JPS6026002B2 - Manufacturing method of refrigerator box - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a refrigerator box body in which a urethane foam stock solution is injected and foamed to be used as a heat insulating material and a structural material.

In recent years, efforts have been made to reduce the specific gravity of urethane foam with the aim of saving resources.

In order to lower the specific gravity and maintain and improve the strength of the refrigerator box, so-called integral foam refrigerators are becoming more common, in which the outer box and the inner box are integrated by injection foaming with a urethane foam stock solution. In the conventional structure, a thin film such as a polyethylene film (POIJ) ethylene film was interposed on the heat insulating side of the inner box to prevent direct contact between the urethane foam and the inner box.

R-11, a blowing agent contained in urethane foam
Since this would corrode the inner box used in conventional structures, it was protected with polyethylene film, etc.

In the case of integral foam refrigerators, the inner box material is changed to ABS to reduce corrosion and prevent practical problems. However, depending on the usage conditions of the refrigerator, the shape of the inner box, the properties of urethane, etc., the stress (strain) acting on the ABS inner box through the urethane foam varies, and the allowable stress (critical strain)
If the temperature exceeds that level, fine cracks (whitening) will occur in the ABS inner box. The present invention has been made to eliminate this harm, and its main purpose is to apply a wax-like mold release agent that is easy to work with and is non-polluting to the main parts. The purpose is to increase the critical strain acting on the inner box and prevent minute cracks. Hereinafter, a first embodiment of the present invention will be described.
This will be explained in detail with reference to FIGS.

First, as shown in the figure, 1 is a refrigerator box body, and wax was applied to the urethane foam contact surface 2a of the inner box 2 as shown in parts A and B, which will be described later.

That is, the inner box front flat part (A part), the rear corner part (B
2) was applied separately to the handle side and hinge side. Using these inner boxes 2, outer boxes 4 were assembled and urethane injection was performed. Injecting urethane into the refrigerator box 1 is usually performed using a generally well-known injection method. After the injection is completed, the refrigerator box 1 is left at room temperature for one day and night, and then the refrigerator box 1 is left in an atmosphere of -30°C, and the inner box 2 is injected into the refrigerator box 1. Table 1 shows the relationship between critical strain and whitening.
It was shown to. In addition, the strain gauges for determining the critical strain were attached near the center of each section A and B from the inner side of the inner box 2, and the number of whitened pieces was determined by visual measurement. Further, although the coating thickness of Wax 3 was 50 to 100 μm in all cases, it is sufficiently effective even if it is less than that. Table 1 It has been found that when the wax 3 having a mold release effect is used as described above, the critical strain of the inner box 2 becomes high and the number of whitenings becomes extremely small.

Next, the paraffin wax used in the present invention is 85% or less of normal paraffin, and the remainder is isoparaffin.
It is a naphthenic type, and the amount of normal-paraffin is particularly limited.

Ordinary paraffin wax is 95% or more normal-paraffin and has a low melting point. The paraffin wax used in the present invention falls into the category of high melting point waxes. In the present invention, the content of normal paraffin is effectively 85% or less, and a particularly preferable range is 80 to 85%. In addition to these types of waxes for use as template agents, there are microwaxes, synthetic paraffins, and low molecular weight polyethylenes, but all of them have inferior mold release properties to urethane. The results of these studies will be explained according to Example 1. In addition, regarding the critical strain amount and the number of whitening, the same forehead direction is shown for both the handle side and the hinge side, so here,
Only the handle side is shown. The urethane foam used in the present invention is a conventionally known foam, and the foam manufacturing technology does not require a technology that is particularly different from known methods.

<Urethane foam> Sucrose polyether (OH value 490) 100 parts dimethylaminoethano.

-ru 2 Ikarito triethylene diamine (33
% dipropylene glycol solution) 1.
$ parts silicone surfactant (SH-193) 20 parts trichloromo/furo.

Methane 4 Guo C-Blood 1
10th side or C-side 12th side Table 2 In Experimental Examples 2 to 6 and Examples 2 to 3, C-TDI was used as the isocyanate, and in Examples 4 to 5, C1M Town 1 was used.

From this result, paraffin waxes with a normal paraffin content of 85% or less and a melting point of 65°C or higher are effective.

This is because the exothermic temperature of the urethane foam injected into the refrigerator reaches 65 to 75 o'clock, so the wax melts within that range and recoats the inner box surface uniformly, which further improves the moldability. Moreover, it is characterized in that the effective content of normal paraffin does not harm the urethane foam. Next, regarding the coating method, conventional methods have problems in terms of production technology, such as shortening of drying time by coating or pollution caused by spraying. Conventional wax-based koji molding agents have mostly been water-removable and solvent-based, and these have been sprayed with air. The water-repellent type takes a long time to dry, and the solvent-based type involves hazardous materials, environmental issues, and environmental issues. Also, if you spray using an air conditioner, the surrounding conditions will become a closed system, which is extremely bad. The coating method used in the present invention uses melted solvent-free wax, and the drying time is drying at room temperature using sand for several hours.

Furthermore, spraying involves applying pressure (hydraulic pressure) to the melted wax without using air to create a turbulent flow state and spray uniformly. These systems can be achieved by slightly modifying the conventionally used hot-melt systems, the benefit of which is very little diffusion into the surroundings. When actually incorporating it into a production line, it is sufficient to mass-produce by placing the inner box for coating on the conveyor, using four spray guns, and synchronizing the photocell and discharge timer. . The drying time and pollution properties were investigated based on Example 1 below.

Table 3 According to the above example, in a refrigerator manufactured by injecting a urethane foam stock solution into the space between the outer box and the plastic inner box and foaming, the main part of the inner box contains normal paraffin of 85% or less, which has been melted by heating in advance. It has been revealed that the critical strain of the main part of the inner box can be increased by applying paraffin wax having a temperature of 65°C or higher.

Furthermore, this wax is effective for both TDI foam and M blood 1 foam and does not cause cell roughness. Therefore, there is no whitening or cracking of the essential parts of the inner box due to integral foaming of the refrigerator, and the reliability of the product is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the refrigerator, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is a perspective view illustrating a state in which the wax of the present invention is applied to the inner box. 1... Refrigerator box body, 2... Inner box, 2a
......Urethane foam contact surface, 3...
Wax, 4... Outer box, A... Front flat part of inner box, B... Rear corner part of inner box. Multi-1 diagram A 2-diagram matching diagram

Claims (1)

[Claims] 1. In a refrigerator box manufactured by injecting a urethane foam stock solution into the gap between an outer box and a plastic inner box and foaming, the main part of the inner box contains a paraffin-based material having a normal paraffin content of 85% or less and a melting point of 65°C or higher. A method for manufacturing a refrigerator box body, characterized in that wax is sprayed and applied using hydraulic pressure, and then urethane foam stock solution is injected and foamed.