JPS5922732A - Manufacture of urethane foam - Google Patents

Abstract

PURPOSE:To shorten the release time length from a molding jig and obtain the titled foam to ensure the adhesion strength between a sheet and the urethane foam by a method wherein the urethane foam is cooled for a predetermined period from the start of aging of urethane foam and heated after the elapse of a large portion of its aging period. CONSTITUTION:In case of obtaining the insulating door 1 of a refrigerator for example, the high temperature molding jig 6 is pre-heated at 40-50 deg.C and then the door outer panel 2 is taken in a bottom mold 7 with the open surface of the panel 2 facing upward so as to pour expandable urethane resin stock solution 10 in the door outer panel 2 from the nozzle 9 of an urethane pouring equipment and, immediately after pouring, kraft paper serving as a sheet is placed on the poured urethane resin stock solution 10 so as to cover it and then the open surface of the door outer panel 2 is closed by a top mold 8 in order to age the urethane resin. And then, after the aging starts, the door outer panel 2 is transferred to a low temperature molding jig. Further, after the elapse of three fourths of the total aging period (about two minutes fifteeen seconds), the panel 2 is returned to the high temperature molding jig 6 so as to be heated in order to develop sufficiently strong resin skeleton in the urethane foam at the boundary surface to the sheet and consequently to obtain the insulating door 1 composed of the objective urethane foam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a urethane foam, which forms a urethane foam having paper attached to its outer surface.

[Technical background of the invention]

For example, the insulated door of a refrigerator is made by injecting foaming urethane IIWII11 into the outer panel of the flat box-shaped door with the negative side open, and applying a moisture-proof sheet to cover the open surface of the door outer panel.
This is stored in a molding jig maintained at a predetermined temperature, allowed to foam and mature for a predetermined period of time, thereby forming a urethane foam with a sheet attached to the surface. The inside panel of the door is attached to the inside of the door. However, in recent years, in order to improve productivity and shorten the time required for demolding from the molding jig, it has been considered to cool the urethane foam at a predetermined time after the start of ripening. In this way, the temperature of the urethane foam is lowered and its internal pressure is lowered quickly, so the time when it is possible to release the mold, which is stagnant due to the balance between the internal pressure of the urethane foam and the skeletal strength of the urethane foam that suppresses it, is earlier. This results in a significant reduction in mold time.

[Problems with background technology]

However, in the above method of simply cooling after a predetermined period of the ripening period, when forming a urethane foam with a sheet attached to the outer surface, the adhesive strength between the sheet and the urethane 7 ohm deteriorates and local Since gaps are formed, the problem is that not only the strength is decreased but also sufficient moisture proofing cannot be achieved. This is because the temperature of the urethane foam in contact with the sheet decreases too much due to cooling, and the f# fat skeleton is not sufficiently generated, resulting in the formation of a weakened resin layer at the interface with the sheet. It is believed that there is.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve productivity by significantly shortening the time required for demolding from a molding jig in a product that forms a urethane foam with a sheet attached to its outer surface.
Moreover, it is an object of the present invention to provide a method for producing a urethane foam that can ensure sufficient adhesion strength between the sheet and the urethane foam.

[Summary of the invention]

In the present invention, the urethane foam is cooled at a predetermined time after the start of ripening, and then heated when approximately 3/4 of the ripening period has elapsed, thereby providing a sufficiently strong resin skeleton to the urethane foam at the interface with the heated sheet. The feature is that it is generated.

[Embodiments of the invention]

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

First, in Fig. 1, numeral 1 is the finally obtained urethane foam insulated door of a refrigerator, which is composed of a door outer panel 2 in the shape of a flat box with the negative side open, and an open surface of the door outer panel 2. It consists of a door inner side plate 5 attached to the door. 4 is a urethane foam with a thickness of approximately 30 to 40 mm that is filled inside the door outer panel 2.
A sheet such as kraft paper 5 is attached to the outer surface of the open side of outer &2. The kraft paper 5 is provided, for example, to prevent moisture from entering the urethane foam 4. Next, in FIGS. 2 and 6 showing the manufacturing process of this heat-insulating door 1, 6 is a high-temperature forming jig that is divided into upper and lower parts, and this is a lower mold 7 that accommodates the door outer panel 2, and a lower mold 7 that accommodates the door outer panel 2. The filling of the upper mold 8 resin foam 4, which is arranged to open and close the open surface of the outer panel 2, is as follows.

