JPH07332587A - Vacuum heat insulating material - Google Patents

Abstract

PURPOSE:To embody the light weight and improve the productivity during vacuum-packaging by vacuum-packaging a thermoplastic resin porous sheet with a specified characteristics in gas barrier packaging material. CONSTITUTION:A thermoplasticc resin porous sheet having fine pores in communicated structure with the pore diameter of 1-20,m, the continuous bubble fraction of 90-100% and the density of 20-100kg/m<3> is vacuum-packaged in gas barrier packaging material to manufacture vacuum heat insulating material. Since the pore diameter of the porous sheet used as a filler is 1-20mum, the vacuum degree of about 10<-1>mmHg or more is sufficient, and since the density is 20-100kg/m<3>or less, the weight is extremely light. In addition, handling performance in a vacuum-packaging process can be made remarkably desirable because of not a grain state but a porous sheet state. Also with the continuous bubble fraction being 90-100%, the vacuum degree immediately after vacuum- packaging can be maintained, and the vacuum-packaging process can be simplified.

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 heat insulation of appliances such as refrigerators and freezers and construction materials, and in particular, a vacuum heat insulating material having a significantly improved heat insulating performance as compared with conventional resin foam heat insulating materials. In addition, the present invention relates to a heat insulating material having characteristics of being lightweight and excellent in productivity as compared with conventional inorganic powder vacuum heat insulating materials.

[0002]

2. Description of the Related Art Conventionally, resin foams which have been widely used for heat insulating materials exhibit heat insulation performance by enclosing a gas having a low thermal conductivity such as Freon gas in the bubbles of the foam. However, in recent years, the use of chlorofluorocarbons, which is one of the CFCs used in resin foams, has been restricted due to environmental problems, especially the problem of ozone layer destruction. As a countermeasure, the development of so-called alternative CFC gases such as hydrochlorofluorocarbons and hydrofluorocarbons, which have a low degree of ozone depletion, is progressing, but the former is not without any effect on the depletion of the ozone layer. Due to its high thermal conductivity, it is necessary to increase the thickness of the heat insulating material in order to maintain the conventional heat insulation performance, and there is a concern that the alternative CFC gas may affect global warming. It is inherent.

Further, conventionally, as a solution to the chlorofluorocarbon problem, a vacuum heat insulating material which does not use any chlorofluorocarbon gas, in particular, a powder vacuum heat insulating material in which inorganic fine particles are used as a filler and vacuum packed with a resin film packaging material having a gas barrier property has been attracting attention. Are gathering. The inorganic fine particles here play an important role as a filler that secures voids equal to or less than the mean free path of air during vacuum packaging depressurization in order to reduce the thermal conductivity of the air present in the interparticle voids. .

[0004]

However, since this powder vacuum heat insulating material uses inorganic fine particles such as silica and pearlite as the filler, it has the following major problems. First, since it is an inorganic material, the density of the heat insulating material is as high as 200 to 350 kg / m ^3, and the weight is heavier than that of the resin foam, so there is a problem in handleability in the production process and it is used for heat insulation of equipment. In this case, the weight ratio of the heat insulating material to the weight of the equipment increases, and the amount of the heat insulating material used must be limited.

Next, the inorganic fine particles must be vacuum-packed, and the fine particles should not be sucked during vacuum packaging.
It is essential to preliminarily pack the material in an inner wrapping material that is breathable and capable of holding fine particles, and there is a problem in selection of the material and productivity of the process. Furthermore, since the particles are extremely fine, there is a concern that dust particles such as scattering of particles during the production process and the disposal process may affect the human body.

In order to solve the problems of these inorganic powder fillers, so-called continuous urethane foam or the like, in which a part of the cell membrane is broken to form open cells instead of the inorganic fine particles, has not been studied as the filler. However, even if the bubble diameter of the foam is small, it is at most about 60 to 70 μm, so the degree of pressure reduction during vacuum packaging must be increased to 10 ^-2 to 10 ^-3 mmHg or less, and the seal of the gas barrier packaging material is required. There was a problem with the long-term reliability of the gas barrier property such as the entry of air from the parts, etc., and it was practically unusable.

