JP2702746B2 - Insulation - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulator used for a refrigerator, a freezing prefab, and the like.

FIG. 3 shows a conventional heat insulator. The configuration of the conventional example will be described below with reference to FIG.

In recent years, attention has been paid to using a heat insulator whose internal pressure is reduced in order to improve the heat insulating performance of the heat insulating box. As a core material of the heat insulator, powder such as pearlite, honeycomb, foam, or the like is used. For example, as disclosed in JP-A-57-133870, a proposal has been made to use a rigid urethane foam having open cells as a core material. JP-A-57-13
Referring to FIG. 3, reference numeral 1 denotes a heat insulating structure, in which a rigid urethane foam 2 having open cells is covered with a container 3 made of an airtight thin film, and the inside is made 0.00
Reduce the pressure to 1 mmHg and seal. The rigid urethane foam 2 is characterized in that a commercially available material having a closed cell ratio of about 80 to 90% is vacuum-degassed under high temperature and high humidity to break a cell membrane and obtain open cells.

Problems to be Solved by the Invention However, in such a heat-insulating structure 1, the foam film of the rigid urethane foam 2 may not break due to high resin strength even in a state of high temperature and high humidity. It is considered that the open cell rate cannot reach 100%. For this reason, even if the initial thermal conductivity is excellent, the internal pressure of the heat-insulating structure 1 gradually increases with time due to the gas, such as air, water vapor, and chlorofluorocarbon gas, which gradually diffuses from the closed cell portion, and the thermal conductivity increases. It is getting bigger. For example, 30
cm × 30cm × 2cm (volume 1800cm ³ ), average bubble diameter
In the heat-insulating structure 1 having a core material of a hard urethane foam 2 of about 300 μm, when the open cell ratio is 98%, the heat-insulating structure 1 has a thickness of 0.2%.
Even if the pressure is reduced to 001 mmHg, theoretically, about 36 cm ³ of gas (1800 cm ³ × 0.02) contained in 2% of closed-cell parts is reduced to open-cell parts that are gradually reduced in pressure while receiving the diffusion resistance of the bubble film. Spread. According to experiments, it was necessary to use rigid urethane foam 2 at room temperature for about 30 days to completely reach pressure equilibrium.
Even in an atmosphere at a temperature of 80 to 100 ° C. close to the heat-resistant temperature, aging was required for 1 to 3 days. In the long term, it is considered that the gas of about 36 cm ³ raises the internal pressure from 0.001 mmHg to 15 mmHg and deteriorates the thermal conductivity to 0.020 kcal / mh ° C. or more.

In order to prevent this, it will be necessary to maintain the rigid urethane foam 2 at least at 80 to 100 ° C. and continue to evacuate it with a vacuum pump for one day or more. That is, the gas remaining in the closed cell portion by this operation is exhausted through the bubble film,
Even if there are closed cells, the pressure can be reduced to a predetermined pressure. However, this operation can produce only one body per day for one exhaust facility in production, and mass production is very difficult. In addition, high-temperature and high-humidity processing also requires large-scale equipment, which also has a problem in mass production, and there has been a problem in improving productivity.

The present invention solves the above-mentioned problems, by significantly reducing the pressure to a predetermined pressure with a short-time exhaust, significantly improves the productivity, maintains the heat insulation performance of the heat insulator for a long time, and ensures the quality reliability. Aim.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a sealed container in which a silicone-based antifoaming agent is applied on the inner surface, and a saturated monocarboxylic acid divalent metal which is filled by integral foaming with the sealed container. It is made of a rigid urethane foam using a salt as a cell communicating agent, and the inside of the closed vessel is depressurized to obtain a heat insulator.

Effect The above structure breaks the cell membrane including the skin portion of the rigid urethane foam that comes into contact with the closed container during the foaming process, and the open cell ratio becomes 100%. Can be uniformly reduced to a predetermined pressure. In addition, since there is no closed cell portion, the internal pressure does not increase for a long period of time, and the initial heat insulating performance is maintained.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

In the figure, reference numeral 4 denotes an airtight container made of stainless steel, to which a silicone-based antifoaming agent SH-200 (not shown) manufactured by Toray Silicon Co., Ltd. is applied in advance on the inner surface. Reference numeral 5 denotes a rigid urethane foam having an open-cell structure, which is injected from an injection port 6 of a closed container 4 and is integrally foamed. The raw material and blending number of the rigid urethane foam 5 are shown in the table.

