JPH08136120A - Heat insulation box and fabrication thereof - Google Patents

Abstract

PURPOSE: To improve heat insulation in the vicinity of a wall surface of a container of a heat insulation box by providing a skinless expandable layer on an expanded structure expanded in the container by interposing paper or cloth on a part of a contact surface between an inner wall of the container and the expanded structure. CONSTITUTION: A heat insulation member 4 comprising an expanded structure expanded in a container 3 is filled therewith between a metal outer box 1 and a resin inner box 2 both constituting the container 3, and a skinless expandable layer 5 is provided in contact with an inner wall surface of the metal outer box 1. The skinless expandable layer 5 is formed by previously providing a cloth 6 on the inner wall surface of the metal outer box 1, and impregnating water and a highly volatile blowing agent or a polyol composition or polyisocyanate composition including the water and the highly volatile blowing agent in the skinless expandable layer, and further using a polyurethane reaction upon injection of a urethane stock material. Hereby, heat insulation in the vicinity of the wall surface of the container 3 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating box body filled with polyurethane foam which is mainly used in electric refrigerators and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, electric refrigerators have been composed of a heat insulating box having a structure in which a metal outer box and a resin inner box are filled with a heat insulating material such as polyurethane foam or expanded polystyrene. Polyurethane foam is used in many electric refrigerators because it can be produced by in-situ foaming. But,
In the polyurethane foam produced by in-situ foaming, the reaction temperature does not rise as much as in the inside of the heat insulating material at the contact surface of the heat insulating box with the container during the manufacturing process, and therefore the growth of bubbles is not sufficient. Therefore, the obtained polyurethane foam has a problem that the density of the contact surface with the container increases and the heat insulating property decreases. In order to raise the temperature of the wall surface of the container to increase the foaming efficiency and to improve the heat insulating property of the obtained polyurethane foam, it is necessary to heat a large container constituting the refrigerator, which requires a large number of steps and energy. Further, in consideration of disassembling work of an electric refrigerator, it is proposed to provide a heat-meltable resin layer or a water-soluble adhesive layer between the container and the heat insulating material (Japanese Patent Application Laid-Open No. Hei 5-
No. 196346), however, it is not a structure for enhancing the heat insulating property of the contact surface of the heat insulating material with the inner wall of the container.

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a new heat insulating box body having an improved heat insulating property in the vicinity of the wall surface of the container of the heat insulating box body. The present invention also aims to provide a method of manufacturing such an insulating box.

[0004]

The heat-insulating box body of the present invention comprises a container and a foam formed in the container by foaming, particularly polyurethane foam, the foam being at least one of the contact surfaces with the inner wall of the container. In the part, a skinless foam layer is provided through paper or cloth. Further, the method for producing a heat insulating box of the present invention comprises a step of forming a liquid-containing layer selected from the group consisting of water and a highly volatile foaming agent on at least a part of the inner wall surface of the container, and at least one of which is foamed. A step of injecting a mixture of a polyol composition containing an agent and a polyisocyanate composition into the container and reacting the polyol composition with the polyisocyanate composition to form a polyurethane foam is included.

Here, the liquid-containing layer is preferably made of paper or cloth impregnated with the liquid. In another aspect of the present invention, the liquid-containing layer comprises paper or cloth impregnated with a polyol composition or a polyisocyanate composition containing the liquid. Further, in another aspect, the liquid-containing layer is the liquid layer formed by spraying or coating.

[0006]

In the heat insulation box of the present invention, the polyurethane foam has the skinless foam layer on at least a part of the contact surface with the inner wall of the container as described above. When a resin such as polyurethane foam is foamed in the container, the temperature of the wall surface of the container generally decreases, so that a non-foaming layer called a skin layer or a low foaming layer is easily formed on the contact surface of the foam with the container wall surface.
The present invention is configured to have a skinless foam layer instead of this skin layer. As a result, a heat-insulating box having excellent heat-insulating properties can be obtained without causing a large temperature drop on the wall surface of the container where a large temperature gradient is likely to occur.

In order to form this skinless foam layer,
The present invention utilizes the following two mechanisms. First, a water layer is formed on the inner wall surface of the container prior to foam molding. In this case, the water reacts with the polyisocyanate injected into the container to generate carbon dioxide and form a urea bond to form a skinless foam layer. Secondly, a highly volatile foaming agent layer is formed on the inner wall surface of the container. In this case, the blowing agent is
It is vaporized by the heat of reaction between the polyol composition and the polyisocyanate composition injected into the container to form a skinless foam layer. The highly volatile foaming agent refers to an organic liquid having a lower boiling point than the foaming agent in the bulk of polyurethane foam that is added to a polyol composition or a polyisocyanate composition to react and foam.