By the way, a fine cell foam having a cell diameter of 10 μm or less is prepared by impregnating polystyrene with nitrogen or carbon dioxide under high pressure, releasing the pressure, and then heating in an oil bath to foam. It has been considered for several years. U.S. Pat. No. 4,473,665, and "Polyme.
r Eng. Sc. , 27, P485-492, ANT
EC. '91. P1406 to 1410 "and the like, their production methods are specifically described. However, since the purpose of the microcellular foam is to reduce the amount of resin used, the foams described are all independent. It is a cell and has a foaming ratio of 2 to 3 times (at most about 10 times at most), and its development concept is clearly different from that of a high-foaming and continuous resin foam. It could not be used as a filler.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, as a result of diligent study on a low-density resin porous sheet having a communicating structure and fine pores, which has not been studied at all in the past, it was found to be lightweight and The present invention, which is a vacuum heat insulating material having high productivity in vacuum packaging, has been completed. That is, the present invention has a pore size of 1 to 20 μm and an open cell rate of 90 to 100.
%, A porous thermoplastic resin sheet having a density of 20 to 100 kg / m ³ is vacuum-packaged in a gas barrier packaging material, which is a vacuum heat insulating material.

The feature of the vacuum heat insulating material of the present invention is that since the pore size of the porous sheet used as the filling material is 1 to 20 μm, the degree of vacuum decompression is about 10 ⁻¹ mmHg or more, and the density is Since it is 20 to 100 kg / m ³ or less, it is extremely lightweight, and since it is not a fine particle shape but a porous sheet, it is remarkably excellent in handleability in the vacuum packaging process.

The thermoplastic resin used in the present invention means generally known polycarbonate resin, polymethacrylate resin, polystyrene resin, polyphenylene resin, polyarylate resin, polysulfone resin, polyethersulfone resin, poly Amorphous thermoplastic resins such as ether imide resins and polyethylene terephthalate resins, polyphenylene sulfide resins, polyamide resins, polypropylene resins, polyethylene resins, polyoxymethylene resins and other crystalline thermoplastic resins, It may be appropriately used in combination with the optimum foaming agent. Amorphous thermoplastic resins are preferred because of their ease of forming fine bubbles. However, even a crystalline resin such as a polyethylene terephthalate resin or a polyphenylene sulfide resin whose crystallinity can be controlled by molding conditions and whose crystallinity can be suppressed to a low level is preferably used similarly to the amorphous resin. More preferably, a polycarbonate resin,
They are polymethacrylate resin, polystyrene resin, and polyphenylene ether resin. Particularly preferably,
They are a polycarbonate resin containing so-called bisphenol A in its main chain and a polymethylmethacrylate resin containing in its main chain methyl methacrylate.

These resins may be used alone, but may be used in a blended form in order to improve the resin melt viscosity in the heated state during foaming and the retention of the foaming agent. further,
If necessary, known additives such as lubricants, heat stabilizers, and ultraviolet absorbers may be added to the extent that foaming properties are not significantly impaired. Further, for the purpose of reducing the cell diameter, an additive which can serve as a foam nucleating agent may be used.

The pore size of the porous sheet which is the filler of the present invention must be 1 to 20 μm. The pores of the porous body here are those having a foam shape, and are so-called foam-shaped cells in the form of a foam, and the bubble wall portion of the polyhedron portion aggregates on the sides of the polyhedron portion to form a line. In a porous body forming a columnar support, it refers to a portion constituted by its sides, and the pore diameter is a value obtained from an electron micrograph of an arbitrary cross section of the porous body in accordance with ASTM D-3576. Is. The pore size must be less than or equal to the mean free path of air at the vacuum packing decompression degree in order to reduce the heat transfer of air molecules. Therefore, if the pore diameter exceeds 20 μm, the degree of pressure reduction must be increased, and if the pore diameter is less than 1 μm, it tends to be difficult to obtain a low-density porous body, and this is limited. The pore size is preferably 1 to 15 μm,
More preferably 2 to 10 μm, particularly preferably 2 to 5
μm.

The continuous porosity of the porous sheet which is the filler of the present invention must be 90 to 100%. Those having a low value are limited because the air remaining in the independent pores in the porous body sheet after vacuum packaging diffuses throughout the porous body and the degree of reduced pressure immediately after vacuum packaging is not maintained. Therefore, in order to maintain the degree of reduced pressure during vacuum packaging, the higher the value, the better, preferably 95 to 100%, more preferably 9%.
It is 7 to 100%, particularly preferably 99 to 100%.

