JPS6361588B2 - - 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. Prior Art 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 insulator 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, 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. This Japanese Patent Application Laid-open No. 57-133870 is explained with reference to Fig. 3. In the figure, 1 is a heat insulating structure, in which a hard urethane foam 2 with open cells is covered with a container 3 made of an airtight thin film.
The pressure is reduced to 0.001mmHg and it is sealed. Rigid 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 1, 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 gradually diffusing from the closed cell parts, and the thermal conductivity will decrease. It's getting bigger. For example, in a heat insulating structure 1 having a core material of 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 300 μm, 98
% open cell ratio, even if the pressure is reduced to 0.001 mmHg, the theoretical amount of water contained in 2% closed cell portion is
36cm ³ of gas (1800cm ³ ×0.02) diffuses into the open cell portion, which is gradually being depressurized, while being affected by the diffusion resistance of the cell membrane. Further, according to experiments, it took about 30 days at room temperature to completely reach pressure equilibrium, and 1 to 3 days in an atmosphere of 80 to 100°C, which is close to the heat resistance temperature of the rigid urethane foam 2. In the long run, the approximately 36 ^cm3 of gas mentioned above will increase the internal pressure.
It is conceivable to increase the thermal conductivity from 0.001 mmHg to 15 mmHg and deteriorate the thermal conductivity to 0.020 kcal/mh℃ or more. To prevent this, it would be necessary to maintain the heat insulating structure 1 at a temperature of at least 80 to 100°C and to 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. In addition, large-scale equipment is required for high-temperature and high-humidity processing, which also makes mass production difficult.
That's a problem. In view of the above problems, the present invention significantly improves productivity by reducing the pressure to a predetermined pressure in a short time, and maintains the insulation performance of the heat insulator over a long period of time, ensuring quality reliability. The purpose is to Means for Solving the Problems In order to solve the above problems, the present invention provides organic polyisocyanate, polyol, catalyst, blowing agent, and cell communication agent in the form of a powder of 0.1 to 5.0 parts by weight per 100 parts by weight of polyol. The core material of the heat insulator is a hard urethane foam made from a divalent metal salt of a saturated monocarboxylic acid. Effect With the above structure, the cell membrane ruptures during the foaming process and the core material, which has an open cell ratio of 100%, is covered with a container made of metal-plastic laminate film, and the interior is depressurized, allowing for short-time evacuation. This allows the internal pressure of the heat insulator to be uniformly reduced to a predetermined pressure. Furthermore, since there are no closed cell portions, there is no increase in internal pressure over a long period of time, and the initial heat insulation performance is maintained. In addition, examples of powdered divalent metal salts of saturated monocarboxylic acids that can be used in the present invention include calcium stearate, magnesium stearate, strontium stearate, and calcium myristate. EXAMPLE Hereinafter, an example of the present invention will be explained with reference to FIGS. 1 and 2. In the figure, 4 is a urethane foam foamed and cured using a high-pressure urethane foaming machine using the raw materials and blended parts shown in the table below. It is made of hard urethane foam, aged at room temperature, and then cut into a predetermined size.

【table】

[Table] In the table, polyol A is 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. In addition, polyol B includes sucrose, ethylenediamine,
This is a polyether polyol with a hydroxyl value of 400 mgKOH/g obtained by addition polymerizing PO using diethylene glycol as an initiator. In addition, polyol C
is a mixed polyether polyol containing polyol A and polyol B in a ratio of 70:30. and,
The foam stabilizer is silicone surfactant F-318 manufactured by Shin-Etsu Chemical Co., Ltd., and the foaming agent is Freon R-11 manufactured by Showa Denko Co., Ltd.
It is. Catalyst A is dimethylethanolamine,
Catalyst B is dibutyltin dilaurate. In addition, the cell communication agent is calcium stearate manufactured by NOF Corporation. Organic polyisocyanate A
is a polyisocyanate with an amine equivalent of 150 obtained by reacting toluylene diisocyanate with trimethylpropane and diethylene glycol, and organic polyisocyanate B is a crude diphenylmethane diisocyanate with an amine equivalent of 136 manufactured by Nippon Polyurethane Co., Ltd. Foaming was performed using various combinations of these raw materials.
4. Nos. A and B are shown in the table as comparative examples. The density and open cell ratio of these hard urethane foams 4 are also shown in the table. Thereafter, the adsorbed moisture is evaporated by heating at 120°C for about 2 hours, and the interior is covered with a bag-shaped container 5 made of a metal-plastic laminate film with a laminate structure of an aluminum vapor-deposited polyester film and a polyethylene film. The pressure was reduced to mmHg, and the heat insulator 6 was obtained by sealing. 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 K made by Shinku Riko Co., Ltd.
Measured with Matic at an average temperature of 24℃. As is clear from the table, as a polyol, an organic isocyanate, a catalyst, a foam stabilizer, a blowing agent, and a cell communication agent, 0.1 to 5.0 of a powdered divalent metal salt of a saturated monocarboxylic acid is added to 100 parts by weight of the polyol. Hard urethane foam foamed using weight parts 4
It was found that the open cell ratio was 100%. This is a powdery divalent metal salt of a saturated monocarboxylic acid.
It is thought that when the hard urethane foam 4 is foamed, it is dispersed on the cell film, making the film thickness non-uniform and causing the bubbles to break, but the details of this process have not yet been elucidated. Then, this hard urethane foam 4 with an open cell ratio of 100% and no closed cell portion is made into a heat insulating material 6.
Since it is used as a core material, the internal pressure of the heat insulating body 6 can be uniformly reduced to a predetermined pressure through open cells by evacuation for a short time, resulting in excellent mass production efficiency. In addition, since there is no closed cell portion containing gas, even if the heat insulator 6 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 6 does not deteriorate over a long period of time, contributing to quality assurance. On the other hand, in No. A containing 0.05 parts by weight of the cell communication agent, the open cell ratio was less than 100%, and the thermal conductivity was
It has become extremely large. In addition, in No. B containing 6.0 parts by weight, the cell skeleton itself was not formed and the foam disappeared due to the large effect of the cell communication agent, making it inapplicable as the core material of the heat insulating body 1. Effects of the Invention As is clear from the above description, the present invention has the following advantages:
The following effects can be obtained. a. Mixing 0.1 to 5.0 parts by weight of a powdered divalent metal salt of a saturated monocarboxylic acid to 100 parts by weight of the polyol as an organic polyisocyanate, a polyol, a catalyst, a foam stabilizer, a blowing agent, and a cell communication agent; The rigid urethane foam obtained by foaming has a cell structure with a 100% open cell ratio and no closed cells, so when it is covered with a container made of metal-plastic laminate film and the inside is depressurized, the internal pressure is reduced. It is possible to uniformly reach a predetermined pressure in a short time, and it is possible to ensure productivity during mass production. b. Since there is no closed cell part containing gas, even if the heat insulator is left for a long period of time, there will be no gas diffusion from the closed cell part and no pressure increase will occur. Therefore, the heat insulating performance of the heat insulator does not deteriorate, and quality stability is ensured.

[Brief explanation of drawings]

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, 5...Container, 6
...Insulator.

Claims (1)

[Claims] 1. 0.1 to 5.0 parts by weight of a powdered divalent metal salt of a saturated monocarboxylic acid is mixed with 100 parts by weight of polyol as an organic polyisocyanate, a polyol, a catalyst, a foam stabilizer, a blowing agent, and a cell communication agent, A heat insulator that is foamed to form a rigid urethane foam with an open cell structure, covered with a container made of metal-plastic laminate film, and sealed by reducing the pressure inside.