JPS61153478A - 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 for use in refrigerators, freezers, etc.

BACKGROUND OF THE INVENTION FIG. 3 shows a conventional heat insulator. The configuration of the conventional example will be explained below with reference to FIG.

In recent years, attention has been paid to the use of a heat insulating body with a reduced internal pressure in order to improve the heat insulation performance of the 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-57-1338
As shown in No. 70, a proposal has been made to use a hard urethane foam having open cells as the core material. This Japanese Patent Application Laid-Open No. 57-133870 is explained with reference to Fig. 3. In Fig. 10, 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. The pressure is reduced to 0.001B Hg and the chamber is sealed. The hard urethane foam 2 has a closed cell ratio of approximately 80 to 9.
It is characterized by the fact that a commercially available material with a size of about 0.0 cm 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 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. It is conceivable 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 rise over time due to gases such as air, water vapor, and fluorocarbon gas gradually diffusing from the closed cell portions.
Thermal conductivity increases. For example, 3oc
III×3ocI11×2α (volume 1800cfIl)
In the heat insulating structure 1 having a core material of hard urethane foam 2 with a size of 9 and an average cell diameter of about 300 μm,
When the open cell ratio is 8 inches, even if the pressure is reduced to 0.001 Hq, theoretically about 3e7 gas (1800i However, it diffuses into the open cell part where the pressure is gradually reduced. Further, 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. The approximately 36-degree gas in the 2% closed cell portion ultimately raises the internal pressure to 0.001. H
It is conceivable to increase the thermal conductivity from g to 15 trrrr H9 to deteriorate the thermal conductivity to 0.0207/mh°C or more.

To prevent this, it will be necessary to maintain the heat insulating structure 1 at a temperature of at least 80-100'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 mass production, this operation can only produce one exhaust system per day, making mass production very difficult. Additionally, high-temperature, high-humidity processing requires large-scale equipment, which also takes time for mass production.

There is a problem.

In view of the above-mentioned problems, the present invention aims to significantly improve productivity by reducing the pressure to a predetermined pressure in a short time, maintain the insulation performance of the heat insulator over a long period of time, and ensure quality reliability. shall be.

Means for Solving the Problems In order to achieve the above object, the present invention provides a heat insulating material using a hard urethane foam made from thermoplastic resin powder as a raw material of an organic polyisocyanate, a polyol, a catalyst, a blowing agent, and a cell communication agent. The above-mentioned hard urethane 7 has a core material of which the cell membrane is torn during the foaming process and the open cell ratio is 100%.
The ohm is covered with a container made of metal-plastic laminate film.

Function Since the present invention reduces the internal pressure as described above, it is possible to uniformly reduce the internal pressure of the heat insulating body to a predetermined pressure by evacuation for a short time, and since there is no closed cell portion, the internal pressure does not increase over a long period of time. It maintains its initial insulation performance. EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

In the figure, 4 is a hard urethane foam foamed and cured using the R-RIM high-pressure foaming machine using the raw materials shown in the table below.
After processing at room temperature, it is cut to the specified size.

In the table, polyol A uses aromatic diamine as an initiator and propylene oxide (hereinafter referred to as P).

Hydroxyl value 442#KOH obtained by addition polymerization of
/g of polyether polyol. Moreover, polyol B is sucrose and ethylenediamine.

This is a polyether polyol with a hydroxyl value of 400 jWKOH/, 9 obtained by addition polymerization of Po using diethylene glycol as an initiator. The foam stabilizer is silicone surfactant F-3o6 manufactured by Shin-Etsu Chemical Co., Ltd., the foaming agent is Freon R-11 manufactured by Showa Denko Co., Ltd., and the catalyst is tetramethylhexyl diamine manufactured by Kako Soap Co., Ltd., air bubbles. The communication agent is Fron7in UF-20, a polyethylene powder manufactured by Seitetsu Kagaku Co., Ltd.
It is. Organic polyisocyanate A is manufactured by Shikinichi Yakuhin Kogyo (
Takenate ■81-12P (7min equivalent weight 16o
), organic polyisocyanate) B is Japanese polyurethane (
This is crude diphenylmethane diiricyanate (amine equivalent weight: 136) manufactured by Co., Ltd. Foaming was carried out using various combinations of these raw materials, and some of these materials were used as examples in Examples 1 to 6. &A and &B are shown in the table as comparative examples.