Here, the continuous porosity is ASTMD-28.
It is a value calculated from the independent porosity determined in accordance with No. 56, and the resin layer on the surface of the porous sheet is a non-porous resin layer, that is, a so-called foamed skin layer, the resin layer is thinly removed, Alternatively, it is a value of the continuous porosity measured in a practical use form as a vacuum heat insulating material in which a part of the resin layer is destroyed. As a method for removing the non-porous resin layer of the foam, a method of mechanically slicing and removing the entire resin layer thinly, or a method of mechanically forming a hole or groove in the resin layer from the outside In addition, when foaming is heated, the resin layer is plasticized with an additive or the like to facilitate bubble breaking, or heat is concentrated in the additive to generate heat, for example, a method of breaking the resin layer during the foaming process, etc. Can be appropriately selected. Preferably, it is a method of mechanically forming a hole using a needle or the like, or a slit groove using a blade such as a leather continuously from at least one surface of the porous sheet. The degree thereof may be appropriately determined depending on the depressurizing capacity and form of the vacuum packaging machine, as long as the gas inside the pores of the porous body is degassed within a predetermined time during vacuum depressurization.

The density of the porous sheet which is the filler of the present invention must be 20 to 100 kg / m ³ . The porous body density here is a value determined according to JIS K-6767. In order to reduce the effect of heat conduction of the resin solid portion, the density is preferably 20 to 80 kg / m ³ or less, more preferably 20 to 60 kg / m ³ , and particularly preferably 30 to 50 kg / m ³ . The lower limit of density is 20
It is kg / m ³ , and if it is less than this, the compressive strength of the porous body is lowered, so that it is contracted and deformed remarkably during vacuum packaging, so that its use is limited, and the upper limit tends to make a large contribution to the thermal conductivity of the solid itself. Limited.

The porous sheet used for the vacuum heat insulating material of the present invention preferably has a bubble film existence rate in the range of 60 to 100% for the purpose of enhancing the strength against compression during vacuum packaging. The bubble film existence rate is specifically determined as follows. First, from the enlarged photograph of an arbitrary cross section of the foam (observed at a magnification at which at least 100 cells of the foam can be observed) obtained by scanning electron microscope observation or the like, the presence or absence of the defect portion of the cell wall and its shape At least 20 or more bubbles that can be sufficiently observed are selected. Next, using an image analysis device or the like, the cross-sectional area of each of the selected bubbles is calculated, and then the total sum (this value is set to A) is calculated. Further, for bubbles having a defect portion, after determining the area of each defect portion (the area when the defect portion is projected perpendicularly to the cross section so that it can be measured on the photograph) by an image analysis device or the like, The total sum (this value is B) is calculated. Here, as the bubble wall existence rate, a value (%) obtained by {1- (B / A)} × 100 is adopted. Here, the bubble wall existence rate is 100
%, It is considered that microcracks, which are difficult to observe in a magnified photograph or the like, exist in the cell wall and the cells are connected. In particular, those having a cell wall presence rate of 60% or more have a partially lacking portion in the cell wall, but since the cell wall stretched during foaming is substantially present, the compressive strength becomes high. Those having a bubble wall existence rate of less than 60% are limited because the compressive strength tends to decrease. The bubble wall existence rate is preferably 80 to 100%, more preferably 90 to 100%,
More preferably 95 to 100%, particularly preferably 98.
~ 100%. Usually, a porous sheet having such a form in which cell walls are present often depends on the manufacturing method of the sheet, and can be obtained by a foaming method described later.

The thickness of the porous sheet needs to be increased depending on the heat insulation performance required for each application, but with a thick sheet, the foaming method reduces the thermal efficiency and the phase separation method removes the solvent. There is a problem in productivity, such as taking time, and the uniformity of the pores of the obtained porous body tends to be poor, so that the thickness thereof is limited. The thickness of the porous sheet is preferably 0.1 to 10 mm, more preferably 0.5 to 8 mm, and particularly preferably 1 to 5 mm. Therefore, in order to secure the required thickness of the porous sheet, it is necessary to stack thin sheets produced by the respective production methods with good productivity. Further, the porous body sheets may be laminated simply by stacking, and if necessary, a pressure-sensitive adhesive or an adhesive may be used as long as the removal of the gas from the bubbles by vacuum decompression is not hindered. Furthermore, by sandwiching a material that suppresses radiant heat transfer such as aluminum foil between the porous material sheets that are laminated to suppress the radiant heat transfer of the vacuum heat insulating material, a vacuum with improved heat insulation performance can be obtained. Can be used as a heat insulating material.