In order to form such a skinless foam layer easily and quickly, it is necessary that the above-mentioned water and / or highly volatile foaming agent is retained on the inner wall surface in a form that facilitates reaction and vaporization. is necessary. By impregnating paper or cloth with water and / or a highly volatile foaming agent, the surface area can be increased and this is a suitable constitution. However, the effect of the present invention can be obtained only by spraying or coating water, a highly volatile foaming agent, a polyol composition or a polyisocyanate composition containing these on the inner wall surface of the container. Further, when the container is heated, the reaction rate on the inner wall surface of the container is increased and a skinless foam layer is obtained, but heating a large container requires a large number of steps and energy in the manufacturing process. According to the present invention, even if the container is not heated, a skin layer is not formed, and a heat-insulating box body having a high heat-insulating property can be obtained. Therefore, the heat insulating property of the polyurethane foam is greatly improved particularly in the contact portion with the inner wall of the container having a large temperature difference.

A metal outer box is often used in an electric refrigerator or the like. Further, the metal outer box has a high thermal conductivity and a high temperature gradient in the vicinity of the wall portion. Therefore, according to the configuration of the present invention, a large heat insulating effect can be obtained. Further, the heat-insulating box of the present invention has many voids because it has a skinless foam layer on the inner wall portion of the outer-box container, and when the electric refrigerator is dismantled, this facilitates the separation of the outer box and the heat-insulating body, and dismantling There is also an advantage that it becomes easier.

As described above, the heat insulating box of the present invention has the skinless foam layer on at least a part of the contact surface with the inner wall of the container, so that the heat insulating property in the vicinity of the wall surface of the container can be improved. Further, according to the method of the present invention, a skinless foam layer can be easily formed on the contact surface with the wall surface of the container, and a heat insulating box having excellent heat insulating properties can be obtained. In particular, it is efficient to locally apply the configuration of the present invention to a low temperature part such as a freezing part that requires high heat insulation. Further, during the urethane reaction for forming the heat-insulating box, it is also excellent to use the present invention at a location where temperature rise is difficult to occur, foamability is low, and a skin layer is easily formed, that is, where heat conductivity is high and heat easily escapes. It is useful in constructing a heat insulating box.

[0011]

EXAMPLES Next, the present invention will be described in more detail by way of its examples. The heat insulating box of the present invention has a skinless foam layer on at least a part of the contact surface of the foam filled in the container with the container inner wall as described above, and is a heat insulating box used in an electric refrigerator. An example will be shown below as an example.
FIG. 1 shows an example of the wall surface of the heat insulating box of the present invention. Between the metal outer box 1 and the resin inner box 2 that form the container 3, a heat insulating material 4 made of a foam that is foam-molded in the container is filled.
A skinless foam layer 5 is provided in contact with the inner wall surface of the metal outer box 1. As shown in FIG. 2, the skinless foam layer is prepared by previously providing the cloth 6 on the inner wall surface of the metal outer box 1 and adding water and / or a highly volatile foaming agent, or a polyol composition or polyisocyanate containing them. The composition is impregnated and a skinless foam layer is formed by a polyurethane reaction when the urethane raw material is injected.

As the highly volatile foaming agent used here, an organic liquid having a low boiling point lower than the boiling point of the foaming agent in the urethane raw material is suitable, and specific examples thereof include hydrocarbons, fluorohydrocarbons and chlorofluorohydrocarbons. be able to.
The polyol composition and the polyisocyanate composition,
The material used for general polyurethane foaming is used. The addition of a foam stabilizer, a flame retardant, a filler, a foam nucleating agent, a reaction catalyst and the like is the same as in the case of producing a general urethane foam.

