JPS61153481A - Heat insulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat insulator used in refrigerators, frozen prefabricated products, and the like.

Prior Art FIG. 4 shows a conventional heat insulator. 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, JP-A-57
As shown in No. 133870, a proposal has been made to use a rigid urethane foam having open cells as the core material.

To explain JP-A-57-13870 with reference to FIG. 4, 1 is a heat insulating structure in which a hard urethane foam 2 having open cells is covered with a container 3 made of an airtight thin film, and the inside is sealed with zero The pressure is reduced to .001 mHf and the chamber is sealed. The hard urethane foam 2 has a closed cell ratio of approximately 80 to 9.
It is characterized by vacuum degassing of commercially available materials with a size of about 0.0 cm 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 bubble membrane of the hard urethane foam 2 has strong resin strength even under high temperature and high humidity conditions, so the bubbles may not burst. Therefore,
It is possible that the open cell ratio cannot reach 100%. Therefore, even if the initial thermal conductivity is excellent, the internal pressure of the heat insulating structure 1 will increase over time due to gases such as air, water vapor, and fluorocarbon gas that gradually diffuse from the closed cell parts, and the thermal conductivity will decrease. It's getting bigger. For example, 30
cm x 30cm x 2cm (volume 18007
) and has a core material of hard urethane foam 2 with an average cell diameter of about 10011 m, when the open cell ratio is 98%, o, oo 1rtrm
Even if the pressure is reduced to Hq, approximately 36a is theoretically contained in a 2-inch closed cell! tD gas (1 sock x o,
o2) diffuses into the open cell portion 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.

It is conceivable that the above-mentioned approximately 36 d of gas ultimately increases the internal pressure from 0.001 mmHg to 15 m1q and deteriorates the thermal conductivity to 0.0201 al/mh'c or more.

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
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, and maintains the heat insulation performance of the heat insulator over a long period of time.
The purpose is to establish quality reliability.

Means for Solving the Problems The present invention solves the above problems by using less than 100 pieces.
A foam having an open cell ratio of 0% or more is placed in a pressure vessel and pressurized with pressurized gas to form the core material of the heat insulator.

Function: As in the above configuration, the cell membrane of the foam is broken by applying pressure.
Since the core material with 100% open cell ratio is covered with a container made of metal-plastic laminate film to reduce the internal pressure, the internal pressure of the insulation can be uniformly reduced to a predetermined pressure with a short evacuation. Since there is no internal pressure, there is no increase in internal pressure over a long period of time, and the initial insulation performance is maintained.

EXAMPLE Hereinafter, an example 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 after aging at room temperature,
It is cut into a predetermined size.

In the table, polyols are propylene oxide (hereinafter referred to as P) using an aromatic diamine as an initiator.

Hydroxyl value 442mgKO obtained by addition polymerization of
The foam stabilizer is a silicone surfactant F-335 manufactured by Shin-Etsu Chemical Group, the blowing agent is Showa Denko K.K. Freon R-11, and the catalyst is dimethylethanolamine.

The bubble communication agent is calcium stearate manufactured by Nippon Yushiki. The organic polyinsyanate was crude diphenylmethane diincyanate 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. After that, the hard urethane foam 4 is placed in the pressure vessel 6, and the pressure in the pressure vessel 6 is reduced to 0.01 KM-, and 2. 3, 4.5 to ν
Pressure-treated hard urethane foam 6
A part of this is shown in A1-A3 as an example,
AA-B is shown in the table as a comparative example. In addition, the density of the hard urethane 7 ohm 4 and the pressure-treated hard urethane 7
The open cell ratio of Ohm 6 is also shown in the table. After this, 6Ky/a
After pressurizing the container to 120° C. for about 2 hours to evaporate the adsorbed moisture, the container 7 was covered with a metal-plastic laminate film made of a laminate of aluminum-deposited polyester film and polyethylene film, and the inside was sealed. o, o s ttmHqi to reduce the pressure 1. The heat insulator 8 was obtained by sealing. 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 30
The thermal conductivity after several 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 A4.

As is clear from the table, the open cell ratio increases when the pressure treatment is performed, and at about s Kplct1, the open cell ratio increases to 100.
%. This is because when the pressure in the closed cells is at least 1 to 5 to 6 or more, all the cell membranes cannot withstand the pressure and burst. However, in the case of hard urethane foam 4 in which closed cells account for 40% or more, deformation and shrinkage occur. This is 1 1
Rather than stress being applied locally in the form of a single cell membrane, the probability of stress being applied to a series of closed cells increases, and as a result of stress being applied to a wide area of the hard urethane foam 4, the 7-ohm urethane 4 shrinks, deforms, and breaks. It is thought that it will happen.

Since this pressure-treated hard urethane foam 6 with an open cell ratio of 100% and no closed cell portions is used as the core material of the heat insulator 8, the internal pressure of the heat insulator 7 is uniformly maintained through the open cells by a short time of evacuation. The pressure can be reduced to low pressure, making it highly efficient in mass production. Furthermore, 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 having an open cell ratio of less than 10% and 60% or more is placed in a pressure vessel and pressurized with pressurized gas to increase the open cell ratio to 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) Since there are no closed cells that contain gas, even if the insulation is left for a long time, there will be no gas diffusion from the closed cells and no pressure increase will occur, so the insulation performance of the insulation will deteriorate. This is to ensure stability of quality.

[Brief explanation of drawings]

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. 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... Heat insulator. Figure 3 Figure 4

Claims (1)

[Claims] A foam having an open cell ratio of less than 100% and 60% or more is placed in a pressure vessel, pressurized with pressurized gas to make the open cell ratio 100%, and then covered with a container made of a metal-plastic laminate film. An insulator whose interior is sealed and depressurized.