JPH035972B2 - - Google Patents

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 a flat box-shaped door with one side open, and a foaming urethane resin is injected into the outer panel, and a moisture-proof sheet is placed so as to cover the open surface of the door. The foam is stored in a molding jig maintained at a predetermined temperature, allowed to foam, and aged for a predetermined period of time to form a urethane foam with a sheet attached to the surface. I am trying to attach the inner side panel 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. By doing this, the temperature of the urethane foam decreases and its internal pressure decreases quickly, so the time when demolding is possible, which is determined by the balance between the internal pressure of the urethane foam and the skeletal strength of the urethane foam that suppresses it, becomes earlier. This allows time to be shortened.

[Problems with background technology]

However, with the above method of cooling at a predetermined timing during the ripening period, when forming a urethane foam with a sheet attached to the outer surface, the adhesion strength between the sheet and the urethane foam deteriorates and local Since gaps are formed, there is a problem that not only the strength is lowered but also sufficient moisture proofing cannot be achieved. This is because the temperature of the urethane foam in contact with the sheet drops too much due to cooling, and the resin skeleton is not sufficiently generated.
This is thought to be because a weakened resin layer is formed at the interface with the sheet.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve productivity by reducing the time required for demolding from a molding jig as much as possible in a device that forms a urethane foam with a sheet attached to its outer surface. It is an object of the present invention to provide a method for producing a urethane foam that can ensure sufficient adhesion strength with the foam.

[Summary of the invention]

In the present invention, the urethane foam is temporarily cooled after the start of aging, and then the entire foam is heated from about 3/4 of the aging period until the end of aging, and the heating causes the interface with the sheet to It is characterized by producing a sufficiently strong resin skeleton in the urethane foam.

[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 insulation door of a refrigerator, which has a flat box-shaped door outer panel 2 with one side open and an open surface of the door outer panel 2. It consists of the attached door inner side plate 3. 4 is about 30mm to 40mm thick filled inside the door outer panel 2
mm urethane foam, and the outer surface of the open side of the door outer panel 2 is covered with a sheet of kraft paper, for example.
is attached. The kraft paper 5 is provided, for example, to prevent moisture from entering the urethane foam 4. Next, in FIGS. 2 and 3 showing the manufacturing process of this heat insulating door 1, 6 is a high-temperature forming jig that is divided into upper and lower halves, and this is comprised of a lower mold 7 that accommodates the door outer panel 2, and a lower mold 7 that accommodates the door outer panel 2. Board 2
an upper mold 8 disposed so as to open and close the open surface of the upper mold 8;
It consists of.

Now, in the above-mentioned configuration, filling the urethane foam 4 into the door outer panel 2 of the heat-insulating door 1 is performed as follows. First, the high-temperature forming jig 6 is heated at a temperature of, for example, 40°C to 50°C.
The upper mold 8 is opened, the door outer panel 2 is placed in the lower mold 7 with the open side facing upward, and a predetermined amount of urethane is poured into the door outer panel 2 from the nozzle 9 of the urethane injection device. Inject the urethane resin stock solution 10 of the foam (second
(see figure). 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 3). 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 since a large amount of reaction heat is generated during the curing reaction, the urethane foam 4 is at a high temperature. For this reason, the urethane foam 4 has increased fluidity and is filled up to the corners of the door outer panel 2, and the curing reaction is promoted to successively generate resin skeletons. Next, when, for example, about 1 minute and 30 seconds have passed 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, for example, from about 5°C to
Transfer to a low-temperature molding jig (not shown, but having the same structure as the high-temperature molding jig) maintained at a low temperature of 20°C. As a result, the door outer panel 2 and the urethane foam 4 inside are cooled, so that the heat of reaction is removed, the internal temperature rapidly decreases, and the internal pressure of the urethane foam 4 decreases accordingly. In addition, due to this cooling, the kraft paper 5 that is in direct contact with the upper mold 8
Since the urethane foam 4 is cooled particularly strongly, the temperature of the portion of the urethane foam 4 in contact with the kraft paper 5 particularly decreases. So, next time, for example, about 2 minutes 15 minutes after the start of ripening.
After seconds have elapsed, the upper mold 8 of the low-temperature molding jig is opened, 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 boundary between the urethane foam 4 and the kraft paper 5 is heated, thereby preventing the weakening of the resin skeleton where the curing reaction has been accelerated in this area, thereby increasing the adhesion between the kraft paper 5 and the urethane foam 4. can be secured sufficiently. Therefore, kraft paper 5
It is possible to reliably prevent moisture from partially peeling off from the surface of the urethane foam 4, creating a gap, and allowing moisture to enter into the urethane foam 4 through this gap. After that, about 3 minutes after the start of ripening, 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.

By the way, during the aging period of the urethane foam 4, that is, the period from injecting the urethane resin stock solution 10 into the door outer panel 2 until the door outer panel 2 can be taken out from the molding jig, the internal pressure of the urethane foam 4 This is determined by the balance between this and the skeletal strength of the urethane foam 4 that holds it down. That is,
The internal pressure of the urethane foam 4 generally increases rapidly after the start of aging and then gradually decreases, and the strength of the resin skeleton of the urethane foam 4 generally increases gradually as the aging begins. If the mold is removed at an early stage when the internal pressure of the 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, the temperature could be lowered, and the internal pressure could be lowered quickly. The aging time is about 3
This can be shortened to minutes. Incidentally, if such cooling is not applied, it will take about 7 minutes to demold. Furthermore, in this example, approximately 2
Since the urethane foam 4 was heated after 15 minutes (corresponding to 3/4 of the total aging period), the resin skeleton strength of the urethane foam 4 at the boundary with the kraft paper 5 was increased as described above. can be effectively increased to improve adhesion strength.

In addition, in this example, the case where the thickness dimension of the urethane foam 4 is about 30 mm to 40 mm and the aging period is about 3 minutes is illustrated, but the thickness dimension of the urethane foam is not limited to this. Therefore, the aging period is also set appropriately.

〔Effect of the invention〕

As described above, the present invention, in forming a urethane foam with a sheet attached to the outer surface, can shorten the time required for demolding from a molding jig as much as possible, improving productivity, and also It is possible to provide a method for producing a urethane foam that can ensure sufficient adhesion strength to the foam.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a cross-sectional view of a heat-insulated door of a refrigerator, Figs. 2 and 3 are cross-sectional views showing different stages of the manufacturing process, and Fig. 4 shows the temperature of the forming jig. It is a change diagram of. In the figure, 1 is a heat insulating door (urethane foam), 4 is urethane foam, 5 is kraft paper (sheet), 6
is a forming jig.

Claims (1)

[Scope of Claims] 1. A method for forming a urethane foam with a sheet attached to the outer surface of the urethane resin by foaming it and aging it, comprising: a step of attaching a sheet to the outer surface of the foamable urethane resin; and the step of attaching a sheet to the outer surface of the urethane resin; Production of a urethane foam characterized by sequentially performing a step of temporarily cooling the foam after the start of ripening, and a step of heating the entire foam from approximately 3/4 of the ripening period to the end of the ripening. Method.