As the metal outer box 1 used in the present invention, a coated steel plate or a resin laminated steel plate such as a vinyl chloride steel plate is generally used. However, if a coated steel plate coated with paper or cloth in advance is used, the present invention can be easily carried out. Can be used for forming a skinless foam layer. As the resin inner box 2, various hard thermoplastic resins can be generally used. Among them, acrylonitrile / butadiene / styrene copolymer, acrylonitrile / styrene copolymer,
It is preferable to use polyolefin or the like. As a method of forming paper or cloth on the inner wall of the metal outer box, it can be easily formed by using glue or an adhesive. As this material, a general woven fabric, a non-woven fabric, or the like can be arbitrarily used, but a porous material having high water absorption and liquid absorption is suitable. In addition, it is preferable from the environmental point of view to select a material that causes less environmental damage even at the time of disassembly and disposal.

Example 1 A cotton cloth 6 was adhered to the inner wall surface of the freezer portion of the metallic outer box 1 as shown in FIG. 2 and impregnated with water to form a high water content layer. By mixing a polyol composition containing cyclopentane as a foaming agent and a polyisocyanate composition, injecting this mixture into a container composed of a metal outer box 1 and an ABS resin inner box 2, and foam-molding the mixture. A heat insulating box filled with polyurethane foam was obtained. This heat-insulating box has a skinless foam layer,
The heat insulating property was 11% higher than that of a conventional heat insulating box, that is, a heat insulating box obtained without providing a water-containing cotton cloth in the container. When the box body of this example is disassembled and the heat insulating material is observed, the impregnated water reacts with polyisocyanate in the high water content cotton cloth portion of the inner wall surface of the metal outer box, and carbon dioxide is formed by the formation of a urea bond. Micro bubbles due to foaming (about 140 micron diameter)
The skinless foam layer was formed on the inner wall contact surface of the metal outer box.

[Example 2] A non-woven fabric 6 was adhered to the inner wall surface of the freezer portion of the metal outer box 1 as shown in Fig. 2, and CFC R11 (boiling point 23.8 ° C) as a highly volatile foaming agent was contained therein. A highly volatile foaming agent-containing layer was spray-impregnated with the polyol composition of 1. A polyol composition containing cyclopentane (boiling point 49 ° C.) as a foaming agent and a polyisocyanate composition were mixed, and this mixture was poured into a container composed of a metal outer box 1 and an ABS resin inner box 2. Then, it was foamed and filled with polyurethane foam to obtain a heat insulating box. The heat insulation of this heat insulation box is 1 compared with the conventional heat insulation box.
It was 3% higher. When the heat insulating material was disassembled and observed, the polyol composition containing CFC R11 (boiling point 23.8 ° C.) reacts with polyisocyanate in the portion of the highly volatile foaming agent-containing layer on the inner wall surface of the metal outer box, Micro bubbles (about 160
A skinless foam layer (micron diameter) was formed on the inner wall contact surface of the metal outer box.

[0016]

As described above, the heat insulating box body of the present invention has the skinless foam layer on at least a part of the contact surface with the inner wall of the container, so that the heat insulating property in the vicinity of the wall surface of the container can be improved. . Further, according to the method of the present invention, a skinless foam layer can be easily formed on the contact surface with the wall surface of the container, and a heat insulating box having excellent heat insulating properties can be obtained. Further, the present invention is useful as a structure of a heat-insulating box body for recycling production that can be easily disassembled, and is capable of constructing a production system that is energy-saving and excellent in the global environment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a heat insulating box according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a main part of a heat insulating box according to another embodiment of the present invention.

[Explanation of symbols]

 1 Metal Outer Box 2 Resin Inner Box 3 Container 4 Heat Insulation Material (Foam) 5 Skinless Foam Layer 6 Cloth

Claims (5)

[Claims] 1. A container and a foam body foam-molded in the container, wherein the foam body has a skinless foam layer on at least a part of a contact surface with an inner wall of the container via a paper or a cloth. Insulation box body characterized by 2. A step of forming a liquid containing layer selected from the group consisting of water and a highly volatile blowing agent on at least a part of the inner wall surface of the container, and a polyol composition in which at least one contains a blowing agent. A method for producing a heat insulating box, comprising the step of injecting a mixture with a polyisocyanate composition into the container and reacting the polyol composition with the polyisocyanate composition to form a polyurethane foam. 3. The method for manufacturing a heat insulating box according to claim 2, wherein the liquid-containing layer is made of paper or cloth impregnated with the liquid. 4. The method according to claim 3, wherein the liquid-containing layer is made of paper or cloth impregnated with the polyol composition or polyisocyanate composition containing the liquid. 5. The method for manufacturing a heat insulating box according to claim 2, wherein the liquid-containing layer is a layer of the liquid formed by spraying or coating.