JPH0463992B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a heat insulator used in refrigerators, frozen prefabricated products, and the like. BACKGROUND OF THE INVENTION FIG. 4 shows a heat insulating body of the present invention. The configuration of the conventional example will be explained below with reference to FIG. 4. In recent years, attention has been paid to the use of a heat insulator with a reduced internal pressure for the purpose of improving the heat insulation performance of a heat insulating box.
As the core material of this heat insulating body, powder such as perlite, honeycomb, foam, etc. are used. For example, as shown in JP-A-57-133870, a proposal has been made to use a hard urethane foam having open cells as the core material. To explain JP-A-57-13870 with Figure 4, in the figure 1 is a heat insulating structure, 2 is a rigid urethane foam having open cells.
is covered with a container 3 made of an airtight thin film, and the inside is sealed.
The pressure is reduced to 0.001mmHg and it is sealed. The hard urethane foam 2 is characterized in that a commercially available material with a closed cell ratio of about 80 to 90% is vacuum degassed under high temperature and high humidity to break the cell membrane and obtain open cells. Problems to be solved by the invention However, in such a heat-insulating structure,
The cell membrane of the hard urethane foam 2 has strong resin strength even under high temperature and high humidity conditions, so the cells may not burst, and it is conceivable that the open cell rate may not reach 100%. Therefore, even if the initial thermal conductivity is excellent, the thermal insulation structure 1
The internal pressure increases due to gases such as air, water vapor, and chlorofluorocarbon gas that gradually diffuse from the closed cell portion.
Thermal conductivity increases. for example,
Hard urethane foam 2 with a size of 30 cm x 30 cm x 2 cm (volume 1800 cm ³ ) and an average cell diameter of about 100 μm.
In the heat insulating structure 1 having a core material ^of
The gas (1800cm ³ ×0.02) diffuses into the open cell part, where the pressure is gradually reduced while being affected by the diffusion resistance of the cell membrane. According to experiments, it took about 30 days at room temperature to completely reach pressure equilibrium, and 1 to 3 days even in an atmosphere of 80 to 100°C, which is close to the heat resistance temperature of the rigid urethane foam 2. Then, the aforementioned approximately ^36cm3 of gas will ultimately increase the internal pressure from 0.001mmHg to 15mm
Increase the thermal conductivity to 0.020Kcal/mh by increasing the temperature to Hg.
It is conceivable that the temperature may deteriorate above ℃. To prevent this, it will be necessary to maintain the heat insulating structure 1 at a temperature of at least 80 to 100°C and continue to evacuate it with a vacuum pump for one day or more. That is, by this operation, the gas remaining in the closed cell portion is exhausted through the cell membrane, and even if there is a closed cell portion, the pressure can be reduced to a predetermined pressure. However, in production, only one unit of exhaust equipment can be manufactured per day using this operation, and mass production is extremely difficult. Furthermore, high temperature and high humidity treatment also requires large-scale equipment, which is also a problem for mass production. In view of the above problems, the present invention greatly improves productivity by reducing the pressure to a predetermined pressure in a short time, maintains the insulation performance of the heat insulator over a long period of time, and improves quality reliability. The purpose is to establish gender. Means for Solving the Problems In order to solve the above-mentioned problems, the method for manufacturing a heat insulating body of the present invention is to produce a foam made of a hard urethane foam having an open cell ratio of less than 100% and 60% or more in a pressure vessel. Pressure is applied to the foam at a pressure of 5 kg/cm2 or ^more to burst the closed cells of the foam, and the burst insulation is placed in a container made of metal-plastic laminate film, the inside is depressurized, and the container is opened. It is sealed. Effect As shown in the above structure, the cell membrane of the foam is broken by pressurization, and the core material with an open cell ratio of 100% is made of metal.
Since the internal pressure is reduced by covering the container with a plastic laminate film, the internal pressure of the insulation can be uniformly reduced to the specified pressure with a short evacuation, and since there is no closed cell part, the internal pressure can be reduced for a long period of time. There is no rise, and the initial insulation performance is maintained. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the figure, 4 is a foam made of hard urethane foam (hereinafter referred to as hard urethane foam) that is foamed and hardened using the raw materials shown in the table below, and is cut into a predetermined size after being aged at room temperature. be.