As a method for producing the porous sheet as the filler of the present invention, known resin foaming methods such as impregnation foaming method, extrusion foaming method and phase separation method can be used. Impregnation foaming method,
A multi-stage foaming method is preferably used as the extrusion foaming method.
Further, it is particularly preferable to set the expansion ratio of the first stage to 1.5 to 7 times. This aims at forming a large number of foam nuclei in the first stage of foaming, suppresses the foaming ratio, and increases the bubble pressure inside the bubbles formed in the foam formed by primary foaming after the second stage of foaming. This is to increase the expansion ratio and break the bubbles. Specifically, an extruded sheet of thermoplastic resin is wound up, and in that form is impregnated with a high-pressure blowing agent gas in an autoclave, and the impregnated sheet is heated by a heating medium such as hot air, steam, or far infrared rays to be foamed. While it can be produced by a method of breaking bubbles.

Also, a known phase separation method can be adopted. Specifically, after uniformly dissolving and mixing the resin and the solvent, phase separation is performed in a state where a sheet having a constant thickness is obtained, and in that state, the solvent is extracted to obtain a porous body sheet. Is the way. The solvent used, the phase separation conditions and the like can be appropriately selected depending on the resin used. Among the above production methods, the bubble wall existence rate is 6
In order to obtain a sheet of 0 to 100%, an impregnation foaming method and an extrusion foaming method using a physical foaming agent capable of forming fine cells are preferable.

As the physical foaming agent used in the present invention, solvent-based foaming agents, organic and inorganic gas-foaming agents used for generally known foams can be appropriately selected. Carbon dioxide is particularly preferable in order to increase the number of cell nuclei per unit volume of the foam as much as possible, that is, to reduce the cell diameter at a constant expansion ratio. Further, for the purpose of increasing the number of bubble nuclei of the foaming agent, carbon dioxide may be used together with or additionally impregnated with other inorganic gas. The amount of the foaming agent is appropriately selected depending on the type of the thermoplastic resin and the foaming agent to be used, but in general, when the amount of impregnation is small, the number of cell nuclei is small, and therefore the amount is limited. It is limited because the magnification is suppressed. In the combination of polycarbonate resin, polymethylmethacrylate resin and carbon dioxide gas, the impregnation amount is used in the range of 5 to 15 parts by weight, preferably 7 to 15
The weight is more preferably 8 to 15 parts by weight.

When the physical properties of the porous sheet used in the present invention cannot be satisfied by ordinary primary foaming, the obtained porous sheet is again impregnated with a physical foaming agent, that is, so-called additional, and then foamed again to foam the foam of the present invention. It is also possible to obtain This is a method for increasing the bubble pressure inside the bubbles formed in the foam and making it easier to break the bubbles after the secondary foaming. It goes without saying that a multi-stage foaming method in which impregnation and foaming are further carried out can be adopted if necessary.

As the physical foaming agent additionally added to the secondary and subsequent foaming, known gases such as carbon dioxide gas, nitrogen and air can be appropriately selected in consideration of the foaming temperature, the foaming ratio, the open cell formation rate and the like. . The amount of the secondary foaming agent is also appropriately selected according to the types of the thermoplastic resin and the foaming agent used as in the case of the primary. Generally, if the impregnated amount is small, the communication rate is low, and therefore the amount is limited. In the case of a combination of a polycarbonate resin, a polymethylmethacrylate resin and carbon dioxide gas, the impregnation amount is 8 to 40 parts by weight, preferably 10
-30 parts by weight, more preferably 12-25 parts by weight.

As the gas barrier packaging material used in the vacuum heat insulating material of the present invention, a known gas barrier resin such as polyvinylidene chloride resin, ethylene vinyl alcohol resin, polyacrylonitrile resin, polyamide resin or the like is used. A single-layer or multi-layer film, and a laminate of polyethylene terephthalate-based resin, polypropylene-based resin, and polyethylene-based resin film for imparting thermoformability and heat-sealing property to them are used. Further, in order to secure a gas barrier property for a long period of time, a film laminated with aluminum foil or vapor-deposited with aluminum is preferably used.

As the method for producing the vacuum heat insulating material of the present invention, the method for producing the powder vacuum heat insulating material which has been studied conventionally is applied. However, in the present invention, since the material to be filled is a sheet, its handleability is remarkable. Be improved. As described above, since the present invention does not fill fine particles, it is not necessary to use a breathable inner bag or the like, and a generally known bag-shaped or box-shaped barrier packaging material having a good barrier property against air, The laminated porous body sheets may be put in and vacuum packaged by a known vacuum packaging machine. At that time, it is preferable that the porous sheet of thermoplastic resin is laminated in at least two layers and vacuum-packed with a gas barrier packaging material. Further, if necessary, it is also possible to appropriately vacuum-pack the volatile component from the resin and the adsorbent such as air and water passing through the packaging material at the same time.