In the table, polyol A is a polyether polyol having a hydroxyl value of 442 mgKOH / g obtained by addition polymerization of propylene oxide (hereinafter, referred to as PO) using an aromatic diamine as an initiator. The foam stabilizer is silicone surfactant F-338 manufactured by Shin-Etsu Chemical Co., Ltd., and the foaming agent is Freon R-11 manufactured by Showa Denko KK. Catalyst A is dimethylethanolamine and catalyst B is dibutyltin dilaurate. In addition, the bubble communicating agent is calcium stearate manufactured by NOF Corporation. Organic polyisocyanate A
Is the amine equivalent obtained by reacting toluylene diisocyanate with trimethylpropane and diethylene glycol.
150 polyisocyanates These materials were combined and foamed, some of which are shown in the table as examples. The results obtained by measuring the density and open cell ratio of the rigid urethane foam 5 at the entire average including the skin layer and at the center at this time are shown in the same table.

Thereafter, the mixture was heated at 120 ° C. for about 2 hours to evaporate water and the like through the inlet 6, and then the valve 7 was attached. The pressure inside the container was reduced to 0.05 mmHg by a vacuum pump to obtain a heat insulator 8.
The evacuation time at this time was 10 minutes. The obtained heat insulator 8
The thermal conductivity of the initial value immediately after decompression and the thermal conductivity after 20 days are also shown in the table. The thermal conductivity was measured at an average temperature of 24 ° C. using K-Matic manufactured by Vacuum Riko Co., Ltd.

On the other hand, as a comparative example, the density and the open cell ratio of the rigid urethane foam 5 when the silicone-based defoaming agent is not applied to the inner surface of the closed container 4, the overall average value and the value at the center, and the heat of the heat insulator 6. The change in conductivity is also shown in the table.

As is clear from the table, a silicone-based antifoaming agent is applied to the inner surface of the closed container, and a rigid urethane foam having a saturated carboxylic acid divalent metal salt as a cell communicating agent is injected into the inside, and the foamed one is continuous. It was found that the air bubble ratio was 100% on the whole average including the skin layer.

This is because, when the rigid urethane foam 5 is foamed, the saturated monocarboxylic acid divalent metal salt is dispersed on the foamed film to make the film thickness non-uniform, break bubbles, and break the foam. It is considered that the applied silicone-based defoamer also exerts a foam breaking effect on the rigid urethane foam 5 in the foaming process even in the high-density portion, and increases the open cell ratio to 100%. Since the rigid urethane foam 5 having an open cell ratio of 100% and having no closed cell portion is used as a core material of the heat insulator 8, the internal pressure of the heat insulator 8 is uniformly reduced to a predetermined pressure through the open cells by short-time exhaustion. The pressure can be reduced and the mass production efficiency becomes excellent. Further, since there is no closed cell portion containing gas, even if the heat insulator 8 is left for a long period of time, there is no gas diffusion from the closed cell portion and no pressure rise occurs.
Therefore, the heat insulating performance of the heat insulator 8 does not deteriorate for a long time and contributes to quality assurance.

In addition, unlike the saturated monocarboxylic acid divalent metal salt, the open cell formation by the silicone-based antifoaming agent causes the bubbles to be coarse and the thermal conductivity to deteriorate, but is applied to the inner surface of the closed container 4. Is limited to the local portion of the skin layer portion and has a small adverse effect on the whole.

On the other hand, in the case of the comparative example in which the silicone-based antifoaming agent was not applied, the open cell ratio of the skin layer portion was low, and the thermal conductivity became significantly large after the elapse of time.

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

(A) A silicone-based antifoaming agent is applied to the inner surface of a closed container, and rigid urethane foam having a saturated monocarboxylic acid divalent metal salt as a cell communicating agent is injected into the closed container and integrally foamed. The obtained open-celled rigid urethane foam has an open cell ratio of 100 including the skin.
%, A closed cell structure without a closed cell portion is obtained. Therefore, when the inside of the sealed container is depressurized, the internal pressure can uniformly reach a predetermined pressure in a short time, and productivity during mass production can be secured. In particular, by applying a silicone-based antifoaming agent to the inner surface of the closed container, the foaming of the closed cell part can be promoted in the foaming process of the skin part, and the foam part of the skin part as well as the foam center is broken. A rigid urethane foam having an open cell ratio of 100% can be obtained.

(B) Since there is no closed cell portion containing gas, even if the heat insulator is left for a long period of time, there is no gas diffusion from the closed cell portion and no pressure rise occurs. Therefore, the heat insulation performance of the heat insulator is not deteriorated, and the stability of quality is ensured.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a heat insulator according to one embodiment of the present invention,
FIG. 2 is a cross-sectional view of the heat insulating body after filling with rigid urethane foam, and FIG. 3 is a cross-sectional view of a conventional heat insulating structure. 4 ... closed container, 5 ... hard urethane foam, 8 ...
Insulation.

Claims (1)

(57) [Claims] 1. A closed container in which a silicone-based antifoaming agent is applied to the inner surface thereof; A heat insulator formed by reducing the pressure inside the closed container.