The density and open-cell ratio of the obtained rigid urethane foam 4 are also shown in the table.The obtained rigid urethane foam 4 was then heated at 100°C for about an hour to evaporate the adsorbed moisture and form an aluminum-deposited polyester film. It is covered with a bag-shaped container 6 made of a metal-plastic laminate film with a polyethylene film laminate structure, and the inside is 0-O
The pressure was reduced to 5 nm Hg, and the heat insulator 6 was obtained. The evacuation time at this time was 3 minutes. The initial thermal conductivity of the obtained heat insulator 6 immediately after sealing and the thermal conductivity after 30 days are also shown in the table. Thermal conductivity is made by Shinku Riko Co., Ltd. -Ma
Measurements were made tic at an average temperature of 24°C.

As is clear from the table, 5 to 50 parts by weight of thermoplastic resin powder consisting of polyethylene was added as a cell communication agent to 10 parts by weight of polyol to various blended raw materials of polyol, organic isocyanate, catalyst, foam stabilizer, and 9 blowing agents. The hard urethane foam 4 foamed using
00% and the foam strength was found to be able to withstand atmospheric compression when the heat insulator was 6. Furthermore, if the cell communication agent is less than 5 parts by weight, the open cell ratio will be less than 100%;
If the amount is more than 0 parts, the viscosity of the reaction raw materials will increase, and the raw materials will not be mixed sufficiently during foaming, resulting in a foam with poor foaming, which is difficult to implement.

Regarding the formation of open cells, during the foaming process, the polyethylene powder, which is a thermoplastic resin, dispersed in the cell membrane of the hard urethane foam 4 is melted by the heat of the formation reaction of the hard urethane foam 4, which reaches 120 to 140 ° C. A part of the bubble membrane where the polyethylene powder was located became hollow,
It is thought that the bubbles appear to be broken and the cells become open, but the details of this process have not yet been elucidated. By using the hard urethane foam 4, which has an open cell ratio of 100% and has no closed cell portions, as the core material of the heat insulator 6, when exhaust is performed, the internal pressure of the heat insulator d is uniformized through the open cells in a short time. The pressure can be reduced to a predetermined pressure, resulting in excellent mass production efficiency.

Furthermore, since there is no closed cell portion containing gas, even if the heat insulator 6 is left for a long period of time, gas will not diffuse from the closed cell portion and no pressure will increase. Therefore, the heat insulating performance of the heat insulator 6 does not deteriorate over a long period of time, contributing to quality assurance.

Effects of the Invention As is clear from the above description, the present invention provides the following effects.

(-) A hard material obtained by mixing and foaming 5 to 50 parts by weight of thermoplastic resin powder to 100 parts by weight of polyol as an organic polyincyanate, a polyol, a catalyst, a foam stabilizer, a foaming agent, and a cell communication agent. Urethane foam has an open cell ratio of 1o.

Since the cell has a cell structure with no closed cell parts, by covering it with a container made of metal-plastic laminate film and reducing the internal pressure, the internal pressure can uniformly reach the specified pressure in a short time, making it possible for mass production. This makes it possible to ensure productivity over time.

(b) Since there is no closed cell part containing gas, even if the heat insulator is left for a long time, there will be no gas diffusion from the closed cell part and no pressure increase will occur. Therefore, the heat insulation performance of the heat insulator will not deteriorate. This ensures quality stability.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a rigid urethane foam according to an embodiment of the present invention, FIG. 2 is a sectional view of the same heat insulating body, and FIG. 3 is a sectional view of a conventional heat insulating structure. 4...Hard urethane foam, 6...
Container, 6...Insulator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 = Figure 3 4... 4 more) ``Tsu L9zke-4 5... Customer Waka 6... Ha 11 Den

Claims (1)

[Claims] Organic polyisocyanates, polyols, catalysts, foam stabilizers,
5 to 50 parts by weight of thermoplastic resin powder is mixed with 100 parts by weight of polyol as a blowing agent and a cell communication agent, and foamed to form a rigid urethane foam with an open cell structure. - A heat insulator covered with a container made of plastic laminate film, the inside of which is sealed under reduced pressure.