[0025]

EXAMPLES The present invention will be described in more detail with reference to examples.

[0026]

Example 1 Pellets of polycarbonate resin (weight average molecular weight 56,000) produced from diphenyl carbonate and 2,2-bis (4-hydroxyphenyl) propane by the method described in JP-A-3-68627. Was melt-extruded using a T-die extruder at a cylinder temperature of 320 ° C. to prepare an extruded sheet having a thickness of 1.1 mm.

A sample of 85 × 85 mm was cut out from this extruded sheet, placed in an autoclave, and carbon dioxide gas was added to 4
The mixture was press-fitted to 0 kg / cm ² and left at ambient temperature of 5 ° C. for 24 hours. The pressure was released, and aging was performed at room temperature to adjust the carbon dioxide gas impregnation amount to 8 parts by weight with respect to the sample weight. This impregnated sample was immersed in a silicone oil bath at a temperature of 150 ° C. for 30 seconds to be heated and foamed.
A primary foam sheet having a size of 0 × 130 mm and a magnification of 3.5 was obtained.

The primary foamed product was again placed in the autoclave, carbon dioxide gas was similarly injected up to 40 kg / cm ^2, and the mixture was allowed to stand at an ambient temperature of 5 ° C. for 24 hours. The pressure was released, and aging was performed at room temperature to adjust the impregnated amount of carbon dioxide gas to 19 parts by weight based on the weight of the sample. This impregnated sample was subjected to a temperature of 19
When it was immersed in a silicone oil bath at 0 ° C for 15 seconds and heated for foaming, it had a thickness of 3.3 mm and a size of 250 x 250.
In mm, a porous sheet having a density of 46 kg / m ³ , a cell diameter of 9 μm, and a cell wall existence rate of 98% was obtained. On this porous sheet, the slit positions were shifted on both sides of the sheet, and a slit groove having a distance of 5 mm and a depth of 2.5 mm was continuously formed from both sides with a leather, and then the sheet was sampled at 200 × 200 mm square. A part of this sample was cut out and the open cell ratio was measured and found to be 99.9%.

In a state in which eight porous sheets of this size are laminated, PET / aluminum foil / 100 μm thick
Barrier film made of PE (oxygen permeability of 0.3cc
Below / atm · m ² · 24 hr, 20 ° C., 0% RH) was put in a bag-made product. With a vacuum packaging machine, vacuum packaging with the vacuum reduced to 0.1 mmHg,
A vacuum insulation material was obtained.

The heat insulating material thus obtained was measured by a thermal conductivity measuring device (AS
According to TMC-518), the thermal conductivity was 0.007 kcal / m · h · ° C.
The weight of this heat insulating material was 54 g, which was extremely excellent in lightness as compared with the comparative example.

[0031]

Example 2 Size 16 obtained under the same conditions as in Example 1
The primary foam sample of × 16 mm was impregnated again in the same manner as in Example 1 to obtain a foam having a carbon dioxide gas impregnation amount of 30 parts by weight. When this impregnated sample was immersed in a silicone oil bath at a temperature of 190 ° C. for 45 seconds and heated to foam,
Thickness 2.7 mm, size 250 x 250 mm, density 7
A porous sheet having 8 kg / m ³ , a cell diameter of 8 μm, and a cell wall presence rate of 92% was obtained. On this porous sheet, the slit positions were shifted on both sides of the sheet, and slit grooves with a gap of 5 mm and a depth of 1.8 mm were continuously formed from both sides with a leather, and then the sheet was sampled into a 200 × 200 mm square. A part of this sample was cut out and the open cell ratio was measured and found to be 99.8%.

Vacuum insulation was carried out in the same manner as in Example 1 to obtain a heat insulating material having a thermal conductivity of 0.008 kcal / m · h · ° C. The weight of this heat insulating material was 69 g, which was extremely excellent in lightness as compared with the comparative example.

