivity even after 1 year.

Example 4 In Example 2, the glass fiber, the polypropylene powder and the radiant heat shielding material SiC were made to have a weight ratio of 7: 3: 1.
C was added. The density of the obtained formed plate having a thickness of 5 mm is 4
It was 00 kg / m ³ . The obtained molded body was cut into 20 cm square pieces, placed in the same laminated film container as in Example 1, and sealed in a vacuum packaging machine at a vacuum degree of 0.1 Torr to obtain a vacuum heat insulating material. There is no problem in handling during vacuuming.
The obtained vacuum heat insulating material had a smooth surface and had no cracks or the like. When the thermal conductivity of the obtained vacuum heat insulating material was measured by a thermal conductivity meter manufactured by Eiko Instruments Co., Ltd., it was 0.0030 Kcal / m.
It was hr.degree. C., and there was no change in the thermal conductivity even after one year.

Comparative Example 1 In the same manner as in Example 1, the nonwoven material was preheated to 200 ° C. by a hot press to melt the polypropylene, and a pressure of 3 kgf / cm ² was once applied to the polypropylene by a cooling press to well blend the polypropylene and the glass fiber. After that, the glass fiber was cooled without being spring-back to produce a nonwoven material having a plate thickness of 5 mm and a density of 900 g / m ³ . The obtained molded body was cut into 20 cm square pieces, placed in the same laminated film container as in Example 1, and sealed in a vacuum packaging machine at a vacuum degree of 0.1 Torr to obtain a vacuum heat insulating material. The heat conductivity of the obtained vacuum heat insulating material was 0.100 Kcal / m · hr · ° C. when measured with a heat conductivity meter of Eiko Seiki Co., Ltd., and the performance as a heat insulating material was not shown.

Comparative Example 2 A nonwoven material was produced in the same manner as in Example 1 except that the glass fiber content was 25% by weight and the polypropylene resin content was 75% by weight. This nonwoven fabric was molded in the same manner as in Example 1 to obtain a molded plate having a plate thickness of 5 mm and a density of 830 kg / m ³ . The obtained molded body was cut into 20 cm square pieces, placed in the same laminated film container as in Example 1, and sealed in a vacuum packaging machine at a vacuum degree of 0.1 Torr to obtain a vacuum heat insulating material. When the thermal conductivity of the obtained vacuum heat insulating material was measured by a thermal conductivity meter of Eiko Seiki Co., Ltd., it was 0.05 Kcal / m · hr ·
The temperature was 0 ° C and did not show any performance as a heat insulating material.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Awata 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Corporation Yokohama Research Institute

Claims (6)

[Claims] 1. A container having a gas barrier property, containing an inorganic fiber and a thermoplastic resin as main components and having a density of 100 to 7.
A vacuum heat insulating material in which a porous molded body of 00 kg / m ³ is enclosed. 2. The porous molded body contains 10 to 10 thermoplastic resins.
70 weight% is contained, The vacuum heat insulating material of Claim 1 characterized by the above-mentioned. 3. The porous molded body contains 10 to 9 inorganic fibers.
The vacuum heat insulating material according to claim 1 or 2, wherein the vacuum heat insulating material contains 0% by weight. 4. The porous molded body comprises a radiant heat shielding material in an amount of 1 to 2.
The vacuum heat insulating material according to claim 1, wherein the vacuum heat insulating material contains 0% by weight. 5. The vacuum heat insulating material according to claim 1, wherein the inorganic fiber has a fiber diameter of 3 to 30 μm and a fiber length of 3 to 50 mm. 6. A container having a gas barrier property and flexibility is accommodated in a container having a density of 100 to 700 kg / m ³ and made of an inorganic fiber and a thermoplastic resin. A method for producing a vacuum heat insulating material, which comprises evacuating to 1 torr or less and closely sealing the container.