【table】

[Table] In the table, polyols are produced using propylene oxide (hereinafter referred to as PO) using an aromatic diamine as an initiator.
Hydroxyl value 442mg obtained by addition polymerization of
KOH/g polyether polyol. The foam stabilizer is a silicone surfactant manufactured by Shin-Etsu Chemical.
F-335, the blowing agent is Freon R-11 manufactured by Showa Denko Co., Ltd.
The catalyst is dimethylethanolamine. The bubble communication agent is calcium stearate manufactured by Nippon Oil & Fats Co., Ltd. The organic polyisocyanate was crude diphenylmethane diisocyanate with an amine equivalent weight of 136 manufactured by Nippon Polyurethane Co., Ltd. Various combinations of these raw materials are foamed to obtain the hard urethane foam 4. Thereafter, the hard urethane foam 4 is placed in the pressure vessel 5, and the inside of the pressure vessel 5 is heated to 0.01.
A pressure-treated hard urethane foam 6 was obtained by reducing the pressure to Kg/cm ² and increasing the pressure to 2, 3, 4, and 5 Kg/cm ² , some of which are shown in Examples No. 1 to No. 3, Comparative examples are shown in Nos. A to B in the table. The table also shows the density open cell ratio of the hard urethane foam 4 and the open cell ratio of the pressure-treated hard urethane foam 6. After this, the product was pressurized to 5Kg/cm ² and heated to 120℃.
The container was heated for about 2 hours to evaporate the adsorbed water, then covered with a container 7 made of a metal-plastic laminate film made of a laminate of an aluminum-deposited polyester film and a polyethylene film, and the inside was reduced to 0.05 mmHg and sealed. A heat insulator 8 was obtained. The evacuation time at this time was 3 minutes. The initial value of thermal conductivity of the obtained heat insulator 8 immediately after sealing and
The thermal conductivity after 30 days is also shown in the table. A similar experiment was conducted using commercially available phenol foam, and the results are added to the table as Example No. 4. As is clear from the table, the open cell ratio increases with pressure treatment and reaches approximately 5 kg/ ^cm2 .
It turned out to be 100%. This is because the pressure in closed cells is at least 1Kg/cm ² , but when a pressure of 5Kg/cm ² or more is applied, all the cell membranes cannot withstand the pressure and burst. However, closed cell
In the case of hard urethane foam 4, which accounts for 40% or more, deformation and shrinkage occur. This is because stress is not applied locally to each cell film, but the probability that stress is applied to a series of closed cells increases, and as a result, stress is applied to a wide area of the hard urethane foam 4, causing the urethane foam 4 to shrink. - It is thought that deformation and destruction may occur. Since this pressure-treated hard urethane foam 6 with a 100% open cell ratio and no closed cell portions is used as the core material of the heat insulator 8, the internal pressure of the heat insulator 7 can be uniformly maintained through the open cells by short-time evacuation. The pressure can be reduced to a predetermined pressure, resulting in excellent mass production efficiency. Further, since there is no closed cell portion containing gas, even if the heat insulator 7 is left for a long period of time, there will be no gas diffusion from the closed cell portion, and no pressure increase will occur. Therefore, the heat insulating performance of the heat insulator 7 does not deteriorate over a long period of time and contributes to ensuring quality. Effects of the Invention As is clear from the above description, the present invention provides the following effects. (a) A foam with an open cell ratio of less than 100% and 60% or more is placed in a pressure vessel and pressurized with pressurized gas to make the open cell ratio 100%. - By covering the container with a plastic laminate film and reducing the internal pressure, the internal pressure can uniformly reach a predetermined pressure in a short time, ensuring productivity during mass production. (b) In addition, since the foam is formed by pressurizing it in a pressure vessel, it is easy to break the walls of closed cells, and it is easy to apply pressure, so it is easy to obtain an open cell ratio of 100%. Since bubbles are broken only by pressure, there is no need to use moisture or alkali to separate the bubbles from drying at high temperatures. In other words, if the foam is kept at a high temperature, the internal pressure of the closed container may increase due to changes over time, but since pressure is only being applied, even if the foam is dried, it will only take a short time. It's okay. (c) Since there are no closed cells that contain gas, even if the insulation is left unused for a long period of time, there will be no gas diffusion from the closed cells and no pressure increase will occur.Therefore, the insulation performance of the insulation is This ensures quality stability without deterioration.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a rigid urethane foam according to an embodiment of the present invention, FIG. 2 is a sectional view of the pressure vessel and the rigid urethane foam placed in a pressure vessel and being subjected to pressure treatment, and FIG. 3 is a cross-sectional view of the rigid urethane foam according to an embodiment of the present invention. Cross-sectional view of the insulation,
FIG. 4 is a sectional view of a conventional heat insulating structure. 4...Hard urethane foam (foam), 5...
...Pressure vessel, 6...Hard urethane foam, 7...
...Container, 8...Insulator.

Claims (1)

[Claims] 1 A foam made of hard urethane foam having an open cell ratio of less than 100% and 60% or more is pressurized in a pressure vessel at a pressure of 5 kg/cm ² or more to burst the closed cells of the foam, and the foam is broken. A method for manufacturing a heat insulating body, which comprises storing the heat insulating body in a container made of a metal-plastic laminate film, reducing the pressure inside the container, and then sealing the container.