[0033]

Example 3 A polymethacrylate resin (Delpet 80N, manufactured by Asahi Kasei Kogyo Co., Ltd.) was melt extruded at a cylinder temperature of 230 ° C. using a T-die extruder to a thickness of 0.
A 4 mm extruded sheet was created. 9 from this extruded sheet
A 0 × 90 mm sample was cut out, and n-pentane: methanol was added to a mixed solvent having a volume ratio of 80:20 at room temperature for 24 hours.
The sample was immersed for 17 hours to obtain a sample impregnated with 17 parts by weight of the solvent. 24 hours at room temperature
Aging was performed for a period of time to adjust the solvent impregnation amount to 6 parts by weight. When this impregnated sample was immersed in a 120 ° C. silicon oil bath for 30 seconds for primary foaming, 63 × 63 m
A foam sheet having an expansion ratio of m and a foaming ratio of 5 was obtained. Carbon dioxide gas was pressed into the foamed body in an autoclave up to 40 kg / cm ^2, and the foamed body was left standing at an ambient temperature of 5 ° C. for 24 hours. The pressure was released, and aging was performed at room temperature to adjust the carbon dioxide gas impregnation amount to 13 parts by weight with respect to the sample weight. The impregnated samples, when heated by immersion for 20 seconds in a silicon oil bath temperature of 140 ° C., was foamed, thickness 1.1 mm, size 250 × 250 mm density 60 kg / m ^3, the cell diameter 1
A porous sheet having a thickness of 8 μm and a bubble wall existence rate of 85% was obtained.
This porous sheet has a depth of 0.7 mm and a pitch of 5 mm.
After shifting the slit position on both sides of the sheet and forming continuous slit grooves with leather from both sides, 200 × 200
It was sampled in mm square. A part of this sample was cut out and the open cell ratio was measured and found to be 99.2%. Twenty porous sheets of this size were laminated and vacuum-packaged in the same manner as in Example 1 to obtain a thermal conductivity of 0.00
A heat insulating material having a performance of 9 kcal / m · h · ° C was obtained. The weight of the heat insulating material was 50 g, which was extremely excellent in lightness as compared with the comparative example.

[0034]

[Example 4] Polycarbonate resin (Teijin Kasei Co., Ltd.)
Manufactured by Panlite K1300) with dioxane: cyclohex
Sun = 70: 30% by volume of mixed solvent, concentration 7.5%
%, The solution was uniformly dissolved at 60 ° C. This solution
After cooling to room temperature, the aluminum pan becomes 2mm thick
Was transferred as follows. Quenching and freezing in liquid nitrogen together with aluminum pan
After tying and phase separation, the solvent was removed using a freeze dryer.
It was The resulting porous sheet had a cell diameter of 7 μm and a cell wall
Presence rate is 0%, thickness is 1.8 mm, and density is 95 kg / m. ³so
there were. This porous sheet is used as the sheets of Examples 1 to 3.
In comparison, the compression strength at the fingertip tended to be inferior.

Eight sheets of the porous sheet of 200 × 200 mm square size were laminated and vacuum-packed in the same manner as in Example 1 to obtain a vacuum heat insulating material. When the obtained heat insulating material was measured with a thermal conductivity measuring device (based on ASTM C-518), the thermal conductivity was 0.0095 kcal / m · h.
・ It was a performance of ° C. The weight of this heat insulating material was 58 g, which was very excellent in lightness as compared with the comparative example.

[0036]

[Comparative Example] White carbon (density 300 kg / m ³ :
Vacuum-dried average agglomerate diameter 3.5-4 μm)
It was filled in a rectangular parallelepiped inner bag made of kraft paper with a size of 200 × 200 × 25 mm, sealed, and then lightly compressed by a pressing device. This inner bag was put in the same bag as the gas barrier film bag used in Example 1 and vacuum-packed in the same manner as in Example 1 to obtain a powder vacuum heat insulating material. The thermal conductivity of this heat insulating material was almost the same as that of the example, but the weight was 330 g, which was heavier than that of the example, and the packaging process was complicated.

[0037]

EFFECT OF THE INVENTION The vacuum heat insulating material of the present invention uses a resin foam sheet having a small cell diameter and an open cell as a filler, and therefore, compared with a conventional material using inorganic fine particles as a filler, The vacuum packaging process is simplified and the weight of the heat insulating material can be remarkably reduced.

Claims (1)

[Claims] 1. A pore size of 1 to 20 μm and an open cell rate of 90 to
A vacuum heat insulating material, characterized in that a 100% thermoplastic resin porous sheet having a density of 20 to 100 kg / m ³ is vacuum packaged with a gas barrier packaging material.