First, the high-temperature forming jig 6 is preheated to, for example, 40° C. to 50° C., the upper mold 8 is opened, and the door outer panel 2 is housed in the lower mold 7 with the open side facing upward. A predetermined foamable urethane resin stock solution 10 is injected into the door outer panel 2 from the nozzle 9 of the urethane injection device (see FIG. 2). After this, immediately put the kraft paper 5 into the door outer panel 2 from the open side and cover it with the urethane resin stock solution 10, and then align the upper mold 8 with the lower mold 7 to close the open surface of the door outer panel 2 and carry out the aging process. (See Figure 6). At the beginning of this aging process, the high temperature molding jig 6 is at a high temperature of approximately 40°C to 50°C, and a large amount of reaction heat is generated due to the curing reaction.
becomes high temperature. For this reason, the urethane foam 4 increases its fluidity and is filled up to the gaps within the door outer panel 2, and the curing reaction is promoted to successively generate resin skeletons. Next, after about 1 minute and 50 seconds have elapsed after the start of this aging, the upper mold 7 of the high-temperature forming jig 6 is opened, the door outer panel 2 is taken out from the lower mold 8, and the temperature is immediately heated to about 5°C to 2°C, for example.
Transfer to a low-temperature molding jig (not shown, but made of the same structure as the high-temperature molding jig) that was kept at a low temperature of 0°C for 4 (8 seconds).As a result, the door outer panel 2 and the inner urethane foam 4 is cooled, the heat of reaction is removed and the internal temperature rapidly decreases, and the internal pressure of the urethane foam 4 also decreases accordingly.In addition, due to this cooling, the kraft paper 5 in direct contact with the upper mold 8 Since the urethane foam 4 is also cooled particularly strongly, the temperature of the portion of the urethane foam 4 in contact with the kraft paper 5 particularly decreases.
After 5 seconds have elapsed, the upper mold 8 of the low-temperature molding jig is opened and the door outer panel 2 is taken out, and immediately returned to the high-temperature molding jig 6 to continue aging for about 45 seconds.

As a result, the urethane foam 449 has a craft forging 5
Since the boundary between the kraft paper 5 and
Adhesion strength between the urethane foam 4 and the urethane foam 4 can be ensured sufficiently. Therefore, Kula.

It is possible to reliably prevent IF from occurring when the soft paper 5 is partially peeled off from the surface of the urethane foam 4 to create a gap, and moisture from entering into the urethane foam 4 through this gap. After that, about 3 minutes after the start of aging, the upper mold 8 of the high-temperature forming jig 6 is opened, the door outer panel 2 filled with the urethane foam 4 and hardened is taken out, and the door inner panel 3 is attached to the door outer panel 2. After installation, the insulation door 1 is completed.

and ζro, the aging period of urethane foam 4, that is, the door outer panel 2
During the period from injecting the urethane fat stock solution 10 into the molding jig until force is applied to take out the door outer panel 2 from the molding jig, the internal pressure of the urethane foam 4 and the skeleton of the urethane foam 4 that presses this are maintained. It is determined by the balance with strength. That is, the internal pressure of the urethane foam 4 generally tends to increase rapidly after the start of ripening and then gradually decrease, and the strength of the resin skeleton of the urethane foam 4 generally increases gradually as the ripening starts. Therefore, if the mold is removed at an early stage when the internal pressure of the urethane foam 4 still exceeds the resin skeleton strength, the urethane foam 4 will continue to expand, causing distortion in the door outer panel 2. Therefore, demolding must be possible only after the resin skeleton strength exceeds the internal pressure. Regarding this point, in this example, the urethane foam 4 was cooled approximately 1 minute and 30 seconds after the start of ripening, so that the heat of reaction could be removed and the temperature could be lowered, thereby reducing the internal pressure quickly. This allows the aging time to be shortened to about 5 minutes. Incidentally, if such cooling is not applied, it will take about 7 minutes to demold. Furthermore, in this example,
Since the urethane foam 4 was heated approximately 2 minutes and 15 seconds after the start of aging (corresponding to 3/40 of the total aging period), the urethane foam 4 at the boundary with the kraft paper 5 was heated as described above. The adhesive strength can be improved by effectively increasing the resin skeleton strength.

In this example, the case where the thickness of the urethane foam 4 is about 50 to 40 mm and the aging period is about 3 minutes is exemplified, but the thickness of the urethane foam is not limited to this. Therefore, the aging period should be set appropriately.

〔Effect of the invention〕

As described above, the present invention is directed to a product that forms a urethane foam with a sheet attached to the outer surface, and is capable of reducing the time required for demolding from a molding jig to improve productivity. It is possible to provide a method for producing a urethane foam that can ensure sufficient adhesion strength between the foam and the urethane foam.

[Brief explanation of drawings]

The drawings show one implementation of the present invention; FIG. 1 is a cross-sectional view of a heat-insulating door of a refrigerator, FIGS. 2 and 3 are cross-sectional views showing different stages of the manufacturing process, and FIG. 4 is a temperature diagram of a forming jig. It is a change diagram of. In the figure, 1 is a heat insulating door (urethane foam), 4 is urethane 7
ohm, 5 is a kraft paper C sheet), and 6 is a forming jig. Figure 1 Figure 20

Claims (1)

[Claims] 1. In a product in which urethane foam is foamed and aged for a predetermined period to form a urethane foam with a sheet attached to the outer surface, the urethane foam is cooled at a predetermined time after the start of aging, and then aged for the predetermined period. Abbreviation of period 3/
4. A method for producing a urethane foam, characterized in that heating is performed after 4 lapses.