JPS6361587B2 - - 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 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 insulator, 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. Hard urethane foam 2 is a commercially available general material,
The feature is that the bubble membrane is broken by vacuum degassing under high temperature and high humidity to obtain open cells. Problems to be solved by the invention However, in such a heat-insulating structure,
Organic gas may be generated from the resin of the hard urethane foam 2 over time, increasing the internal pressure and deteriorating the heat insulation performance. That is, the raw material composition of the hard urethane foam 2 contains components that do not react with isocyanate groups, and there are low molecular weight monomers that do not turn into a resin even after the reaction is completed as the hard urethane foam 2. It gradually evaporates, increasing the internal pressure. According to experiments, these evaporated components may not completely evaporate in the heat insulating structure 1 until it is left at room temperature for about 80 days. In other words, even if the initial insulation performance is excellent, organic gases will gradually be generated after long-term use, increasing the internal pressure and deteriorating the insulation performance, which is expected to cause serious quality problems. Ru. In view of the above-mentioned problems, it is an object of the present invention to prevent organic gas from being generated from the resin over time, to prevent internal pressure from increasing over a long period of time, and to maintain heat insulation performance. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides purified diphenylmethane diisocyanate, purified diphenylmethane diisocyanate modified product, and purified tolylene diisocyanate obtained by preliminary reaction of polyol. A urethane consisting of an organic isocyanate having an amine equivalent of 120 to 180, a polyol, a catalyst, a foam stabilizer, a blowing agent, and a cell interconnection agent obtained by using prepolymerized purified tolylene diisocyanate alone or in combination. The core material of the insulator is a hard urethane foam with an open cell structure obtained by mixing and foaming raw materials, and is covered with a container made of metal-plastic laminate film, which is then sealed by reducing the pressure inside.
Purified diphenylmethane isocyanate and purified tolylene diisocyanate as used in the present invention refer to isocyanates obtained by distillation purification and do not contain distillation residues. for example,
As the purified tolylene diisocyanate, commonly available commercially available Takenate R80 manufactured by Takeda Pharmaceutical Co., Ltd. can be used. Effects In the present invention, with the above structure, all the components of the urethane raw material react and become resin, so there is no unreacted low-molecular monomer in the hard urethane foam resin, which evaporates as an organic gas over time, increasing the internal pressure.
It does not deteriorate the insulation performance. Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the figure, 4 is a hard urethane foam foamed and cured using the raw materials shown in the table below, which was 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.
This is a polyether polyol with a hydroxyl value of 442 mgKOH/g obtained by addition polymerization. Polyol B
is a polyether polyol with a hydroxyl value of 450 mg/KOH/g using sucrose and diethylene glycol as an initiator. The foam stabilizer is silicone surfactant F-335 manufactured by Shin-Etsu Chemical Co., Ltd., the foaming agent is Freon R-11 manufactured by Showa Denko Co., Ltd., the catalyst is dimethylethanolamine, and the cell communication agent is Nippon Oil & Fats Co., Ltd. ) manufactured by Calcium Stearate. Organic polyisocyanate A is
Prepolymerized tolylene diisocyanate with an amine equivalent of 150 obtained by reacting purified tolylene diisocyanate (TDI-80) with trimethylolpropane and diethylene glycol. Organic polyisocyanate B is Takenate manufactured by Takeda Pharmaceutical Company Limited.
Purified diphenylmethane diisocyanate with R300F and amine equivalent weight of 125. Organic polyisocyanate C is Millionate RMTL manufactured by Nippon Polyurethane Co., Ltd., which is a partially carbodiimidized modified product of purified diphenylmethane diisocyanate having an amine equivalent of 143. Furthermore, organic polyisocyanate D
is a crude diphenylmethane diisocyanate manufactured by Nippon Polyurethane Co., Ltd. with an amine equivalent of 136, and organic polyisocyanate E is a crude tolylene diisocyanate prepolymer obtained by reacting crude tolylene diisocyanate with tritylrollpropane and diethylene glycol and has an amine equivalent of 136. is 125.
Foaming was performed using various combinations of these raw materials, and some of them were designated as Examples No. 1 to No. 6 and Comparative Example No. 1.
A to No.C are shown in the table. The density and open cell ratio of the obtained hard urethane foam 4 are also shown in the table. Thereafter, the adsorbed moisture was evaporated by heating at 120°C for about 2 hours, and the container 5 was covered with a metal-plastic laminate film made of a laminate of aluminum vapor-deposited polyester film and polyethylene film, and the internal pressure was reduced to 0.05 mmHg. , 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 80 days are also shown in the table. As is clear from the table, rigid urethane foam 4 uses purified diphenylmethane diisocyanate, purified modified diphenylmethane diisocyanate, and prepolymerized purified tolylene diisocyanate as organic polyisocyanates.
It was found that the heat insulating body 6 having the core material had a very small change in thermal conductivity over time, and there was no problem in actual use.
On the other hand, in the heat insulator 6 using crude isocyanate, significant deterioration in thermal conductivity was observed. This is because the crude isocyanate contains components with no reaction activity, and even after the reaction is completed as a hard urethane foam 4, it remains in the resin as a low molecular weight monomer, gradually evaporates in the heat insulator 6, and internalizes it. It is thought that the thermal conductivity deteriorates due to the increase in pressure, but
It is thought that this phenomenon does not occur because purified isocyanate is not contaminated with inactive components. Note that the detailed theory has not yet been elucidated. As described above, by using purified diphenylmethane diisocyanate, purified diphenylmethane diisocyanate modified product, and prepolymerized purified tolylene diisocyanate as organic polyisocyanates, and using the hard urethane foam 4 produced, heat insulation can be achieved. Changes in the thermal conductivity of the body 6 over time are extremely small, making it possible to greatly contribute to quality reliability. Effects of the Invention As is clear from the above description, the present invention provides the following effects. The rigid urethane foam with an open cell structure is produced using purified diphenylmethane diisocyanate, purified diphenylmethane diisocyanate, and prepolymerized purified tolylene diisocyanate as organic polyisocyanates. Since no components are contained, all raw materials are converted into resin, and no low molecular weight monomers remain. As a result, it does not evaporate as organic gas inside the insulation, and its thermal conductivity does not deteriorate due to internal pressure increases, maintaining excellent insulation performance over a long period of time, contributing to quality stability. .

[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 a 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 Purified diphenylmethane diisocyanate,
The amine equivalent of the purified diphenylmethane diisocyanate modified product and the prepolymerized purified tolylene diisocyanate obtained by preliminary reaction of purified tolylene diisocyanate and polyol is
A hard urethane foam with an open cell structure obtained by mixing and foaming 120 to 180 organic polyisocyanate, polyol, catalyst, foam stabilizer, blowing agent, and cell communication agent is placed in a container made of metal-plastic laminate film. An insulator that is covered with a heat shield and sealed by reducing the pressure inside.